Background: Sarcopenia defined by lean mass has been inconsistently associated with disability in elders. Studies suggest that definitions should consider body size and additional influences of high fat mass (FM; sarcopenic-obesity). We examined sarcopenia accounting for body size, and sarcopenic-obesity, in relation to mobility limitations among 767 elderly men and women (mean age 79 years) from the Framingham Study.

Methods: Whole-body dual-energy x-ray absorptiometry measured appendicular lean mass (ALM) and total FM in 1992-1995. Sarcopenia was defined in two ways: ALM/height squared (ALM/ht(2)) and ALM adjusted for height and FM (residuals). Sarcopenic-obesity categories (referent, obese, sarcopenic, and sarcopenic-obese) were defined by cross-classifying ALM/ht(2) and obesity (% body fat: more than 30 for men and more than 40 for women). Mobility limitation was defined as self-reported inability to walk one-half mile, climb stairs, or perform heavy housework. Sex-specific logistic regression calculated odds ratios (OR) and 95% confidence intervals (CI) for mobility limitation, adjusting for covariates.

Results: Sixteen percent of men and 30% of women had mobility limitation. Among men, both ALM/ht(2) (OR = 6.3, 95% CI = 2.5-16.1) and residuals (OR = 4.6, 95% CI = 2.0-10.5) sarcopenia were associated with increased limitation. For sarcopenic-obesity, odds of limitation was higher in sarcopenic (OR = 6.1, 95% CI = 2.2-16.9) and sarcopenic-obese categories (OR = 3.5, 95% CI = 1.0-12.7) but suggested no synergistic effect. In women, only residuals sarcopenia was associated with higher odds of limitation (OR = 1.8, 95% CI = 1.2-2.9).

Conclusions: Low lean mass is associated with mobility limitations after accounting for body size and fat, and lean and FM have independent effects on mobility in elders. These findings support previous reports that sarcopenia definitions should consider body size and fat.