# Association between sleep duration and depressive symptoms among older adults in China: a national cross-sectional study

## TL;DR

Longer sleep is linked to fewer depressive symptoms in older Chinese adults, with benefits peaking around 7 hours of sleep.

## Contribution

This study reveals a non-linear dose-response relationship between sleep duration and depressive symptoms in China’s aging population.

## Key findings

- Increased sleep duration is associated with reduced odds of depressive symptoms, with the strongest effect at 7–8 hours.
- Each additional hour of sleep reduces depressive symptoms risk by 31% up to 7 hours, then by 9% beyond.
- A non-linear relationship was observed, with an inflection point at 7 hours of sleep.

## Abstract

Depression is a common mental health issue among older adults. Previous studies have suggested that sleep disturbances, including abnormal sleep duration, may be associated with an increased risk of depressive symptoms. However, the relationship between sleep duration and depressive symptoms in the context of China’s aging population remains underexplored; this study aims to investigate this association among older adults.

This national cross-sectional study included 12,104 participants aged 65+ from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS). To assess the association between sleep duration and depressive symptoms, we used multivariate logistic regression models adjusted for sociodemographic characteristics, lifestyle factors, and comorbid chronic diseases. Additionally, trend test, restricted cubic splines (RCS) and threshold saturation effect analyses were employed to further explore the relationship between sleep duration and depressive symptoms.

After adjusting for confounders, increased sleep duration was linked to a lower depressive symptoms risk. The odds ratios (ORs) were 0.60 (95% CI 0.54-0.69) for 6–7 hours, 0.40 (95% CI 0.36-0.47) for 7–8 hours, 0.34 (95% CI 0.30-0.39) for 8–9 hours, and 0.32 (95% CI 0.28-0.36) for 9–15 hours. The relationship was non-linear, with an inflection point at 7 hours. Each additional hour of sleep duration was associated with a 31% (OR = 0.69, 95% CI 0.66-0.72) reduction in depressive symptoms; however, this association attenuated after 7 hours of sleep, with each additional hour corresponding to a 9% (OR = 0.91, 95% CI 0.89-0.94) reduction.

In this nationwide survey, it is revealed that a dose - response relationship exists between sleep duration and depressive symptoms among Chinese older adults.