Risk factors for the development of asthma between age 4 and 7 years in a national cohort study

Abstract

Background: The risk of developing asthma is associated with genetic, environmental and lifestyle factors. The aim of this study was to estimate the incidence of, and examine risk factors for developing, asthma using data from the child cohort of the Longitudinal Study of Australian Children. Methods: The child cohort (aged 4–5 years at baseline) was recruited in 2004 and re-assessed two years later via face-to-face interviews with the primary carer. Asthma diagnosis was ascertained from the question “Has a doctor ever told you that your child has asthma?”. Multivariate logistic regression was used to examine associations between risk factors reported at baseline and new asthma diagnosis two years later among children with no diagnosis of asthma at baseline. Results: At baseline, 20% of children aged 4–5 years had ever-diagnosed asthma and the estimated incidence of newly diagnosed asthma over the next two years was 8.6%. Independent risk factors significantly (p≤0.013) associated with new asthma diagnosis among 6–7 year olds were wheeze (OR=3.0); food/digestive allergies (OR=2.3); and neonatal intensive care after birth (OR=1.6). No association was observed for eczema, passive smoke exposure, ever breastfed, no siblings, 1+ pets in household, English-speaking primary carer, socioeconomic disadvantage, sex or overweight/obesity. Conclusions: While several of the observed associations are similar to those reported in comparable populations elsewhere, the lack of association with sex, passive smoke exposure, and breastfeeding status suggests that these factors do not have an impact on the incidence of asthma after early childhood.