Researchers say they have developed a simple test that can tell if a person with heart disease is likely to suffer a heart attack. The test measures levels of a protein in the blood. The researchers say people with high levels of this protein are at high risk of heart attack, heart failure or stroke.

Kirsten Bibbins-Domingo of the University of California in San Francisco led the team. For about four years, they studied almost one thousand patients with heart disease.

The researchers tested the heart disease patients for a protein called NT-proBNP. Patients with the highest levels were nearly eight times more likely than those with the lowest levels to have a heart attack, heart failure or stroke.

The researchers say the presence of high levels of the protein in the blood shows that the heart muscle is under pressure in some way. The study involved mostly men, so the researchers could not say for sure that the results are also true for women.

They say the patients with the highest levels of NT-proBNP were older and had other problems like diabetes or high blood pressure.

Other researchers say more studies are needed to confirm if knowing the protein levels of a heart patient should affect that person's treatment. They also would like to know if more aggressive treatment could reduce the patient's chance of a heart attack or stroke.

The study appeared in the Journal of the American Medical Association.

Could a little sleep during the middle of the day reduce the risk of a heart attack? An unrelated study earlier this month in the Archives of Internal Medicine suggests that the answer may be yes.

In countries like the United States, afternoon naps are mostly for children. But they are common for adults in Mediterranean countries. And these countries generally have lower rates of heart disease. So scientists in the United States and Greece wondered if naps could play a part.

Twenty-three thousand healthy adults took part in the study by Harvard University and the University of Athens. Those who took thirty-minute naps three times a week had a thirty-seven percent lower risk of death from heart problems than people who did not take naps.

The researchers say napping may improve heart health by reducing stress. They say the research suggests that naps are especially good for working men. But they say not enough female subjects died during the study to judge the benefits for women