Regional variations in the impacts of high temperature on hospital admissions in Brazil.

Background: High temperatures driven by climate change significantly threaten global health. Their impact on health systems, particularly within low- and middle-income countries, remains underexplored.

Methods: Daily non-elective hospital admissions were collected from the Brazil Hospital Information System for 5,459 (98%) Brazilian municipalities, 2008-2019. Gridded daily maximum temperatures were obtained from the European Centre for Medium-Range Weather Forecasts Reanalysis V5 for the historical period (2008-2023) and projected up to 2060 under three SSP emission scenarios. Population projections were derived from WorldPop. We used a case time-series design and distributed lag non-linear models to examine the relationship between temperature and hospitalisation risk for each state, estimating the number of heat-attributable hospitalisations from 2008 to 2060. Related economic costs were estimated using a cost-of-illness approach including direct and indirect costs.

Findings: Without adaptation, high-temperature-related annual hospitalisations were projected to reach 51 (95 % CI: 19-103), 54 (21-106), and 59 (25-112) per 100,000 population in the 2050s under SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios, respectively, representing 54 %, 62 %, and 78 % increases from the 2010s baseline of 33 (9-67) per 100,000. Annual economic costs were projected to reach $228-$264 million in the 2050s, with higher absolute costs in the South and faster relative increases in the North.

Interpretation: The substantial impact of heat on hospitalisations, and its associated costs to the health sector and wider economy, worsen under future climate and demographic change. Regional adaptation and targeted healthcare investments are crucial to manage rising health burdens.

Funding: UK Research and Innovation; China Scholarship Council.