Family history of coronary heart disease, a strong risk factor for myocardial infarction interacting with other cardiovascular risk factors: Results from the Stockholm Heart Epidemiology Program (SHEEP)

We explored the relation between family history of coronary heart disease a nd the risk of myocardial infarction in a case-control study of subjects, 4 5 to 70 years of age, living in Stockholm, Sweden. Our cases comprised 1091 male and 531 female first-time acute myocardial infarction patients who ha d survived at least 28 days after their infarction. Referents were randomly selected from the population from which the cases were derived. The adjust ed odds ratio (OR) of myocardial infarction was 2.0 (95% confidence interva l [CI] = 1.6-2.6) for men reporting greater than or equal to1 affected pare nt or sibling, compared with men with no family history of coronary heart d isease, and 3.4 (95% CI = 2.1-5.9) for those reporting greater than or equa l to2 affected parents or siblings. The corresponding OR for women were 2.1 (95% CI = 1.5-3.0) and 44 (95% CI = 2.4-8.1). We found evidence for synerg istic interactions in women exposed to family history of coronary heart dis ease in combination with current smoking and with a high quotient between l ow-density lipoprotein and high-density lipoprotein cholesterol (>4.0), res pectively, which yielded adjusted synergy index scores of 2.9 (95% CI = 1.2 -7.2) and 3,8 (95% CI = 1.5-9.7), respectively. Similarly, in men we found evidence for interaction for the co-exposure of family history of coronary heart disease and diabetes mellitus. Our study shows that family history of coronary heart disease is nor only a strong risk factor for myocardial inf arction in both sexes, but that its effect is synergistic with other cardio vascular risk factors as well.