Almost half of heart attacks are silent; they're still risky

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.

The study's aim was to examine causes of age-related artery damage that can lead to heart disease.

Silent heart attacks were found on EKGs in 317 participants, or about 3 percent, who hadn't had suspicious symptoms.

Silent heart attacks may cause mild fatigue or other vague symptoms that don't seem serious.

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.

Smoking and family history of heart disease were slightly less common among silent heart attack patients but otherwise the groups were pretty similar.