A new study conducted by researchers at Old Dominion University, Eastern Virginia Medical School and Virginia Commonwealth University compared auto crash rates over two years at Chesterfield and Henrico counties and found a correlation between crashes involving teen drivers and early school start times.

The two Central Virginia counties begin classes about an hour and a half apart. The study concluded that Chesterfield County, where high school begins at 7:20 a.m., had a significantly higher rate of crashes among teen drivers than Henrico County high schools, which start classes at 8:45 p.m.

The study is the latest to suggest that early school start times are challenging for teens. As a result, a growing number of school systems are rethinking their early high school start times.

Mariana Szklo-Coxe, an associate professor in the School of Community and Environmental Health at ODU's College of Health Sciences, worked closely with Dr. Robert Vorona, lead author and associate professor of internal medicine in the sleep division at EVMS, on this research as well as a prior study published in the Journal of Clinical Sleep Medicine, in 2011.

"We believe our results and conclusions regarding increased teen car crashes in counties with earlier school start times are strengthened," Szklo-Coxe said, "as this is a replication study and in light of the stability of our findings over four sequential years."

The Virginia Department of Motor Vehicles supplied the researchers with data from the two counties on weekday crashes and time-of-day for 16- to 18-year-olds and adult drivers for school years 2009-2010 and 2010-2011.

Chesterfield teens had a statistically higher crash rate of 48.8/1,000 licensed drivers versus Henrico's 37.9/1,000 for 2009-2010. For 2010-2011, Chesterfield's 16- to 17-year-olds had a crash rate of 53.2 per 1,000 versus 42 per 1,000 in Henrico. There was no discernible difference in crash rates among adult drivers in the two jurisdictions during either school year.

"Importantly, the significant differences in car crashes between counties with different school start times were observed for teen drivers only, not adults, further suggesting early start times could be an important potential contributor to preventable auto crashes in teens, which is a significant cause of premature death and morbidity in this population," Szklo-Coxe said.

Data for both studies came from the Virginia Department of Motor Vehicles. Among other things, the study also reviewed police-reported crash causes that showed significantly more instances where teen drivers from Chesterfield ran off the road to the right - a common finding in crashes where inadequate sleep is suspected.

"Our latest data can be used to further help inform policymakers," Szklo-Coxe said.

The findings closely resemble those from a 2011 study of teen drivers in Chesapeake and Virginia Beach, also conducted by Szklo-Coxe and Vorona. The 2011 study used data from 2007-2008. The latest study appears in the Nov. 15 issue of Journal of Clinical Sleep Medicine as the lead article

"More and more data suggest that insufficient sleep is common in our teens and that early high school start times contribute to teens' reduced sleep," Vorona said. "Insufficient sleep appears to have deleterious consequences such as decrements in mood and increased risk-taking, impaired academics and increased crash rates."

The issue of early start time crash rates among teens is a growing issue among schools.

In October, Fairfax County's school board approved a new initiative that will push back the first class of the day in its 22 high schools and three secondary schools to 8 a.m. or later. "The growing body of research of the health benefits of adolescents has become so clear and compelling, we felt that we had to make a change," said board chairman Tammy Derenak-Kaufax, after the 11-1 decision. Other Virginia jurisdictions are also now considering delaying high school start times.