Extreme sleep disorder may herald dementia or Parkinson's disease

24 May 2007
NEW DELHI, INDIA

A correlation has been found between REM Behavior Disorder (RBD), an extreme form of sleep disorder, and eventual beginning of dementia or parkinsonism.

Patients with RBD, a new study has showed, have a high probability of developing Lewy body dementia later, Parkinson’s disease or multiple system atrophy – since all of these conditions seem to originate from a similar neurodegenerative origin.

The study, published online in the journal Brain, was conducted by a team of researchers led by Bradley Boeve at Mayo Clinic.

Earlier studies have associated the sleep disorder with eventual onset of Parkinson’s disease or Parkinson’s disease-like disorder in some patients. The new study builds on that work and makes the connection to onset of a non-Alzheimer’s dementia.

As a part of the Mayo Clinic study, researchers examined individuals, usually older males who strike out violently, often yelling, when they entered REM sleep, over many years. It was found that many of them develop symptoms of dementia.

Post-mortems showed that they all had developed Lewy bodies but not the pathology of Alzheimer’s disease.

Violent movements during sleep, however, do not always mean that a person has this condition. Sometimes the behavior could be because of untreated sleep apnea, in which case the condition can be resolved with regular treatment for sleep apnea.

The correlation between REM Behavior Disorder and the eventual onset of dementia or parkinsonism, says Bradley Boeve, may provide one of the earliest indicators thus far of eventual dementia or parkinsonism. While some patients do not exhibit symptoms of dementia, all patients we have seen with RBD do develop the pathology.

Though Lewy body dementia and Parkinson’s disease have no cure, they can be treated. Unlike Alzheimer’s disease, medications can restore cognitive function for many with Lewy body dementia.

The dilemma that the physicians face is whether to inform patients that they have an increased risk of developing dementia or parkinsonism, when symptoms may not appear for years or may never appear at all.

The dilemma is an ethical one, says Bradley Boeve. He adds: “We know that many patients with RBD will develop dementia or parkinsonism, but we can’t positively predict what will happen in each individual case. Some physicians choose to tell very little of this to their patients. I try to explain this, but also emphasise the positive – that some people never show any symptoms and live a normal life. There are documented cases of patients who have had RBD for decades and die from heart disease, stroke or cancer, and never show any signs of dementia or parkinsonism.”