VOICE ONE:
This is Sarah Long.
VOICE TWO:
And this is Bob Doughty with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science.
Today we tell about the pain medicine aspirin.
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Aspirin is one of the world's oldest, least costly and most widely used drugs. It makes people feel better. It is a common treatment for headaches, colds and flu. It also reduces other kinds of pain, such as pain in bone joints caused by arthritis.
A drug like aspirin is said to have been used in ancient Greece. More than two-thousand-four-hundred years ago, Hippocrates told his patients to ease pain by chewing the outer covering of the willow tree. The covering, called bark, contains the chemical salicylic acid.
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In the Seventeen-Hundreds, people used willow bark to reduce a sick person's high body temperature. In Eighteen-Sixty, researchers at the Bayer Company in Germany copied the salicylic acid found in willow bark. They created acetyl salicylic acid. They called it aspirin, for the spirea plant which also contains the natural chemical. Aspirin first was made into its present pill form about one-hundred years ago.
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In Nineteen-Eighty-Two, British scientist Sir John Vane shared the Nobel Prize in Medicine in part for discovering how aspirin works. He found that aspirin blocks the body from making natural substances called prostaglandins.
Prostaglandins have several effects on the body. Some cause pain and swelling in damaged tissue. Others protect the lining of the stomach and small intestine. Prostaglandins also make the kidneys, heart and blood vessels work well. The problem with aspirin is that it works against all prostaglandins -- good and bad.
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Scientists have learned how aspirin interferes with a protein enzyme. One form of the enzyme makes the prostaglandin that causes pain and swelling. Another form of the enzyme creates the protective kind of compound. So, while aspirin can reduce pain and swelling in damaged tissues, it also can harm the lining of the stomach and small intestine. Still, aspirin does things that other drugs for treating pain cannot do.
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Scientists know that aspirin prevents tiny blood cells called platelets from sticking together to form blood clots. Clots can block the flow of blood to the heart or the brain. They can cause heart attacks or strokes. A few years ago, some doctors began advising people to take aspirin to prevent heart attacks and strokes. One doctor noted this effect of aspirin more than forty years ago.
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The doctor was Lawrence Craven. He observed unusual bleeding among children who chewed an aspirin gum to ease pain after a throat operation. Doctor Craven believed they were bleeding because aspirin prevented the blood from thickening or clotting. He decided that aspirin might help prevent heart attacks caused by blood clots in blood vessels.
In the Nineteen-Fifties, Doctor Craven examined medical records of about eight-thousand people. He found no heart attacks or strokes among those who regularly took aspirin. Doctor Craven invited other scientists to test his ideas with modern methods. But, it was many years before large studies were carried out.
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One study was begun in Nineteen-Eighty-Three by Charles Hennekens of Harvard University Medical School in Cambridge, Massachusetts. He began studying more than twenty-two-thousand healthy male doctors over the age of forty. Half of the doctors in the study took an aspirin every other day. The other half took an inactive pill. Five years later, Doctor Hennekens reported that the men who took aspirin reduced their chances of having a heart attack by forty-four percent.
However, the study also found that the men who took aspirin had almost two times the rate of bleeding in the brain as the other group. Thousands of men had refused to take part in the study because aspirin caused them to suffer stomach problems.
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A group of American medical experts recently said that people who have an increased risk of suffering a heart attack should take a small amount of aspirin every day. The experts examined studies on aspirin for the Department of Health and Human Services. They said research has shown that taking an aspirin each day can reduce the chance of suffering a heart attack in the future.
People likely to suffer a heart attack include men over the age of forty and women over the age of fifty. The group also includes people who weigh too much or smoke cigarettes. It also includes people who suffer diabetes, heart disease, high blood pressure, or high cholesterol levels.
Doctors say aspirin should be given to anyone who is having a heart attack because of a blocked blood vessel in the heart. Aspirin lets blood continue to flow past the blockage in the artery. Research has shown that taking aspirin during a heart attack lowers the chance of death by about twenty-five percent. It also lowers the chance of having a second heart attack by fifty percent.
Some people should not take aspirin, however. They include people who have stomach problems, or suffer bleeding, or take medicines to thin the blood.
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New research has provided information about the effects of aspirin on the brain. Several small studies have shown that taking aspirin can affect older people with thinking problems. Those who took aspirin did not lose their reasoning abilities as soon as those who did not take aspirin. Doctors think aspirin can help prevent small strokes that result from blocked blood vessels in the brain.
Some studies have been done on the effects of people taking aspirin during the first signs of a stroke. These show a fifteen to twenty-five percent improvement in the patients’ condition. But researchers have not been able to find any evidence that aspirin can prevent strokes in healthy people.
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A study of aspirin and strokes was published in the “Archives of Neurology.” Robert Hart and others at the University of Texas at San Antonio examined studies of aspirin and stroke prevention in more than fifty-thousand healthy people. Some of the people already had an increased risk of stroke, like high blood pressure. Others had no signs that they could suffer a stroke in the future.
The researchers found that aspirin did not seem to prevent strokes as long as people had no signs of blocked blood vessels in the brain. Often, taking aspirin was linked with a small increased risk of bleeding in the brain. This also can cause a stroke.
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Aspirin often causes problems in the stomach or intestines, especially if taken in large amounts. These problems can include life-threatening bleeding. Such problems are caused by damage to the tissue inside the stomach or intestines. The acid in aspirin irritates the tissue, and the drug interferes with natural healing of the cells.
However, researchers also have found that aspirin may prevent cancers of the stomach and intestines. Studies done in the last twenty years have shown that people who take aspirin have unusually low rates of such cancers.
Steven Shiff is a researcher at Rockefeller University in New York City. Studies in his laboratory have shown that aspirin destroys cells in the lining of the intestines before they can become cancerous. This action may also injure other cells and cause bleeding.
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Medical experts continue to say that no one should begin taking aspirin to prevent heart attacks or strokes without first asking their doctor. They also say people should not take aspirin instead of doing other things that can prevent heart attacks and strokes. They say people should exercise, stop smoking cigarettes and eat foods low in fat.
Doctors do not believe aspirin is safe for everyone. They do not believe pregnant women should take the drug. And, they say children should not take aspirin. Studies show that children who take aspirin for a sickness like flu or chicken pox have a much greater chance of developing a serious disease called Reye's syndrome.
Even with its problems, aspirin still is considered one of the most valuable drugs ever discovered.
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This VOA Special English SCIENCE IN THE NEWS program was written by Nancy Steinbach and Avi Arditti. This is Sarah Long.
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And this is Bob Doughty. Join us again next week for more news about science in Special English on The Voice of America.