Total and regional fat-to-muscle mass ratio in relation to all-cause and cause-specific mortality in men and women.

Abstract

Fat-to-muscle mass ratio (FMR) has been considered a potentially useful indicator for assessing disease risk. However, the association between FMR and risk of death remains inconclusive. To investigate the associations of FMR (the whole body, trunk, legs and arms) with all-cause and cause-specific mortality by sex. A total of 337951 participants from the UK Biobank were included. Fat mass and muscle mass were estimated using a bioelectrical impedance assessment device. Cox proportional hazard regression was applied to explore the associations. During a median follow-up of 12.58 years, we recorded 22391 (6.62 %) deaths, of which 4427 were from cardiovascular disease, 11740 from cancer, and 1458 from respiratory disease. We observed associations of different shapes (U-shaped for whole body and trunk, L-shaped for legs, and J-shaped for arms) between FMR and all-cause mortality (P for non-linearity <0.001). Compared with the lowest quintile of whole body and trunk FMR, the all-cause mortality risk was reduced by 12-14% and 7-15% in men and women in quintile 2-4, respectively. The hazard ratio (HR) associated with arm FMR in men and leg FMR in men and women (quintile 5 vs 1) were 1.14 (95% CI 1.05, 1.23), 0.76 (0.71, 0.82), and 0.78 (0.70, 0.88) for all-cause mortality, respectively. The associations between FMR and cause-specific mortality were mostly similar to those for all-cause mortality. Our study revealed significant associations of total and regional FMR with mortality, providing new evidence that FMR may be a potentially useful indicator for assessing mortality risk.