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, 5-6(th) graders slept for 7.95±1.05 h, 7-9(th) graders for 7.57±1.05 h, and 10-12(th) 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 5-6(th) graders, 8.17±1.20 h for 7-9(th) graders, and 6.87±1.40 h for 10-12(th) graders. PDSS scores increased with age, 11.89±5.56 for 5-6(th) graders, 16.57±5.57 for 7-9(th) graders, and 17.71±5.24 for 10-12(th) 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.