A new study has found that there is a correlation between an extreme form of sleep disorder, REM Behavior Disorder (RBD), and eventual onset of dementia or parkinsonism.
Patients with RBD have a high probability of later developing Lewy body dementia, Parkinson's disease or multiple system atrophy, because all of these conditions appear to stem from a similar neurodegenerative origin.
The study was conducted by a team of researchers led by Bradley Boeve at Mayo Clinic.
Earlier studies have associated the sleep disorder with eventual onset of Parkinson's disease or Parkinson's disease-like disorder in some patients. This study builds on that work and makes the connection to onset of a non-Alzheimer's dementia.
As part of this study, researchers examined individuals, usually older males who strike out violently, often yelling, when they entered REM sleep, over many years.
Researchers found that many of them develop symptoms of dementia.
Post-mortems showed that they all had developed Lewy bodies but not the pathology of Alzheimer's disease.
However, violent movements during sleep do not always mean someone has this condition. Sometimes the behavior is due to untreated sleep apnea and the condition resolves with regular sleep apnea treatment, by the use of a CPAP breathing machine. In those cases, the cause is sleep apnea.
"This association may provide one of the earliest indicators thus far of eventual dementia or parkinsonism. While some patients don't exhibit symptoms of dementia, all patients we have seen with RBD do develop the pathology." Boeve said.
While Lewy body dementia and Parkinson's disease have no cure, they can be treated. Unlike Alzheimer's disease, medications can restore cognitive function for many with Lewy body dementia.
The quandary facing physicians is whether to inform patients that they have an increased risk of developing dementia or parkinsonism, when symptoms may not appear for years or may never appear at all.
"It's an ethical dilemma. We know that many patients with RBD will develop dementia or parkinsonism, but we can't positively predict what will happen in each individual case. Some physicians choose to tell very little of this to their patients. I try to explain this, but also emphasize the positive -- that some people never show any symptoms and live a normal life. There are documented cases of patients who have had RBD for decades and die from heart disease, stroke or cancer, and never show any signs of dementia or parkinsonism." Boeve said.
The findings of the study are published online in the journal Brain.