Understanding environmental factors associated with crowd-sourced symptoms of asthma, and hayfever in Tasmania and the Australian Capital Territory; 2015-2022

<p dir="ltr">Asthma and allergic rhinitis (hayfever) cause a significant disease burden both globally and in Australia. We investigated the spatial distribution of symptom reports logged by users of the smartphone app ‘AirRater’ to provide insights into the geographic pattern of asthma and hayfever symptoms within Tasmania and the Australian Capital Territory (ACT), which represent two regions of south-eastern Australia with very high asthma and hayfever prevalence. In each region, we examined the association between symptom reports and environmental triggers from 2015-2022 using symptom data from the AirRater app and meteorological records. We used the Getis-Ord Gi* and Geographically Weighted Regression (GWR) to investigate symptom hotspots, space-time trends and spatial associations between symptom reports and several environmental variables including fine particulate matter (PM2.5), temperature, pollens, precipitation, and relative humidity from 2015-2022. We found distinct spatial distributions of symptom reports within Tasmania and the ACT. Specifically, we identified multiple statistically significant symptom hotspots and coldspots in Tasmania's larger urban areas. In contrast, the ACT, which is smaller in size with just one major city, exhibited a more uniform distribution of symptom reports with no statistically significant symptom hotspots and coldspots. Our GWR analysis in Tasmania found that temperature, precipitation, relative humidity, PM2.5, and pollen all demonstrated weak spatial associations with symptom reports but explained very little of the geographic variation in symptom reporting. The relatively weak associations found between these environmental factors and symptom reports imply that other factors, including individual characteristics, local socio-economic and contextual influences, may significantly contribute to shaping the spatial patterns of symptom reports. The space-time pattern in Tasmania reveals inconsistent spatial variations in symptom reports, hotspots, and coldspots at the Local Government Area (LGA) level from year to year. To improve our understanding of the limited spatial variability apparent in our findings, further research is essential. This additional investigation aims to enhance our knowledge of the regional spatial and spatiotemporal variations in symptom reports, ultimately informing the necessity for targeted public health interventions in specific geographic areas for these conditions. </p>