"Some people tell us that their wedding night -- that was the first time couples slept together back in those days" -- was the first indication of a problem, Boeve said. "Wives would report 'I got punched. I didn't know what I would be enduring for decades to come.'"
Boeve and his co-authors reviewed Mayo Clinic records to identify 27 patients who had RBD and went on to develop Parkinson's, dementia with Lewy bodies or multiple system atrophy, all neurodegenerative diseases, 15 or more years later.
Thirteen of the patients were diagnosed with dementia, another 13 with Parkinson's and one with multiple system atrophy.
Among the entire database of hundreds of patients (this included people with shorter intervals between the two diagnoses), only one with the sleep disorder had autopsy-confirmed Alzheimer's, Boeve said.
The average time elapsing between RBD and one of the other diseases was 25 years, the researchers found.
Eighty-nine percent of the patients in the sample were men, although it's not clear why, as neurological disorders affect both genders, noted the authors of an accompanying editorial.
Boeve cautions that "not everybody that acts out dreams at night has RBD." They may have another sleep disorder producing similar symptoms, he said.
And it's unlikely that everyone with RBD will go on to develop Parkinson's or a kindred disorder, if they live long enough, he said.
The new findings, while informative, aren't enough by themselves to make a difference in patients' lives, experts said.
Dr. Carlos Singer, professor of neurology at the University of Miami Miller School of Medicine, said clinicians won't be able to identify candidates for early intervention "unless we find another clue how to distinguish [those who do progress and those who don't] at an early stage."
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