REM sleep behavior disorder blocks the paralysis that comes with deep sleep and causes people to violently act out their dreams. As though that's not bad enough, the disorder might mean neurological diseases are in the patient's future.
Researchers examined the full medical records of 27 Mayo Clinic patients who suffered through at least fifteen years of REM sleep behavior disorder. All 27 of them eventually developed a serious neurological disease: 13 developed Parkinson's, 13 were diagnosed with dementia, and the final one developed the Parkinson's-like condition known as multiple system atrophy. The time span between the onset of the sleep disorder and the diagnosis of the later illness averaged at least 25 years, with one patient living 50 years before presenting the first symptoms of the later disease.
So what does this all mean, exactly? Lead researcher Dr. Bradley F. Boeve explains:
"Our findings suggest that in some patients, conditions such as Parkinson's disease or dementia with Lewy bodies have a very long span of activity within the brain and they also may have a long period of time where other symptoms aren't apparent. More research is needed on this possible link so that scientists may be able to develop therapies that would slow down or stop the progression of these disorders years before the symptoms of Parkinson's disease or dementia appear."
Indeed, this finding suggests a link between two sets of diseases that we don't know a lot about, and now may know even less about than we thought. We don't actually know the underlying cause of REM sleep behavior disorder, and it's possible that the same processes that cause these neurological breakdowns decades later might also play a role in preventing the neurotransmitters from shutting off during REM sleep.
Of course, it's important to keep these findings in perspective. The fact that all 27 patients studied later developed a serious degenerative neurological condition is certainly a persuasive argument that the sleep disorder is somehow linked to these more serious diseases, but it can't be considered definitive proof. The researchers readily admit they don't know what percentage of sufferers of REM sleep behavior disorder will eventually develop Parkinson's or Dementia.
Still, even though the sleep disorder is probably not an absolute indicator of later degenerative conditions, it could be a useful early warning system, and finding a link between the two conditions will hopefully allow us to find better treatments for both.