Interhemispheric sleep depth coherence predicts driving safety in sleep apnea

Obstructive sleep apnea is associated with increased risk of car crashes; however, conventional measures of sleep apnea severity do not clearly identify those individuals who are at greatest risk. Here we tested whether, among individuals with sleep apnea, those with reduced interhemispheric sleep depth coherence, measured by correlation between right and left hemisphere odds ratio product, are at greater risk. The sample was derived from the Sleep Heart Health Study, a prospective observational cohort study, and included 1,378 adults with sleep apnea. The occurrence of a car crash was ascertained by a questionnaire administered 2 years after the sleep study, which asked about the occurrence of crashes during the year prior to questionnaire administration. We computed the sleep depth coherence from electroencephalograms recorded during baseline sleep studies and after 5 years. The weighted kappa coefficient and Bangdiwala's B were 0.34 and 0.59, respectively, indicating a fair to moderate stability over a 5-year interval. Multivariate logistic regression, adjusted for age, sex, race, body mass index and miles driven per year, was used to assess the risk of a car crash. Compared to the lowest quartile of sleep depth coherence (<0.86), individuals in the highest quartile (>0.93) had a 62% (95% confidence interval, 22%-81%) lower risk of an accident. Further adjustments for usual sleep duration and sleepiness did not meaningfully alter these findings. Higher interhemispheric sleep depth coherence is associated with significantly lower risk of motor vehicle crashes in individuals with sleep apnea. This suggests that high interhemispheric sleep depth coherence may be a marker of resistance to sleep apnea-related adverse neurocognitive outcomes.