Teenage drivers who sleep later have fewer car accidents, a new study suggests.
Car crash rates in Chesterfield and Henrico counties in Virginia offered researchers a natural experiment. The adjacent counties near Richmond are almost identical in socioeconomic and ethnic characteristics, and in the percentage of roads with traffic congestion. But the high school day begins at 8:45 a.m. in Henrico, and at 7:20 a.m. in Chesterfield.
The rate of accidents among 16- to 18-year-old drivers in Chesterfield County in 2009-2010 was 48.8 per thousand, compared with 37.9 in Henrico County. In 2010-2011, the same trend was evident: 51.9 per thousand in Chesterfield and 44.2 in Henrico. The crash rate among adults over the same period fluctuated between 13 and 14 per thousand, with no difference between the two counties.
The study, in the November issue of The Journal of Clinical Sleep Medicine, gathered no information on other risky behaviors, sleep habits, vehicle type, or miles traveled in each county, factors that could have affected the results. And the lead author, Dr. Robert D. Vorona, an associate professor at Eastern Virginia Medical School, acknowledged that the study provides no proof of a causal effect.
Still, he said, “There is a growing literature that shows that early start times are a problem, and school systems should take a look at the data and seriously consider whether they should delay them.”
