Pesticide Use Ups Parkinson's in Men
Parkinson's Disease Risk: Interplay of Environmental Exposures, Genetics
Why Men, but Not Women?
It might seem that men simply get exposed to pesticides more than women. But that explanation doesn't fit the data, Maraganore says.
He offers two theories. One is that estrogen -- known to protect the brain from toxins -- also protects the brain against the Parkinsonian effects of pesticides.
The other theory is that the genes that interact with pesticides to cause Parkinson's diseaseParkinson's disease are on the X chromosome. Men have only one X chromosome; women have two. If an X-chromosome gene is defective in women, there is a 50-50 chance that the normal gene on the other X chromosome will be the active one.
"Women have only half of the exposure to a random X-chromosome gene variant as men," Maraganore suggests. "So women could be protected vs. men."
But women don't get a free ride. Some chemical exposures seem to put women at greater risk of Parkinson's disease than men, Opanashuk says.
"Women are not off the hook," she says. "There could be genetic differences that render women susceptible. PCBs have been linked to risk for Parkinson's disease. [A recent study] found a potential sex linkage, and women seem to be more susceptible."
As scientists learn more about how chemicals affect Parkinson's risk, they get sorely needed clues about the cause of this mysterious disease.
Meanwhile, Maraganore says everyone should closely follow safety precautions when using pesticides.
"We aren't saying people should not use pesticides, but this argues for regulatory bodies to make sure these agents are safe and to make sure the reasons for their use are clearly stated," he says. "And if I am what I eat, am I going to be a healthy person if I eat foods contaminated with possible harmful substances?"