Relationships between hand-grip strength, socioeconomic status, and depressive symptoms in community-dwelling older adults

Background: Depressive symptoms have been found to be associated with decreased hand-grip strength (HGS) and low socioeconomic status (SES) in older adults. We aimed to investigate the potential moderating effect of SES on the association between HGS and depressive symptoms and the potential mediating effect of HGS on the association between SES and depressive symptoms using a nationally representative sample of older adults. Method: Data from 3169 community-dwelling adults aged 60 years or older were acquired from the Korea National Health and Nutrition Examination Survey conducted in 2014 and 2016. HGS was measured using a digital hand-grip dynamometer. Depressive symptoms were evaluated using the 9-item version of the Patient Health Questionnaire-9 (PHQ-9). SES was assessed using equivalent monthly household income and education level. Results: Older adults in the lowest tertile of HGS measures were more likely to have experienced depressive symptoms compared to those in the highest tertile (odds ratio = 1.95, 95% confidence interval = 1.25-2.74). A significant moderating effect of household income level was observed on the association between HGS and PHQ9 score (P = 0.014). Older adults with a low income had a stronger inverse correlation between HGS and PHQ-9 score compared to those with a high income (low income: beta = - 0.162, P < 0.001; high income: beta = - 0.119, P = 0.036). HGS partially mediated the association between low income and depressive symptoms. Conclusion: Our findings indicate that there may be a stronger relationship between low HGS and depressive symptoms in socioeconomically deprived older people. Further research on muscle strength and income level in older adults is required regarding depression risk assessment.