Risk of empyema in patients with COPD.

Objective: Pneumonia is one of the most common infectious diseases in patients with COPD. The risk of empyema in COPD is controversial, and its incidence has not been reported. The aim of our study was to determine the risk of empyema in COPD patients and to assess its risk factors. Patients and methods: We used the National Health Insurance Research Database in Taiwan to conduct an observational cohort study. This study analyzed patients who were diagnosed with COPD between January 1, 2003 and December 31, 2009. The earliest date of COPD diagnosis was designated the index date. Patients who were younger than 40 years or had empyema before the index date were excluded. Results: We analyzed 72,085 COPD patients in our study. The incidence of empyema was higher in the COPD group than in the non-COPD group (15.80 vs 4.34 per 10,000 person-years). The adjusted hazard ratio for empyema was 3.25 (95% CI =2.73-3.87) in patients with COPD compared with patients without COPD. COPD patients with only comorbidity of stroke, cancer, and chronic renal disease had adjusted hazard ratios of 1.88, 4.84, and 3.90, respectively. Conclusion: The likelihood of developing empyema is higher in patients with COPD than in those without COPD. Some comorbidities, such as stroke, cancer, and chronic renal disease, are associated with an elevated risk for empyema in COPD patients.