Pesticide link to Parkinson's probed

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http://www.msnbc.com/news/740692.asp

Pesticide link to Parkinson's probed

Preliminary study of farmers implicates several compounds

By Sommerfeld

MSNBC

DENVER, April 19 - Preliminary results from a study of thousands of farmers

in Iowa and North Carolina suggest exposure to several crop pesticides may

be linked to the development of Parkinson's disease.

DOCTORS HAVE consistently observed that the neurodegenerative disease is

more common in people who live in farming communities, leading them to

speculate that exposure to pesticides increases a person's risk of

developing the disease. But little work has been done looking at the effects

of specific compounds on people over time, said study co-author Dr.

Goldman, a research scientist at the Parkinson's Institute in Sunnyvale,

Calif.

The question of the role of environmental factors in the development

of Parkinson's was thrown into the spotlight earlier this month when it was

revealed that four people, including actor J. Fox, who worked

together at the Canadian Broadcasting Company in the late 1970s have

developed the dreaded disease, which affects an estimated 1.2 million people

in the United States and Canada.

" The idea of some link to environmental toxins is becoming pretty

well-accepted, but the exact ones and how much you have to be exposed to be

at risk of Parkinson's disease isn't clear, " said Dr. Robin Brey, a

professor of medicine, division of neurology, at University of Texas Health

Sciences Center, San .

Brey said that while this study doesn't answer these questions once

and for all, it suggests tantalizing links that need to be probed further.

FARMER STUDY

For the study, a team of researchers surveyed over 20,000 farmers -

55 of whom reported having Parkinson's disease - in the mid-1990s about

their health history and exposures to specific pesticides.

Dr. Freya Kamel, an epidemiologist at the National Institute of

Environmental Health, presented the initial findings to members of the

American Academy of Neurology meeting in Denver this week.

The study found the use of several crop pesticides was more common

among the Parkinson's group than the non-affected farmers: dieldrin,

paraquat, maneb, rotenone and a class of insecticides known as

organochlorines.

Those with Parkinson's were 80 percent more likely to have been

exposed to dieldrin. The other pesticides appeared to carry an increased

risk ranging from 20 percent to 60 percent.

These pesticides have been shown in test-tube studies or laboratory

animal experiments to have toxic effects on certain brain cells, which can

lead to Parkinson's-like symptoms of tremor, rigidity, slowness of movement

and imbalance.

Dieldrin, an insecticide, is now banned in the United States;

rotenone, a pesticide, has been banned for agricultural use though it is

still used to kill unwanted fish in reservoirs. Paraquat, an herbicide, and

maneb, a fungicide, are still used by farmers.

The study also found high-exposure methods of application, where the

pesticide was likely to get on the skin or be inhaled, also were more

commonly reported by the farmers with Parkinson's.

Interactive Questions:

Select a question --Who gets Parkinson's?What causes it?What are the most

common symptoms?How quickly does the condition progress?How is it treated?

Parkinson's disease is a disorder of the central nervous system that affects

more than 1 million Americans.

Click on a question for more information on the condition.

Age is one of the main risk factors for Parkinson's disease. The average age

of onset is in the mid-50s, though up to 10 percent of patients develop

symptoms before the age of 40. Heredity also appears to play a role - recent

research shows that people with a close relative with the disease have a

three times greater risk of developing it themselves. In addition, people

who are exposed to herbicides and pesticides have been shown to have an

increased risk. Also, men are affected slightly more often than women.

Doctors don't know exactly what triggers the disease, but they do know that

Parkinson's results in the degeneration of cells in a part of the brain

called the substantia nigra. This region produces dopamine, a substance that

allows people to move normally. People with Parkinson's have a shortage of

dopamine.

The hallmark symptoms are tremors, rigidity, slowness of movement and

postural instability. The earliest signs are tremors and slowness of

movement that are usually worse on one side of the body than the other. As

the disease progresses, it causes rigidity and then later on leads to

instability of stance and posture.

Mental function is usually not affected in early Parkinson's but there can

be cognitive deterioration as the disease progresses. Up to 25 percent of

patients with advanced disease experience some level of mental impairment,

such as memory loss and poor concentration.

It really varies from person to person. But Parkinson's usually advances

more slowly in younger people than the elderly. Still, the rate of

progression is variable and impossible to predict.

There is no drug that can prevent cell loss in the substantia nigra. Doctors

can only treat the symptoms with a number of drugs:

.. Levodopa

.. Carbidopa combined with levodopa (Sinemet)

.. Symmetrel (amantadine hydrochloride)

.. Anticholinergics (trihexyphenidyl, benztropine mesylate, procyclidine,

etc.)

.. Selegiline or deprenyl (Eldepryl)

.. Dopamine agonists (bromocriptine, pergolide, pramipexole and

andropinirole)

.. COMT inhibitors (tolcapone, entacapone, etc.)

Also available for some Parkinson's patients are surgical interventions

including brain tissue transplants, using an electrode to destroy the cells

that cause unwanted movements and deep brain stimulation with a

pacemaker-like device.

Source: Dr. Ali Samii, a neurologist at the University of Washington in

Seattle; Parkinson's Disease Foundation

But researchers do not think that exposure to these pesticides

necessarily results in Parkinson's disease.

" We don't think any one compound causes Parkinson's disease because

then we would expect to see more clusters of cases, " said Goldman. " So it

has got to be a whole lifetime of mild insults that set off a degenerative

cascade in the brain. "

Most experts think that a complex interaction between a person's

genes and environmental exposures is at play in the development of Parkinson

's.

Kamel acknowledged that the data does not prove a relationship

because it included only a small number of Parkinson's patients and relied

on self-reports of the disease, which may be inaccurate.

" It's a very dirty study at this point, " Brey said. " Self-reports

have a tremendous potential for bias. Many patients may have tremor and say

they have Parkinson's. The diagnosis clearly needs to be confirmed. "

Which is exactly what the research team plans to do. Noting that the

new preliminary results come from the initial phase of an ongoing

government-funded study of more than 84,000 pesticide applicators and their

spouses, Kamel said the next step will be to identify more Parkinson's

patients, have neurologists confirm the diagnosis, and test their blood and

homes for pesticide levels.

This major endeavor is widely hoped to definitively answer the

question about the role of pesticide exposure in Parkinson's, neurologists

here said.

OTHER FINDINGS

Researchers at the meeting also reported a potential link between

eating a lot of foods that contain compounds known as isoquinolines (IQs) -

such as chocolate, cheese, milk and wine - and Parkinson's disease.

IQs have been shown in laboratory animals to inhibit cellular

function and lead to Parkinson's-like symptoms.

Goldman, who was lead author of this study, asked 72 pairs of twins

in which one had Parkinson's and the other did not about their dietary

habits in the 10 years prior to one of them developing the disease.

He found those who ate a lot of chocolate - two to three candy bars

per week - had more than a three-fold increased risk of having Parkinson's

than those who ate less. He also found a smaller link with wine and with a

measure of total IQ consumption.

" The population is fairly small and the data is extremely

retrospective, " he said. " But in basic science research there's probably a

reason to suspect these compounds. "

Brey noted that dietary histories are often unreliable. " People don't

remember what they've eaten years ago and if you had bad information you are

going to have erroneous results.

" I would hate for someone to stop eating chocolate and cheese because

of this study, " she said.