Emergency visits for stroke increase after a heat wave , according to research presented today at ESC Asia, a scientific conference organized by the European Society of Cardiology (ESC), the Asian Pacific Society of Cardiology (APSC) and the ASEAN Federation of Cardiology (AFC).
"Climate change and global warming are global problems, and stroke is one of the leading causes of death," said study author Dr. Ryohei Fujimoto, of Tsuyama Central Hospital and the Department of Epidemiology at the University of Tokyo, Japan. of Medicine, Dentistry and Pharmaceutical Sciences from Okayama University, Japan. 2-4 “Our study indicates that older adults may be more susceptible to stroke after exposure to hot climates. “Preventive measures, such as insulated housing and air conditioning, should be considered a public health priority to protect people from this debilitating and potentially deadly disease.”
There is little information about the effects of high temperatures on stroke risk. This study examined the association between heat exposure and emergency visits for stroke in older adults. The study included 3,367 residents of Okayama, a city in western Japan. Participants were 65 years of age or older and were transported to emergency hospitals between 2012 and 2019 for the onset of a stroke during and several months after the rainy season.
The researchers obtained hourly data on outdoor temperature, relative humidity, barometric pressure, and mean atmospheric concentration of particles less than 2.5 μm in diameter (PM2.5) from the Okayama weather station, managed by the Agency. Meteorology of Japan and the Government of Okayama Prefecture.
The association between temperature and stroke was analyzed during the rainy season, one month later, two months later and three months later. A time-stratified case-crossover study design was used in which for each participant, researchers compared the temperature on the day of the week the stroke occurred (e.g., Monday) with the temperature on the same day. of the stroke-free week (e.g., all remaining Mondays) within the same month. This avoided the potential confounding effects of individual characteristics, long-term temporal trends, seasonality, and day of the week.
The researchers found that the relationship between temperature and stroke was strongest a month after the rainy season. For every 1°C increase in temperature, there was a 35% increased risk of emergency visits for stroke after adjusting for relative humidity, barometric pressure, and PM2.5 concentration. When each type of stroke was analyzed separately, each 1°C increase in temperature was associated with a 24% increase in the likelihood of hemorrhagic stroke , a 36% increase in the risk of ischemic stroke, and a 56% increase in the risk of ischemic stroke. in the risk of transient ischemic attack .
In a second analysis, the researchers evaluated whether there was a possible “effect modification” depending on the rainy season. Effect modification means that the association between the exposure (hot air temperature) and the outcome (emergency visit for stroke) may be different depending on a third variable (during and after the rainy season). For this analysis, the reference period was the rainy season. Again, the relationship was stronger a month after the rainy season. Compared with the baseline period, there was a 31% increase in the probability of stroke for every 1°C temperature increase.
Dr. Fujimoto explained: “The results of the second analysis suggest that environmental conditions immediately after the rainy season intensify the relationship between heat and stroke. "In addition to high temperatures, this period is characterized by an increase in the duration of sunlight and less rain, which may explain the findings."
He concluded: “Our study suggests that older adults should try to stay cool during hot periods, for example by staying indoors during peak temperatures. “Public health systems can help by providing cool spaces for the public to escape the heat during the hottest months of the year.”
