Vulnerability factors driving differential patterns in the heat-related mortality between rural and urban areas in Switzerland

Abstract

BACKGROUND AND AIM: Heat-mortality association has shown to be highly variable across geographies suggesting potential disparities in adaptive capacity or vulnerability of populations between and within countries. Understanding these factors can help us clarify potential adaptive mechanisms and help design tailored public health interventions to protect vulnerable populations from climate change. Here we performed a high-resolution nationwide epidemiological assessment to identify spatial patterns in the heat-related vulnerability and assess whether urban and rural districts share similar vulnerability factors. METHODS: We modelled the heat-mortality association using distributed lag non-linear models over daily temperature-mortality series between May-September 1990-2017 in each municipality in Switzerland. We performed a multivariate meta-regression using a wealth of demographic, socioeconomic, topographic, climatic, land use and other environmental data available for each geographic unit. We ran stratified analyses by urban and rural areas and assessed differential patterns through interaction models between urban/rural areas and the various vulnerability factors. RESULTS:In this nationwide analysis, we found slightly larger heat-mortality risks in urban areas(RR=1.37(95%CI:1.28-1.46)) vs rural(1.26(95%CI:1.16-1.36)), defined as the risk at the 99th percentile vs. the temperature of minimum mortality. However, our preliminary findings suggest similar patterns in meta-predictors explaining vulnerability to heat across urban and rural regions(i.e.interaction terms were not statistically significant). Overall, we found larger heat-mortality risks associated with higher levels of PM2.5, percentage of foreign population, proportion of impervious surfaces, average temperature, population density and limited access to health care. CONCLUSIONS:Our preliminary findings suggest that population living in urban areas in Switzerland may be more vulnerable to heat, compared to rural locations, and within each type of region similar vulnerability factors may play a role. This would suggest that (1) there would not be large polarizations in risks and vulnerability factors across regions in Switzerland, and (2) even in rural locations factors associated with more urbanized environment may exacerbate the risks. KEYWORDS: heat, adaptation, mortality, climate change