To what extent is air pollution associated with cardiorespiratory hospitalisations across Australia? A whole-of-population ecological study

OBJECTIVES AND IMPORTANCE OF STUDY: This study aimed to examine the extent to which residential ambient air pollution across Australia, globally a relatively low-pollution setting, is associated with cardiovascular and respiratory hospitalisations. STUDY TYPE: A national, cross-sectional, ecological study. METHODS: This whole-of-population study used national air pollution estimates from 2016 and administrative hospitalisation data aggregated across 1155 public health areas from 2016 to 2017, representing 23,236,046 of the Australian population. Population-weighted median concentrations from 2016 of particulate matter ≤2.5 µm (PM2.5; 6.4 µg/m3) and nitrogen dioxide (NO2; 4.4 ppb) were estimated using validated satellite-based land use regression models. Cardiorespiratory hospitalisations (June 2016 to June 2017) were sourced from national administrative data from all hospitals for each public health area. Incidence rate ratios for hospitalisations were estimated for an interquartile range increase in each air pollutant using mixed regression models (age-standardised, adjusted for obesity, smoking, rural/urban and disadvantage) stratified by sex. The population-attributable fraction for each pollutant was estimated across ideal exposure scenarios (5th, 10th and 25th percentile of each pollutant) at each public health area. RESULTS: PM2.5 and NO2 exposure were consistently associated with greater hospital admissions for cardiovascular and respiratory diseases across both males and females, with estimated incidence rate ratios ranging from 1.02 to 1.06. Across both pollutants, estimated population attributable fractions ranged from 0.9 to 3.9% for cardiovascular diseases, and 1.8 to 7.5% for respiratory diseases. CONCLUSIONS: Despite Australian air pollution levels being relatively low compared with other countries, we observed consistent associations with cardiorespiratory hospitalisations. Given the mounting evidence that air pollution negatively impacts cardiorespiratory health, policies should continuously target air pollution reduction.