Comorbid pulmonary disease and risk of community-acquired pneumonia in COPD patients.

Methods: Risk of pneumonia in chronic obstructive pulmonary disease (COPD) patients due to comorbid pulmonary disease is not well understood.

Objective: To compare factors associated with risk of community-acquired pneumonia (CAP) in COPD patients for those with and without lung cancer, bronchiectasis and/or history of active tuberculosis.

Methods: Retrospective chart review of patients diagnosed with COPD (forced expiratory volume in 1 second/forced vital capacity < 0.70) between 2006 and 2010, including patient characteristics, occurrence of CAP and type of inhalation treatment. Pneumonia-free survivals were assessed using Kaplan-Meier curves. Factors associated with CAP were assessed using Cox's proportional hazard regression and expressed as adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs).

Results: Of 2630 patients, 402 (15.3%) developed CAP during follow-up. The likelihood of CAP increased with increased age (aHR 1.03, 95%CI 1.02-1.04), lower body mass index (BMI; aHR 0.97, 95%CI 0.95-1.00), lung cancer (aHR 3.81, 95%CI 2.88-5.05), bronchiectasis (aHR 2.46, 95%CI 1.70-3.55) and inhaled corticosteroid (ICS) containing treatment (aHR 1.60, 95%CI 1.30-1.96). ICS-containing treatment was associated with increased risk of CAP only for patients without comorbid pulmonary disease (aHR 1.68, 95%CI 1.30-2.17).

Conclusions: For COPD patients: 1) increased age, low BMI, lung cancer and bronchiectasis may increase the risk of CAP, and 2) without respiratory comorbid disease, ICS use increases the risk of CAP.