About 50 million people worldwide suffer from Alzheimer’s disease, the most common form of dementia. That number is predicted to triple by 2050. Yet, researchers believe that one-third of these cases could be avoided by following a healthy lifestyle. One element to a healthy life is better sleep.
Many of us recognize that our memory suffers after a night of poor sleep. We’re more forgetful and have trouble focusing. But what if you consistently miss out on sleep for years, as at least one-third of Americans do?
Could that ongoing sleep deprivation increase your risk of Alzheimer’s? According to a growing body of research, the answer is yes.
The Link between Sleep Deprivation and Alzheimer’s
Before we explain how sleep deprivation may contribute to Alzheimer’s, it will be helpful to understand how sleep works.
A lot goes on while you sleep. You may be dreaming, but your brain is hard at work, restoring and repairing you from the events of the day. Throughout the night, your body cycles through different stages of sleep, from light sleep to deep sleep to REM, and back again. All in, you might complete this cycle four to five times a night.
With each subsequent cycle, you spend increasing amounts in REM sleep, and less time in the other stages. During this stage of sleep, your brain sorts, processes, and organizes memories. You also dream and process emotional memories. When you wake up grumpy and irritable after a night of poor sleep, it’s because you didn’t get enough REM sleep.
REM matters for Alzheimer’s because it’s during this stage of sleep that your brain gets restored. And thanks to the way our sleep cycles work, when you don’t get a full night’s sleep, you miss out on REM most of all.
Sleep Deprivation Causes Beta-Amyloid Buildup, Increasing Alzheimer’s Risk
One other important function of REM sleep? “Taking out the trash,” as one study put it. During REM sleep, your brain clears out neurotoxic waste like beta-amyloid. Found in the cerebrospinal fluid between your brain cells, these are the same brain proteins that develop into Alzheimer’s-causing plaque.
According to the National Institutes of Health, beta-amyloid buildup is 43 percent higher among individuals with Alzheimer’s than in healthy older adults. Beta-amyloid buildup prevents your neurons from communicating properly, which may contribute to Alzheimer’s and result in impaired brain function.
The study, which was performed using mice, found that the brain clears beta-amyloid buildup 60 percent faster during sleep than when you’re awake.
Another study confirmed these findings, even in healthy adults without Alzheimer’s. Researchers tested beta-amyloid buildup after participants experienced a full-night’s sleep, and after they pulled an all-nighter. Just a single night of lost sleep increased beta-amyloid by 5 percent in the hippocampus and thalamus — two areas of the brain particularly vulnerable to Alzheimer’s disease. These are the clusters indicated in red, below:
Sleep Problems Are an Early Warning Sign of Alzhimer’s
Before receiving an official Alzheimer’s diagnosis, people may have an early form of the disease. They may not be experiencing memory loss or cognitive issues yet, but they start having sleep problems. Disrupted sleep can be one of the earliest warning signs of Alzheimer’s.
For example, in 2013, Washington University researchers analyzed the spinal fluids of 145 study participants to see if they could identify any signs of Alzheimer’s. Based on the presence of amyloid plaques, researchers determined that 32 of the participants did have preclinical Alzheimer’s disease, even though they weren’t yet experiencing any cognitive symptoms. Researchers then had all participants keep sleep diaries over a period of two weeks, where they noted the amount of time they spent in bed (including sleep and wake times), and whether they took any naps during the day.
The participants also wore wrist sleep trackers on their wrists, so the researchers could verify this information and ascertain their sleep efficiency. Sleep efficiency describes the amount of time you actually spend asleep, compared to the total amount of time you’re in bed. A high sleep efficiency indicates that you can fall and stay asleep in a normal manner.
The individuals with preclinical Alzheimer’s disease had a sleep efficiency that was about four percentage points lower than their non-Alzheimer’s counterparts. This trend intensified with poorer sleep: “When we looked specifically at the worst sleepers, those with a sleep efficiency lower than 75 percent, they were more than five times more likely to have preclinical Alzheimer’s disease than good sleepers,” said Yo-El Ju, MD, the study’s lead author.
The individuals with preclinical Alzheimer’s also spent more time napping. Frequent napping (three days or more per week) was associated with more than double the amyloid deposition.
Poor Sleep Can Worsen Symptoms of Alzheimer’s
Sleep problems are common among Alzheimer’s patients: undersleeping, oversleeping, sundowning, napping. Unfortunately, a lack of healthy sleep can make symptoms worse, according to research of tau, another brain protein linked to Alzheimer’s.
In healthy people, tau can exist at normal levels in the brain. However, it can also clump together, creating tangles that pressure and injure nearby brain tissue, leading to cognitive decline. In individuals with Alzheimer’s, the growth of these tau clumps can accelerate the spread of the disease, and sleeplessness appears to be something that drives that growth.
During the day, tau gets released as you use your brain. At night, while you sleep, your brain clears away tau. When you don’t get enough sleep, the tau isn’t sufficiently cleared away, leading to the buildup that can create tangles. For individuals with Alzheimer’s, tau tangles can clump in hippocampus before spreading to other regions of the brain, impacting the person’s memory and ability to think clearly.
Researchers have confirmed that sleep deprivation alone can speed the growth of these toxic tau clumps. In one study of mice, researchers increased levels of tau in the hippocampi of the mice. Then, over a period of four weeks, they allowed half of the mice to sleep normally, while disturbing the sleep of the other group, creating conditions of sleep deprivation. By the end of the study, the tau tangles had spread significantly further in the sleep-deprived mice.
Sleep deprivation also increases tau levels in humans, by about 50 percent. Findings like these reiterate the importance of getting sufficient sleep on a regular basis in order to preserve brain health.
Tips for Getting Better Sleep, for a Better Brain
Good sleep is essential for good health, especially brain health. Adopt these habits to enjoy better sleep on a more regular basis.
1. Make Time for Sleep.
Does your current schedule allow for you to conceivably get at least 7 hours of sleep at night? You may not be able to adjust your school or work hours, but see what you can do to reschedule leisure activities, hobbies, and exercise so you have at least 30 minutes free to wind down before bed at night. Set a sleep schedule and stick to it, even on weekends.
2. Take a Goldilocks Approach to Sleep.
Healthy sleep is the “just right” amount of sleep. If you’re an adult, that can range anywhere from 6 to 9 hours of sleep, although it’s commonly 7 to 7.5. If you miss out on sleep during the week, don’t try to make up for it on the weekend by sleeping in. The idea of “catching up” on sleep isn’t backed up by science, and long sleep (defined as 9 hours or more) is equally linked to a 2.5 times higher risk of dementia and Alzheimer’s as short sleep is.
3. Don’t Nap Too Much.
Just as you shouldn’t sleep in, don’t overindulge in naps, either. Nap too long during the day, and you’ll make it harder for yourself when it’s time to fall asleep at night. By following a regular sleep schedule, and avoiding naps, you’ll eventually train your brain to get all your sleep in at night. That’s the best way to ensure you enjoy your maximum number of sleep cycles, and receive a full amount of REM sleep.
4. Make Your Bedroom More Sleep-Friendly.
Once you’ve created the time to sleep, you can create the space for sleep. To prime your bedroom for deep sleep, do these three things:
- Keep It Cool: Keep the thermostat in the low- to mid-60 degrees Fahrenheit. Help your body cool down with temperature-regulating bedding and by sleeping naked.
- Keep It Dark: Remove all electronics from the room, and face clocks away from you. Use blackout curtains. Automate the light levels in your room by using smart lights that mimic that natural rising and setting of the sun.
- Keep It Quiet: If you sleep with a snorer or pet, block out the noise with a white noise machine, ambient noise playlist, or noise-cancelling headphones.
5. Watch Your Electronics.
You may think watching Netflix on your TV, or scrolling Instagram on your phone, helps you relax before bed, but you’d be wrong. Activities like these are emotionally activating, and in the case of social media, linked to increased levels of anxiety, depression, and insomnia. Worse, your brain confuses the blue light these devices emit as sunlight, so it delays melatonin production and keeps you awake. Limit your electronic use at night, especially in the hour or two before bedtime.