Most women carry a higher long-term risk of heart disease than they realize, say new American Heart Association guidelines issued today.

The guidelines are more far-reaching than those released in 2004, focusing not on a woman's immediate risk but what is likely to happen as she ages.

"Many women can be at low short-term risk, but in the course of a woman's life, she has a nearly one-in-three chance of dying of heart disease," says Lori Mosca, director of preventive cardiology at New York-Presbyterian Hospital. "It's misguided to think you have a low risk of a condition you have a one-in-three chance of dying of.

"Right now, 30 percent of American women (38 million) are living with heart disease," says Mosca, chairwoman of the heart association's guideline committee. "When you have something that common, it's important we all take action to control our risk."

No one knows precisely why women are less likely to suffer heart attacks or strokes as early in life as men do. Some theorize a young woman's estrogen levels may be protective; others that testosterone is harmful, says Jay Cohen of the University of Minnesota.

Cohen says he welcomes the new guidelines because as many women die of heart disease as men, just at a later age. "Really we should be worried at 30 and 40 not about what's going to happen in the next five years but what's going to happen later on."

The 33-member committee based its recommendations, published in Circulation, on the latest research.

The guidelines attempt to dispel confusion bred by conflicting studies. They also contain some don'ts: