A Swedish study suggests that obstructive sleep apnea is associated with a significantly increased risk of motor vehicle accidents.

Researchers found that patients with sleep apnea were nearly 2.5 times more likely to be the driver in a motor vehicle accident, compared with a control group of other drivers in the general population. The risk is reduced when sleep apnea is treated effectively using continuous positive airway pressure (CPAP) therapy.

"This study provides very strong evidence that obstructive sleep apnea patients have an increased traffic accident risk and that this risk can be modified if CPAP treatment is used adequately," Dr. Ludger Grote, principal investigator and senior author, said in a statement.

Further risk analysis found that severe excessive daytime sleepiness, a short sleep duration of 5 hours or less, and use of sleeping pills were independent predictors of increased crash risk in patients with sleep apnea. The study also found that the incidence of motor vehicle accidents was reduced by 70 percent among sleep apnea patients who used CPAP therapy for an average of at least 4 hours per night.

For the study, researchers studied more than 1,400 sleep apnea patients with a mean age of 54 years. Objective motor vehicle accident data were analyzed from the Swedish Traffic Accident Registry (STRADA).

The control population of 635,786 driver's license holders included 21,118 individuals with a record of at least one motor vehicle accident during the study period. Sleep apnea patients were involved in 82 motor vehicle accidents while driving during the study period, including 56 accidents in the five years prior to diagnosis and 26 accidents in the five years after diagnosis. Objective CPAP adherence data were obtained from the device at follow-up visits.

The findings are detailed in the journal Sleep.