Some people who act out their dreams, screaming, laughing and even getting violent during sleep, may develop dementia in later life, a new study warns.
Isolated REM sleep behaviour disorder (iRBD) affects up to 2 per cent of older adults, and the condition is characterised by the loss of normal muscle paralysis when people dream. Rapid eye movement (REM) is the stage of sleep characterised by increased brain activity, limited muscle movement, darting eye movement, and fluctuating respiration and heart rate.
People with iRBD may yell, laugh, grab, or jump from bed while asleep and even violently kick or punch their bed partners.
The long-term trajectory of the condition and cognitive changes associated with it, however, remain unclear.
The new study observed people who received an iRBD diagnosis in Seoul, South Korea, for about seven years and assessed their cognitive changes over time.
Researchers from the Seoul National University Bundang Hospital tracked as many as 162 iRBD patients, with a mean age at diagnosis of 66 years, analysing them on 320 neuropsychological parameters. They found statistically significant linear decline in memory.
A marked change was seen in the digit symbol test, used to measure processing speed, sustained attention and working memory. The test, the study points out, is sensitive to brain damage, dementia, age, and depression.
Researchers also found consistent deterioration in verbal and visual memory across participants.
“Gradual cognitive decline in attention/working memory and memory may represent a natural course of neuro-degeneration in men with iRBD,” said the study published in the journal Sleep.
Thirty three of the participants did not develop neurodegenerative diseases during the study period, but even they showed cognitive decline. This suggests that even people who manage iRBD for long periods without the condition progressing to dementia or Parkinson’s may experience gradual cognitive loss.
The study also found that cognitive decline was comparatively more gradual in women than men.
“Women with iRBD appeared to show greater resilience to cognitive decline compared to men,” the study said.
The findings, researchers say, emphasise the need to develop sex-specific approaches for monitoring cognitive decline in iRBD patients.
They hope future studies can help explain the mechanisms underlying the differences.
“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,” they said.
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