Study suggests stroke hospitalizations and death rates tied to changes in temperature and humidity
Imagine hearing a weather forecaster warn that tomorrow could be "colder with a chance of stroke."
As odd as that may seem, researchers have found possible associations between certain weather conditions and the incidence of strokes.
Larger daily temperature variations and higher humidity each were associated with higher stroke hospitalization rates, according to a new study.
The researchers also found that colder average annual temperatures were associated with stroke hospitalizations and death. An average daily temperature change of 5 degrees Fahrenheit was associated with about a 6 percent increase in stroke risk and hospitalization, the researchers said.
The reasons behind the findings are unclear, said study lead author Judith Lichtman. And although the study showed an association between weather and stroke risk, it didn't prove a cause-and-effect relationship.
"Daily fluctuations in temperature and increased humidity may actually be stressors," said Lichtman, an associate professor of epidemiology at the Yale School of Public Health. "People at risk for stroke may want to avoid being exposed to significant temperature changes and high humidity."
How might fluctuating temperatures actually stress the body? When temperatures go down, blood vessels in the skin constrict so the body doesn't waste a lot of heat, said Dr. Mark Stecker, chairman of the department of neurosciences at Winthrop-University Hospital in Mineola, N.Y. When it's warm outside, the vessels open up to increase heat loss through the skin.
Stecker, who was not part of the research team, said the idea that weather can affect health is not new. "People think there should be a relationship," he said. "They often say things like, 'My joints hurt -- maybe it's going to rain,' or, 'I got a cold because it's cold outside.'"
There might be something to old wives' tales, he said, but it's extremely difficult to know for sure.
The study, which is scheduled for presentation Wednesday at the American Stroke Association meeting in San Diego, should be considered preliminary until published in a peer-reviewed journal.
For the research, Lichtman and her team used 2009-10 statistics from a national database on hospital inpatients, noting ischemic stroke hospitalizations of people 18 years old or older. Ischemic strokes happen as a result of an obstruction within a blood vessel supplying blood to the brain. The new study included data from nearly 135,000 patients.
Temperature and dew point were pulled from the U.S. National Climatic Data Center and linked to stroke discharges at the county level. Factors such as region, season, age, gender, race and patient health issues (such as diabetes and high blood pressure) were considered in the analysis of the data.
This study isn't the first to suggest a relationship between weather and stroke risk, Lichtman said. She said other studies done in Europe and Japan have shown seasonal associations for weather and stroke.
Lichtman suggested that people at risk of stroke who are living in a region with extreme weather fluctuations might want to minimize their exposure to the extremes. That might be as simple as staying indoors with air conditioning on a hot day or ensuring ample heating when it's especially cold outside, she said.
Fluctuating or extreme weather conditions should also raise alertness for the signs and symptoms of stroke, Lichtman said.
For his part, Stecker said the research will have a minimal impact on managing stroke risk.
"I'd tell a patient to not even think about it. People have enough anxiety already," he said. It's more important to focus on other risks, such as diet, weight, blood pressure, exercise and whether they take a statin to treat high cholesterol, he said.
Lichtman said she wants to do more research to better understand whether there is a more defined cause-and-effect relationship between weather and stroke risk, and explore the cause in more depth. "Understanding the reasons for the associations between weather conditions and stroke could lead to the development of targeted preventive interventions," she said.
Lichtman, who is married to a musician, said she knows firsthand how weather can affect us. "My husband's violin responds to extreme weather temperatures and humidity all the time," she said.
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