Population aging exacerbates heat stroke-related ambulance transportations in Japan

Rapid aging significantly increases Japan's population vulnerability to severe heat stress, yet the precise impact on heat stroke-related morbidity remains unclear. This study integrates multiple datasets and develops predictive models for daily heat stroke-related emergency ambulance dispatches (HT-EADs) among younger and older populations in Japan for 2010-2019. By adjusting the proportion of older adults and incorporating pseudo climate warming, we assessed how aging and warming could amplify total HT-EADs. Compared to the simulation using demographic conditions of 1995, recent aging trends have led to a 15% increase in total HT-EADs in Japan during 2010-2019, an effect equivalent to a 0.3℃ warming. This increase could rise to 30% under a super-aging demographic scenario by 2045, surpassing the impact of a 0.5℃ warming. Our findings emphasize that aging has comparable negative impacts on heat stroke morbidity as climate change, highlighting the urgent need of enhanced protections for older residents during hot summers.