Association of prior infection with Chlamydia pneumoniae and angiographically demonstrated coronary artery disease.

To evaluate the association between prior infection with Chlamydia pneumoniae, as measured by IgG antibody, and coronary artery disease. A population-based, case-control study. Group Health Cooperative of Puget Sound, a Seattle-based health maintenance organization. Men 55 years of age and younger and women 65 years of age and younger. Cases (n = 171) were members of Group Health Cooperative undergoing diagnostic coronary angiography who had at least one coronary artery lesion occupying 50% or more of the luminal diameter. The population controls (n = 120) were Group Health Cooperative members without known coronary heart disease. The adjusted odds ratio (OR) for coronary artery disease associated with prior C pneumoniae infection as measured by the presence of IgG antibody. After adjusting for age, gender, and calendar quarter of blood drawing, the OR for coronary artery disease associated with the presence of antibody was 2.6 (95% confidence interval, 1.4 to 4.8). The association was limited to cigarette smokers, in whom the OR was 3.5 (95% confidence interval, 1.7 to 7.0). Among never-smokers, the OR was 0.8 (95% confidence interval, 0.3 to 1.9). When cases and controls were restricted to those assayed concurrently, the adjusted OR (smokers and nonsmokers combined) was 4.2 (95% confidence interval, 1.8 to 10.0). Adjustment for serum cholesterol, hypertension, alcohol use, diabetes, and socioeconomic status did not change these results. Only a week association was found when cases were compared with 63 subjects whose angiographic results were normal (OR, 1.2; 95% confidence interval, 0.6 to 2.2). These results generally support the previously reported association between C pneumoniae infection and coronary heart disease. However, caution should be used in interpreting the basis for this association.