Early RBD linked to severity of nonmotor Parkinson’s symptoms
Patients with sleep behavior disorder saw faster symptom progression
A study found a link between the likely presence of REM sleep behavior disorder (RBD) in people with Parkinson’s disease and greater frequency and severity of other nonmotor symptoms (NMS) that characterize the neurodegenerative disease.
The researchers said the results link RBD to a Parkinson’s subtype called diffuse malignant Parkinson’s, in which symptoms tend to be more severe and progress more quickly than usual. Knowing which patients are at risk for faster NMS progression can help doctors make treatment decisions.
“These NMS profiles may play a critical role in stratifying patients for targeted interventions,” the researchers wrote.
The study, “Clinically probable RBD is an early predictor of malignant non-motor Parkinson’s disease phenotypes,” was published in npj Parkinson’s disease.
Beyond the classic motor symptoms of Parkinson’s, patients experience a range of troublesome symptoms, including mood disorders, cognitive problems, sleep issues, and gastrointestinal disturbances, that can contribute to overall disease severity and progression.
RBD and Parkinson’s
Scientists don’t have a reliable way of predicting which patients will develop more severe NMS. It’s also not clear whether they occur as distinct conditions, or whether they tend to cluster together and co-occur.
RBD is a common NMS in which people act out their dreams during the rapid eye movement (REM) phase of sleep. Normally, the body is basically paralyzed during REM sleep, but in RBD, that paralysis doesn’t happen.
This sleep disorder is often one of the first evident symptoms of Parkinson’s, sometimes appearing years before the onset of motor symptoms that prompt a diagnosis. RBD has been associated with a higher rate of other NMS such as depression and cognitive impairment.
The scientists explored the possible link between RBD and the development of other NMS in Parkinson’s.
They examined clinical data from 452 Parkinson’s patients in the Parkinson’s Progression Markers Initiative (PPMI), a large, long-term study involving people with and without the neurodegenerative disease. Of those 452 patients, 180 (40%) were considered to have probable RBD.
Cognitive function, as assessed by the Montreal Cognitive assessment (MoCA), was similar in those with or without RBD in the first year after diagnosis. But after five years, those in the RBD group had a significantly lower mean MoCA score (reflecting greater cognitive impairment) than those without RBD, and their scores declined at a faster rate.
While there was no significant difference in the proportion of patients considered to have mild cognitive impairments or dementia — in which cognitive problems interfere with daily life — in the first two years after diagnosis, a significantly higher proportion of people in the RBD group were considered to have these problems in the years thereafter.
Overall, early RBD was associated with a faster progression to cognitive impairment.
Findings for other nonmotor symptoms showed similar patterns, with early RBD linked to a higher prevalence and greater severity of NMS such as apathy, hallucinations, depression, anxiety, impulse control disorders, and autonomic dysfunction (problems with the part of the nervous system that controls involuntary functions like bladder function, heart rate, and temperature control).
Overall, “patients with early probable RBD experience the same NMS profile as those without early RBD, but they occur more frequently and with much greater severity,” the researchers wrote.
This pattern is consistent with diffuse malignant Parkinson’s phenotype, a disease profile associated with overall faster and more severe disease progression, the scientists said.
They noted that while natural history studies typically indicate the emergence of NMS like cognitive issues, apathy, and hallucinations about 10 years after motor symptoms appear, these problems were evident within the first five years among this group with early RBD.
This more rapid progression may be related to underlying brain connectivity abnormalities that occur during RBD, they said.
Certain NMS in the study also seemed to be linked. For example, apathy, cognitive impairment, and anxiety strongly co-occurred in those with RBD. The researchers indicated that this could be related to common brain networks involved in the symptoms.
According to the scientists, it’s critical to know which Parkinson’s patients are at a risk of these rapidly progressing symptoms because it can influence disease management and treatment choices. “Using RBD as an early clinical predictor of a malignant non-motor phenotype could impact the long-term management of these patients,” the team concluded.
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