Heat stroke? Try cold stroke

I get pretty tired of those local news stories about how we should be afraid of the weather here in the temperate zone. Killer cold! Killer heat! Killer pollen! Whatever you do, don't go outside and enjoy nature!

Well, let's hope my smartypants are well-insulated, because new Yale research shows that when the mercury drops, hospitalizations for strokes increase.

Using Medicare, Medicaid, and private insurance data, School of Public Health researchers looked at more than 100,000 stroke hospitalizations nationwide. Then they compared those figures to local temperature and humidity data. For every 5-degree Fahrenheit drop in average daily temperature, they found, stroke risk increased by 4.3 percent.

Global warming to the rescue? Think again. Temperature fluctuations seem to matter even more than absolute temperature: every 5-degree daily change was associated with a 6 percent increase in stroke risk, a Yale News release says.

And then there's humidity. Even during cold weather, each 5-degree increase in the dew point—indicating moister air—was associated with a 2 percent increase in stroke hospitalizations.

‘‘Maybe some of these meteorological factors serve as a trigger’’ for strokes, lead researcher Judith Lichtman ’88MPH, ’96PhD, tells the Associated Press. As climate change produces the extreme weather that some call "global weirding," daily weather effects on stroke risks "could be increasingly important," she says.

The AP lists some possible explanations for a weather-stroke connection. Cold makes blood vessels constrict, raising blood pressure. It also causes cardiovascular stress, making the heart work harder and blood more susceptible to clotting. And high humidity can cause dehydration, thickening the blood.

Lichtman, an associate professor of epidemiology at the School of Public Health, and coauthors presented their findings Wednesday at an American Stroke Association conference—in San Diego, with a high temperature 69 degrees Fahrenheit and a low of 53.

Keep warm.

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The Yale Alumni Magazine is published by Yale Alumni Publications Inc., an alumni-based nonprofit that is not run by Yale University. Its content does not necessarily reflect the views of the university administration.