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

## TL;DR

This study finds that poor sleep quality in elderly patients with depression is linked to cognitive impairment.

## Contribution

The study uses polysomnography to reveal specific sleep parameters associated with cognitive decline in elderly depression patients.

## Key findings

- Cognitive impairment was observed in 47.7% of elderly depression patients.
- Shorter total sleep time and reduced sleep efficiency correlated with cognitive impairment.
- The proportion of NREM sleep was significantly linked to cognitive scores in regression analysis.

## Abstract

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.

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.

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. However, in the multiple linear regression model, only the proportions of NREM exhibited a significant linear relationship with the MMSE scores.

In elderly patients with depression, a significant linear relationship was observed between the MMSE score and various sleep parameters measured by PSG.