Supplementary Material for: Central lean mass distribution and the risks of all-cause and cause-specific mortality in 40283 UK Biobank participants

Introduction
The purpose of this study is to investigate the association of central lean mass distribution with the risk of mortality.
Methods
This cohort study included 40283 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.

引言
本研究旨在探讨躯干性瘦体重分布与死亡风险的相关性。

方法
本项队列研究共纳入40283名英国生物样本库（UK Biobank）受试者。采用Cox比例风险回归模型，分析经双能X线吸收测量法（dual energy X-ray absorptiometry）测得的躯干性瘦体重分布（即躯干-下肢瘦体重比值）与死亡风险之间的相关性。

结果
受试者中位年龄为65岁，女性占比52%。中位随访4.18年后，共计674名受试者死亡，其中366例死于癌症，126例死于心血管疾病。以躯干-下肢瘦体重比值最低三分位组为参照，经多因素校正（校正年龄、性别、种族、生活方式、共患疾病、体质量指数及四肢肌肉质量指数）后，躯干-下肢瘦体重比值最高三分位组的全因死亡、癌症相关死亡及心血管相关死亡的校正后风险比分别为1.55（95%CI：1.23~1.94）、1.69（95%CI：1.26~2.26）及1.14（95%CI：0.72~1.80）。中性粒细胞-淋巴细胞比值（neutrophil-to-lymphocyte ratio）介导了躯干-下肢瘦体重比值与全因死亡相关性中的9.3%（95%CI：3.3%~40.4%）。研究发现，躯干-下肢瘦体重比值与高龄、不良饮食质量之间存在相加型交互作用，可影响全因死亡风险。

结论
在英国中老年人群中，经双能X线吸收测量法测得的躯干-下肢瘦体重比值与全因死亡及癌症相关死亡风险呈正相关，且该相关性独立于全身性肥胖与中心性肥胖。躯干性瘦体重分布可能与衰老及不良饮食质量产生协同交互作用，进而进一步升高死亡风险。