This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty.
And I'm Faith Lapidus. Our subject this week is Parkinson's disease.
Muhammad Ali is known around the world as one of the great sports stars of the twentieth century. He needed great energy and power to became the world boxing champion.
As he grew older, though, he began to change. The energy and power began to disappear. His face lost its expressiveness. His legs lost their speed.
Muhammad Ali is sixty-four now and long retired from boxing. Yet it was not age that changed him so much. It was Parkinson's disease.
Parkinson's is a disease of the central nervous system. It is a progressive disorder. It gets worse over time.
The disease affects a small area of cells in the middle of the brain. This area is called the substantia nigra. The cells slowly lose their ability to produce a chemical called dopamine.
The decrease in the amount of dopamine can result in one or more of the general signs of Parkinson's disease.
These include shaking in the hands, arms and legs. They also include difficulty in moving or general slowness of movement. Another symptom is difficulty keeping balanced while walking or standing.
Other signs in some people include decreased movement of the face. Victims might swallow less often than normal. And they might have difficulty forming words when they talk. Also, there can be emotional changes, like feeling depressed or worried.
The disease is named after James Parkinson. He was a British doctor who first described this condition in eighteen seventeen. Doctor Parkinson did not know what caused it.
During the nineteen sixties, medical researchers discovered changes in the brains of people with the disease. These discoveries led to medicines to treat the effects. There is no cure, however, and no way that doctors know of to prevent it. And there is still mystery about the cause.
Parkinson's is found in all parts of the world. At least six million people have the disease. Most are older adults. But fifteen percent of patients develop the disease before they are fifty years old. Also, it affects men a little more often than women.
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Most patients have what is called idiopathic Parkinson's disease. Idiopathic means the cause is unknown. People who develop the disease often want to link it to some cause they can identify. This might be an injury or a medical operation or extreme emotional stress.
Many doctors, however, reject this idea of a direct link to Parkinson's. The doctors point to other people who have similar experiences and do not develop the disease. Still, doctors say it is possible that such events might cause symptoms of Parkinson's to appear earlier than they would have.
Some medicines used to treat other problems can cause movement disorders similar to Parkinson's disease. These include medicines used to treat older adults who see things that do not exist. And they include some drugs used to treat people suffering from extreme tension or from stomach problems.
Another disease that can cause movement problems and other effects like those of Parkinson's is encephalitis. In the early twentieth century, encephalitis spread to many parts of the world.
Many victims of the disease had symptoms similar to Parkinson's disease. This led to investigations into the possibility of a virus as a cause of Parkinson's. But scientists could not find evidence to support this theory.
Another area of study is family genetics. There are some cases of many members of a family having the disease.
In two thousand four, scientists linked changes in a gene called PARK-eight to cases of Parkinson's disease in some families. They identified the gene in a study of five families with a history of the disease. The families lived in England and in the Basque area of Spain.
Other research involves genes that might increase the risk of Parkinson's disease in some ethnic groups. Two new studies looked for changes in a gene called LRRK-two as a cause of Parkinson's in Jews and North African Arabs.
Researchers in the United States led one of the studies. They tested the genes of one hundred twenty Ashkenazi Jews with Parkinson's disease. Ashkenazi Jews are those whose ancestors came from eastern Europe.
The study found changes in the LRRK-two gene in eighteen percent of the patients. That compares to just one percent of a healthy group. The rate was highest, thirty percent, among patients with a family history of Parkinson's.
Researchers in France and Algeria carried out the other study. They tested the genes of fifty-nine North African Arabs with Parkinson's disease. They found the same genetic changes in about forty percent of them, compared to three percent in a healthy group.
The New England Journal of Medicine published the results of both studies at the end of January.
Improved treatments to ease the symptoms of Parkinson's disease make it possible for many patients to live almost normal lives. People who have lost their ability to do many things might be able to regain some of their old abilities with treatment.
The most commonly used drug is levodopa. When it reaches the brain, levodopa is changed into dopamine, the chemical that is lacking in people with the disease.
Levodopa helps deal with the symptoms of Parkinson's. But it does not prevent more changes in the brain that are caused by the disease. It can also produce unwanted effects in some people.
These side effects include feeling sick to the stomach. To prevent this from happening, other substances can be combined with levodopa.
Other drugs used to treat Parkinson's disease act like dopamine. They produce reactions in the nerve cells in the brain.
Experts at the National Institutes of Health say an antiviral drug called amantadine also appears to reduce symptoms of the disease.
Doctors sometimes perform operations to treat Parkinson's. Recently, the United States Food and Drug Administration approved an operation called deep brain stimulation, or D.B.S. Doctors place small electrical devices into the brain. These are connected to a small piece of equipment called a pulse generator.
Deep brain stimulation can reduce the need for levodopa and other drugs. It also helps to reduce symptoms such as shaking, slowness of movement and problems with walking.
Another development in the treatment of Parkinson's disease is brain tissue transplants. This involves replacing tissue in areas connected to symptoms of the disease.
Early experiments used brain tissue from unborn babies. Doctors said the experiments appeared to have highly successful results. But the experiments became a subject of moral debate over the issue of ending unwanted pregnancies.
Researchers have begun working with genetically changed cells and animal cells that can be made to produce dopamine.
Still, most doctors agree that such operations should be considered only after drugs fail to treat the signs of Parkinson's disease.
The symptoms of Parkinson's differ from person to person. They also differ in their intensity. Some people develop minor effects. Others become severely disabled as the effects get worse.
Around the world, there are groups that provide education and support services for patients and their families. Last month, the World Parkinson Congress took place in Washington, D.C. More than two thousand people, from scientists to patients, gathered to discuss the latest progress and treatments.
SCIENCE IN THE NEWS was written by George Grow and Oliver Chanler. Cynthia Kirk was our producer. I'm Bob Doughty.
And I'm Faith Lapidus. Read and listen to our programs at WWW.51VOA.COM. And we hope you join us again next week for more news about science in Special English on the Voice of America.