Dr. Jim Maraganore of the Mayo Clinic

Researchers from the Mayo Clinic in Minnesota have found that using pesticides increases men's risk of developing Parkinson's disease, a debilitating neurological condition that affects movement. Dr. Jim Maraganore matched about 150 Parkinson's patients with a group of the same age and gender without the disease. He compared their histories, looking for exposure to insecticides and herbicides. "These were people who were reporting exposures… regular exposures to pesticides either at work or outside of work."

Scientists already know that men are more likely to get Parkinson's disease than women. But Maraganore found a more significant difference between the sexes in his study. "Women who were exposed to pesticides, whether at work or outside of work, had no increased risk for Parkinson's disease," he says. "But by contrast, men who were exposed to pesticides at work or outside of work had more than a doubling in their risk for Parkinson's disease."

Maraganore says the gender difference raises interesting ideas about the causes of Parkinson's disease. He says one possibility is that women's sex hormones might protect their nervous systems. Another might be the fact that the female body can suppress problems on one of their X-chromosomes, and use genes from their second X-chromosome. But men have only one X-chromosome.

"So one possibility is that to get Parkinson's disease, you not only have to be exposed to pesticides, but you have to be genetically predisposed," he explains. "And if that genetic predisposition is X-linked, then men may be more likely to be vulnerable when exposed than women."

Maraganore notes that Parkinson's is a complex disease with no single cause. He estimated that pesticide exposure accounts for only 10 to 15% of cases.