Risk of developing pleural empyema in patients with stroke: a propensity-matched cohort study

Pleural empyema is an important complication of pneumonia. Patients with stroke are at a higher risk developing pneumonia; however, the association between stroke and pleural empyema risk is largely unknown. We used the data from the National Health Insurance Research Database of Taiwan to establish a stroke group consisting of 466,170 patients diagnosed between 2000 and 2010, and a non-stroke group consisting of the same number of individuals matched by the propensity score. Incident pleural empyema was monitored toward the end of 2011. Adjusted hazard ratios (aHRs) of pleural empyema in the stroke group, compared to the non-stroke group, were estimated using the Cox proportional hazards model. We found that the incidence of pleural empyema is 2.69-fold higher in the stroke group than in the non-stroke group (15.2 vs. 5.59/10,000 person-years, p < 0.001), with an aHR of 2.89 [95% confidence interval (CI) = 2.72-3.08]. Further analysis reveals the aHRs of pleural empyema to be 2.62 (95% CI = 2.45-2.79) in patients with ischemic stroke and 4.53 (95% CI = 4.14-4.95) in patients with hemorrhagic stroke compared with those without stroke. In addition, we observe that stroke patients with ventriculoperitoneal (VP) shunt implantation exhibit more than sevenfold risk for developing of pleural empyema. In conclusion, patients with stroke are at an elevated risk of developing pleural empyema. The risk is greater for those with hemorrhagic stroke than for those with ischemic stroke. The risk increases further for patients who undergo VP shunt implantation.