The Direct and Indirect Influences of Interrelated Regional-Level Sociodemographic Factors on Heat-Attributable Mortality in Europe: Insights for Adaptation Strategies

Abstract

Background: Heat is a significant cause of mortality, but impact patterns are heterogenous. Previous studies assessing such heterogeneity focused exclusively on risk rather than heat-attributable mortality burdens and assume predictors are independent.

Objectives: We assessed how four interrelated regional-level sociodemographic predictors-education, life expectancy, the ratio of older to younger people (aging index), and relative income-influence heterogeneity in heat-attributable mortality burdens in Europe and then derived insights into adaptation strategies.

Methods: We extracted four outcomes from a temperature-mortality study covering 16 European countries: the rate of increase in mortality risk at moderate and extreme temperatures (moderate and extreme slope, respectively), the minimum mortality temperature percentile (MMTP), and the underlying mortality rate. We used structural equation modeling with country-level random effects to quantify the direct and indirect influences of the predictors on the outcomes.

Results: Higher levels of education were directly associated with lower heat-related mortality at moderate and extreme temperatures via lower slopes and higher MMTPs. A one standard deviation increase in education was associated with a $-0.46\pm 0.14$, $-0.41\pm 0.12$, and $0.41\pm 0.12$ standard deviation ($\pm \text{standard error}$) change in the moderate slope, extreme slope, and MMTP, respectively. However, education had mixed indirect influences via associations with life expectancy, the aging index, and relative income. Higher life expectancy had mixed relations with heat-related mortality, being associated with higher risk at moderate temperatures ($0.33\pm 0.11$ for the moderate slope; $-0.19\pm 0.097$ for the MMTP) but lower underlying mortality rates ($-0.72\pm 0.097$). A higher aging index was associated with higher burdens through higher risk at extreme temperatures ($0.13\pm 0.072$ for the extreme slope) and higher underlying mortality rates ($0.93\pm 0.055$). Relative income had relatively small, mixed influences.

Discussion: Our novel approach provided insights into actions for reducing the health impacts of heat. First, the results show the interrelations between possible vulnerability-generating mechanisms and suggest future research directions. Second, the findings point to the need for a dual approach to adaptation, with actions that explicitly target heat exposure reduction and actions focused explicitly on the root causes of vulnerability. For the latter, the climate crisis may be leveraged to accelerate ongoing general public health programs. https://doi.org/10.1289/EHP11766.