Relationships Among Skeletal Muscle Index, Dietary Protein Intake, and Serum Markers of Protein in Sarcopenic Older Adults

Abstract

Prevalence of sarcopenia increases with age and is related to several comorbidities. However, in the absence of disease there are some internal influences that may affect classification of sarcopenia or age-related loss of muscle mass. PURPOSE: The purpose of this study was to examine the relationships among skeletal muscle index (SMI), basic anthropometric measures, dietary protein intake, and serum markers of protein in older adults with class I (SMI 31-37% in men and 22-28% in women) or class II (SMI <31% in men and <22% in women) sarcopenia. METHODS: Six men and 5 women (age: 64.2±8.3 yrs; height: 171.3±14.7 cm; weight: 76.7±14.7 kg) agreed to undergo a dual-energy x-ray absorptiometry (DXA) scan, which was analyzed for segmental muscle mass and appendicular lean soft tissue. Participants also completed a 3-day food diary representing their typical diet, and a fasted blood sample was collected. The 3-day food diary was analyzed using Diet Analysis + (Version 8.0.1, Thompson Learning) software. Pearson product moment correlation coefficients were calculated on the following variables: Age, height (Ht), body weight (Wt), daily caloric intake (Kcal), grams of daily protein intake (Protein, g), percent of Kcal intake as protein (%PRO), protein per kg body weight (Prog/kg), SMI per kg body weight (SMI1), SMI1 per cm height (SMI2), total serum protein (TP), albumin (Alb), and globulin (Glob). RESULTS: There were no significant correlations among any serum protein markers or dietary protein intake variables and SMI1 or SMI2. There were expected correlations among age, height, weight, and SMI as well as associations among kcal and dietary protein intake. There were unexpected correlations between age and TP and Alb. CONCLUSIONS: Although not surprising, these findings indicate that serum protein and age are strongly inversely proportional. These findings extend those of previous studies that protein intake for sarcopenic older adults is important to maintain serum protein levels.