International comparison of the prevalence of asthma symptoms and bronchial hyperresponsiveness

Potential explanations for the higher rates of asthma mortality and hospital admissions in New Zealand (NZ) include greater prevalence of asthma. To evaluate this further, a large community survey has been undertaken. Rates of respiratory symptoms and bronchial hyperresponsiveness (BHR) for children in Auckland, NZ have been compared to those for children in two locations in New South Wales (NSW), Australia: Wagga Wagga (inland) and Belmont (coastal). The methodology used was the same in both studies: parent-completed questionnaire and BHR measured by response to an abbreviated histamine challenge. In Auckland, 1,084 children participated (84% of those selected) and were compared to 769 inland NSW and 718 coastal NSW children. The prevalence of respiratory symptoms, BHR, severity of BHR, and BHR combined with symptoms was similar among Auckland and inland NSW children but lower among coastal NSW children than those from the other two sites. It is concluded that other unidentified factors must be invoked to explain mortality and admission differences between these regions.