Lower limb strength and depression: a national cross-sectional study of an elderly population in China

The relationship between lower limb strength and depression in the elderly remains underexplored. This study aims to investigate this relationship using representative samples from China.

A total of 3421 elderly people aged 60 and above from the China Health and Retirement Longitudinal Study (CHARLS) were included. Five Times Sit-to-Stand (5TSTS) test was used to group the strength of lower limbs, and subjects' demographic characteristics, lifestyle behaviour and health index were evaluated. After adjusting the related variables, the relationship between lower limb strength and depression was determined by logistic regression model, and whether the relationship between lower limb strength and depression was related to different ages was further studied.

There were 1222 (35.7%) participants suffering from depression. Higher lower limb strength was associated with a lower likelihood of depression. Compared to the weakest group (Q1), those with stronger lower limb strength had significantly lower adjusted odds ratio (OR) for depression: OR ranged from 0.722 (95% CI: 0.589-0.886) to 0.446 (95% CI: 0.359-0.553). The relationship between lower limb strength and depression varied by age.

This cross-sectional study cannot establish causality. Additionally, depression assessment relied on self-reports, which may introduce bias. Future longitudinal studies should consider other psychological and social factors to comprehensively understand the determinants of depression in the elderly.

There is a correlation between lower limb strength and depression, that is, the incidence of depressive symptoms in the elderly with better lower limb strength is lower, and this significant correlation has been proved in both sexes and almost all age groups.