Attention and executive function impairments in obstructive sleep apnea are associated with decreased sleep spindles

Introduction Sleep spindles play a key role in sleep-mediated cognitive processes. Cognitive functions are well-known to be affected in obstructive sleep apnea (OSA). Here, we analyzed attention and executive functions in patients with OSA and investigated the relationship between sleep spindles and cognitive abilities. Methods Sixty patients with OSA (18–65 years, 19 females and 41 males) and a control group ( n = 41) including age-and sex-matched healthy individuals were consecutively and prospectively enrolled. All participants had a full-night polysomnography, and sleep spindles were analyzed using a semi-automated program. For the evaluation of short-term memory, attention and executive functions, Stroop test, forward and backward digit span tests were applied to all participants upon awakening following polysomnography. Results Scores of forward and backward digit span and Stroop tests were worse in OSA patients in compared to those in controls. Mean density of sleep spindles was decreased in OSA patients than those in controls ( p = 0.044). A positive correlation was found between fast sleep spindle frequency and forward digit span ( r = 2.222; p = 0.038) and backward digit span test scores ( r = 2,157; p = 0.042) in OSA patients. In patients with moderate to severe OSA, sleep spindle density was positively correlated with forward ( r = 2.323, p = 0.029) and backward ( r = 2.500, p = 0.016) DSTs, and the duration of sleep spindles had positive correlation with backward DST ( r = 2.452, p = 0.010). Conclusion Our findings demonstrated that the disturbances in sleep spindle characteristics in OSA are associated with the cognitive impairments in attention, short-term memory, and executive functions, especially in patients with moderate to severe OSA.