Camilla Jessen
Acting out dreams linked to later cognitive decline.
Researchers from Seoul National University Bundang Hospital focused on a condition called Isolated REM Sleep Behaviour Disorder, or iRBD. It affects an estimated two percent of older adults.
iRBD causes people to physically act out their dreams during rapid eye movement, or REM, sleep. This is the stage of sleep when dreaming is most intense and brain activity is high.
Normally, the body’s muscles are temporarily paralysed during REM sleep, preventing movement. In people with iRBD, that paralysis fails, allowing them to shout, laugh, flail their arms, or even jump out of bed while asleep.
Risks during sleep
The condition can also pose a risk to bed partners, who may be accidentally hit or kicked during the night. Because symptoms occur during sleep, many people with iRBD are unaware they have the disorder.
Warning signs can include vivid dreams, unexplained bruises or injuries, and falling out of bed. Often, it is a partner who first notices the behaviour.
Cognitive decline observed
The research team studied 162 people diagnosed with iRBD, who underwent a total of 318 neuropsychological assessments. Participants were monitored for an average of more than seven years, with an average age of 65 at diagnosis.
The scientists reported “significant linear declines” in attention, working memory, and memory over time. Tests measuring memory and brain processing speed showed a steady downward trend in cognitive performance.
Men in the study showed notable declines in attention, working memory, and memory. Women also experienced decline, though it was described as more limited.
Link to neurodegenerative disease
The researchers said their findings strengthen evidence that iRBD may be an early indicator of neurodegenerative disorders.
Previous studies show that around half of people with Parkinson’s disease have iRBD. The condition is also present in about 80 percent of people with Lewy body dementia and nearly all people with multiple system atrophy.
iRBD can appear years before these conditions develop. It is seen in up to 50 percent of multiple system atrophy cases, 25 percent of Parkinson’s cases, and between 70 and 100 percent of Lewy body dementia cases.
Why awareness matters
The researchers said their study provides long-term data showing gradual cognitive decline in people with iRBD. They stressed that recognising symptoms early may help identify those at higher risk of developing dementia-related conditions.
Because many people are unaware they have iRBD, experts say awareness, particularly among partners and family members, is key.
Sources: Seoul National University Bundang Hospital, World Health Organisation, LadBible
