Chlamydia pneumoniae infection and its association with coronary heart disease and cardiovascular risk factors in a sample South Asian population.

Recent studies have suggested that a chronic infection with Chlamydia pneumoniae (C. pneumoniae) may be associated with the risk of developing coronary heart disease (CHD). A case control study was conducted to investigate the association between C. pneumoniae infection and coronary heart disease and coronary risk factors in a sample South Asian population. C. pneumoniae specific IgG antibody was measured by microimmunofluorescence. Among controls 56.6% were seropositive (> or =1/32) compared to 58.5% of acute myocardial infarction (AMI) patients (n=41, odds ratio 1.08, CI 0.37--3.12, P=0.93) and 73.3% of stable coronary heart disease (SCHD) patients (n=30, odds ratio 2.1, CI 0.63--7.19, P=0.27). The highest geometric mean titre of control subjects (n=30) was significantly lower (74.7) compared to AMI patients (101.5, P<0.05) and SCHD patients (138.6, P<0.05). Patients who were non-smokers had higher odds ratios for CHD than smokers when seropositive at IgG antibody titres of 1/32, 1/64 and 1/128, suggesting an association between smoking and C. pneumoniae infection. In patients with CHD there was a significant association between diabetes mellitus and seropositivity (P=0.008) in those over 50 years of age. Non-smoking CHD patients with high cholesterol/HDL-C ratio had a higher trend for seropositivity. Other risk factors (smoking, systolic and diastolic blood pressure, waist/hip ratio, triglycerides) showed no association when controlled for age. In the control group, smokers with high cholesterol/HDL-C ratio had a higher trend for seropositivity. These results do not provide strong support for the hypothesis that C. pneumoniae infection is a risk factor for clinical CHD in this South Asian population. Results suggest that C. pneumoniae infection may be linked to CHD through its interaction with some of the known risk factors such as blood lipids, diabetes and smoking.