Research has also shown that people with one particular estrogen gene variant are three times more likely to have a heart attack than those without the variant. Both men and women have the gene, but only a small number have the variant that increases heart attack risk.

Finally, researchers have identified a gene mutation that causes heart attacks. While the mutation was discovered in only one family, and is unlikely to be found in others, the finding provides new insight into the genetic component of heart disease.

Does race play a role in heart attacks?

Yes. African-Americans have greater rates of heart disease and heart attack than do white Americans. The reasons for this are currently being explored in the Jackson Heart Study, which was launched in 2000. Sponsored by the National Institutes of Health, it is modeled after the famed Framingham Heart Study. More than 6,000 black American men and women ages 35 to 84, in Jackson, Mississippi, are being studied. A combination of physical examinations and questionnaires are being used to establish risk factors for cardiovascular disease in black Americans.

Is menstruation a factor in heart attacks?

Possibly. Recent studies have explored whether a woman's menstrual cycle plays a role in heart attack risk. One found a higher risk of heart attack at the onset of the menstrual cycle, when estrogen and progesterone levels are at their lowest. Researchers are unsure of the reason but stress that the increase in risk is very low.