Scientists have uncovered a potential link between delayed REM sleep and Alzheimer’s disease.
A new study shows that individuals who take longer to enter the dream phase of sleep may be at higher risk of developing the condition. Researchers found that those with delayed REM sleep had higher levels of toxic proteins associated with Alzheimer’s and lower levels of protective proteins.
Delayed REM Sleep: An Alzheimer’s Warning Sign?
Recent research suggests that both the quality and duration of sleep may play a role in the risk of developing Alzheimer’s disease.
Now, a new study indicates that people who take much longer to enter the dream stage of sleep, known as rapid eye movement (REM) sleep, could be showing an early sign of the disease.
Sleep progresses through three stages of non-REM sleep before reaching REM. Each cycle becomes progressively deeper and takes about 90 minutes or more to complete, depending on a person’s age. Throughout the night, individuals typically go through these cycles four to five times, with older adults generally taking longer to reach REM sleep.
Disrupted REM Sleep and Stress Hormones
REM sleep is crucial for memory processing, particularly for storing emotionally significant experiences into long-term memory.
“The delay in REM sleep disrupts the brain’s ability to consolidate memories by interfering with the process that contributes to learning and memory,” said Yue Leng, PhD, an associate professor in the Department of Psychiatry and Behavioral Sciences at UCSF.
“If it is insufficient or delayed, it may increase the stress hormone cortisol,” said Leng, who is part of the UCSF Weill Institute for Neurosciences. “This can impair the brain’s hippocampus, a critical structure for memory consolidation.”
Leng is a senior author of the paper, published today (January 27) in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
Higher Levels of Amyloid and Tau Proteins
Researchers followed 128 people with an average age of 70 from the neurology unit of the China-Japan Friendship Hospital in Beijing. Half had Alzheimer’s, and about one-third had mild cognitive impairment, a frequent precursor to Alzheimer’s. The rest had normal cognition.
The participants in the study slept overnight in the clinic, so researchers could measure their brainwave activity, eye movement, heart rate, and breathing. Fitness trackers can capture some of this information, but it is less precise.
The researchers divided the participants into early and delayed REM sleep. On average, the early group reached REM less than 98 minutes after falling asleep, while the late group reached it more than 193 minutes after falling asleep.
Those with Alzheimer’s were more likely to have delayed REM sleep, and they also tended to have higher levels of the two toxic proteins, amyloid, and tau, found in people with the condition.
Those with delayed REM sleep had 16% more amyloid and 29% more tau than those with early REM sleep. They also had 39% less of a healthy protein called brain-derived neurotrophic factor (BDNF), which drops in Alzheimer’s.
Medications and Sleep: A Potential Avenue
“Future research should study the effects of certain medications that influence sleep patterns, as these may modify disease progression,” Leng said.
Melatonin can boost REM sleep, and studies in mice have shown that it decreases tau and amyloid accumulation. Other drugs that treat insomnia by blocking a chemical that suppresses REM sleep also have been shown to decrease tau and amyloid.
Tips for Healthy Sleep and Alzheimer’s Prevention
People who are concerned about their risk for Alzheimer’s should practice healthy sleep habits that facilitate the transition from light sleep to REM sleep. “This includes treating conditions like sleep apnea and avoiding heavy drinking, since both can interfere with a healthy sleep cycle,” said Dantao Peng, MD, of the Department of Neurology at the China-Japan Friendship Hospital in Beijing, who is also a senior author of the paper.
“Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor, if they are worried about Alzheimer’s.”
Reference: 27 January 2025, Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
Authors: Co-first authors are Jiangli Jin, MD, of China-Japan Friendship Hospital and the School of Clinical Medicine in Beijing, and Jiong Chen of the Institute of Medical Technology, Peking University Health Science Center. For a complete list of authors, please see the paper.
Funding: Chinese Ministry of Science and Technology (grant # 2021ZD0201902) and the Chinese National Health Commission (grant# 2020ZD10).
