Clinical implication of REM sleep behavior disorder in Parkinson's disease.

REM sleep behavior disorder (RBD) appears to have a predilection for some neurodegenerative disorders, especially synucleinopathies such as Parkinson's disease (PD), dementia with Lewy bodies and multiple system atrophy. The frequency of RBD in PD has been reported to variably range from 20 to 72%. RBD may precede or follow onset of parkinsonism. Idiopathic RBD may foreshadow neurodegenerative diseases, and RBD in patients with PD has several associated clinical factors although their causal or temporal relationships are not known. RBD may be associated with the development of hallucinations and dementia in PD. It has been reported that the male gender, old age, a non-tremor motor subtype, a more severe parkinsonism, fall, longer disease duration, autonomic dysfunction, and higher levodopa doses are factors associated with RBD in PD. This review will address the clinical implications of RBD as a preclinical marker of neurodegenerative diseases and PD phenotypes associated with RBD.