Mayo Clinic researchers and a group of international collaborators have discovered a correlation between an extreme form of sleep disorder and eventual onset of parkinsonism or dementia.
The findings appear in the current issue of the journal Brain http://brain.oxfordjournals.org/.
Clinical observations and pathology studies, as well as research in animal models, led to the findings that patients with the violent rapid eye movement sleep (REM) behavior disorder (RBD) have a high probability of later developing Lewy body dementia, Parkinson's disease or multiple system atrophy (a Parkinson's-like disorder), because all of these conditions appear to stem from a similar neurodegenerative origin.
"Our data suggest that many patients with idiopathic (not associated with any other neurologic symptoms) RBD may be exhibiting early signs of an evolving neurodegenerative disease, which in most cases appear to be caused by some mishap of the synuclein protein," says Bradley Boeve, M.D., Mayo Clinic neurologist and lead author of the study. Synuclein proteins are associated with synapses in the brain, and clumps of abnormal alpha-synuclein protein are present in some forms of dementia. "The problem does not seem to be present in the synuclein gene itself, but it's something that happens to the protein following gene expression. Just what happens to it to cause the conditions isn?t clear."
The result, however, is quite clear. The patients -- usually older males -- strike out violently, often yelling, when they enter REM sleep. Mayo researchers following these individuals over many years saw many of them develop symptoms of dementia. Postmortems showed they all had developed Lewy bodies but not the pathology of Alzheimer's disease. Earlier studies by two of the co-authors on this paper (from the University of Minnesota) had described this sleep disorder and associated it with eventual onset of Parkinson's disease or Parkinson's disease-like disorder in some patients. This Mayo study builds on that work and makes the connection to onset of a non-Alzheimer's dementia.