About every three seconds, someone develops dementia. In most cases, the cause is Alzheimer’s disease (AD). While researchers are still looking for a cure, we are far from helpless against this disease. A 2020 study published in the journal Neurology found that healthy lifestyle choices could reduce the risk of AD by up to 60 percent. Doctors call these choices manageable risk factors.

A 2023 study published in the American Medical Society’s journal JAMA Neurology found that a very important manageable risk factor for AD is getting enough deep sleep. According to the study, as little as a 1 percent reduction in deep sleep time per year equals a 27 percent higher risk of developing AD. The trial looked at sleep studies done several years apart in 346 people ages 60 to 87. During a sleep study, brain waves can be measured to tell when a person is in the stage of deep sleep. Over an average of 17 years, 44 people in the study were diagnosed with AD. By comparing how much deep sleep decreased between sleep studies, the researchers were able to determine that more time in deep sleep was associated with a considerably lower risk of AD.

How deep sleep reduces the risk of AD

Sleep researchers describe three stages of falling asleep, each one taking you deeper into sleep. When you reach the third stage, a deep sleep called slow-wave sleep, brain waves become long and slow, and your blood pressure, breathing, and heart rate drop. The fourth stage is called rapid eye movement (REM) sleep, which is when you dream. Going through the four stages of sleep is called a sleep cycle. Deep sleep accounts for about 20 to 30 percent of the cycle. A person who sleeps well will go through up to six of these cycles each night. 

All the stages of sleep are important, but deep sleep (the third stage) is the most important for restoring your mind and body. You are very relaxed and hard to wake in deep sleep. Sleep experts believe that during deep sleep, your brain is imprinting new thoughts and experiences and saving memories.

In the last 10 years, sleep researchers discovered a new and very important aspect of deep sleep called the glymphatic system. Your brain is an extremely active organ. To keep all the systems of your body running, it needs a constant supply of oxygen and glucose (sugar) for energy production. This is called brain metabolism. It takes a lot of energy to fire neurons and make new connections between neurons, and that energy production creates metabolic waste in the form of protein fragments and other toxins that leak out between brain cells.

To deal with that waste, the glymphatic system serves as the brain’s waste management plan. In deep sleep, the spaces between brain cells becomes more open, allowing cerebrospinal fluid to flood the spaces and wash out the waste. It’s essentially a brain washing. The cerebrospinal fluid takes the waste back to the bloodstream, where it can be eliminated by the kidneys or detoxed in the liver.

The proteins that are removed are called beta amyloid. If these proteins build up, they cut off communications between brain cells. Eventually, they can form the beta amyloid clumps that cause the loss of brain cells, as seen in AD.

Researchers already knew that people who sleep less may be at higher risk for AD, but now they know that disruption of the glymphatic system may explain how and why.

How to get more deep sleep

You can’t just drop off into deep sleep. The only way to increase deep sleep is to get enough sleep cycles each night, which means making seven to eight hours of sleep every night a priority.

Before electricity, humans went to bed when it got dark and got up with the sun. This made it easy for the brain’s internal clock to regulate sleep stages and cycles. In our 24-hour connected world, the hours and cycles of sleep are under constant stress.

That challenge has led to the concept of sleep medicine and sleep hygiene. Sleep medicine researchers have been finding out why evolution has designed our brains and bodies to sleep one-third of our lives away. Failure to get the recommended seven to eight hours of sleep has been linked to dementia, diabetes, heart disease, high blood pressure, depression, anxiety, and even suicide.

Sleep hygiene is the lifestyle changes and choices you can make to get enough sleep. It includes your sleep environment and sleep habits. Here are the fundamentals:

  • Go to bed and get up at the same time every day.
  • Keep your bedroom cool, quiet, and dark at night. Remove all light, including light from alarm clocks, television boxes, nightlights, etc.
  • Get exposure to outdoor light in the daytime to help regulate your biologic clock.
  • Avoid food, caffeine, and alcohol in the hours before sleep.
  • Reduce your fluid intake in the evening. Hydrate earlier in the day if possible.
  • Avoid exposure to blue light (phones, computers, and television) for at least 30 minutes before bed.
  • Reserve the bedroom for only sleep and sex.
  • If you can’t fall asleep, don’t lie in bed worrying. Get out of bed, read or do a calm, nonelectronic activity until you get tired, and try again.

Beware fragmented sleep

Prostate enlargement in older men, arthritis, sleep apnea, and a long list of sleep disorders can lead to fragmented sleep, which is another enemy of deep sleep. An interrupted sleep cycle decreases time in deep sleep. If you have trouble falling asleep or staying asleep, talk to your doctor. You might benefit from a referral to a sleep medicine specialist.

Additional recommendations

The 2020 Neurology study found that several additional healthy lifestyle choices could reduce AD risk by up to 60 percent:

  • Don’t smoke.
  • Get 150 minutes of moderate to vigorous physical activity per week.
  • Follow a healthy Mediterranean diet.
  • Avoid an excess use of alcohol.
  • Engage in brain-stimulating activities throughout your life.

People who adhered to at least four of these habits were 60 percent less likely to get AD than people who followed only one or none. Take note that this study did not include sleep hygiene, so that could further reduce risk. A healthy lifestyle, along with healthy sleep, could knock your AD risk down significantly.

It takes about seven years for AD to develop, so now would be a good time to start working on your sleep and other healthy lifestyle changes.

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