Summary:
A new study highlights a potential link between delayed progression to the dream phase of sleep (REM sleep) and an increased risk of Alzheimer’s disease. Researchers found that participants with delayed REM sleep had higher levels of amyloid and tau proteins, both hallmarks of Alzheimer’s, as well as lower levels of brain-derived neurotrophic factor (BDNF), a protein that supports memory and learning. The findings suggest that disrupted REM sleep may impair the brain’s ability to consolidate memories, contributing to disease progression. The study also points to interventions, such as improving sleep hygiene, treating conditions like sleep apnea, and exploring medications that influence sleep patterns, as potential ways to mitigate risk.
Key Takeaways:
- Sleep Delays and Alzheimer’s Risk: Delayed progression to the dream phase of sleep is associated with higher levels of amyloid and tau proteins, which are linked to Alzheimer’s disease.
- Memory Consolidation Impacts: Disrupted REM sleep impairs the brain’s ability to consolidate emotionally charged memories, potentially accelerating cognitive decline.
- Potential Interventions: Treating sleep disorders, adopting healthy sleep habits, and exploring medications that boost REM sleep may help reduce Alzheimer’s risk and slow disease progression.
Scientists have recently shown that both the quality and the amount of sleep we get may influence our risk of developing Alzheimer’s disease.
Now, a study suggests that people who take significantly longer to start the dream phase of sleep, known as rapid eye movement (REM), may be experiencing an early symptom of the disease.
REM follows three phases of non-REM sleep, each deeper than the last. The four phases take 90 minutes or more to complete, depending on age, and a person may cycle through them four or five times in a typical night. Older people take longer to reach REM.
During REM sleep, the brain processes memories, especially those that are emotionally charged, and puts them into long-term storage.
“The delay in REM sleep disrupts the brain’s ability to consolidate memories by interfering with the process that contributes to learning and memory,” says Yue Leng, PhD, an associate professor in the Department of Psychiatry and Behavioral Sciences at the University of California, San Francisco (UCSF), in a release. “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.”
Leng, who is part of the UCSF Weill Institute for Neurosciences, is a senior author of the paper, which appears in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
Higher Levels of Amyloid, Tau
Researchers followed 128 people with an average age of 70 from the neurology unit of the China-Japan Friendship Hospital in Beijing. Half had Alzheimer’s, and about one-third had mild cognitive impairment, a frequent precursor to Alzheimer’s. The rest had normal cognition.
The participants in the study slept overnight in the clinic, so researchers could measure their brainwave activity, eye movement, heart rate, and breathing. Fitness trackers can capture some of this information, but it is less precise.
The researchers divided the participants into early and delayed REM sleep. On average, the early group reached REM less than 98 minutes after falling asleep, while the late group reached it more than 193 minutes after falling asleep.
Those with Alzheimer’s were more likely to have delayed REM sleep, and they also tended to have higher levels of the two toxic proteins, amyloid and tau, found in people with the condition.
Those with delayed REM sleep had 16% more amyloid and 29% more tau than those with early REM sleep. They also had 39% less of a healthy protein called brain-derived neurotrophic factor (BDNF), which drops in Alzheimer’s.
“Future research should study the effects of certain medications that influence sleep patterns, as these may modify disease progression,” Leng says in a release.
Melatonin can boost REM sleep, and studies in mice have shown that it decreases tau and amyloid accumulation. Other drugs that treat insomnia by blocking a chemical that suppresses REM sleep also have been shown to decrease tau and amyloid.
People who are concerned about their risk for Alzheimer’s should practice healthy sleep habits that facilitate the transition from light sleep to REM sleep. “This includes treating conditions like sleep apnea and avoiding heavy drinking since both can interfere with a healthy sleep cycle,” says Dantao Peng, MD, of the Department of Neurology at the China-Japan Friendship Hospital in Beijing, who is also a senior author of the paper, in a release. “Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor if they are worried about Alzheimer’s.”
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