Examining the association between muscle mass, muscle function, and fat indexes in an elderly population

Skeletal muscle mass with function decline indicated as sarcopenia, which may cause disability in elderly adults. Studies regarding fat composition in sarcopenia have gained attraction recently; however, different fat indexes have yielded different findings. It is necessary to explore the association between muscle mass, muscle function, and fat indexes among elderly adults.

Community-dwelling elderly adults ages 65 and older who received annual health examination or outpatient services were enrolled. Hand grip strength and gait speed were measured. Muscle and fat mass were estimated by bioelectrical impedance analyzer. Presarcopenia was defined as loss of muscle mass only; sarcopenia was loss of muscle mass accompanied by low grip strength or/and slow gait speed. The relationships between sarcopenia parameters and different fat indexes among elderly adults were analyzed.

There were 295 participants recruited. The presarcopenia group showed lower fat indexes compared to the sarcopenia group. Negative correlations existed between sarcopenia parameters (skeletal muscle mass index, grip strength, gait speed) and fat indexes (body-fat percentage, fat-to-muscle ratio). In the multiple hierarchical regression model, gait speed was negatively associated with body-fat percentage (β = -0.255, P = 0.009) and fat-to-muscle ratio (β = -0.272, P = 0.005) in the male group. In the female group, grip strength was inversely associated with body-fat percentage (β = -0.232, P = 0.009) and fat-to-muscle ratio (β = -0.195, P = 0.031).

Individuals in the presarcopenia group had lower fat indexes than those in the sarcopenia group. Gait speed in men and hand grip strength in women-but not muscle mass for either- were negatively associated with body-fat percentage and fat-to-muscle ratio.