Delayed school start times and adolescent health

Chapter 33

Delayed school start times and adolescent health Aaron T. Bergera, Rachel Widomea, Wendy M. Troxelb a

Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN, United States, bRAND Corporation, Santa Monica, CA, United States

Adolescence is a development period characterized by dramatic changes in neurobiological, physical and socioemotional development as well as changes in sleep-wake patterns. Most adolescents should optimally sleep a minimum of 8–9.5 h per night [1, 2]. However, the majority fall substantially short of that mark as national surveillance shows that only 7% of US adolescents report getting at least 8.5 h of sleep on school nights [3]. Between ages 12 and 18, the probability of getting at least 7 h of sleep per night drops by about half [4]. The magnitude of the short sleep duration epidemic among adolescents is even larger than what we have observed in adults, with US high school-aged youth being more than twice as likely to report getting insufficient sleep compared to adults [2]. Additionally, there are sleep disparities among adolescents, with girls, non-whites, and those from lower socioeconomic status backgrounds, being more likely to report short sleep duration compared to other groups [4]. A particularly worrisome trend is the secular decline in adolescent sleep over the past 20 years, a trend that has been called a “great sleep recession” [4]. A variety of social and environmental factors pose significant obstacles to sufficient sleep for most US adolescents [5–9], including social pressures to stay up late, bright light from screens at and after bedtime, after school homework and employment, and caffeine use, to name a few. Even in the absence of these social and environmental contexts, there are powerful, hardwired biological factors that push teenagers toward later bedtimes and delayed wake-up times [10, 11]. The circadian biological clock and sleep/wake homeostasis are two body systems that regulate sleep [12]. Early in puberty, in most adolescents, there is a neurobiological change to children's circadian clocks that results in a twoto three-hour delay in the release of the sleep-promoting hormone, melatonin. This circadian timing persists through adolescence [13], and means that the time adolescents naturally fall asleep is deferred to a later hour. After this shift it is challenging, even for an adolescent who tries to get to Sleep and Health. https://doi.org/10.1016/B978-0-12-815373-4.00033-2 © 2019 Elsevier Inc. All rights reserved.

bed at an early hour, to fall asleep prior to 11 p.m. and it follows that they will struggle to wake before 8 a.m. [11]. Additionally, “sleep drive,” which accumulates over the waking hours and diminishes wakefulness as the day progresses, builds slower once children reach their teen years [14]. As adolescents get older, bedtime is delayed on both school and non-school days [5]. This adolescent sleep timing shift has been observed both in the US and around the world, adding confirmatory evidence to this delay of sleep onset being a largely biological, and not purely social, normative or cultural phenomenon [5, 11, 15]. Meanwhile, contrary to popular belief, adolescents require just as much sleep as they did when they were a few years younger [11] with 9.25 h of nightly sleep being considered optimal through the teen years [16]. Early school start times are perhaps the most potent and salient environmental constraint on adolescent sleep [1, 17, 18]. Although delayed sleep onset has many biological and social causes, delayed sleep onset does not necessarily result in truncated sleep duration, unless schedules dictate an untenable wake-up time. Unfortunately, this is nearly always the case in the US, where high schools, almost without exception, tend to start very early [18], leading adolescents to need to wake before they have finished sleeping. In order to meet the biological sleep needs of adolescents, over two dozen medical organizations, including the American Academy of Pediatrics and the Centers for Disease Control and Prevention, have recommended that middle and high schools start at 8:00 a.m., 8:30 a.m., or later [19]. Numerous examples in school districts from across the country have shown that high schools can feasibly shift their start times to 8:30 a.m. or later [20]. Both cross-sectional [21] and longitudinal [22–24] evaluations of start time differences show that later start times allows teens to get more sleep, with each one-hour start time delay associated with 30–90 additional minutes of school night sleep duration. Yet <18% of US middle and high schools start at or after 8:30 a.m. and 447

448  PART | VIII  Sleep Health in Children and Adolescents

42% start at 8 a.m. or earlier [18, 25], start times which appear to most severely curtail sleep [26]. In this chapter we aim to summarize the documented effects of delaying school start time on adolescent health. Given the strong evidence linking short sleep duration with numerous physical and mental health risks (covered in depth in the preceding chapters), delaying start times could be an effective population-level strategy to promote sleep and physical and mental health in adolescents. Our review covers those health outcomes that have been included in peer-reviewed literature, in relation to a K-12 school start time contrast (e.g. studies that have compared two or more schools with different start times, or one school before and after a start time change). We review the effects of school start times on sleep duration, academic outcomes and truancy, mental health and risky behavior, and unintentional injury. We conclude by discussing the obstacles communities face when delaying school start times.

DELAYING HIGH SCHOOL START TIME IMPROVES SLEEP Delaying school start time is a population-level intervention with the potential to affect sleep duration and sleep-related

health during adolescence, a critical developmental period. Studies that have evaluated whether school start times are associated with more or better-quality sleep have overwhelmingly concluded that later school start times are associated with significantly longer school-night sleep duration [27, 28]. Later school start times are associated with longer school-night sleep duration in all eight studies eligible for inclusion in a recent Cochrane review, and in 29 of 31 studies included in another recent systematic review [27, 28]. Fig. 33.1 illustrates the distributions of school-night sleep duration for students at eight US high schools, with start times ranging from 7:35 a.m. to 8:55 a.m. [24]. Compared to students in the earliest-starting school, the entire distribution of sleep duration at later-starting schools shifts progressively toward longer sleep duration. Notably, approximately 10% of US high schools start before the earliest-starting high school in this sample [18]. Some have questioned whether a delayed school start time might be counterproductive, and only serve to delay bedtimes such that sleep duration is not lengthened. Contrary to this belief, most of the available evidence has shown that later school start time leads to longer sleep duration because adolescent bedtimes are stable and likely not influenced much by artificially imposed wake-up times.

0.4

0.3 Start time

density

7:35am 8:00am 8:05am

0.2

8:20am 8:35am 8:55am 0.1

0.0 3

4

5

6 7 8 9 School night sleep duration (hours)

10

11

12

Data: Wahistrom (2014) FIG. 33.1  Wahlstrom [24] collected self-reported sleep duration in eight US high schools with a range of start times. At later-starting schools, the entire distribution of school-night sleep duration is progressively shifted to the right, toward greater sleep.

Delayed school start times and adolescent health Chapter | 33  449

In before-after studies of school start time changes, students typically maintain the same bedtimes after starting later that they had when their school started early [21, 29, 30], although one study showed that bedtimes actually shifted earlier when schools started later [22]. One recent crosssectional study showed that students had modestly later bedtimes at schools with later start times; however this study did not compare bedtimes before and after start time changes [26]. The stability of adolescent bedtimes across various school start times, early and late, is yet another piece of evidence reinforcing adolescents' circadian clocks are biologically set and rather inflexible.

ACADEMIC ACHIEVEMENT, ATTENTION, AND TRUANCY Students who do not get enough sleep have more difficulty concentrating in class, and are less likely to graduate high school or college than their better-rested peers [31]. Many sleepy adolescents find themselves unable to stay awake even while they are in class. A 2006 survey by the National Sleep Foundation found that 28% of high school students report falling asleep in school at least once a week [32]. Among high school students in a nationally representative survey, each additional hour of sleep was associated with 16% lower probability of attention problems in school, 15% lower probability of trouble completing homework, and a grade point average (GPA) increase of 0.2 points [31]. Moreover, when those students were followed through early adulthood, each additional hour of sleep was associated with 13% greater probability of graduating high school and a nearly 10% increase in probability of attending college [31]. Because delaying high school start time is recognized as an important strategy for promoting health sleep duration [1, 19], researchers have worked to understand if later start times will improve adolescents' academic achievement. However, there are challenges in interpreting the effect of school start time on academic performance due to the nature of letter grades and standardized tests. Grade point averages may reflect the difficulty of a student's class schedule or the whims of a teacher, while standardized college entrance exams are not taken universally and may reflect only the population who intends to go to college [27]. Additionally, students who struggle in school due to sleepiness might opt for, or be tracked into, less difficult courses. Studies that have considered the effect of a one-hour school start time delay on standardized test scores have had mixed results [33, 34]. Hinrichs compared ACT test scores of high school students in the Minneapolis and Saint Paul, Minnesota, public school districts before and after a start time delay in Minneapolis schools [33]. Hinrichs found no significant effects of school start time on ACT scores (β = −0.024, 95% confidence interval [CI] −0.23 to 0.18).

In addition, Hinrichs conducted cross-sectional comparisons of high school student scores on the Kansas Reading Assessment by school start time. As with ACT scores, there was no association between school start time and reading score (β = 0.95, 95% CI −2.67 to 4.58). Meanwhile, Edwards conducted a similar study of the math and reading exam scores of middle school students in neighboring communities in North Carolina, one of which delayed its school start time during the study period [34]. Edwards found that students whose school was delayed by 1 h experienced a 1.8% point improvement in math scores (95% CI 1.19–2.37) and 0.98-point improvement in reading scores (95% CI 0.28–1.68) [34]. A few studies have also considered the effect of school start time on students' letter grades. Wahlstrom conducted a pre-post study of student grades before and after start time delays in six school districts [24]. In four districts, the combined pre-post change in all core courses (mathematics, science, social studies, and/or English), and in two districts the core course grades were available for individual analysis. There was significant improvement in grades in three of the four school districts where all courses were analyzed collectively, and no significant difference in one school. In the two districts in which core course grades were analyzed separately, some courses had significant increases and others had significant decreases (although Wahlstrom did not report which specific courses showed letter grade improvements or setbacks) [24]. A considerable problem in causal inference for studies of school start times is that, due to the logistical complexity and multiple competing interests in setting school start times, researchers may never be able to randomize the start times that students receive. One noteworthy study, among first-semester freshmen at the US Air Force Academy (USAFA), was able to overcome that limitation [35]. Because the service academy randomly assigned students' academic schedules, including start time, course, and instructor, this study effectively recreates a randomized trial. The study found that when students are randomly assigned to take a class before 8:00 a.m., their academic performance in their first hour class was significantly worse than those whose first hour class was assigned to 8:00 a.m. or later. In addition, having an early start to the academic day reduced performance throughout the entire day [35]. This study provides the highest-quality evidence that later school start times may play a causal role in improving academic outcomes. While the students at the USAFA are slightly older than high school students, most first-semester freshmen students are still biologically adolescents [35]. The average age of freshman cadets was not reported, but USAFA cadets are required to be between 17 and 23 years old in the year they enter [36], and 33% of all USAFA students are ages 18–19 years old, suggesting that a substantial majority of freshmen enter at age 18 [37].

450  PART | VIII  Sleep Health in Children and Adolescents

Later school start times may improve learning and academic achievement by reducing sleepiness during the school day. Indeed, in a recent review of the school start time literature, 10 of the 12 studies that measured sleepiness found significantly less sleepiness in schools with later start times [27]. For example, Danner and Phillips used the Epworth Sleepiness Scale, a validated measure of daytime sleepiness [38], to measure changes in daytime sleepiness before and after a start time change in Kentucky [30]. Mean sleepiness declined from 8.9 to 8.2 (P < 0.001). Other longitudinal studies have also found lower levels of sleepiness following delays in start times [22, 23]. Reduced sleepiness may also improve academic achievement by facilitating improved concentration and attention to school and afterschool homework. An Israeli study used two different assessments to compare sustained attention in middle school students whose school start time was experimentally delayed by 1 h, compared to a group with consistently early start times [39]. The delayed start time group has a significantly better attention level, and made significantly fewer errors, than the early start time group. Oversleeping students may be absent for all or part of a school day due to early start times. Edwards estimated that students at schools starting 1 h later average 1.3 fewer absences per year, with a median of five absences per year [34]. Wahlstrom identified the attendance of students who change schools more frequently as experiencing a particularly large benefit from later school start time [21]. While school attendance for continuously enrolled students was consistently high before and after a start time change, attendance for students who had changed schools during high school improved significantly following a start time delay, from 72% to 76% for 9th grade students, and from 73.7% to 77.5% for 10th and 11th grade students [21]. This suggests that the largest gains in school attendance may be observed for the students at highest risk of absenteeism. Combined with reduced daytime sleepiness and better attention to school and homework, improved attendance may account for the increased academic achievement observed in later starting schools.

MENTAL HEALTH AND RISKY BEHAVIOR Adolescence is known to be a highly vulnerable period for the onset of mental health issues and substance use disorders. For instance, 50% of all lifetime cases of depression begin by age 14 [40]. Furthermore, risky behavior in adolescence, including alcohol, tobacco and other substance use and risky sexual behavior, are a cause of substantial morbidity, mortality, and social problems for youth and can lead to chronic lifelong health issues [41]. Thus, adolescence may be a critical period for preventing the lasting consequences of mental health and substance use-related morbidity and improving sleep health may be a key tactic in the armament of psychological and behavioral health promotion strategies.

Sleep loss and sleep disorders are commonly associated with reduced mental well-being and risky behaviors. Adults with psychiatric mood disorders such as major depression and post-traumatic stress disorder commonly experience sleep disturbances [42], inadequate or poor-quality sleep also co-occur with symptoms of depression [43], hopelessness and suicidal thoughts and attempts [43–45], irritability and impaired emotional regulation [46]. Sleep problems in childhood and adolescence may predict future mental health problems [47, 48] and even suicide [48]. Experimental studies of sleep restriction provide further causal support for a role of sleep disturbance in contributing to mental health problems [46, 49, 50]. Experimentally sleep restricted adolescents exhibit higher levels of anxiety, anger, fatigue and confusion compared to periods of sleep extension [46]. Additionally, experimental sleep deprivation has been associated with reduced positive affect [49, 50], and increased negative affect [49] in adolescents, which may increase adolescent vulnerability to depression. The role played by REM sleep in emotional processing [42] may explain these changes in affective response. When adolescents are woken prematurely they are deprived of rapid eye movement (REM) sleep (the stage of sleep known to be associated with emotional processing). This deficit hampers recovery from emotional conflict, and reduces emotional control by increasing reactivity to negative emotional stimuli [42]. Insufficient sleep may contribute generally to increased adolescent risk behaviors by diminishing teen's executive cognitive functioning and emotional regulation [51]. Early school start times cause many adolescents to live in a state of constant “circadian misalignment” due to the discrepancy between the school-imposed schedule and their own internal clock. Tired from the week, adolescents will sleep dramatically more hours on weekends to make up for school day sleep loss. Differences in weekend and weekday sleep hours have been associated with regulation of reward processing [52, 53] which can manifest as increased sensationseeking and diminished regulatory control [51, 54]. Sleep problems, including insomnia, short sleep duration, and inconsistencies in weekend versus weekday sleep, are associated cross-sectionally and longitudinally with increased use of alcohol, marijuana, and other drugs in adolescent samples [43, 45]. Although much literature has been published on the associations between sleep and mental health in adolescence, comparatively little work has been done to identify the psychological effects of delayed school start time [55]. We recently conducted a recent systematic review of literature on school start time and psychological health, including substance use. We identified eight eligible studies conducted in the past 20 years. The most commonly studied outcome, symptoms of depression and anxiety, was assessed in four of the studies [21–23, 56]. Positive and negative affect or

Delayed school start times and adolescent health Chapter | 33  451

attitudes were included in two more studies [57, 58], and two other studies included nonspecific measures of mental health [59, 60]. In both cross-sectional [21, 56] and longitudinal studies [22, 23], later school start time is consistently associated with fewer symptoms of depression and anxiety. One additional longitudinal study, with a control group, found that school start time was associated with improved general mental health and reduced psychologically-relevant behavior problems, such as emotional problems and hyperactivity/inattention [60]. Although both studies assessing the effect of school start time on positive and negative affect [57, 58] and one of the two studies of general mental health [59] did not find significant differences between earlier and later-starting schools, these studies were of short, 15-min differences in start times, a school with a late start on only 1 day of the week, and a highly unusual situation where a school was hosted during afternoon hours in another school building due to a fire. The highest quality studies uniformly found that later school start times are associated with better mental health in adolescents [22, 23, 60]. Notably lacking from the literature were studies of the impact of later start times on substance use or other risk-taking behaviors.

UNINTENTIONAL INJURY Sleep-deprived adolescents are more likely to be involved in car crashes, work-related injuries, and sports injuries [61]. High school students who get 7 h or of sleep or less each night are more likely to take risks that can lead to serious injury or death, such as failing to wear bike helmets and seat belts, drinking and driving or riding with a drunk driver, and texting while driving, compared to students who get 9 or more hours of sleep [61]. Being in a car crash is the leading cause of death for US adolescents, resulting in nearly 4000 teen deaths in the US every year [62]. Nationally, onefifth of fatal car crashes between 2009 and 2013 involved a drowsy driver [63]. Half of drowsy driving crashes involve a driver aged 25 or younger [64]. By addressing widespread chronic sleep shortages among adolescents, delaying school start times has a clear link to reducing adolescent injuries and fatalities. Several studies have analyzed the effect of school start time on car crash rates [24, 30, 65, 66]. One longitudinal study compared car crash rates for 17- and 18-year old drivers in a Kentucky school district to those in the state as a whole over the two years before and two years after a onehour start time delay. Teens in the county with delayed start times had a 16.5% reduction in car crash rate over the study period, while teen crashes in the rest of the state increased by 7.8% [30]. Two cross-sectional studies compared crash rates for high school-aged drivers in adjacent communities in central [66] and eastern Virginia [65] with 85-min and 75- to 80-min start time differences, respectively. In each comparison, teen drivers in the communities with later start

times were significantly less likely to be in crashes. As predicted, the teen crash peaks occurred during high school commute times in both communities, and teen drivers in the central Virginia community with earlier starting times were more likely to be in crashes where the car veered off the road to the right, a commonly sleep-related type of crash [66]. Finally, Wahlstrom compared the number of crashes involving 16- to 18-year old drivers in four communities before and after a start time delay [24]. She found that there were fewer adolescent-involved crashes in three of the four communities following a start time delay, while one community had a slight increase in crashes after a start time delay. However, because the communities were not compared to a reference population, it is not possible to say if the observed trends were unique to communities in which start time was delayed. Lengthening sleep duration could plausibly reduce these types of injuries by improving concentration, attention, and reaction time, and reducing fatigue and adolescent risk taking. For example, a Norwegian study compared reaction times among students whose start time is delayed one day of the week (N = 33), to high school students with consistently early start times (N = 45) [57]. Compared to the consistently early start students, students had significantly fewer reaction time lapses (response delays of over 500 milliseconds) and faster average reaction times, on the late start day. These improvements in reaction time could reduce the risk of multiple types of injury. However, we are aware of no research to date assessing the effect of school start time on other types of accidental injury, including occupational and sports injuries. Another way school start times could be used to reduce the risk of child pedestrian injury is by staggering school start times with periods of high motor vehicle traffic to reduce exposure to traffic [67]. Future research is needed to identify what effect school start time may have on these and other injuries.

CONCLUSIONS The evidence, which is based on pragmatic observational studies, some of which were natural experiment evaluations, suggests that delaying school start times can promote adolescent sleep and that this can have far reaching effects on healthy youth development. Numerous studies have overwhelmingly demonstrated that adolescents at later-starting schools are more likely get a healthy amount of sleep than their peers at earlier-starting schools. Limited evidence suggests that students at later-starting schools may learn more, and at worst perform no worse than their peers at earlier-starting schools, while an early start may hamper performance throughout the entire school day. There is also limited, but consistent, evidence that later school start times benefit both mental health and physical safety. Students starting school later demonstrate fewer symptoms of ­anxiety

452  PART | VIII  Sleep Health in Children and Adolescents

and depression and fewer behavioral problems. The risk of an adolescent being involved in a car crash appears to be reduced in communities with later-starting schools, possibly because or reduced sleepiness and improved reaction time among better-rested teens. Given the consistency of these findings, with most studies showing clear benefits of later start times for adolescents and the absence of any studies showing harms for adolescents, it is striking that <20% of US middle and high schools start at 8:30 a.m. or later [18]. Although an increasing number of schools have made the change toward later start times or are currently in the process of considering the issue, there are many logistical challenges that deter school districts from making such a change, despite the robust evidence in support. Primary areas of concern include the potential impact on elementary school students (particularly if the schedules are “flipped” with elementary schools starting first and middle/high schools starting later to accommodate bussing), the impact on sports/extracurricular activities, and the impact on before or after-school childcare. Underlying many of these concerns is also a concern about the potential cost implications to school districts—a genuine concern in light of increasingly tightening school budgets. Countering this, however, the RAND Corporation recently published the first comprehensive investigation of the potential economic costs and benefits of a hypothetical state-wide shift in school start times to 8:30 a.m. or later across the US [68]. The study found that, even after just 2 years of such a policy change, the US economy would see an $8.6 billion dollar gain, which would already outweigh the costs per student from delaying school start times to 8.30 a.m. The study projected even larger gains over a more protracted (e.g., 10-year) period of time, with benefits accrued through the improvement in academic outcomes and subsequent lifetime earnings of well-rested students as well as a reduction in adolescent drowsy driving motor vehicle crashes. There are still important avenues for inquiry and a need to gain additional broad insight on the impacts of the timing of school days, as far as health and social impacts both in adolescence and later in the life course. In particular, there is a critical need for longitudinal studies with longer term follow-up periods, as many potential benefits of later start times are likely to manifest over a longer period of time. Further, there is a need to study the potential impact of start times changes on other members of the community, including parents, teachers, and elementary school students. Additionally, there is a need to increase both the resolution the data on this topic via more objective measures as well as conduct research that would strengthen causal inference in this area. For this, innovative natural experiment evaluations are perhaps the best option given that randomizing schools to start time is highly infeasible. Strengthening the scientific base and disseminating such evidence to school districts and policy-makers is critical because school start

times are likely one of the most readily modifiable major determinants of adolescent sleep and this relatively straightforward intervention can reach youth from various backgrounds.

REFERENCES [1] American Academy of Pediatrics. School start times for adolescents. Pediatrics 2014;134(3):642–9. [Internet]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/25156998%5Cnhttp://pediatrics.aappublications.org/cgi/doi/10.1542/peds.2014-1697. [2] US Department of Health and Human Services. Healthy people 2020 sleep health objectives [Internet]. [cited 2017 Mar 20]. Available from: https://www.healthypeople.gov/2020/topics-objectives/topic/ sleep-health/objectives?topicId=38. [3] Eaton  DK, LR  MK-E, Lowry  R, Perry  GS, Presley-Cantrell  L, Croft  JB. Prevalence of insufficient, borderline, and optimal hours of sleep among high school students—United States, 2007. J Adolesc Health 2010;46(4):399–401. [Internet]. Elsevier Inc; Available from: https://doi.org/10.1016/j.jadohealth.2009.10.011. [4] Keyes  KM, Maslowsky  J, Hamilton  A, Schulenberg  J. The great sleep recession: changes in sleep duration among US adolescents, 1991–2012. Pediatrics 2015;135(3):460–8. [Internet].Available from: http://www.ncbi.nlm.nih.gov/pubmed/25687142%5Cnhttp://www. pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4338325. [5] Millman RP, Working Group on Sleepiness in Adolescents/Young Adults, AAP Committee on Adolescence. Excessive sleepiness in adolescents and young adults: causes, consequences, and treatment strategies. Pediatrics 2005;115(6):1774–86. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS& PAGE=reference&D=med5&NEWS=N&AN=15930245. [6] Maume  DJ. Social ties and adolescent sleep disruption. J Health Soc Behav 2013;54(4):498–515. [Internet]. Available from: http:// www.ncbi.nlm.nih.gov/pubmed/24311758. [7] Maslowsky  J, Ozer  EJ. Developmental trends in sleep duration in adolescence and young adulthood: evidence from a national United States sample. J Adolesc Health 2014;54(6):691–7. [Internet]. Elsevier Ltd; Available from: https://doi.org/10.1016/j. jadohealth.2013.10.201. [8] Owens  J, Adolescent Sleep Working Group, Committee on Adolescence. Insufficient sleep in adolescents and young adults: an update on causes and consequences. Pediatrics 2015;134(3): e921–32. Au R, Millman R, Wolfson A, Braverman PK, Adelman WP, Breuner CC, Levine DA, Marcell AV, Murray PJ, O'Brien RF, Carskadon M, editors. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D= med8&NEWS=N&AN=25157012. [9] Wing  YK, Chan  NY, Man Yu  MW, Lam  SP, Zhang  J, Li  SX, et  al. A school-based sleep education program for adolescents: a cluster randomized trial. Pediatrics 2015;135(3):e635–43. [Internet]. Available from: http://pediatrics.aappublications.org/cgi/ doi/10.1542/peds.2014-2419. [10] Carskadon  MA, Vieira  C, Acebo  C. Association between puberty and delayed phase preference. Sleep 1993;16(3):258–62. [11] Carskadon MA, Acebo C, Jenni OG. Regulation of adolescent sleep: implications for behavior. Ann N Y Acad Sci 2004;1021(1):276– 91. [Internet]. Available from: http://doi.wiley.com/10.1196/ annals.1308.032.

Delayed school start times and adolescent health Chapter | 33  453

[12] O’Malley  EB, O'Malley  MB. 7 School start time and its impact on learning and behavior. Sleep Psychiatr Disord Child Adolesc 2008;5:79. [Internet]. Available from: http://www.neurofeedback. ch/downloads/Schlaf_und_Schule.pdf. [13] Frey S, Balu S, Greusing S, Rothen N, Cajochen C. Consequences of the timing of menarche on female adolescent sleep phase preference. PLoS ONE 2009;4(4):e5217. [14] Taylor DJ, Jenni OG, Acebo C, Carskadon MA. Sleep tendency during extended wakefulness: insights into adolescent sleep regulation and behavior. J Sleep Res 2005;14(3):239–44. [15] Sanya  EO, Kolo  PM, Desalu  OO, Bolarinwa  OA, Ajiboye  PO, Tunde-Ayinmode  MF. Self-reported sleep parameters among secondary school teenagers in middle-belt Nigeria. Niger J Clin Pract 2015;18(3):337–41. [16] National Sleep Foundation, editors. Adolescent sleep needs and patterns: research report and resource guide. 2000. [17] Barnes M, Davis K, Mancini M, Ruffin J, Simpson T, Casazza K. Setting adolescents up for success: promoting a policy to delay high school start times. J Sch Health 2016;86(7):552–7. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi? T=JS&PAGE=reference&D=prem&NEWS=N&AN=27246680. [18] Wheaton  AG, Ferro  GA, Croft  JB. School start times for middle school and high school students—United States, 2011–12 school year. MMWR Morb Mortal Wkly Rep 2015;64(30):809–13. [Internet]. United States; Available from: http://ovidsp.ovid.com/ ovidweb.cgi?T=JS&PAGE=reference&D=med8&NEWS=N& AN=26247433. [19] Position statements—Start school later [Internet]. [cited 2018 May 15]. Available from: http://www.startschoollater.net/position-statements.html. [20] Wahlstrom  K. School start time and sleepy teens. Arch Pediatr Adolesc Med 2010;164(7):676–7. [21] Wahistrom  K, Wahlstrom  K. Changing times: findings from the first longitudinal study of later high school start limes. NASSP Bull 2002;86(633):3–22. [Internet]. Available from: http://bul. sagepub.com/content/86/633/3%5Cnhttp://bul.sagepub.com/ content/86/633/3.full.pdf%5Cnhttp://bul.sagepub.com/content/86/633/3.short. [22] Owens JA, Belon K, Moss P. Impact of delaying school start time on adolescent sleep, mood, and behavior. Arch Pediatr Adolesc Med 2010;164(7):608–14. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D= med6&NEWS=N&AN=20603459. [23] Boergers J, Gable CJ, Owens JA. Later school start time is associated with improved sleep and daytime functioning in adolescents. J Dev Behav Pediatr 2014;35(1):11–7. [Internet]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24336089. [24] Wahlstrom KL, Dretzke BJ, Gordon MF, Peterson K, Edwards K, Gdula J. Examining the impact of later high school start times on the health and academic performance of high school students: a multi-site study. 2014. 72. Available from: http://www.ccsdschools. com/Community/documents/ImpactofLaterStartTime.pdf. [25] National Center for Education Statistics. Schools and Staffing Survey (SASS) [Internet]. Available from: https://nces.ed.gov/ surveys/sass/. [26] Paksarian  D, Rudolph  KE, He  J-P, Merikangas  KR. School start time and adolescent sleep patterns: results from the US National Comorbidity Survey-Adolescent Supplement. Am J Public Health 2015;105(7):1351–7.

[27] Wheaton AG, Chapman DP, Croft JB. School start times, sleep, behavioral, health, and academic outcomes: a review of the literature. J Sch Health 2016;86(5):363–81. [28] Marx R, Tanner-Smith EE, Davison CM, Ufholz L-A, Freeman J, Shankar  R, et  al. Later school start times for supporting the education, health, and well-being of high school students. Cochrane Database Syst Rev 2017;7:CD009467. [Internet]. England; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE =reference&D=mesx&NEWS=N&AN=28670711. [29] Wahlstrom  KL. Accommodating the sleep patterns of adolescents within current educational structures: an uncharted path. In: Adolescent sleep patterns. Cambridge University Press; 2002. [30] Danner F, Phillips B. Adolescent sleep, school start times, and teen motor vehicle crashes. J Clin Sleep Med 2008;4(6):533–5. [31] Wang  K, Sabia  JJ, Cesur  R. Sleepwalking through school: new evidence on sleep and academic performance [Internet]. [cited 2018 Apr 12]. (IZA Discussion Paper). Report No.: 9829. Available from: https://poseidon01.ssrn.com/delivery.php? ID=48307812300500009402808411900701212606306903005 00590410650161070471130580031181210241080870910060 73082122082094073070126084026070087092023094121071029102123000105088115125097114&EXT=pdf; 2016. [32] National Sleep Foundation. 2006 Sleep in America Poll—Teens and Sleep [Internet]. [cited 2018 Apr 12]. Available from: https://sleepfoundation.org/sleep-polls-data/sleep-in-america-poll/2006-teensand-sleep; 2006. [33] Hinrichs P. When the bell tolls: the effects of school starting times on academic achievement. Educ Financ Policy 2011;6(4):486–507. [Internet]. [cited 2018 Apr 12]; Available from: https://www.mitpressjournals.org/doi/pdf/10.1162/EDFP_a_00045. [34] Edwards F. Early to rise? The effect of daily start times on academic performance. Econ Educ Rev 2012;31(6):970–83. [Internet]. [cited 2018 Apr 12]; Available from: https://teensneedsleep.files.wordpress.com/2011/04/edwards-early-to-rise-the-effect-of-daily-starttimes-on-academic-performance-published-version.pdf. [35] Carrell SE, Maghakian T, West JE. A's from Zzzz's? The causal effect of school start time on the academic achievement of adolescents. Am Econ J Econ Pol 2011;3(3):62–81. [36] Admissions requirements—United States Air Force Academy [Internet]. [cited 2018 May 16]. Available from: https://www.usafa. edu/prep-school/admissions-requirements/. [37] Undergraduate age diversity at United States Air Force Academy [Internet]. [cited 2018 May 16]. Available from: https://www.collegefactual.com/colleges/united-states-air-force-academy/studentlife/diversity/chart-age-diversity.html. [38] About the ESS—Epworth Sleepiness Scale [Internet]. [cited 2018 Apr 16]. Available from: http://epworthsleepinessscale.com/ about-the-ess/. [39] Lufi  D, Tzischinsky  O, Hadar  S. Delaying school starting time by one hour: some effects on attention levels in adolescents. J Clin Sleep Med 2011;7(2):137–43. [Internet]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3077340/pdf/ jcsm.7.2.137.pdf. [40] Kessler  RC, Chiu  WT, Demler  O, Walters  EE. Prevalence, severity, and comorbidity of 12-Month DSM-IV disorders in the national comorbidity survey replication. Arch Gen Psychiatry 2005;62(6):617–27. [41] Kann L, Kinchen S, Shanklin SL, Flint KH, Kawkins J, Harris WA, et al. Youth risk behavior surveillance—United States, 2013. Morb

454  PART | VIII  Sleep Health in Children and Adolescents

Mortal Wkly Report Surveill Summ 2014;63(Suppl 4):1–168. (Washington, DC 2002). [42] Van Der HE, Walker MP. Overnight therapy? The role of sleep in emotional. Psychol Bull 2010;135(5):731–48. [Internet]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2890316/ pdf/nihms206917.pdf. [43] Wahlstrom KL, Berger AT, Widome R. Relationships between school start time, sleep duration, and adolescent behaviors. Sleep Heal J Natl Sleep Found 2017;https://doi.org/10.1016/j.sleh.2017.03.002. (In press). [Internet]. Elsevier Inc.; Available from:. [44] Daly  BP, Jameson  JP, Patterson  F, McCurdy  M, Kirk  A, Michael  KD. Sleep duration, mental health, and substance use among rural adolescents: developmental correlates. J Rural Ment Health 2015;39(2):108–22. [Internet]. Available from: http://search. ebscohost.com/login.aspx?direct=true&db=pdh&AN=201528960-005&site=ehost-live%[email protected]. [45] Winsler  A, Deutsch  A, Vorona  RD, Payne  PA, Szklo-Coxe  M. Sleepless in fairfax: the difference one more hour of sleep can make for teen hopelessness, suicidal ideation, and substance use. J Youth Adolesc 2015;44(2):362–78. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference &D=med8&NEWS=N&AN=25178930. [46] Baum KT, Desai A, Field J, Miller LE, Rausch J, Beebe DW. Sleep restriction worsens mood and emotion regulation in adolescents. J Child Psychol Psychiatry Allied Discip 2014;55(2):180–90. [47] Gregory  AM, Caspi  A, Eley  TC, Moffitt  TE, O'Connor  TG, Poulton  R. Prospective longitudinal associations between persistent sleep problems in childhood and anxiety and depression disorders in adulthood. J Abnorm Child Psychol 2005;33(2):157–63. [Internet]. Available from: https://link.springer.com/content/ pdf/10.1007%2Fs10802-005-1824-0.pdf. [48] Clarke  G, Harvey  AG. The complex role of sleep in adolescent depression. Child Adolesc Psychiatr Clin N Am 2012;21(2):385– 400. [Internet]. Elsevier; Available from: https://doi.org/10.1016/j. chc.2012.01.006. [49] McMakin DL, Dahl RE, Buysse DJ, Cousins JC, Forbes EE, Silk JS, et al. The impact of experimental sleep restriction on affective functioning in social and nonsocial contexts among adolescents. J Child Psychol Psychiatry Allied Discip 2016;57(9):1027–37. [50] Lo JC, Ong JL, RLF L, Gooley JJ, MWL C. Cognitive performance, sleepiness, and mood in partially sleep deprived adolescents: the need for sleep study. Sleep 2016;39(3):687–98. [Internet]. Available from: https://academic.oup.com/sleep/article-lookup/doi/10.5665/sleep.5552. [51] Edwards S, Reeves GM, Fishbein D. Integrative model of the relationship between sleep problems and risk for youth substance use. Curr Addict Rep 2015;2(2):130–40. [52] Hasler BP, Smith LJ, Cousins JC, Bootzin RR. Circadian rhythms, sleep, and substance abuse. Sleep Med Rev 2012;16(1):67–81. [53] Hasler BP, Clark DB. Circadian misalignment, reward-related brain function, and adolescent alcohol involvement. Alcohol Clin Exp Res 2013;37(4):558–65. [54] Hasler BP, Soehner AM, Clark DB. Sleep and circadian contributions to adolescent alcohol use disorder. Alcohol 2015;49(4):377–87. [55] Berger AT, Widome R, Troxel WM. School start time and psychological health in adolescents. Curr Sleep Med Rep 2018;. Available from: https://link.springer.com/content/pdf/10.1007/s40675-018-0115-6.pdf.

[56] Wahlstrom KL. Technical report, volume II: analysis of student survey data. 1998. II(November). [57] Vedaa  Ø, Saxvig  IW, Wilhelmsen-Langeland  A, Bjorvatn  B, Pallesen  S. School start time, sleepiness and functioning in Norwegian adolescents. Scand J Educ Res 2012;56(1):55–67. [58] Perkinson-Gloor N, Lemola S, Grob A. Sleep duration, positive attitude toward life, and academic achievement: the role of daytime tiredness, behavioral persistence, and school start times. J Adolesc 2013;36(2):311–8. [Internet]. England; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=reference&D=med8&NE WS=N&AN=23317775. [59] Martin  JS, Gaudreault  MM, Perron  M, Laberge  L. Chronotype, light exposure, sleep, and daytime functioning in high school students attending morning or afternoon school shifts: an actigraphic study. J Biol Rhythm 2016;31(2):205–17. [Internet]. United States; Available from: http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE =reference&D=med8&NEWS=N&AN=26825618. [60] Chan NY, Zhang J, MWM Y, Lam SP, Li SX, APS K, et al. Impact of a modest delay in school start time in Hong Kong school adolescents. Sleep Med 2017;30:164–70. [Internet]. Elsevier Ltd; Available from: https://doi.org/10.1016/j.sleep.2016.09.018. [61] Wheaton AG, Olsen EO, Miller GF, Croft JB. Sleep duration and injuryrelated risk behaviors among high school students—United States, 2007–2013 [Internet]. Vol. 65, Morbidity and mortality weekly report. Atlanta, GA; [cited 2018 Apr 9]. Available from: https://www. cdc.gov/mmwr/volumes/65/wr/mm6513a1.htm; 2016. [62] Governors Highway Safety Association. Mission not accomplished: teen safe driving, the next chapter [Internet]. [cited 2018 Apr 6]. Available from: https://www.ghsa.org/sites/default/files/2016-12/ FINAL_TeenReport16.pdf; 2017. [63] Tefft  BC. Prevalence of motor vehicle crashes involving drowsy drivers, United States title prevalence of motor vehicle crashes involving drowsy drivers, United States. [cited 2018 Apr 6]; Available from: www.aaafoundation.org; 2009. [64] Knipling  RR, Wang  J-S. Crashes and fatalities related to driver drowsiness/fatigue. Research Note 1996. [65] Vorona  RD, Szklo-Coxe  M, Wu  A, Dubik  M, Zhao  Y, Ware  JC. Dissimilar teen crash rates in two neighboring southeastern Virginia cities with different high school start times. J Clin Sleep Med 2011;7(2):145–51. [66] Vorona RD, Szklo-Coxe M, Lamichhane R, Ware JC, McNallen A, Leszczyszyn  AD, et  al. Adolescent crash rates and school start times in two Central Virginia Counties, 2009–2011: a follow-up study to a Southeastern Virginia study, 2007–2008. J Clin Sleep Med 2014;10(11):1169E–77E. [67] Yiannakoulias  N, Bland  W, Scott  DM. Altering school attendance times to prevent child pedestrian injuries. Traffic Inj Prev 2013;14(4):405–12. [Internet]. [cited 2018 Apr 11]; Available from: http://www.tandfonline.com/doi/abs/10.1080/15389588.2 012.716879 [68] Hafner  M, Stepanek  M, Troxel  WM. The economic implications of later school start times in the United States. Sleep Heal 2017;3(6):451–7. [Internet]. National Sleep Foundation; Available from: https://doi.org/10.1016/j.sleh.2017.08.007.