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Background: Rising temperatures and frequent heatwaves lead to substantial health burden, particularly among older adults. Simultaneously, various heat adaptation strategies are in development, but empirical studies are lacking and limited to evaluate long-term effects.

Aim/scientific question: What is the long-term effectiveness of a range of fictional heat adaptation strategies for older adults as of age 65?

Material & Methods: We developed a decision-analytic Markov state transition model capturing hospitalizations as well as heat- and non-heat related mortality. National model input parameters include temperature-mortality exposure-response curves (ERCs), temperature data, hospitalization data, and mortality data. We assumed effects of fictional adaptation strategies by changing temperature-mortality ERCs. These changes were realized by defining the temperature threshold for activation of an adaptation strategy (25, 26, 27, 28, 29°C), and the relative reduction of the curve (0.95, 0.90, 0.85, 0.80, 0.70). Outcomes include heat-related deaths (HRD) and life-years gained (LYG) per 10,000 people aged 65. Analyses were conducted over a lifetime horizon. Sensitivity analyses were performed to assess robustness.

Results: Model validation included comparing observed remaining life expectancy at age 65 (20.192 years) with the modeled value (20.190 years). Based on preliminary results, evaluated strategies prevented 2 to 27 HRD/10,000 people aged 65 and produced 9 to 214 LYG/10,000 people aged 65.

Discussion: This modeling study provides the first systematic long-term evaluation of fictional heat adaptation strategies with a range of assumed effects in older adults. By exploring this spectrum of potential long‑term outcomes, future heat adaptation strategies–once their effects have been empirically evaluated–can be positioned within this range, enabling an informed estimation of their long‑term impact. The findings support evidence-informed decisions on the implementation of interventions.

Take Home Message: Heat adaptation measures can reduce heat-related deaths. Long-term effectiveness evaluation supports health systems in prioritizing strategies.

Competing interests: The authors declare no conflicts of interest. This work was partially funded by the European Union’s Horizon Europe research and innovation program under Grant Agreement No. 101057131, Climate Action To Advance HeaLthY Societies in Europe (CATALYSE).