Pneumococcal Pneumonia and the Risk of Stroke: A Population-Based Follow-Up Study

BACKGROUND: To investigate the risk of developing stroke in patients hospitalized following a diagnosis of pneumococcal pneumonia. METHODS: The study cohorts comprised of patients hospitalized with a principal diagnosis of pneumococcal pneumonia (n = 745), with a random sampling of control individuals in 2004 (n = 1490). The Cox proportional hazard model was used to compare the stroke-free survival rate between the cohorts after adjusting for possible confounding and risk factors for a two-year follow up. Instrumental variable analysis (IVA) was used to address potential biases associated with measured and unmeasured confounding variables. RESULTS: Of the 153 patients with stroke, 80 (10.7%) were from the pneumococcal pneumonia cohort, and 73 (4.9%) were from the control group. The risk of stroke was 3.65 times higher (95% confidence interval, 2.25–5.90; P<0.001) in patients with pneumococcal pneumonia after adjusting for patient characteristics, co-morbidities, geographic region, urbanization level of residence, and socioeconomic status during the first year. IVA showed an additional 14% risk of stroke for pneumococcal pneumonia patients (odds ratio = 1.14; 95% CI, 1.02–1.26, P = 0.032). CONCLUSIONS: Patients with pneumococcal pneumonia carry an increased risk for stroke than the general population. Further studies are warranted for developing better diagnostic and follow-up strategies for patients with increased risk.