A clear sign of dementia: Researchers have identified an early warning signal from the body indicating the onset of the disease.

Recent studies have indicated that the quality and duration of sleep, particularly during the rapid eye movement (REM) phase, may influence the risk of developing Alzheimer’s disease. With these findings, researchers are hopeful they can predict the onset of this dangerous illness, which affects millions, based on this characteristic. This could ultimately lead to smoother and more effective therapies, as reported by University of California — San Francisco.

The research, published in the journal Alzheimer's and Dementia, identified a potential link between the delay in REM sleep and early signs of Alzheimer’s disease.

REM sleep, the phase during which the brain processes and stores emotionally charged memories, typically occurs after three stages of non-REM sleep. A complete sleep cycle lasts about 90 minutes but can extend with age. Researchers assert that a delay in REM sleep may disrupt memory consolidation and increase cortisol levels, a stress hormone that, in turn, impairs the function of the hippocampus—a crucial brain area responsible for memory.

Dr. Yue Leng, the senior author of the study and an associate professor of psychiatry and behavioral sciences at the University of California — San Francisco (UCSF), emphasized that the timing of REM sleep is critical for cognitive health. According to the study, a delay in REM sleep is associated with elevated levels of amyloid and tau—two toxic proteins linked to Alzheimer’s disease.

The scientific study involved 128 participants with an average age of 70, who were hospitalized at the China-Japan Friendship Hospital in Beijing. The group included individuals with Alzheimer’s disease, mild cognitive impairment, and normal cognitive status. Participants underwent overnight sleep studies that monitored brain wave activity, eye movements, heart rate, and breathing patterns.

The main findings revealed that individuals with a delay in REM sleep, defined as taking more than 193 minutes to enter REM phase, had 16% more amyloid, 29% more tau, and a 39% lower level of brain-derived neurotrophic factor—a protein critical for brain health—compared to those whose REM sleep occurred earlier. These biomarkers are closely linked to the progression of Alzheimer’s disease.

The study also discovered that improving REM sleep through interventions could potentially slow disease progression. Melatonin and other medications that regulate REM sleep have shown effectiveness in reducing tau and amyloid accumulation in preclinical trials in mice. Sleep disorders, such as sleep apnea, and lifestyle factors, like excessive alcohol consumption, have been noted as potential disruptors of this essential stage.

Dr. Dantao Peng, a co-author of the study and a neurologist at the China-Japan Friendship Hospital, highlighted the importance of addressing such issues and maintaining healthy sleep to bolster cognitive health. He also advised individuals taking medications like antidepressants and sedatives, which may suppress REM sleep, to consult with a physician regarding potential risks.

Further research by scientists may explore the role of sleep-altering medications in the prevention and treatment of Alzheimer’s disease. The connection between REM sleep and Alzheimer’s underscores the broader significance of sleep for our overall health, the authors note. According to the Sleep Foundation, adults should aim for 7-9 hours of sleep per night to maintain good well-being and robust cognitive functions.

This material is for informational purposes only and does not contain advice that may affect your health. If you are experiencing issues, consult a specialist.