There are recent meta-analyses showing higher risk of motor vehicle accidents (MVA) in those with obstructive sleep apnea (OSA), and a lower risk of MVA with CPAP therapy. However, the conclusions from these studies is somewhat limited due to possibly faulty research designs. In other words, it's still uncertain how much risk OSA imparts and if CPAP really reduces that risk. However, this study, recently in the Sleep Journal, set out to determine just that, using a well designed protocol. It was a retrospective study of almost 1500 drivers in Sweden. The results showed that there was a 2.5 fold increase in risk of MVA in patients with OSA. The risk was highest in older drivers. Also, risk was highest in those with high subjective sleepiness, but the risk did not depend on OSA severity. And the incidence of MVA was reduced by 70% among patients that used their CPAP at least 4 hours per night. Interestingly, risk of MVA was increased by 54% among those that used CPAP less than 4 hours per night.
The authors concluded that because CPAP therapy can improve sleep quality and overnight oxygenation, it could improve alertness and driving performance - leading to less MVA's.