The study examined Medicare, Medicaid, and private insurance data from hospitals across the United States. The researchers looked at 157,130 hospital discharges in 2010-2011 for ischemic stroke (caused by a blood clot that blocks blood flow in or leading to the brain). The researchers also obtained temperature and dew point data during the same period and localized it to the county level.
They found that each 5-degree Fahrenheit change in daily temperature was associated with a 6% increased risk of stroke hospitalization. Meanwhile, each 5-degree Fahrenheit increase in the dew point was associated with a 2% increase in stroke hospitalization. The associations were present even during the coldest period of the year.
"Weather is not something people typically associate with stroke risk; however, we've found weather conditions are among the multiple factors that are associated with stroke hospitalizations," said Judith Lichtman, first author and an associate professor of epidemiology at the Yale School of Public Health.
These fluctuations in daily temperature and average dew point were associated with increased odds of being hospitalized for a stroke, but not with dying in the hospital.
"This study suggests that meteorological factors such as daily fluctuations in temperature and increased humidity may be stressors that increase stroke risk," Lichtman said. "People at risk for stroke may want to avoid being exposed to significant temperature changes and high dew point and, as always, be prepared to act quickly if they or someone they know experiences stroke signs and symptoms."
More research is needed to better understand the physiological changes that occur with changes in temperature and humidity, said Lichtman.
Erica C. Leifheit-Limson of the Yale School of Public Health, and Larry Goldstein of Duke University are co-authors of the study.
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