Patrones De Sueño Korea

DOI: 10.3345/kjp.2011.54.1.29

Korean J Pediatr 2011;54(1):29-35

Original article

29

Sleep patterns and school performance of Korean

adolescents assessed using a Korean version of the

pediatric daytime sleepiness scale

Purpose: Korean adolescents have severe nighttime sleep deprivation

and daytime sleepiness because of their competitive educational

environment. However, daytime sleep patterns and sleepiness have

never been studied using age-specific methods, such as the pediatric

daytime sleepiness scale (PDSS). We surveyed the daytime sleepiness

of Korean adolescents using a Korean translation of the PDSS.

Methods: We distributed the 27-item questionnaire, including the

PDSS and questions related to sleep pattern, sleep satisfaction, and

emotional state, to 3,370 students in grades 5-12.

Results: The amount of nighttime sleep decreased significantly with

increasing age. During weekday nights, 5- 6th graders slept for 7.95±1.05

h, 7-9th graders for 7.57±1.05 h, and 10-12th graders for 5.78±1.13 h.

However, the total amounts of combined daytime and nighttime sleep

during weekdays were somewhat greater, 8.15±1.12 h for 5- 6th graders,

8.17±1.20 h for 7-9th graders, and 6.87±1.40 h for 10-12th graders. PDSS

scores increased with age, 11.89±5.56 for 5- 6th graders, 16.57±5.57 for

7-9th graders, and 17.71±5.24 for 10-12th graders. Higher PDSS scores

were positively correlated with poor school performance and emotional

instability.

Conclusion: Korean teenagers sleep to an unusual extent during the

day because of nighttime sleep deprivation. This negatively affects

school performance and emotional stability. A Korean translation of

the PDSS was effective in evaluating the severity of daytime sleepiness

and assessing the emotional state and school performance of Korean

teenagers.

Key words: Sleep deprivation, Adolescent, Sleepiness, Emotions,

School performance

Seonkyeong Rhie, M.D., Sihyoung Lee, M.D.,

and Kyu Young Chae. M.D.

Department of Pediatrics, CHA Bundang Medical

Center, CHA University, Seongnam, Korea

Received: 11 September 2010, Revised: 12 October 2010

Accepted: 16 November 2010

Corresponding author: Kyu Young Chae, M.D.

Department of Pediatrics, CHA Bundang Medical Center,

CHA University, 351, Yatap-dong, Bundang-gu, Seongnamsi,

Gyeonggi-do 463-712, Korea

Tel: +82.31-780-5230, Fax: +82.31-780-5239

E-mail: barnabas@cha.ac.kr

The summary of this paper was presented at the 59th

Autumn meeting of the Korean Pediatric Society in 2009.

Copyright © 2011 by The Korean Pediatric Society

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/

3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

30 S Rhie, et al. • Sleep patterns & PDSS in Korean adolescent

Introduction

Sufficient sleep is essential for the physical growth, emotional

stability, and maintenance of cognitive function in adolescence1).

Excessive daytime sleepiness attributable to sleep deprivation or a sleep

disorder is known to reduce work efficiency and to cause traffic and

industrial accidents2). Chronic sleep deprivation among adolescents

inhibits pre-frontal lobe functions, such as working memory, judgment,

and insight, resulting in impairment of learning and school

performance. The increased emotional lability and depression

associated with sleep deprivation also makes it difficult for sleepdeprived

students to adjust to school life3-12).

Modern-day adolescents get much less sleep than was the case in

the 20th century. In particular, excessive use of the internet and other

media has reduced sleep time13, 14). It was noted that the average sleep

duration of adolescents was 7.6-8.6 hours, 0.4-1.4 hours less than

what is needed5). Adolescents in higher grades usually get even less

nighttime sleep and experience more marked differences when sleep

duration on weekdays and weekends is compared10, 15-17). In Japan,

where the educational environment is similar to that of Korea, sleep

duration was 7.2-7.8 hours among 10-12th graders, thus shorter than

that of adolescents in the West18).

Korean parents place great emphasis on education, and adolescents

often take extra classes or private lessons, contributing to chronic sleep

deprivation. In particular, 11-12th graders in Korea have an average

nighttime sleep duration of 4.9-5.5 hours, much less than students

in Japan, where parents also place great emphasis on education19-21).

This severe chronic nighttime sleep deprivation can lead to excessive

daytime sleepiness and lack of attention in class, an increase in

emotional lability and depression, and may also be associated with

increases in violence and suicide among adolescents22). A previous

report indicated that about 70% of Korean adolescents were worried

about nighttime sleep quality and over 20% complained of excessive

daytime sleepiness. However, the daytime sleep patterns and

sleepiness of Korean adolescents have never been studied using an

age-specific measure of sleepiness, such as the well-known pediatric

daytime sleepiness scale (PDSS)23).

In the present study, we examined the sleep patterns and daytime

sleepiness of Korean adolescents using a Korean version of the PDSS

and studied the relationship between PDSS data, and adjustment to

school life and academic achievement.

Materials and methods

We administered sleep questionnaires to 3,379 students in grades

5-12, in their classrooms, in schools situated in the southern region

of Gyeonggi-do and Seoul (Korea), from May to November 2009.

A total of 3,201 students successfully completed the survey (5-6th

grade: 532, 7-9th grade: 302, 10-12th grade: 2545). The male/female

ratio was about equal for students in grades 5-9. However, more boys

than girls were in grades 10-12 (79.6% boys; 20.4% girls) (Table 1).

The entire sleep questionnaire contained 27 items, and included

four questions on sleep/wake patterns, two questions on time spent

at school,

...