Caregiver perceptions of neighbourhood green space quality, heavy traffic conditions, and asthma symptoms: Group-based trajectory modelling and multilevel longitudinal analysis of 9,589 Australian children

Background: This study assessed the associations between changes in exposure to green space quality, heavy traffic conditions, and asthma symptoms among children. Methods: 10-year cohort data of 9589 children, retrieved from the Longitudinal Study of Australian Children, were analysed. Caregiver-reported neighbourhood green space quality, heavy traffic conditions, and asthma symptoms were measured biennially. Group-based trajectory mixture models were used to develop trajectory groups, denoting different patterns of, or changes in, exposure to green space quality, heavy traffic conditions, and asthma symptoms across childhood. Multilevel multinomial logistic regression was used to identify factors associated with trajectory group membership and examine the confounders-adjusted associations between trajectory groups of green space quality, heavy traffic conditions, and asthma symptoms. Results: Four trajectory groups for each green space quality and heavy traffic conditions, and five trajectory groups for asthma symptoms were developed. Children in less disadvantaged areas were more likely to be in trajectory groups with exposure to quality green space, but less likely to be exposed to heavy neighbourhood traffic. Living in more remote areas was associated with the decreased likelihood to be in groups with exposure to both quality green space and heavy traffic conditions over time. Accumulation of exposure to quality green space across childhood was not found to be protective against asthma symptoms. However, children whose caregiver perceptions of heavy traffic conditions trended from low to moderate levels; or were consistently in high levels across childhood had a higher likelihood to be in trajectory groups with a higher risk of asthma symptoms. Conclusion: Exposure to quality green space was not associated with the reduced risk of asthma symptoms. The accumulation of exposure to heavy traffic conditions increased the likelihood of asthma symptoms among children. Reducing the presence of heavy traffic in neighbourhoods might reduce the risk of childhood asthma.