The natural history of community-acquired pneumonia in COPD patients: a population database analysis.

Background: Patients with Chronic Obstructive Pulmonary Disease (COPD) are at higher risk of developing Community-Acquired Pneumonia (CAP) than patients in the general population. However, no studies have been performed in general practice assessing longitudinal incidence rates for CAP in COPD patients or risk factors for pneumonia onset.
Methods: A cohort of COPD patients aged ≥ 45 years, was identified in the General Research Practice Database (GPRD) between 1996 and 2005, and annual and 10-year incidence rates of CAP evaluated. A nested case-control analysis was performed, comparing descriptors in COPD patients with and without CAP using conditional logistic regression generating odds ratios (OR) and 95% confidence intervals (CI).
Results: The COPD cohort consisted of 40,414 adults. During the observation period, 3149 patients (8%) experienced CAP, producing an incidence rate of 22.4 (95% CI 21.7-23.2) per 1000 person years. 92% of patients with pneumonia diagnosis had suffered only one episode. Multivariate modelling of pneumonia descriptors in COPD indicate that age over 65 years was significantly associated with increased risk of CAP. Other independent risk factors associated with CAP were co-morbidities including congestive heart failure (OR 1.4, 95% CI 1.2-1.6), and dementia (OR 2.6, 95%CI 1.9-3.). Prior severe COPD exacerbations requiring hospitalization (OR 2.7, 95% CI 2.3-3.2) and severe COPD requiring home oxygen or nebulised therapy (OR 1.4, 95% CI 1.1-1.6) were also significantly associated with risk of CAP.
Conclusion: COPD patients presenting in general practice with specific co-morbidities, severe COPD, and age >65 years are at increased risk of CAP.
(Copyright © 2012 Elsevier Ltd. All rights reserved.)