To clarify the actual feature of the sleep problems in adolescence from the points of view sleep loss, circadian rhythm, and development, the survey for five years was performed on 523 students in a College of Technology. The survey results were analyzed in regard to the Sleep Habits Scales and the Life Habits Scales. These scales were (1) Long sleeper-Short sleeper, (2) Good sleeper-Poor sleeper, (3) Sleep phase advanced type-Sleep phase delayed type, (4) Morningness-Eveningness, (5) Regnlar sleeper-Irregular sleeper, (6) Sleep satisfaction type-Sleep dissatisfaction type. Sleep length was shortened with advancements in grade. The irregularity and the delay of sleep phase increased with advancements in grade. Furthermore, approximately 5-10 percents of each grade student were screened as the persons who had some sleep disturbances or sleep problems. The present results suggest that the sleep problems (irregularity and phase delay) of adolescence apt to increase with advancements in grade
