Bart Jansen

USA TODAY

WASHINGTON — Drivers who skimp on just a couple of hours of sleep nearly double the risk of a crash, making drowsy driving about as dangerous as drunken driving, according to a report released Tuesday.

A review of thousands of crashes resulting in injuries found drivers were 1.3 times more likely to be involved in accidents if they missed an hour of sleep and 1.9 times more likely if they missed two of the seven hours recommended daily, the AAA Foundation for Traffic Safety found.

About one-third of U.S. drivers get less than seven hours of sleep each night, according to the Centers for Disease Control and Prevention.

“Managing a healthy work-life balance can be difficult, and far too often, we sacrifice our sleep as a result,” said Jake Nelson, director of Traffic Safety Advocacy and Research for AAA. “Failing to maintain a healthy sleep schedule could mean putting yourself or others on the road at risk.”

Symptoms of drowsy driving include motorists having trouble keeping their eyes open, drifting across lanes of traffic or forgetting recent miles driven. In addition to getting plenty of sleep, AAA recommends drivers on longer trips schedule a break every two hours or 100 miles, avoid heavy food, travel with an alert passenger and take turns driving and avoid medications that cause drowsiness.

“You cannot miss sleep and still expect to be able to safely function behind the wheel,” said David Yang, executive director for the AAA Foundation for Traffic Safety.

The study covered 4,571 crashes from July 2005 to December 2007 when emergency medical services were dispatched and at least one vehicle was towed from the scene. It used data from the National Highway Traffic Safety Administration and information about crime-scene investigations that found drivers committed an illegal action or made a mistake.

The risk of a crash for sleep-deprived drivers increased steadily as sleep time decreased:

1.3 times for six to seven hours of sleep.

1.9 times for five to six hours of sleep.

4.3 times for four to five hours of sleep.

11.5 times for less than four hours of sleep.

The study might underestimate the risk of fatigue: It covered only crashes from 6 a.m. to midnight because data on accidents in the early morning hours were unavailable.

“Other studies have shown that the effects of sleep deprivation on attention and performance are greatest during the early morning hours,” the report noted.