Insulin-like growth factor-1 and interleukin 6 predict sarcopenia in very old community-living men and women: The Framingham Heart Study

OBJECTIVES: To assess the prognostic role of the inflammatory cytokine, interleukin 6 (IL-6), and insulin-like growth factor-1 (IGF-1) in predicting 2-year changes in fat-free mass (FFM) while controlling for potential confounders. DESIGN: Population-based cohort, the Framingham Heart Study, examined in 1992-93 and 1994-95. SETTING: General community. PARTICIPANTS: Two hundred thirty-two men and 326 women aged 72 to 92. MEASUREMENTS: IGF-1 was measured using radioimmunoassay and cellular IL-6 production using non-crossreacting radioimmunoassays. FFM was estimated using population-specific equations for predicting FFM from bioelectrical impedance analysis developed separately for men and women. RESULTS: Higher IGF-1 predicted smaller loss of FFM in men than lower IGF-1 did (P = .002), after adjusting for age, baseline FFM, fat mass, and 2-year weight changes, whereas cellular IL-6 was a significant predictor of sarcopenia in women (P = .02). Weight change was a strong determinant of change in FFM in both sexes (P < .0001). CONCLUSION: Predictors of sarcopenia include body composition characteristics that are common to men and women and sex-specific metabolic predictors. Sarcopenia appears to reflect a withdrawal of anabolic stimuli, such as growth hormone, in men but an increase in catabolic stimuli, such as cellular IL-6, in women.