Increased body mass index (BMI) is a well-established risk factor for cardiovascular disease; however, patients with elevated BMI, in comparison to those with low BMI, seem to have better survival, a phenomenon reported as "obesity paradox," which remains controversial. We investigated the effect of BMI on cardiac mortality post acute myocardial infarction (AMI).In this analysis, 3562 AMI patients were included and classified into four groups based on BMI values. The primary endpoint was cardiac death. Compared to normoweight group, overweight and obese group subjects were younger, mostly men, and more likely to receive percutaneous coronary intervention (PCI) and had higher levels of glucose and lipids, but lower level of NTproBNP. Subjects in the underweight group were older, were mostly women, had lower Barthel index (BI), were less likely to receive PCI, and had lower levels of glucose and lipids, but higher level of N-terminal pro-brain natriuretic peptide (NTproBNP) and higher rates of left ventricular ejection fraction (LVEF) < 50%. During a median follow-up period of 1.9 years, cardiac death occurred significantly more in the underweight group (30.0%, 10.6%, 7.0%, and 5.0% among the four groups from underweight to obese; P < 0.001 for trend). The Cox analysis revealed that underweight was an independent predictor of subsequent cardiac death (odds ratio (OR), 1.86; 95% confidence interval (CI), 1.07-3.25) and identified that older age, BI < 60, higher levels of cardiac troponin I (cTnI), LVEF < 50%, and not receiving PCI were independently associated with increased risk of cardiac death.Patients who were underweight were at greater risk of cardiac death post AMI. In addition, older age, frail, higher levels of cTnI, LVEF < 50%, and not receiving PCI also independently predicted cardiac mortality post AMI.
Keywords: Acute coronary syndrome; Body mass index; Obesity paradox.