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High Humidity Boosts Heart Attack Risk

Study Shows More Elderly Die During Periods of High Humidity, Extreme Heat and Cold

WebMD Health News
Reviewed by Louise Chang, MD

July 12, 2006 -- High humidity may be deadly for elderly at risk for heart attacks.

A new Greek study shows that changes in humidity, as well as temperature, can influence heart attackheart attack death rates among the elderly -- even in relatively mild climates.

Although the relationship between extreme cold and heat and increased heart attacks has been shown in prior studies, researchers say this is the first study to link high humidity to the risk.

Humidity-Heart Link?

In the study, published in the journal Heart, researchers analyzed all heart attack-related deaths reported in Athens during the year 2001, then compared them against daily weather information.

The researchers found sharp seasonal variations in the timing of heart attack deaths, with the proportion of deaths a third higher in winter than in summer. Nearly all of those additional deaths were among people aged 70 and over.

Researchers found that the number of daily heart attack deaths decreased as the average daily temperature increased up to about 74 degrees Fahrenheit. Beyond 74 degrees Fahrenheit, heart attack deaths began to increase along with the temperature.

Short-term cold or heat spells didn’t have as much impact. The study showed average daily temperature over the past week was a much better predictor of heart attack deaths than the average temperature of a single day.

Then, when researchers compared monthly heart attack death rates with weather information, they found that average monthly relative humidity was associated with total heart attack deaths. The number of heart attack deaths increased as average monthly relative humidity rose. In this Athens study, the most humid month was December; the driest was August.

Researchers say the biological link between high monthly humidity and heart attack risk is unclear and requires further research.

But the results suggest vigilant efforts are needed to protect the elderly during periods of extreme temperatures and high humidity.

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