The SARC-F score may indirectly reflect the extracellular water-to-total body water ratio.

Background & aims: In the Asian Working Group for Sarcopenia 2019 guidelines, SARC-F is used to screen for sarcopenia. SARC-F is measured based on five components: strength, assistance with walking, rising from a chair, climbing stairs, and falling. However, it has been reported that SARC-F has high specificity but low sensitivity for sarcopenia screening. Considering that SARC-F is currently recommended for sarcopenia screening, indicating the utility of SARC-F not only in sarcopenia screening but also in other aspects is pivotal. This cross-sectional study aimed to clarify the relationship between the SARC-F score and the extracellular water-to-total body water ratio (ECW/TBW) in community-dwelling older people.

Methods: This study included 167 community-dwelling older people (aged ≥ 65) who were able to walk independently and used the SARC-F as a screening test for sarcopenia diagnosis. ECW/TBW and the skeletal muscle mass index (SMI) were measured using bioelectrical impedance analysis. The associations among the SARC-F score, ECW/TBW, and SMI were assessed using Spearman's correlation coefficient. Multiple linear regression analyses of the SARC-F score were conducted. Age, sex, number of medications, pain, medical history, ECW/TBW, and SMI were considered independent variables in multiple linear regression analysis.

Results: The analyses revealed a significant positive correlation between the SARC-F score and ECW/TBW (ρ = 0.473, p < 0.001). SMI was significantly and negatively correlated with the SARC-F score (ρ = -0.233, p = 0.002). In the multiple linear regression analysis, ECW/TBW (β = 0.311, p < 0.001) and prevalence of pain (β = 0.169, p = 0.023) were significantly and independently associated with the SARC-F score (R² = 0.260). SMI was not significantly associated with the SARC-F score (β = 0.002, p = 0.986).

Conclusion: This study revealed a positive correlation between SARC-F score and ECW/TBW in community-dwelling older people, and this relationship persisted even after adjusting for confounding factors. However, there was no correlation between the SARC-F score and SMI. Our study indicated that the SARC-F score may be considered an indirect indicator of ECW/TBW. The score might also be useful for discriminating high and low ECW/TBW. These findings highlight a new use for SARC-F.