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Having delayed dreams during sleep? Watch out for Alzheimer’s

A new study from the University of California, San Francisco (UCSF) and partners discovered a potential early warning sign of Alzheimer's disease: a large delay in entering rapid eye movement (REM) sleep, a phase of the sleep cycle characterized by heightened brain activity, vivid dreams, and rapid movement of the eyes beneath closed eyelids. It typically occurs about 90 minutes after falling asleep and recurs several times throughout the night, with each REM phase becoming longer as the night, which is necessary for memory consolidation and emotional control. The findings, published in Alzheimer's and Dementia: The Journal of the Alzheimer's Association, contribute to a growing body of research relating sleep quality and timing to the advancement of neurodegenerative disorders.

REM sleep is the fourth stage of a typical sleep cycle, following three increasingly profound stages of non-REM sleep. This phase, which is critical for memory and emotional processing, begins around 90 minutes after falling asleep in healthy people. Older persons frequently take longer to enter REM sleep, but a recent study reveals that prolonged delays may reflect underlying brain alterations associated with Alzheimer's. 

"Delayed REM sleep disrupts the brain's ability to consolidate memories and may increase stress hormone levels, which impair the hippocampus," noted Dr. Yue Leng, the study's principal author and associate professor at UCSF's Department of Psychiatry and Behavioural Sciences. The hippocampus, a brain region responsible for memory formation, is especially prone to Alzheimer's disease impairment. 

The study, which took place at the China-Japan Friendship Hospital in Beijing, followed 128 volunteers who were on average 70 years old. Half of them had Alzheimer's disease, a third had mild cognitive impairment (MCI), and the rest were cognitively normal. Participants performed nocturnal sleep examinations to assess brainwave activity, eye movement, heart rate, and respiration.

The researchers separated the subjects into two groups depending on their REM sleep start times. The delayed REM group required more than 193 minutes to reach the dream phase, whereas the early REM group needed less than 98 minutes. 

The delayed REM group had a worrying pattern of biomarkers strongly associated with Alzheimer's disease. This group had a 16% higher level of amyloid plaques, which are harmful substances that disrupt brain connections and are characteristic of Alzheimer's disease. They also found a 29% rise in tau protein, a chemical known to build tangles in the brain, which contribute to cell degradation and cognitive loss. In addition to these findings, the group had 39% lower levels of brain-derived neurotrophic factor (BDNF), a protein essential for maintaining healthy neural connections and cognitive function. The loss of BDNF is especially concerning since it increases the brain's susceptibility to the toxic effects of amyloid and tau, resulting in a feedback loop that promotes neurodegeneration. These biomarkers show that delayed REM sleep has a big effect on brain function, which helps us understand how it might play a part in the progression of Alzheimer's. 

These findings point to delayed REM sleep as a potential early predictor of Alzheimer's progression, even before substantial cognitive symptoms appear. 

The study emphasises the bidirectional association between sleep problems and Alzheimer's. While Alzheimer's can disturb sleep patterns, inadequate sleep, particularly delayed REM, may hasten disease progression by increasing amyloid and tau accumulation.

Medications and lifestyle changes that increase REM sleep may provide new opportunities for Alzheimer's prevention and treatment. In tests on animals, melatonin supplements and drugs for insomnia that target molecules that stop REM sleep have shown promise in lowering levels of amyloid and tau. 

"Future research should explore how these treatments affect disease progression in humans," Dr. Leng told me. 

People who are concerned about their risk of getting Alzheimer's disease must ensure they get enough and quality REM sleep. According to research, REM sleep plays an important role in memory consolidation and cognitive function; therefore, adopting sleep practices that encourage this restorative phase is a top priority. Addressing sleep apnoea, a common condition that disturbs REM sleep with frequent breathing disruptions, is an important step. Furthermore, avoiding chemicals that interfere with the natural evolution of sleep cycles, such as alcohol and powerful sedatives, can aid in the maintenance of REM sleep. Those taking antidepressants or other medications that may impact their sleep patterns should talk with their doctor to discuss alternatives or changes. People who take proactive steps to maintain healthy REM cycles can improve their cognitive resilience and potentially minimise their risk of Alzheimer's disease. 

Dr. Dantao Peng, a co-author from the China-Japan Friendship Hospital, stated, "Treating sleep disorders and avoiding substances that impair REM sleep could be pivotal in reducing Alzheimer's risk." 


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