Hospital readmissions for asthma in children and young adults in Canada.

To examine the incidence rate of hospital readmission for asthma in relation to sex and age among Canadian children and young adults, we used data from 86,863 subjects under age 20 years when they had a first admission for asthma as 1 of first 5 diagnoses in Canada between April 1, 1994 and March 31, 1997. We calculated age- and sex-specific incidence rates, and used the Cox proportional hazards model for multivariate analysis. Of these subjects, 20,277 (23.3%) were readmitted to hospital for asthma during the study period. After adjusting for length of stay for first admission and province, the rate ratio for females vs. males was 0.86 for those under age 1 year, and close to unity for the 1-4-year and 5-9-year age groups, whereas it was 1.47 and 1.35 for the 10-14-year and 15-19-year age groups, respectively. The data showed similar trends for rehospitalization asthma as a primary diagnosis. The incidence rate of rehospitalization showed little sex difference between ages 1-9 years, but was markedly higher in females than in males 10-19 years of age. Airway size, female hormonal changes, increased use of cosmetic products, and cigarette smoking among adolescent girls may contribute to the age- and sex-differences in adolescence. Copyright 2003 Wiley-Liss, Inc.