The reason for the association between education and RBD is unclear, but it could be that people with less education have different types of dreams that cause them to act out less, Harris said.
The relationship among certain factors was different for RBD and Parkinson's. Whereas caffeine intake and cigarette smoking seem to protect people against Parkinson's symptoms, the researchers found no association between caffeine use and RBD risk and that smoking increased the risk of having RBD by 43 percent.
"I find that quite interesting," Postuma said. "It makes you think about the mechanisms of these diseases."
The study found an association -- not a cause-and-effect link -- between these various factors and the risk of RBD.
Some forms of Parkinson's probably involve degeneration of nerve cells in the sleep region of the brain before the disease strikes the motor areas, causing tremors and coordination problems, Postuma explained.
Not all patients with RBD will develop Parkinson's or DLB, however, and it may be that some forms of RBD affect only the part of the brain involved in sleep regulation, he added.
"People who have RBD should see a neurologist," Postuma said. Even though it is not possible to prevent Parkinson's or DLB, doctors can monitor these patients and make sure they get the best treatment to manage their disease.
RBD is also treatable, and the most common medication is clonazepam (brand name Klonopin), which can relax muscles during sleep, Harris said.
"The first thing we always do is modify the sleep environment to reduce the risk of injury," she said.
Postuma and his colleagues are now studying other factors that could increase the risk of RBD, including family history and certain medications and diseases.
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