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/m2 and >40 kg/m2 had a higher risk of mortality, which was lowest at approximately 30 kg/m2 .

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.