Just like eating and drinking, sleeping is necessary for the body to function. For years, scientists have studied the impact of sleep on overall health. One major area receiving a lot of attention over this past year is the effect of sleep on both dementia in general and Alzheimer’s disease. Although research is still ongoing and answers are still needed, medical professionals agree sleep plays an important role in keeping the brain healthy.

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Does sleep influence Alzheimer’s risk? We investigate. Image credit: Oleksii Syrotkin/Stocksy.

Although it is recommended most adults receive 7 or more hours of sleep each night, many people struggle with getting enough shut-eye.

Previous research shows sleep deprivation to be a global issue.

Another global health concern receiving much attention lately is that of dementia, in general, and a specific type of dementia known as Alzheimer’s disease.

Right now, more than 55 million people around the world live with dementia. And that number is expected to increase to 78 million by 2030 and 139 million by 2050.

Because sleep is important for a variety of brain functions and many people who have dementia experience sleep disturbances, researchers have taken an increased interest in figuring out what the link between sleep and risk for dementia and Alzheimer’s disease might be.

Let us take a closer look at why sleep is so important for brain health and some of the ways scientists believe sleep correlates with dementia risk.

According to Dr. Karen D. Sullivan, a board-certified neuropsychologist and owner of I CARE FOR YOUR BRAIN, sleep is a staple of physical and mental health including brain health:

“There are several major functions that occur during sleep including memory consolidation, emotional processing, and a deep cleaning process. In deep sleep, our cerebrospinal fluid and the brain’s immune system clear away waste products from our brain cells.”

“When we are awake, neurons produce a chemical called adenosine — a by-product of the cells’ activities,” Dr. Sullivan continued. “Without consistent deep sleep, we have an incomplete clearing of adenosine and other waste products like blood cells and the result is chronic inflammation. Chronic inflammation is the cause or exacerbator of many brain diseases and disorders.”

Dr. John Showalter, chief product officer at digital cognitive assessment platform provider Linus Health, said sleep is also important because it is restorative, meaning it is when the brain and body slow down to recover from the activities of the day.

“Without time to recover, the brain cannot adequately repair itself from the daily wear and tear of life,” he explained to Medical News Today. “Over time this lack of repair leads to dysfunction and disease.”

And Dr. Raphael Wald, a neuropsychologist at Baptist Health Marcus Neuroscience Institute, said our brains are both electrical and chemical entities that are constantly working, much like the engine of a car.

“During sleep, the brain rests and prepares for more work,” he explained to MNT. “A car engine cannot work continuously without maintenance. Sleep is like an oil change for the brain to renew it for more work.”

One area researchers have been focusing on is the effect of poor sleep — such as sleep apnea and insomnia — on the brain.

One study in May 2023 found sleep apnea may lead to a loss in brain volume, affecting memory. Another study in May found that obstructive sleep apnea was associated with increased white matter abnormalities in the brain, and noted that such abnormalities may contribute to an increased risk for both dementia and stroke.

A study in June 2023 says sleep-initiation insomnia may elevate dementia risk. And a study in December 2022 found insomnia was associated with higher levels of the cerebrospinal fluid biomarker CSF Aβ42, which is associated with Alzheimer’s disease.

“Large meta-analyses have shown a link between poor sleep quality and memory loss,” Dr. Owen Deland, a geriatrician at Hackensack University Medical Center explained to MNT. “Not only does poor sleep interfere with the body’s natural recovery processes, but sleep disorders like sleep apnea can actually increase your risk of heart disease and stroke, both of which also increase your risk of dementia.”

“Inadequate sleep interferes with your brain’s ability to learn and remember new information,” he continued. “Insomnia and worsening memory also form a vicious cycle, and having memory impairment can lead to more problems with getting adequate sleep.”

Another topic of interest this past year has been the effect of sleeping pills on dementia risk. However, the research so far has been conflicting.

For example, a study in March 2023 found that people who took the insomnia medication suvorexant experienced a drop in the Alzheimer’s-related proteins beta-amyloid and tau.

Conversely, another study earlier this year found frequent use of sleep medications was associated with an increased risk for dementia in certain ethnic groups.

“‘Sleeping pills’ is a term used for several types of medications, including antihistamines, benzodiazepines, hypnotics, and antidepressants,” Dr. Showalter explained. “Each type of medication affects the brain differently and likely contributes to the conflicting research.”

“Readers, especially older adult readers, should approach all types of sleeping pills with caution, he continued. “Medication should only be used if non-medical approaches have failed. It is also important to investigate common medical causes for poor sleep, such as obstructive sleep apnea, before starting over-the-counter sleep aids.”

“I think the best approach can be to educate oneself about how to get a good night’s sleep and try to use non-pharmacologic measures to improve your sleep,” Dr. David Merrill, a geriatric psychiatrist and director of the Pacific Neuroscience, told MNT. “Things like sleep hygiene, meditative activities in the evening, winding down — all those great non-pharmacological approaches really will get you a lot further than turning to a sleeping pill for the long term.”

And researchers have also been examining deep sleep and the role it plays in helping a person keep their memories.

“Deep sleep is the stage of sleep where our brain activity slows and we don’t wake as easily,” Dr. Deland explained. “This is dreamless sleep, usually occurring later during the night right before dreaming sleep, known as REM. During deep sleep, growth hormone is released and the body performs recovery and clean up.”

A study from May 2023 says that deep sleep may help protect against memory loss in older people with elevated amounts of beta-amyloid in the brain. And a study released earlier this month found that applying deep-brain stimulation when a person is in deep sleep improves their brain’s ability to make memories.

“We see less memory loss in older adults who have high-quality nightly sleep,” Dr. Sullivan said. “We also know that the restorative clearing-out functions of sleep are at their most effective during deep sleep, which removes some of the toxic proteins that build up to cause Alzheimer’s disease.”

“The commonly accepted belief is that deeper sleep helps you perform and consolidate memories, so if you don’t get to that part of sleep, then you don’t consolidate memories,” explained Dr. Clifford Segil, a neurologist at Providence Saint John’s Health Center in Santa Monica, CA.

“The interesting part of this theory is as you age by design, our brain doesn’t let you go into those deeper waves of sleep anyway. And by design, as people age, their sleep requirements go down. Younger people get more deep sleep than older people — that is why younger people are more easily able to consolidate and form memories,” he suggested.

And Dr. Merrill said that while deep sleep may decrease as we age, there are ways to help increase it.

“Taking a warm shower before you go to bed, [making] sure you don’t get any screen time after dark, not eating a big meal too close to bedtime — all these things may help [with] deep sleep,” he detailed.

Although it can sometimes be hard to make sleep a priority, all experts agree getting enough sleep is vital for not just good brain health, but good overall health.

“We know that poor general health puts a person at a higher risk for Alzheimer’s disease,” Dr. Wald said. “Without proper rest, our bodies cannot work properly in order to maintain health. Subsequently, it would seem to be a logical conclusion that poor sleep might lead to dementia.”

Here are some tips from experts on how to improve your sleep:

  • try to wake up and go to sleep at the same time every day
  • avoid electronics that emit blue light — such as television, computers, tablets, or smartphones — at least 1 to 2 hours before bed.
  • try reading instead of watching television before bed
  • exercise daily, but not right before going to sleep
  • avoid caffeinated beverages in the afternoon
  • try not to nap in the afternoon
  • avoid large meals at least 1 hour before going to sleep
  • only go to bed when you feel sleepy
  • establish a pre-sleep ritual to let your body know that it is time to wind down
  • do a relaxing activity, such as meditation or deep breathing, before bedtime
  • set up your sleeping area so it is cool, dark, and quiet
  • use your bed for sleeping and intimacy only
  • use a smartwatch or other device to track your sleep
  • expose yourself to sunlight when you wake up.

And if you do find yourself not getting adequate sleep, Dr. Segil advised making sure to pay off your “sleep debt.”

“More sleep is better than less sleep and I’m a firm believer in sleep debt,” he continued. “If you’re unable to get a good night of sleep for any reason, please pay off your sleep debt as soon as possible, or sleep more the following night the amount of sleep you lost prior.”