Body Mass Index and Mortality among Adults with Incident Myocardial Infarction

The relationship between body mass index (BMI; weight (kg)/height (m)2) and mortality among survivors of myocardial infarction (MI) remains controversial. We examined the relationships of BMI before and after MI and change in weight with all-cause mortality among participants in the Nurses' Health Study (1980-2016) and Health Professionals Follow-up Study (1988-2016) cohorts. During a follow-up period of up to 36 years, we documented 4,856 participants with incident nonfatal MI, among whom 2,407 died during follow-up. For pre-MI and post-MI BMI, overweight was not associated with lower mortality. Obesity (BMI ≥30) was associated with higher risk of mortality. Compared with participants with post-MI BMI of 22.5-24.9, hazard ratios were 1.16 (95% confidence interval (CI): 1.01, 1.34) for BMI 30.0-34.9 and 1.52 (95% CI: 1.27, 1.83) for BMI ≥35.0 (P for trend < 0.001). Compared with stable weight from before MI to after MI, a reduction of more than 4 BMI units was associated with increased mortality (hazard ratio = 1.53, 95%: CI: 1.28, 1.83). This increase was seen only among participants who lost weight without improving their 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.