The burden of health issues caused by high temperatures is a major public health issue that is projected to increase as global temperatures rise. Heatwaves, generally defined as more than two days of abnormally high temperatures, are becoming more frequent and their health effects are becoming better understood.
Until recently, however, the association between heatwaves and ischaemic stroke (IS) had not been well investigated. IS occurs when blood flow to the brain is interrupted and accounts for more than 60% of all new strokes. In a new study by Yin and colleagues published in Nature Scientific Reports in January 2025, the association between heatwaves and IS in Hunan province, China was explored.
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Using meteorological and hospital admissions data, Yin and colleagues analysed associations between heatwaves and more than 329,000 IS hospital admissions. They found a strong association between heatwaves, defined as at least three days with a maximum temperature of 35°C (95°F), and increased risk of hospitalisation for IS. Those aged 60 and older experienced the effects of heatwaves more rapidly, with a lag of only one day between the start of a heatwave and peak IS hospitalisation risk, as well as stronger effects, with a 20% higher risk of IS hospitalisation than during non-heatwave periods. The younger age group had a slower reaction to heatwaves, with a lag of six days to the highest IS hospitalisation risk, and less dramatic effects, with only a 7% higher risk of IS hospitalisation than during non-heatwave periods.
In general, men were found to have a higher risk of IS due to heatwaves and a faster response, with a lag of only one day between the start of the heatwave and the highest IS hospitalisation risk, which was 30% higher than during non-heatwave periods. Women had a delayed response to heatwaves, with a peak IS hospitalization risk on day five and only 5% higher than during non-heatwave periods. This study highlights both the increased risk of hospitalisation for IS during and following heatwaves, and the differential effects across age groups and sexes.
This increased risk of IS during heatwaves aligns with GlobalData epidemiologists’ broader forecasting about the indication. Diagnosed incident cases of acute ischaemic stroke (AIS) are forecast to increase from 1,735,000 cases to 2,779,000 cases at an annual growth rate of 5% between 2017 and 2027 in China. For older men, the group at highest risk for heatwave-associated IS identified by Yin and colleagues, diagnosed incident cases of AIS are forecast to increase between 2% and 10% across different age groups.
China leads the eight major pharmaceutical markets (8MM: urban China, France, Germany, Italy, Japan, Spain, the UK and the US) in the diagnosed incidence of AIS and makes up approximately 70% of all diagnosed incident cases across the 8MM.
As heatwaves become more common, a focus on the prevention of IS must be included in management plans. Access to cool spaces and messaging around avoiding physical exertion during the hottest parts of the day will be critical in reaching those at the highest risk of IS, especially older adults and men.
