Adolescent sleep patterns, circadian timing, and sleepiness at a transition to early school days

Study Objectives: This study examined effects on adolescent sleep patterns, sleepiness, and circadian phase of a school transition requiring an earlie r start. Design and Setting: Adolescents were evaluated in 9th and 10th grades; scho ol start time in 9th grade was 0825 and in 10th grade was 0720. Assessments at each point included 2 weeks of actigraphy and sleep diaries at home, fo llowed by a 22-hour laboratory evaluation, including evening saliva samples every 30 minutes in dim light for determination of dim-light salivary mela tonin onset phase (DLSMO), overnight sleep monitoring, and multiple sleep l atency test (MSLT). Participants: Twenty-five females and 15 males, ages 14 to 16.2 were enroll ed; 32 completed the study in 9th grade and 26 completed in 10th grade. Int erventions: Participants kept their own schedules, except that laboratory n ights were scheduled based upon school-night sleep patterns. Measurements and Results: According to actigraphy, students woke earlier on school days in 10th than in 9th grade, but they did not go to sleep earlie r and they slept less. DLSMO phase was later in 10th grade (mean = 2102) th an 9th grade (mean = 2024). Sleep latency on MSLT overall was shorter in 10 th (mean = 8.5 minutes) than in 9th (mean = 11. 4 minutes), particularly on the first test of the morning at 0830 (5.1 vs 10.9 minutes). Two REM episo des on MSLT occurred in 16% of participants in 10th grade; one REM episode occurred in 48%. When those with REM sleep on one or both morning MSLTs (n= 11) were compared to those without morning REM, significant differences inc luded shorter sleep latency on the first test, less slow wave sleep the nig ht before, and later DLSMO phase in those who had morning REM. Conclusions: Early start time was associated with significant sleep depriva tion and daytime sleepiness. The occurrence of REM sleep an MSLT indicates that clinicians should exercise caution in interpreting MSLT REM sleep in a dolescents evaluated on their "usual" schedules. Psychosocial influences an d changes in bioregulatory systems controlling sleep may limit teenagers' c apacities to make adequate adjustments to an early school schedule.