Projected compound effects of population aging and climate warming on emergency ambulance demand in Japan
Research led by Associate Professor Lina Madaniyazi of the School of Tropical Medicine and Global Health, Nagasaki University, in collaboration with the University of Tokyo and the National Institute for Environmental Studies, has carried out Japan’s first integrated projection of how population aging and climate warming will together impact the emergency medical services demands.
Japan faces two converging challenges: rapid population aging and climate change. Older adults are particularly vulnerable to heat, and heat-related conditions such as heatstroke are already on the rise. These factors are driving an increase in emergency medical service use, especially in densely populated areas.
By combining demographic and climate projections, this study projects the future demand for emergency ambulance dispatches among older adults in Japan through the end of the 21st century (up to 2099). The results suggest that administrative agencies—including fire departments—should begin preparing for a changing landscape of demand.
Three strategic priorities emerge:
1. Plan for mid-century demand surges by expanding emergency medical service capacity—personnel, vehicles, training, and infrastructure—to meet the needs of a growing elderly population.
2. Adapt resource allocation seasonally, recognizing that emergency calls may remain high in winter but will increasingly rise during hot summer months.
3. Integrate climate and demographic risks into long-term emergency medical service strategies, rather than treating them separately.
The authors emphasize that these are scenario-based simulations, not fixed forecasts. Still, they provide valuable insights to guide risk-informed and proactive planning in a society that is both aging and warming.
This study was supported by the Environmental Research and Technology Development Fund of the Environmental Restoration and Conservation Agency, provided by the Ministry of the Environment of Japan (Project No. 1-2307, JPMEERF20231007).
Projected annual all-cause emergency ambulance dispatch incidence among older adults (≥65 years) from 2011 to 2099 in Japan. Panel (a) and panel (b) show the results for annual cases (×100,000 people) and annual incidence rate (per 100,000 people), respectively.
Relative changes (%) in all-cause emergency ambulance dispatches (cases and incidence rates) among older adults (≥65 years) across prefectures in the 2050s and 2090s relative to the reference period (2011-2019) under SSP2-4.5 climate change scenario & SSP2 population scenario.
Panels (a), (b), and (c) show the relative change in incidence cases in the 2050s and 2090s. Panels (d), (e), and (f) show the relative change in incidence rate in the 2050s and 2090s. The prefecture in bar plots (panels (c) and (f)) are ordered according to latitude, with Hokkaido in the north and Okinawa in the south.
Seasonality of all-cause emergency ambulance dispatch among older adults (≥65 years) in Japan from the 2011-19 to 2090s. The grey line represents seasonality from 2011 to 19, and the sequential colors represent seasonality from the 2020s to the 2090s. The two grey vertical lines split the entire season (Jan 1st to Dec 31st) to warm season (May 1st to Oct 30th) and cold season (Jan 1st to Apr 30th and Nov 1st to Dec 31st).
Background
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.
Methods
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.
Results
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.
Conclusion
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.
Keywords: Emergency ambulance; dispatch; Aging; Climate change; Seasonality
Journal: Environment International
Title: Projected compound effects of population aging and climate warming on emergency ambulance demand in Japan
Authors:
Lina Madaniyazi
School of Tropical Medicine and Global Health, Nagasaki University
Kazutaka Oka
Center for Climate Change Adaptation, National Institute for Environmental Studies
Yasushi Honda
Center for Climate Change Adaptation, National Institute for Environmental Studies
Masahiro Hashizume
School of Tropical Medicine and Global Health, Nagasaki University
Department of Global Health Policy, Graduate School of Medicine, The University of Tokyo
Corresponding Author:
Lina Madaniyazi
DOI: https://doi.org/10.1016/j.envint.2025.109619
For more details, please see the full article in the Environment International.
