Massa magra e conteúdo mineral ósseo estão associados a força muscular dos membros superiores?: abordagem segundo o gênero e ciclo de vida a partir do estudo longitudinal de saúde do adulto (ELSA-BRASIL)

Abstract

INTRODUCTION: The body structure reached in adulthood, such as muscle mass and bone mineral content, reflects the balance between acquisition, maintenance, and loss throughout life. Low muscle mass, a recent marker, and bone mineral content, a marker of the life course, can influence the worse performance of muscle grip strength in adults and the elderly, being a marker of independence and the development of unfavorable health conditions throughout the years. OBJECTIVE: To estimate whether greater amounts of muscle mass and bone mineral content are associated with greater handgrip strength and whether this relationship is different in men and women as well as in adults and the elderly. METHODS: Participants in this analysis were eligible for the second wave of exams and interviews (2012 to 2014) of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a multicentric cohort, composed of 15,105 active or retired civil servants, aged 35 and 74 years in the baseline, belonging to higher education and research institutions. The outcome variable of this study was the handgrip strength (HGS) of the dominant hand-measured in Kgf. The performance of the HGS test was also used in categories, being adequate (Men ≥ 26kgf; Women ≥ 16kgf) and inadequate (Men <26kgf; Women <16kgf). The explanatory variables of interest were the amounts of muscle mass (MM) and bone mineral content (CMO), in kilograms (kg), measured by an electrical bioimpedance device (InBody 230). The magnitudes of the associations were estimated by the differences in means and their 95% confidence intervals (95%CI) using linear regression models (Model 1). Also, sequential adjustments were made for; age, sex, and race/self-reported color (Model 2); current educational attainment (Model 3); alcohol consumption, smoking and physical activity (Model 4); body mass index, use of diuretics, calcium and vitamin D supplementation, depression status and the number of chronic diseases (Model 5). After complete adjustment (Model 5) for each explanatory variable of interest, terms of interaction with sex and age were included to verify the presence of effect modification by these variables on the relationship of MM and BMC on HSG. Analyzes were performed using Stata 13.0. RESULTS: Of the 12,491 participants, 54.48% were women, with a mean age of 55 years (SD = men ± 9.21; women ± 8.74). Considering the entire study population, lower amounts of muscle mass (mean difference: 1.19; 95% CI 0.89 -0.91) and bone mineral content (mean difference: 12.24; 95% CI 0.27 -0.35) are associated with poor performance in the handgrip strength test. After complete adjustment (Model 5), there was a considerable reduction in the magnitudes of the associations (muscle mass: 0.69; 95% CI 0.66- 0.73; bone mineral content: 5.58; 95% CI 5.21-5, 95), remaining statically significant. We did not observe any change in the effect of sex and age (p-value of interaction terms> 0.05) in this relationship. CONCLUSION: We observed that better musculoskeletal health was associated with better performance in the upper limb strength test, without modification of the effect of sex and age. Our results reinforce the importance of the life course in maintaining and preventing the decline in functionality with aging, which impacts on lower morbidity and mortality, financial costs for the individual, family, and audiences with health services and interventions.