Overlap of depressive symptoms and low physical activity affects the risk of social frailty in Japanese community-dwelling older adults

Although depressive symptoms (DS) and physical activity (PA) have each been associated with social frailty (SF), their combined effects remain unclear. This study examined the independent and interactive associations of DS and objectively measured PA with SF in community-dwelling older adults. This cross-sectional study included 147 adults aged ≥ 65 years. DS were assessed using the Japanese version of 15-item Geriatric Depression Scale, and PA was measured objectively via accelerometer-based daily step counts, classified as < 4,000 or ≥ 4,000 steps/day. SF was evaluated using the five-item criteria proposed by Makizako et al. A two-way analysis of covariance was performed with DS (yes/no) and step count (≥ 4,000/<4,000) as independent variables and the total number of positive SF components (0–5) as the dependent variable, adjusting for relevant covariates. A significant interaction between DS and step count on SF was observed (P = 0.006). Significant main effects were also found, with higher SF scores among participants with DS and those walking < 4,000 steps/day (both P < 0.001). These findings indicate that both DS and low PA are independently associated with SF, and that the overlap of these two factors may be linked to an increased risk of SF among older adults.