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The incidence of one type of heart attack has steadily decreased in the US since 1996, regardless of gender or ethnicity, to the lowest rates in years, according to a new study.

In recent years, mortality in patients with the type of heart attack, known as acute ST-elevation myocardial infarction, has decreased substantially in developed countries, Dr. Mohammad Reza Movahed, of the University of Arizona Sarver Heart Center, Tucson, and colleagues write in their study.

Acute ST-elevation myocardial infarctions, which afflict about half a million in the U.S. each year, result from prolonged blockage of one of the arteries that supply blood to the heart. The decline may be due to treatments as well as prevention of risk factors such as high cholesterol, according to the authors.

The team reports in the American Journal of Cardiology that they studied more than 1.3 million patients, at least 40 years of age, who were diagnosed with such heart attacks between 1988 to 2004. The patients' average age was 66 years.

Almost twice as many men were diagnosed than women (62 percent versus 38 percent, respectively).

Beginning in 1996, the rate of the heart attacks decreased steadily, until it was 50 per 100,000 per year, just half the rate it was in 2004.