Our analysis of national data suggests that the prevalence of parent- or carer reported childhood asthma in Australia is clustered geographically. We further demonstrated that higher area-level asthma prevalence was associated with both higher area-level socioeconomic disadvantage and Indigenous people density. These findings point to potential geographic areas for focused interventions to lessen the burden of childhood asthma, with priorities set according to the sociodemographic characteristics of local populations.

Geographical clustering of childhood asthma prevalence indicates that a higher prevalence of asthma appears to cluster regionally. Substantial hot spots were mostly observed in regional or remote areas of New South Wales, Victoria, Queensland, and Tasmania. It is supported by prior research indicating that childhood asthma is more prevalent in inner-regional areas than in major cities [30]. These findings can be attributed to environmental features including socioeconomic deprivation, race or ethnicity, pollen, dust, exhaust pollutants, air pollution, violence, or crime, as well as limited access to healthcare because the majority of specialised paediatric asthma services are located in tertiary metropolitan hospitals [9,10,11,12, 31]. Research indicates that areas with low median household incomes, a high non-White population, and a high percentage of households without vehicles are associated with a high asthma hotspot [31]. Areas with high asthma prevalence had far more crime activity [14, 31]. Asthma hotspots also exhibit limited physician access [31]. There is a need for further research to assess environmental features related to geographic variation in childhood asthma in Australia. Environmental influence is better described by socioecological frameworks, which postulate that individual health and behaviour are subject to and influenced by a complex web of influences at both individual (intrapersonal) and environmental levels (interpersonal, institutional, community, and policy). The frameworks can explain the findings of this study, which assessed area-level (i.e., community-level) factors related to the spatial patterning of childhood asthma.

Our results show that areas with higher socioeconomic deprivation had a significantly higher prevalence of childhood asthma than areas with less socioeconomic deprivation, which is supported by earlier research [30]. Children residing in socially deprived areas may be more likely to have asthma due to negative environmental exposures that directly and indirectly exacerbate asthma [32]. One possible mechanism is psychosocial stress produced by local environments [32]. For example, crime is often concentrated in socioeconomically deprived areas [33], leading parents to perceive neighbourhoods as unsafe. This view may lead to children being kept indoors, increasing their exposure to allergens and harmful behaviours that can aggravate asthma [31]. Research shows that parental perceptions of neighbourhood unsafety are related to childhood asthma morbidity [34]. Other factors that might cause or intensify psychosocial stress include but are not limited to neighbourhood poverty, unemployment, substandard housing, limited access to healthcare, and greater exposure to environmental pollutants. Neighbourhoods with high levels of deprivation are typically marked by low levels of education and income, poor housing conditions, limited access to healthcare, and increased exposure to environmental pollutants, which consequently put children at higher risk of asthma [35,36,37]. However, we were unable to test these potential mechanisms in this study.

This study found that areas with a high proportion of Indigenous people had a higher childhood asthma prevalence. Asthma prevalence is higher among Indigenous communities in Australia [38], and previous research has reported that asthma is a significant cause of morbidity and the most prevalent chronic respiratory condition among Indigenous populations, supporting this finding [39, 40]. Various factors can contribute to the high asthma prevalence, including smoking, limited access to culturally appropriate health services, and social-environmental factors [40, 41]. For example, low income can lead to poor living conditions and exposure to environmental asthma triggers such as household moulding or air pollution, as well as limited access to healthcare resources and medications, resulting in poor asthma control and a high prevalence. According to a Western Australian study, the prevalence of asthma in Aboriginal children rises with decreasing household income [40]. Moreover, the marginalisation of Indigenous populations in disadvantaged neighbourhoods can be attributed to broader, ongoing political, economic, and social determinants of health due to the ongoing impacts of colonisation. This marginalisation often leads to increased stress levels among these populations, which in turn can contribute to higher rates of disease morbidity.

Australia has universal healthcare coverage for all citizens and eligible residents, which minimises healthcare access barriers. Research, however, suggests that environmental risk factors may contribute to the prevalence of asthma in children, even in countries with universal healthcare coverage [42]. Briefly, neighbourhood-level environmental features can contribute to neighbourhood-level variation in asthma among children by creating barriers to adequate prevention and management strategies, as well as by increasing exposure to environmental triggers for asthma. Children living in socioeconomically disadvantaged neighbourhoods have a higher likelihood of experiencing repeated visits to the emergency department due to asthma [35]. This suggests that there may be issues with asthma management, and the presence of asthma triggers. For example, managing environmental tobacco smoke and asthma triggers (e.g., dust mites) can be more challenging in public housing than in private homes, and most of the public housing is in socioeconomically deprived areas [43,44,45].

This study has several strengths. First, we analysed the percentage of children with asthma at a smaller geographical area level, encompassing the entirety of Australia. Secondly, the census data encompass all Australian children, unlike health surveys, which rely on a sample of the population and have limited ability to investigate small area variations. Moreover, this research employed small area spatial analysis, which allowed for a more comprehensive assessment of the spatial patterns of childhood asthma (i.e., localised variation, identifying high- or low-risk areas) and the underlying reasons, which could help public health initiatives. While our exploratory spatial analysis aids in the investigation of spatial variation in and clustering of childhood asthma, spatial regression analysis provides insight into the environmental predictors of spatial variation in childhood asthma.

This research has some limitations as well. This ecological study examines associations rather than causal relationships between environmental features and asthma prevalence. It has been suggested that parents- or carers who experience financial distress at home are more likely to report asthma morbidity in their children [46]. Therefore, the use of parents- or carer reported data for asthma in children may introduce reporting bias and may not be the most reliable method for diagnosing asthma. However, it is a widely used methodology in childhood asthma epidemiology [47]. Even though pollen, dust, climate characteristics, and household environments (e.g., smoking, allergens, mould) may contribute to asthma geographic variation, the census did not collect data on them, limiting our ability to investigate their impacts. The census was done in 2021 which coincided with the COVID-19 pandemic years. We know asthma health care utilisation was reduced in Australia during the pandemic which may have led to an estimation of a lower prevalence of asthma (the primary outcome of this analysis) [48]. However, respondents were asked if they were ever diagnosed with asthma by a physician. In addition, the pandemic presented challenges in conducting censuses. Nevertheless, by implementing effective planning and risk management strategies, such as conducting thorough testing of procedures and systems during the 2020 Census Test, the disruptions caused by the pandemic to Census field operations were mitigated, resulting in minimal impact on the accuracy and reliability of Census data [49]. In 2021, the implementation of new online self-service options aimed at enhancing the census experience gained popularity among Australian households. These options played a critical role in reducing the impact of pandemic restrictions on the distribution of census forms and other fieldwork activities [49].

This study documents significant spatial clustering of childhood asthma in Australia and highlights that prevalence of asthma is higher in some communities and in socioeconomically disadvantaged communities. This key finding can inform resource allocation and the development of strategies to minimise the inequitable burden of childhood asthma in these communities. It is crucial to employ multilevel strategies; for instance, the combined effects of environment-enhancing strategies (such as healthcare accessibility) and individual-directed interventions (such as parental counselling) are likely to be more impactful than those of either strategy alone. Through the lens of socioecological frameworks, which address and acknowledge the complex causes and consequences of health disparities, and highlight multiple levels of influence that direct the focus of health promotion programs, these strategies can be better understood. At an individual level, this could involve evidence-based proactive multi-dimensional comprehensive asthma care for children in these communities [50]. At the environmental level, this could involve initiatives to address external environmental and socioeconomic determinants of health. Overall, implementing comprehensive asthma interventions that involve children, their parents or carers, the communities they live in, and the healthcare systems can potentially enhance health outcomes for Australian children with asthma.