Deep sleep may mitigate Alzheimer’s memory loss

Deep sleep, also known as non-REM slow-wave sleep, may act as a “cognitive reserve factor” that can increase resistance against a protein in the brain called beta-amyloid that is linked to memory loss caused by dementia. Disrupted sleep has previously been associated with a more rapid buildup of beta-amyloid protein in the brain. However, new research from a UC Berkeley team reveals that higher amounts of deep, slow-wave sleep may act as a protective factor against memory decline in people with high amounts of Alzheimer’s disease pathology, a breakthrough. potentially significant that, according to experts. it could help alleviate some of the most devastating results of dementia.

“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 the UC Berkeley Human Sleep Sciences Center. “People need to be aware that despite having a certain level of pathology, there are certain lifestyle factors that will help moderate and lessen the effects.

“One of those factors is sleep, and specifically deep sleep.”

The research, published Wednesday in the journal BMC Medicineit is the latest in a large body of work aimed at finding a cure for Alzheimer’s disease and preventing it altogether.

As the most common form of dementia, Alzheimer’s disease 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 the progressive disease, a proportion that is expected to grow rapidly as the baby boom generation ages.

In recent years, scientists have investigated the ways in which beta-amyloid deposits are associated with Alzheimer’s disease and how such deposits also affect memory in general. In addition to sleep being a critical part of memory retention, the UC Berkeley team previously found that a person’s decreasing amount of deep sleep could act like a “crystal ball” to predict a faster rate of accumulation. future beta-amyloid buildup in the brain, after which dementia is more likely to develop.

It is widely believed that years of education, physical activity, and social engagement bolster a person’s resistance to serious brain pathology, essentially keeping the mind sharp, despite declining brain health. These are called cognitive reserve factors. However, most of them, such as the last years of education or the size of one’s social network, cannot be easily changed or modified retroactively.

That idea of ​​cognitive reserve became a compelling target for sleep researchers, said Matthew Walker, a UC Berkeley professor of neuroscience and psychology and lead author of the study.

“If we believe that sleep is so critical to memory,” Walker said, “sleep could be one of those missing pieces in the explanatory puzzle that would tell us exactly why two people with the same amount of severe and vicious amyloid pathology They have very different illnesses.” memory?”

“If the findings support the hypothesis, that would be exciting, because sleep is something we can change,” he added. “It’s a modifiable factor.”

To test that question, the researchers recruited 62 older adults from the Berkeley Aging Cohort Study. The participants, who were healthy adults and not diagnosed with dementia, slept in a laboratory while researchers monitored their sleep waves with an electroencephalography (EEG) machine. The researchers also used a positron emission tomography (PET) scan to measure the amount of beta-amyloid deposits in the participants’ brains. Half of the participants had large amounts of amyloid deposits; the other half don’t.

After sleeping, the participants completed a memory task that involved matching names to faces.

Those with large amounts of beta-amyloid deposits in their brain who also experienced higher levels of deep sleep did better on the memory test than those with the same amount of deposits but slept worse. This compensatory drive was limited to the group with amyloid deposits. In the non-pathology group, deep sleep had no additional supportive effect on memory, which was understandable since there was no demand for resilience factors on otherwise intact cognitive function.

In other words, deep sleep tipped the arrow of cognition up, mitigating the detrimental effects of beta-amyloid pathology on memory.

In their analysis, the researchers went on to control for other cognitive reserve factors, including education and physical activity, with immobile sleep demonstrating a marked benefit. This suggests that sleep, independently of these other factors, contributes to saving memory function against brain pathology. These new discoveries, they said, indicate the importance of non-REM slow-wave sleep in counteracting some of the memory-impairing effects of beta-amyloid deposits.

Walker compared deep sleep to a rescue effort.

“Think of deep sleep almost as a life raft that keeps memory afloat, rather than memory being dragged down 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 especially exciting because we can do something about it. There are ways we can improve sleep, even in older adults.”

Chief among those areas for improvement? Maintain a regular sleep schedule, stay mentally and physically active during the day, create a cool, dark sleep environment, and minimize things like coffee at the end of the day and screen time before bed. A warm shower before bed has also been shown to improve the quality of deep, slow-wave sleep, Zavecz said.

With a small sample of healthy participants, the study is just an initial step in understanding the precise ways that sleep can prevent memory loss and the progression of Alzheimer’s disease, Zavecz said.

Still, it opens the door for possible long-term experiments examining sleep-improving treatments that could have far-reaching implications.

“One of the advantages of this result is its application to a large population just over 65 years of age,” Zavecz said. “By getting better sleep and doing your best to practice good sleep hygiene, which is easy to research online, you can reap the benefit of this compensatory function against this type of Alzheimer’s disease.”