New research suggests that how quickly a person enters REM sleep&mdash;the dream phase of sleep&mdash;could be an early indicator of Alzheimer&rsquo;s disease. The <a href="https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.14495">study</a>, published in Alzheimer&rsquo;s &amp; Dementia: The Journal of the Alzheimer&rsquo;s Association, found that individuals who take longer to reach REM sleep tend to have higher levels of toxic proteins linked to Alzheimer&rsquo;s and lower levels of protective proteins.
The Link Between Sleep and Alzheimer&rsquo;s
Sleep progresses through three stages before reaching REM, the phase critical for memory processing. Typically, a full sleep cycle takes about 90 minutes, repeating multiple times throughout the night. However, older adults often take longer to reach REM sleep.
The study followed 128 participants, with an average age of 70, at the China-Japan Friendship Hospital in Beijing. Half had Alzheimer&rsquo;s, while others had mild cognitive impairment or normal cognition. Researchers monitored their sleep patterns overnight, analysing brainwave activity, eye movement, heart rate, and breathing.
Participants were divided into two groups: those who reached REM in less than 98 minutes and those who took more than 193 minutes. Those in the delayed REM group showed significantly higher levels of amyloid and tau proteins&mdash;hallmarks of Alzheimer&rsquo;s&mdash;compared to those with earlier REM onset. They also had lower levels of brain-derived neurotrophic factor (BDNF), a protein essential for brain health.
The Role of Stress and Medications
According to study co-author Yue Leng, PhD, of the UCSF Weill Institute for Neurosciences, a delay in REM sleep may disrupt memory consolidation and increase levels of cortisol, a stress hormone that can impair the hippocampus, a key brain region for memory.
The findings also raise questions about medications that affect sleep. Some antidepressants and sedatives reduce REM sleep, while melatonin and certain insomnia treatments may enhance it. Researchers suggest that future studies should explore whether sleep-modulating drugs could influence Alzheimer&rsquo;s progression.
Healthy Sleep Habits for Brain Health
For those concerned about Alzheimer&rsquo;s risk, improving sleep quality could be beneficial. Treating conditions like sleep apnea, avoiding heavy alcohol consumption, and discussing medication effects with a doctor may help maintain a healthy sleep cycle, according to 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.
While more research is needed to confirm whether delayed REM sleep directly contributes to Alzheimer&rsquo;s, the study reinforces the growing understanding that sleep health and brain health are deeply connected.

AI representation of an old person's brain during REM

Study finds slower REM sleep onset may signal higher levels of toxic proteins tied to Alzheimer’s

Delayed REM Sleep Linked to Alzheimer’s Risk

Study finds slower REM sleep onset may signal higher levels of toxic proteins tied to Alzheimer’s

January 29, 2025 | 19:49 IST