- Email: [email protected]
Short sleep duration, sleep disorders, and traffic accidents
IATSS Research 37 (2013) 1–7
Contents lists available at SciVerse ScienceDirect
IATSS Research
Short sleep duration, sleep disorders, and traffic accidents Yoko Komada, Shoichi Asaoka, Takashi Abe, Yuichi Inoue ⁎ Department of Somnology, Tokyo Medical University, Japan
a r t i c l e
i n f o
Article history: Received 26 March 2013 Received in revised form 3 June 2013 Accepted 4 June 2013 Keywords: Sleepiness Sleep apnea syndrome Narcolepsy Insufficient sleep Traffic accident Countermeasure
a b s t r a c t Sleepiness is an important factor in traffic accidents caused by human error. The purpose of this paper is to review a number of studies conducted over the years regarding the effect of the lack of sleep on the incidence of traffic accidents as well as the individual effects of various sleep disorders on accidents. In addition, we discuss recent advances in methods of detecting sleepiness and strategies for preventing traffic accident by using these methods. © 2013 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved.
Contents
1. 2. 3.
Introduction . . . . . . . . . . . . . . . . . . . . . . Lack of sleep and accidents . . . . . . . . . . . . . . . . Sleep disorders and accidents . . . . . . . . . . . . . . 3.1. Insomnia . . . . . . . . . . . . . . . . . . . . . 3.2. Sleep apnea syndrome . . . . . . . . . . . . . . 3.3. Narcolepsy . . . . . . . . . . . . . . . . . . . . 3.4. Behaviorally-induced insufficient sleep syndrome . . 3.5. Shift-work disorder . . . . . . . . . . . . . . . . 4. Sleepiness detection methods and accident countermeasures 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
1. Introduction In April 2012 a bus driver in Japan who fell asleep at the wheel caused a disastrous accident that took the lives of 7 people and injured ⁎ Corresponding author at: Department of Somnology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan. Tel.: +81 3 3342 6111; fax: +81 3 3342 7083. E-mail address: [email protected] (Y. Inoue). Peer review under responsibility of International Association of Traffic and Safety Sciences.
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
1 2 3 3 3 4 4 5 5 6 6
a further 39. The bus, on its way from Kanazawa to Tokyo, hit a roadside wall on the Kanetsu Expressway around dawn. No brake or skid marks were found at the site of the accident; the Gunma Prefectural Police reported that the driver had “fallen asleep.” Around the same time in Kameoka City, Kyoto, a mini-car ran into a group of children walking to school with their guardians, hitting 10 people, of whom 3 died and 7 were severely injured. This accident reportedly involved an unlicensed 18-year-old driver who fell asleep at the wheel. Generally, accidents caused by drowsiness and falling asleep are the result of drivers being unable to control the brakes or steering due to their impaired state. Furthermore, because such accidents often occur at high speeds, there is a much greater mortality rate or risk of serious injuries [1]. Sleepiness is an important factor in traffic accidents caused by human error. One study of 19,000 subjects across five European
0386-1112/$ – see front matter © 2013 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.iatssr.2013.06.001
Y. Komada et al. / IATSS Research 37 (2013) 1–7
countries [2], as well as another of 3000 Japanese adults [3], found that excessive daytime sleepiness (EDS) reached as much as 15%. The main causes of EDS are (1) the lack of sleep, (2) deterioration in the quality of sleep, (3) disruption of circadian rhythms, and (4) primary hypersomnia. In terms of lack of sleep, it has been suggested that lifestyles requiring activity around the clock or late at night are the main cause of this condition. In 1960, 90% of people reportedly went to sleep at 11:00 PM and slept for an average of more than 8 h, but the number of people active late at night has gradually risen, resulting in shorter sleeping times. In 2010, half of the population was still awake at 11:00 PM and the mean sleeping time was only 7 h and 14 min, suggesting a reduction of around 1 h of sleeping time compared with 40 years ago [4] (Fig. 1). In a study conducted on the general population (n = 12,000) in Finland, 20.4% of participants were found to have insufficient sleep [5], while a study of 4000 adult subjects in Japan revealed that 28% had fewer than 6 h of sleep each night [6]. Thus, there appears to be a high rate of insufficient sleep in developed countries. Of course, people with chronically short sleeping times often have EDS. However, although an accumulated lack of nocturnal sleep can result in serious deficits in neurobehavioral function, the increase in subjective sleepiness under such conditions remains mild. That is, people with chronic lack of adequate sleep may underestimate their own sleepiness [7]. Unwanted sleepiness may also occur due to the disruption of circadian rhythms in situations such as jet lag or shift work, as well as primary circadian rhythm sleep disorders such as delayed sleep phase. People whose quality of sleep deteriorates as a result of sleep disorders that cause frequent interruption of nocturnal sleep, such as obstructive sleep apnea syndrome and periodic limb movement disorder, can develop secondary hypersomnia. In addition, while primary hypersomnia such as narcolepsy and idiopathic hypersomnia is relatively rare, it can cause serious problems with EDS [8]. In this report, we survey a number of studies conducted over the years regarding the effect of the lack of sleep on the incidence of traffic accidents as well as the individual effects of various sleep disorders on accidents. In addition, we discuss recent advances in methods of detecting sleepiness and strategies for preventing traffic accident by using these methods.
2. Lack of sleep and accidents In a previous study, we sought to identify a correlation between the occurrence of traffic accidents due to falling asleep at the wheel and sleep duration on the day before the accident. We analyzed 1772 of the 4871 traffic accidents that occurred in Tsukuba City from August 1993 to December 2003, excluding those caused by drunk driving [9]. First, accidents were categorized by type as rear-end collisions (n = 240), single-car accidents (n = 293), or other accidents (n = 1239). A rear-end collision was defined as a trailing car crashing into the rear of a leading vehicle. A single-car accident was defined as a car crashing against a structure on a road or shoulder such as a parked vehicle, wall, house, or telegraph pole. Accidents involving interaction with other vehicles or persons were classified as other accidents. Our analysis of the time of day that each accident occurred revealed that rear-end collisions most frequently occurred between 8:00 and 9:00 AM. On the other hand, single-car accidents occurred more frequently during the night than during the day (Fig. 2). These findings suggest that the time zone of accident occurrence differs by the type of accident. The risk of rearend collisions grows with increased traffic density, especially during the morning rush hour, which may lead to less space between cars. In contrast, it was hypothesized that single-car accidents could be attributed to low nighttime traffic density that reduced driver alertness and increased driving speed. For both rear-end collisions and single-car accidents, a higher percentage of subjects were found to have had less than 6 h of sleep on the day before the accident than for other accidents (11.3% in rearend collisions, 10.2% in single-car accidents, 4.8% in other accidents). Multivariate logistic regression analysis showed that the occurrence of
a Number of accidents
2
300 250 200 150 100 50 12:00
14:00
16:00
18:00
20:00
22:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
6:00 6:00
8:00
4:00 4:00
10:00
2:00 2:00
8:00
0:00 0:00
0
Proportion of each accident in each time zone (%)
b 100 80 60 40 20 0
Time of day Fig. 1. Changes in Japanese sleep duration and percentage of people staying awake past 11:00 PM. This figure shows the percentage of Japanese people who stay awake past 11:00 PM on weekdays and the average subjective total sleep time from 1960 to 2010. In 1960, 90% of the population were already asleep at 11:00 PM and typically slept for over 8 h. However, sleeping times gradually fell over the surveyed period. In 2010, half of the population remained awake past 11:00 PM with an average sleeping time of 7 h and 14 min. Created by the NHK National Time Life Survey.
Accidents of other types Single-car accidents Rear-end collisions Fig. 2. (a) Time of day distribution of all accidents, and (b) proportion of rear-end collisions, single-car accidents and other accidents among all accidents in each time zone. Abe et al., Journal of Sleep Research. 2010.
Y. Komada et al. / IATSS Research 37 (2013) 1–7
rear-end collisions was significantly associated with sleep duration of less than 6 h and more frequent driving, while the occurrence of single-car accidents was significantly associated with younger age (≤25 years old), sleep duration of less than 6 h, the increment between spells of driving, and nighttime (21:00–06:00) driving. In another study, we administered a questionnaire in October 2008 to approximately 4000 non-professional drivers and investigated factors associated with motor vehicle accidents (MVAs). The results obtained were as follows: self-reported sleep duration on weekdays of less than 6 h (OR = 8.02, 95% confidence interval [CI]: 1.08–59.60, p b .05), more than 6 h and less than 7 h (OR = 6.28, 95% CI: 0.83– 47.43, p = .07), and loud snoring or apnea (OR = 2.07, 95% CI: 1.12– 3.82, p b .05) were all associated with an increased risk of MVAs [10]. This result suggests that in order to prevent MVAs caused by falling asleep, drivers should have adequate sleep and undergo screening for sleep apnea syndrome. 3. Sleep disorders and accidents The International Classification of Sleep Disorders [8], includes the following classifications for sleep disorders: insomnia, sleep-related breathing disorders, hypersomnias of central origin, circadian rhythm sleep disorders, parasomnias, sleep-related movement disorders, isolated symptoms, and other sleep disorders. Among them, drivers with sleep disorders that can cause severe EDS such as sleep apnea syndrome or hypersomnias of central origin are reported to have 1.5–4 times greater risk of traffic accidents than drivers without any sleep disorder [11,12]. Undoubtedly, diagnosis and treatment of these sleep disorders are important to reduce traffic accidents caused by falling asleep at the wheel. Here, we focus on several sleep disorders, all of which are associated with an increased risk of traffic accidents. In addition to introducing accident conditions for each disorder, which have been published previously, we discuss issues that should be clarified to keep traffic safe from driving problems caused by the disorders. 3.1. Insomnia Insomnia is known to be common [13–15], affecting approximately 10% to 15% of the general population [2,16]. In addition, the rate of occasional sleep medication use in the general population is approximately 3% to 11% [17–19]. In people with insomnia symptoms, the rate is approximately 26% [20]. Nocturnal insomnia is frequently associated with daytime sleepiness and fatigue [21,22], psychomotor deficits [23,24] and cognitive impairments [25], but no study has yet revealed a direct correlation between insomnia and an increased risk of traffic accidents. The residual effects of hypnotics the next morning, however, may lead to substantial impairment in psychomotor functioning, possibly increasing the risk of motor vehicle accidents, although various prescription hypnotics may be equally effective in promoting sleep [26]. A study on the effects of after-midnight intake of zolpidem and temazepam on the driving ability of 18 insomniac women using a driving simulator revealed that 5.5 h after administration there were no major differences in psychomotor performance in women who had taken these two hypnotics compared with those who had taken a placebo, indicating an absence of significant residual effects early the next morning [27]. However, certain subjects were more susceptible than others to the drugs' effects. This underlines the necessity to strongly advocate against taking hypnotics late at night if patients intend to drive a car early the next morning. 3.2. Sleep apnea syndrome Sleep apnea syndrome (SAS), with its repeated episodes of nocturnal hypoxemia and sleep fragmentation, increases sleepiness, which in turn increases inattention while driving [28]. Following the initial report by George et al. in 1987 [29], the risk of accident in SAS patients due to
3
falling asleep at the wheel has been studied by numerous researchers [28,30]. The results of a meta-analysis study by Sassani et al. [31] showed that the odds ratio of traffic accidents increased in people with SAS by 2.52 (95% CI: 1.84–3.45). Our systematic investigation of MVA risk among Japanese drivers with obstructive sleep apnea syndrome (OSAS) revealed that the odds ratios for MVAs and dozing off at the wheel in the OSAS group compared with the general population were 2.4 (95% CI: 1.6–3.4) and 13.2 (95% CI: 10.0–17.4), respectively [32]. Multivariate logistic regression analysis revealed that MVAs were significantly associated with either high scores on the Epworth Sleepiness Scale (ESS ≥ 11) or frequent respiratory disorder events (apnea Hypopnea Index: AHI ≥ 40/h). Further studies have found that long-term continuous positive airway pressure (CPAP) treatment was clearly effective in reducing the number of MVAs [32,33]. In our study indicated above, the proportion of subjects who experienced MVAs was significantly higher in the OSAS group at baseline compared with the control group and OSAS group at the follow-up period (OSAS group at the baseline: 16.8%; control group: 4.7%; OSAS group at follow-up period: 3.1%; p b 0.01). Furthermore, there was no significant difference in the rate between the control group and the CPAP-treated OSAS group at follow-up. Results from a study using driving simulators also demonstrated a significant improvement in subjective sleepiness and driving performance in CPAP-treated OSAS patients [34]. Interestingly, in our study AHI scores were significantly higher in those who had multiple MVAs than in those who had only a single MVA, despite the ESS scores of the former group being significantly lower (Fig. 3). This finding supports the hypothesis that self-reported measures tend to underestimate the severity of sleepiness in severe OSAS patients [35]. In addition, in a systematic review examining MVA rates in OSAS patients, ESS scores did not appear to be predictive of crashes in 8 of the 15 studies examined [36]. Mulgrew et al. [37] also reported no significant relationship between subjective sleepiness and MVA rate, and suggested that patients who are less aware of their impaired vigilance may be at much higher risk. Thus, we should consider that MVAs might occur when subjective measures of sleepiness are lower than expected from the AHI, especially in patients severely affected by OSAS. Therefore, early detection and treatment of severe OSAS should be promoted to prevent multiple MVAs, regardless of whether there is subjective sleepiness. In order to elucidate the current rate of falling asleep at the wheel among driver's license holders and to understand the correlation between falling asleep at the wheel and SAS, approximately 5000 driver's license holders who went for renewal were asked to answer an anonymous and voluntary questionnaire in September 2006 (respondents: 3235; response rate: 61.8%). As mentioned above, the percentage of people with EDS is about 15% of the general population [2,3]. The results of this study, however, revealed that around 40.4% of the 3235 respondents had experienced sleepiness while driving [19]. Thus, sleepiness can easily occur among ordinary drivers in daily life while driving a vehicle. Furthermore, 20.3% of driver's license holders reported having fallen asleep at the wheel while 10.4% had experienced near-miss accidents or actually had accidents due to falling asleep at the wheel [19]. Other studies from Western countries revealed that 29% of subjects had experienced almost falling asleep at the wheel [38] while 18.3% had experienced near misses due to falling asleep at the wheel [39]. In addition, 1.3% had experienced an actual accident [39]. Other studies have reported the percentage of accidents that occur in relation to sleepiness to be around 20% [1,40]. Looking at these studies, the occurrence of accidents in Japanese drivers is at least the same as or a little bit higher than for drivers in Western countries, and there is a clear association between sleepiness and traffic accidents. Factors related to falling asleep at the wheel are being male, having a driver's license for a long period, longer weekly driving distance, appearance of sleepiness even after a short driving time, and selfawareness of having SAS or has been diagnosed with SAS [19]. An
4
Y. Komada et al. / IATSS Research 37 (2013) 1–7
p<0.01 160
p<0.01
p<0.05
25
p<0.05
20
ESS score
AHI
120
80
15
10
40 5
0
0 =0
=1
2
=0
=1
2
Number of car accidents within past 5 years Fig. 3. Comparison of AHI (left panel) and ESS score (right panel) between groups categorized by number of MVAs (Komada et al., Tohoku Journal of Experimental Medicine. 2009). Group without MVA: n = 496, Group with one MVA: n = 56, Group with two or more MVAs: n = 18. AHI: F2,567 = 7.2, p b 0.001; ESS: F2,567 = 15.9, p b 0.0001. AHI: Apnea hypopnea index; ESS: Epworth sleepiness scale.
analysis conducted on driver's license holders who had SAS revealed that 7.5% responded that they “might suffer from SAS,” whereas 1.1% responded that they “were diagnosed with SAS.” However, that this study was of driver's license holders who had come to the driver's license examination center for license renewal may have introduced a sampling bias. Despite this, because the percentage of drivers who had been diagnosed with SAS among those who thought that they might have SAS remained low, it may be important to promote early diagnosis and treatment of SAS in order to prevent as-yet-undiagnosed drivers from falling asleep at the wheel. Furthermore, it is also important to disseminate information about the relationship between exhaustion due to driving for long periods, falling asleep at the wheel, and accidents resulting from falling asleep. 3.3. Narcolepsy Narcolepsy is a sleep disorder closely related to EDS. Usually, a normal person does not fall asleep during driving or while having a conversation, but people suffering from narcolepsy have such tendencies. In addition, cataplexy triggered with certain kinds of emotions may also occur. That is, bodily muscle tone is completely lost when a strong emotional reaction occurs. In general, sleepiness in narcolepsy patients is reportedly stronger than in SAS patients. For this reason, the deterioration of driving performance in patients with narcolepsy has been systematically studied using a simulator [41,42]. According to Aldrich, the motor vehicular accident rate due to sleepiness in the general population is around 5%; however, that rate increases up to 50% in narcoleptic patients [11]. Another previous study found that 75% of narcolepsy patients with cataplexy and 50% of those without cataplexy had experienced traffic accidents or near misses in the last five years [43]. The results of a logistic regression analysis showed that ESS scores were significantly associated with increased automobile accidents and near misses (severe; OR = 14.6, 95% CI: 2.0–108.7) [43]. 3.4. Behaviorally-induced insufficient sleep syndrome In the 2nd edition of the ICSD, behaviorally induced insufficient sleep syndrome (BIISS) is classified as a category of “hypersomnia of central origin which is not due to a circadian rhythm sleep disorder, sleep-related breathing disorder, or other cause of disturbed nocturnal sleep” [8]. Unlike narcolepsy, which occurs based on decreased
orexinergic control of wakefulness, patients with BIISS are unable to maintain normal alertness and wakefulness due to a chronic lack of sleep. In reports from other countries, 2% of patients who visited a sleep disorder center with any sleep complaint and 6% of those with EDS were diagnosed to have BIISS [44]. Our previous study showed that among the 1243 patients who visited our clinic due to EDS, the percentage of patients diagnosed with BIISS was 7.1% [45]. This rate was higher than those for circadian rhythm sleep disorders and periodic limb movement disorders, despite being lower than the rate for major hypersomnias such as sleep apnea syndrome, idiopathic hypersomnia, and narcolepsy (Table 1). Considering this, cases with EDS caused by chronic insufficient sleep should not be ignored clinically. Furthermore, the rate of the population with chronic EDS in epidemiological surveys is markedly higher than the rate of patients with BIISS who consult medical institutes. That is, most people with BIISS are thought unlikely to seek medical assistance. We believe that it is necessary to raise awareness of the significance of chronic sleep insufficiency in the general population. Symptoms of BIISS include fatigue, irritation, depression, muscle pain, concentration disturbance, and a decline in cognitive function as well as daytime vigilance [46,47]. Another study confirmed that Table 1 Diagnoses of 1243 patients with excessive daytime sleepiness. Komada et al., Sleep Medicine. 2008. Diagnosis
n
%
Obstructive sleep apnea syndrome Idiopathic hypersomnia Narcolepsy Behaviorally induced insufficient sleep syndrome Circadian rhythm sleep disorders Sleep disorders associated with mental disorders Periodic limb movement disorder or restless legs syndrome Insomnia Parasomnias Long sleeper Recurrent hypersomnia More than two diseases causative for daytime sleepiness (Of which ISS + other hypersomnia) Undiagnosed
431 136 109 88 76 54 33 30 14 12 3 69 25 188
34.7 10.9 8.8 7.1 6.1 4.3 2.7 2.4 1.1 1.0 0.2 5.6 2.0 15.1
Undiagnosed: Patients who did not have a confirmed diagnosis due to interruption of diagnostic examination or treatment, or patients in whom two clinicians did not completely agree on the final diagnosis.
Y. Komada et al. / IATSS Research 37 (2013) 1–7
the performance of tasks that require both concentration and vigilance was reduced in populations with BIISS [48]. In our study, the ESS score of people with BIISS at an initial assessment was 13.6 (SD = 3.4), which was significantly lower than that of narcolepsy patients, significantly higher than that of people with SAS and circadian rhythm sleep disorders, and on the same level as those with idiopathic hypersomnia (Table 2). Furthermore, among people with BIISS, 22.1% had experienced driving or work-related accidents or near misses. Considering that the traffic accident rate due to falling asleep remains below 3% in the general population [49], the accident rate of people with BIISS may be much higher. Compared with the group who had no such experiences, the ESS scores of the group that had experienced accidents or near misses was significantly higher (group with accident experience: 15.5 (SD = 3.8) points, group without accident experience: 13.0 (SD = 3.1) points; p b .01). 3.5. Shift-work disorder The period length of circadian rhythm in humans, including sleep– wake pattern, melatonin hormone secretory pattern, and body temperature, exceeds 24 h without light–dark changes and time information, both of which are crucial for maintaining constant circadian rhythm. In normal life, the circadian rhythms of the sleep–wake pattern, body temperature, and melatonin secretion run synchronously. Body temperature becomes lowest in the middle of nocturnal sleep, and highest during afternoon hours. In addition, the secretion of melatonin starts a few hours before sleep onset, promoting the induction of human sleep. However, when a forced change in the sleep-awake pattern (desynchronization) occurs for some reason, unbearable feelings of sleepiness can occur during the daytime. The most important cause of desynchronized circadian rhythms is rotating shift work. According to the Ministry of Health, Labor and Welfare, 18.6% of companies in Japan adopted shift-work systems and 17.9% of the working population worked at night [50], suggesting that this is not a problem only for a small minority of workers. Those working on a shift schedule have different circadian rhythm timing than those of day workers. They are not only forced to stay awake and engaged in their daily work but also prone to develop insufficient sleep, because sleep after night shifts is shortened [51]. According to an analysis of 2570 adult subjects by Drake et al., 36%– 45% of those engaged in night work or shift work reported unbearable daytime sleepiness [52]. In a study by Scott et al., 600 out of 895 nurses reported that they had fallen asleep at the wheel at least once [53]. Scott et al. also found that 30 nurses reported driving in a sleepy state after shift work. Shift-work disorder (SWD) is a sleep disorder related to shift work, one that causes excessive sleepiness and/or complaints of nocturnal sleep [8]. The prevalence of SWD was 10.1% in day workers [54], 32.1% among night workers [54], 28.9% of nurses working on a three-shift rotation [55], 44.3% of those working on a two-shift rotation
5
[55], and 24.4% of nurses working with rapid-rotation schedules in Japan [56]. Our previous study of 3109 subjects engaged in shift work as public transportation drivers demonstrated that SWD was the main factor of EDS among them (Table 3). Notably, the strength of subjective sleepiness in drivers with SWD was higher than that of OSAS drivers [57]. In workers who met the criteria for SWD, there was a high incidence of accidents related with sleepiness [52], suggesting that early diagnosis and treatment of SWD is also important for ensuring traffic safety. However, SWD is often undiagnosed and untreated [58]. Because shift workers are no longer a small minority, and approximately 50% of professional drivers have irregular schedules or are engaged in nighttime driving [59], it is important to perform systematic SWD screenings to maintain both the physical and mental health of workers and to ensure traffic safety. As for the treatment of SWD, there are several available methods such as taking a short nap before or during night shifts, using bright light exposure and melatonin at appropriate times, and using drugs such as modafinil to stay awake as needed [60]. These methods were reported to be effective for maintaining wakefulness during shifts or for increasing the amount of nocturnal sleep [58]. However, no established study has investigated how these methods act to ensure the traffic safety of shift workers. 4. Sleepiness detection methods and accident countermeasures Because ocular variables (e.g., pupils, eye movement, and blinking) change with the level of sleepiness and can be measured without contact or restraint, several researchers have proposed methods for measuring drivers' sleepiness using ocular variables [61–65]. In a previous study, we investigated the detection capability of ocular variables for decreased vigilance or falling asleep while performing monotonous tasks that can easily induce sleepiness [66]. A cap-type head sensor and an eyetracking system (EMR-9; NAC Image Technology Inc., Tokyo, Japan) (Fig. 4) were used to record several ocular variables. Decreased blink frequency and pupil diameter, increased percentage of eyelid closure time (PERCLOS), and slow eye movement were observed as consecutive missed responses increased. Among these variables, PERCLOS was the most suitable for detecting missed responses and three or more consecutive missed responses. This result suggests that, among the ocular variables we assessed, PERCLOS can most effectively prevent error or accident caused by decreased vigilance while driving. Further study on the development of systems to alert drivers using this variable can be expected to prevent accidents due to sleepiness. As for countermeasures for drowsy driving, laboratory- and questionnaire-based epidemiological studies have demonstrated the effectiveness of napping and drinking coffee [67–69]. Taking a nap as a measure to counter sleepiness at the wheel is common among drivers between 46 and 64 years of age, those who have already experienced a sleep-related traffic accident, and those who have experienced severe sleepiness during driving [70]. A short nap is thought to be effective in
Table 2 Comparison of descriptive variables among the five groups with major hypersomnias. Komada et al., Sleep Medicine. 2008.
Behaviorally induced insufficient sleep syndrome Sleep apnea syndrome Idiopathic hypersomnia Narcolepsy Circadian rhythm sleep disorders
Mean age of initial visit
Mean age of symptoms
ESS score of the initial visit
BMI
Sleep length of weekday
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
30.2 45.1 31.4 31.0 27.7
7.3 12.1⁎⁎⁎ 9.0 13.3 8.1
28.6 – 19.2 17.2 18.9
7.5 – 7.3⁎⁎⁎ 7.5⁎⁎⁎ 6.4⁎⁎⁎
13.6 12.5 14.3 15.7 12.4
3.4 3.6⁎⁎ 3.0 3.0⁎⁎⁎ 3.7⁎
22.2 27.4 21.8 23.4 21.9
2.8 4.9⁎⁎⁎
5.5 6.1 6.3 6.4 7.8
0.8 1.0⁎⁎⁎ 1.1⁎⁎⁎ 1.3⁎⁎⁎ 2.3⁎⁎⁎
3.1 4.1⁎ 3.8
Results with post hoc test (compared with ISS).We exclude obstructive sleep apnea syndrome from the analysis of mean age of symptoms because the data for people with this syndrome in the population is unknown. ⁎⁎⁎ p b 0.0001. ⁎⁎ p b 0.01. ⁎ p b 0.05.
6
Y. Komada et al. / IATSS Research 37 (2013) 1–7
Table 3 The diagnoses of sleep disorders according to the International Classification of Sleep Disorders 2nd edition among drivers with subjective EDS (ESS ≥ 11). Asaoka et al., Journal of Occupational and Environmental Medicine. 2010.
Shift-work disorder Obstructive sleep apnea syndrome Behaviorally induced insufficient sleep syndrome Delayed sleep phase disorder Insomnia Idiopathic hypersomnia without long sleep time Periodic limb movement disorder Other Error in answering questionnaire Lost to follow-up Total
n
%
48 30 12 11 10 7 5 3 6 15 147
32.7 20.4 8.2 7.5 6.8 4.8 3.4 2.0 4.1 10.2 100.0
reducing sleepiness and maintaining the vigilance level. However, sleep inertia sometimes occurs after awakening from a short nap, and this could be a risk factor for accidents [71]. It was reported that a short nap with self-awakening was more effective in reducing sleepiness and sleep inertia than one with forced-awakening [71]. Another experimental study showed that sleep inertia after taking a nap during sleep deprivation can be prevented by hourly caffeine (0.3 mg/kg) intake [72]. Our study of about 4000 drivers demonstrated that 67.6% had experienced sleepiness while driving and 11.4% had fallen asleep at the wheel in the year preceding the investigation [73]. In that study, analysis of two groups—professional (about 700 subjects) and nonprofessional drivers (about 3300 subjects)—revealed that the rate of subjects experiencing traffic accidents caused by falling asleep in the last five years, and falling asleep at the wheel during the past year, was higher in professional drivers than in non-professional drivers (traffic accidents caused by falling asleep: 3.5% vs. 1.2%; falling asleep at the wheel: 17.8% vs. 10.1%, respectively). In addition, an analysis of measures taken to reduce sleepiness during driving revealed that the most frequently used method, used by more than 40% of subject drivers, both non-professional and professional, was “taking a rest.” Other measures included “chewing gum,” “opening a window,” and “drinking coffee,” all used by 30% of drivers; “napping” and “smoking,” used by 20% of drivers; and finally, “listening to the radio” and “talking with a passenger,” used by 10% of drivers. In that study, we also found that non-professional drivers are likely to take such measures when they feel sleepy or are in situations where prone to dozing off at the wheel. However, this tendency was not observed in professional drivers,
Fig. 4. Recordings using an eye-tracking system (EMR-9; NAC Image Technology Inc., Tokyo Japan). Abe et al., International Journal of Psychophysiology. 2011.
suggesting that they do not use naps as a countermeasure until they have experienced sleepiness-related traffic accidents. Undoubtedly, when sleepiness occurs during driving, drivers should take measure such as taking a break or drinking coffee, both of which have been reported to successfully reduce sleepiness and increase driving performance [74]. However, driving schedule constraints on professional drivers seem to make them less likely than non-professional drivers to take proactive measures to counter sleepiness while driving. It is therefore important to educate professional drivers and their employees about the mechanism of sleepiness-related vehicular accidents and the importance of strategies for coping with sleepiness. 5. Conclusion Sleepiness is a main factor responsible for traffic accidents caused by human error. People who sleep for fewer than 6 h have an increased risk of traffic accidents. Thus, the most essential thing to prevent traffic accidents due to sleepiness is ensuring that drivers get sufficient sleep at night. Of course, to prevent daytime sleepiness, it is important to maintain nocturnal sleep quality as well as an adequate amount of sleep. SAS is one of the most common and important sleep disorders, and makes nocturnal sleep shallow and fragmented. Patients affected with severe SAS may be especially likely to underestimate their own sleepiness. Considering that the risk of traffic accidents can be reduced close to that of healthy people by providing proper treatment, the early detection and treatment of SAS is desirable. Sleepiness-related accidents may have multiple causes. It is therefore important to address this matter from various approaches, including the maintenance of good sleep hygiene, measures to reduce sleepiness, and the prevention and treatment of sleep disorders. In addition, we want to emphasize the need to establish and maintain appropriate working conditions for drivers. References [1] J.A. Horne, L.A. Reyner, Sleep related vehicle accidents, BMJ 310 (1995) 565–567. [2] M.M. Ohayon, R.G. Priest, J. Zulley, S. Smirne, T. Paiva, Prevalence of narcolepsy symptomatology and diagnosis in the European general population, Neurology 58 (2002) 1826–1833. [3] X. Liu, M. Uchiyama, K. Kim, M. Okawa, K. Shibui, Y. Kudo, Y. Doi, M. Minowa, R. Ogihara, Sleep loss and daytime sleepiness in the general adult population of Japan, Psychiatry Research 93 (2000) 1–11. [4] NHK Broadcasting Culture Research Institute, NHK Data Book 2010 National Time Use SurveyNHK Publishing, Inc., Tokyo, 2011. [5] C. Hublin, J. Kaprio, M. Partinen, M. Koskenvuo, Insufficient sleep—a populationbased study in adults, Sleep 24 (2001) 392–400. [6] T. Ohida, A.M. Kamal, M. Uchiyama, K. Kim, S. Takemura, T. Sone, T. Ishii, The influence of lifestyle and health status factors on sleep loss among the Japanese general population, Sleep 24 (2001) 333–338. [7] H.P. Van Dongen, G. Maislin, J.M. Mullington, D.F. Dinges, The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation, Sleep 26 (2003) 117–126. [8] American Academy of Sleep Medicine, International Classification of Sleep Disorders: Diagnostic and Coding Manual, 2nd ed. American Academy of Sleep Medicine, Westchester, Illinois, 2005. [9] T. Abe, Y. Komada, Y. Nishida, K. Hayashida, K. Inoue, Short sleep duration and long spells of driving are associated with the occurrence of Japanese drivers' rearend collisions and single-car accidents, Journal of Sleep Research 19 (2010) 310–316. [10] T. Abe, Y. Komada, S. Asaoka, A. Ozaki, Y. Inoue, Questionnaire-based evidence of association between sleepiness while driving and motor vehicle crashes that are subjectively not caused by falling asleep, Sleep and Biological Rhythms 9 (2011) 134–143. [11] M.S. Aldrich, Automobile accidents in patients with sleep disorders, Sleep 12 (1989) 487–494. [12] T. Young, J. Blustein, L. Finn, M. Palta, Sleep-disordered breathing and motor vehicle accidents in a population-based sample of employed adults, Sleep 20 (1997) 608–613. [13] K. Kim, M. Uchiyama, M. Okawa, X. Liu, R. Ogihara, An epidemiological study of insomnia among the Japanese general population, Sleep 23 (2000) 41–47. [14] J.C. Souza, L.A. Magna, R. Reimao, Insomnia and hypnotic use in Campo Grande general population, Brazil, Arquivos de Neuro-Psiquiatria 60 (2002) 702–707. [15] M.M. Ohayon, Epidemiology of insomnia: what we know and what we still need to learn, Sleep Medicine Reviews 6 (2002) 97–111. [16] C.L. Drake, T. Roehrs, T. Roth, Insomnia causes, consequences, and therapeutics: an overview, Depression and Anxiety 18 (2003) 163–176.
Y. Komada et al. / IATSS Research 37 (2013) 1–7 [17] M.M. Ohayon, Epidemiological study on insomnia in the general population, Sleep 19 (1996) S7–S15. [18] S. Englert, M. Linden, Differences in self-reported sleep complaints in elderly persons living in the community who do or do not take sleep medication, The Journal of Clinical Psychiatry 59 (1998) 137–144. [19] Y. Komada, T. Shiomi, K. Mishima, Y. Inoue, Associated factors for drowsy driving among licenced driver, Japanese Journal of Public Health 57 (2010) 1066–1074. [20] K. Komada, T. Nomura, M. Kusumi, K. Nakashima, I. Okajima, T. Sasai, Y. Inoue, Correlations among insomnia symptoms, sleep medication use and depressive symptoms, Psychiatry and Clinical Neurosciences 65 (2011) 20–29. [21] D.E. Moul, E.A. Nofzinger, P.A. Pilkonis, P.R. Houck, J.M. Miewald, D.J. Buysse, Symptom reports in severe chronic insomnia, Sleep 25 (2002) 553–563. [22] E. Fortier-Brochu, S. Beaulieu-Bonneau, H. Ivers, C.M. Morin, Relations between sleep, fatigue, and health-related quality of life in individuals with insomnia, Journal of Psychosomatic Research 69 (2010) 475–483. [23] J.D. Edinger, M.K. Means, C.E. Carney, A.D. Krystal, Psychomotor performance deficits and their relation to prior nights' sleep among individuals with primary insomnia, Sleep 31 (2008) 599–607. [24] J.A. Shekleton, N.L. Rogers, S.M. Rajaratnam, Searching for the daytime impairments of primary insomnia, Sleep Medicine Reviews 14 (2010) 47–60. [25] E. Altena, Y.D. Van Der Werf, R.L. Strijers, E.J. Van Someren, Sleep loss affects vigilance: effects of chronic insomnia and sleep therapy, Journal of Sleep Research 17 (2008) 335–343. [26] J. Menzin, K.M. Lang, P. Levy, E. Levy, A general model of the effects of sleep medications on the risk and cost of motor vehicle accidents and its application to France, PharmacoEconomics 19 (2001) 69–78. [27] M. Partinen, K. Hirvonen, C. Hublin, M. Halavaara, H. Hiltunen, Effects of aftermidnight intake of zolpidem and temazepam on driving ability in women with non-organic insomnia, Sleep Medicine 4 (2003) 553–561. [28] C.F. George, Sleep apnea, alertness, and motor vehicle crashes, American Journal of Respiratory and Critical Care Medicine 176 (2007) 954–956. [29] C.F. George, P.W. Nickerson, P.J. Hanly, T.W. Millar, M.H. Kryger, Sleep apnoea patients have more automobile accidents, Lancet 330 (1987) 447. [30] S. Tregear, J. Reston, K. Schoelles, B. Phillips, Obstructive sleep apnea and risk of motor vehicle crash: systematic review and meta-analysis, Journal of Clinical Sleep Medicine 5 (2009) 573–581. [31] A. Sassani, L.J. Findley, M. Kryger, E. Goldlust, C. George, T.M. Davidson, Reducing motor-vehicle collisions, costs, and fatalities by treating obstructive sleep apnea syndrome, Sleep 27 (2004) 453–458. [32] Y. Komada, Y. Nishida, K. Namba, T. Abe, S. Tsuiki, Y. Inoue, Elevated risk of motor vehicle accident for male drivers with obstructive sleep apnea syndrome in the Tokyo metropolitan area, The Tohoku Journal of Experimental Medicine 219 (2009) 11–16. [33] S. Tregear, J. Reston, K. Schoelles, B. Phillips, Continuous positive airway pressure reduces risk of motor vehicle crash among drivers with obstructive sleep apnea: systematic review and meta-analysis, Sleep 33 (2010) 1373–1380. [34] M. Orth, H.W. Duchna, M. Leidag, W. Widdig, K. Rasche, T.T. Bauer, J.W. Walther, J. de Zeeuw, J.P. Malin, G. Schultze-Werninghaus, S. Kotterba, Driving simulator and neuropsychological testing in OSAS before and under CPAP therapy, The European Respiratory Journal 26 (2005) 898–903. [35] T. Young, P.E. Peppard, D.J. Gottlieb, Epidemiology of obstructive sleep apnea: a population health perspective, American Journal of Respiratory and Critical Care Medicine 165 (2002) 1217–1239. [36] R.L. Ellen, S.C. Marshall, M. Palayew, F.J. Molnar, K.G. Wilson, M. Man-Son-Hing, Systematic review of motor vehicle crash risk in persons with sleep apnea, Journal of Clinical Sleep Medicine 2 (2006) 193–200. [37] A.T. Mulgrew, G. Nasvadi, A. Butt, R. Cheema, N. Fox, J.A. Fleetham, C.F. Ryan, P. Cooper, N.T. Ayas, Risk and severity of motor vehicle crashes in patients with obstructive sleep apnoea/hypopnoea, Thorax 63 (2008) 536–541. [38] G. Maycock, Sleepiness and driving: the experience of UK car drivers, Journal of Sleep Research 5 (1997) 229–237. [39] N.B. Powell, K.B. Schechtman, R.W. Riley, C. Guilleminault, R.P. Chiang, E.M. Weaver, Sleepy driver near-misses may predict accident risks, Sleep 30 (2007) 331–342. [40] S. Garbarino, L. Nobili, M. Beelke, F. De Carli, F. Ferrillo, The contributing role of sleepiness in highway vehicle accidents, Sleep 24 (2001) 203–206. [41] L. Findley, M. Unverzagt, R. Guchu, M. Fabrizio, J. Buckner, P. Suratt, Vigilance and automobile accidents in patients with sleep apnea or narcolepsy, Chest 108 (1995) 619–624. [42] C.F. George, A.C. Boudreau, A. Smiley, Comparison of simulated driving performance in narcolepsy and sleep apnea patients, Sleep 19 (1996) 711–717. [43] A. Ozaki, Y. Inoue, T. Nakajima, K. Hayashida, M. Honda, Y. Komada, K. Takahashi, Health-related quality of life among drug-naïve patients with narcolepsy with cataplexy, narcolepsy without cataplexy, and idiopathic hypersomnia without long sleep time, Journal of Clinical Sleep Medicine 4 (2008) 572–578. [44] T. Roehrs, F. Zorick, J. Sicklesteel, R. Wittig, T. Roth, Excessive daytime sleepiness associated with insufficient sleep, Sleep 6 (1983) 319–325. [45] Y. Komada, Y. Inoue, K. Hayashida, T. Nakajima, M. Honda, K. Takahashi, Clinical significance and correlates of behaviorally induced insufficient sleep syndrome, Sleep Medicine 9 (2008) 851–856. [46] M.S. Aldrich, Insufficient sleep syndrome, in: M. Billiard (Ed.), Sleep: Physiology, Investigations, and Medicine, Kluwer Academic/Plenum Publishers, New York, 2003, pp. 341–346.
7
[47] J.E. Broman, L.G. Lundh, J. Hetta, Insufficient sleep in general population, Neurophysiologie Clinique 26 (1996) 30–39. [48] T. Roehrs, V. Timms, A. Zwyghuizen-Doorenbos, R. Buzenski, T. Roth, Polysomnographic, performance, and personality differences of sleepy and alert normals, Sleep 13 (1990) 395–402. [49] P.M. Turkington, M. Sircar, V. Allgar, M.W. Elliot, Relationship between obstructive sleep apnoea, driving simulator performance, and risk of road traffic accidents, Thorax 56 (2001) 800–805. [50] Ministry of Health, Labour and Welfare, Annual Health, Labour and Welfare Report 2007, 2007. [51] T. Åkerstedt, Shift work and disturbed sleep/wakefulness, Occupational Medicine 53 (2003) 89–94. [52] C.L. Drake, T. Roehrs, G. Richardson, J.K. Walsh, T. Roth, Shift work sleep disorder: prevalence and consequences beyond that of symptomatic day workers, Sleep 27 (2004) 1453–1462. [53] L.D. Scott, W.T. Hwang, A.E. Rogers, T. Nysse, G.E. Dean, D.F. Dinges, The relationship between nurse work schedules, sleep duration, and drowsy driving, Sleep 30 (2007) 1801–1807. [54] L. Di Milia, S. Waage, S. Pallesen, B. Bjorvatn, Shift work disorder in a random population sample-prevalence and comorbidities, PloS One 8 (2013) e55306. [55] E. Flo, S. Pallesen, N. Magerøy, B.E. Moen, J. Grønli, I. Hilde Nordhus, B. Bjorvatn, Shift work disorder in nurses-assessment, prevalence and related health problems, PloS One 7 (2012) e33981. [56] S. Asaoka, S. Aritake, Y. Komada, A. Ozaki, Y. Odagiri, S. Inoue, T. Shimomitsu, Y. Inoue, Factors associated with shift work disorder in nurses working with rapid-rotation schedules in Japan: the nurses' sleep health project, Chronobiology International 30 (2013) 628–636. [57] S. Asaoka, K. Namba, S. Tsuiki, Y. Komada, Y. Inoue, Excessive daytime sleepiness among Japanese public transportation drivers engaged in shiftwork, Journal of Occupational and Environmental Medicine 52 (2010) 813–818. [58] J.R. Schwartz, T. Roth, Shift work sleep disorder: burden of illness and approaches to management, Drugs 66 (2006) 2357–2370. [59] A.I. Pack, D.F. Dinges, G. Maislin, A study of prevalence of sleep apnea among commercial truck drivers, Federal Motor Carrier Safety Administration Publication No DOT-RT-02-030 Washington, DC, 2002. [60] R.L. Sack, D. Auckley, R.R. Auger, M.A. Carskadon, K.P. Jr, M.V. Vitiello Wright, I.V. Zhdanova, Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders: An American Academy of Sleep Medicine review, Sleep 30 (2007) 1460–1483. [61] T. Åkerstedt, M. Ingre, G. Kecklund, A. Anund, D. Sandberg, M. Wahde, P. Philip, P. Kronberg, Reaction of sleepiness indicators to partial sleep deprivation, time of day and time on task in a driving simulator: the DROWSI project, Journal of Sleep Research 19 (2010) 298–309. [62] D.F. Dinges, M. Mallis, G. Maislin, J.W. Powell, Evaluation of Techniques for Ocular Measurement as an Index of Fatigue and as the Basis for Alertness Management, U.S. Department of Transportation, National Highway Traffic Safety Administration, 1998. [63] M.W. Johns, A. Tucker, R. Chapman, K. Crowley, N. Michael, Monitoring eye and eyelid movements by infrared reflectance oculography to measure drowsiness in drivers, Somnologie 11 (2007) 234–242. [64] D. Shin, H. Sakai, Y. Uchiyama, Slow eye movement detection can prevent sleep-related accidents effectively in a simulated driving task, Journal of Sleep Research 20 (2011) 416–424. [65] A. Ueno, S. Kokubun, Y. Uchikawa, A prototype real-time system for assessing vigilance levels and for alerting the subject with sound stimulation, International Journal of Assistive Robotics and Mechatronics 8 (2007) 19–27. [66] T. Abe, T. Nonomura, Y. Komada, S. Asaoka, T. Sasai, A. Ueno, Y. Inoue, Detecting deteriorated vigilance using percentage of eyelid closure time during behavioral maintenance of wakefulness tests, International Journal of Psychophysiology 82 (2011) 269–274. [67] J. Horne, L. Reyner, Vehicle accidents related to sleep: a review, Occupational and Environmental Medicine 56 (1999) 289–294. [68] P. Philip, J. Taillard, N. Moore, S. Delord, C. Valtat, P. Sagaspe, B. Bioulac, The effects of coffee and napping on nighttime highway driving: a randomized trial, Annals of Internal Medicine 144 (2006) 785–791. [69] P. Sagaspe, J. Taillard, G. Chaumet, N. Moore, B. Bioulac, P. Philip, Aging and nocturnal driving: better with coffee or a nap? A randomized study, Sleep 30 (2007) 1808–1813. [70] A. Anund, G. Kecklund, B. Peters, T. Åkerstedt, Driver sleepiness and individual differences in preferences for countermeasures, Journal of Sleep Research 17 (2008) 16–22. [71] K. Kaida, H. Nittono, M. Hayashi, T. Hori, Effects of self-awakening on sleep structure of a daytime short nap and on subsequent arousal levels, Perceptual and Motor Skills 97 (2003) 1073–1084. [72] H.P. Van Dongen, N.J. Price, J.M. Mullington, M.P. Szuba, S.C. Kapoor, D.F. Dinges, Caffeine eliminates psychomotor vigilance deficits from sleep inertia, Sleep 24 (2001) 813–819. [73] S. Asaoka, T. Abe, Y. Komada, Y. Inoue, The factors associated with preferences for napping and drinking coffee as countermeasures for sleepiness at the wheel among Japanese drivers, Sleep Medicine 13 (2012) 354–361. [74] S.V. Heatherle, Caffeine withdrawal, sleepiness, and driving performance: what does the research really tell us? Nutritional Neuroscience 14 (2011) 89–95.
Contents lists available at SciVerse ScienceDirect
IATSS Research
Short sleep duration, sleep disorders, and traffic accidents Yoko Komada, Shoichi Asaoka, Takashi Abe, Yuichi Inoue ⁎ Department of Somnology, Tokyo Medical University, Japan
a r t i c l e
i n f o
Article history: Received 26 March 2013 Received in revised form 3 June 2013 Accepted 4 June 2013 Keywords: Sleepiness Sleep apnea syndrome Narcolepsy Insufficient sleep Traffic accident Countermeasure
a b s t r a c t Sleepiness is an important factor in traffic accidents caused by human error. The purpose of this paper is to review a number of studies conducted over the years regarding the effect of the lack of sleep on the incidence of traffic accidents as well as the individual effects of various sleep disorders on accidents. In addition, we discuss recent advances in methods of detecting sleepiness and strategies for preventing traffic accident by using these methods. © 2013 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved.
Contents
1. 2. 3.
Introduction . . . . . . . . . . . . . . . . . . . . . . Lack of sleep and accidents . . . . . . . . . . . . . . . . Sleep disorders and accidents . . . . . . . . . . . . . . 3.1. Insomnia . . . . . . . . . . . . . . . . . . . . . 3.2. Sleep apnea syndrome . . . . . . . . . . . . . . 3.3. Narcolepsy . . . . . . . . . . . . . . . . . . . . 3.4. Behaviorally-induced insufficient sleep syndrome . . 3.5. Shift-work disorder . . . . . . . . . . . . . . . . 4. Sleepiness detection methods and accident countermeasures 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
1. Introduction In April 2012 a bus driver in Japan who fell asleep at the wheel caused a disastrous accident that took the lives of 7 people and injured ⁎ Corresponding author at: Department of Somnology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan. Tel.: +81 3 3342 6111; fax: +81 3 3342 7083. E-mail address: [email protected] (Y. Inoue). Peer review under responsibility of International Association of Traffic and Safety Sciences.
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
1 2 3 3 3 4 4 5 5 6 6
a further 39. The bus, on its way from Kanazawa to Tokyo, hit a roadside wall on the Kanetsu Expressway around dawn. No brake or skid marks were found at the site of the accident; the Gunma Prefectural Police reported that the driver had “fallen asleep.” Around the same time in Kameoka City, Kyoto, a mini-car ran into a group of children walking to school with their guardians, hitting 10 people, of whom 3 died and 7 were severely injured. This accident reportedly involved an unlicensed 18-year-old driver who fell asleep at the wheel. Generally, accidents caused by drowsiness and falling asleep are the result of drivers being unable to control the brakes or steering due to their impaired state. Furthermore, because such accidents often occur at high speeds, there is a much greater mortality rate or risk of serious injuries [1]. Sleepiness is an important factor in traffic accidents caused by human error. One study of 19,000 subjects across five European
0386-1112/$ – see front matter © 2013 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.iatssr.2013.06.001
Y. Komada et al. / IATSS Research 37 (2013) 1–7
countries [2], as well as another of 3000 Japanese adults [3], found that excessive daytime sleepiness (EDS) reached as much as 15%. The main causes of EDS are (1) the lack of sleep, (2) deterioration in the quality of sleep, (3) disruption of circadian rhythms, and (4) primary hypersomnia. In terms of lack of sleep, it has been suggested that lifestyles requiring activity around the clock or late at night are the main cause of this condition. In 1960, 90% of people reportedly went to sleep at 11:00 PM and slept for an average of more than 8 h, but the number of people active late at night has gradually risen, resulting in shorter sleeping times. In 2010, half of the population was still awake at 11:00 PM and the mean sleeping time was only 7 h and 14 min, suggesting a reduction of around 1 h of sleeping time compared with 40 years ago [4] (Fig. 1). In a study conducted on the general population (n = 12,000) in Finland, 20.4% of participants were found to have insufficient sleep [5], while a study of 4000 adult subjects in Japan revealed that 28% had fewer than 6 h of sleep each night [6]. Thus, there appears to be a high rate of insufficient sleep in developed countries. Of course, people with chronically short sleeping times often have EDS. However, although an accumulated lack of nocturnal sleep can result in serious deficits in neurobehavioral function, the increase in subjective sleepiness under such conditions remains mild. That is, people with chronic lack of adequate sleep may underestimate their own sleepiness [7]. Unwanted sleepiness may also occur due to the disruption of circadian rhythms in situations such as jet lag or shift work, as well as primary circadian rhythm sleep disorders such as delayed sleep phase. People whose quality of sleep deteriorates as a result of sleep disorders that cause frequent interruption of nocturnal sleep, such as obstructive sleep apnea syndrome and periodic limb movement disorder, can develop secondary hypersomnia. In addition, while primary hypersomnia such as narcolepsy and idiopathic hypersomnia is relatively rare, it can cause serious problems with EDS [8]. In this report, we survey a number of studies conducted over the years regarding the effect of the lack of sleep on the incidence of traffic accidents as well as the individual effects of various sleep disorders on accidents. In addition, we discuss recent advances in methods of detecting sleepiness and strategies for preventing traffic accident by using these methods.
2. Lack of sleep and accidents In a previous study, we sought to identify a correlation between the occurrence of traffic accidents due to falling asleep at the wheel and sleep duration on the day before the accident. We analyzed 1772 of the 4871 traffic accidents that occurred in Tsukuba City from August 1993 to December 2003, excluding those caused by drunk driving [9]. First, accidents were categorized by type as rear-end collisions (n = 240), single-car accidents (n = 293), or other accidents (n = 1239). A rear-end collision was defined as a trailing car crashing into the rear of a leading vehicle. A single-car accident was defined as a car crashing against a structure on a road or shoulder such as a parked vehicle, wall, house, or telegraph pole. Accidents involving interaction with other vehicles or persons were classified as other accidents. Our analysis of the time of day that each accident occurred revealed that rear-end collisions most frequently occurred between 8:00 and 9:00 AM. On the other hand, single-car accidents occurred more frequently during the night than during the day (Fig. 2). These findings suggest that the time zone of accident occurrence differs by the type of accident. The risk of rearend collisions grows with increased traffic density, especially during the morning rush hour, which may lead to less space between cars. In contrast, it was hypothesized that single-car accidents could be attributed to low nighttime traffic density that reduced driver alertness and increased driving speed. For both rear-end collisions and single-car accidents, a higher percentage of subjects were found to have had less than 6 h of sleep on the day before the accident than for other accidents (11.3% in rearend collisions, 10.2% in single-car accidents, 4.8% in other accidents). Multivariate logistic regression analysis showed that the occurrence of
a Number of accidents
2
300 250 200 150 100 50 12:00
14:00
16:00
18:00
20:00
22:00
10:00
12:00
14:00
16:00
18:00
20:00
22:00
6:00 6:00
8:00
4:00 4:00
10:00
2:00 2:00
8:00
0:00 0:00
0
Proportion of each accident in each time zone (%)
b 100 80 60 40 20 0
Time of day Fig. 1. Changes in Japanese sleep duration and percentage of people staying awake past 11:00 PM. This figure shows the percentage of Japanese people who stay awake past 11:00 PM on weekdays and the average subjective total sleep time from 1960 to 2010. In 1960, 90% of the population were already asleep at 11:00 PM and typically slept for over 8 h. However, sleeping times gradually fell over the surveyed period. In 2010, half of the population remained awake past 11:00 PM with an average sleeping time of 7 h and 14 min. Created by the NHK National Time Life Survey.
Accidents of other types Single-car accidents Rear-end collisions Fig. 2. (a) Time of day distribution of all accidents, and (b) proportion of rear-end collisions, single-car accidents and other accidents among all accidents in each time zone. Abe et al., Journal of Sleep Research. 2010.
Y. Komada et al. / IATSS Research 37 (2013) 1–7
rear-end collisions was significantly associated with sleep duration of less than 6 h and more frequent driving, while the occurrence of single-car accidents was significantly associated with younger age (≤25 years old), sleep duration of less than 6 h, the increment between spells of driving, and nighttime (21:00–06:00) driving. In another study, we administered a questionnaire in October 2008 to approximately 4000 non-professional drivers and investigated factors associated with motor vehicle accidents (MVAs). The results obtained were as follows: self-reported sleep duration on weekdays of less than 6 h (OR = 8.02, 95% confidence interval [CI]: 1.08–59.60, p b .05), more than 6 h and less than 7 h (OR = 6.28, 95% CI: 0.83– 47.43, p = .07), and loud snoring or apnea (OR = 2.07, 95% CI: 1.12– 3.82, p b .05) were all associated with an increased risk of MVAs [10]. This result suggests that in order to prevent MVAs caused by falling asleep, drivers should have adequate sleep and undergo screening for sleep apnea syndrome. 3. Sleep disorders and accidents The International Classification of Sleep Disorders [8], includes the following classifications for sleep disorders: insomnia, sleep-related breathing disorders, hypersomnias of central origin, circadian rhythm sleep disorders, parasomnias, sleep-related movement disorders, isolated symptoms, and other sleep disorders. Among them, drivers with sleep disorders that can cause severe EDS such as sleep apnea syndrome or hypersomnias of central origin are reported to have 1.5–4 times greater risk of traffic accidents than drivers without any sleep disorder [11,12]. Undoubtedly, diagnosis and treatment of these sleep disorders are important to reduce traffic accidents caused by falling asleep at the wheel. Here, we focus on several sleep disorders, all of which are associated with an increased risk of traffic accidents. In addition to introducing accident conditions for each disorder, which have been published previously, we discuss issues that should be clarified to keep traffic safe from driving problems caused by the disorders. 3.1. Insomnia Insomnia is known to be common [13–15], affecting approximately 10% to 15% of the general population [2,16]. In addition, the rate of occasional sleep medication use in the general population is approximately 3% to 11% [17–19]. In people with insomnia symptoms, the rate is approximately 26% [20]. Nocturnal insomnia is frequently associated with daytime sleepiness and fatigue [21,22], psychomotor deficits [23,24] and cognitive impairments [25], but no study has yet revealed a direct correlation between insomnia and an increased risk of traffic accidents. The residual effects of hypnotics the next morning, however, may lead to substantial impairment in psychomotor functioning, possibly increasing the risk of motor vehicle accidents, although various prescription hypnotics may be equally effective in promoting sleep [26]. A study on the effects of after-midnight intake of zolpidem and temazepam on the driving ability of 18 insomniac women using a driving simulator revealed that 5.5 h after administration there were no major differences in psychomotor performance in women who had taken these two hypnotics compared with those who had taken a placebo, indicating an absence of significant residual effects early the next morning [27]. However, certain subjects were more susceptible than others to the drugs' effects. This underlines the necessity to strongly advocate against taking hypnotics late at night if patients intend to drive a car early the next morning. 3.2. Sleep apnea syndrome Sleep apnea syndrome (SAS), with its repeated episodes of nocturnal hypoxemia and sleep fragmentation, increases sleepiness, which in turn increases inattention while driving [28]. Following the initial report by George et al. in 1987 [29], the risk of accident in SAS patients due to
3
falling asleep at the wheel has been studied by numerous researchers [28,30]. The results of a meta-analysis study by Sassani et al. [31] showed that the odds ratio of traffic accidents increased in people with SAS by 2.52 (95% CI: 1.84–3.45). Our systematic investigation of MVA risk among Japanese drivers with obstructive sleep apnea syndrome (OSAS) revealed that the odds ratios for MVAs and dozing off at the wheel in the OSAS group compared with the general population were 2.4 (95% CI: 1.6–3.4) and 13.2 (95% CI: 10.0–17.4), respectively [32]. Multivariate logistic regression analysis revealed that MVAs were significantly associated with either high scores on the Epworth Sleepiness Scale (ESS ≥ 11) or frequent respiratory disorder events (apnea Hypopnea Index: AHI ≥ 40/h). Further studies have found that long-term continuous positive airway pressure (CPAP) treatment was clearly effective in reducing the number of MVAs [32,33]. In our study indicated above, the proportion of subjects who experienced MVAs was significantly higher in the OSAS group at baseline compared with the control group and OSAS group at the follow-up period (OSAS group at the baseline: 16.8%; control group: 4.7%; OSAS group at follow-up period: 3.1%; p b 0.01). Furthermore, there was no significant difference in the rate between the control group and the CPAP-treated OSAS group at follow-up. Results from a study using driving simulators also demonstrated a significant improvement in subjective sleepiness and driving performance in CPAP-treated OSAS patients [34]. Interestingly, in our study AHI scores were significantly higher in those who had multiple MVAs than in those who had only a single MVA, despite the ESS scores of the former group being significantly lower (Fig. 3). This finding supports the hypothesis that self-reported measures tend to underestimate the severity of sleepiness in severe OSAS patients [35]. In addition, in a systematic review examining MVA rates in OSAS patients, ESS scores did not appear to be predictive of crashes in 8 of the 15 studies examined [36]. Mulgrew et al. [37] also reported no significant relationship between subjective sleepiness and MVA rate, and suggested that patients who are less aware of their impaired vigilance may be at much higher risk. Thus, we should consider that MVAs might occur when subjective measures of sleepiness are lower than expected from the AHI, especially in patients severely affected by OSAS. Therefore, early detection and treatment of severe OSAS should be promoted to prevent multiple MVAs, regardless of whether there is subjective sleepiness. In order to elucidate the current rate of falling asleep at the wheel among driver's license holders and to understand the correlation between falling asleep at the wheel and SAS, approximately 5000 driver's license holders who went for renewal were asked to answer an anonymous and voluntary questionnaire in September 2006 (respondents: 3235; response rate: 61.8%). As mentioned above, the percentage of people with EDS is about 15% of the general population [2,3]. The results of this study, however, revealed that around 40.4% of the 3235 respondents had experienced sleepiness while driving [19]. Thus, sleepiness can easily occur among ordinary drivers in daily life while driving a vehicle. Furthermore, 20.3% of driver's license holders reported having fallen asleep at the wheel while 10.4% had experienced near-miss accidents or actually had accidents due to falling asleep at the wheel [19]. Other studies from Western countries revealed that 29% of subjects had experienced almost falling asleep at the wheel [38] while 18.3% had experienced near misses due to falling asleep at the wheel [39]. In addition, 1.3% had experienced an actual accident [39]. Other studies have reported the percentage of accidents that occur in relation to sleepiness to be around 20% [1,40]. Looking at these studies, the occurrence of accidents in Japanese drivers is at least the same as or a little bit higher than for drivers in Western countries, and there is a clear association between sleepiness and traffic accidents. Factors related to falling asleep at the wheel are being male, having a driver's license for a long period, longer weekly driving distance, appearance of sleepiness even after a short driving time, and selfawareness of having SAS or has been diagnosed with SAS [19]. An
4
Y. Komada et al. / IATSS Research 37 (2013) 1–7
p<0.01 160
p<0.01
p<0.05
25
p<0.05
20
ESS score
AHI
120
80
15
10
40 5
0
0 =0
=1
2
=0
=1
2
Number of car accidents within past 5 years Fig. 3. Comparison of AHI (left panel) and ESS score (right panel) between groups categorized by number of MVAs (Komada et al., Tohoku Journal of Experimental Medicine. 2009). Group without MVA: n = 496, Group with one MVA: n = 56, Group with two or more MVAs: n = 18. AHI: F2,567 = 7.2, p b 0.001; ESS: F2,567 = 15.9, p b 0.0001. AHI: Apnea hypopnea index; ESS: Epworth sleepiness scale.
analysis conducted on driver's license holders who had SAS revealed that 7.5% responded that they “might suffer from SAS,” whereas 1.1% responded that they “were diagnosed with SAS.” However, that this study was of driver's license holders who had come to the driver's license examination center for license renewal may have introduced a sampling bias. Despite this, because the percentage of drivers who had been diagnosed with SAS among those who thought that they might have SAS remained low, it may be important to promote early diagnosis and treatment of SAS in order to prevent as-yet-undiagnosed drivers from falling asleep at the wheel. Furthermore, it is also important to disseminate information about the relationship between exhaustion due to driving for long periods, falling asleep at the wheel, and accidents resulting from falling asleep. 3.3. Narcolepsy Narcolepsy is a sleep disorder closely related to EDS. Usually, a normal person does not fall asleep during driving or while having a conversation, but people suffering from narcolepsy have such tendencies. In addition, cataplexy triggered with certain kinds of emotions may also occur. That is, bodily muscle tone is completely lost when a strong emotional reaction occurs. In general, sleepiness in narcolepsy patients is reportedly stronger than in SAS patients. For this reason, the deterioration of driving performance in patients with narcolepsy has been systematically studied using a simulator [41,42]. According to Aldrich, the motor vehicular accident rate due to sleepiness in the general population is around 5%; however, that rate increases up to 50% in narcoleptic patients [11]. Another previous study found that 75% of narcolepsy patients with cataplexy and 50% of those without cataplexy had experienced traffic accidents or near misses in the last five years [43]. The results of a logistic regression analysis showed that ESS scores were significantly associated with increased automobile accidents and near misses (severe; OR = 14.6, 95% CI: 2.0–108.7) [43]. 3.4. Behaviorally-induced insufficient sleep syndrome In the 2nd edition of the ICSD, behaviorally induced insufficient sleep syndrome (BIISS) is classified as a category of “hypersomnia of central origin which is not due to a circadian rhythm sleep disorder, sleep-related breathing disorder, or other cause of disturbed nocturnal sleep” [8]. Unlike narcolepsy, which occurs based on decreased
orexinergic control of wakefulness, patients with BIISS are unable to maintain normal alertness and wakefulness due to a chronic lack of sleep. In reports from other countries, 2% of patients who visited a sleep disorder center with any sleep complaint and 6% of those with EDS were diagnosed to have BIISS [44]. Our previous study showed that among the 1243 patients who visited our clinic due to EDS, the percentage of patients diagnosed with BIISS was 7.1% [45]. This rate was higher than those for circadian rhythm sleep disorders and periodic limb movement disorders, despite being lower than the rate for major hypersomnias such as sleep apnea syndrome, idiopathic hypersomnia, and narcolepsy (Table 1). Considering this, cases with EDS caused by chronic insufficient sleep should not be ignored clinically. Furthermore, the rate of the population with chronic EDS in epidemiological surveys is markedly higher than the rate of patients with BIISS who consult medical institutes. That is, most people with BIISS are thought unlikely to seek medical assistance. We believe that it is necessary to raise awareness of the significance of chronic sleep insufficiency in the general population. Symptoms of BIISS include fatigue, irritation, depression, muscle pain, concentration disturbance, and a decline in cognitive function as well as daytime vigilance [46,47]. Another study confirmed that Table 1 Diagnoses of 1243 patients with excessive daytime sleepiness. Komada et al., Sleep Medicine. 2008. Diagnosis
n
%
Obstructive sleep apnea syndrome Idiopathic hypersomnia Narcolepsy Behaviorally induced insufficient sleep syndrome Circadian rhythm sleep disorders Sleep disorders associated with mental disorders Periodic limb movement disorder or restless legs syndrome Insomnia Parasomnias Long sleeper Recurrent hypersomnia More than two diseases causative for daytime sleepiness (Of which ISS + other hypersomnia) Undiagnosed
431 136 109 88 76 54 33 30 14 12 3 69 25 188
34.7 10.9 8.8 7.1 6.1 4.3 2.7 2.4 1.1 1.0 0.2 5.6 2.0 15.1
Undiagnosed: Patients who did not have a confirmed diagnosis due to interruption of diagnostic examination or treatment, or patients in whom two clinicians did not completely agree on the final diagnosis.
Y. Komada et al. / IATSS Research 37 (2013) 1–7
the performance of tasks that require both concentration and vigilance was reduced in populations with BIISS [48]. In our study, the ESS score of people with BIISS at an initial assessment was 13.6 (SD = 3.4), which was significantly lower than that of narcolepsy patients, significantly higher than that of people with SAS and circadian rhythm sleep disorders, and on the same level as those with idiopathic hypersomnia (Table 2). Furthermore, among people with BIISS, 22.1% had experienced driving or work-related accidents or near misses. Considering that the traffic accident rate due to falling asleep remains below 3% in the general population [49], the accident rate of people with BIISS may be much higher. Compared with the group who had no such experiences, the ESS scores of the group that had experienced accidents or near misses was significantly higher (group with accident experience: 15.5 (SD = 3.8) points, group without accident experience: 13.0 (SD = 3.1) points; p b .01). 3.5. Shift-work disorder The period length of circadian rhythm in humans, including sleep– wake pattern, melatonin hormone secretory pattern, and body temperature, exceeds 24 h without light–dark changes and time information, both of which are crucial for maintaining constant circadian rhythm. In normal life, the circadian rhythms of the sleep–wake pattern, body temperature, and melatonin secretion run synchronously. Body temperature becomes lowest in the middle of nocturnal sleep, and highest during afternoon hours. In addition, the secretion of melatonin starts a few hours before sleep onset, promoting the induction of human sleep. However, when a forced change in the sleep-awake pattern (desynchronization) occurs for some reason, unbearable feelings of sleepiness can occur during the daytime. The most important cause of desynchronized circadian rhythms is rotating shift work. According to the Ministry of Health, Labor and Welfare, 18.6% of companies in Japan adopted shift-work systems and 17.9% of the working population worked at night [50], suggesting that this is not a problem only for a small minority of workers. Those working on a shift schedule have different circadian rhythm timing than those of day workers. They are not only forced to stay awake and engaged in their daily work but also prone to develop insufficient sleep, because sleep after night shifts is shortened [51]. According to an analysis of 2570 adult subjects by Drake et al., 36%– 45% of those engaged in night work or shift work reported unbearable daytime sleepiness [52]. In a study by Scott et al., 600 out of 895 nurses reported that they had fallen asleep at the wheel at least once [53]. Scott et al. also found that 30 nurses reported driving in a sleepy state after shift work. Shift-work disorder (SWD) is a sleep disorder related to shift work, one that causes excessive sleepiness and/or complaints of nocturnal sleep [8]. The prevalence of SWD was 10.1% in day workers [54], 32.1% among night workers [54], 28.9% of nurses working on a three-shift rotation [55], 44.3% of those working on a two-shift rotation
5
[55], and 24.4% of nurses working with rapid-rotation schedules in Japan [56]. Our previous study of 3109 subjects engaged in shift work as public transportation drivers demonstrated that SWD was the main factor of EDS among them (Table 3). Notably, the strength of subjective sleepiness in drivers with SWD was higher than that of OSAS drivers [57]. In workers who met the criteria for SWD, there was a high incidence of accidents related with sleepiness [52], suggesting that early diagnosis and treatment of SWD is also important for ensuring traffic safety. However, SWD is often undiagnosed and untreated [58]. Because shift workers are no longer a small minority, and approximately 50% of professional drivers have irregular schedules or are engaged in nighttime driving [59], it is important to perform systematic SWD screenings to maintain both the physical and mental health of workers and to ensure traffic safety. As for the treatment of SWD, there are several available methods such as taking a short nap before or during night shifts, using bright light exposure and melatonin at appropriate times, and using drugs such as modafinil to stay awake as needed [60]. These methods were reported to be effective for maintaining wakefulness during shifts or for increasing the amount of nocturnal sleep [58]. However, no established study has investigated how these methods act to ensure the traffic safety of shift workers. 4. Sleepiness detection methods and accident countermeasures Because ocular variables (e.g., pupils, eye movement, and blinking) change with the level of sleepiness and can be measured without contact or restraint, several researchers have proposed methods for measuring drivers' sleepiness using ocular variables [61–65]. In a previous study, we investigated the detection capability of ocular variables for decreased vigilance or falling asleep while performing monotonous tasks that can easily induce sleepiness [66]. A cap-type head sensor and an eyetracking system (EMR-9; NAC Image Technology Inc., Tokyo, Japan) (Fig. 4) were used to record several ocular variables. Decreased blink frequency and pupil diameter, increased percentage of eyelid closure time (PERCLOS), and slow eye movement were observed as consecutive missed responses increased. Among these variables, PERCLOS was the most suitable for detecting missed responses and three or more consecutive missed responses. This result suggests that, among the ocular variables we assessed, PERCLOS can most effectively prevent error or accident caused by decreased vigilance while driving. Further study on the development of systems to alert drivers using this variable can be expected to prevent accidents due to sleepiness. As for countermeasures for drowsy driving, laboratory- and questionnaire-based epidemiological studies have demonstrated the effectiveness of napping and drinking coffee [67–69]. Taking a nap as a measure to counter sleepiness at the wheel is common among drivers between 46 and 64 years of age, those who have already experienced a sleep-related traffic accident, and those who have experienced severe sleepiness during driving [70]. A short nap is thought to be effective in
Table 2 Comparison of descriptive variables among the five groups with major hypersomnias. Komada et al., Sleep Medicine. 2008.
Behaviorally induced insufficient sleep syndrome Sleep apnea syndrome Idiopathic hypersomnia Narcolepsy Circadian rhythm sleep disorders
Mean age of initial visit
Mean age of symptoms
ESS score of the initial visit
BMI
Sleep length of weekday
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
30.2 45.1 31.4 31.0 27.7
7.3 12.1⁎⁎⁎ 9.0 13.3 8.1
28.6 – 19.2 17.2 18.9
7.5 – 7.3⁎⁎⁎ 7.5⁎⁎⁎ 6.4⁎⁎⁎
13.6 12.5 14.3 15.7 12.4
3.4 3.6⁎⁎ 3.0 3.0⁎⁎⁎ 3.7⁎
22.2 27.4 21.8 23.4 21.9
2.8 4.9⁎⁎⁎
5.5 6.1 6.3 6.4 7.8
0.8 1.0⁎⁎⁎ 1.1⁎⁎⁎ 1.3⁎⁎⁎ 2.3⁎⁎⁎
3.1 4.1⁎ 3.8
Results with post hoc test (compared with ISS).We exclude obstructive sleep apnea syndrome from the analysis of mean age of symptoms because the data for people with this syndrome in the population is unknown. ⁎⁎⁎ p b 0.0001. ⁎⁎ p b 0.01. ⁎ p b 0.05.
6
Y. Komada et al. / IATSS Research 37 (2013) 1–7
Table 3 The diagnoses of sleep disorders according to the International Classification of Sleep Disorders 2nd edition among drivers with subjective EDS (ESS ≥ 11). Asaoka et al., Journal of Occupational and Environmental Medicine. 2010.
Shift-work disorder Obstructive sleep apnea syndrome Behaviorally induced insufficient sleep syndrome Delayed sleep phase disorder Insomnia Idiopathic hypersomnia without long sleep time Periodic limb movement disorder Other Error in answering questionnaire Lost to follow-up Total
n
%
48 30 12 11 10 7 5 3 6 15 147
32.7 20.4 8.2 7.5 6.8 4.8 3.4 2.0 4.1 10.2 100.0
reducing sleepiness and maintaining the vigilance level. However, sleep inertia sometimes occurs after awakening from a short nap, and this could be a risk factor for accidents [71]. It was reported that a short nap with self-awakening was more effective in reducing sleepiness and sleep inertia than one with forced-awakening [71]. Another experimental study showed that sleep inertia after taking a nap during sleep deprivation can be prevented by hourly caffeine (0.3 mg/kg) intake [72]. Our study of about 4000 drivers demonstrated that 67.6% had experienced sleepiness while driving and 11.4% had fallen asleep at the wheel in the year preceding the investigation [73]. In that study, analysis of two groups—professional (about 700 subjects) and nonprofessional drivers (about 3300 subjects)—revealed that the rate of subjects experiencing traffic accidents caused by falling asleep in the last five years, and falling asleep at the wheel during the past year, was higher in professional drivers than in non-professional drivers (traffic accidents caused by falling asleep: 3.5% vs. 1.2%; falling asleep at the wheel: 17.8% vs. 10.1%, respectively). In addition, an analysis of measures taken to reduce sleepiness during driving revealed that the most frequently used method, used by more than 40% of subject drivers, both non-professional and professional, was “taking a rest.” Other measures included “chewing gum,” “opening a window,” and “drinking coffee,” all used by 30% of drivers; “napping” and “smoking,” used by 20% of drivers; and finally, “listening to the radio” and “talking with a passenger,” used by 10% of drivers. In that study, we also found that non-professional drivers are likely to take such measures when they feel sleepy or are in situations where prone to dozing off at the wheel. However, this tendency was not observed in professional drivers,
Fig. 4. Recordings using an eye-tracking system (EMR-9; NAC Image Technology Inc., Tokyo Japan). Abe et al., International Journal of Psychophysiology. 2011.
suggesting that they do not use naps as a countermeasure until they have experienced sleepiness-related traffic accidents. Undoubtedly, when sleepiness occurs during driving, drivers should take measure such as taking a break or drinking coffee, both of which have been reported to successfully reduce sleepiness and increase driving performance [74]. However, driving schedule constraints on professional drivers seem to make them less likely than non-professional drivers to take proactive measures to counter sleepiness while driving. It is therefore important to educate professional drivers and their employees about the mechanism of sleepiness-related vehicular accidents and the importance of strategies for coping with sleepiness. 5. Conclusion Sleepiness is a main factor responsible for traffic accidents caused by human error. People who sleep for fewer than 6 h have an increased risk of traffic accidents. Thus, the most essential thing to prevent traffic accidents due to sleepiness is ensuring that drivers get sufficient sleep at night. Of course, to prevent daytime sleepiness, it is important to maintain nocturnal sleep quality as well as an adequate amount of sleep. SAS is one of the most common and important sleep disorders, and makes nocturnal sleep shallow and fragmented. Patients affected with severe SAS may be especially likely to underestimate their own sleepiness. Considering that the risk of traffic accidents can be reduced close to that of healthy people by providing proper treatment, the early detection and treatment of SAS is desirable. Sleepiness-related accidents may have multiple causes. It is therefore important to address this matter from various approaches, including the maintenance of good sleep hygiene, measures to reduce sleepiness, and the prevention and treatment of sleep disorders. In addition, we want to emphasize the need to establish and maintain appropriate working conditions for drivers. References [1] J.A. Horne, L.A. Reyner, Sleep related vehicle accidents, BMJ 310 (1995) 565–567. [2] M.M. Ohayon, R.G. Priest, J. Zulley, S. Smirne, T. Paiva, Prevalence of narcolepsy symptomatology and diagnosis in the European general population, Neurology 58 (2002) 1826–1833. [3] X. Liu, M. Uchiyama, K. Kim, M. Okawa, K. Shibui, Y. Kudo, Y. Doi, M. Minowa, R. Ogihara, Sleep loss and daytime sleepiness in the general adult population of Japan, Psychiatry Research 93 (2000) 1–11. [4] NHK Broadcasting Culture Research Institute, NHK Data Book 2010 National Time Use SurveyNHK Publishing, Inc., Tokyo, 2011. [5] C. Hublin, J. Kaprio, M. Partinen, M. Koskenvuo, Insufficient sleep—a populationbased study in adults, Sleep 24 (2001) 392–400. [6] T. Ohida, A.M. Kamal, M. Uchiyama, K. Kim, S. Takemura, T. Sone, T. Ishii, The influence of lifestyle and health status factors on sleep loss among the Japanese general population, Sleep 24 (2001) 333–338. [7] H.P. Van Dongen, G. Maislin, J.M. Mullington, D.F. Dinges, The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation, Sleep 26 (2003) 117–126. [8] American Academy of Sleep Medicine, International Classification of Sleep Disorders: Diagnostic and Coding Manual, 2nd ed. American Academy of Sleep Medicine, Westchester, Illinois, 2005. [9] T. Abe, Y. Komada, Y. Nishida, K. Hayashida, K. Inoue, Short sleep duration and long spells of driving are associated with the occurrence of Japanese drivers' rearend collisions and single-car accidents, Journal of Sleep Research 19 (2010) 310–316. [10] T. Abe, Y. Komada, S. Asaoka, A. Ozaki, Y. Inoue, Questionnaire-based evidence of association between sleepiness while driving and motor vehicle crashes that are subjectively not caused by falling asleep, Sleep and Biological Rhythms 9 (2011) 134–143. [11] M.S. Aldrich, Automobile accidents in patients with sleep disorders, Sleep 12 (1989) 487–494. [12] T. Young, J. Blustein, L. Finn, M. Palta, Sleep-disordered breathing and motor vehicle accidents in a population-based sample of employed adults, Sleep 20 (1997) 608–613. [13] K. Kim, M. Uchiyama, M. Okawa, X. Liu, R. Ogihara, An epidemiological study of insomnia among the Japanese general population, Sleep 23 (2000) 41–47. [14] J.C. Souza, L.A. Magna, R. Reimao, Insomnia and hypnotic use in Campo Grande general population, Brazil, Arquivos de Neuro-Psiquiatria 60 (2002) 702–707. [15] M.M. Ohayon, Epidemiology of insomnia: what we know and what we still need to learn, Sleep Medicine Reviews 6 (2002) 97–111. [16] C.L. Drake, T. Roehrs, T. Roth, Insomnia causes, consequences, and therapeutics: an overview, Depression and Anxiety 18 (2003) 163–176.
Y. Komada et al. / IATSS Research 37 (2013) 1–7 [17] M.M. Ohayon, Epidemiological study on insomnia in the general population, Sleep 19 (1996) S7–S15. [18] S. Englert, M. Linden, Differences in self-reported sleep complaints in elderly persons living in the community who do or do not take sleep medication, The Journal of Clinical Psychiatry 59 (1998) 137–144. [19] Y. Komada, T. Shiomi, K. Mishima, Y. Inoue, Associated factors for drowsy driving among licenced driver, Japanese Journal of Public Health 57 (2010) 1066–1074. [20] K. Komada, T. Nomura, M. Kusumi, K. Nakashima, I. Okajima, T. Sasai, Y. Inoue, Correlations among insomnia symptoms, sleep medication use and depressive symptoms, Psychiatry and Clinical Neurosciences 65 (2011) 20–29. [21] D.E. Moul, E.A. Nofzinger, P.A. Pilkonis, P.R. Houck, J.M. Miewald, D.J. Buysse, Symptom reports in severe chronic insomnia, Sleep 25 (2002) 553–563. [22] E. Fortier-Brochu, S. Beaulieu-Bonneau, H. Ivers, C.M. Morin, Relations between sleep, fatigue, and health-related quality of life in individuals with insomnia, Journal of Psychosomatic Research 69 (2010) 475–483. [23] J.D. Edinger, M.K. Means, C.E. Carney, A.D. Krystal, Psychomotor performance deficits and their relation to prior nights' sleep among individuals with primary insomnia, Sleep 31 (2008) 599–607. [24] J.A. Shekleton, N.L. Rogers, S.M. Rajaratnam, Searching for the daytime impairments of primary insomnia, Sleep Medicine Reviews 14 (2010) 47–60. [25] E. Altena, Y.D. Van Der Werf, R.L. Strijers, E.J. Van Someren, Sleep loss affects vigilance: effects of chronic insomnia and sleep therapy, Journal of Sleep Research 17 (2008) 335–343. [26] J. Menzin, K.M. Lang, P. Levy, E. Levy, A general model of the effects of sleep medications on the risk and cost of motor vehicle accidents and its application to France, PharmacoEconomics 19 (2001) 69–78. [27] M. Partinen, K. Hirvonen, C. Hublin, M. Halavaara, H. Hiltunen, Effects of aftermidnight intake of zolpidem and temazepam on driving ability in women with non-organic insomnia, Sleep Medicine 4 (2003) 553–561. [28] C.F. George, Sleep apnea, alertness, and motor vehicle crashes, American Journal of Respiratory and Critical Care Medicine 176 (2007) 954–956. [29] C.F. George, P.W. Nickerson, P.J. Hanly, T.W. Millar, M.H. Kryger, Sleep apnoea patients have more automobile accidents, Lancet 330 (1987) 447. [30] S. Tregear, J. Reston, K. Schoelles, B. Phillips, Obstructive sleep apnea and risk of motor vehicle crash: systematic review and meta-analysis, Journal of Clinical Sleep Medicine 5 (2009) 573–581. [31] A. Sassani, L.J. Findley, M. Kryger, E. Goldlust, C. George, T.M. Davidson, Reducing motor-vehicle collisions, costs, and fatalities by treating obstructive sleep apnea syndrome, Sleep 27 (2004) 453–458. [32] Y. Komada, Y. Nishida, K. Namba, T. Abe, S. Tsuiki, Y. Inoue, Elevated risk of motor vehicle accident for male drivers with obstructive sleep apnea syndrome in the Tokyo metropolitan area, The Tohoku Journal of Experimental Medicine 219 (2009) 11–16. [33] S. Tregear, J. Reston, K. Schoelles, B. Phillips, Continuous positive airway pressure reduces risk of motor vehicle crash among drivers with obstructive sleep apnea: systematic review and meta-analysis, Sleep 33 (2010) 1373–1380. [34] M. Orth, H.W. Duchna, M. Leidag, W. Widdig, K. Rasche, T.T. Bauer, J.W. Walther, J. de Zeeuw, J.P. Malin, G. Schultze-Werninghaus, S. Kotterba, Driving simulator and neuropsychological testing in OSAS before and under CPAP therapy, The European Respiratory Journal 26 (2005) 898–903. [35] T. Young, P.E. Peppard, D.J. Gottlieb, Epidemiology of obstructive sleep apnea: a population health perspective, American Journal of Respiratory and Critical Care Medicine 165 (2002) 1217–1239. [36] R.L. Ellen, S.C. Marshall, M. Palayew, F.J. Molnar, K.G. Wilson, M. Man-Son-Hing, Systematic review of motor vehicle crash risk in persons with sleep apnea, Journal of Clinical Sleep Medicine 2 (2006) 193–200. [37] A.T. Mulgrew, G. Nasvadi, A. Butt, R. Cheema, N. Fox, J.A. Fleetham, C.F. Ryan, P. Cooper, N.T. Ayas, Risk and severity of motor vehicle crashes in patients with obstructive sleep apnoea/hypopnoea, Thorax 63 (2008) 536–541. [38] G. Maycock, Sleepiness and driving: the experience of UK car drivers, Journal of Sleep Research 5 (1997) 229–237. [39] N.B. Powell, K.B. Schechtman, R.W. Riley, C. Guilleminault, R.P. Chiang, E.M. Weaver, Sleepy driver near-misses may predict accident risks, Sleep 30 (2007) 331–342. [40] S. Garbarino, L. Nobili, M. Beelke, F. De Carli, F. Ferrillo, The contributing role of sleepiness in highway vehicle accidents, Sleep 24 (2001) 203–206. [41] L. Findley, M. Unverzagt, R. Guchu, M. Fabrizio, J. Buckner, P. Suratt, Vigilance and automobile accidents in patients with sleep apnea or narcolepsy, Chest 108 (1995) 619–624. [42] C.F. George, A.C. Boudreau, A. Smiley, Comparison of simulated driving performance in narcolepsy and sleep apnea patients, Sleep 19 (1996) 711–717. [43] A. Ozaki, Y. Inoue, T. Nakajima, K. Hayashida, M. Honda, Y. Komada, K. Takahashi, Health-related quality of life among drug-naïve patients with narcolepsy with cataplexy, narcolepsy without cataplexy, and idiopathic hypersomnia without long sleep time, Journal of Clinical Sleep Medicine 4 (2008) 572–578. [44] T. Roehrs, F. Zorick, J. Sicklesteel, R. Wittig, T. Roth, Excessive daytime sleepiness associated with insufficient sleep, Sleep 6 (1983) 319–325. [45] Y. Komada, Y. Inoue, K. Hayashida, T. Nakajima, M. Honda, K. Takahashi, Clinical significance and correlates of behaviorally induced insufficient sleep syndrome, Sleep Medicine 9 (2008) 851–856. [46] M.S. Aldrich, Insufficient sleep syndrome, in: M. Billiard (Ed.), Sleep: Physiology, Investigations, and Medicine, Kluwer Academic/Plenum Publishers, New York, 2003, pp. 341–346.
7
[47] J.E. Broman, L.G. Lundh, J. Hetta, Insufficient sleep in general population, Neurophysiologie Clinique 26 (1996) 30–39. [48] T. Roehrs, V. Timms, A. Zwyghuizen-Doorenbos, R. Buzenski, T. Roth, Polysomnographic, performance, and personality differences of sleepy and alert normals, Sleep 13 (1990) 395–402. [49] P.M. Turkington, M. Sircar, V. Allgar, M.W. Elliot, Relationship between obstructive sleep apnoea, driving simulator performance, and risk of road traffic accidents, Thorax 56 (2001) 800–805. [50] Ministry of Health, Labour and Welfare, Annual Health, Labour and Welfare Report 2007, 2007. [51] T. Åkerstedt, Shift work and disturbed sleep/wakefulness, Occupational Medicine 53 (2003) 89–94. [52] C.L. Drake, T. Roehrs, G. Richardson, J.K. Walsh, T. Roth, Shift work sleep disorder: prevalence and consequences beyond that of symptomatic day workers, Sleep 27 (2004) 1453–1462. [53] L.D. Scott, W.T. Hwang, A.E. Rogers, T. Nysse, G.E. Dean, D.F. Dinges, The relationship between nurse work schedules, sleep duration, and drowsy driving, Sleep 30 (2007) 1801–1807. [54] L. Di Milia, S. Waage, S. Pallesen, B. Bjorvatn, Shift work disorder in a random population sample-prevalence and comorbidities, PloS One 8 (2013) e55306. [55] E. Flo, S. Pallesen, N. Magerøy, B.E. Moen, J. Grønli, I. Hilde Nordhus, B. Bjorvatn, Shift work disorder in nurses-assessment, prevalence and related health problems, PloS One 7 (2012) e33981. [56] S. Asaoka, S. Aritake, Y. Komada, A. Ozaki, Y. Odagiri, S. Inoue, T. Shimomitsu, Y. Inoue, Factors associated with shift work disorder in nurses working with rapid-rotation schedules in Japan: the nurses' sleep health project, Chronobiology International 30 (2013) 628–636. [57] S. Asaoka, K. Namba, S. Tsuiki, Y. Komada, Y. Inoue, Excessive daytime sleepiness among Japanese public transportation drivers engaged in shiftwork, Journal of Occupational and Environmental Medicine 52 (2010) 813–818. [58] J.R. Schwartz, T. Roth, Shift work sleep disorder: burden of illness and approaches to management, Drugs 66 (2006) 2357–2370. [59] A.I. Pack, D.F. Dinges, G. Maislin, A study of prevalence of sleep apnea among commercial truck drivers, Federal Motor Carrier Safety Administration Publication No DOT-RT-02-030 Washington, DC, 2002. [60] R.L. Sack, D. Auckley, R.R. Auger, M.A. Carskadon, K.P. Jr, M.V. Vitiello Wright, I.V. Zhdanova, Circadian rhythm sleep disorders: part I, basic principles, shift work and jet lag disorders: An American Academy of Sleep Medicine review, Sleep 30 (2007) 1460–1483. [61] T. Åkerstedt, M. Ingre, G. Kecklund, A. Anund, D. Sandberg, M. Wahde, P. Philip, P. Kronberg, Reaction of sleepiness indicators to partial sleep deprivation, time of day and time on task in a driving simulator: the DROWSI project, Journal of Sleep Research 19 (2010) 298–309. [62] D.F. Dinges, M. Mallis, G. Maislin, J.W. Powell, Evaluation of Techniques for Ocular Measurement as an Index of Fatigue and as the Basis for Alertness Management, U.S. Department of Transportation, National Highway Traffic Safety Administration, 1998. [63] M.W. Johns, A. Tucker, R. Chapman, K. Crowley, N. Michael, Monitoring eye and eyelid movements by infrared reflectance oculography to measure drowsiness in drivers, Somnologie 11 (2007) 234–242. [64] D. Shin, H. Sakai, Y. Uchiyama, Slow eye movement detection can prevent sleep-related accidents effectively in a simulated driving task, Journal of Sleep Research 20 (2011) 416–424. [65] A. Ueno, S. Kokubun, Y. Uchikawa, A prototype real-time system for assessing vigilance levels and for alerting the subject with sound stimulation, International Journal of Assistive Robotics and Mechatronics 8 (2007) 19–27. [66] T. Abe, T. Nonomura, Y. Komada, S. Asaoka, T. Sasai, A. Ueno, Y. Inoue, Detecting deteriorated vigilance using percentage of eyelid closure time during behavioral maintenance of wakefulness tests, International Journal of Psychophysiology 82 (2011) 269–274. [67] J. Horne, L. Reyner, Vehicle accidents related to sleep: a review, Occupational and Environmental Medicine 56 (1999) 289–294. [68] P. Philip, J. Taillard, N. Moore, S. Delord, C. Valtat, P. Sagaspe, B. Bioulac, The effects of coffee and napping on nighttime highway driving: a randomized trial, Annals of Internal Medicine 144 (2006) 785–791. [69] P. Sagaspe, J. Taillard, G. Chaumet, N. Moore, B. Bioulac, P. Philip, Aging and nocturnal driving: better with coffee or a nap? A randomized study, Sleep 30 (2007) 1808–1813. [70] A. Anund, G. Kecklund, B. Peters, T. Åkerstedt, Driver sleepiness and individual differences in preferences for countermeasures, Journal of Sleep Research 17 (2008) 16–22. [71] K. Kaida, H. Nittono, M. Hayashi, T. Hori, Effects of self-awakening on sleep structure of a daytime short nap and on subsequent arousal levels, Perceptual and Motor Skills 97 (2003) 1073–1084. [72] H.P. Van Dongen, N.J. Price, J.M. Mullington, M.P. Szuba, S.C. Kapoor, D.F. Dinges, Caffeine eliminates psychomotor vigilance deficits from sleep inertia, Sleep 24 (2001) 813–819. [73] S. Asaoka, T. Abe, Y. Komada, Y. Inoue, The factors associated with preferences for napping and drinking coffee as countermeasures for sleepiness at the wheel among Japanese drivers, Sleep Medicine 13 (2012) 354–361. [74] S.V. Heatherle, Caffeine withdrawal, sleepiness, and driving performance: what does the research really tell us? Nutritional Neuroscience 14 (2011) 89–95.