Central Lean Mass Distribution and the Risks of All-Cause and Cause-Specific Mortality in 40,283 UK Biobank Participants

Introduction: The purpose of this study was to investigate the association of central lean mass distribution with the risk of mortality. Methods: This cohort study included 40,283 UK Biobank participants. Cox proportional hazards regression models were used to estimate the association of central lean mass distribution, i.e., trunk-to-leg lean mass ratio, assessed by dual-energy X-ray absorptiometry, with the risk of mortality. Results: The median age of the participants was 65 years, and 52% were women. During a median follow-up of 4.18 years, 674 participants died, of whom 366 were due to cancer and 126 were due to cardiovascular causes. Compared with the lowest tertile of a trunk-to-leg lean mass ratio, the multivariable-adjusted (age, sex, ethnicity, lifestyle, comorbidities, body mass index, and appendicular muscle mass index) hazards ratios of the highest tertile of trunk-to-leg lean mass ratio were 1.55 (95% CI: 1.23–1.94), 1.69 (95% CI: 1.26–2.26), and 1.14 (95% CI: 0.72–1.80) for all-cause, cancer, and cardiovascular mortality, respectively. Neutrophil-to-lymphocyte ratio mediated 9.3% (95% CI: 3.3%–40.4%) of the association of trunk-to-leg lean mass ratio with all-cause mortality. There was evidence for additive interactions of trunk-to-leg lean mass ratio with older age and poor diet quality for all-cause mortality. Conclusion: Trunk-to-leg lean mass ratio, assessed by dual-energy X-ray absorptiometry, was positively associated with the risks of all-cause and cancer mortality, independent of general obesity and central obesity, in UK middle-aged and older adults. Central lean mass distribution may interact synergistically with aging and poor diet quality to further increase the risk of death.