Body mass index and the risk of recurrent coronary events following acute myocardial infarction

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Abstract

Although excess adiposity appears to increase the risk of coronary heart disease in the general population, its importance in patients with established coronary disease is less defined. We evaluated a population-based inception cohort of survivors to hospital discharge following first acute myocardial infarction (AMI) (n = 2,541) to assess the association between body mass index (BMI) and the risk of recurrent coronary events and to explore the mechanisms for this relation. Using Cox proportional-hazards regression, we assessed the risk of recurrent coronary events associated with levels of adiposity as defined by BMI and then investigated potential mechanisms through which adiposity conferred risk by examining how adjustment for diabetes mellitus, systemic hypertension, and dyslipidemia affected the association. Forty-one percent of the cohort were overweight (BMI 25 to 29.9), and 27.8% were obese (BMI ≥30). After adjustment for other risk factors, the risk of recurrent coronary events (n = 418) increased as BMI increased, especially among those who were obese. Using a BMI of 16 to 24.9 as the reference group, for mildly overweight patients (BMI 25 to 27.4), the relative risk (RR) was 0.93 (95% confidence interval [CI] 0.70 to 1.24); it was 1.16 for more severe overweight patients (BMI 27.5 to 29.9; 95% CI 0.87 to 1.55). For patients with class I obesity (BMI 30 to 34.9), the RR was 1.49 (95% CI 1.12 to 1.98), and for class II to III obesity (BMI ≥35), the RR was 1.80 (95% CI 1.30 to 2.48). We estimated that clinical measurements of diabetes, hypertension, and dyslipidemia explained approximately 43% of this risk. Thus, excess adiposity as measured by BMI was associated with an increased risk of recurrent coronary events following AMI, particularly among those who were obese.

Section snippets

Study population

The study setting was Group Health Cooperative, a health maintenance organization with >400,000 enrollees based in Washington state. Eligible patients included all enrollees who survived to hospital discharge following a first AMI during the period from July 1986 (women) or July 1989 (men) through December 1996. A potential incident AMI was identified by the International Classification of Disease 9th revision codes from the computerized discharge abstracts of the 2 Group Health Cooperative

Results

In the cohort of 2,541 patients who survived to hospital discharge following first AMI, 2/3 were either overweight (40.8%) with a BMI of 25 to 29.9, or obese (27.8%) with a BMI ≥30. Patients with greater BMIs tended to be younger, have a greater prevalence of diabetes, hypertension, or dyslipidemia, and were more frequently taking aspirin and β blockers (Table 1). During the 8,584 person-years of follow-up on the 2,541 subjects (median years of follow-up 3.0), there were 418 recurrent coronary

Discussion

In this inception cohort of persons who survived incident AMI, excess adiposity as estimated by BMI was associated with an increased risk of recurrent coronary events after adjustment for other clinical risk factors. This risk was especially evident among obese patients (BMI ≥30), whose risk appeared to increase with higher levels of obesity. The increased RR in the obese subgroup is of significant public health importance because these persons comprise over 1/4 of the cohort, a proportion

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    This study was supported by grants HL53375, HL40628, and HL43201 from the National Heart, Lung, and Blood Institute, Bethesda, Maryland. Manuscript received December 8, 2000; revised manuscript received and accepted March 30, 2001.

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