Infectious Burden and Risk of Stroke: The Northern Manhattan Study

BACKGROUND: Common infections may be associated with stroke risk, though no single infection is likely a major independent predictor. OBJECTIVE: To determine the association between a composite measure of serologies to common infections (Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, Herpes Simplex Virus 1 and 2) and stroke risk in a prospective cohort study. DESIGN: Prospective cohort followed longitudinally for median 8 years. PATIENTS: Randomly selected stroke-free participants from a multiethnic urban community. SETTING: Northern Manhattan Study (NOMAS). MAIN OUTCOME MEASURE: Incident stroke and other vascular events. RESULTS: All five infectious serologies were available from baseline samples in 1625 participants (mean age 68.5 ± 10.1 years; 64.9% women). Cox proportional hazards models were used to estimate associations of each positive serology with stroke. Individual parameter estimates were then combined into a weighted index of infectious burden (IB) and used to calculate hazard ratios and confidence intervals (HR, 95% CI) for association with risk of stroke and other outcomes, adjusted for risk factors. Each individual infection was positively though not significantly associated with stroke risk after adjusting for other risk factors. The IB index was associated with an increased risk of all strokes (adjusted HR per standard deviation 1.39, 95% CI 1.02–1.90) after adjusting for demographics and risk factors. Results were similar after excluding those with coronary disease (adjusted HR 1.50, 95% CI 1.05–2.13) and adjusting for inflammatory biomarkers. CONCLUSION: A quantitative weighted index of infectious burden was associated with risk of first stroke in this cohort. Future studies are needed to confirm these findings and to further define optimal measures of IB as a stroke risk factor