Fine-Scale Spatio-Temporal Patterns in the Heat-Related Health Burden Within California (2006-2019): The Role of Structural Racism and Environmental Injustice

Climate change has amplified health consequences from heatwave exposure, resulting in the exacerbation of existing inequities from structural racism and environmental discrimination. Even so, research has not adequately prioritized the examination of heatwave impacts on morbidity at refined spatial scales alongside the characterization of specific or intersectional community characteristics that relate to these injustices. This study examined the spatio-temporal relationship between the exposure to 27 heatwave definitions and acute care utilizations from 2006 to 2019 across California ZIP code tabulation areas (ZCTAs) and assessed how 145 community characteristics may influence susceptibility. A within-community matched design paired with a spatial Bayesian hierarchical model considered variation in these associations at a fine spatial scale, and a random effects meta-regression was applied to evaluate their modification by community characteristics. Across the state, the 1-day 95th percentile of maximum temperature definition was found to have the greatest population attributable number (29,723; 95% CI: 27,691, 31,722). Predominantly positive relationships were identified at the ZCTA level, where both the Central Valley and Southern California were the most impacted regions. Communities experiencing certain social, cultural, and economic discrimination, particularly those with higher proportions of American Indian/ Alaska Native male residents under 5 years old, residents using the Supplemental Nutrition Assistance Program (SNAP), and Asian male residents, were observed to be the most susceptible to heat-related health impacts. These findings may support future efforts to elucidate underlying mechanisms of heat-related health disparities and inform heat action plans that prioritize the most affected communities to reduce their health burden.