Head injury, pesticide exposure tied to Parkinson's disease:study
Nov 14 (Reuters) - The combination of a past serious head injury and pesticide exposure may be linked to an extra-high risk of developing Parkinson's disease, according to a U.S. study.
The findings, which appeared in the journal Neurology, don't prove that being knocked unconscious or exposed to certain chemicals - particularly an herbicide called paraquat - directly causes Parkinson's, a chronic movement and coordination disorder.
But they are in line with previous studies, which have linked head trauma and certain toxins, along with family history and other environmental exposures, to the disease.
"While traumatic brain injury and paraquat exposure each increase the risk of Parkinson's disease moderately, exposure to both factors almost tripled Parkinson's disease risk," wrote lead researcher Pei-Chen Lee, at the University of California at Los Angeles, and colleagues.
"These environmental factors seem to act together to increase Parkinson's disease risk in a more than additive manner."
For the study, the researchers compared 357 people with a recent Parkinson's diagnosis to a representative sample of 754 people without the disease. All lived in central California, a major agricultural region.
The study team asked all of them to report any past traumatic head injuries, in which people had been unconscious for at least five minutes, and used their home and work addresses to determine their proximity to pesticide sprayings since 1974.
Those surveys showed that close to 12 percent of people with Parkinson's had been knocked unconscious, and 47 percent had been exposed to paraquat near both their home and workplace.
That's in comparison to almost seven percent of control-group participants with a history of head injury and 39 percent with pesticide exposure.
On their own, traumatic brain injury as well as living and working near pesticide sprayings were each tied to a moderately increased risk of Parkinson's - but combined, they were linked to a tripling of that risk, the researchers said.
That was after taking into account people's baseline risk based on their age, gender, race, education, smoking history and family history of Parkinson's.
Lee's team didn't know which came first in people who'd had both head trauma and paraquat exposure, but they said it made sense that a head injury would increase inflammation in the brain and disrupt the barrier that separates circulating blood and brain fluid.
Those changes could then make neurons in the brain more vulnerable to the effects of pesticides, ultimately increasing the risk of Parkinson's - although this is just a theory.
"I think all of us are beginning to realize that there's not one smoking gun that causes Parkinson's disease," said James Bower, a neurologist from the Mayo Clinic in Rochester, Minnesota, who wasn't involved in the research.
For example, he said, some people who are genetically predisposed might need just one "environmental insult" - such as a blow to the head - to set them up for Parkinson's. Others who aren't naturally susceptible could still develop it after multiple exposures.
The study "is more evidence that traumatic injury to the brain can lead to later problems that are usually neurodegenerative," he added. "We need to be increasingly careful about preventing these traumatic brain injuries." SOURCE: bit.ly/TD3OA9 (Reporting from New York by Genevra Pittman at Reuters Health; editing by Elaine Lies)
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