This sleep habit could be an early sign of dementia, scientists warn

A team of scientists have warned that a sleep habit which affects around two percent of older adults might be an early warning sign of dementia.

Researchers from the Seoul National University Bundang Hospital identified Isolated REM Sleep Behaviour Disorder (iRBD) as a possible factor for developing dementia later in life.

While rare, iRBD is a condition where a person will physically and vocally act out their dreams which typically occur during rapid eye movement (REM) sleep.

REM sleep is the part of sleep where there's more brain activity, less movement and your eyes will be moving around beneath the lids as you dream, it is a vitally important part of your nightly rest.

However, it's also a time where your arm and leg muscles are typically paralysed so while your eyes are moving about your limbs aren't.

REM sleep is where your limbs don't move and you start dreaming, but some people have a condition where their sleeping body acts out the dream (Getty Stock Photo)

But for people with iRBD they will make noises or move around during REM sleep to the point where they might shout, laugh or even jump out of bed because of their movements.

It can also be dangerous to people sharing a bed with them as they might get punched or kicked in their sleep from their partner's unconscious limb movements.

Now a team of scientists studying 162 people with iRBD who underwent 318 neuropsychological assessments have warned that they found 'significant linear declines were observed across attention/working memory and memory domains'.

Tests which measured the effectiveness of a person's memory and their brain processing speed found that people with iRBD displayed a downward trend in their cognitive abilities.

The average age of someone with an iRBD diagnosis was 65, and they were monitored for an average of over seven years as the scientists measured a 'gradual cognitive decline'.

A study has found that people with iRBD experience steady cognitive decline and possibly dementia (Getty Stock Photo)

There was a bit of a gender gap in their observed results, as they found men were experiencing 'significant declines in attention/working memory and memory' while women had 'a more restricted decline'.

They said: "This study, overcoming prior limitations of short follow-up and small samples, provides long-term data demonstrating a gradual decline in attention/working memory and memory domains among people with iRBD."

Studies show that around half of people suffering from Parkinson's disease also have iRBD, along with 80 percent of people with Lewy body dementia and almost all people with muscular system atrophy (MSA).

iRBD often appears years before the onset of the disorder according to one study: in up to 50 percent of cases for MSA, 25 percent of cases for Parkinson's and between 70 and 100 percent of cases for Lewy body dementia.

Many with it will not know they have it because they'll be asleep at a time when symptoms present themselves, but particularly vivid dreams, unexplained injuries and falling out of bed are warning signs.

Sharing your bed with someone is the most effective means of spotting the symptoms as they're more likely to spot it than you are.