The combination of a past serious head injury and pesticide exposure may be linked to an extra-high risk of developing Parkinson's disease, a new study suggests. The findings don't prove being knocked unconscious or exposed to certain chemicals 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. "I think all of us are beginning to realize that there's not one smoking gun that causes Parkinson's disease," said Dr. James Bower, a neurologist from the Mayo Clinic in Rochester, Minnesota who wasn't involved in the new research. "There might be many paths to the ultimate development of Parkinson's disease," he said. For example, Bower 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 to the disorder could still develop it after multiple exposures. For the new study, researchers led by Pei-Chen Lee from the University of California at Los Angeles compared 357 people with a recent Parkinson's diagnosis to a representative sample of 754 people without the disease, all living in central California, which is 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 an herbicide called 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 disease. Combined, they were linked to a tripling of that risk, the researchers reported in the journal Neurology. 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. http://english.ahram.org.eg/News/58076.aspx
