Association of overweight and obesity with patient mortality after acute myocardial infarction: a meta-analysis of prospective studies

BACKGROUND: The obesity paradox, which suggests that overweight and obesity exert protective effects on patient survival after acute myocardial infarction (AMI), is controversial in the existing researches. OBJECTIVE: The aim of our study was to evaluate the associations of overweight and obesity with all-cause mortality in patients after AMI. METHODS: The PubMed and Embase databases were searched for original articles published in English prior to March 2015, using the terms ('myocardial infarction' and ('body mass index'or BMI)) and ('mortality' or 'death'). Prospective studies that reported the relationship between overweight and obesity at baseline (immediately after AMI) and all-cause mortality outcomes were eligible. Two authors separately performed the extraction of the data, and any differences were discussed and resolved. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were computed either by fixed effects or random effects models. RESULTS: Twenty studies were included in the present analysis. Comparing a healthy weight group to a combined overweight and obese group, the pooled RRs were 0.72 (95% CI: 0.57-0.90) for in-hospital mortality, 0.3((95% CI: 0.28-0.55) for short-term mortality, 0.66 (95% CI: 0.55-0.78) for medium-term mortality and 0.68 (95% CI: 0.57-0.81) for long-term mortality. However, the RRs were 0.82 (95% CI: 0.64-1.06) for in-hospital mortality and 0.94 (95% CI: 0.55-1.58) for short-term, 0.82 (95% CI: 0.65-1.04) for medium-term and 0.98 (95% CI: 0.88-1.09) for long-term mortality when the obese group was compared with the overweight group, which were not significant. CONCLUSIONS: This meta-analysis identified an inverse association between overweight and obesity with all-cause mortality after AMI compared with healthy weight, which indicated an obesity paradox. Another notable finding is that obesity is associated with neither an increased nor a decreased risk of death in patients after AMI compared with overweight patients.