A new study has found that just one hour delay in school start time can help improve sleep in adolescents and reduce risk of auto accidents.
The researchers found that when school started one hour later students had on an average 12 minutes (grade nine) to 30 minutes (grade 12) more nightly sleep.
The percentage of students who got at least eight hours of sleep per weeknight increased significantly from 35.7 percent to 50 percent; students who got at least nine hours of sleep also increased from 6.3 percent to 10.8 percent.
The average amount of additional weekend sleep, or "catch-up sleep," decreased from 1.9 hours to 1.1 hours. Moreover, the daytime sleepiness also decreased.
The average crash rates for teen drivers in the study dropped 16.5 percent, compared to the two years prior to the change after the change in school start time.
The survey concerning the sleep habits of students from a county-wide school district in Kansas was distributed before and after a change in school start times.
In April 1998, (Year One), a total of 9,966 students (66 percent of the total population of middle and high-school students enrolled in the county) from grades six to 12 completed questionnaires concerning their sleep habits on school nights and non-school nights and various aspects of daytime functioning.
Barbara Phillips, MD, director of the UK Healthcare Good Samaritan Sleep Center in Lexington, Ky. attributed the decrease in auto accidents after the change in school start times to improved vigilance, as the students were able to get more sleep.
"It is surprising that high schools continue to set their start times early, which impairs learning, attendance and driving safety of the students," said Phillips.
The authors report that both social and biological pressures appear to cause a shift in sleep patterns during the transition to adolescence, with the result that adolescents stay up progressively later.
As a result, adolescents get an inadequate amount of sleep due to early school start times, which increases their daytime sleepiness and may in turn increase their odds of crashing their vehicles while driving.
The study appears in The Journal of Clinical Sleep Medicine (JCSM).