Background: A number of studies in European and North American populations have reported associations between Chlamydia pneumoniae seropositivity and coronary heart disease (CHD). Our objective was to assess the association of IgG and IgA antibodies to C. pneumoniae with acute myocardial infarction (MI) in a population-based case-control study in a Middle Eastern country.
Methods: Eligible cases aged 25-64 with a first acute MI were ascertained through an active surveillance system in Jerusalem hospitals between 1987 and 1989 (85% response). Controls were Jerusalem residents aged 25-64 sampled from the national population registry (83% response). Data on sociodemographic variables, CHD history and risk factors were collected by interview. Chlamydia serology, available for 93% of eligible participants, was performed by microimmunofluorescence on frozen stored samples using the TWAR antigen. Altogether, 251 male and 51 female cases, and 324 male and 162 female controls were analysed.
Results: Overall, high IgG titres (> or = 128) were not associated with increased risk of acute MI (Odds ratio [OR] = 0.74 for men [95% confidence interval (CI): 0.47-1.17] and 0.91 for women [95% CI: 0.43-1.94]); neither were high IgA titres (> or = 80) (OR = 1.11 for men [95% CI: 0.71-1.73] and 1.15 for women [95% CI: 0.33-4.0]). At IgG and IgA titres of > 32 and > 20 respectively there was also no relation.
Conclusions: An association of C. pneumoniae seropositivity with acute MI was not confirmed in this population with a very high IgG seropositivity prevalence of 84% in males and 69% in females. However, we cannot exclude the possibility that a postulated recent outbreak obscured an association with chronic C. pneumoniae infection.