Total and Regional Fat/Muscle Mass Ratio and Risks of Incident Cardiovascular Disease and Mortality

Background To evaluate the sex-specific associations of total and regional fat/muscle mass ratio (FMR) with cardiovascular disease (CVD) incidence and mortality, and to explore the underlying mechanisms driven by cardiometabolites and inflammatory cells. We compared the predictive value of FMRs to body mass index. Methods and Results This population-based, prospective cohort study included 468 885 UK Biobank participants free of CVD at baseline. Fat mass and muscle mass were estimated using a bioelectrical impedance assessment device. FMR was calculated as fat mass divided by muscle mass in corresponding body parts (total body, trunk, arm, and leg). Multivariable Cox proportional hazards models and mediation analyses were used. During 12.5 years of follow-up, we documented 49 936 CVD cases and 4158 CVD deaths. Higher total FMR was associated with an increased risk of incident CVD (hazard ratios [HRs] were 1.63 and 1.83 for men and women, respectively), ischemic heart disease (men: HR, 1.61; women: HR, 1.81), myocardial infarction (men: HR, 1.72; women: HR, 1.49), and congestive heart failure (men: HR, 2.25; women: HR, 2.57). The positive associations of FMRs with mortality from total CVD or its subtypes were significant mainly in trunk and arm for male patients (P for trend <0.05). We also identified 8 cardiometabolites and 5 inflammatory cells that partially mediated FMR-CVD associations. FMRs were modestly better at discriminating cardiovascular mortality risk. Conclusions Higher total and regional FMRs were associated with an increased risk of CVD and mortality, partly mediated through cardiometabolites and inflammatory cells. Early monitoring of FMR should be considered to alleviate CVD risk. FMRs were superior to body mass index in predicting CVD mortality.