Struggling to enter the rapid eye movement (REM) stage of sleep could be an early sign of Alzheimer's disease, according to a new study from Chinese researchers. The REM phase, the deepest stage of the sleep cycle, is crucial for memory, learning, and creativity. Delays in reaching this stage were linked to higher levels of toxic proteins amyloid and tau in the brain, which are hallmarks of Alzheimer's.
The study, published in the journal Alzheimer's and Dementia, tracked the sleep patterns of 128 volunteers with an average age of 70. Half had Alzheimer's, about one-third had mild cognitive impairment, and the rest had normal cognition. Researchers monitored brainwave activity, eye movement, heart rate, and breathing during a night in the clinic.
Participants were divided into early and delayed REM sleep groups. The early group reached REM in less than 98 minutes after falling asleep, while the late group took more than 193 minutes. Those with Alzheimer's were more likely to have delayed REM sleep, with 16% more amyloid and 29% more tau than the early REM group. They also had 39% less brain-derived neurotrophic factor (BDNF), a protein that drops in Alzheimer's.
Dr. Yue Leng, an associate professor at the University of California, San Francisco, said: 'The delay in REM sleep disrupts the brain's ability to consolidate memories by interfering with the process that contributes to learning and memory. 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.'
Previous research on mice has suggested that melatonin can boost REM sleep and reduce tau and amyloid accumulation. The scientists advise those concerned about Alzheimer's risk to practice healthy sleep habits, treat conditions like sleep apnea, and avoid heavy drinking. Patients taking antidepressants or sedatives that reduce REM sleep should discuss concerns with their doctor.
