Research has recently highlighted the potential link between sleep patterns and the risk of developing Alzheimer’s disease. A particular focus has been the time it takes an individual to enter the rapid eye movement (REM) phase of sleep, with longer periods potentially signaling an early Alzheimer’s symptom.
Typically, the REM sleep phase follows three non-REM phases, each progressively deeper than the preceding one. This cycle, usually repeating four or five times in a night, can take 90 minutes or more to conclude, with older individuals taking a longer time to reach REM. This phase is crucial for memory consolidation as it’s when the brain processes memories, especially emotionally laden ones, and stores them for long-term use.
According to Yue Leng, PhD, an associate professor in the Department of Psychiatry and Behavioral Sciences at UCSF, a delay in reaching REM sleep can disrupt the brain’s memory consolidation process. This disruption might result in an increased cortisol level, the stress hormone, which might impair the hippocampus, a part of the brain central to memory consolidation.
The study, published in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association on Jan. 27, followed 128 participants, averaged aged 70, from the neurology unit of the China-Japan Friendship Hospital in Beijing. Half of them were Alzheimer’s patients, while about one-third had mild cognitive impairment, often a precursor to Alzheimer’s. The remaining participants had normal cognition.
The researchers classified participants into two groups – those who reached REM sleep early (less than 98 minutes after falling asleep) and those who reached it late (more than 193 minutes after falling asleep). The study showed that Alzheimer’s patients were more likely to have delayed REM sleep and had higher levels of two toxic proteins, amyloid and tau, often found in Alzheimer’s patients.
Furthermore, participants with delayed REM sleep had 16% more amyloid, 29% more tau, and 39% less of a healthy protein called brain derived neurotrophic factor (BDNF), which typically decreases in Alzheimer’s patients.
Yue Leng suggests that future research should explore the impact of medications influencing sleep patterns, as they could potentially modify Alzheimer’s disease progression. Some drugs that treat insomnia by blocking a chemical suppressing REM sleep have been shown to decrease tau and amyloid.
The study also recommends healthy sleep habits for those worried about Alzheimer’s risk, including treating conditions like sleep apnea and avoiding heavy drinking, as both can disrupt a healthy sleep cycle. Additionally, patients who take certain antidepressants and sedatives that reduce REM sleep should consult their doctors if they have Alzheimer’s concerns.
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