Neighborhood determinants of vulnerability to heat for cardiovascular health: a spatial analysis of Milan, Italy

Climate change can contribute to the increase in the prevalence of cardiovascular (CV) diseases, the leading cause of global deaths. Accordingly, many big cities are interested in increasing their residents’ resilience against heat waves. With these issues in mind, the aim of our study was to identify salient features of urban areas and to analyze the effect of such features on population vulnerability to heat (VtoH) as it relates to CV health. This approach was developed and tested in the city of Milan, Italy, considering the summer periods (May–September) of 2017–2022. Milan was divided into 86 districts and 11 features were considered. K-means was applied for clustering, and both spatial and non-spatial regression were used to study the VtoH, defined as the percentage of CV emergencies on a given heat day and on the day after, compared to the total number of CV emergencies. Socio-urban features were spatially non-stationary and three different clusters of districts were identified. In the whole city, regression analysis depicted a spatial relationship between the focal features and the VtoH, with the model estimating a significant effect in five variables: mean summer temperature, density of drinking water fountains and percentages of elderly, female and graduate residents. Three additional features were found to be significant in only some of the cities’ clusters. Our spatial analysis of CV health emergencies applied to the entire geographical area, rather than at the patient level, represents a relatively underexplored approach in public health-related research. The results of our study and future research taking this approach can inform solutions to equitably protect cities’ residents, which is important in the context of ongoing urbanization and climate change.