A good night’s rest is essential for maintaining a healthy brain, and research increasingly suggests that poor sleep can heighten the risk of developing dementia. Among the various stages of sleep, the rapid eye movement (REM) phase plays a particularly crucial role in cognitive function.
New findings indicate that delays in reaching REM sleep may serve as an early symptom of Alzheimer’s disease, highlighting the importance of sleep quality in preventing cognitive decline.
New Findings on Sleep and Alzheimer’s Disease
Recent research has shown that individuals who take longer to enter the REM phase of sleep may be experiencing an early warning sign of Alzheimer’s disease.
“Previous studies have mostly focused on slow wave sleep, or deep sleep, as a risk factor for Alzheimer’s disease,” says senior study author Yue Leng, PhD, an associate professor in the department of psychiatry and behavioral sciences at the University of California in San Francisco.
“This is really the first study to look at how long it takes you to enter REM sleep as a novel mark for Alzheimer’s disease,” she adds.
This groundbreaking study provides new insights into the relationship between sleep and brain health, emphasizing the importance of REM sleep in maintaining cognitive function.
The Link Between Sleep and Brain Health
The REM stage of sleep plays a significant role in processing emotional memories and consolidating information. When there is a delay in entering REM sleep, the brain’s ability to organize and store memories is disrupted.
Dr. Leng and her collaborators found that poor or reduced REM sleep could raise levels of cortisol, a stress hormone that can impair the hippocampus—a critical region of the brain responsible for memory consolidation. This disruption may accelerate cognitive decline, potentially increasing the risk of Alzheimer’s disease over time.
Higher Levels of Toxic Brain Proteins in Individuals with Delayed REM Sleep
To further explore this connection, researchers conducted a study involving 128 adults with an average age of 70 from the neurology unit of the China-Japan Friendship Hospital in Beijing. Half of the participants had Alzheimer’s disease, while one-third had mild cognitive impairment, a common precursor to Alzheimer’s. The remaining individuals exhibited normal cognitive function.
Participants were monitored overnight in a clinical setting, where researchers measured brainwave activity, eye movement, heart rate, and breathing patterns. The data revealed a striking difference between individuals who reached REM sleep early (within 98 minutes) and those who reached REM sleep late (beyond 193 minutes).
Those who experienced delayed REM sleep were found to have higher levels of amyloid and tau—two toxic proteins commonly associated with Alzheimer’s disease. Specifically, subjects with delayed REM sleep had 16 percent more amyloid and 29 percent more tau than those who reached REM sleep earlier.
Additionally, individuals in the late REM group exhibited 39 percent lower levels of brain-derived neurotrophic factor (BDNF), a healthy protein known to support brain function, which decreases in Alzheimer’s patients.
Good Sleep as a Preventative Measure Against Alzheimer’s
For Stefania Forner, PhD, director of medical and scientific relations for the Alzheimer’s Association, these findings reinforce existing evidence that sleep disturbances may influence the risk of developing Alzheimer’s and other neurodegenerative diseases.
“This study may contribute to a better understanding of modifiable risk factors for Alzheimer’s, such as poor sleep,” she says.
“However, replication of these findings in larger and more diverse study populations is needed. The study was conducted in a very controlled environment — inside a clinic — and a real-world data study would be important for a future study,” Dr. Forner explains.
Although further research is necessary to confirm these results in broader populations, the study underscores the importance of addressing sleep issues as a potential strategy for reducing Alzheimer’s risk.
Monitoring and Improving Sleep for Better Brain Health
According to Yuko Hara, PhD, director of aging and Alzheimer’s prevention at the Alzheimer’s Drug Discovery Foundation, most individuals are unable to determine on their own if their REM sleep is delayed. However, wearable technology, such as smartwatches and EEG headsets, can provide estimates of sleep stages, helping individuals track their sleep health.
Even without precise data on REM sleep timing, maintaining good sleep hygiene can help minimize dementia risk. The Alzheimer’s Drug Discovery Foundation and the Alzheimer’s Association recommend the following strategies for improving sleep quality:
- Get seven to eight hours of sleep each night.
- Avoid caffeinated beverages near bedtime.
- Refrain from consuming alcohol several hours before sleep.
- Keep your sleeping environment dark and comfortable.
- Limit exposure to blue light from electronic devices after sunset. “Electronics are a major source of blue light, which promotes wakefulness,” says Hara.
- Seek medical advice if you suspect sleep disorders such as insomnia or sleep apnea.
- Discuss with your doctor any medications that may be disrupting your REM sleep.
“If you don’t get enough sleep or have poor quality sleep, addressing these issues may optimize your sleep cycles and help lower your risk for Alzheimer’s disease,” says Dr. Hara.
Conclusion: The Critical Role of Sleep in Cognitive Health
As the body of research continues to grow, it becomes increasingly clear that sleep plays an essential role in cognitive health.
The new findings on REM sleep and Alzheimer’s disease suggest that delays in reaching REM sleep could be an early warning sign of neurodegenerative decline. By prioritizing sleep hygiene and monitoring sleep health, individuals may be able to take proactive steps to support brain function and reduce the risk of Alzheimer’s.
As future studies explore these connections further, improving sleep habits today remains one of the simplest and most effective ways to protect long-term cognitive well-being.