Recent scientific discoveries have illustrated that the quality and quantity of our sleep may play a crucial role in our susceptibility to developing Alzheimer’s disease. A new study has revealed that individuals who experience extended delays before entering the dream phase of sleep, known as rapid eye movement (REM) sleep, might be exhibiting an early indicator of the disease.
Three stages of non-REM sleep precede REM sleep, each deeper than the last. These stages collectively take around 90 minutes or more to cycle through, with variations depending on a person’s age. A typical night might include four to five cycles of these stages. It has been observed that older adults often require more time to reach the REM stage.
During REM sleep, the brain actively processes and stores memories, particularly those with emotional significance, into long-term memory storage. According to Yue Leng, PhD, an associate professor at the UCSF Department of Psychiatry and Behavioral Sciences, a delay in reaching REM sleep can interfere with this memory consolidation. Dr Leng, also affiliated with the UCSF Weill Institute for Neurosciences, explains that a disruption in REM sleep can elevate stress hormone cortisol levels, which may harm the hippocampus, an area of the brain essential for memory consolidation.
Dr Leng is the senior author of a study published on January 27 in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association, which examined 128 individuals with an average age of 70. The participants were recruited from the neurology unit at the China-Japan Friendship Hospital in Beijing, and their group included individuals with Alzheimer’s, those with mild cognitive impairment—a common precursor to Alzheimer’s—and others with normal mental functions.
For the study, participants spent a night in a clinic, where their brainwave activity, eye movements, heart rate, and respiration were monitored. Although fitness trackers can collect some of this data, the precision achieved in a clinical setting is unmatched.
The researchers categorized the participants according to their REM sleep timing into early and delayed groups. The early group entered REM sleep less than 98 minutes after falling asleep, whereas the delayed group took more than 193 minutes. Notably, those in the delayed REM sleep group not only had higher levels of amyloid and tau—proteins associated with Alzheimer’s—but also showed significantly lower levels of a healthy protein called brain-derived neurotrophic factor (BDNF), which is known to decrease in Alzheimer’s patients.
These findings have significant implications, as they suggest that interventions targeting sleep patterns may alter the progression of Alzheimer’s disease. Dr. Leng highlights the potential of medications like melatonin, which has been shown to enhance REM sleep and reduce amyloid and tau accumulation in animal studies. Other pharmaceuticals designed to treat insomnia by inhibiting chemicals that suppress REM sleep have also demonstrated promise in decreasing levels of these harmful proteins.
Dr. Dantao Peng, MD, another senior author from the Department of Neurology at the China-Japan Friendship Hospital, advises individuals concerned about their risk of Alzheimer’s to cultivate sleep habits that promote an efficient transition from light to REM sleep. This includes managing conditions like sleep apnea and avoiding excessive alcohol consumption, which can disrupt the sleep cycle. Additionally, Dr. Peng suggests that patients using certain antidepressants and sedatives known to reduce REM sleep should consult their physicians if they have concerns about Alzheimer’s disease. This proactive approach in addressing sleep-related issues could be a pivotal step in the management and potentially the prevention of Alzheimer’s disease, signalling a new frontier in our understanding of the relationship between sleep health and neurodegenerative diseases.
More information: Yue Leng et al, Association of rapid eye movement sleep latency with multimodal biomarkers of Alzheimer’s disease, Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association. DOI: 10.1002/alz.14495
Journal information: Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association Provided by University of California – San Francisco
