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 hospitalisation rates, according to a new study.
The researchers also found that colder average annual temperatures were associated
with stroke hospitalisations and death. An average daily temperature change of 15
degrees Celsius was associated with about a 6% increase in stroke risk and
hospitalisation, 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, NY 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 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 hospitalisations
of people 18 years old or older. Ischaemic 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 US National Climatic Data Centre
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.
Minimising exposure to extremes
Lichtman suggested that people at risk of stroke who are living in a region
with extreme weather fluctuations might want to minimise 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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