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

CHICAGO (AP) - A new study found almost half of all heart attacks cause no obvious symptoms, yet they can still be life-threatening.

The research followed more than 9,000 middle-aged men and women for almost 13 years. It's one of the biggest studies to examine so-called silent heart attacks, and to explore them across racial and gender groups.

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