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Adjusting for reverse causation to estimate the effect of obesity on mortality after incident heart failure, the atherosclerosis risk in communities (ARIC) study.

Research paper by Maryam M Shakiba, Hamid H Soori, Mohammad Ali MA Mansournia, Seyed Saeed SS Hashemi Nazari, Yahya Y Salimi

Indexed on: 11 Jun '16Published on: 11 Jun '16Published in: Epidemiology and health



Abstract

The lower mortality rate of obese patients in heart failure (HF) has been partly attributed to reverse causation bias due to weight loss caused by disease. Using the weight both prior and after heart failure HF, this study aimed to adjust for reverse causation and examine the association of obesity both before and after HF with mortality.Using Atherosclerosis Risk in Communities (ARIC) study, 308 patients with data available on before and after development of incident HF included. Pre and post-morbid obesity defined based on body mass index measurements at least three months before and after incident HF. The associations of pre and post-morbid obesity and weight change with survival after HF evaluated using Cox proportional hazard model.Pre-morbid obesity associated with higher mortality (HR=1.61, 95%CI: 1.04-2.49, p=0.03) but post-morbid obesity associated with increased survival (HR=0.57, 95%CI: 0.37-0.88, p=0.01). Adjustment for weight change due to disease as the confounder for obesity-mortality relation resulted in no significant association of post-morbid obesity and mortality.This study demonstrates that controlling for reverse causality through adjustment for weight change as the confounder may remove or inverse the protective effect of obesity on mortality among patients with incident HF.