High school students with a delayed school start time are more likely to take advantage of the extra time in bed, and less likely to report daytime sleepiness, according to a research abstract that will be presented on June 9 at SLEEP 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies (APSS).

The study, authored by Zaw W. Htwe, MD, of Norwalk Hospital's Sleep Disorders Center in Norwalk, Conn., focused on 259 high school students who completed the condensed School Sleep Habits Questionnaire. Prior to the delay, students reported sleeping a mean of 422 minutes (7.03 hours) per school night, with a mean bed-time of 10:52 p.m. and a mean wake-up time as 6:12 a.m.

According to the results, after a 40-minute delay in the school start time from 7:35 a.m. to 8:15 a.m., students slept significantly longer on school nights. Total sleep time on school nights increased 33 minutes, which was due mainly to a later rise time. These changes were consistent across all age groups. Students' bedtime on school nights was marginally later, and weekend night sleep time decreased slightly. More students reported "no problem" with sleepiness after the schedule change.

"Following a 40-minute delay in start time, the students utilized 83 percent of the extra time for sleep. This increase in sleep time came as a result of being able to 'sleep in' to 6:53 a.m., with little delay in their reported school night bedtime. This study demonstrates that students given the opportunity to sleep longer, will, rather than extend their wake activities on school nights," said Mary B. O'Malley, MD, PhD, corresponding author of the study.

It is recommended that adolescents get nine hours of nightly sleep.