Objective: To evaluate the association between prior infection with Chlamydia pneumoniae, as measured by IgG antibody, and coronary artery disease.
Design: A population-based, case-control study.
Setting: Group Health Cooperative of Puget Sound, a Seattle-based health maintenance organization.
Participants: 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.
Main outcome measure: The adjusted odds ratio (OR) for coronary artery disease associated with prior C pneumoniae infection as measured by the presence of IgG antibody.
Results: 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).
Conclusions: 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.