American Heart Association meeting report:
DALLAS, Nov. 9 -- People with heart disease may want to pay closer attention to weather reports, especially if below-normal temperatures or extreme atmospheric pressures are in the forecast. A study presented today at the American Heart Association's 71st Scientific Sessions suggests that changes in temperature and atmospheric pressure may be related to an increased risk of heart attack in men. Researchers examined the relationship between weather conditions and heart attacks -- both fatal and nonfatal -- among 250,000 men ages 25 to 64 living in and around Lille, France.
Philippe Amouyel, M.D., Ph.D., professor of epidemiology at Lille University School of Medicine in France, reports that an 18° F (10° C) decrease in the temperature average for a particular date increased the risk of a first heart attack that day by 13 percent.
Amouyel says the study results reflect similar trends in heart attack risk for women, but to a lesser extent because of the much lower risk for heart attack observed in general for women than for men in these age classes.
The French team noted a possible relationship between atmospheric pressure and heart attacks. Extremes of pressure were associated with increased risk of heart attack regardless of whether the change in pressure was higher or lower. This trend is called a "V-shaped" relationship, meaning that if the effects of atmospheric pressure were drawn on a graph, the resulting series of points would form the shape of a "V."
"The description of the effect of atmospheric pressure extremes is new," says Amouyel. "The lowest risk was 1,016 millibars -- the standard atmospheric pressure at sea level," Amouyel says. The millibar is the international unit for measuring atmospheric pressure.
"When atmospheric pressure rose by 10 millibars above sea level [the right side of the "V"], there was an 11 percent increase of heart attack rates, and when pressure dropped by 10 millibars [left side of the "V"], there was a 12 percent increase," he says. "The V-like relationship was observed for fatal, nonfatal and recurrent heart attacks and for all ages."
The risk of heart attack was significantly greater for people who had suffered a previous heart attack. When atmospheric pressure dropped 10 millibars below the 1,016 figure, for example, the risk of a recurrent heart attack rose 30 percent. Similarly, an 18° F (10° C) drop in temperature was associated with a 38 percent increased risk of recurrent heart attack, which is about three times higher than a person's risk of having a first attack.
The study was not designed to determine the reason that changes in temperature and atmospheric pressure might affect the risk of heart attack. Previous studies have linked cold weather with higher blood pressure, elevations of certain fats in the blood and fibrinogen, a protein involved in blood clotting.
These conditions might make a heart attack more likely, he says. A heart attack occurs when blood flow to the heart is blocked by clots or fatty plaque deposits in blood vessels.
Previous studies have linked changes in atmospheric pressure to an increase in the likelihood of a hemorrhagic stroke, one that is caused by bleeding in the brain, says Amouyel. "The usual explanation reported is a variation of blood pressure that could be tied to atmospheric pressure variations," he says. "This is the first study to report an effect of atmospheric changes on the occurrence of heart attacks in the general population, and not just deaths from heart disease," Amouyel says.
Amouyel and his colleagues analyzed 10 years of data from the World Health Organization's Monitoring of Trends and Determinants in Cardiovascular Disease study. Called the MONICA Project, this international study focuses on trends, risk factors and treatments for heart disease and stroke.
The findings suggest that at least with regard to temperature, some preventive measures might reduce the risk of heart attack when temperatures turn unusually cold. For instance, bundling up for winter weather and improving heat insulation in homes may be helpful, he says.
First, however, "these observations have to be confirmed and new studies designed to analyze the variations of common heart disease and stroke risks with temperature and atmospheric pressure," Amouyel says.
As part of the MONICA project, researchers had tracked the precise date and time of all heart attacks in the Lille area through hospital records, physician contacts and death certificates from 1985 through 1994.
Among the 250,000 men studied, 2,524 suffered 3,314 heart attacks during the decade studied. A total of 1,281 died of heart attacks with 700 men having at least one recurrent heart attack.
In general, the risk of heart attack increased as the temperature dropped below the average for the day and decreased as temperatures rose above normal. However, Amouyel notes that the Lille area has a moderate climate, with the annual temperature averaging between 5° and 82° F (minus 15° and 28° C). Other studies have shown an increased risk of heart attack with much higher temperatures. "We did not have temperatures high enough to detect that," he says.
Co-authors of the paper are Sandrine Danet, M.D.; Florence Richard, M.D.; Michele Montaye, M.D.; Stephanette Beauchant, M.D.; Brigitte Lemaire, M.D.; Catherine Graux, M.D.; Dominique Cottel, M.D.; Chantal Steclebout, R.T.; and Nadine Marecaux, R.D.
For more information Nov. 8-11
4:30 p.m. CT, Monday contact Carole Bullock or Brian Henry
November 9, 1998 Dallas County Convention Center.