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High Humidity May Be Linked to Heart-Attack Risk

But researchers say the findings are far from definitive

THURSDAY, July 13, 2006 (HealthDay News) -- A Greek study suggests a relationship between high humidity and increased incidence of heart attacks among the elderly, but the finding comes with a lot of "buts" and "maybes" attached.

For one thing, the results don't apply to most of the United States, said study lead author Dr. Georgios Giannopoulos, a research fellow at the University of Athens.

"Athens is a very temperate climate," he said. "It is more like the climate in Florida and parts of California."

The lowest temperature recorded in the year-long study was 34 degrees Fahrenheit, reached on three days in December. The highest temperature, 102 Fahrenheit, was recorded on two days in August.

There were sharp seasonal differences in the number of deaths attributed to heart attacks -- 3.5 times higher in June and seven times higher in December among people over age 70, compared to other age groups, reflecting higher humidity readings, the study found.

The average monthly humidity was the single most important factor associated with heart attack deaths, according to the report in the July issue of the journal Heart.

The finding "should be a concern to physicians," Giannopoulos said. "Measures should be taken to educate older people to avoid excess activity in warm days with humid conditions. They should not be outside without adequate protection."

Dr. Steven Nissen, interim chairman of the department of cardiovascular medicine at the Cleveland Clinic, said it's good advice to tell "anybody who has got a chronic illness to try not to expose themselves to extremes of weather that might cause stress." But, he said, the new study doesn't necessarily prove that high humidity is a major risk factor for heart attacks.

The report study is based on "very raw population data" -- essentially the number of heart-attack deaths reported by hospitals in Athens, Nissen said. But, the lower number of deaths reported in Athens during the high summer months could be "because everyone is out on the island of Cyprus sunning themselves," he said.

The Greek study also lacked the controls of a carefully planned trial, Nissen said. "If we really had strong data that humidity causes heart attacks, everyone would sit up and take notice," he said.

Little research has been done on the effect of weather conditions on cardiovascular disease, Nissen said, but the general impact of high temperatures and high humidity is known.

The American Heart Association recommends that anyone who exercises in such weather should work out in the morning or evening, and be alert for the signs of heat exhaustion and heat stroke.

More information

Detailed advice on avoiding heart trouble in hot weather is offered by the American Heart Association.

SOURCES: Georgios Giannopoulos, M.D., research fellow, University of Athens, Greece; Steven Nissen, M.D., interim chairman of cardiovascular medicine, Cleveland Clinic; July 2006, Heart
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