Effect of the Obesity Paradox on Mortality in Patients with Acute Coronary Syndrome: A Comprehensive Meta-analysis of the Literature

Background:The protective effect of obesity in patients with acute coronary syndrome undergoing percutaneous coronary intervention or bypass surgery has been described as the obesity paradox in the literature.Aims: In this comprehensive meta-analysis, we aimed to investigate the pooled effect of the obesity paradox on mortality in acute coronary syndrome patients.Study Design: Systemic meta-analysis and metaregression.Methods: We searched PubMed, Google Scholar, and the Cochrane Library for eligible studies that compared the mortality rates between body mass index cut-off points in acute coronary syndrome patients.This meta-analysis comprised 54 studies with 534,903 patients.Random-and fixed-effect models were used to calculate pooled effects sizes in the presence of moderately high and low heterogeneity between studies, respectively.A metaregression analysis was used to detect possible causes of heterogeneity.A dose-response meta-analysis was also conducted to detect the association between mortality risk and body mass index.Results: Overweight patients had lower mortality risk for 30-day (RR =0.69; 0.62-0.76,p < 0.01) and long-term (RR =0.73; 0.70-0.77,p < 0.01) mortality than normal-weight patients.The 30-day mortality risk was higher in low-weight patients than in normal-weight patients (RR =1.74; 1.39-2.18,p < 0.01).Meta-regression could not explain the possible causes of between-study heterogeneity.Patients with body mass index <21.5 kg/m 2 and >40 kg/m 2 had a higher risk of mortality, which was lowest at approximately 30 kg/m 2 .Conclusion: Low-weight and overweight acute coronary syndrome patients had higher mortality risk than normal-weight patients.A U-shaped nonlinear association was detected between body mass index and mortality risk.