Ambient heat exposure after the rainy season is associated with an increased risk of Stroke

Abstract Funding Acknowledgements Type of funding sources: None. Background Stroke is a major global health issue and Climate change is the biggest and most urgent challenges. The Asia and Pacific region have been more vulnerable to climate change and extreme heat exposure than other regions of the world. Despite the growing concern for heat waves, few studies have investigated heat exposure and the risk of Stroke in the elderly considering effect of Asian meteorological factors. Purpose We aimed to examine the association between heat exposure and the risk of Stroke in the elderly and to evaluate possible effect-measure modifications by the rainy season, which is a characteristic climatic occurrence in East Asia. Methods Our study was designed as a time-stratified case-crossover. The study included 3367 residents in the city, Japan, aged 65 years or older who were dispatched to emergency hospitals between 2012 and 2019 for the onset of Stroke during and a few months after the rainy seasons (Picture 1). We examined the association between temperature and Stroke onset during and a few months after the rainy seasons with conditional logistic analysis adjusted for relative humidity, barometric pressure, and particulate matter less than 2.5 µm in diameter (pm 2.5). Furthermore, we examined analyses on effect-measure modification where is the exposure of a 1°C increase in temperature and potential effect modifier as stratified during and after the rainy seasons. Results Heat exposure during one month after the rainy season was associated with Stroke risk; the adjusted odds ratio (OR) for a 1°C increase in temperature was 1.34 (95% confidence interval [CI]: 1.29-1.39). In stratified type of the stroke, Hemorrhagic stroke (OR: 1.37, 95% CI: 1.24-1.51), Ischemic stroke (OR: 1.37, 95% CI: 1.24-1.53), and Transient ischemic attack (OR: 1.43, 95%CI: 1.23-1.68) were significantly associated with heat exposure during one month after the rainy season respectively (Picture 2). In the results of analyses on effect modification, one month after the rainy season group was highest than other groups when reference was during the rainy seasons (OR: 1.34, 95% CI: 1.3-1.39, P<0.001 [Measure of effect modification on additive scale]). Conclusions The present study suggests that heat exposure increases the risk of Stroke onset during the month after the end of the rainy season in the elderly. We propose that public health measures, such as maintenance designed high-insulated housing and improved air conditioning control, be implemented in the Asia and Pacific region to address heat exposure during one month after the rainy season, which can affect the incidence of stroke in the elderly.