Iranzo A et al. (2006) Rapid-eye-movement sleep behaviour disorder as an early marker for a neurodegenerative disorder: a descriptive study. Lancet Neurol 5: 572–577

Rapid eye movement (REM) sleep behavior disorder (RBD) is a condition in which patients act out their unpleasant dreams and experience a loss of the normal muscle atonia associated with REM sleep. Evidence indicates that RBD can be the first manifestation of a neurodegenerative disease in some patients, sometimes preceding the neurodegenerative disease by years.

In a recent descriptive study conducted in Spain, researchers retrospectively assessed the records of 44 patients (39 male, 5 female; mean age 74 years) who attended their sleep clinic and had been diagnosed with idiopathic RBD. All patients had received at least 2 years of clinical follow-up involving assessments every 3–12 months by both sleep and neurodegenerative experts, which included neurological examinations, neuropsychological testing and parkinsonism rating scales.

After a mean of 5.1 years of follow-up from the time of diagnosis of idiopathic RBD, 20 patients were found to have developed a neurological disorder: nine patients developed Parkinson's disease, six patients developed dementia with Lewy bodies, four developed mild cognitive impairment, and one developed multiple system atrophy with predominant cerebellar syndrome. The mean duration from the time of the reported onset of RBD to development of the neurological disease was 11.5 years.

The authors conclude that patients diagnosed with idiopathic RBD should be closely monitored for the development of neurodegenerative disease, as early detection and symptomatic treatment might improve their long-term outcome.