Chlamydia pneumoniae is a likely risk factor for ischemic stroke in young patients.

Recently, Chlamydia pneumoniae has been identified as a risk factor for atherosclerosis, cardiovascular disease, and stroke. In young patients the causes of stroke are more diverse, and remain unknown in about 30% of cases, despite thorough investigations. To find a possible relationship between C. pneumoniae infection and stroke at young age, we investigated C. pneumoniae antibody titers in 41 patients with ischemic stroke who were younger than 50 years old and in 55 healthy control subjects. A positive IgA antibody titer to C. pneumoniae was significantly associated with stroke (crude odds ratio 2.1; 90% confidence interval 1.1-9.5; P = .04). After adjusting for hypertension, smoking, and hypercholesterolemia, positive Chlamydia antibodies remained associated with stroke (adjusted odds ratio 2.8; 90% confidence interval 1.1-7.1; P = .04). No significant association between positive IgG antibodies and stroke was found. Because a positive IgA antibody titer may reflect a persistent infection, these data indicate that persistent C. pneumoniae infection may be an independent risk factor for stroke at young age.