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Sleep disorder may signal dementia

Sleep disorder may signal dementia Linked to unsettled REM sleep

A type of sleep disorder may be a warning sign of future dementia, a study has found.

US researchers found that people with rapid eye movement sleep behaviour disorder (RBD) are at greater risk of developing Parkinson's disease and other neurological conditions.

People who experience RBD unconsciously act out their dreams during the REM stage sleep. This can involve shouting, kicking, thrashing and even jumping out of bed and in some cases causing injury to themselves.

Normally during REM sleep, the body's muscles are deeply relaxed to the point of paralysis while the brain actively dreams, but in people with RBD, little or no muscle relaxation occurs.

US researchers looked at the medical records of 27 people with three neurodegenerative conditions who also experienced RBD earlier in life.

They found that 63 per cent of those who experienced RBD developed Lewy body dementia or Parkinson’s disease in later life.

The time between the start of the sleep disorder and the symptoms of dementia averaged 25 years. But in some cases, the disorder was detected up to 50 years before disease symptoms developed.

The research confirms past studies which identified a link between sleep disorder and Lewy body dementia, which makes up four per cent of all dementia cases in the UK.

It is characterised by certain symptoms that are also present in people with both Parkinson’s and Alzheimer’s disease.

Lead author Dr Bradley Boeve of the Mayo Clinic in Rochester, Minnesota, said: "Our findings suggest that in some patients, these conditions have a very long life span of activity within the brain and they may also have a long period of time where other symptoms aren't apparent."

Ruth Sutherland, acting chief executive of the Alzheimer’s Society, said: "This research improves our understanding of how Lewy body dementia develops and how it might be linked to sleep disorders early in life.

"However we don’t yet understand why this correlation exists, and given the small sample size of this study, more research is needed."

The findings are published online in the journal Neurology.

This article was published on Thu 29 July 2010

Image © Karen Roach - Fotolia.com

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