The association between body mass index and in-hospital outcome among patients with acute myocardial infarction-Insights from China Acute Myocardial Infarction (CAMI) registry.

Background: The relationship between body mass index (BMI) and in-hospital mortality risk among patients with acute myocardial infarction (AMI) remains controversial.

Methods And Results: We included 35,964 patients diagnosed with AMI in China Acute Myocardial Infarction registry between January 2013 and December 2016. Patients were categorized into 4 groups according to BMI level: BMI <18.5, 18.5-24.9, 25-30, and ≥30 kg/m for underweight, normal, overweight, and obese groups, respectively. Clinical data were extracted for each patient, and multivariable logistic regression analysis was used to examine the association between BMI level and in-hospital mortality. Compared with normal-weight patients, obese patients were younger, more often current smokers, and more likely to have hypertension, hyperlipidemia, and diabetes. Multivariable regression analysis results demonstrated that compared with normal group, underweight group had significantly higher in-hospital mortality (odds ratio [OR]: 1.34; 95% confidence interval [CI]: 1.06-1.69; p = 0.016), while overweight group (OR: 0.86; 95% CI: 0.77-0.97; p = 0.011) and obese group (OR: 0.65; 95% CI: 0.46-0.91; p = 0.013) had lower mortality. All subgroups showed a trend toward lower in-hospital mortality risk as BMI increased.

Conclusions: Our study provided robust evidence supporting "obesity paradox" in a contemporary large-scale cohort of patients with AMI and demonstrated that increased BMI was independently associated with lower in-hospital mortality.