Correlation between sleep characteristics and cognitive decline in the elderly people: A cross-sectional study in China.

STUDY OBJECTIVES: In this study, we conducted a cross-sectional analysis of the sleep characteristics in the elderly Chinese people to comprehensively investigate the association between sleep and cognitive function in the elderly people. We aimed to evaluate the most important demographic factors, conventional physiological indices and living habits that may influence sleep. METHODS: We surveyed 2901 elderly people (age ≥60 years old) face-to-face from 1 July to 31 December 2017, who were recruited from 17 communities of the Pudong New Area (Shanghai, China) by probability proportional to size. The Pittsburgh sleep quality index (PSQI) scale was used to describe the sleep features of each participant. Cognitive assessment was performed using the mini-mental state examination (MMSE) scale, Montreal cognitive assessment (MoCA) and the clinical dementia rating (CDR) scale. Those factors which potentially influence sleep and consequentially may impact cognition in the elderly people were evaluated, and the correlations of sleep characteristics and cognitive function were explored by the linear regression analysis. RESULTS: Altogether, there were 1287 (44.4%) people taking part in the investigation. Sleep quality was significantly correlated with MMSE and MoCA total scores. Healthy sleep (especially enough sleep) was correlated with better cognitive functions. Besides recognised relative factors (such as age, sex and living alone), the number of children was found to be a strong risk factor of poor sleep. Anxiety before sleep and light/noise interference significantly damaged sleep while an exercise routine was associated with better sleep. Moderate levels of reading, watching TV and household work were correlated with superior sleep quality. CONCLUSION: In conclusion, sleep characteristics correlate with cognitive decline in the elderly people, and they can be influenced by multiple demographic factors and living habits. To improve sleep quality, it may be important to change sleep environment, to be relax, to increase physical exercise and recreational activities moderately.