Risk factors for Parkinson's disease under study-impaired smell early indicator

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Public release date: 7-Jan-2008

http://www.eurekalert.org/pub_releases/2008-01/mcog-rff010708.php

Contact: Hilliard

jhilliard@...

Medical College of Georgia

Risk factors for Parkinson's disease under study

http://www.eurekalert.org/pub_releases/2008-01/mcog-rff010708.php

Doctors know an impaired sense of smell is an early indicator of

Parkinson’s Disease.

Now they want to know if a smell test can help determine if people with

no symptoms eventually develop the disease.

“The analogy would be like diagnosing coronary artery disease before the

heart attack,” says Dr. Kapil Sethi, director of the Movement Disorders

Program at the Medical College of Georgia and a lead investigator the

Parkinson’s Associated Risk Syndrome Study. “With Parkinson’s, we are

dependent on the presence of motor symptoms like tremors, stiffness and

slowness in order to diagnose it. By that time you have lost 50 to 60

percent of your dopaminergic cells, which make dopamine and are key to

movement control. The question becomes, is there a window between when

you had non-motor symptoms like loss of smell and when you begin to

demonstrate clinical motor symptoms " ”

Dr. Sethi and researchers at 17 other sites across the country will

recruit 15,000 close relatives of Parkinson’s patients as part of the

study, which is being led by the Institute for Neurodegenerative

Disorders and the University of Pennsylvania.

“By testing those with a family history of the disease, we have an

enriched population,” he says. “We already know that those people are

more at risk. To enrich the sample even further, we’ll test their sense

of smell. It’s not just the essence of a sense of smell that is

different in these people. It’s a quantitative decrease in their ability

to distinguish odors.”

Patients will be given the University of Pennsylvania’s Smell

Identification Test, which tests for 40 common odors and has been used

to detect the first signs of neurodegenerative disorders.

People with a normal sense of smell who take the test can usually

identify around 35 odors correctly. Parkinson’s patients typically can

only identify 20 or less.

The study will also help determine if the smell test can also predict

who will get Parkinson’s.

“We believe that if you’re a person who is going to develop Parkinson’s,

you’ll also score lower than others,” Dr. Sethi says.

Based on the results of the smell test, study participants will be

divided into two groups – those with a normal sense of smell and those

without. Both groups will undergo functional neuroimaging analyses at

the Institute for Neurodegenerative Disorders in New Haven. Functional

neuroimaging can identify changes in brain activity associated with

Parkinson’s.

Both also will be clinically examined by a movement disorder specialist

and followed for three to five years.

“We believe that a proportion of those who have the deteriorated sense

of smell will develop Parkinson’s over the next two or three years,” Dr.

Sethi says.

Study participants also will be asked about other common symptoms of the

disease that may be present prior to the telltale motor symptoms. For

example, people with Parkinson’s and other neurological diseases often

suffer from a sleep disorder called REM Behavior Disorder, which causes

them to act out their dreams.

“While most people are paralyzed when they dream so they can’t hurt

themselves or others, people with Parkinson’s are not,” Dr. Sethi says.

“They yell, scream and kick. No one knows why, but half of the people

who have this sleep disorder will develop Parkinson’s or a similar disease.”

Questions about excessive daytime sleepiness and anxiety and

constipation – other pre-symptoms of Parkinson’s – also will be asked.

“The goal is to give someone a degree of risk based on one or multiple

factors,” Dr. Sethi says. “We don’t know specific numbers now, but

hopefully, in the future, we will be able to tell people who have a

deteriorated sense of smell and the sleep disorder specifically how much

their risk goes up.”

The long-term goal, he says, is to develop prevention strategies once

risk is established.

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The study is open to those 50 or older who do not have Parkinson's but

have a mother, father, child or sibling with the disease. For more

information, call the MCG Movement Disorders Program at or

the Institute for Neurodegenerative Disorders .

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ne Holden, MS, RD < fivestar@... >

" Ask the Parkinson Dietitian " http://www.parkinson.org/

" Eat well, stay well with Parkinson's disease "

" Parkinson's disease: Guidelines for Medical Nutrition Therapy "

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