Influences of area-level sociodemographic factors on heat-related mortality in Europe: insights to guide adaptation strategies

Abstract

BackgroundEurope is the world region most affected by heat-attributable mortality, but impact patterns are heterogenous. We aimed to assess the contributions to this heterogeneity of four area-level predictors (education, life expectancy, the ratio of older to younger people [ageing index], and relative income) to identify general adaptation strategies. MethodsWe extracted four outcomes from a heat-mortality study covering 147 areas in 16 European countries: the rate of increase in risk at (1) moderate and (2) extreme temperatures, (3) the minimum mortality percentile, and (4) the underlying mortality rate. We used structural equation modelling to quantify the direct and indirect associations between the predictors and outcomes, accounting for country-level random effects. FindingsHigher levels of education (compared with lower levels) were directly associated with lower heat-related mortality burdens via reduced risk at moderate and extreme temperatures, and lower underlying mortality rates. However, it had ambiguous indirect associations with heat-related mortality burden through positive associations with life expectancy, ageing index, and relative income. Higher life expectancy (compared with lower life expectancy) had contradictory relations with the mortality burden, being associated with higher risk at moderate temperatures but lower underlying mortality rates. A higher ageing index (compared with a lower index) was associated with higher burdens through higher risk at extreme temperatures and higher underlying mortality rates. Relative income made a small and ambiguous contribution. The relative magnitudes of the county-level random effects suggested innate human physiology had a major role in risk at extreme temperatures but that addressing modifiable sociomaterial conditions might reduce the burden via influence on risk at moderate temperatures and the underlying mortality burden. InterpretationOur findings support three general adaptation strategies, showing the need for both general social transformation and focused climate-specific interventions: (1) general social strategies to improve health and reduce underlying mortality, (2) targeted social interventions to address factors instilling patterns of vulnerability at moderate temperatures, and (3) specific actions during extreme temperatures. FundingThe EU's Horizon 2020 research and innovation programme (grant agreement 865564 European Research Council Consolidator Grant EARLY-ADAPT).