Blackwell Science, LtdOxford, UK PCN Psychiatric and Clinical Neurosciences 1323-13162003 Blackwell Science Pty Ltd 574August 2003 1146 EDS in high school students C. Shin et al. 10.1046/j.1323-1316.2003.01146.x Original Article451453BEES SGML
Psychiatry and Clinical Neurosciences (2003), 57, 451–453
Short Communication
Short Communication
Sleep habits, excessive daytime sleepiness and school performance in high school students CHOL SHIN, MD, PhD, FCCP,1 JINKWAN KIM, MPH,1 SANGDUCK LEE, MD,2 YONGKYU AHN, PhD3 AND SOONJAE JOO, PhD4 1
Department of Respiratory Internal Medicine, Pulmonary Sleep Disorder Center, and 4Institute of Human Genomic Study, Ansan Hospital, Korea University Medical Center, Gyeonggi-Do 2Hana Otorhinolaryngology Clinic and 3Korean National University of Physical Education, Seoul, Korea
Abstract
A questionnaire survey was carried out to examine the sleep habits and excessive daytime sleepiness (EDS) of 3871 high school students with a mean age of 16.8 years in Korea. The results showed that mean total sleep time was 6.3 h/day for male students and 6.5 h/day for female students, which may be insufficient for adolescence during puberty. The overall prevalence of EDS (defined as an Epworth sleepiness scale score of >10) was 15.9% (14.9% for boys and 18.2% for girls). The prevalence of EDS increased significantly (P < 0.001) with a decline in school performance.
Key words
excessive daytime sleepiness, Korea, senior high school students, sleep habits.
INTRODUCTION Because excessive daytime sleepiness (EDS) has been associated with increased motor vehicle and workrelated accident, and decreased productivity,1,2 it is increasingly recognized as a significant public health problem. Few studies on EDS in adolescents, however, have been performed in Asian countries and none have occurred in Korea. The purpose of the present study was to assess sleep habits and EDS, and its association with school performance in senior high school students in Korea.
METHODS A total of 11 schools were randomly selected using the official directory of public and private senior high schools in the southern part of Seoul, Korea. Institu-
Correspondence address: SoonJae Joo, Institute of Human Genomic Study, Ansan Hospital, Korea University Medical Center, 516 Gojan-Dong, Danwon-gu, Ansan-Si, Gyeonggi-Do 425-707, Korea. Email:
[email protected] Received 13 September 2002; revised 16 December 2002; accepted 23 December 2002.
tional approval for the survey was granted in 10 schools. One school, however, refused to participate in the study. A questionnaire study therefore was carried out in a sample of 4781 students in the 11th grade from each of 10 schools from September 2001 to December 2001. Questionnaires were filled out by the students during school hours in the presence of skilled investigators, who explained the study procedures. Participation was on a voluntary and anonymous basis without teacher input. School performance was defined as either a high or low grade depending on whether students were ranked among the top or bottom quartiles of their class, respectively, based on final exams of the first semester in the 2001 academic year. Student rankings in the middle two quartiles were defined as being of moderate performance. The c2 test was applied to compare the item scores of the Epworth sleepiness scale (ESS) between the EDS group and non-EDS group, and to examine the association of prevalence of EDS with school performance.
RESULTS Data from 3871 students (2703 boys and 1168 girls) were collected, representing a response rate of 81%.
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In the present study 34.7% of all students went to bed after midnight and 52.5% got up before 7:00 a.m. As a result, mean total sleep time was 6.3 h/day for male students and 6.5 h/day for female students. The overall prevalence of EDS, defined as an ESS score of >10, was estimated to be 15.9% (14.9% for boys and 18.2% for girls). The mean ESS score for the EDS group (group B in Table 1) was 13.1 ± 2.8 (SD), which was much higher than that for the non-EDS group (group A; 5.8 ± 2.5). As shown in Table 1, these two groups also differed significantly (P < 0.001) in their item-scores for each item. In all eight situations the EDS students were much more likely than non-EDS students to doze. Compared with non-EDS students, the situations in items 4 and 8 (as a passenger in a car for an hour without a break; and in a car while stopped for a few minutes in the traffic) were the most soporific for the EDS students. Figure 1 shows the prevalence of EDS by school performance. The prevalence of EDS in all students with a low grade was 20.5%, which was significantly higher (P < 0.001) than in those with a moderate grade (14.2%) and those with a high grade (14.0%), respectively. Moreover, the prevalence of EDS in male students significantly increased (P < 0.001) with a decline in school performance. The highest (P < 0.001) prevalence of EDS was also shown in female students with a low grade.
DISCUSSION In the present study nearly one-third of students go to bed after midnight and more than 50% get up before 7:00 a.m. Thus, mean total sleep time of all students was 6.4 h/day, which may be insufficient for adolescence
Figure 1. Prevalence of excessive daytime sleepiness (EDS) by school performance. According to school performance, significant differences in the prevalence of EDS were found (c2, P < 0.001).
Table 1. Distribution of the ESS scores for the eight situations between EDS (n = 614) and non-EDS (n = 3257) students
Item
Situation
1
Sitting and reading*
2
Watching television*
3
Sitting, inactive in a public place*
4
As a passenger in a car for an hour without a break*
5
Lying down to rest in the afternoon when circumstances permit*
6
Sitting and talking to someone*
7
Sitting quietly after lunch without alcohol*
8
In a car, while stopped for a few minutes in traffic*
% subjects with item scores of 1 2 3
Group
0
A B A B A B A B A
25 8 43 15 67 21 23 4 12
58 35 50 49 30 44 50 20 37
14 33 6 26 3 25 21 40 37
3 24 1 10 0 10 6 36 14
B A B A B A B
2 88 44 64 16 45 7
10 11 34 29 35 37 21
30 1 16 6 34 12 32
58 0 6 1 15 6 40
ESS, Epworth sleepiness scale; EDS, excessive daytime sleepiness; group A, non-EDS students; group B, EDS students. *Significant differences in item-scores were found between groups A and B (P < 0.001).
EDS in high school students
during puberty.3 This insufficient sleep in adolescents may be due to the school schedules requiring them to wake up earlier, increased academic demands requiring them to stay up late, expanding social opportunities, and increased access to drugs and alcohol. Arakawa et al.4 also reported that bedtimes became significantly later, accompanied by significant increases in sleep debt as grade levels rose at junior high school in Japan. Although no significant difference in total sleep time between EDS and non-EDS students was found in the present study, it is recognized that EDS has been attributed in part to insufficient sleep, which may affect school performance of adolescent students. Our results also showed that the prevalence of EDS increased significantly (P < 0.001) with a decline in school performance. Whether interventions to modify EDS can improve academic performance in adolescents who have EDS warrants further study.
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ACKNOWLEDGMENT This work was supported by a grant (2000-n6) from Korea University Medical Science Research Center.
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