Incidence of utilization- and symptom-defined COPD exacerbations in hospital- and population-recruited patients.
OBJECTIVE
The objectives of this study were to estimate the impact of recruitment source and outcome definition on the incidence of acute exacerbations of COPD (AECOPD) and explore possible predictors of AECOPD.


METHODS
During a 1-year follow-up, we performed a baseline visit and four telephone interviews of 81 COPD patients and 132 controls recruited from a population-based survey and 205 hospital-recruited COPD patients. Both a definition based on health care utilization and a symptom-based definition of AECOPD were applied. For multivariate analyses, we chose a negative binomial regression model.


RESULTS
COPD patients from the population- and hospital-based samples experienced on average 0.4 utilization-defined and 2.9 symptom-defined versus 1.0 and 5.9 annual exacerbations, respectively. The incidence rate ratios for utilization-defined AECOPD were 2.45 (95% CI 1.22-4.95), 3.43 (95% CI 1.59-7.38), and 5.67 (95% CI 2.58-12.48) with Global Initiative on Obstructive Lung Disease spirometric stages II, III, and IV, respectively. The corresponding incidence rate ratios for the symptom-based definition were 3.08 (95% CI 1.96-4.84), 3.45 (95% CI 1.92-6.18), and 4.00 (95% CI 2.09-7.66). Maintenance therapy (regular long-acting muscarinic antagonists, long-acting beta-2 agonists, inhaled corticosteroids, or theophylline) also increased the risk of AECOPD with both exacerbation definitions (incidence rate ratios 1.65 and 1.73, respectively). The risk of AECOPD was 59%-78% higher in the hospital sample than in the population sample.


CONCLUSIONS
If externally valid conclusions are to be made regarding incidence and predictors of AECOPD, studies should be based on general population samples or adjustments should be made on account of a likely higher incidence in other samples. Likewise, the effect of different AECOPD definitions should be taken into consideration.
Department of Thoracic Medicine, Haukeland University Hospital; Department of Clinical Science, University of Bergen.
Marta
M
Erdal
Department of Global Public Health and Primary Care, University of Bergen, Bergen, Norway.
Ane
A
Johannessen
Department of Thoracic Medicine, Haukeland University Hospital; Department of Clinical Science, University of Bergen.
Tomas Mikal
TM
Eagan
Department of Clinical Science, University of Bergen.
Per
P
Bakke
Department of Clinical Science, University of Bergen.
Amund
A
Gulsvik
Department of Thoracic Medicine, Haukeland University Hospital; Department of Clinical Science, University of Bergen.
Rune
R
Grønseth
D000368:Aged; D001993:Bronchodilator Agents / Q000627:therapeutic use; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D018450:Disease Progression; D005260:Female; D006295:Health Resources / Q000706:statistics & numerical data*; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009664:Norway / Q000453:epidemiology; D018579:Patient Selection; D011446:Prospective Studies; D029424:Pulmonary Disease, Chronic Obstructive / Q000145:classification / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology*; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors
D001993:Bronchodilator Agents
COPD; exacerbations; general population; predictors