FRIDAY, Aug. 18 (HealthDay News) -- Truckers with severe sleep apnea or who sleep less than five hours a night when they're at home are more likely than other truckers to experience sleepiness and impaired ability while driving, a U.S. study finds.

"In the United States, approximately 5,600 people are killed annually in crashes involving commercial trucks," study author Allan L. Pack, of the University of Pennsylvania, noted in a prepared statement.

"Falling asleep while driving is an important factor in serious crashes involving commercial vehicles, prompting the question, why?" he said.

This study concluded that obstructive sleep apnea and chronically insufficient sleep are two main reasons.

Pack and his colleagues tested hundreds of truck drivers for sleep apnea, sleepiness, and performance impairment.

"In this study, we showed that both subjective and objective sleepiness, as well as performance impairments, are common in our sample of commercial driver's license holders," Pack said.

"Chronic short sleep duration is a risk factor for subjective sleepiness, objectively measured sleepiness and performance impairments," he said. "The results for sleep apnea are less clear."

Among drivers with less than five hours of sleep, 49.5 percent had two or three performance impairments, Pack's team reported in the August issue of the American Journal of Respiratory and Critical Care Medicine.

The U.S. federal government needs to do more to reduce sleepiness in commercial truck drivers, the study authors said. This should include programs that identify "sleep-impaired" drivers through objective testing; pinpoint and treat drivers with severe sleep apnea and monitor their adherence to therapy; and promote increased sleep duration among truck drivers.

More information

The National Sleep Foundation has more about drowsy driving.