Researchers have revealed a potential early indicator that might hint at the risk of developing Alzheimer’s disease. Individuals who experience delays in entering the dream phase of sleep, referred to as rapid eye movement or REM sleep, may face a heightened risk of dementia.
The study, conducted by scientists at the University of California San Francisco, suggests there is a link between sleep duration and quality, and the chance of developing Alzheimer’s later in life. Those who took “significantly longer” than usual to arrive at the REM stage were identified as potentially more susceptible to the disease.
The journey into REM sleep occurs after navigating through three progressive stages of non-REM sleep, with each phase drawing a person into a deeper sleep state. Normally, it can take up to 90 minutes to reach REM sleep, though this process may take longer as we age. These sleep stages tend to cycle multiple times throughout the night.
REM sleep is vital for brain function as this is the period when memories are processed and stored in the long term. This stage is also key for the emotional processing linked to these memories.
Professor Yue Leng, the co-senior author of the study, shed light on the implications of delayed 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. 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.”
A study at Beijing’s China-Japan Friendship Hospital neurology unit has provided new insights into the link between sleep patterns and Alzheimer’s disease. The research involved 128 participants with an average age of 70, half of whom were already diagnosed with Alzheimer’s, while the others exhibited early symptoms. Their sleep details, including heart rate, brain activity, and eye movement, were recorded.
The team categorised the subjects into two groups based on their REM sleep patterns: those who entered REM sleep normally and those with delayed REM sleep. Findings revealed that individuals with delayed REM sleep were more prone to Alzheimer’s.
The delayed REM participants also showed higher levels of harmful toxins in their bodies, with an average increase of 16% in amyloid and 29% in tau proteins. They also had a significant 39% reduction in brain-derived neurotrophic factor (BDNF), which typically decreases in Alzheimer’s patients.
Professor Leng is keen to explore how medications affecting sleep could alter the course of the disease. She highlighted that melatonin has been shown to aid REM sleep and, in animal studies, as well as reducing tau and amyloid build-up. “Future research should study the effects of certain medications that influence sleep patterns, as these may modify disease progression.”, she said.
Dr Dantao Peng, the study’s co-senior author, underscored the importance of addressing sleep concerns for overall health: “This includes treating conditions like sleep apnoea and avoiding heavy drinking, since both can interfere with a healthy sleep cycle. Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor, if they are worried about Alzheimer’s.”
For individuals interested in monitoring their sleep habits, smartwatches and similar devices can provide data on REM sleep duration, but with less precision than scientific research tools. While these gadgets offer insights, they don’t match the accuracy found in clinical settings. The NHS website has further information on Alzheimer’s disease.