To establish the strength of the connection between the two conditions, the researchers - whose recent findings appear in Brain: A Journal of Neurology - worked with 1,280 people with REM sleep behavior disorder across 24 centers of the International RBD Study Group.
The researchers assessed the participants' motor function, cognitive abilities, and sensory abilities for a number of years. After a 12-year follow-up period, they found that 73.5 percent of the people involved in this study had developed Parkinson's disease.
Moreover, participants who had started experiencing motor function issues in this period had a threefold increase in the risk of developing Parkinson's disease or related conditions, such as dementia with Lewy bodies.
Also at high risk were participants who had developed cognitive impairment or started experiencing problems with their sense of smell.
These findings confirm that the presence of RBD is, indeed, a strong predictor of Parkinson's disease.
All the more so, since the researchers conducted the study in centers across North America, Europe, and Asia, which means that the results apply to diverse populations.