Stroke and climate change: A World Stroke Organization scientific statement

Climate change poses an escalating threat to global brain health and is increasingly linked to stroke incidence, outcomes, and inequities in prevention and treatment. This World Stroke Organization scientific statement summarizes current evidence on the associations between stroke and the environmental variables exacerbated by climate change, with a focus on risk and outcomes.

We systematically identified and reviewed published studies assessing associations between stroke and environmental variables, including extreme temperatures, temperature variability, humidity, barometric pressure, wildfires, dust and sandstorms, and compound weather events. Air pollution, unrelated to wildfire exposure, was excluded, as a subsequent statement will focus on this. Paired reviewers screened titles and abstracts. Full texts were evaluated for study design, sample size, geographic context, and strength of evidence, with attention to impacts on vulnerable populations where data were available. Study type, exposure assignment, and strength of evidence were further confirmed by a team member with Master's level qualification in epidemiology.

Most of the included studies were based on ecological designs. Cold exposure, temperature variability, and extreme thermal events were most consistently associated with increased stroke risk. Although cold effects were generally stronger than heat effects, heat effects have been increasing over time. Increased stroke incidence was also associated with low or varying barometric pressure, rapid humidity shifts, and exposure to wildfire smoke, dust, and sandstorms, particularly among older adults and those in low- and middle-income countries. Compound weather events, such as concurrent heat and humidity extremes, showed additive or synergistic effects on stroke incidence and mortality. Despite heterogeneity in definitions and methods and most evidence supporting associations rather than proving causation, the overall direction of evidence across exposures was positive, coherent, and biologically plausible.

Advancing mitigation efforts that reduce greenhouse gas emissions is essential, since limiting further climate change directly decreases the environmental drivers of stroke risk and protects long-term population brain health, along with broader climate-related health risks. Stroke professionals and organizations can meaningfully contribute through local, regional, and global advocacy. Climate-related environmental variables already meaningfully increase stroke risk and exacerbate existing health inequities. To further counter these trends, stroke prevention and care systems should integrate climate risk awareness, patient education, and early-warning mechanisms into clinical practice and health system planning. Priority areas include targeted protection for vulnerable groups, standardized exposure metrics, longitudinal surveillance, systematized education on climate change's impact on brain health, and expansion of research in underrepresented regions. Strengthening global collaboration and embedding climate resilience into stroke systems of care are critical for reducing both stroke-related morbidity and the wider health impacts of a climate-impacted world. This scientific statement has been reviewed and approved by the WSO Executive.