Estimating the Effects of Obesity and Weight Change on Mortality Using a Dynamic Causal Model.
Estimating the Effects of Obesity and Weight Change on Mortality Using a Dynamic Causal Model.
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使用动态因果模型估算肥胖和体重变化对死亡率的影响。
DOI：
10.1371/journal.pone.0129946
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Cao B
中科院分区：
文献类型：
--
作者：
Cao B
在估计肥胖的死亡风险时，一个众所周知的挑战是归因于疾病相关和吸烟相关的体重减轻的反向因果关系。鉴于慢性和急性疾病的可能性随着年龄的增长而增加，反向因果关系对从老年人口中得出的估计数最具威胁。我分析了来自全国代表性纵向数据集“健康与退休研究”（HRS）的12523名50岁以上受访者的数据。在调整了人口统计和社会经济变量以及疾病和吸烟等时变混杂因素后，估计了基线体重和时变体重变化对死亡率的影响。体重是用身体质量指数（BMI）来衡量的。在死亡率的生存模型中，疾病和吸烟被滞后，以尽量减少在估计体重变化影响时反向因果关系的偏差。此外，由于疾病既是BMI变化的原因，也是由BMI变化引起的，因此我使用了边际结构模型（MSM）而不是标准调整来控制由BMI和其他时间相关因素引起的混淆。总体而言，相对于正常体重，基线时体重过轻和II/III级的风险比分别为2.07（95%可信区间（CI）： 1.28-3.37）和1.82(1.54-2.16)，而超重和I级肥胖并没有显著降低或增加死亡风险。此外，相对于稳定的体重变化，所有类型的体重变化导致死亡风险显著增加。具体来说，大幅度减肥导致的死亡风险是保持稳定体重范围的近3.86（3.26-4.58）倍，小幅减肥导致的死亡风险约为1.81（1.55-2.11）倍。相比之下，体重增加多和体重增加少的风险比分别为1.98（1.67-2.35）和1.20（1.02-1.41）。基线体重过轻或严重肥胖与死亡风险过高有关，体重变化往往会增加死亡风险。疾病和吸烟造成的混淆导致高估了基线体重不足和体重减轻的影响，但低估了基线肥胖的影响。
A well-known challenge in estimating the mortality risks of obesity is reverse causality attributable to illness-associated and smoking-associated weight loss. Given that the likelihood of chronic and acute illnesses rises with age, reverse causality is most threatening to estimates derived from elderly populations. I analyzed data from 12,523 respondents over 50 years old from a nationally representative longitudinal dataset, the Health and Retirement Study (HRS). The effects of both baseline body weight and time-varying weight change on mortality are estimated, adjusting for demographic and socio-economic variables, as well as time-varying confounders including illness and smoking. Body weight is measured by body mass index (BMI). In survival models for mortality, illness and smoking were lagged to minimize bias from reverse causality in estimates of the effect of weight change. Furthermore, because illness both causes and is caused by changes in BMI, I used a marginal structural model (MSM) rather than standard adjustment to control confounding by this and other time-dependent factors. Overall, relative to normal weight, underweight and Class II/III at baseline are associated with hazard ratios that are 2.07 (95% confidence interval (CI): 1.28–3.37) and 1.82 (1.54–2.16) respectively, whereas overweight and Class I obesity do not significantly lower or raise the mortality risks. Furthermore, relative to stable weight change, all types of weight change lead to significantly increased risk of mortality. Specifically, large weight loss results in a mortality risk that is nearly 3.86 (3.26–4.58) times of staying in the stable weight range and small weight loss is about 1.81 (1.55–2.11 ) times riskier. In contrast, large weight gain and small weight gain are associated with hazard ratios that are 1.98 (1.67–2.35) and 1.20 (1.02–1.41) respectively. Being underweight or severe obese at baseline is associated with excess mortality risk, and weight change tend to raise mortality risk. Both the confounding by illness and by smoking lead to overestimates of the effects of being underweight at baseline and of weight loss, but underestimates the effect of being obese at baseline.
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