New research suggests that people who take longer to enter the dream phase of sleep, known as rapid eye movement (REM) sleep, may face a greater risk of developing dementia, including Alzheimer’s disease.
Scientists have found that delayed REM sleep disrupts critical brain functions, such as memory consolidation and emotional regulation.
The study, conducted by researchers at the University of California, San Francisco (UCSF), and the China-Japan Friendship Hospital in Beijing, emphasizes the potential role of sleep quality as an early indicator of neurodegenerative conditions.
REM sleep is the stage of the sleep cycle when dreaming typically occurs. It follows three phases of non-REM sleep, each progressively deeper than the last. On average, it takes about 90 minutes for an individual to reach REM sleep, though the duration may vary depending on age.
During REM sleep, the brain processes emotionally charged memories and transfers them to long-term storage. The body also produces melatonin during this phase, which is believed to help clear out toxic proteins associated with brain damage, such as amyloid and tau.
Researchers monitored the sleep patterns of 128 participants aged around 70, including individuals with Alzheimer’s, mild cognitive impairment, and normal cognitive function. The participants underwent overnight sleep monitoring to track brainwave activity, heart rate, breathing, and eye movement.
The study divided participants into two groups based on the time it took to reach REM sleep:
- Early REM group: Less than 98 minutes after falling asleep
- Delayed REM group: More than 193 minutes after falling asleep
Participants in the delayed REM group were more likely to have Alzheimer’s disease and showed higher levels of the toxic proteins amyloid (16% more) and tau (29% more) compared to those in the early REM group. Additionally, the delayed group had lower levels of brain-derived neurotrophic factor (BDNF), a protein essential for healthy brain function.
“The delay in REM sleep disrupts the brain’s ability to consolidate memories by interfering with the processes that contribute to learning and memory,” said Dr. Yue Leng, co-senior author of the study. “If REM sleep is insufficient or delayed, it may increase the stress hormone cortisol, which can impair the hippocampus—a critical structure for memory consolidation.”
Dr. Leng added that certain medications, such as melatonin and drugs that block chemicals suppressing REM sleep, have been found to reduce the accumulation of tau and amyloid in previous studies on mice.
Researchers suggest that individuals concerned about their dementia risk should adopt sleep habits that facilitate a smooth transition from light sleep to REM sleep. These recommendations include:
- Treating conditions like sleep apnea: Sleep disruptions can hinder REM sleep.
- Avoiding heavy drinking: Alcohol is known to suppress REM sleep.
- Medication review: Patients on antidepressants or sedatives that reduce REM sleep should discuss their concerns with their healthcare provider.
With input from New York Post and the Daily Mail.
