Body-Mass Index and Mortality among Adults with Incident Myocardial Infarction

The relation between body mass index (BMI, kg/m2) and mortality among survivors of myocardial infarction (MI) remains controversial. We examined the relationship of BMI before and after MI, and change in weight, with all-cause mortality among participants of the Nurses’ Health Study (1980-2016) and Health Professionals Follow up Study (1988-2016) cohorts. During up to 36 years of follow-up, we documented 4856 incident nonfatal MI cases, among whom 2407 died. For the pre-MI and post-MI BMI, overweight was not associated with lower mortality. Obesity (BMI ≥ 30 kg/m2) was associated with higher risk of mortality. Compared to participants with post-MI BMI of 22.5-24.9, HRs were 1.16, 95% CI: 1.01, 1.34 for BMI 30-34.9 and 1.52, 95% CI: 1.27, 1.83 for BMI ≥ 35; Ptrend<0.001. Compared to stable weight from before to after MI, reduction of > 4 BMI units was associated with increased mortality, HR=1.53, 95%: CI 1.28, 1.83. This increase was only among participants who lost weight without improving physical activity or diet. Our findings showed no survival benefit of excess adiposity in relation to risk of mortality. Weight loss from before to after MI without lifestyle improvement may reflect reverse causation and disease severity.