Quantifying the risk of neurodegenerative disease in idiopathic REM sleep behavior disorder

Postuma RB, Gagnon JF, Vendette M, Fantini ML, Massicotte-Marquez J, Montplaisir J; Neurology 2009; 72 (15); 1296-1300. [Epub 2008 Dec 24]

Commented by Prof Serge Gauthier, 31 May 2009

Aim of the study

To quantify the risk of developing a neurodegenerative condition in patients with REM sleep behavior disorder (RBD).

Method

Follow-up study of all patients seen in a research sleep laboratory between 1989 and 2006 with a diagnosis of idiopathic RBD, excluding patients with signs of neurodegenerative disease at baseline examination.

Parkinson's disease was diagnosed using the UK bank criteria, dementia using a MMSE cut off of <24 with evidence of functional decline, probable Dementia with Lewy Bodies (DLB) using the McKeith criteria as cognitive decline, RBD, and at least one of parkinsonism, visual hallucinations or fluctuations.

The primary outcome measure was the risk of developing parkinsonism or dementia using a life table (Kaplan-Meier) survival analysis.

Results

113 patients have been diagnosed with RBD during the 17 years of data collection; 93 (82.3%) met inclusion criteria. The mean age was 65.4, 80% were men, and they had a mean duration of 7.2 years of RBD symptoms before the sleep study. Of the 93 patients with RBD 26 developed a neurodegenerative disease (14 Idiopathic PD; 1 Multiple System Atrophy; 7 DLB; 4 Alzheimer’s disease). The estimated 5-year risk of developing a neurodegenerative disease was 17.7%, 10-year risk 40.6%, 12-year risk 52.4%.

Professor Gauthier's comments

This is an important confirmation of other studies suggesting an increased risk of parkinsonism and of dementia in patients with idiopathic RBD. The accompanying editorial by TC Britton and KR Chaudhuri (ref. 1) highlights the very high quality of this study and the possibility that RBD may become a prodromal marker of alpha-synucleopathies.

The search for reliable prodromal markers of neurodegenerative conditions is important. For instance in Alzheimer's disease there are a number of mood and behavioral symptoms preceding the diagnosis of dementia (ref. 2). Post-op delirium is increasingly recognized as a prodrome of dementia (ref. 3).

Although the maintenance of a healthy lifestyle is currently the best option with regard to the prevention of dementia (ref. 4), this will change in the near future as evidence is gained on more specific preventive measures for at risk populations identified by prodromal markers such as RBD.