table of contents
“The greatest life insurance policy that I know of—and it is universally available, largely free, and mostly painless—is that thing called a night of sleep. So, I’ll gift it to myself every single night.”
Dr. Matt Walker
Why do we sleep?
Did you sleep well? It’s often the first question we hear—or ask ourselves—in the morning. But what does that even mean? Are you thinking about how many hours you got, or how calm and undisturbed your night was?
The truth is, without sleep, nothing works. It’s when your body repairs, your brain resets, and your emotions settle. And yet, we’re the only species that chooses to skip sleep. For work, social plans—or just one more Netflix episode.
On average, we sleep 90 minutes less than we should. And that’s not just about feeling tired. It speeds up aging, weakens the immune system, and raises the risk of serious health problems like heart disease and cancer.
Good sleep doesn’t just make you feel better—it helps you live longer and healthier.
And you know the difference: after a bad night, everything feels harder. But after a good one? You’re clearer, stronger, and life feels lighter.
Sleep isn’t a luxury. It’s your daily investment in health, energy, and your longevity.
What happens when we sleep?
| Function | What Happens During Sleep |
|---|---|
| Body repair & recovery | Damaged tissues are repaired, muscles are rebuilt, and recovery hormones are released — it’s your body’s nightly maintenance shift. |
| Energy conservation | Metabolism slows down to save energy for the next day, like switching to low-power mode. |
| Brain detox | The brain clears out waste like beta-amyloid, reducing risks linked to conditions like Alzheimer’s. |
| Memory & learning | Your brain organizes and stores the day’s information, helping you retain and understand what you’ve learned. |
| Heart recovery | Heart rate and blood pressure drop, giving your cardiovascular system a much-needed break. |
| Immune system boost | Infection-fighting proteins are produced, strengthening your immune defenses and reducing inflammation. |
| Circadian rhythm reset | Your internal body clock syncs, helping regulate sleep-wake cycles, mood, digestion, and energy. |
| Emotional processing & stress | Sleep helps balance emotions and reduce stress by calming the brain and sorting through emotional input. |
| Hormone regulation | Key hormones for appetite, stress, and blood sugar are stabilized — helping prevent cravings, mood swings, and imbalances. |
How much sleep do we need?
Your sleep-need isn’t static—it changes with age as well as it differes between people. A 2018 study showed this: newborns need up to 17 hours of sleep a day, adults 7-9 hours to be at their best. As we get older total sleep time often decreases, not because we need less sleep but because we can’t get deep, restorative sleep.
But it’s not just about how long you sleep—quality and consistency are just as important. The study says maintaining good sleep habits is just as important as sleep duration for overall health and wellbeing.
Keep on reading
Learn how Dr. Matt Walker defines good sleep through the four key macros—QQRT:
Quantity, Quality, Regularity, and Timing. Mastering these factors can help you sleep better, strengthen your body, sharpen your mind, and improve your overall health.
Do woman need more sleep than men?
According to an American study, women sleep an average of 11 minutes longer per night than men, but their sleep is often more interrupted and of lower quality. Hormonal changes, menstruation, pregnancy, menopause, and caregiving responsibilities lead to more awakenings and fragmented sleep.
Although women sleep longer, men often experience more uninterrupted and consolidated sleep, which can result in better recovery. The study highlights that sleep quality and consistency are just as important as duration.
Read the full study here.
Sleep stages:
Sleep has two main phases: NREM and REM. NREM includes three stages (N1, N2, and N3), and REM is the stage where most dreaming occurs. Sleep happens in 90-minute cycles that include all four stages. A full night’s sleep usually consists of 4 to 6 of these cycles, giving the body and brain time to recover, repair, and process the day.
| Stage | Type | What happens | Why it’s important |
|---|---|---|---|
| N1 | Light sleep | You drift between being awake and asleep. Muscles relax, and breathing slows. Lasts 1–5 minutes. | Prepares your body and mind for deeper sleep. |
| N2 | Light sleep | Heart rate slows, body temperature drops, and brain activity decreases. Lasts 10–25 minutes. | Helps your brain process and store information. |
| N3 | Deep sleep | The deepest and most restorative sleep. Breathing slows, and tissue repair begins. Lasts 20–40 minutes. | Vital for physical recovery and boosting the immune system. |
| REM | Dream sleep | Your brain becomes highly active, dreams occur, and your body is temporarily paralyzed. Repeats every 90 minutes. | Supports memory, learning, emotional balance, and creativity. |
How do I get more REM sleep?
REM sleep occurs in every sleep cycle, but it gradually becomes longer and more dominant as the night progresses. Early in the night, REM sleep lasts only a few minutes, but in the second half of the night, it can extend to 30-60 minutes per cycle.
This means that if you cut your sleep short, you miss out on the longest REM periods, which are essential for memory, learning, and emotional regulation. That’s why both sleep quality and duration are crucial for getting enough REM sleep.
Sleep enough: 7-9 hours a night as REM cycles get longer the longer you sleep.
Stick to a sleep schedule: Go to bed and wake up at the same time every day to regulate your body’s sleep wake cycle.
Limit alcohol: Alcohol can break up your REM sleep.
Manage stress: High stress can reduce REM sleep. Try yoga, meditation or deep breathing.
Make your bedroom sleep friendly: Keep your bedroom cool, dark and quiet to avoid interruptions.
No screens before bed: Blue light from phones or laptops can delay REM sleep by suppressing melatonin.
Exercise daily: Moderate exercise during the day helps with sleep including REM. Avoid vigorous exercise before bed.
No single sleep stage is more important than the others—each plays a unique and essential role in maintaining physical and mental health. While REM sleep is crucial for memory, learning, and emotional processing, deep sleep is equally vital for physical restoration and immune function.
How do I get more deep sleep (N3)?
Deep sleep is the stage where your body repairs itself, strengthens memory, and resets for the next day. It should make up about 13–23% of your total sleep, which equals 55–110 minutes per night.
That’s easier said than done — deep sleep naturally decreases with age, often dropping to just 10–15% in older adults. If you’re tracking your sleep and consistently falling below this range, it might be time to adjust your habits.
| Tip | Why it helps |
|---|---|
| Stick to a routine | A consistent bedtime helps your body settle into deeper sleep. |
| Ditch screens before bed | Blue light blocks melatonin, delaying deep sleep. |
| Exercise—but not too late | Movement boosts deep sleep, but intense workouts before bed can disrupt it. |
| Create a sleep-friendly room | Keep it cool (16-18°C), dark, and quiet to minimize interruptions. |
| Avoid caffeine & alcohol | Both interfere with deep sleep quality. |
| Try magnesium or glycine | Studies suggest they can enhance sleep depth and efficiency. |
Sleep stages summary
Each sleep stage has a unique role — from helping the body relax to repairing tissues, strengthening memory, and processing emotions. REM sleep gets longer later in the night, so 7–9 hours of sleep is important. Deep sleep is most restorative but decreases with age. Support both by keeping a regular routine, managing stress, avoiding screens before bed, and creating a calm sleep environment.
“Beauty sleep” – does lack of sleep age your skin?
We’ve all been there: that feeling in your body after a bad night’s sleep or during periods of chronic sleep deprivation. The reasons can be many—a baby that won’t sleep, work stress, or something else entirely. And then there’s the comment: “You look so tired!” Unfortunately it’s often true after a bad night’s sleep.
A study from Karolinska Institutet in Stockholm looked at how sleep deprivation affects your face and how others perceive those changes.
In the study, 10 people were photographed after a full night’s sleep and again after 31 hours of sleep deprivation. 40 observers then rated the photos for fatigue and specific facial features such as droopy eyelids, dark circles under the eyes, pale skin and red eyes.
The results showed that sleep deprivation has a big impact on your face. Sleep deprived people looked more tired, with droopier eyelids, puffier and redder eyes, darker under-eye circles and paler skin. They also looked sadder.
Best sleeping position for longevity
The way you sleep can affect your posture, breathing, and even how well your body recovers overnight. While individual comfort plays a big role, some positions may offer more long-term health benefits than others.
Back sleeping: Sleeping on the back keeps the spine aligned and reduces pressure on joints. It also minimizes facial compression, which may slow wrinkle formation. However, this position can worsen snoring and sleep apnea, potentially disrupting sleep quality.
Side sleeping: Side sleeping is often recommended for its benefits on spinal alignment and breathing. It may also support the brain’s natural cleansing processes during sleep, which could play a role in reducing the risk of neurodegenerative diseases.
Stomach sleeping: This position is generally the least recommended. It can strain the neck and spine, leading to discomfort over time. While it may help reduce snoring for some, it does not support long-term musculoskeletal health.
Sleep and skin
Sleep is essential for skin health and longevity. While you sleep, your body repairs damage, boosts collagen production, and improves blood flow — all of which help keep your skin smooth, radiant, and youthful. Lack of sleep, on the other hand, speeds up skin aging. Poor sleep increases cortisol, which breaks down collagen and leads to wrinkles, dullness, and sagging. Over time, it also weakens the skin’s ability to repair itself and protect against environmental stress.
Explore our Rewind Liquid Collagen — a premium formula with highly absorbable collagen peptides and 7 carefully selected supporting ingredients that promote skin health from within, including glycine which not only supports collagen structure but is also backed by studies showing it may improve sleep quality.
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What do the experts say?
Bryan Johnson, known for his extremely healthy lifestyle, has achieved something extraordinary: 8 months of 100% perfect sleep, which has been measured as the best sleep ever recorded.
Through his optimized routines, Bryan has proven how lifestyle changes can lead to incredible sleep quality.
“Sleep is the most important thing a human does on a daily basis”
Bryan Johnson
Bryan Johnson’s perfect sleep results are just one part of his extraordinary health journey. He follows a rigorous protocol called the Blueprint, which includes diet, exercise, and advanced technology to reverse aging and optimize every aspect of his body.
Read more here: Bryan Johnson Blueprint protocol
QQRT: the 4 macros for good sleep
What is a good night’s sleep? Most of us know the question, “Did you sleep well?” But what do we actually measure when we answer that? We tend to focus only on the quantity of sleep without giving much thought to its quality or other factors. Often, the answer could easily be, “Yeah, I got my 8 hours.”
However, according to Dr. Matt Walker, sleep is far more complex than that. He conceptualised sleep into four important macro factors, collectively known as QQRT.
QQRT: Quantity | Quality | Regularity | Timing
Q | Quantity
Quantity refers to the length of sleep. Many years of research suggest that an adult human needs about 7-9 hours of sleep per night. However, studies also show that, on average, people need 90 minutes more sleep than they actually get. Dr. Matt Walker’s answer to how much sleep we need is therefore simple: “90 minutes more.”
Q | Quality
Quality is about the continuity of sleep—did you wake up often, and was your sleep fragmented? For example, maybe you were in bed for 9 hours but only slept for 7. In this case, the quality of sleep becomes low. Sleep efficiency is the percentage of time you spend in bed that you were actually sleeping. If you spent 8 hours in bed but only slept for 6, your efficiency score would be 75%.
Dr. Matt Walker identifies good sleep as having an efficiency score above 85%. Anything below 85% indicates sleep that needs improvement, often due to waking up too frequently during the night.
R | Regularity
Regularity is about maintaining consistent bedtimes and wake-up times every day. Dr. Matt Walker suggests aiming for consistency with a buffer of +/- 30 minutes to stabilize your body’s circadian rhythm. A major study from 2023 confirms the importance of sleep regularity. The study, conducted using data from over 60,000 participants in the UK Biobank, examined how consistent bedtimes and wake-up times affect mortality.
A major study from 2023 confirms the importance of sleep regularity. The study, conducted using data from over 60,000 participants in the UK Biobank, examined how consistent bedtimes and wake-up times affect mortality.
- Participants with regular bedtimes and wake-up times had a 20%-48% lower risk of all-cause mortality compared to those with irregular sleep schedules.
- Regularity also reduced the risk of death from heart disease with 22%-57% and cancer with 16%-39%.
This study highlights that consistency in sleep patterns—going to bed and waking up at the same time each day—is a crucial factor for health and longevity.
T | Timing
Timing is all about aligning your sleep schedule with your chronotype and understanding your body’s circadian rhythm—the natural 24-hour internal clock that regulates your sleep-wake cycle, energy levels, and other biological processes.
What is your chronotype?
Your chronotype is your natural preference for sleeping early or late. It’s a hardwired trait, gifted to you at birth, and very difficult to change.
| Chronotype | Typical Bedtime | Typical Wake Time |
|---|---|---|
| Extreme Morning Type | 8-9 PM | 5 AM or earlier |
| Morning Type | 10 PM | 7 AM |
| Neutral Type | 11 PM | 8 AM |
| Evening Type | Midnight | 9 AM |
| Extreme Evening Type | 2-3 AM | Mid-morning or later |
Sleeping out of sync with your chronotype—such as being a night owl who has to wake up early for work—can result in poor-quality sleep, even if you get the recommended 7-9 hours. Understanding your chronotype can help you better tailor your sleep schedule to your natural rhythm.
Summing up QQRT
A good night’s sleep depends on four key factors: Quantity, Quality, Regularity, and Timing. Most people need more sleep than they get, with consistent, uninterrupted rest aligned to their natural rhythm. Balancing all four supports better health and longevity.
NMN and sleep: New study reveals improved sleep quality in older adults
A new human trial suggests that NMN may enhance sleep quality in middle-aged and older adults. In a 12-week double-blind, placebo-controlled study, participants who took 300 mg of NMN daily experienced fewer nighttime awakenings, better sleep efficiency, and reduced daytime fatigue. The findings indicate that NMN may support sleep by increasing NAD+ levels and counteracting age-related cellular changes. Read more about the study here: NMN Sleep Quality Human Trial: Breakthrough Results for Aging Adults
References
- Chaput, J.-P., Dutil, C., & Sampasa-Kanyinga, H. (2018). Sleeping hours: what is the ideal number and how does age impact this? Nature and Science of Sleep, 10, 421–430. https://doi.org/10.2147/NSS.S163071
- Burgard, S. A., & Ailshire, J. A. (2013). Gender and Time for Sleep among U.S. Adults. American Sociological Review, 78(1), 51–69. https://doi.org/10.1177/0003122412472048
- Sundelin, T., Lekander, M., Kecklund, G., Van Someren, E. J. W., Olsson, A., & Axelsson, J. (2013). Cues of Fatigue: Effects of Sleep Deprivation on Facial Appearance. Sleep, 36(9), 1355–1360.
- Windred, D. P., Burns, A. C., Lane, J. M., Saxena, R., Rutter, M. K., Cain, S. W., & Phillips, A. J. K. (2023). Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study. Sleep, 47(1), zsad253. https://doi.org/10.1093/sleep/zsad253
- Bryan Johnson: How I Fixed My Terrible Sleep. Blueprint. Available at: https://blueprint.bryanjohnson.com/blogs/news/how-i-fixed-my-terrible-sleep
- Dr. Matt Walker: The Biology of Sleep & Your Unique Sleep Needs. Huberman Lab Podcast (YouTube). Available at: https://www.youtube.com/watch?v=-OBCwiPPfEU&t=5409s
- Morningness-Eveningness Questionnaire (MEQ). Discover your chronotype here: https://qxmd.com/calculate/calculator_829/morningness-eveningness-questionnaire-meq
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