Chronic obstructive pulmonary disease and hospitalizations for pneumonia in a US cohort.

OBJECTIVE: To better understand risk factors for pneumonia hospitalizations in people with impaired lung function.
METHODS: We analyzed longitudinal data from participants in the Atherosclerosis Risk in Communities Study (ARIC) and the Cardiovascular Health Study (CHS). We limited our analysis to 20,375 participants aged 45 and older at baseline. We stratified the sample based on prebronchodilator baseline lung function data, according to modified GOLD criteria, including a "restrictive" category (FEV(1)/FVC>70% and FVC<80%). We defined "pneumonia" as a hospitalization with a pneumonia discharge diagnosis (ICD-9 codes 480-486) within 36 months. We used Cox proportional hazard models to determine pneumonia risk associated with COPD stage, adjusting for age, sex, race, smoking status and comorbid disease (diabetes mellitus or cardiovascular disease at the baseline examination).
RESULTS: Pneumonia hospitalization risk was associated with older age, male gender, comorbid conditions, smoking status, and level of lung function impairment. Overall, people with normal lung function had the lowest pneumonia hospitalization rate (1.5 per 1000 person-years) and those with GOLD stage 3 or 4 COPD had the highest rate (22.7 per 1000 person-years). After adjusting for other potential confounding factors, GOLD stages 3 or 4 and 2 COPD were associated with an increased risk of pneumonia (hazard ratio [HR] 5.65, 95% confidence interval [CI] 3.29, 9.67 and 2.25 (1.35, 3.75), respectively) relative to normal lung function.
CONCLUSION: COPD severity (GOLD stage) is an important and independent predictor of pneumonia hospitalizations in this cohort.