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This is SCIENCE IN THE NEWS, in VOA Special English. I'm SarahLong.

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And I'm Bob Doughty. Today we talk about a medicine that hasfound new uses over time.

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And may find even newer ones.Learn the history of aspirin, and the most recent findings, comingup.

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More than two-thousand years ago, in ancient Greece, Hippocratesadvised his patients about a way to ease pain. The great doctor toldthem to chew on the bark of the willow tree. The outer covering ofthe tree contains a chemical, salicylic acid.

By the seventeen-hundreds, people used willow bark to reduce highbody temperatures.

In eighteen-sixty, researchers at the Bayer Company in Germanycopied nature. They created acetyl salicylic acid. And they took aname from the spirea plant, which also contains the naturalchemical. They called their new formula aspirin.

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Aspirin has been sold for more than a century as a treatment forheadaches, muscle pain and high temperature.

In nineteen-eighty-two, a British scientist shared the NobelPrize in Medicine in part for discovering how aspirin works. SirJohn Vane found that aspirin blocks the body from making naturalsubstances called prostaglandins.

Prostaglandins have several effects on the body. Some cause painand swelling in damaged tissue. Others protect the lining of thestomach and small intestine. Prostaglandins also make the kidneys,heart and blood vessels work well. But there is a problem. Aspirinworks against all prostaglandins, good and bad.

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Scientists learned how aspirin interferes with an enzyme. Oneform of this protein makes the prostaglandin that causes pain andswelling. Another form of the enzyme creates the protective kind ofcompound. So aspirin can reduce pain and swelling in damagedtissues. But it can also harm the lining of the stomach and smallintestine.

Aspirin competes these days with a lot of other pain medicines.Many people like to take acetaminophen. This is the active substancein products like Tylenol. Still, experts say aspirin does somethings that the others cannot.

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Many people take aspirin to reduce the risk of a heart attack.

Scientists say aspirin prevents tiny blood cells called plateletsfrom sticking together to form clots. Clots can block the flow ofblood to the heart or the brain. This can cause heart attacks orstrokes.

The use of aspirin to reduce the risk of heart disease has grownin recent years. Yet one doctor noted this effect in thenineteen-fifties.

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The doctor was Lawrence Craven. He observed unusual bleedingamong children who chewed on aspirin gum to ease pain after a throatoperation. Doctor Craven believed they were bleeding because aspirinprevented the blood from thickening. He decided that aspirin mighthelp prevent heart attacks caused by blood clots.

So Doctor Craven examined medical records of about eight-thousandpeople. He found no heart attacks or strokes among those whoregularly took aspirin. Doctor Craven invited other scientists totest his ideas. But it was many years before large studies tookplace.

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Doctor Charles Hennekens of the Harvard Medical School in Boston,Massachusetts, led one of the studies. In nineteen-eighty-three, hebegan to study more than twenty-two-thousand healthy male doctorsover the age of forty.

Half the doctors in the study took an aspirin every other day.The other half took what they thought was aspirin, but was just asugar pill. Five years later, Doctor Hennekens reported that the menwho took aspirin reduced their chances of a heart attack. However,the men who took aspirin also had a higher risk of bleeding in thebrain.

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In recent years, a group of American medical experts examinedstudies on aspirin for the Department of Health and Human Services.The experts said people who have an increased risk of a heart attackshould take a small amount of aspirin every day.

People who are most likely to suffer a heart attack include menover the age of forty and women over the age of fifty. People whoweigh too much or smoke cigarettes are also at greater risk. So arepeople with diabetes, heart disease, high blood pressure or highcholesterol.

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Aspirin may help someone who is having a heart attack caused by ablockage in the flow of blood to the heart. Aspirin thins the blood.This can permit blood to flow past the blockage in the artery. Butheart experts say people should seek emergency help immediately.They say an aspirin is no substitute for treatment.

Some people should not take aspirin. These include people whohave stomach problems. Doctors say people who take other bloodthinners or have bleeding disorders should not take aspirin either.

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Some studies have been done on the effects of taking aspirinduring the first signs of a stroke. These studies showed someimprovement in the condition of the patients. But can aspirinprevent strokes in healthy people?

The Archives of Neurology published a report in two-thousandabout aspirin and stroke prevention. Robert Hart and others at theUniversity of Texas at San Antonio examined studies of more thanfifty-thousand healthy people.

Some of the people already had an increased risk of stroke, likehigh blood pressure. Others had no signs that they might suffer astroke in the future.

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The researchers found that aspirin did not seem to preventstrokes, as long as people had no signs of blocked blood vessels intheir brain. Doctors say aspirin may help prevent small strokes thatresult from such blockage. But the report said aspirin was linked toa small increase in the risk of bleeding in the brain. This can alsocause a stroke.

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Like other medicines, aspirin can cause problems, especially iftaken in large amounts. The acid in the drug may damage the tissueof the stomach or intestines. Aspirin can also interfere with thehealing of the cells. Some people develop severe bleeding.

Yet other research has found that aspirin may help preventcancers of the stomach and intestines. Studies in the last twentyyears have shown that people who take aspirin have unusually lowrates of such cancers.

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One of the newest reports about aspirin involves the most commonform of breast cancer. In May, researchers announced findings from astudy of almost three thousand women in New York City. The studycompared women who took aspirin several times a week to women whodid not. Scientists from Columbia University say the aspirin usershad a twenty-five percent lower rate of breast cancer.

One of the doctors involved in the study said aspirin appeared toreduce the production of estrogen. This female hormone is linked toup to seventy percent of all cases of breast cancer.

The Journal of the American Medical Association published thefindings. But the researchers say they are not ready to advise womento take aspirin in hopes of protection against breast cancer.

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But doctors do often advise aspirin for patients at risk ofdiseases that result from blood clots, such as a heart attack. InMay, a Harvard Medical School publication said that some people,however, get little or no protection from aspirin. The Harvard HeartLetter said this idea is so new that many doctors do not know aboutit, or they are waiting for more research. Still, the report advisedthat it is not too early for people to ask about being tested to seeif they respond to aspirin.

In any case, medical experts say no one should take aspirin fordisease prevention without first asking a doctor. Aspirin is sold indifferent strengths. It can interfere with other drugs. And it isnot safe for everyone. Most pregnant women are told to avoidaspirin. Children who take aspirin can suffer a serious diseasecalled Reye's syndrome.

Yet, even with its problems, aspirin remains one of the oldest,least costly and most widely used drugs in the world.

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This SCIENCE IN THE NEWS program was written by Caty Weaver andproduced by Cynthia Kirk. This is Bob Doughty.

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And this is Sarah Long. Join us again next week for more newsabout science in VOA Special English.