title: Rates and patterns of chronic obstructive pulmonary disease exacerbations.
abstract: BACKGROUND
  Acute exacerbations of chronic obstructive pulmonary disease (COPD) are believed to be a common occurrence in patients with COPD and are known to be associated with considerable morbidity.
  
  
  OBJECTIVE
  To describe the frequency of treated COPD exacerbations in a large population-based cohort.
  
  
  METHODS
  A cohort of newly treated patients with COPD was formed from the administrative databases of Saskatchewan Health. The outcome was the occurrence of all moderate or severe exacerbations from 1990 to 1999. Exacerbations were defined in three ways: dispensing of a prescription for a systemic antibiotic; dispensing of both a prescription for an antibiotic and a prescription for an oral corticosteroid on the same day; and requiring a hospitalization with a primary discharge diagnosis of COPD.
  
  
  RESULTS
  There were 5645 patients who entered the COPD cohort between 1990 and 1997, of whom 4453 experienced at least one exacerbation requiring treatment during follow-up. The overall rate of acute exacerbations was 1.12/person-year. It was constant across all age groups, and was similar in both men and women (1.13/person-year versus 1.11/person-year, respectively). The rate of exacerbations was highest in the first trimester of therapy for the disease (1.39/person-year) and stabilized thereafter at 1.04 exacerbations/person-year.
  
  
  CONCLUSIONS
  The results indicate that in a population-based cohort of patients with COPD, the average rate of exacerbations was 1.12/person-year. Men and women had similar rates of exacerbations.
authors.affiliation: Department of Epidemiology and Biostatistics, McGill University, Montreal, Canada.
authors.forename: Magda Nunes
authors.initials: MN
authors.lastname: de Melo
authors.forename: Pierre
authors.initials: P
authors.lastname: Ernst
authors.forename: Samy
authors.initials: S
authors.lastname: Suissa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D011792:Quebec / Q000453:epidemiology