Parkinson's Linked to Pesticides, Head Trauma

Mar. 23 -- WEDNESDAY, May 30 (HealthDay News) -- Pesticides and head injury can both bump up risks for Parkinson's disease, European researchers report.

Moreover, odds for the illness increase as exposure to these brain insults rises, the report found.

For example, "Those who were heavily exposed to pesticides had a 41 percent increased risk of developing Parkinson's disease, and those with lower exposure had a 13 percent increased risk," said lead researcher Dr. Finlay Dick, from the Department of Environmental and Occupational Medicine at Aberdeen University Medical School, Aberdeen, U.K.

In addition, people who were knocked unconscious even once had a 35 percent increased risk of developing Parkinson's, Dick said.

That finding has real implications for sports such as boxing, the researchers said. In fact, professional boxing legend Muhammad Ali, 65, now suffers from advanced Parkinson's disease.

The findings are published in the May 30 online edition of Occupational and Environmental Medicine.

According to the National Parkinson Foundation, 1.5 million Americans currently have the degenerative illness, which strikes men and women in roughly equal numbers, usually after the age of 65.

In the study, Dick's team collected data on 959 people with Parkinson's or Parkinson's-like syndromes and almost 2,000 people without the condition. All the people were questioned about their exposure to pesticides as well as iron, copper and manganese. They were also asked if they had ever having been knocked unconscious or had a family history of Parkinson's disease.

The team found that people who had been exposed to low levels of pesticides were 13 percent more likely to have Parkinson's compared to people who had never been exposed. And people exposed to high levels of pesticides were 41 percent more likely to develop the condition.

Dick's group also found that Parkinson's disease occurred 35 percent more often in people who had been knocked unconscious once compared with those who had never been knocked out, and more than two-and-a-half times more frequently in people who had been knocked out more often.

In terms of pesticides, the researchers don't know which compounds are most likely to increase the risk for Parkinson's, Dick said. More research is needed, he added.

One take-home message: avoiding head injury is a good way to cut Parkinson's risk. "This has implications for contact sports, particularly for things like boxing," Dick said.

One expert lauded the research.

"This study adds to a growing body of evidence that points toward an association between exposure to environmental issues being related to neurodegenerative diseases like Parkinson's disease," said Dr. Michael S. Okun, the medical director of the National Parkinson Foundation.

He speculated that environmental exposures may trigger genes that spur the illness. "In some way, environmental exposures are affecting a series of events that unfold in the human brain that result in neurodegenerative diseases," he said.

While the causes of Parkinson's aren't known, Okun believes that it is a combination of factors, such as a genetic predisposition for the disease, coupled with environmental triggers.

"It would be a mistake to assume that this is a disease linked directly to pesticides or linked directly to genes and to close the door on potential interactions between them," he said.

More information

For more information on Parkinson's, visit the U.S. National Institute of Neurological Disorders and Stroke.

SOURCES: Finlay Dick, M.D., department of environmental and occupational medicine, Aberdeen University Medical School, Foresterhill, Aberdeen, Scotland; Michael S. Okun, M.D., medical director, National Parkinson Foundation, Gainesville, Fla.; May 30, 2007, online edition, Occupational and Environmental Medicine