APOE Polymorphism, Obstructive Sleep Apnea, and Cognitive Function

Objective  Obstructive sleep apnea (OSA) is associated with the apolipoprotein E ε4 polymorphic allele ( APOE ε4 ) and with worse cognitive function. However, the influence of APOE ε4 on cognitive function in patients with moderate-to-severe OSA is controversial. The present study evaluated the influence of APOE ε4 polymorphism and cognitive function in sedentary OSA patients with no other major comorbidities. Materials and Methods  In total, 55 middle-aged patients underwent conventional nocturnal polysomnography, APOE ε4 polymorphism genotyping, cognitive evaluation (attention, inhibitory control, frontal functions, processing speed, and episodic memory), and they filled out the International Physical Activity Questionnaire. Results  Overall, 13 patients had no or mild OSA, and 42 had moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥ 15 events/h of sleep) and APOE ε4 was present in 7.7% and 21.4% of the patients in each group respectively. Among patients with moderate-to-severe OSA, the sleep parameters were similar in the groups of APOE ε4 carriers and noncarriers. Compared with patients with no or mild OSA, the cognitive parameters were worse for processing speed (Digit Symbol Test) and attention (Stroop Color Word Test, SCWT-Part 2) among the patients with moderate-to-severe OSA. The difference was present even after the exclusion of APOE ε4 carriers. Among patients with moderate-to-severe OSA, APOE ε4 carriers presented worse episodic memory, evaluated through the Rey Auditory Verbal Learning Test, than APOE ε4 noncarriers. Conclusion  Moderate-to-severe OSA is associated with poor cognitive function that is further impaired by the presence of APOE ε4 polymorphism.