From sleep podcasts and media interviews to cocktail parties and my kids’ sports events, I often hear that question. That’s probably the #1 question that people of all ages ask me! By now, I’ve crafted a simple answer, with the gist being to focus on sleeping cooler to get deep, restorative sleep.
That inevitably leads to the second most frequently asked question that I hear back in response.
“But...I thought we were supposed to get eight hours of sleep? Don’t all doctors say something’s wrong if I’m not sleeping for eight full hours a night?”
So when I came across new research confirming that it really is all about sleep quality, not sleep quantity, I was thrilled! It’s a huge breakthrough to see other scientists confirm that deep sleep is vital, and 6-8 hours sleep is sufficient.
Deep Sleep May Prevent Dementia
Gone are the days of a blanket statement to “get eight hours” without providing further context.
Did You Know: Research affirms that deep sleep may also help protect against Alzheimer’s disease. Alzheimer’s disease afflicts more than 40 million people worldwide, which is expected to rise. While Alzheimer’s disease is currently untreatable, deep sleep may offer a prevention strategy.
Take a look at a few sleep studies showing that deep sleep can prevent dementia (while inadequate sleep could raise your risk):
In the first study, scientists revealed how deep sleep can protect against Alzheimer’s disease. We’ll dive into the science behind "beta-amyloid" below, but in this study, a team of scientists set out to answer a question:
Can I look into your future, and can I accurately estimate how much beta-amyloid you will accumulate over the next two years, the next four years, the next six years, simply based on your sleep tonight
Can I look into your future, and can I accurately estimate how much beta-amyloid you will accumulate over the next two years, the next four years, the next six years, simply based on your sleep tonight.
Dementia Sleep Study Results
The results, published in the journal Current Biology, found that people who got less deep sleep had more beta-amyloid.  Researchers looked for the slow electrical waves that signal deep sleep, using brain scans to monitor levels of beta-amyloid in each participant for up to six years.
The results indicate that humans have a specific “sleep signature” that can help scientists better understand where someone would sit on the Alzheimer's risk trajectory in the future.
In the next sleep study, researchers at Harvard Medical School studied more than 2,800 individuals ages 65 and older.  The results, published in the journal Aging, found that individuals who slept fewer than five hours per night were twice as likely to develop dementia, and twice as likely to die, compared to those who slept six to eight hours per night.
Finally, in a third study, European researchers found that sleeping less than six hours a night could raise your chances of developing dementia later in life. 
The study, published in Nature Communications, examined data from almost 8,000 participants and found that consistently sleeping six hours or less at age 50, 60, and 70 was associated with a 30% increase in dementia risk compared to a normal sleep duration of seven hours.
How Deep Sleep Reboots Your Brain
The studies above all looked into things like A? amyloid plaque build-up, sleep, and dementia.
What does that mean in plain English? Well, when your brain doesn’t get enough rest, your brain has a harder time cleaning and rebooting itself.
In more scientific terms, amyloid plaque build-up contributes to poor sleep in older adults through its direct impact on sleep-wake regulator brain regions.  There is also evidence of an association of A? accumulation disrupting the circadian rhythm and sleep pattern in cognitively normal adults.
Extended wakefulness and/or sleep deficiency can cause more “bad stuff” to build up, thereby increasing the risk of Alzheimer's disease.
Or as Andrew E. Budson, MD, wrote in this Harvard Medical blog post,  a lack of quality sleep means “your brain won’t have enough time to drain away beta-amyloid and other substances” that continue to accumulate, day after day, until they cause dementia.
How can you prioritize deep, restful sleep, without necessarily adhering to the 8-hour myth as a guideline? You must be mentally prepared to rest, of course!
Read More: The Benefits of Naps, Drawbacks & More
The first step to getting deeper sleep is knowing your chronotype and respecting the stages of sleep. This starts with honoring your inherent sleep schedule, giving you a chance to get more deep sleep right off the bat. The second step is cooling down, literally.
That’s because your body also needs a physical change to signal that it’s the appropriate and safe time for sleep. This change is a drop in temperature.
Learning how to get more deep sleep will take different methods for different people. The big takeaway is that if you’re focused on taking care of yourself, optimizing your longevity and wellness, and looking for prevention strategies to keep your brain sharp, you must prioritize deep sleep.
Remember, it’s never too late to choose healthy bedtime habits to promote brain health and achieve deep sleep!
 Winer, J. R., Mander, B. A., Kumar, S., Reed, M., Baker, S. L., Jagust, W. J., & Walker, M. P. (2020). Sleep Disturbance Forecasts ?-Amyloid Accumulation across Subsequent Years. Current Biology, 30(21), 4291-4298.e3. View Study
 kconvery. (2021, August 31). Understanding the Connection Between Sleep and Dementia. Harvard Pilgrim Health Care - HaPi Guide. View Study
 Bryant, E. (2021, April 27). Lack of sleep in middle age may increase dementia risk. National Institutes of Health (NIH). View Study
 Ju, Y.-E. S., Lucey, B. P., & Holtzman, D. M. (2013). Sleep and Alzheimer disease pathology—a bidirectional relationship. Nature Reviews Neurology, 10(2), 115–119. View Study
 MD, A. E. B. (2021, May 3). Sleep well — and reduce your risk of dementia and death. Harvard Health. View Study