Measuring exacerbations in subjects with mild to moderate COPD from a population-based cohort: The CanCOLD study

Rationale: There is no information on COPD exacerbations in subjects with mild to moderate COPD sampled from the general population. Objective: To assess in a population-based sample the frequency and characteristics of COPD exacerbations. Methods: Canadian Cohort Obstructive Lung Disease (CanCOLD) is a longitudinal, multi-center study, 1600 subjects ≥ 40 years old, identified by random digit dialling from the general population. Subjects are sex- and age-matched, and grouped as: 1) COPD moderate + (GOLD≥ 2); 2) COPD mild (GOLD 1); 3) subjects at risk (ever smoker); 4) healthy subjects (never smoker, no obstruction). An exacerbation questionnaire is administered at baseline and every 3 months to capture changes in respiratory symptoms, medication, work and health service use. Results: From a preliminary analysis of 182 subjects, 35 were normal, 30 at risk, 62 GOLD 1 and 55 GOLD ≥2. Exacerbations at baseline were reported by 2 at risk, 2 GOLD 1 and 9 GOLD ≥2 subjects, suggesting a prevalence of 9% in this cohort. GOLD 1 and at-risk subjects experienced similar worsened respiratory symptoms, but no change in medication, work or health service use. GOLD ≥2 subjects experienced more symptoms, and changes in medication, work and health service use. Conclusions: Based on these preliminary data, COPD exacerbations are reported in a minority of COPD subjects sampled from the population. Exacerbations occur, and are similar in at-risk and GOLD 1 subjects, however in GOLD ≥2 subjects they are more common and have a greater impact. Longitudinal evaluation will be of great value.