RBD is rare compared with conditions like sleepwalking, which occurs during a different phase of sleep, Postuma explained. Previous research has found that one in 200 people have RBD, but Postuma thinks that number probably does not include mild cases.
Having RBD puts someone at much higher risk of developing Parkinson's or DLB -- between 38 percent and 75 percent of people with RBD also have a neurodegenerative disorder -- but people can have RBD for a decade or more before they develop one of those disorders, Postuma said.
For the study, Postuma and his colleagues recruited nearly 350 people with RBD from sleep clinics in the United States, Canada, Europe and Japan. The patients' average age was 67, and 81 percent of the group was male.
Because these participants were already going to a sleep clinic, they tended to have more severe cases of RBD, Postuma said. The participants did not have Parkinson's or dementia.
The control group included 281 people who had unrelated sleep problems, such as sleep apnea and insomnia, and 129 people with no sleep problems.
The researchers asked the participants about their exposure to many factors that have been associated with increased risk of Parkinson's or DLB, such as caffeine intake and head injuries.
They found that the biggest risk factor for RBD was pesticide exposure, which is also a risk factor for Parkinson's. People in the RBD group were more than twice as likely as the non-RBD group to have been exposed to pesticides at work.
There was no association, however, between pesticide use outside of work and having RBD, probably because the exposure levels for this group would have been very low, Postuma said.
Postuma and his colleagues found that head injury, which also is a risk factor for both Parkinson's and DLB, was 59 percent more likely in the group with RBD. Less education has been linked to dementia, and the current study found people with RBD had bee
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