Thrashing about in your sleep may be an early warning sign of Parkinson's and dementia, new research suggests.
Moving around in bed, and seeming to 'act out' dreams is a characteristic of a condition called rapid eye movement sleep behaviour disorder (RBD).
People who suffer from this were shown to have inflammation in the area of the brain where the chemical dopamine is produced, which is involved in sending messages.
Parkinson's and dementia patients are known to have diminished supplies of dopamine because nerve cells that make it have died.
RBD affects around five per cent of people and includes talking, laughing, shouting and swearing while sleeping.
It adds to research published two years ago which discovered about half of people with RBD will develop Parkinson's disease or another neurological disorder within a decade of being diagnosed.
Thrashing about in your sleep may be an early warning sign of Parkinson's and dementia, research suggests (stock image)
An estimated seven to 10 million people worldwide are living with Parkinson's disease – one million Americans and 127,000 people in the UK.
Dementia affects 850,000 the UK and 5.4 million in US – figures expected to rise substantially to place huge pressures on health and social care services.
For most people, dreaming is purely a 'mental' activity: dreams occur in the mind while the body is at rest.
But people who suffer from REM behavior disorder (RBD) act out their dreams.
They physically move limbs or even get up and engage in activities associated with waking. Some engage in sleep talking, shouting, screaming, hittting or punching.
Some even jump out of bed while sleeping.