Impact of Cumulative Exposure to Extreme Heat – Intergenerational Inequities of Health Burden in Japan

At the UTCCS Annual Workshop 2025, I presented a poster on my doctoral research exploring the largely unexplored long-term mortality effects of cumulative heat exposure in Japan.

Poster Overview

• Background & Rationale
  • Climate change has led to increasingly frequent and intense heatwaves, raising the risk of heat-related mortality.
  • While short-term mortality associations with extreme heat are well established, the long-term effects of cumulative lifetime exposure remain under-investigated:contentReference[oaicite:1]{index=1}.
• Aims & Objectives
  1. Investigate the long-term effects of cumulative exposure to extreme heat on mortality risks and Years of Life Lost (YLL).
  2. Assess intergenerational disparities in health burdens to inform targeted climate adaptation strategies.
• Methods
  • Synthetic cohort of 49.75 million death records (1972–2022) linked with long-term meteorological data (1875–2022).
  • Extreme heat days defined by the 95th percentile threshold (1880–1950 baseline) per prefecture.
  • YLL calculated using Japanese life tables (MHLW) and assigned exposure histories across individual lifespans.
• Key Findings
  • Extreme heat days have risen sharply in recent decades across all prefectures.
  • YLL increases with age and is higher among older birth cohorts due to cumulative exposure.
  • Intergenerational differences suggest varying vulnerability to lifetime heat exposure, highlighting potential inequities in health burden.
• Discussion & Implications
  • The study demonstrates the growing burden of heat-related YLL in Japan and highlights the importance of incorporating a life-course and generational perspective in climate–health research.
  • Findings provide evidence to guide future climate adaptation and health equity strategies.

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