Rapid-eye-movement sleep behavior disorder (REMBD) may be an indicator for Alzheimer's, Parkinson's Disease

Researchers at the University of Toronto say a sleep disorder that causes people to act out their dreams is the best current predictor of brain diseases like Parkinson's and Alzheimer's.
According to an article in Trends in Neurosciences, John Peever, MD, associate professor at the University of Toronto suggests the link occurs because brain degeneration attacks the brain circuits controlling REM sleep before it attacks those areas involved in Parkinson’s, Alzheimer’s, and other neurodegenerative conditions.

Sleep occurs in five distinct phases; the the fifth stage is REM, the the most active sleep phase in which you’re most likely to dream. The REM stage is also when you may find yourself twitching or tossing.
During normal REM sleep your brain temporarily paralyzes your muscles, but in people with REM sleep behavior disorder (REMBD) this paralysis ceases to occur; they may act out their dreams, resulting in injury to themselves and/or their bed partner.

The new research examines the idea that neurodegeneration might first affect areas of the brain that control sleep before attacking brain areas that cause more common brain diseases like Alzheimer’s. REMBD is most common in older men – 90 percent of people who develop it are male, and most are over the age of 50. Scientists already knew REMBD was associated with certain brain disorders including Parkinson’s: previous research has shown that approximately 30 percent of people diagnosed with REMBD will develop Parkinson’s within three years. However, the new study suggests that  80 to 90 percent of people who develop REM sleep behavior disorder will develop degenerative brain disease within the near future.

Medications are available for many of these conditions that can delay or slow progression of the disease when taken early enough, so REMBD could serve as an alert to do so. Once you’re diagnosed with REMBD the usual treatment is a muscle relaxant such as clonazepam (Clomid or Klonopin). However this new research suggests it’s a good idea for anyone diagnosed with REMBD to have a complete workup for Parkinson’s, Alzheimer’s, dementia, and other brain disorders.

Dr. Peever suggests that “...It’s important for clinicians to recognize RBD as a potential indication of brain disease in order to diagnose patients at an earlier stage. This is important because drugs that reduce neurodegeneration could be used in RBD patients to prevent (or protect) them from developing more severe degenerative disorders.”

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References:

Breakdown in REM sleep circuitry underlies REM sleep behavior disorder (Abstract; Trends in Neuroscience, 03/04/2014
Specific Sleep Disorder Associated with Brain Diseases: Psyche Central