Helicobacter pylori, Chlamydia pneumoniae and myocardial infarction

Several epidemiological studies have suggested a positive association of coronary heart disease with both Helicobacter pylori and Chlamydia pneumoniae infection. The issue has been difficult to resolve because of the potential impact of several confounding factors, in particular, socioeconomic status for H. pylori and smoking for C. pneumoniae.

A case-control study was carried out of 341 patients with a recent myocardial infarction (MI) and 831 community controls who had serology tests for H. pylori and C. pneumoniae (selected from a total study number of 1745 subjects). Individuals of Pacific Island or Maori ethnicity were excluded because they were infrequent.

H. pylori seropositivity was associated with increasing age (P < 0.001) and lower household income (P = 0.0003) but not with gender, smoking status or alcohol intake. H. pylori was associated with lower high-density lipoprotein cholesterol (P = 0.007) and a higher body mass index (P = 0.007). The overall seropositivity for H. pylori was 41.6% for patients with MI and 34.5% for age and sex-matched population controls. The odds ratio was 1.34 (95% confidence interval (CI): 1.00-1.80; P = 0.038) after adjusting for age and sex. C. pneumoniae seropositivity was significantly associated with male sex, younger age (P = 0.03) and smoking status (P = 0.004) but not associated with household income or any other measured risk factor for coronary heart disease. The overall seropositivity for C. pneumoniae was 51.2% for patients with recent MI and 43.5% for controls. After adjusting for age and sex, the odds ratio was 1.24 (95%CI: 0.95-1.62; P = 0.11). Subgroup analysis showed no clear pattern within different age groups. In particular, the odds ratio for H. pylori seropositivity in younger subjects (aged 35-49 years) was similar to the overall group (1.38; 95%CI: 0.83-2.29).

The association between H. pylori or C. pneumoniae seropositivity and coronary heart disease was significant but may not indicate a causal association.