Impact of Sleep Quality on Cognitive Function in Elderly Patients With Alzheimer’s Disease

OBJECTIVE: This study aimed to analyse the effect of sleep quality on cognitive function in elderly patients with Alzheimer's disease (AD). METHODS: This retrospective study extracted clinical data from the hospital's electronic medical record system for elderly patients with AD admitted to the Departments of Neurology or Geriatrics between June 2022 and June 2024. Cognitive function was assessed using the MiniMental State Examination (MMSE), subjective sleep quality was evaluated with the Athens Insomnia Scale (AIS) and objective sleep architecture parameters were measured via overnight polysomnography (PSG). Participants were stratified into mild and moderate-to-severe cognitive impairment groups according to their MMSE scores. General characteristics and sleep-related indicators were compared between the two groups. A binary logistic regression model was employed to analyse independent factors influencing cognitive impairment severity. In this model, cognitive impairment severity served as the dependent variable, and PSG parameters and AIS score served as the core independent variables. Adjustments were made for potential confounding factors, including age, gender, years of education, disease duration, Hospital Anxiety and Depression Scale (HADS) scores and Instrumental Activities of Daily Living Scale (IADL) scores. RESULTS: The cohort comprised 61 (40.67%) moderate-to-severe and 89 (59.33%) mild impairment patients. Compared with the mild impairment group, the moderate-to-severe group showed significantly poorer subjective (higher AIS) and objective sleep profiles, including reduced total sleep time, efficiency, and N2/N3 sleep and increased N1 sleep, latency and awakenings (p < 0.05). Adjusted regression identified the N3 stage/total sleep time ratio as a protective factor (odds ratio [OR] = 0.720, 95% CI: 0.576-0.900, p = 0.004) and the AIS score (OR = 1.850, 95% CI: 1.405-2.434, p < 0.001) and number of awakenings (OR = 3.101, 95% CI: 1.879-5.116, p < 0.001) as independent risk factors. CONCLUSION: In elderly patients with AD, impaired objective sleep architecture and subjective insomnia are significantly associated with poor cognitive function. This study highlighted sleep parameters as potential indicators for cognitive status assessment.