The Association between Nap Duration, Nighttime Sleep, and Depressive Symptoms among Elderly People in China: an Empirical Analysis based on 2020 CHARLS Data

Abstract

Background As China enters a moderately aging society, the mental health problems of the elderly are increasing year by year, and lifestyle habits are closely related to the mental health of the elderly. Objective Exploring the relationship between nap time, nighttime sleep, and depressive symptoms among elderly people in China, and determining recommended sleep time based on lifestyle habits, providing scientific basis for early prevention and control of depression in the elderly. Methods Based on the publicly released fifth round (2020) of the China Health and Retirement Longitudinal Study (CHARLS) on November 16, 2023, 8 233 eligible individuals were included as research subjects. The Depression Rating Scale (CSE-D10) was used to assess depressive symptoms in elderly individuals, with nap duration divided into 5 levels: no nap, <30 min, 30-59 min, 60-89 min, ≥90 min. Nighttime sleep was divided into 5 levels: ≥8 h, 7-<8 h, 6-<7 h, 5-<6 h, <5 h. Multivariate Logistic regression analysis was used to explore the factors that affect the occurrence of depression symptoms in elderly people. Random forest model was used to analyze the importance of nap duration and nighttime sleep in the occurrence of depression symptoms in elderly people. Restrictive cubic spline curves were used to further explore the dose-response relationship between nap duration, nighttime sleep duration, and the risk of depression symptoms. Results During the 2020 survey period, the incidence of depressive symptoms among elderly people in China was 24.84% (2 045/8 233) . The results of multivariate Logistic regression analysis showed that a nap duration of 30-59 minutes was a protective factor for depression symptoms in the elderly (OR=0.814, 95%CI=0.673-0.985, P=0.034) , and a nighttime sleep duration of less than 5 hours was a risk factor for depression symptoms in the elderly (OR=1.705, 95%CI=1.435-2.027, P<0.001) . Women, unmarried/separated/divorced/widowed, disabled, physically painful, physically active, self-rated health status decreased, life satisfaction decreased, stroke, and Parkinson's disease increased the risk of depression symptoms in the elderly (P<0.05) . The random forest model showed that the duration of nap time and nighttime sleep time had a significant impact on depressive symptoms. There was a non-linear relationship between the duration of nap time and the occurrence of depressive symptoms (Pnonlinear<0.05) . The risk of depression in elderly people continued to decrease with increasing time after nap time of 30 minutes, with the lowest level being about 50 minutes. The risk of depression symptoms increased after nap time exceeded 75 minutes. The risk of depression in elderly people decreased continuously with time after 6 hours of sleep at night, with a minimum level of about 7 hours. The risk of depression increased after more than 9 hours of sleep (Poverall<0.05) . Conclusion The incidence of depression (24.84%) is higher in the elderly population in China, and there is a J-shaped relationship between the duration of nap time and nighttime sleep and depression. It is recommended that elderly people nap for 30-75 minutes every day, and moderate nap time can effectively reduce the risk of depression symptoms in the elderly. At the same time, sleeping for 6-9 hours at night can reduce the risk of depression symptoms, which has certain significance for early prevention and control of depression in the elderly population.

Keywords

• depression|aged|nap duration|nighttime sleep|charls