Hospitalization rates and survival associated with COPD: a nationwide Danish cohort study

We examined rates of first hospitalization for COPD, rates of 5-year mortality among patients hospitalized for COPD, and comparisons of mortality between COPD patients and a matched cohort free of COPD. We computed standardized rates of first COPD hospitalization. Using Cox regression, we compared 180- and 181-day to 5-year mortality among COPD patients with the comparison cohort. We used medical databases in Denmark (population 5.4 million) from 1997 to 2006. We included patients 40 years or older with first hospitalization for COPD (64,499) and an age- and gender-matched comparison cohort of persons without COPD hospitalization (322,495). We examined the incidence of COPD hospitalization and risks and rates of mortality in the 5 years after hospitalization. Standardized rates of first hospitalization for COPD declined from 276 per 100,000 person-years in 1999 to 231 per 100,000 person-years in 2006. Within 180 days of hospitalization, 16% of COPD patients and 2.4% of persons in the matched cohort died (adjusted hazard ratio = 7.00, 95% CI = 6.79-7.22). Between 181 days and 5 years, 46% of COPD patients who survived the first 180 days and 19% of persons in the comparison cohort died (adjusted hazard ratio = 2.91, 95% CI = 2.86-2.95). COPD and comorbid diseases interacted to increase mortality in the first 180 days, but not thereafter. COPD continues to be a major public health problem causing substantial mortality in the 5 years after hospitalization, particularly in the first 180 days and in patients with comorbid diseases.