Background: There is still a lack of data on the seasonality of exacerbations of COPD based on large randomized studies using COPD exacerbations as primary end points. The objective of this study was to assess the seasonal pattern of moderate and severe exacerbations and analyze the influence of associated baseline factors. We also determined the timing of second exacerbations and the potential impact of the 2009 influenza A(H1N1) pandemic on exacerbations.
Methods: Analyses of exacerbation rates across treatment groups were adjusted for differing times on treatment by means of descriptive statistics based on the 1-year Prevention of Exacerbations with Tiotropium in COPD (POET-COPD) trial, in which exacerbations were the primary end point.
Results: Of the 7,376 patients who were randomized, a total of 4,411 exacerbations were reported in 2,691 patients. Mean monthly exacerbation rates during winter were 2.16-fold higher than during summer, regardless of baseline characteristics (age, sex, COPD severity, smoking status, BMI, inhaled corticosteroid use, cardiovascular comorbidity, concomitant cardiovascular medication). Second exacerbations after a previous event in October to March occurred 1 month earlier than during the warmer half of the season. The portion of exacerbation-related hospitalizations remained constant throughout the year. Most exacerbations were treated with antibiotics and reached a peak in the colder season. All-cause mortality showed a seasonal pattern similar to exacerbations. The 2009 A(H1N1) pandemic was not associated with an increase in exacerbation rates or deaths.
Conclusions: This analysis presented a marked impact of season on exacerbation outcomes, antibiotic treatment, timing of second exacerbations, and all-cause mortality.
Trial registration: ClinicalTrials.gov NCT00563381.