Objective: To assess the prevalence of obstructive sleep apnea (OSA) in patients with mild-moderate Alzheimer's Disease (AD) and to evaluate cognitive characteristics according to the severity of OSA.
Methods: Patients with mild-moderate AD, recruited prospectively from a cognitive impairment unit, underwent overnight polysomnography. OSA was defined as an apnea-hypopnea index > 5/h. AD severity was assessed using the Mini-Mental State Examination and extensive neuropsychological battery. Epworth Sleepiness Scale and APOE status were analyzed.
Results: The cohort included 128 patients with a median [IQR] age of 75.0 [72.0;79.2] years and 57.8% were women. OSA was diagnosed in 116 subjects (90.6%). The distribution of mild, moderate and severe severity of OSA was 29 (22.7%), 37 (28.9%) and 50 (39.1%), respectively. Regarding sleep symptoms, the cohort showed normal values of daytime sleepiness (median EES score 5 [3, 8]), while nycturia (89.1%) and snoring (71.1%) were the most common symptoms. Participants with severe OSA included a higher proportion of older men, were associated with snoring and sedentariness. No significant differences in cognitive assessment were found between patients with and without severe OSA in any of the domains. The prevalence of APOE ε4 was not significantly different between patients with and without severe OSA.
Conclusion: There was a high prevalence of OSA in patients with mild-moderate AD. OSA was not associated with sleepiness or worse cognitive function. APOE ε4 was not related to the presence or severity of OSA. Further longitudinal studies will be required to evaluate whether OSA impairs cognitive evolution in AD patients.
Keywords: Alzheimer’s disease; Cognition; Obstructive sleep apnea; Prevalence; Sleep-disordered breathing.