The Relationship Between Body Mass Index and In-Hospital Mortality in the Contemporary Era of an Acute Myocardial Infarction Management

Background: The association between body mass index (BMI) and clinical outcomes following an acute myocardial infarction (AMI) remains controversial. Our objective was to investigate the relationship between BMI and AMI presentation, in-hospital clinical course and mortality in the contemporary era of AMI management. Methods: Patients, hospitalized for an AMI between October 2015 and December 2016, were identified in the National Inpatient Sample (NIS) database. Socio-demographic and clinical data, including BMI, were collected and outcomes, including length of stay and mortality, were analyzed. Patients were divided into 6 BMI (kg/m2) subgroups; under-weight (<= 19), normal-weight (20-25), over-weight (26-30), obese I (31-35), obese II (36-39) and extremely obese (>= 40). Multivariable logistic regression model was used to identify predictors of in-hospital mortality. Linear regression model was used to identify predictors of length of stay (LOS). Results: An estimated total of 125,405 hospitalizations for an AMI across the US were analyzed. Compared to the other BMI subgroups, the under-weight, normal-weight and extremely obese groups presented with a non-ST segment elevation AMI (NSTEMI) more frequently and were less likely to undergo coronary revascularization. The data show a J-shaped relationship between BMI and study outcomes with lower mortality in patients with BMI over 25 compared to normal-and low-weight patients. In the multivariate regression model, BMI group was found to be an independent predictor of mortality. Conclusion: J-shaped relationship between BMI and mortality was documented in patients hospitalized for an AMI in the recent years. These findings confirm that the "obesity paradox" persists during the contemporary era of an AMI management.