Urban Heat Islands and their Effect on Incident Myocardial Infarctions

BackgroundClimate change is causing an increasing number of extreme heat events, which are associated with a higher risk of cardiovascular disease (CVD)-related morbidity and mortality. Urban areas are particularly susceptible to extreme heat due to the urban heat island (UHI) effect. ObjectivesThis study investigates the effect of UHI exposure on clinically significant CVD and how this relationship changes when accounting for measures of social vulnerability. MethodsWe used publicly available data from California urban areas on a census-tract level, including the UHI index (UHII), CVD incidence as measured by the age-adjusted rate of acute myocardial infarction (MI), the Social Vulnerability Index (SVI), and racial and ethnic group percentages. We performed regression analyses, including simple linear regression, partial regression, and multiple regression with interaction terms, to model these relationships. We created census-tract level bivariate choropleth maps of urban areas in California counties. ResultsThe regression models estimate that residents in census tracts with a mean UHII have a 22% increased risk of acute MI and residents in census tracts with the highest UHII have a 112% increased risk of acute MI when compared to residents living in census tracts with the lowest UHII. Additionally, for any given value of UHII, the rate of acute MI was predicted to be higher in census tracts with higher percent people of color. DiscussionThis study highlights the intersection of UHII, CVD incidence, and social vulnerability within urban areas on a census-tract level. It emphasizes the need to implement mitigation strategies to decrease the UHI effect, thereby preventing heat-related CVD events.