Association between polysomnography-measured sleep parameters and cognitive impairment in elderly patients with depression

Background: Limited research has explored the associations between sleep disturbances (SD) and cognitive impairment (CI) in elderly patients with depression, particularly by incorporating polysomnography (PSG) to assess sleep quality. This study was conducted to determine correlations between PSG-quantified sleep parameters and CI among individuals with late-life depression. Methods: 65 elderly patients with depression were included in the study. The sleep status was assessed using PSG, while cognitive function was evaluated using the Mini-Mental State Examination (MMSE). The correlation between PSG-measured sleep parameters and cognitive function was analyzed. Results: CI was observed in 31 (47.7%) individuals. Depressed elderly patients with CI exhibited a shorter total sleep time (TST) compared to those without CI. Furthermore, their sleep efficiency (SE) was reduced as evidenced by shortened durations and proportions of N1 and N3. Conversely, the proportion of non-rapid eye movement (NREM) and N2 increased in this group. Additionally, both the duration and proportion of rapid eye movement (REM) were decreased. Spearman correlation analysis revealed a linear relationship between the MMSE score and various sleep parameters. In the multivariate logistic regression model adjusted for patients' educational level, degree of depression, and obstructive sleep apnea (OSA), the independent risk factors for CI included decreased TST, SE, N1 stage duration, N3 stage duration, N1 stage proportion, and REM sleep time. Conversely, increased N2 stage proportion represented an independent risk factor for CI. Conclusions: In elderly patients with depression, a significant linear relationship was observed between the MMSE score and various sleep parameters measured by PSG. Decreased sleep parameters, including TST, SE, duration of N1 stage, duration of N3 stage, proportion of N1 stage, and REM sleep time, along with an increased proportion of N2 stage, were identified as independent risk factors for CI.