Middle-aged men who move around, walk, talk and hit out while sleeping are five times more likely to develop dementia, a study has found.
Researchers at the Mayo Clinic in the US said men physically acting out their dreams can be a sign that they are developing the Lewy bodies which make up the second most common form of dementia.
Acting out dreams physically is known as rapid eye movement (REM) sleep behaviour disorder study suggests it can be a precursor up to 30 years before a full diagnosis of dementia is made.
The study involved taking magnetic resonance imaging (MRI) scans of the brains of 75 people diagnosed with probable dementia. The medical records of those patients were then checked to see if they had been diagnosed with the sleep disorder in earlier life.
Dr Melissa Murray, a neuroscientist at Mayo Clinic, said that while not everyone who has sleep disorders develops dementia, 75 to 80 per cent of the men studied were found have experienced REM sleep behaviour disorder.
The researchers found no link to sleep disorders and dementia in women.
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