Heat exhaustion, domestic heat exposure and socioeconomic disparities among older adults: a cross-sectional mediation analysis from Germany.

Abstract

Background: Older adults are particularly vulnerable to the effects of heatwaves and extreme heat due to physiological changes often exacerbated by chronic diseases and decreased mobility. Although cool indoor temperatures can moderate the health consequences of extreme outdoor heat to some extent, it is important to recognize that access to cool indoor temperatures is distributed unequally across population groups. This study aimed to assess the mediating effect of (indoor) domestic heat exposure on the relationship between socioeconomic position and heat exhaustion in older adults.

Methods: In August 2024, 10,000 participants from the DigiHero cohort were invited to take part in an online survey. Of the 5,026 respondents, persons aged 65 or older were included in the analysis (n = 1,457). Domestic heat exposure was assessed through self-reported indoor temperatures during the day and at night, as well as the availability of cooler rooms at night. Heat exhaustion was measured using self-reported symptoms. Income and education were used as indicators for socioeconomic position. We applied structural equation modelling to assess the total impact of socioeconomic position (education/income) on heat exhaustion and the portion of this effect mediated through domestic heat exposure. Additionally, the analyses were stratified by sex/gender and degree of urbanization.

Results: In the study sample, 54% were female; mean age was 72.8 (SD = 5.1); 50% had a high education level; and 70% were not exposed to domestic heat. Lower income and education were linked to more frequent symptoms of heat exhaustion. Lower income, but not education, was associated with higher domestic heat exposure which mediated the income-heat exhaustion relationship (total effect β = -0.09 (-0.14, -0.03); indirect effect β = -0.01 (-0.02, -0.003)). Sex/gender-stratified analyses showed these associations only among women. Sensitivity analyses indicated a stronger mediation in urban settings.

Conclusion: The analysis revealed that lower income result in more frequent symptoms of heat exhaustion in older women, partially due to differential domestic heat exposure. Potential sex/gender differences in the effects of heat exposure warrant further exploration.