Sarcopenia, cardiopulmonary fitness, and physical disability in community-dwelling elderly people.

BACKGROUND Sarcopenia refers to the loss of skeletal muscle mass with aging. It is believed to be associated with functional impairment and physical disability. OBJECTIVE The purposes of this study were: (1) to compare the physical activity, muscle strength (force-generating capacity), cardiopulmonary fitness, and physical disability in community-dwelling elderly people with sarcopenia, borderline sarcopenia, and normal skeletal muscle mass in Taiwan and (2) to test the hypothesis that sarcopenia is associated with physical disability and examine whether the association is mediated by decreased muscle strength or cardiopulmonary fitness. DESIGN This was a cross-sectional investigation. METHODS Two hundred seventy-five community-dwelling elderly people (148 men, 127 women) aged > or =65 years participated in the study. The participants were recruited from communities in the district of Zhongzheng, Taipei. Predicted skeletal muscle mass was estimated using a bioelectrical impedance analysis equation. The skeletal muscle mass index (SMI) was calculated by dividing skeletal muscle mass by height squared. Physical disability was assessed using the Groningen Activity Restriction Scale. Physical activity was assessed using a 7-day recall physical activity questionnaire. Cardiopulmonary fitness was assessed using a 3-minute step test, and grip strength was measured to represent muscle strength. RESULTS Cardiopulmonary fitness was significantly lower in elderly people with sarcopenia than in those with normal SMIs. Grip strength and daily energy expenditure (kcal/kg/day) were not significantly different between the participants with sarcopenia and those with normal SMIs. The odds ratio for physical disability between the participants with sarcopenia and those with normal SMIs was 3.03 (95% confidence interval=1.21-7.61). The odds ratio decreased and the significant difference diminished after controlling for cardiopulmonary fitness. LIMITATIONS A causal relationship between sarcopenia and physical activity, cardiopulmonary fitness, and physical disability cannot be established because of the cross-sectional nature of study design. CONCLUSIONS Sarcopenia was associated with physical disability in elderly men. The association between sarcopenia and physical disability was mediated to a large extent by decreased cardiopulmonary fitness.