Risk of asthma in children with a history of croup.

All fourth-grade school children in Munich and the surrounding districts (age 9-11 years, n = 9403) were surveyed with a questionnaire, lung function testing and bronchial provocation. Croup was reported in 9.8%. In these children, lung function was decreased even after controlling for asthma and other confounding factors. Only recurrent croup had an increased prevalence in children with asthma. When a family history for asthma, maternal smoking and social status were included into a logistic multiple regression model, the odds ratio to develop asthma was 2.91 (confidence interval (CI) 2.19 - 3.86) for children with a history of croup, 2.60 (CI 1.93 - 3.51) for a family history for asthma and 8.60 (CI 4.99 - 14.80) for the combination of family history and croup. Asthma was diagnosed in 37.3% of children with croup and a positive family history.