Relação entre água corporal, função muscular e desempenho funcional em idosos comunitários: resultados do estudo PRO-VA

Abstract

INTRODUCTION: The aging process induces a variety of anatomical and physiological changes in the human body, significantly impacting the musculoskeletal system. Notably, a reduction in total body water content is intrinsic to the functional decline observed in elderly individuals. OBJECTIVE: To analyze the relationships between total body water and variables related to muscle function and funcional performance in communitydwelling elderly participants of the PRO-EVA Study. METHOD: A cross-sectional and analytical observational study was conducted, evaluating 735 individuals aged ≥60 years, of both sex, residing in Parnamirim/RN, Brazil. Data were collected through a standardized protocol containing questions on sociodemographic variables and lifestyle habits (from the Elderly Person's Health Notebook – CSPI). Total body water variables were measured using electrical bioimpedance, expressed by the formula: ACT = 2.447 − (0.09156×Age) + (0.1074×Height) + (0.3362×Weight). Variables related to function included calf circumference and grip strength, measured by a tape measure and a Saehan® hydraulic dynamometer, respectively. Performance was assessed using the Short Physical Performance Battery (SPPB). The relationship between investigated variables was analyzed using Spearman's correlation test, considered significant at p<0.05 with a 95% confidence interval. Additionally, the Ridge Path Analysis method was employed to address multicollinearity identified in the multiple regression model. RESULTS: The sample had a mean age of 70.1 (±7.1) years, most of whom were female (60.8%), nonsmokers (84.9%), non-practitioners of physical activity (52.9%) and had 0-3 years of schooling (51.6%). Regarding muscle strength, calf circumference and SPPB, the averages were 24.89 (±7.81) kgf, 32.9 (±3.52) cm and 9.6 (±2.2) points, respectively. In the Ridge Path analysis, a significant relationship was found between total body water, sociodemographic variables, and the Short Physical Performance Battery (SPPB). In particular, there is a statistically negative association between extracellular water and age, which translates directly into the SPPB score. Regarding the relationship between total body water and sociodemographic variables with handgrip strength, a positive association was observed between intracellular and extracellular water, together with the gender variable, and handgrip strength. Finally, when exploring the relationship between total body water and sociodemographic variables with calf circumference, a positive association was found between both intracellular and extracellular water and calf circumference. CONCLUSION: The study revealed a significant association between total body hydration and functional performance in the elderly, highlighting the importance of intracellular water in muscle strength. Additionally, demographic factors such as age and gender were identified as significant predictors of muscle function and functional performance.