Association between muscle strength and depressive symptoms among Chinese female college freshmen: a cross-sectional study.

BACKGROUND Increased physical activity level is related to lower risk of depressive symptoms, and there is an inverse association between muscle strength and risk of depressive symptoms among the elderly. Although there is evidence of an inverse association between muscle strength and depressive symptoms, the relationship between these variables in a younger population is still unknown. This study aimed to examine the association between handgrip strength, a representative indicator of skeletal muscle strength, and the risk of depressive symptoms among Chinese female college freshmen. METHODS A cross-sectional study was conducted among 867 participants aged between 16 and 23 years. Handgrip strength was measured with a handheld digital Smedley dynamometer, and handgrip strength relative to body weight (kg/kg) was calculated and was classified into tertiles as follows: low (0.32-0.50), medium (0.51-0.58), and high (0.59-0.94). Depressive symptoms were evaluated using the 20-item Zung self-rating depression scale (SDS), and three cutoff points were used to indicate different depression levels. RESULTS We found that 10.7% of participants were classified as having severe depressive symptoms using an SDS score of 50 as the cutoff point. After adjusting for potential confounders, the adjusted odds ratios and 95% confidence intervals (CIs) for moderate-to-severe depressive symptoms across tertiles of the relative handgrip strength were 1.00 (reference) for tertile 1, 0.614 (0.353, 1.069) for tertile 2, and 0.537 (0.292, 0.988) for tertile 3 (P for trend = 0.041). The significant associations remained when other cutoff points (SDS scores: 48 or 45) were used. Interactions between handgrip strength and potential confounders for depressive symptoms in the final models were not significant. CONCLUSIONS Our findings indicate that handgrip strength is inversely and independently related to the risk of depressive symptoms among Chinese female college freshmen. The present findings can help develop an effective intervention strategy against depression. Further intervention studies are needed to explore the mechanisms underlying the effects of handgrip strength on depressive symptoms.