People with obstructive sleep apnea are nearly five times as likely to get into car accidents in which people get hurt than their peers without the sleep-related breathing disorder, new research demonstrates.

And the more severe the sleep apnea, the greater their risk, Dr. Najib Ayas of the University of British Columbia in Vancouver, Canada and colleagues found.

People with obstructive sleep apnea wake several times each night due to blockage of their airways, and are known to be at greater risk of getting into car accidents because they are sleep-deprived and may doze off behind the wheel. But many studies have relied on patients’ own reports of car accident involvement, which may be unreliable, and few have gathered data on accident severity, Ayas and his team note in the June issue of Thorax.

Ayas and colleagues hypothesized that sleep apnea sufferers would be more likely to be involved in car crashes, especially severe crashes involving injury. To investigate, they looked at 783 people with suspected sleep apnea who had undergone overnight sleep studies called polysomnography to diagnose the presence and severity of sleep apnea. They compared provincial insurance records including information on any car crashes in the three years before people underwent the test to records for 783 people who did not have sleep apnea.

Among the sleep apnea patients, 252 crashes occurred, compared to 123 accidents for the control group. Overall, people with the condition were 2.6 times more likely to be involved in a car accident in the previous three years. The 140 people who had undergone polysomnography but didn’t have sleep apnea were no more likely to be involved in accidents than the control group.

Sleep apnea patients were also 4.8 times more likely to be involved in accidents involving personal injury, while those with severe sleep apnea were at 6.1-fold greater risk of such accidents than people who underwent polysomnography but didn’t have the condition. And while there were only 10 very severe accidents - for example, head-on collisions or crashes involving pedestrians or bicyclists - sleep apnea patients were behind the wheel in eight.

The main symptom of sleep apnea is loud snoring, even though most people who snore don’t have the condition, Ayas noted. Treatment with continuous positive airway pressure, in which a person wears a mask that pushes oxygen into the lungs, has been shown to reduce the risk of crashes and improve awareness in drivers with sleep apnea. Obesity is a risk factor for the condition, and losing weight, avoiding alcohol, and quitting smoking can also help.

“Increasing public awareness of the symptoms and risks of [obstructive sleep apnea] together with improved access to diagnosis and treatment is likely to confer major cost savings to society in addition to benefiting individual patients,” Ayas and colleagues conclude.

SOURCE: Thorax, June 2008.