Objective: To compare the prevalence and severity of asthma and of allergic sensitisation in children in different regions. We hypothesised that regions with different standardised hospital admission rates would have different prevalences of childhood asthma and that diverse climates would result in a range of sensitisations to different allergens.
Design and setting: We studied large random population samples of children in seven regions in New South Wales (NSW) in 1991-1993. Hospitalisation rates were obtained from NSW Department of Health data.
Participants: 6394 children aged 8-11 years.
Outcome measures: History of respiratory symptoms by self-administered questionnaire; airway hyperresponsiveness by histamine inhalation test; and sensitisation to allergens by skin-prick tests.
Results: Children in all regions had a high prevalence of recent wheeze (22%-27%), of diagnosed asthma (24%-38%) and of use of asthma medications (22%-30%), but no region was consistently higher or lower for all measurements. The prevalence of current asthma in children living in three coastal regions (where sensitisation to house-dust mites was high) and in the far west (where sensitisation to alternaria was high) was 12%-13%, which was significantly higher than the prevalence of 7%-10% in children living in three inland regions (where sensitisation to these allergens was lower) (P < 0.01).
Conclusions: We found significant variations in the prevalence and severity of childhood asthma in NSW. The prevalence of hospitalisations, diagnosed asthma, recent symptoms and medication use may relate to different regional diagnostic patterns, whereas current asthma prevalence may relate to different levels of allergic sensitisation.