Alzheimer's Scientists Reveal New Early Warning Sign

Taking too long to enter the phase of sleep in which we dream may be an early sign of Alzheimer's disease. This is the conclusion of an international team of researchers who studied the sleep patterns of around 100 patients with either Alzheimer's or its precursor in comparison with their cognitively healthy counterparts. The last of four phases of increasingly deep sleep that we cycle through many times each night, "rapid eye movement" (REM) is when we dream and when the brain processes memories and files them away for long-term recall. As people grow older, it typically takes them longer to enter REM sleep. "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 epidemiologist professor Yue Leng of the University of California, San Francisco, in a statement. "If it is insufficient or delayed, it may increase the stress hormone cortisol. This can impair the brain's hippocampus, a critical structure for memory consolidation."

In their study, Leng and her colleagues recruited 128 patients—with an average age of 70—from the neurology clinic of the China–Japan Friendship Hospital in Beijing. Of the subjects, half had Alzheimer's disease, while around a third had a common Alzheimer's precursor: mild cognitive impairment. The remainder had normal cognition. The researchers had all the participants spend a night sleeping in the clinic, during which the scientists recorded the patients' brainwave activity, breathing, eye movements and heart rate. Based on their observations, the team divided the subjects into groups based on when they entered the REM phase of sleep. Those in the "early" group typically achieved REM within 98 minutes of falling asleep, while the "late" group took more than 193 minutes.

The researchers found that the subjects with Alzheimer's were significantly more likely to experience a delay in the onset of REM sleep—alongside having higher levels of the toxic amyloid and tau proteins associated with the condition. In fact, the team reported that patients with delayed REM onset had 29 percent more tau and 16 percent more amyloid proteins than those who reach REM early, as well as 39 percent less of a healthy protein known to decrease with Alzheimer's—brain-derived neurotrophic factor, or BDNF for short. "Future research should study the effects of certain medications that influence sleep patterns, as these may modify disease progression," Leng said. Melatonin, for example, is known to increase REM sleep—and has been linked, in mice models, to a reduction in harmful amyloid and tau aggregation.

How To Sleep To Reduce Alzheimer's Risk

The researchers advise people who are concerned about their own risk of Alzheimer's to practice healthy sleep habits that can help ease the transition from light into REM sleep. "This includes treating conditions like sleep apnea and avoiding heavy drinking, since both can interfere with a healthy sleep cycle," said paper author and neurologist Dr. Dantao Peng of the China–Japan Friendship Hospital in a statement. She added: "Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor, if they are worried about Alzheimer's." Do you have a tip on a health story that Newsweek should be covering? Do you have a question about Alzheimer's disease? Let us know via science@newsweek.com.

Reference

Jin, J., Chen, J., Cavaillès, C., Yaffe, K., Winer, J., Stankeviciute, L., Lucey, B. P., Zhou, X., Gao, S., Peng, D., & Leng, Y. (2025). Association of rapid eye movement sleep latency with multimodal biomarkers of Alzheimer's disease. Alzheimer's & Dementia. https://doi.org/10.1002/alz.14495