Cigarette smoking, head injury, farming, pesticide exposure, and a lower level of education may be risk factors for idiopathic rapid eye movement (REM) sleep behavior disorder (RBD), researchers report. They also note that, despite RBD being a prediagnostic marker of parkinsonism and dementia, they found some important differences in risk factors.
"Until now we didn't know much about the risk factors for this disorder, except that it was more common in men and in older people," said lead author Ronald Postuma, from McGill University in Montreal, Canada, in a press statement.
"Because it is a rare disorder, it was difficult to gather information about enough patients for a full study. For this study, we worked with 13 institutions in 10 countries to get a full picture of the disorder."
The 347 patients with RBD were 43% more likely than 347 individuals without RBD to have ever smoked and 41% more likely to be regular smokers. They were also 59% more likely to have suffered a head injury resulting in unconsciousness.
Education and occupation affected RBD risk as well, with RBD cases having fewer years of education than individuals without the disorder, at 11.1 years versus 12.7 years. Farming as an occupation was 67% more common among RBD patients than controls and RBD patients were more than twice as likely to have been exposed to pesticides through work.
Postuma and team note in Neurology that in addition to being risk factors for RBD, head injury, occupational pesticide exposure, and farming have all previously been linked to Parkinson's disease. Conversely, however, while abstaining from caffeine has proved protective against Parkinson's disease it had no affect on the risk for RBD. Similarly, smoking has had a protective effect in studies of Parkinson's disease but was found to be a risk factor for RBD.
This suggests that, "within established neurodegenerative diseases, RBD may mark a unique subtype that may differ in pathophysiology and risk factors," the team concludes. - Lucy Piper