Combined association of chronic disease and low skeletal muscle mass with physical performance in older adults in the Sarcopenia and Translational Aging Research in Taiwan (START) study

Background: Multiple chronic conditions and low skeletal muscle mass are common features of aging that are detrimental to physical performance. This study evaluates the simultaneous impact of these conditions on physical performance in older adults. Methods: Five studies from 2003 to 2012 were pooled to include 2,398 adults aged >= 65 years with diagnosed chronic diseases measured by self-administered questionnaire. Low muscle mass was defined as an appendicular skeletal muscle mass index less than that of the sex-specific lowest quintile in the population of older adults. Poor physical performances were defined as the lowest quintile of grip strength and gait speed in the population of older adults and the slowest sex-specific 20% of Timed Up and Go (TUG) test at each study site. Chi-squared and logistic regression tests were applied for data analysis. Results: Mean age of the study participants, of whom approximately 50% were men, was 74.3 years. Slow gait speed was nearly three times more likely to occur in the presence of low muscle mass coupled with chronic disease than in the absence of both factors after adjustment for study site, age, sex, education, marital status, body mass index, tobacco and alcohol use, and comorbidities. The independent effect of low muscle mass was generally stronger than that of each disease. Participants with more than two chronic diseases and low muscle mass were significantly more likely to perform poorly than those with no risk factors (odds ratio [OR] = 2.51 in patients with low grip strength, OR = 3.89 in patients with low gait speed, and OR = 3.67 in patients with poor TUG test scores, all P < 0.05) after adjustment. Conclusions: The combined association of chronic disease and low skeletal mass with physical performance was stronger than the effect of either factor alone.