Sleep apnea impairs driving, even in alert drivers

NEW YORK (Reuters Health) - In driving tests, French investigators found that people with sleep apnea had longer reaction times while driving, took longer to stop, and were more likely to crash into obstacles.

But once people underwent treatment for their sleep-disordered breathing, their driving skills improved significantly, Dr. S. Mazza of Grenoble University Hospital and colleagues found.

In sleep apnea, a person wakes up repeatedly during the night due to a partial or complete airway collapse that obstructs breathing. The condition causes daytime sleepiness, and has been linked to impaired driving and greater accident risk. But to date, the only assessment of sleep apnea patients' driving skills has been through driving simulators.

To get a better sense of how sleep apnea affects driving skills in the real world, Mazza and colleagues had 20 sleep apnea patients and 20 individuals without the condition perform a series of tests on a road safety platform consisting of two one-way tracks 150 meters long. Study participants drove onto the platform and had to brake to avoid a jet of water.

Participants with sleep apnea took a half-second longer, on average, than the controls to stop when the water jet appeared. This means a person traveling at 130 kilometers per hour (about 81 miles per hour), the top speed permitted on French highways, would take 18 meters or nearly 20 yards longer to stop. People with sleep apnea also collided with the water jet obstacle twice as often as those without the condition.

While lab tests found that the sleep apnea patients were not sleepier than the controls, and did not have attention deficits, they did have a more difficult time dividing their attention between two tasks.

Ten of the sleep apnea patients were then retested after three months of treatment with continuous positive airway pressure or CPAP, in which a mask delivers oxygen during sleep to keep the airways open.

After treatment, their stopping distances and reaction times were no different from those of the healthy controls.

Sleep experts have questioned whether treatment is necessary for sleep apnea patients who don't report daytime sleepiness, Mazza and colleagues note. They say their findings show that, even without sleepiness, people with sleep apnea have impairments in attention that can significantly affect driving ability.

"Simple strategies" now available could help identify attention problems and driving impairments in these patients, and should be investigated further.

"Public health policy should take into account the impact of obstructive sleep apnea syndrome on driving ability in order to reduce traffic accidents," they conclude.

SOURCE: European Respiratory Journal, November 2006.