Projected compound effects of population aging and climate warming on emergency ambulance demand in Japan

The emergency medical services system, including emergency ambulance dispatch (EAD), faces significant challenges due to a rapidly aging population and climate change. Notably, despite the warming climate, it remains unclear whether the high EAD incidence in winter will persist. This study projects the compound impact of these factors on future seasonal demands of EAD in Japan.

We analyzed 26,595,933 all-cause EAD cases among older adults in Japan in 2011-2019 and projected EAD incidence in 2011-99 under climate-population scenarios. We compared EAD incidence and its seasonality between 2011 and 2019 and future decades. Peak-to-trough ratio (PTR) and attributable fraction (AF) were used to measure the amplitude and burden of seasonality.

Until mid-century, annual incidence cases are projected to rise by 15 %, followed by a decline afterwards. The annual incidence rate is expected to increase by 2.95 % to 4.25 % by the 2090s under various scenarios. Importantly, the high-incidence peak is projected to shift from cold to warm season, while high incidence in cold season persists. PTR and AF are projected to increase, with more profound changes under extreme climate scenario.

Demand for emergency medical services among older adults is expected to rise, especially until mid-century, with high demand in both summer and winter. Adaptive strategies are needed to manage increasing emergency service demands and shifts in seasonal patterns.