Predictors of Exacerbations in Chronic Obstructive Pulmonary Disease - Results from the Bergen COPD Cohort Study

BACKGROUND COPD exacerbations accelerate disease progression. AIMS To examine if COPD characteristics and systemic inflammatory markers predict the risk for acute COPD exacerbation (AECOPD) frequency and duration. METHODS 403 COPD patients, GOLD stage II-IV, aged 44-76 years were included in the Bergen COPD Cohort Study in 2006/07, and followed for 3 years. Examined baseline predictors were sex, age, body composition, smoking, AECOPD the last year, GOLD stage, Charlson comorbidity score (CCS), hypoxemia (PaO2<8 kPa), cough, use of inhaled steroids, and the inflammatory markers leucocytes, C-reactive protein (CRP), neutrophil gelatinase associated lipocalin (NGAL), soluble tumor necrosis factor receptor 1 (sTNF-R1), and osteoprotegrin (OPG). Negative binomial models with random effects were fitted to estimate the annual incidence rate ratios (IRR). For analysis of AECOPD duration, a generalized estimation equation logistic regression model was fitted, also adjusting for season, time since inclusion and AECOPD severity. RESULTS After multivariate adjustment, significant predictors of AECOPD were: female sex [IRR 1.45 (1.14-1.84)], age per 10 year increase [1.23 (1.03-1.47)], >1 AECOPD last year before baseline [1.65 (1.24-2.21)], GOLD III [1.36 (1.07-1.74)], GOLD IV [2.90 (1.98-4.25)], chronic cough [1.64 (1.30-2.06)] and use of inhaled steroids [1.57 (1.21-2.05)]. For AECOPD duration more than three weeks, significant predictors after adjustment were: hypoxemia [0.60 (0.39-0.92)], years since inclusion [1.19 (1.03-1.37)], AECOPD severity; moderate [OR 1.58 (1.14-2.18)] and severe [2.34 (1.58-3.49)], season; winter [1.51 (1.08-2.12)], spring [1.45 (1.02-2.05)] and sTNF-R1 per SD increase [1.16 (1.00-1.35)]. CONCLUSION Several COPD characteristics were independent predictors of both AECOPD frequency and duration.