The American Heart Association tells us that heart disease is the number one killer of American women. I think you could change that to include women in other industrialized nations.

Women's Health.gov tells us:

One in three American women dies of heart disease. In 2003, almost twice as many women died of cardiovascular disease (both heart disease and stroke) than from all cancers combined. The older a woman gets, the more likely she is to get heart disease. But women of all ages should be concerned about heart disease. All women should take steps to prevent heart disease.

Added to the usual things that cause heart attacks, like stress, obesity and high blood pressure, research has discovered a new source for worry. Vitabeat tells us:

New research suggests that air pollution can trigger heart disease in older women and increase their chances of death by a stroke; raising questions of whether U.S. environmental standards are strict enough.

Scientists at the Women's Health Initiative tracked 66,000 women between the ages of 50-79, who lived in 36 cities. After considering other risk factors, it was found that air quality was a strong predictor of heart disease and strokes.