Refining the Association Between Body Mass Index and Atrial Fibrillation: G-Formula and Restricted Mean Survival Times
Refining the Association Between Body Mass Index and Atrial Fibrillation: G-Formula and Restricted Mean Survival Times
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DOI：
10.1161/jaha.119.013011
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发表时间：
2019-08-20
影响因子：
5.4
通讯作者：
Trinquart, Ludovic
中科院分区：
文献类型：
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作者：
Conner, Sarah C.;Lodi, Sara;Trinquart, Ludovic
背景-以前评估体重指数（BMI）和房颤（AF）之间关系的研究没有考虑随时间变化的协变量，而这些协变量可能受以前BMI的影响。我们说明了如何g-公式可以占随时间变化的confounding.Methods和结果，我们包括4392名参与者的心脏研究谁是AF自由在45至55岁，并遵循他们长达20年。我们用考克斯模型比较了随时间变化的非肥胖与肥胖的风险比。我们使用g公式比较非肥胖与肥胖，以及BMI每年下降10%（直到达到正常体重）与自然病程。我们估计了HR和限制平均生存时间的差异，生存时间和无AF时间的平均差异。我们调整了性别、年龄和随时间变化的风险因素。考克斯模型表明，与肥胖受试者相比，非肥胖受试者的AF发生率降低（HR，0.83; 95% CI，0.72-0.97）。G公式分析比较了所有非肥胖者和肥胖者，得出了更强的相关性（HR，0.73; 95%CI，0.58-0.91）。非肥胖者的限制性平均生存时间为19.22年，肥胖者为19.03年（差异为2.25个月; 95%CI，-0.66至5.16）。当评估BMI每年下降10%时，相关性较弱（HR 0.96; 95%CI，0.86-1.08）。结论-在考虑了依赖于使用g公式的既往暴露的时变协变量后，BMI降低与AF发生率降低相关，而考克斯模型无法适应。绝对的措施，如有限的平均生存时间差提供了上下文的相关性的相对措施。
Background-Previous studies assessing the association between body mass index (BMI) and atrial fibrillation (AF) did not account for time-varying covariates, which may be affected by previous BMI. We illustrate how the g-formula can account for time-varying confounding.Methods and Results-We included 4392 participants from the Framingham Heart Study who were AF free at ages 45 to 55 years, and followed them for up to 20 years. We estimated hazard ratios (HRs) comparing time-varying nonobese versus obese with Cox models. We used the g-formula to compare nonobese versus obese and 10% annual decrease in BMI (until normal weight is reached) versus natural course. We estimated HRs and differences in restricted mean survival times, the mean difference in time alive and AF free. We adjusted for sex, age, and time-varying risk factors. Cox models indicated that nonobese participants had a decreased rate of AF versus obese participants (HR, 0.83; 95% CI, 0.72-0.97). G-formula analyses comparing everyone had they been nonobese versus obese yielded stronger associations (HR, 0.73; 95% CI, 0.58-0.91). The restricted mean survival time was 19.22 years had everyone been nonobese and 19.03 years had everyone been obese (difference, 2.25 months; 95% CI, -0.66 to 5.16). When assessing a 10% annual decrease in BMI, the association was weaker (HR 0.96; 95% CI, 0.86-1.08).Conclusions-Decreased BMI was associated with a lower rate of AF after accounting for time-varying covariates that depend on previous exposure using the g-formula, which Cox models cannot accommodate. Absolute measures like the restricted mean survival time difference offer context to relative measures of association.