Commentary: A little-understood sleep disorder affects millions and has clear links to dementia — 4 questions answered

A little-known and poorly understood sleep disorder that occurs during the rapid eye movement, or REM, stage of sleep has been garnering attention for its role in foreshadowing neurodegenerative brain diseases such as Parkinson’s disease and dementia with Lewy bodies. The disorder, known as REM sleep behaviour disorder, or RBD in the medical field, affects around 1 per cent of the general population worldwide and about 2 per cent of adults over 65.