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Poor sleep has been linked to an increased dementia risk, though we don’t yet know exactly how one affects the other.
But roughly 90% of people with the sleep condition known as isolated REM sleep behaviour disorder (iRBD) go on to develop Parkinson’s or Lewy body dementia, according to a study published in Neurology.
The leader of the research team, Professor Shady Rahayel, said iRBD is “not just restless sleep – it’s a neurological warning sign”.
But what is iRBD, and what does the new study show?
What is REM sleep behaviour disorder?
This is a condition where you physically or verbally act out in your sleep.
Its symptoms include thrashing around, shouting, and “sudden, often violent arm and leg movements during REM sleep”. It is also known as “dream-enacting behaviour”.
You might accidentally hit your partner in your sleep, swear while you’re dreaming, or fall out of bed. Per the Cleveland Clinic, about 80% of those with the condition get injured from the actions in their sleep.
Usually, our brain prevents our limbs from moving during our dream cycle. With REM sleep behaviour disorders, though, this doesn’t work.
According to the Mayo Clinic, it can come on gradually and get worse over time.
But the type most heavily linked to Lewy body dementia and Parkinson’s is isolated, or idiopathic, REM sleep disorder.
This issue, which affects about 2% of the population and “commonly presents in males >50 years”, comes with no other obvious neurological conditions – hence why this particular type is described as “isolated”.
Speak to your doctor if you or your partner notice that you’re “acting out” your dreams, especially if you’re injuring yourself or others.
The findings could lead to dementia being spotted sooner in patients
Using MRI scans, the researchers found those with iRBD who saw changes to the amount of free water in the part of their brains responsible for thought and reasoning were eight times more likely to have a type of dementia with Lewy bodies.
“What’s fascinating is that this marker picks up very early changes – even before symptoms emerge,” the study’s lead author, Celine Haddad, said.
And people with iRDB who also had a lower DTI-ALPS index (a MRI-based measuring technique focusing on fluid) in the left hemisphere of the brain were 2.4 times more likely to develop Parkinson’s in the coming years.
This is hopeful news, because the earlier these conditions are spotted, the better it is for scientists and patients, who can access timely treatment and potentially help slow the rate of disease.
“We already knew that isolated REM sleep behaviour disorder is a warning sign for these diseases,” Professor Rahayel explained.
“What we didn’t know was who would develop what. Thanks to these complementary studies, we now have tools to better predict and personalise care.”
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