Sleeping disorders may act as an early indicator of neurodegenerative diseases like Parkinson's disease and Lewy body dementia (LBD) -- a type of dementia, according to a study.

The study focused on patients with Rapid eye movement behaviour disorder -- a sleep disorder where individuals physically act out their dreams during the rapid eye movement (REM) stage of sleep.

"Normally, when we're asleep and dreaming, our muscles are paralysed, but around age 50, some people become very agitated during sleep and start punching, kicking and screaming," said Shady Rahayel, a medical professor at Université de Montréal in Canada.