Hospitalization rate and 30-day mortality among patients with status asthmaticus in Denmark: a 16-year nationwide population-based cohort study

OBJECTIVE Current data on hospitalization and prognosis of acute asthma and status asthmaticus are inconclusive. We aim to analyze the rate of first-time hospitalizations for status asthmaticus among patients of all ages, the proportion admitted to intensive care units (ICU), and the 30-day mortality over a 16-year period. METHODS In this population-based cohort study, we used medical registries to identify all first-time status asthmaticus hospitalizations in Denmark from 1996 through 2011. Data on comorbidities were also obtained. We computed yearly hospitalization rates overall and by gender and age groups, and estimated the proportion requiring ICU admission. We estimated 30-day age- and gender-standardized mortality. We examined potential misclassification from acute exacerbation of chronic obstructive pulmonary disease (COPD) by excluding patients with preexisting or concurrent COPD. RESULTS Of the 5,001 patients identified with a first-time status asthmaticus hospitalization, 50.5% were male, 40.3% were <15 years old, and 12.4% had comorbidity. The hospitalization rate increased from 48.0 per 1,000,000 person-years (PY) (95% confidence interval [CI]: 45.1-51.1 PY) during 1996-1999 to 70.1 per 1,000,000 PY (95% CI: 66.7-73.7 PY) during 2008-2011. This may be explained by an increased hospitalization rate of children. The standardized 30-day mortality risk declined from 3.3% (95% CI: 2.5%-4.1%) in 1996-1999 to 1.5% (95% CI: 0.9%-2.1%) in 2008-2011. During 2005-2011, 10.1% of status asthmaticus patients were admitted to the ICU. Hospitalization rates and mortality risk decreased by excluding 939 patients also registered with COPD, but overall temporal changes did not change. CONCLUSION From 1996 to 2011, status asthmaticus hospitalization rate increased but remained below 100 hospitalizations per 1,000,000 PY. Thirty-day mortality risk was halved to less than 2%.