One of the easiest and most important things you can do to improve your memory and protect against dementia is to go to bed at a regular time every night and sleep well.

If you’re a long-time reader of this newsletter, then you’ve likely heard me tout the memory benefits of sleep many times before. Now, a recent study reveals another reason why sleep is so critical to memory and, even more important, how much sleep you really need.

Psychologists at the University of California, Berkeley, recently studied sleep habits in relation to maintaining a healthy brain as you age.

The research team found that poor sleep is linked to changes in the brain that are connected to the development of Alzheimer’s disease. For example, they found that people who report a declining quality of sleep as they age from their 50s to their 60s have more amyloid beta protein tangles in their brain, putting them at higher risk of developing Alzheimer’s disease.

“Insufficient sleep across the lifespan is significantly predictive of your development of Alzheimer’s disease pathology in the brain,” said the study’s senior author, Matthew Walker, a sleep researcher and professor of psychology.1

Another group of researchers, led by Joe Winer, a postdoctoral research fellow at Stanford University in California, is teasing out even more details about the link between sleep and cognitive health.

It seems when it comes to sleep, there’s a sweet spot. Too little is detrimental, but so is too much. Mr. Winer’s new study, published in the journal JAMA Neurology, begs the question2

How Much Sleep is Enough? 

The authors of this new study understood that disrupted sleep is common in later years. And when sleep changes occur, so do changes to cognitive function — the mental capacity for learning, thinking, reasoning, problem-solving, decision-making, remembering and paying attention can all become negatively affected.3

Equally important, the researchers knew that age-related changes in sleep have been linked to early signs of Alzheimer’s disease.4

The researchers wanted to investigate possible links between self-reported sleep duration, demographic and lifestyle factors, subjective and objective cognitive function, as well as participants’ levels of beta amyloid proteins.

The team found that both ends of the sleep duration spectrum could have varying effects on older adults’ brain health.

Sweet Spot for Sleep 

Those in the study who operated on a sleep deficit – six hours or less – had elevated levels of amyloid beta. Mr. Winer explains that amyloid beta “greatly increases” risk for dementia. (There is research that questions the link between amyloid beta and Alzheimer’s disease—more on this in a minute— although this is still the accepted belief in the medical community.)

Mr. Winer and his team compared this group of short sleepers to participants who reported normal sleep patterns, which the researchers defined as seven to eight hours of sleep per night.

What did they learn?

The older adults with insufficient sleep performed moderately to significantly worse on tests commonly used for assessing cognitive abilities, memory, language, visual-spatial skills; and identifying mild dementia.

And what about those snoozers who reported sleeping nine or more hours a night? Researchers said that while this group did display lesser executive function, they did not have elevated amyloid beta levels.

Make Time for Sleep 

“The main takeaway is that it is important to maintain healthy sleep late in life,” Mr. Winer said. “Additionally, both people who get too little sleep and people who get too much sleep had higher (body-mass index and) more depressive symptoms.”

He added that the findings suggested that both short and long duration sleep might involve different underlying disease processes. But the presence of amyloid beta (amyloid-β) is of utmost concern.

“Amyloid-β is one of the first detectable markers in the progression of Alzheimer’s disease,” Mr. Winer explains. “In Alzheimer’s disease, amyloid-β proteins start to build up throughout the brain, sticking together in plaques. Amyloid plaques are more likely to appear as we age, and many people with amyloid built up in their brains remain healthy.”

He notes that about 30 percent of healthy 70-year-olds will have substantial amounts of amyloid plaques in their brain. Not only do many healthy adults have high levels of the plaques, but many people with dementia don’t have them. What’s more, drugs that target amyloid-beta plaques have not been successful in treating dementia. Having said that, it’s well-known that poor-quality sleep increases dementia risk, and the research cited in this article clearly supports that finding, and further shows that lack of sleep physically alters the brain.

My Takeaway 

As with most self-reported studies, this one has its limitations. However, some interesting patterns did emerge. For instance, both the short- and long-sleep duration groups reported more depressive symptoms than the normal sleep group.

While self-reported caffeine intake didn’t appear to influence sleep, alcohol consumption did. It seems the more alcoholic drinks participants drank daily, the more likely they were to sleep longer.

If you need some guidance to improve your sleep habits, then try these tips from the Sleep Foundation for practicing good sleep hygiene: set a regular sleep schedule, follow a nightly pre-sleep routine, cut down on caffeine, especially in the afternoon and evening, and restrict in-bed activities such as watching television or eating.5

For more good sleep hygiene tips, go to https://www.sleepfoundation.org/sleep-hygiene.


  1. https://news.berkeley.edu/2019/06/26/disrupted-sleep-in-ones-50s-60s-raises-risk-of-alzheimers-disease/ 
  2. https://jamanetwork.com/journals/jamaneurology/article-abstract/2783664?utm_campaign=articlePDF&utm_medium=articlePDFlink&utm_source=articlePDF&utm_content=
    jamaneurol.2021.2876 
  3. https://www.sciencedirect.com/topics/psychology/cognitive-functioning 
  4. https://nhats.org/researcher/nhats 
  5. https://www.sleepfoundation.org/sleep-hygiene 

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