Alzheimer’s disease linked to dream quality and amount of REM sleep

A recent study suggests that Alzheimer’s disease may have a stronger connection to sleep than previously believed, with both sleep quality and duration playing a significant role in its development.

Disruptions in sleep, especially during the transition to REM, may serve as early signs of cognitive decline. REM sleep is important for memory consolidation, emotional processing, and overall brain health.

“Sleep disturbances are common in patients with dementia and have been associated increasingly with Alzheimer’s disease and Alzheimer’s disease and related dementias (AD/ADRD) biomarkers, even in preclinical stage of the disease,” noted the study authors.

Understanding the various sleep stages, including REM, could provide valuable insights for Alzheimer’s research.

How sleep changes with age

Sleep, for health purposes, isn’t just a singular, seamless cycle. We undergo three distinct phases of non-REM sleep, each progressively deeper than the former, before finally transitioning into REM sleep.

The completion of this cycle typically takes 90 minutes or longer, depending on age. As people get older, it often takes longer to move into REM sleep.

This delay may indicate underlying neurological changes, potentially linked to Alzheimer’s progression.

REM sleep and memory connection

During REM sleep, the brain is hard at work processing memories – particularly those that are emotionally charged – and depositing 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,” said Dr. Yue Leng, an associate professor in the Department of Psychiatry and Behavioral Sciences at UCSF.

“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.”

Sleep patterns in Alzheimer’s patients

The researchers observed 128 individuals (with an average age of 70) in the neurology unit of the China-Japan Friendship Hospital in Beijing. Among them, half were diagnosed with Alzheimer’s, about one-third had mild cognitive impairment, and the rest had normal cognition.

The participants spent a night in the clinic, allowing researchers to monitor their brainwave activity, eye movement, heart rate, and breathing.

Based on these observations, the researchers categorized the individuals into groups of early and delayed REM sleep. The former group transitioned to REM sleep in less than 98 minutes, while the latter typically took over 193 minutes.

Delayed REM sleep and Alzheimer’s

The researchers identified an interesting pattern. Patients with Alzheimer’s were more prone to delayed REM sleep, and they also exhibited higher levels of two toxic proteins – amyloid and tau – commonly associated with the condition.

Individuals with prolonged REM sleep had higher amyloid levels by 16% and tau levels by 29% compared to their counterparts with early REM sleep. They also had a 39% decrease in a beneficial protein called brain-derived neurotrophic factor (BDNF), known to drop in Alzheimer’s.

Potential strategies against Alzheimer’s

With these findings in mind, the researchers recommend taking a closer look at the effects of medications that influence sleep cycle.

“Future research should study the effects of certain medications that influence sleep patterns, as these may modify disease progression,” Leng said.

Melatonin, known for its role in sleep regulation, has been shown in animal studies to boost REM sleep while reducing tau and amyloid accumulation.

Other insomnia medications that block chemicals suppressing REM sleep have demonstrated similar effects.

Prioritizing healthy sleep habits

For individuals who are concerned about their Alzheimer’s risk, prioritizing healthy sleep habits may be beneficial.

“This includes treating conditions like sleep apnea and avoiding heavy drinking, since both can interfere with a healthy sleep cycle,” said Dr. Dantao Peng of the Department of Neurology at the China-Japan Friendship Hospital in Beijing, who is also a senior author of the study.

“Patients taking certain antidepressants and sedatives that reduce REM sleep should discuss their concerns with their doctor, if they are worried about Alzheimer’s.”

In conclusion, while sleep alone may not serve as a standalone indicator of Alzheimer’s, it is becoming increasingly clear that sleep patterns play a crucial role in brain health.

The research was published in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.

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