Sleep Disorder Could Signal Early Dementia Risk, Study Finds
Scientists have issued a warning that a specific sleep habit could serve as an early indicator of dementia, with new research highlighting significant gender differences in how cognitive decline progresses. The study, conducted over seven years, provides crucial long-term data on the connection between sleep disturbances and neurodegenerative diseases.
Understanding Isolated REM Sleep Behaviour Disorder
Isolated REM sleep behaviour disorder (iRBD) affects approximately 2 per cent of older adults and involves the loss of normal muscle paralysis during dreaming. During rapid eye movement (REM) sleep – characterised by increased brain activity, limited muscle movement, darting eye movements, and fluctuating respiration and heart rate – individuals with iRBD may exhibit unusual behaviours.
These can include yelling, laughing, grabbing, or even jumping from bed while asleep, with some patients violently kicking or punching their bed partners during dream states. The condition has long been associated with increased risk of developing neurodegenerative diseases, but the long-term trajectory remained unclear until this comprehensive study.
Seven-Year Study Reveals Cognitive Decline Patterns
Researchers from Seoul National University Bundang Hospital in South Korea tracked 162 iRBD patients with a mean diagnosis age of 66 years, analysing them across 320 neuropsychological parameters. The study, published in the journal Sleep, found statistically significant linear decline in memory functions among participants.
A particularly marked change was observed in the digit symbol test, which measures processing speed, sustained attention, and working memory. This test is known to be sensitive to brain damage, dementia, age, and depression. Researchers documented consistent deterioration in both verbal and visual memory across study participants.
"Gradual cognitive decline in attention/working memory and memory may represent a natural course of neuro-degeneration in men with iRBD," the study concluded.
Surprising Findings About Disease Progression
Perhaps most surprisingly, 33 participants who did not develop neurodegenerative diseases during the study period still showed measurable cognitive decline. This suggests that even individuals who manage iRBD for extended periods without progressing to dementia or Parkinson's disease may experience gradual cognitive loss.
The research indicates that iRBD might represent an early marker of neurodegenerative processes that can occur independently of full disease manifestation, highlighting the importance of monitoring cognitive function in all iRBD patients regardless of whether they develop overt neurological conditions.
Gender Differences in Cognitive Resilience
One of the study's most significant findings concerns gender differences in how cognitive decline manifests. Researchers discovered that cognitive decline was comparatively more gradual in women than in men with the same condition.
"Women with iRBD appeared to show greater resilience to cognitive decline compared to men," the study reported, suggesting potential biological or hormonal factors that might offer some protection against neurodegenerative processes.
Implications for Future Treatment and Monitoring
The findings emphasise the urgent need to develop sex-specific approaches for monitoring cognitive decline in iRBD patients. Researchers hope future studies will help explain the mechanisms underlying these gender differences, potentially leading to more targeted interventions and treatment strategies.
"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," the researchers noted, highlighting the importance of their extended observation period and comprehensive assessment methods.
The research adds to growing evidence about the connection between sleep disorders and cognitive health, suggesting that monitoring sleep patterns in older adults could provide valuable early warnings about potential neurodegenerative risks.
