Prevalence of Sleep Disorders and Sleep Behaviors in Children and Adolescents

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1 Prevalence of Sleep Disorders and Sleep Behaviors in Children and Adolescents JOHN F. SIMONDS, M.D., AND HUMBERTO PARRAGA, M.D. Maternal reports were used to assess the prevalence of a comprehensive group of sleep disorders and behaviors in a rural population of school-aged children. Some sleep behaviors occurred in significantly greater numbers of subjects on the basis of age, sex, socioeconomic status, and chronic medical problems and/or ear, nose, and throat allergies. Journal of fhe American Academy of Child Psychiatry, 1, 4: , 198. Sleep disorders in children have become the focus of interest both as primary disorders and disorders secondary to other emotional and medical conditions. Definitions of particular sleep disorders have become more specific in recent years (Diagnostic and Statistical Manual of Mental Disorders APA, 1980). Past prevalence rates of sleep disorders were often based on ambiguous definitions (Hertzman, 1948). The DSM-III (1980) recognizes four groups of sleep and arousal disorders: (1) disorders of initiating and maintaining sleep, () disorders of excessive somnolence, (3) disorders of the sleep-wake schedule, and (4) dysfunctions associated with sleep, sleep stages or partial arousals, such as ~leepwalking, slep-p terror, sleep-related enuresis, and sleep-related bruxism. A greater number of sleep disorders in children have been recognized (Anders and Weinstein, 197), and a workable classification system has been applied (Karacan et al., 1973). In this study we focused on the sleep disorders which have been identified in children and which can be clinically observed, i.e., sleepwalking, sleep terror, sleep-related enuresis, sleep-related bruxism, narcolepsy, sleep-related myoclonus, sleep-related head banging, sleep apnea, and dream anxiety attacks. Other sleep-related activities which are not defined in DSM-III (1980) as sleep disorders were called sleep behaviors, e.g., snoring, fears of dark, need for security object, bedtime rituals, daytime drowsiness, restless sleeping, biting tongue, gagging, fears of sleeping, and need to sleep with another family member. A comprehensive study of the prevalence of a range of sleep disorders and sleep behaviors in a child and adolescent population has not been reported in the literature. Bixler et al. (1979) studied the occurrence of current and past sleep disorders in an adult population. The Lapouse and Monk study (1959) and the McFarlane et al. study (19) focused on a variety of behaviors in children and nightmares were the main sleep disorder surveyed. Most other prevalence studies were based on one or two sleep disorders (Hertzman, 1948) or were based on a psychiatrically disturbed sample population (Shirley and Kahn, 1958). The objective of this project was to determine the prevalence of various sleep disorders and sleep behaviors in a random sample of subjects, ranging in age from 5 years to 0 years, selected from community schools. Our study made use of expanded numbers of sleep behaviors and disorders which were expressed in lay terms in order to eliminate false positive and false negative responses due to ambiguity of terms. Method Instruments A two-part questionnaire was developed by the investigators as a result of a review of the literature and a consensus about relevant questions concerning children's sleep behavior that could be answered simply. The questionnaire was to be answered by the subject's mother and as such would have distortions related to maternal perception. Part I of the questionnaire l included questions about the child's age, height, weight, medical problems, and medications. It also had questions concerning the quantity and quality of sleep, e.g., how long does it usually take for your child to fall asleep? Part II of the questionnaire was concerned with the previously mentioned sleep disorders and behaviors which were explicitly expressed in lay language. The wording for dream anxiety attacks was "awakens dur- Dr. Simonds is Professor Psychiatry, University of Missouri Medical School, Department of Psychiatry, Columbia, Missouri. Dr. Parraga is Assistant Professor Psychiatry, Southern Illinois University School of Medicine and Director of the Children and Adolescent Unit ofmcfarland Mental Health Center, Springfield, Illinois. Reprints may be requested from: John F. Simonds, M.D., Department of Psychiatry, University of Missouri Medical School, Columbia, MO /8/ $0.00/0 198 by the American Academy of Child Psychiatry. I The questionnaire can be obtained from the authors upon request. 383

2 384 JOHN F. SIMONDS AND HUMBERTO PARRAGA ing night complaining of nightmare or frightening dream and during this awakening seems moderately anxious." A night terror episode was presented as "awakens during the night screaming in terror about people or things in the room that are not there. Anxiety is so severe that sweating, gasping or trembling may occur. Usually the child is not aware of his surroundings and will not remember the event the next day." The parent was asked to state how frequently these behaviors or disorders occurred during the previous 6-month period by checking a five-level frequency scale ranging from daily to less than once per month. There were also some questions regarding the occurrence of certain sleep disorders, Le., sleepwalking, bedwetting, and night terrors in immediate family members. Part II of the questionaire was administered to 15 staff and faculty members whose children ranged from 5 years to 17 years. Two weeks after completing this questionnaire the mothers of these children were asked to complete the same questionnaire again. A Spearman correlation coefficient was determined for each of 4 questions which were answered on a scale from 0 to 5. The "r" values ranged from a low of 0.83 to a high of There were 19 "r" values of 1.00 and 4 between 0.90 and The questionnaire was assumed to have face validity. Subject Selection The superintendent of schools of a midwest community having one senior high school, one junior high school, and two elementary schools gave permission to contact any parent of a student in his school system. Master lists with students' names, addresses, and phone numbers were provided. The principal of a second rural high school also provided us with a list of students from 9th through 1th grades. The investigators randomly selected a total of 369 names of students from kindergarten through 1th grade. Parents were contacted by mail. A letter explained the purpose of our project. The sleep behavior questionnaires were included in the mailed packet. Mothers were asked to complete the questionnaires and return the completed questionnaires in a stamped, self-addressed envelope. Data Analysis This project involved a cross-sectional study. Data were based on mothers' reports. The frequency of sleep behaviors was calculated on the basis of at least one occurrence in the previous 6 months. These frequencies were determined for each age, sex, socioeconomic status (SES), and medical variables. Relationship between the presence or absence of a particular sleep behavior and age, sex, SES, and medical variables was determined by chi square tests. Subjects Questionnaires were mailed to the mothers of 369 subjects of whom 309 (83.7%) completed the questionnaires, 45 (1.%) refused, and 15 (4.1%) agreed to participate but failed to return the questionaire (1 of these 15 turned in a completed questionnaire too late for inclusion in the statistical analyses). There were 158 males (51.1%) and 151 females (48.9%) in the final study group. The distribution of subjects according to the modified Hollingshead (Myers and Bean, 1968) SES classification was as follows: classes I and II (highest) 8 (9.1%), class III (middle) 99 (3%), and classes IV and V (lowest) 18 (59%). Of the total number of subjects participating 44 (14.4%) had at least one chronic illness or ear, nose, throat (ENT) allergy problem. The age distribution of subjects was fairly even across all ages except the youngest and oldest group (5 to 8 years 4.4%, 9 to 11 years 1.1%, 1 to 14 years 18.8%, 15 to 18 years 35.7%). One 0year-old was a senior in high school and this subject was excluded in all data that specifically included 15to 18-year-olds. Results In general children and adolescents slept soundly (93.5%) and were in good mood upon awakening in the morning (85.5%). About 45% of the subjects were reported to act differently the day following a poor night's sleep. Only a few children (15.9%) took naps during the day. Most children had more than one sleep behavior or disorder but each behavior and disorder was considered separate from all others. Table 1 lists the percentage of subjects in whom sleep-related behaviors occurred at least once during a previous 6-month period. The percentage of subjects having at least a weekly frequency are also listed. Those behaviors not listed occurred in less than % of the sample. Sleeptalking occurred in more subjects than any other behavior. Restless sleep was a symptom for 34.6% of the sample but on a daily basis it was found in 0.4% of the population. Irresistible urges to sleep during the day occurred in 5.3% of 5- to 8-year-olds, 1.5% of 9- to 11-year-olds, 3.5% of 1- to 14-year-olds, and 10% of 15- to 18-yearolds. One subject had cataplexy-like symptoms combined with sleep paralysis. Three subjects had sleep paralysis alone and one subject had cataplexy-like symptoms alone. Daytime drowsiness was reported in 5.3% of 5- to 8-year-olds, 6.% of 9- to 11-year-olds, 1.1% of 1- to 14-year-olds, and 11.8% of 15- to 18-

3 SLEEP DISORDERS AND SLEEP BEHAVIORS 365 TABLE 1 Prevalence of Sleep Disorders and Behaviors in Children and Adolescents During 6 Months Prior to Survey Sleep Disorders and Sleep Behaviors Sleeptalking Restless sleeper Snoring Nightmares Grinding teeth Fearful of dark Bed wetting Need for security object Insistence on sleeping with others Sleepwalking Drowsy during daytime Bedtime rituals Fearful going to sleep Irresistible sleepiness Night terrors % Subjects with at Least 1 Episode % Subjects with at Least Weekly Episodes year-oids. However a weekly frequency of daytime drowsiness was only found in 4.9% of the subjects. Some parasomnias were strongly associated with other parasomnias. Bedwetting and sleepwalking occurring at least once during a 6-month period were associated in.6% of the sleepwalkers. Sleepwalking was associated with night terrors in 9.7% of the sleepwalkers. Bedwetting occurred in association with sleepwalking in 19.4% of the bedwetters and in association with night terrors in 16.7% of the bedwetters. Only seven subjects had night terrors; six of these were bedwetters (85.7%) and three were sleepwalkers (4.9%). The variables of sex, SES, age, and chronic medical problems and ENT allergies were tested (chi square tests) to determine whether anyone variable was independent of another variable. All chi square tests were nonsignificant except for SES and sex (X = 6.36, P < 0.05). There was a skewed distribution of females in SES classes I and II (0) compared to males in SES classes I and II (8). The relationship between sleep behaviors and sex of the subjects was determined by chi square tests. Males were more likely to wet beds (4 vs. 1, X = 3.9, P < 0.05) and snore (59 vs. 37, X = 5.9, P < 0.0) while females were more likely to report dreams (119 vs. 84, X =.5, P < 0.01) and to have bedtime rituals (1 vs. 6, X = 9.9, P < 0.01). All other sleep behaviors failed to show significant differences due to the sex variable. Table shows the significant relationships between sleep behaviors and SES of the subject. Subjects in classes IV and V were most likely to awaken during the night, to snore, to be restless sleepers, to be fearful TABLE Relationship ofsleep Behaviors to Socioeconomic Status (SES) No. Subjects in SES Class: Sleep Behavior X p value I and IV III II and V Night time awakenings No night time awak <0.03 enings Restless sleeping No restless sleeping <0.01 Snoring No snoring <0.0 Fearful going to sleep 3 1 Not fearful going to <0.05 sleep Drowsy during day 4 Not drowsy during day <0.01 of going to sleep, and to become drowsy during the day. Significantly more subjects having chronic medical' problems or ENT allergies wet their beds (30% vs. 9%, X = 15.9,p < 0.001); reported unpleasant dreams (39% vs. %, X = 5.1, P < 0.03); required security objects at bedtime (30% vs. 9%, X = 15.9, P < 0.001); were afraid of the dark (7% vs. %, X = 6., P < 0.0); and had bedtime rituals (18% vs. 7%, X = 5.7, P < 0.0) compared to subjects not having chronic medical problems or ENT allergies. There was also a trend for more subjects having chronic medical problems or ENT allergies to snore during the night (43% vs. 9%, X = 3.5, P < 0.07). Table 3 shows the significant relationships between sleep behaviors and age groups of subjects. Significantly more younger subjects than older subjects had the following sleep behaviors: bedtime rituals, insistence on sleeping with other family members, need for security objects, fear of dark, fear of going to sleep, nightmares, bedwetting, teeth grinding. On the other hand significantly more oldest subjects took daytime naps. Night terrors occurred in only 5.33% of the 5- to 8-year-olds, 3.08% of 9- to ll-year-olds, 0% of 1- to 14-year-olds, and 0.9% of 15- to 18-year-olds. Nightmares occurred in 8% of 5- to 8-year-olds, 3% of 9 to ll-year-olds, 10% of 1- to 14-year-olds, and 8% of 15- to 18-year-olds. Sleepwalking occurred in 1% of5 to 8-year-olds, 15.4% of 9- to ll-year-oids, 10.3% of 1 to 14-year-olds, and 5.5% of 15- to 18-year-olds. Discussion The nightmare or "dream anxiety attack" can affect all ages (Kramer, 1979). In our sample there was an occurrence of at least one nightmare in the previous 6 months in 16.5% of the sample population. The fre-

4 386 JOHN F. SIMONDS AND HUMBERTO PARRAGA TABLE 3 Number ofsubjects with Sleep Disorders and Behaviors According to Age Groupings of Subjects Sleep Disorder or Behavior Daytime naps No daytime naps Teeth grinding No teeth grinding Bedwetting No bedwetting Nightmares No nightmares Fearful going to sleep Not fearful going to sleep Fearful of dark Not fearful of dark Insistence on sleeping with others No insistence on sleeping with others Need for security object No need for security object Bedtime rituals No bedtime rituals Age (yr): l p value 8.41 < < < < <0.01 quency of nightmares diminished with increasing age. However the 6% prevalence rate in 5- to ll-year-olds matches closely the 8% prevalence of nightmares reported by Lapouse and Monk (1959) in a sample of normal children. Another study of a normal population (MacFarlane et ai., 19) gave the percentages of subjects having disturbing dreams as follows: 9% of boys and girls at age 3, 33% of boys and 47% of girls at age 10, and 6% of boys and 4% of girls at age 14. Our study does not reflect this peak in disturbing dreams at age 10 years but it does reflect the sharp drop in occurrence of nightmares during the teenage years. Since disturbing dreams may not reach the degree of severity of a "nightmare," differences in the percents probably are due to interpretation of the severity of discomfort caused by the dream. There was an overall occurrence of at least one night terror in.66% of our sample. This was quite similar to the literature estimate of 1 night terror in 1% to 3% of all children between 5 years and 1 years (Kales et ai., 1968). Our data did show night terrors to be a more common phenomenon (5.3%) in the youngest age group. Our study found 10.03% of the population of children and adolescents were observed to have sleepwalked at least once in the previous 6 months while sleepwalking at least once per week occurred in.3%. Sleepwalking was not influenced significantly by age, sex, chronic medical problems and ENT allergies, or SES. There was a greater incidence of sleepwalkers in younger aged children than in the teenage population but the difference was not significant. The literature reports that 15% of the children between 5 and 1 years have walked in their slp,ep at least once (Anders and Weinstein, 197) and 1% to 6% are persistent sleepwalkers (Kales and Kales, 1974). Bedwetting occurred at least once in 11.65% of our total sample and was at least a weekly occurrence in 4.3%. Nocturnal enuresis was clearly reported to occur in more males (15.%) than females (7.9%), to occur in more subjects having chronic medical and ENT allergy problems (9.5%) than in subjects without such problems (8.7%), and to occur in more 5- to 8-year-olds (6.7%) than in 9- to ll-year-olds (0%) or in teenagers (1.4%). In children between 3 years and 15 years Anders and Weinstein (197) reported a range of occurrence of bedwetting from 5% to 17% of a child population. The prevalence of bedwetting in 4- to 5-yearolds is claimed to be 10% to 15%; in 1-year-olds 3%; in adults 1% (Kales and Kales, 1974). Our data reflect the same general trend toward a much diminished frequency of bedwetting in adolescent years. However our higher frequency of occurrence in 9- to ll-yearolds is not found in literature surveys. The literature reports of increased bedwetting in males (Ablon and Mack, 1979) is supported. The additional findings of a greater prevalence of bedwetting in subjects with chronic medical problems and ENT allergies may be secondary to some of the primary medical disorders or psychological reactions to the medical conditions. Bixler et al. (1979) found the following percentages for current or past sleep disorders in a total population of adults: nightmares 11.%, sleeptalking 5.3%, sleepwalking.5%, and bedwetting.1%. These figures were much lower than the percentages we found for the same sleep disorders that were current in our child and adolescent population. Two sleep disorders, narcolepsy and primary hypersomnia, remain relatively unchanged throughout the life of the individual. A significant number of subjects with these disorders have childhood onset. In a study of adult narcoleptics 59% were found to have had the onset of symptoms prior to age 15 (Yoss and Daly, 1960). In our study it was impossible to make an accurate diagnosis of narcolepsy without interviewing the subjects directly to explore the subjective experiences associated with various symptoms. Nineteen (6.1%) subjects were regarded by their mothers to have some degree of irresistible sleepiness and 10% of senior high-school students manifested this problem. Some of these subjects may have had the early signs of narcolepsy and in some cases the parents may have

5 SLEEP DISORDERS AND SLEEP BEHAVIORS exaggerated the degree of irresistible sleepines. Nevertheless only subjects had cataplexy-like symptoms and 4 subjects had sleep paralysis. However, none of these subjects had irresistible urges to sleep so that the validity of the reporting might be in doubt. In addition the probable prevalence rate of narcolepsy is 0.03% of a total population (Zarcone, 1973) and in our sample this rate would not equal one subject. Sleeptalking is defined as a type of parasomnia and it occurs in association with sleepwalking or in transition from stage 4 sleep (Anders and Weinstein, 197). We found it to be the most frequently occurring sleep behavior (44% of our sample talked in their sleep at least one time). It was not significantly related to age, sex, SES, or medical problem variables. Restless sleeping was reported by MacFarlane et al. (19) to occur in % of males and 16% of females at age 11 years and to decrease to 11% of males and 0% of females at age 14 years. Our finding of 34.6% of subjects having some restless sleeping seems high but the daily occurrence in 0.4% of subjects is somewhat closer to the literature reports. In addition our definition of restless sleep was limited to "moving around in bed a lot." Thus the term "restless' has a somewhat different connotation. Restless sleeping was significantly associated with SES classes IV and V which may indicate an environmental influence affecting the degree of motor activity in a child's sleep or a greater awareness of restless sleep patterns by parents in SES classes IV and V. Teeth grinding (bruxism) is probably a partial arousal phenomenon but it occurs primarily during stage sleep (Karacan et al., 1973). It was reported by Kanner (1957) to occur in % of all children attending psychiatric clinics at Johns Hopkins Hospital. Our finding that 15.% of the normal population has been observed to grind their teeth during sleep probably indicates a more systematic search for the behavior than a true difference. Bruxism was significantly more prevalent in the 5- to 8-year-old population (4%) than in a teenage population (10.1%). Teenagers were not asked to complete questionnaires in our study because a high return rate was not anticipated and this would have reduced the return rate expected from the parents. Mothers of teenagers may not be completely aware of their children's sleep patterns although they often asked their teenagers about sleep patterns they were not sure of. On the other hand teenagers cannot observe their own sleep behaviors and would not know what to report unless someone else observed their behaviors. Variations in prevalence of certain sleep behaviors were closely associated with age grouping of subjects. Thus younger children not unexpectedly were more 387 likely to be fearful of the dark, to require bedtime security objects, and to have bedtime rituals. These behaviors in addition to bedwetting and teeth grinding seemed to have some relationship to developmental or maturational phenomena. There were also variations in the prevalence of sleep behavior associated with differences in SES groupings of subjects. The children and adolescents classified as SES IV and V were more likely to be afraid of going to sleep, to experience daytime drowsiness, to be restless sleepers, to awaken during the night, and to snore. It seemed logical to explain these differences on the bases of environmental circumstances that may be different in the child's sleeping room or sleeping situation secondary to SES differences. It was interesting that a prevalence study of sleep disorders in adults found a significantly higher frequency of difficulty falling asleep in lower SES individuals (Bixler et al., 1979). Chronic medical problems and ENT allergies may also exert an influence on the prevalence of some sleep behaviors. Subjects having these medical problems were more likely to be fearful of the dark, to require bedtime security objects, to have bedtime rituals, and to bedwet. The prevalence of some of these behaviors were jointly influenced by SES as well as age. However it would not be unexpected for lower SES subjects to also have more chronic medical problems as a consequence of SES. Bixler et al. (1979) also noted that nightmares, insomnia, and hypersomnia were more frequently associated with persistent or recurrent health problems. There were few sleep behaviors that showed variations in prevalence dependent upon sex difference. Bedwetting has been associated with males probably as a consequence of genetic factors. The fact that girls tended to report more dreams than males probably can be explained on the basis of girls' greater sociability. Sleep patterns have been studied in normal adolescents (Karacan et al., 1975; Price et al., 1978; Williams et al., 197). Price et al. (1978) surveyed 11th and 1th grade students concerning sleep problems and they found that 37.6% of the students reported occasional sleep disturbances (i.e. difficulty falling asleep and frequent night time awakenings). Sleep laboratory studies by Karacan et al. (1975) revealed that total sleep time diminished as pubertal boys and girls became teenagers. Anders et al. (1978) examined symptoms of daytime sleepliness in 18 fifth and sixth grade school children. About 0% of his subjects required 30 minutes or longer to fall asleep but only.4% had significant symptoms of pathological sleepiness. The preadoles-

6 388 JOHN F. SIMONDS AND HUMBERTO PARRAGA cent rarely napped but daytime sleepiness increased in adolescent subjects and was associated with a significant discrepancy between school night and nonschool night total sleep time (Anders et al., 1980). School and social pressures as well as neuroendocrinological changes were linked to these adolescent sleep patterns (Anders et al., 1980). In our studies 9% of the subjects had daytime drowsiness at least once and this was more frequent in teenagers than nonteenagers. About 4.9% of all subjects had daytime drowsiness at least weekly. Daytime naps occurred in about 15% ofthe subjects. The greatest likelihood of napping occurred in 15- to 18-yearolds (.7%). Thus our data supported the concept of daytime drowsiness being more frequent in adolescents and perhaps daytime naps are attempts to compensate for sleep needed. Summary This study showed that the prevalence of sleep behaviors and sleep disorders often depended upon the age, sex, SES, and medical condition ofthe subject. Only a few sleep behaviors differed in frequency between boys and girls. Many behaviors were found in significantly greater numbers of younger children which would suggest a developmental or maturational phenomenon. However the frequency of some behaviors was significantly associated with two or three variables at the same time, suggesting developmental, biological, environmental factors may interact as multiple variables. The prevalence of sleep behaviors in psychiatric population should be compared with normal populations before any definitive conclusions can be made about particular sleep behaviors being more prevalent in emotionally disturbed populations. References ABLON, S. & MACK, J. (1979), Sleep disorders. In: Basic Handbook of Child Psychiatry, Vol., ed. J. Noshpitz. New York: Basic Books, pp AMERICAN PSYCHIATRIC ASSOCIATION (1980), Diagnostic and Sta tistical Manual of Mental Disorders, Ed. 3. Washington, D.C.: APA. ANDERS, T. & WEINSTEIN P. (197), Sleep and its disorders in infants and children; a review. Pediatrics, 50: CARSKADON, M., DEMENT, W. & HARVEY, K. (1978), Sleep habits of children and the identification of pathologically sleepy children. Child Psychiat. Hum. Develpm., 9: (1980), Sleep and sleepiness in children and adolescents. Pediat. Clin. N. Amer., 7:9-43. BIXLER, E. 0., KALES, A., SOLDATOS, C., KALES, J. & HEALEY, S. (1979), Prevalence of sleep disorders in the Los Angeles metropolitan area. Amer. J. Psychiat., 6: HERTZMAN, J. (1948), High school mental hygiene survey. Amer. J. Orthopsychiat., 18: KALES, A. & KALES, J. (1974), Sleep disorders; recent findings in the diagnosis and treatment of disturbed sleep. New Engl. J. Med., 00: KALES, J., JACOBSON, S. & KALES, A. (1968), Sleep disorders in children. In: Progress in Clinical Psychology, Vol. 8, ed. L. Abt and B. Reiss. New York: Grune & Stratton, pp KANNER, L. (1957), Child Psychiatry. Springfield, Ill.: Charles C Thomas, pp KARACAN, 1., SALIS, P. & WILLIAMS, R. (1973), Clinical disorders of sleep. Psychosomatics, 14: ANCH, M., THORNBY, J., OKAWA, M. & WILLIAMS, R. (1975), Longitudinal sleep patterns during pubertal growth; four year followup. Pediat. Res., 9: KRAMER, M. (1979), Dream disturbances. Psychiat. Ann., 9: LAPOUSE, R. & MONK, M. (1959), Fears and worries in a representative sample of children. Amer. J. Orthopsychiat., 9: MACFARLANE, J. W., ALLEN, L. & HONZIK, M. R. (19), A Devel opmental Study of the Behavior Problems of Normal Children between 1 Months and 14 Years. Berkeley, Calif.: University of California Press. MYERS, J. & BEAN, L. (1968), A Decade Later: A Followup of Social Class and Mental Illness. New York: John Wiley & Sons. PRICE, V., COATES, T., THORESEN, C. & GRINSTEAD, O. (1978), Prevalence and correlates ofpoor sleep among adolescents. Amer. J. Dis. Child., : SHIRLEY, H. AND KAHN, J. (1958), Sleep disturbance in children. Pediat. Clin. N. Amer. 5: WILLIAMS, R., KARACAN, 1., HURSCH, C. & DAVIS, C. (197), Sleep patterns of pubertal males. Pediat. Res., 6: Yoss, R. & DALY, D. (1960), Narcolepsy in children. Pediatrics, 5: ZARCONE, V. (1973), Narcolepsy. New Eng. J. Med., 88: