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.

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.

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.

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.