The researchers found severe daytime sleepiness was one of the factors that raised the risk of road traffic accidents among drivers with sleep apnea.
Researchers from the Sahlgrenska Academy at the University of Gothenburg in Sweden report their findings in the journal SLEEP.
The American Academy of Sleep Medicine (AASM) estimates around 25 million adults in the US suffer from obstructive sleep apnea - commonly termed sleep apnea - a condition where breathing starts and stops during sleep, with the interruptions often accompanied by snorting and gasping.
People with sleep apnea may also get sleepy during the day because they do not feel sufficiently restored after a night of interrupted sleep.
Moderate to severe sleep apnea is usually treated with continuous positive airway pressure (CPAP) therapy to stop the throat closing during sleep.
Powered by a small pump, CPAP therapy continuously delivers compressed air through a mask covering the nose or both the nose and mouth.
'Strong evidence' that sleep apnea increases risk of traffic accidents
Lead investigator of the new study, Ludger Grote, associate professor at the Center for Sleep and Vigilance Disorders at the Sahlgrenska Academy, says:
"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."
Using data from the Swedish Traffic Accident Registry (STRADA), the team compared rates of traffic accidents among 1,478 sleep apnea patients attending clinical sleep laboratories and a control population of 635,786 driving license holders in Sweden.
Over a study period exceeding 10 years, they found 21,118 individuals with a record of at least one motor vehicle accident in the control population. They also found that 82 motor vehicle accidents occurred while a sleep apnea patient was at the wheel, with 56 accidents occurring in the 5 years before diagnosis and 26 in the year after diagnosis.
When they analyzed the data, the researchers found sleep apnea patients were nearly 2.5 times more likely to be the driver in a motor vehicle accident, compared with drivers in the general population.
Further analysis identified several factors that independently raised the risk of a traffic accident when sleep apnea patients were driving, such as severe daytime sleepiness, sleeping less than 5 hours a night or use of sleeping pills.
Apnea patients using CPAP effectively showed 70% reduction in higher risk of accidents
However, the analysis showed apnea patients who used CPAP therapy for an average of 4 hours a night or more showed a 70% reduction in the risk of having a motor vehicle accident while driving.
The researchers were able to assess how well the patients stuck to their CPAP therapy regime from data recorded on the CPAP device.
AASM president Dr. Timothy Morgenthaler says:
"Effective identification and treatment of sleep apnea is essential to reduce avoidable, life-threatening accidents caused by drowsy driving."
The AAA Foundation for Traffic Safety estimates that every year in the US, drowsy driving causes 328,000 motor vehicle accidents and 6,400 fatal crashes.
The ResMed Foundation, the Philips Respironics Foundation and the Swedish Heart and Lung Foundation funded the study.
In November 2014, Medical News Today reported another study that suggested sleep apnea is linked to impaired ability to exercise. Researchers from the University of California-San Diego found that people who suffer from sleep apnea may not be able to burn enough oxygen during strenuous aerobic exercise, compared with people who do not have the disorder.