Pesticides Could Raise Parkinson's Risk
Type and duration of exposure needed isn't yet clear, researchers say
By Alan Mozes
HealthDay News, June 26, 2006
Straight to the Source
Exposure to pesticides, but not other
environmental contaminants, may boost the long-term risk for developing
Parkinson's disease by 70%, a new study suggests.
The researchers did not assess the length, frequency, or strength of pesticide
exposure, and they stressed that the absolute risk of developing Parkinson's
remains relatively small.
However, their finding does back up earlier animal studies linking pesticide
exposure to motor function abnormalities and lower levels of the brain
neurotransmitter dopamine. Declines in dopamine have long been associated with
Parkinson's.
"This is the first large human study that shows that exposure to pesticide
is associated with a higher incidence of Parkinson's," said study lead
author Dr. Alberto Ascherio, associate professor of
nutrition and epidemiology at the Harvard School of Public Health in Boston.
"It is, of course, a relative increase," emphasized Ascherio. "So, whereas normally the lifetime risk for
developing Parkinson's is three percent, pesticide exposure will bring the risk
to five percent."
Ascherio and his colleagues discussed their work in
the July issue of the Annals of Neurology.
The authors reviewed lifestyle surveys completed in both 1982 and in 2001 by
over 143,000 participants in the
In addition to pesticide exposure, participants were asked about exposure to a
host of chemicals and dusts, such as: asbestos, acids, solvents, coal and stone
dust, coal tar, asphalt, diesel engine exhaust, dyes, formaldehyde, gasoline
exhaust, herbicides, textile fibers, wood dust, and x-ray or radioactive
materials. Nearly all the patients were white, with an average age just of over
60.
In total, 413 participants went on to develop Parkinson's disease.
The surveys revealed that just over eight percent of the men and just over
three percent of the women reported exposure to pesticides.
Exposed patients were twice as likely to be blue-collar workers and 14 times
more likely to work as either a farmer, rancher, or
fisherman.
However, no differences were found in terms of risk increase between patients
who experienced exposure because of their work, such as farmers, and those who
came into contact with the chemicals because of home or garden use.
The Harvard team found that, regardless of occupation, pesticide exposure
boosted long-term Parkinson's risk by 70% over the long-term.
Ascherio stressed that although the association found
in his study was stronger than any previously documented,
more work is needed to pinpoint what exactly it is about pesticides that may
help spur Parkinson's.
"The key point would be to identify which chemicals cause
Parkinson's," he said. "It's not very practical to tell people to
avoid pesticides, because many people find it very useful. So this will require
more detailed study," he added.
Robin Elliot, executive director for the Parkinson's Disease Foundation in
"This is certainly the biggest and most serious populations study on
people, and it appears to be the best proof today that there is a general
association between pesticide and Parkinson's among people," said Elliot.
"It merits further investigation," he said.
In a separate smaller study, published in the June issue of Movement Disorders,
a team of researchers from the Mayo Clinic in
Telephone interviews were conducted with 149 men and women, all local-area
Parkinson's patients who developed the illness between 1976 and 1995. The Mayo
team also interviewed 129 healthy individuals.
They found that male patients were 2.4 times more likely than healthy
individuals to have been exposed to pesticides. No such increased risk was
evident among the female patients.