Increased extracellular-to-total body water ratio in community-dwelling individuals in their 20s to 90s is associated with decreased grip strength and gait speed

Background: In 2019, the European Working Group of Sarcopenia in Older People indicated the importance of assessing muscle mass and quality in diagnosing sarcopenia. The extracellular water-to-total body water ratio (ECW/TBW) has recently been noticed as muscle quality. This study aimed to clarify the associations of ECW/TBW and grip strength and gait speed in community-dwelling individuals in their 20s to 90s. Methods: This study employed a cross-sectional design. We enrolled 661 community-dwelling individuals (aged ≥ 20). The ECW/TBW was measured using multifrequency bioelectrical impedance analysis. Associations between grip strength, gait speed, and ECW/TBW were analyzed separately for males and females using Spearman's correlation coefficient. Multiple linear regression analyses were conducted to examine factors associated with grip strength and gait speed. Results: Correlation analyses revealed significant negative correlations between ECW/TBW and grip strength (males; ρ = -0.413, p < 0.001, females; ρ = -0.384, p < 0.001) and gait speed (males; ρ = -0.122, p = 0.037, females; ρ = -0.206, p < 0.001). In the multiple linear regression analysis, ECW/TBW was significantly and independently associated with grip strength (males; β = -0.207, p = 0.006, females; β = -0.215, p = 0.001) and gait speed (males; β = -0.213, p = 0.013, females; β = -0.305, p < 0.001). Conclusions: The present study identified negative associations between ECW/TBW and both grip strength and gait speed among community-dwelling individuals aged in their 20s to 90s. Additionally, these associations were confirmed in males and females.