CHICAGO (AP) — Almost half of all heart attacks cause no obvious symptoms, yet they can still be life-threatening, according to research on more than 9,000 middle-aged men and women.
It's one of the biggest studies to examine so-called silent heart attacks, and to also explore them across racial and gender groups.
Researchers at Wake Forest University's medical school led the government-funded study. Results were published online Monday in the American Heart Association's journal, Circulation.
Middle-aged adults from four U.S. communities were enrolled: Washington County, Maryland; suburban Minneapolis; Jackson, Mississippi and Forsyth County, North Carolina. The study's aim was to examine causes of age-related artery damage that can lead to heart disease. Whites and blacks were included.
Participants had periodic clinic exams including electrocardiograms and phone interviews with the researchers. They were followed for about 13 years.
Overall, 45 percent of heart attacks were the silent kind, which are usually discovered some point later when a patient has an abnormal EKG reading that suggests previous heart damage.
Silent heart attacks were found on EKGs in 317 participants, or about 3 percent, who hadn't had suspicious symptoms. By contrast, 386 patients, or 4 percent, had full-blown heart attacks with symptoms. Symptoms often include chest pain, jaw and arm pain and shortness of breath. Silent heart attacks may cause mild fatigue or other vague symptoms that don't seem serious.
About 1,830 participants died during the study, 189 of them from heart disease. Those who had silent heart attacks were three times more likely to die from heart-related causes during the study than those without heart attacks. Among participants who had classic heart attacks, these deaths were five times more common than among those without heart attacks.
Both types of heart attacks were most common in men. Classic heart attacks were more common in white men; the rates were about equal in black men.
Among black women, silent heart attacks were more common than classic attacks; among white women the rates were about the same.
Previous studies on the prevalence of silent heart attacks have had varying results ranging from about 20 percent to 60 percent of all heart attacks. The authors of the current research note that many were on smaller, less diverse groups of patients.
Smoking and family history of heart disease were slightly less common among silent heart attack patients but otherwise the groups were pretty similar.
Government data show that each year more than 700,000 Americans have heart attacks and about 120,000 people die from them. Once discovered, the researchers say silent heart attacks should be treated as aggressively as classic ones. That includes getting blood pressure and cholesterol under control, maintaining a healthy weight and getting lots of exercise.
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