Delayed emergence of a parkinsonian disorder or dementia in 81% of older men initially diagnosed with idiopathic rapid eye movement sleep behavior disorder: A 16-year update on a previously reported series

Objective: To provide a 16-year update from the authors' 1996 report documenting a 38% conversion from idiopathic rapid eye movement sleep behavior disorder (iRBD) to a parkinsonian disorder at a mean interval of nearly 13. years after the onset of iRBD in a series of 29 males ≥50. years old. Methods: The methods of evaluation, diagnosis and follow-up were previously described in the 1996 report. All patients had video-polysomnography (vPSG) confirmed RBD. Results: 80.8% (21/26) of patients who were initially diagnosed with iRBD eventually developed parkinsonism/dementia (three of the original 29 patients were lost to follow-up). The distribution of diagnoses was as follows: n = 13, Parkinson's disease (PD); n = 3, dementia with Lewy bodies (DLB); n = 1, dementia (unspecified; profound); n = 2, multiple system atrophy (MSA); n = 2, clinically diagnosed Alzheimer's Disease (AD) with autopsy-confirmed combined AD plus Lewy body disease pathology. Among the 21 iRBD "converters," the mean age (±SD) of iRBD onset was 57.7 ± 7.7. years; mean age (±SD) of parkinsonism/dementia onset was 71.9 ± 6.6. years; and mean interval (±SD) from iRBD onset to parkinsonism/dementia onset was 14.2 ± 6.2. years (range: 5-29. years). Conclusion: The vast majority of men ≥50. years old initially diagnosed with iRBD in this study eventually developed a parkinsonian disorder/dementia, often after a prolonged interval from onset of iRBD, with the mean interval being 14. years while the range extended to 29. years. Also, the specificity of iRBD converting to parkinsonism/dementia is striking. These findings carry important clinical and research implications in the convergent fields of sleep medicine, neurology, and neuroscience, and identify an optimal clinical group for conducting prospective research studies utilizing putative neuroprotective agents to delay the emergence of, or halt the progression to, parkinsonism and/or cognitive impairment as manifestations of either PD, DLB or MSA.