Obesity and the risk of death after acute myocardial infarction

In the general population, obesity is associated with an increased risk of all-cause death. However, the importance of obesity in patients with established coronary heart disease is less well defined.

As part of the Determinants of Myocardial Infarction Onset Study, we performed a prospective cohort study of 1898 patients hospitalized with confirmed acute myocardial infarction between 1989 and 1994, with a median follow-up of 3.8 years. We assessed all-cause death through December 1995, using the National Death Index. We categorized patients according to WHO criteria for body mass index (BMI). We compared long-term death according to BMI (kg/m2) by using Cox proportional hazards regression.

Of the 1898 eligible patients, 607 (32%) were normal weight (18.5 to 24.9 kg/m2), 832 (44%) were overweight (25.0 to 29.9 kg/m2), 331 (17%) were class I obese (30.0 to 34.9 kg/m2), and 128 (7%) were class II or more obese (> or =35.0 kg/m2). A total of 311 patients died during follow-up. After adjustment for potentially confounding risk factors and excluding patients with noncardiac comorbidity, the risk for death appeared to increase linearly, with increasing BMI across all categories (P for trend =.08). The relative risk of death in all obese patients (> or =30 kg/m2) was 1.46, compared with those with normal weight (95% CI, 0.98 to 2.17).

We found that BMI appeared to have a positive, graded relation with post-myocardial infarction death. Whether weight reduction and secondary prevention strategies would reverse this effect in obese population remains to be seen.