The first warning of Parkinson's disease may be the experience of nightmares during sleep,scientists have revealed.
Experts have found that people who suffer from a condition known as 'REM sleep disturbance' - which includes nightmares and sudden kicking movements - are more likely to develop Parkinson's and other forms of dementia, reports the Daily Mail.
Normal sleepers are effectively paralysed during REM or rapid eye movement because the brain shuts off the muscles allowing the body to properly rest.
But this doesn't happen to those with REM disorders, who often act out their dreams with violent movements.
Scientists in Barcelona found that a fifth of those over 60 suffering from the condition went on to develop Parkinson's, and other degenerative diseases such as Lewy body dementia.
The team of researchers led by Alex Iranzo at the Neurology Department of the Hospital Clinic in Barcelona looked at 43 patients over the age of 60 who had all been diagnosed with REM sleep disorders.
They found that 30 per cent had developed some form of neurological disorder two and a half years after their sleeping problem was diagnosed - in most cases Parkinson's.
This latest study backs up American research published earlier this year, which showed that kicking, or lashing out in sleep could be one of the first signs of Parkinson's.
The study was published in the Lancet Neurology journal.