Sleep disturbances have previously been linked to faster accumulation of beta-amyloid protein in the brain.
Unraveling the link between Deep Sleep and Memory
However, new research from a team at UC Berkeley suggests that high amounts of deep, slow-wave sleep can induce sleep. a protective factor against memory decline in those with high levels of Alzheimer’s disease pathology—a potentially significant breakthrough that could help alleviate some of dementia’s most devastating consequences, experts say (1). “With a certain level of brain pathology, you’re not destined to have cognitive symptoms or memory problems,” said Zsófia Zavecz, a postdoctoral researcher at UC Berkeley’s Center for Human Sleep Sciences. “People should know that despite a certain level of pathology, there are certain lifestyle factors that will help to moderate and reduce the effects (1). “One of these factors is sleep, and especially deep sleep.”
The study was published in the journal BMC Medicine, It is the latest in a major effort to find a cure for Alzheimer’s disease and prevent it altogether.
Alzheimer’s disease, the most common form of dementia, destroys memory pathways and, in advanced forms, interferes with a person’s ability to perform basic daily tasks.
About one in nine people over the age of 65 have progressive disease—a rate expected to grow rapidly as the baby boomer generation ages.
Out of Memory Consolidation
In recent years, scientists have investigated the ways in which beta-amyloid deposits are linked to Alzheimer’s disease and how such deposits have a greater effect on memory.
In addition to sleep being a key part of memory retention, the UC Berkeley team previously discovered that a decrease in the amount of deep sleep a person gets can act as a “crystal ball” for forecasting a faster rate of future beta-amyloid deposition in the brain, after which dementia is more likely to develop.
Years of education, physical activity, and social engagement are believed to strengthen a person’s resilience to severe brain pathologies—keeping the mind sharp despite declining brain health.
These are called cognitive reserve factors. However, most of them, such as past years of education or the size of the social network, cannot be easily modified or changed in retrospect.
This idea of cognitive reserve has become an attractive target for sleep researchers, said Matthew Walker, UC Berkeley professor of neurology and psychology and lead author of the study.
“If we believe that sleep is very important for memory,” Walker said, “sleep could be one of the missing pieces in the explanatory puzzle of why two people with the same amount of bad, severe amyloid pathology have very different memory?”
“If the findings support the hypothesis, that would be exciting because sleep is something we can change,” he said. “It’s a modifiable factor.”
Neuroprotective Benefits of Deep Sleep
To test this question, researchers recruited 62 older adults from the Berkeley Aging Cohort Study. Participants who were healthy adults and not diagnosed with dementia slept in the lab while the researchers monitored their sleep waves with an electroencephalography (EEG) device.
The researchers also used positron emission tomography (PET) to measure the amount of beta-amyloid deposits in the brains of the participants. Half of the participants had high levels of amyloid deposits; the other half did not.
After they slept, the participants performed a memory task of matching names to faces.
Those with high levels of beta-amyloid deposits in their brains also lived higher levels of deep sleep resulted in better performance than those who had the same amount of savings but slept worse on a memory test.
This compensatory increase was limited to the group with amyloid deposits. In the non-pathology group, deep sleep did not have an additional supportive effect on memory, which is understandable, since there is otherwise no demand for sustainability factors in intact cognitive function.
In other words, deep sleep tilted the cognitive axis upward, to my crowd otherwise harmful effects beta-amyloid pathology on memory.
In their analysis, the researchers continued to control for other cognitive reserve factors, including education and physical activity, and still sleep showed a significant benefit.
This suggests that sleep helps rescue memory function in the face of brain pathology, independent of these other factors.
These findings, they say, point to the importance of non-REM slow-wave sleep in counteracting some of the memory-impairing effects of beta-amyloid deposits.
Walker likened deep sleep to a rescue effort
“Think of deep sleep as a life raft that keeps memory afloat rather than being swept away by the weight of Alzheimer’s disease pathology,” Walker said. “It now appears that deep NREM sleep may be a new, missing piece in the explanatory puzzle of cognitive reserve. This is particularly exciting because we can do something about it. Even in older adults, there are ways to improve sleep.”
Head among these areas for improvement? Stick to a regular sleep schedule, be mentally and physically active during the day, create a cool and dark sleep environment, and minimize late-night coffee and screen time before bed. Zavecz has shown that a warm shower before going to bed improves the quality of deep, slow-wave sleep.
Zavecz said the study, with a small sample size of healthy participants, is just the first step toward understanding the exact ways sleep can prevent memory loss and the development of Alzheimer’s disease.
However, this opens the door for potential long-term experiments investigating sleep-enhancing treatments that may have far-reaching effects.
“One of the advantages of this result is that it applies to a large population over the age of 65,” Zavecz said. “By sleeping better and doing your best to practice good sleep hygiene, which is easy to research online, you can benefit from this compensatory function against this type of Alzheimer’s pathology.