Snoring, Apneic Episodes, and Nocturnal Hypoxemia Among Children 6 Months to 6 Years Old

Snoring, Apneic Episodes, and Nocturnal Hypoxemia Among Children 6 Months to 6 Years Old* An Epidemiologic Study of Lower Limit of Prevalence Thorarinn Gislason, MD, PhD, FCCP; and Bryndis Benediktsdottir, MD Study objective: To identify a lower limit of the prev-

alence of sleep-related breathing disturbances among preschool children. Design: A cross-sectional epidemiologic study in two stages, first by questionnaires and second by wholenight investigation of children symptomatic of the sleep apnea syndrome. Setting: Gardabaer, a small town, 10 km south of Reykjavik, Iceland. Participants: All children in Gardabaer, 6 months to 6 \ years old (n=555). Measurements: Symptom score estimated by que\tionnaire and respiratory events based on overnight oximetry, thermistors, and a static charge sensitive bed;Results: The response rate was 81.8o/0 • Snoring was reported as often or very often among 14 (3.2%) and occasionally by 73 (16.7%). Apneic episodes were reported often or very often among seven (1.6%). Altogether 18 children were highly suspected of the sleep apnea syndrome because of habitual snoring or apneic

sleep-disordered breathing has been found to affect a surprisingly high proportion of both middleaged men and women.I- 3 Among adults suffering from the sleep apnea syndrome (SAS), the most common symptoms are habitual snoring, apneic episodes, and daytime sleepiness and the majority are overweight. In children with SAS, loud snoring and breathholding during sleep are usually present,4 but other symptoms are more variable. 5 The children with SAS often show a failure to thrive and some are below the 25th percentile by weight, rather than being overweight. 5·6 The occlusion of the upper airway is most frequently associated with an upper airway anatomic abnormality with hyperplasia of the adenoid and / or tonsillar tissue as the major cause. 5 In severe cases there is C02 retention, 6 and even *From the Department of Pulmonary Medicine, Gardabaer, Iceland (Dr. Gislason) , and the Department of Family Medicine, University of Ice land (Dr. Benediktsd6ttir). Manuscript received February l, 1994; revision accepted September 2.

Reprint requests: Dr. Gislason, Department of Pulmonary Medicine, Vifilsstadir, Garoabae 210, Iceland.

episodes. The girls (n=9) were older than the boys (mean age: 46 ± 21 months vs 20 ± 12 months, p<0.001). Eventually 11 children came for a whole-night investigation and 8 of them showed more than three respiratory events per hour of sleep, associated with 2:4% oxygen desaturation. The lower limit of the sleep apnea syndrome prevalence among these children was thus 2.9% (SE, 0.5%). Conclusions: Among children, symptoms such as snoring and apneic episodes are reported relatively seldom, but a high proportion of the children with these symptoms have hypoxic respiratory events.

(Chest 1995; 107:963-66)

Sa02=arterial oxygen saturation; SAS=sleep apnea syndrome; SCSB=static charge sensitive bed; URTI=upper respiratory tract infection

Key words: epidem iology; preschool children; sleep apnea; snoring

cardiovascular complications have been reported. 7 Compared with adults, very few studies have been published about the prevalence of SAS among children. Most of these studies were performed in connection with an adenoidectomy / tonsillectomy.6,8-l0 The aim of this study was to identify a lower limit of the prevalence of snoring and apneic episodes during sleep among children 6 months to 6 years old. Of this sample, a subgroup of children highly suspected of having SAS was invited for whole-night studies. MATERIAL AND METHODS

This study on sleep disturbances was part of a larger epidemiologic survey on the interrelationship between upper respiratory tract infections (URTI), age, gender, daily life, social surroundings, and sleep 11 All children aged 6 months to 6 years old (n=555 ) living in Gardabaer, a small town with 6,843 inhabitants, 10 km south of the capital city Reykjavik, Iceland, were included in this study. After a pilot study, we constructed a questionnaire consisting of four major parts concerning the following: social surroundings, daily routines, health history, and sleep 11 The questionnaire was CHEST I 107 I 4 I APRIL, 1995

963

posted to "The Person in Charge," marked with the child's nam e and address. There were specific questions about both adenoidectomy and tonsillectomy. There was also a question about "the number of smokers in the home." We asked the parents how often during the previous 3 months the child had been infected with the following: cold; tonsillitis; otitis media; and bronchitis, and thus the number of ORTis was calculated as the sum of these infections. 11 In the part concerning sleep, the parents were asked to state the severity of sleep-related complaints by means of a five-point scale. In the subsequent statistical evaluation, scores of 4 (often) and 5 (very often) were defined as habitual and a score of 3 (sometimes) as occasional, but the scores of 1 (never ) and 2 (seldom ) were defin ed as not existing. The following questions were asked: Does the child snore? Have you noticed brea thing cessations during sleep? Is the child restless when sleeping? Is the child tired or irritated during the day? Is the child abnormally sleepy during the day?

Laboratory Studies The children slept at the pulmonary departm ent one night, together with one parent. Respiration was monitored by a static charge sensitive bed (SCSB) (Biorec OY , Kuusisto, Finland). Sleep time (in minutes) was estimated the following morning. We subtracted from the time in bed all tim e awake during that period, based on the estimation of parents/ nurses and the SCSB. Airflow was measured by a coupled nose and mouth thermistor. Arterial oxygen saturation (SaOz) was measured simultaneously with both a finger and a flex probe with two pulse oximeters (BIOX 3700 Ohmeda). In our analysis of respiratory events, all such events were counted when there was a dip in SaOz on one or both oximeters. We counted only those Sa02 dips appearing together with a marked decrease in oronasal airflow and/ or an increased amplitude on the SCSB records in respiration movements 10 compared with baseline level. Later the number of respiratory events with SaOz dipping 2:4% per hour estimated sleep tim e was calculated and three or more such events per hour estimated sleep were used as criteria for SAS. Blood samples were taken in the morning for measurements of thyroid-stimulating hormone and routine blood values.

Statistics All values are given as means± SDs. Differences were tested by a two-tailed t test. Ax2 test was used for comparison of proportions. RESULTS

After two reminders, 454 (81.8%) questionnaires were obtained for further study .ll There were 203 boys and 251 girls (Table 1). Adenoidectomy was Table l-Age and Gender

Responders

Habitual Snoring and / or Apneic Episodes

Age Group

Boys

Girls

Boys

6 mo-l yr 1-2 yr 2-3 yr 3-4 yr 4-5 yr 5-6 yr Total

32 39 33 32 36 31 203

27 45 38 39 56 46 251

2 4 2

964

0 0 9

Girls 1 0 2 2 3 9

reported by 43 boys (22.5%) and 34 girls (14.4%) (p<0.05). Only 6 children had undergone tonsillectomy, all but 1 adenoidectomy as well.

Snoring and Apneic Episodes Fourteen children (3.2%) were reported as habitual (scores 4 and 5) snorers and 73 (16.8%) as occasional (score 3) snorers. Snoring was somewhat more frequent among boys than girls; habitual snoring 3.6% vs 2.9 % and occasional snoring 20.7 % vs 13.6% (p=0.1). Habitual snoring and occasional snoring were somewhat more common in children who had undergone adenoidectomy (5.3% and 18.4% vs 3.0% and 14.8%), but this difference was not statistically significant (p = 0.41). None of the 6 children who had undergone tonsillectomy was a habitual snorer. Smoking was reported in 50.4% of the homes but the prevalence of snoring was neither related to the reporting of smoking nor the number of smokers in the home. Apneic episodes were habitual in 7 children (1.6%) and occasional in 15 (3.4%).

Selection Procedure All children who were reported as snoring often (six) or very often (eight) and / or were having apneic episodes often (four) or very often (three) were selected for whole-night studies. Both symptoms were reported by three. Thus, a group was formed with 18 children symptomatic of SAS: 9 boys and 9 girls (Table 1). The girls were older than the boys; mean age in months was 46 ( ± 21) vs 20 ( ± 12) (p<0.001). The 18 children symptomatic of SAS were more often sleepy and irritated during the daytime and slept more restlessly during the night compared with children who did not have apneic episodes or snored habitually (Table 2). Their mean number of URTis during the previous 3 months was 2.7 (± 1.2) vs 1.6 ( ± 1.3) (p<0.001). Table 2-Symptomatic Children (Snoring and/ or Apneic Episodes) Compared With Others Snoring and/ or Apneic Episodes, % (n=l8) Restless sleep 33 .3 Not existing 38.9 Occasionally 27.8 Habitually Daytime tiredness/irritability 38.9 Not existing 44.4 Occasionally 16.7 Habitually Abnormal daytime sleepiness 77.8 Not existing 22.2 Occasionally Habituall y 0

Others, % (n=436)

p Value

74.2 21.8 4.0

<0.001

65.5 32.6 1.9

<0.001

92.2 6.6 1.2

<0.05

Snoring, Apneic Episodes, and Nocturnal Hypoxemia Among Children (Gislason, Benediktsdottir)

Table 3-Results From Sleep Studies Respiratory Events Associated With Sa0 2 Desaturation of Case No. / Sex/ Age, mo

Estimated Sleep Tim e, min

1/ F /63 2/ F / 49 3/ F / 63 4/ F /84 5 / M/ 49 6/ F / 36 7/ M/ 25 8/ M/ 21 9/ F / 60 10/ F / 59 11 / M/ 32 Mean 49 SD 19

360 570 510 600 550 510 490 275 610 560 505 504 102

2%

3%

4-6%

7-8%

~9%

No. of ~4 % dips/ h

26 8 2 5 7 2 0

58 11 10 7 4 9 5 5 20 18 20 15 15

53 4 27 41 12 30 11 21 33 29 28 26 14

0 0 3 0 3 12 0 3 3 3 5 3 4

3 0 0 0 1 1 0 0 1 3 2 1

9.3 0.4 3.5 4.1 1.7 5.1 1.3 5.2 3.6 3.8 4.2 3.8 2.3

13 11 7 7 7

In four cases, the parents preferred to go directly to adenoidectomy and / or tonsillectomy without a night study, and in all cases there was postoperatively a clinical disappearance of symptoms. One parent among the 18 children reported spontaneous disappearance of symptoms and was not interested in further investigation. Two children had moved away. The remaining ll children came for a whole-night investigation. There was no statistically significant difference in reported symptoms between the ll investigated children and the other 7 concerning restless sleep, daytime tiredness, and number of URTis. Among those ll children investigated, the girls (seven) were older than the boys (four) with a mean age (months) of 59 ( ± 15) vs 32 ( ± 12) (p<0.01) for the boys. According to their parents, there was no major change in symptoms from the time of the questionnaire until the laboratory investigation was performed, except in one boy (case 5) in whom the symptoms had diminished (Table 3).

Laboratory Studies The mean estimated sleep time was 504 ( ± 102) min; only one child slept less than 6 h (Table 3). None of the children had symptoms of UR TI at the time of the whole-night study; the mean erythrocyte sedimentation rate was 6.4 mm / h and none was hypothyroid. All 11 children had some respiratory events associated with Sa02 dips >2% (Table 3). The mean total number of all such events was 53 ( ± 34) during the night (Table 3). The mean number of respiratory events with Sa02 dips >4% was 30 ( ±15). There were eight children with three or more respiratory events associated with >4% desaturations per hour estimated sleep. Thus, given these criteria for SAS and using statistical methods similar to those we have previously employed,2·3 .l 2 the lower limit of SAS prevalence among children 6 months to 6 years was 8/ llx18/ 454=2.9% with a standard er-

ror=0.5% . DISCUSSION

The survey participation rate was almost 82% and the responders had the same age distribution as the study population.U There were no systematic differences in answers to the first, second, and third letters concerning age, gender, or the prevalence of sleeprelated symptoms. It is therefore unlikely that the responders differ systematically from the responders. The prevalence of SAS symptoms is much lower among children than adults.I- 3 However, the lower limit of the SAS prevalence (2.9%) among children is similar to what we have reported among adults 2•3 and comparable to what others have reported in preoperative studies of snoring children 8.l 0 and even higher than has been reported in a cohort of children with Down's syndrome.l 3 It is also important to realize that our method of first selecting children who are symptomatic and then screening these individuals for sleep apnea will always lead to a lower limit of prevalence. We found an overrepresentation of snoring and apneic episodes among young boys (Table 1). Others have reported a similar prevalence of snoring among older boys and girls in France (10%) 14 and in Italy (7.3%).1 5 This difference is probably due to the fact that young boys in our study more often had URTis. 11 The association between habitual snoring and UR TI is well known from other studies. 10.l 4 Among Italian children, habitual snoring was more common in children from smoking households 15 but in our study smoking was neither related to snoring nor to the number of URTis.l 1 The definition of SAS among children is disputable , especially when sleep and intrathoracic pressure are not monitored . The importance of small Sa02 dips (Table 3) is unknown. Stradling and coworkers8 investigated 31 healthy children; none of CHEST I 107 I 4 I APRIL, 1995

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these had more than three dips in Sa0 2 >4% per hour and new overnight oximetry 6 months later showed the same result. Our criteria are stricter, as we demanded at least three dips in Sa0 2 (>4%) per hour and simultaneously decreased air flow and/ or increased amplitude on the SCSB. In a recently published study of 782 children aged 4 to 5 years, 12.1% were reported to snore on most nights.I 6 However, only one third (22 of 66) of the "snoring" children snored when monitored at home with overnight video recording and oximetry. Based on monitoring in 132 children, the authors estimated the prevalence of sleep and breathing disturbances to be 0.7%. 16 Having in mind how high the lower limit of the SAS prevalence is and the possibility of serious consequences from this disorder, future trends in adenoidectomy /tonsillectomy and other treatments for SAS must be based on more objective data . It is therefore necessary, whenever a suspicion of SAS is the main indication for adenoidectomy /tonsillectomy, to confirm the diagnosis, as is common practice for adults today. REFERENCES

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survey of middle-aged women. Chest 1993; 103:1147-51 4 Potsic WP. Sleep apnea in children. Otolaryngol Clin North Am 1989; 22:537-44 5 Guilleminault C , Stoohs R. Chronic snoring and obstructive sleep apnea syndrome in children. Lung 1990; 168(suppl): 912-19 6 Lind MG, Lundell BPW. Tonsillar hyperplasia in children: a cause of obstructive sleep apnea, COz retention, and retarded growth. Arch Otolaryngol 1982; 108:650-54 7 Wilkinson AR, McCormick MS, Freeland AP, et al. Electrocardiographic signs of pulmonary hypertension in children who snore. BMJ 1981; 282:1579-82 8 Stradling JR, Thomas G, Warley ARH, et al. Effect of adenotonsillectomy on nocturnal hypoxemia, sleep disturbance, and symptoms in snoring children. Lancet 1990; 335:249-53 9 Croft CB, Brockbank MJ, Wright A, et al. Obstructive sleep apnea in children undergoing routine tonsillectomy and adenoidectomy. Clin Otolaryngol1990; 15:307-14 10 Svanborg E, Larsson H, Carlsson-Nordlander B. Indications of sleep-related upper airway obstruction in children. In: Peter JH, Penzel T, Podszus T, von Wichert P, eds. Sleep. Berlin: Springer-Verlag, 1991 ; 468-75 11 Benediktsd6ttir B. Upper airway infections in preschool children-frequency and risk factors. Scand Prim Health Care 1993; 11:197-201 12 Gislason T, Taube A. Prevalence of sleep apnea syndromeestimation by two stage sampling. Up J Med Sci 1987; 92:193203 13 Stebbens VA, Dennis J, Samuels MP, et al. Sleep-related upper airway obstruction in a cohort with Down's syndrome. Arch Dis Child 1991; 66:1333-38 14 Teculescu DB, Caillier I, Perrin P, et al. Snoring in French preschool children. Pediatr Pulmonol1992; 13:239-44 15 Corbo GM, Fuciarelli F, Foresi A, et al. Snoring in children: association with respiratory symptoms and passive smoking. BMJ 1989; 299:1491-94 16 Ali NJ, Pilson DJ, Stradling JR. Snoring, sleep disturbance and behaviour in 4-5 year olds. Arch Dis Child 1993; 68:360-66

Snoring, Apneic Episodes, and Nocturnal Hypoxemia Among Children (Gislason, Benediktsdottir)