Bilateral association between muscle strength and depression: evidence from a prospective cohort study

Both low muscle strength and depressive symptoms are common among middle-aged and older adults. However, their bilateral association has not been thoroughly investigated. This study examined whether muscle strength and depression are bilaterally associated using data from a prospective cohort in China.

A total of 6,961 participants without depression and 6,817 participants without low muscle strength from the China Health and Retirement Longitudinal Study were included to investigate the association of muscle strength with depression and of depressive symptoms with low muscle strength, respectively. The 10-item Center for Epidemiologic Studies Depression Scale (CESD-10) was used to assess depressive symptoms, with a cut-off score of 10. Handgrip strength and the time taken to complete the Five Times Sit-to-Stand Test (5TSTS) were used to evaluate muscle strength. Cox regression was applied to assess the associations after adjusting for relevant variables. Restricted cubic splines (RCS) were used to explore potential non-linear relationships.

There was a significant association between handgrip strength (HR: 0.98; 95% CI: 0.98-0.99) and time of 5TSTS (HR: 1.02; 95% CI: 1.01-1.03) with the 7-year incident depressive symptoms. Similarly, depressive symptoms were significantly associated with the 4-year incident low muscle strength, as defined by both handgrip strength (HR: 1.04; 95% CI: 1.02-1.05) and time of 5TSTS (HR: 1.02; 95% CI: 1.01-1.04). No evidence of non-linear associations was detected.

Depressive symptoms were assessed using the CESD-10 scale rather than a clinical diagnosis.

A bilateral longitudinal association exists between muscle strength and depression.