Heat-Related Mortality among Older Adults: Spatial Patterns and Relationships between Urban Heat Islands, Tree Canopy Cover, and Building Fraction

Sammanfattning

With a warming climate and most of the population living in urban areas, heat exposure due to the urban heat island (UHI) poses a significant threat to human health. This study examines the spatial relationships between UHI, tree canopy cover (TCC), and building fraction (BF) and their influence on heat-related mortality among older adults (≥65 years) in Gothenburg and Stockholm, Sweden.TCC and BF were calculated, and UHI was modelled, all aggregated at the Demographic Statistical Areas (DeSO) level. Areas were subsequently classified as high or low for each variable. Poisson regression was used to examine the relationship between high and low areas and mortality on optimal and heat days.The results showed that the highest UHI and BF, and lowest TCC are found in urban centres in both Gothenburg and Stockholm. The strongest spatial relationship among the variables was found for UHI and BF (R2 = 0.86). The overall risk of dying was found to be 7% higher on heat days than on optimal days. Between the high/low classes, no statistical significance was found for any variables, but a trend was found showing high UHI and BF and low TCC being associated with higher heat-related mortality risk. The small differences between the three variables in relation to mortality suggest the possibility of using TCC or BF as a proxy in planning and policy instead of UHI, for more accessible and actionable indicators.