Washington, June 10 : A new study has shown that high school students with a delayed school start time are more likely to sleep longer, and less likely to feel sleepy during daytime.
Authored by Zaw W. Htwe, MD, of Norwalk Hospital's Sleep Disorders Center in Norwalk, Conn., the study focused on 259 high school students who completed the condensed School Sleep Habits Questionnaire.
Before 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.
The study showed that 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.
Researchers found that 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 teens get nine hours of nightly sleep.
The study has been presented at SLEEP 2008, the 22nd Annual Meeting of the Associated Professional Sleep Societies (APSS).