An association between an antibody against Chlamydia pneumoniae and ischemic stroke in elderly Japanese

Chlamydia pneumoniae (Cp) is an important pathogen for infections of the respiratory tract; recently, also a number of reports suggesting its relation to atherosclerosis. This study was performed to clarify the relation between Cp infection and ischemic stroke.

Forty elderly patients with ischemic stroke (age 75 +/- 6.6; male 57.5%) and 85 elderly control subjects without a history of ischemic stroke (age 74 +/- 8.1; male 43.5%) were investigated.

Patients were divided into four groups according to clinical diagnosis: 1) atherothrombotic infarction, 2) lacunar infarction, 3) those with cardiac embolism, and 4) non-classifiable. Cp infection was determined by measuring the anti-Cp IgG specific antibody level (Cp IgG index) using enzyme-linked immunosorbent assay (ELIZA) method. Those below the 1.10 Cp IgG index were determined as seronegative and those above 1.10 as seropositive.

We found that 20 cases (87.0%) of atherothrombotic infarction, 6 (66.7%) of lacunar infarction, 3 (50.0%) others and 52 (61.2%) control were Cp seropositive. Cp seropositiveness, as adjusted by multiple regression analysis using various known risk factors, was a significant independent contributing factor for ischemic stroke (p = 0.017) and was associated with an increased risk for atherothrombotic infarction (odds ratio, 12.6; 95% CI, 2.0-79.3).

This suggests that Cp infection is also an important risk factor for ischemic stroke, particularly atherothrombotic infarction in elderly Japanese.