Persistent Q fever and ischaemic stroke in elderly patients.

Whether persistent or chronic Q fever may act as a risk factor for stroke is unknown. A case-control study was conducted in the Hospital Universitario de Burgos (Spain) between February 2011 and December 2012. A total of 803 samples from 634 consecutive hospitalized patients ≥65 years old were tested, of whom 111 were cases (patients with prevalent or incident ischaemic stroke and/or transient ischaemic attack) and 523 were controls (patients without ischaemic stroke and/or transient ischaemic attack). Immunoglobulin G (IgG) antibody titres phase I and II against Q fever, and IgG antibodies levels against Chlamydia pneumoniae and cytomegalovirus (CMV), were determined using immunofluorescence assay and ELISA methods, respectively. Phase I IgG titres against Coxiella burnetii ≥1:256 (compatible with chronic or persistent Q fever) were detected in 16 of 110 (14.5%) cases and in 32 of 524 (6.1%) controls; P = .004, odds ratio (OR) 2.6, 95% confidence interval (CI) 1.3 to 4.9. This ratio was maintained after adjusting for age, sex, hypertension, dyslipidaemia, cardioembolic focus, smoking, diabetes, other cardiovascular diseases, C-reactive protein, and leukocyte count (OR 2.6, 95% CI 1.3 to 5.3). High-titre IgG antibodies (top quartile) against CMV (OR 2.1, 95% CI 1.3 to 3.5), but not against C. pneumoniae (OR 0.9, 95% CI 0.5 to 1.6), also were associated with ischaemic stroke after adjustment for risk factors. In conclusion, serology compatible with persistent or chronic Q fever is associated with ischaemic stroke in elderly patients. High levels of IgG antibodies against CMV, but not against C. pneumoniae, also are associated with ischaemic stroke in these patients.