Are body fat and inflammatory markers independently associated with age-related muscle changes?

Summary Background & aims A growing number of studies have shown that body fat and inflammation are associated with age-related changes in body muscle composition. However, most of these studies did not control for potential confounders. The aim was to determine whether there is an association of body fat and inflammatory cytokines with muscle mass/strength decline in community-dwelling older adults. Methods Anthropometric, physical and functionality variables were collected. Nutritional status was assessed by the MNA tool. Dynapenia was assessed with handgrip strength on the dominant hand using a dynamometer. Sarcopenia was determined using adapted criteria from the European Working Group on Sarcopenia in Older People 2 (EWGSOP2). Inflammatory cytokines were evaluated in plasma using a multiplex assay. Associations to muscle mass/strength decline were analyzed using a multinominal logistic regression, adjusted for potential confounders. Results We recruited a convenience sample of 311 adults aged 60 years or older. Most of subjects were sufficiently active females with a median age of 68 years (interquartile range [IQR], 64 – 74 years), whereas about a half (46.3%) were at risk of malnutrition. The prevalence of dynapenia was 38.3%, whereas sarcopenia was 13.2%. After controlling for potential confounders, we found that relative fat mass index is independently associated with sarcopenia. Loss of strength was independently associated only with female sex, lower physical activity, worse nutrition and IL-10/TNF-α ratio, whereas female sex, an insufficiently active lifestyle and relative fat mass index were the key determinants of sarcopenia. Conclusions These findings highlight the importance of physical activity and healthy diet as effective interventions to prevent muscle mass/strength decline, and points to IL-10/TNF-α ratio and body fat as independently associated factors for dynapenia and sarcopenia, respectively.