Joint effects of Chlamydia pneumoniae infection and classic coronary risk factors on risk of acute myocardial infarction.

BACKGROUND: Although not in itself strongly predictive of coronary heart disease, Chlamydia pneumoniae infection could interact with classic risk factors in determining risk of acute myocardial infarction (AMI). METHODS: We assessed C pneumoniae immunoglobulin (Ig) G and IgA titers and classic risk factors in 618 patients with AMI and in 967 controls. RESULTS: IgG titers were not related to AMI, but a significant association was seen between IgA titers and AMI. Excess risk of AMI was noted mainly among patients with the highest IgA titers, such as those beyond 2.88 (the 95th percentile cutoff point in control subjects), showing a 1.8-fold increase in risk (odds ratio 1.75, 95% CI 1.04-2.92). Classic risk factors did not differ between subjects with IgA titers above and below the 95th percentile cutoff. However, in multivariate analyses, models incorporating both IgA titers and a classic risk factor such as obesity, hypercholesterolemia, or smoking predicted risk more effectively than single-parameter models. For example, the odds ratio for AMI among subjects with the highest IgA titers plus hypercholesterolemia was greater than the product of individual risks associated with these high IgA titers and with hypercholesterolemia. CONCLUSIONS: Interactions with classic risk factors (ie, obesity, hypercholesterolemia, and smoking), increased the predictive value of C pneumoniae IgA antibody titers in determining risk of AMI.

Prevalence of Helicobacter pylori infection and its link to coronary risk factors in Japanese patients with acute myocardial infarction.

The association between Helicobacter pylori (H. pylori) infection and coronary artery disease, as well as the association between H. pylori infection and classic coronary risk factors, is controversial in patients from Western countries. The high prevalence of H. pylori infection in Japanese subjects enables an examination of these associations in a large population, especially in young patients, because coronary risk factors may be more strongly associated with younger individuals than with older individuals. The IgG seropositivity to H. pylori was assessed in 618 cases with acute myocardial infarction (AMI) and in 967 controls. The prevalence of seropositivity to H. pylori was similar between cases and controls, but in subjects younger than 55 years, the rate was significantly higher in cases than in controls (58.7% vs 43.3%, p = 0.009). After adjustment for age, gender, diabetes mellitus, hypertension, smoking, body mass index, total cholesterol, and high density lipoprotein cholesterol, the odds ratio for acute myocardial infarction was 2.97 (95% confidence interval, 1.37-6.41; p = 0.006). Worsening of classic coronary risk factors was not associated with H. pylori infection in subjects younger than 55 years. These results suggest that in younger individuals in Japan, H. pylori infection is significantly associated with AMI independent of the classic coronary risk factors.