Abstract
OBJECTIVE: We aimed to determine if there were sex differences in lean body mass (LBM) in patients with rheumatoid arthritis (RA) when compared with sex- and race-specific National Health and Nutrition Examination Survey (NHANES) reference data, and to investigate the impact of sex differences in risk factors for LBM deficits. METHODS: Dual x-ray absorptiometry measures of whole body LBM and appendicular LBM (arms and legs, appendicular lean mass [ALM]) were obtained on a total of 190 subjects from 2 independent cohorts (141 from San Francisco [SF], 49 from Philadelphia [PA]), expressed as indices adjusted for height (LBM index and ALM index, kg/m(2) ), and converted to sex- and race-specific Z scores relative to age and based on NHANES data. Sarcopenia was defined using 4 different sex-specific definitions. Multivariable linear and logistic regression analyses adjusted for disease activity, disease duration, physical activity, anti-cyclic citrullinated peptide seropositivity, fat mass index, and glucocorticoid use. RESULTS: While there were significant differences between the 2 cohorts, ALM index Z scores were significantly lower in men compared to women in both (SF: -1.43 versus -0.43, P < 0.0001; PA: -0.83 versus -0.06, P = 0.03). Observed sex differences were significant after adjustment in multivariable analyses within both cohorts. Odds of sarcopenia were 3 to 8 times greater in men in the SF cohort. Men in the PA cohort also had a higher, but nonsignificant, risk of sarcopenia. CONCLUSION: RA is associated with significant LBM deficits, with greater deficits observed in men. Future study may help elucidate the mechanisms driving greater deficits among men.