A temporal decline in asthma but not eczema prevalence from 2000 to 2005 at school entry in the Australian Capital Territory with further consideration of country of birth

Abstract

Background: Asthma prevalence has declined in some countries over the past 10 years. Most reports have been based on population surveys conducted at two points of time in a given location. Comparisons across countries and time periods can be limited by differences in study methodology or disease diagnostics in different communities. Here, we examined trends in asthma prevalence using serial annual data and further examine the importance of country of birth. Methods: The source population has children aged 4-6 commencing school in the Australian Capital Territory from 2000 to 2005 inclusive. Over 80% of these children and their families completed a health questionnaire on asthma, other atopic disease and respiratory symptoms using some questions from the International Study of Asthma and Allergies in Childhood (n = 22 882). Current asthma has been previously validated against physician assessment in this setting. Results: The prevalence of current asthma declined (P < 0.001) but eczema ever increased (P < 0.001) from 2000 to 2005. The asthma decline was predominantly linear in form, and accompanied by a reduction in night cough and shortness of breath but not recent wheeze. Compared with Australian-born children, children from New Zealand and the United Kingdom had a similar prevalence of asthma, hay fever and eczema history. However, children born in other countries, such as Asia, generally had a lower prevalence of these disorders. The temporal trends for atopic disorders or respiratory symptoms did not differ for overseas-born compared with Australian-born children. Conclusion: The decline in current asthma prevalence from 2000 to 2005 was linear in form and appeared uncoupled from trends in child eczema. Country of birth was associated with marked variation in atopic disorder prevalence. The similar temporal trends for Australian vs overseas-born children indicate that the factors underlying the asthma prevalence decline are unlikely to be only in the pre-natal period.