Sleep for longevity

You walk down the stairs, and the first question that greets you—whether from yourself or your partner—is: Did you sleep well? But before you answer, what exactly do you base your response on? Do you measure it by how many hours you spent asleep? Or is it about how restful and uninterrupted your sleep felt?

“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

In this article

Why do we sleep | What happens when we sleep | How much sleep do we need | Do woman need more sleep than men | Sleep stages | How do I get more REM sleep | “Beauty sleep” – does lack of sleep age your skin | Sleep and skin | What do the experts say | QQRT: the 4 macros for good sleep

Why do we sleep?

We spend a third of our lives lying down, doing nothing, but why do we do so when there’s so much else we could be doing?The answer is simple—sleep isn’t wasted time, it’s survival. It’s when your body repairs, your brain resets, and your emotions find balance. Without it everything breaks down.

We are the only species that voluntarily sacrifices sleep—for work, socialising, or even just one more Netflix episode. And the fact is, on average, we sleep 90 minutes less than we should every night.

So why don’t we prioritise sleep when science tells us that neglecting it doesn’t just make us tired? It ages us, weakens our immune system and increases the risk of chronic diseases like heart disease and cancer. Sleep deprivation doesn’t just affect how we feel in the morning—it affects how long and how well we live.

Because when we sleep we’re buying into our longevity. Sleep isn’t just rest—it’s one of the best tools we have to live longer, healthier, happier lives.

And if you’ve ever had bad sleep you know the difference. You wake up feeling drained, unfocused and irritable. But when you start sleeping well again everything changes. Your mind is clearer, your body is stronger and life is just easier.

So why not give your body what it really needs? Sleep isn’t a luxury it’s an investment in your health, energy and future.

What happens when we sleep?

You save energy for tomorrow | During sleep, your metabolic rate slows down, helping the body conserve energy for the next day. It’s like putting your body in low-power mode, saving resources so you can function efficiently when you wake up.

Your brain gets a deep clean | While you sleep, your brain clears out toxins—like beta-amyloid, which is linked to Alzheimer’s—through the glymphatic system. It’s like giving your brain a nightly detox, flushing out the junk so it stays healthy and sharp.

Your mind organizes and strengthens memories | Have you ever noticed how things just click after a good night’s sleep? That’s because your brain is organizing, storing and strengthening everything you learned during the day. Sleep is when your mind makes sense of new information so you think more clearly and remember more when you wake up.

Your heart gets a break | Your heart works nonstop, but sleep is when it slows down and recovers. Blood pressure drops, stress decreases, and your cardiovascular system resets, reducing strain on your heart. Track your sleep, and you’ll see your heart rate naturally lower at night, giving it the rest it needs to stay strong.

Your immune system gets ready to defend you | When you don’t get enough sleep, your body becomes more vulnerable to illness. That’s because during sleep,your body produces infection-fighting proteins that strengthen your immune system and help combat inflammation. It’s your body’s way of building up defenses overnight, keeping you strong and healthy.

Your body’s internal clock resets | Sleep helps sync your circadian rhythm, the internal clock that controls everything from your energy to digestion. Without it you feel foggy, sluggish and out of whack—like jet lag, even if you haven’t left the house.

You process emotions and reset stress | Ever wake up and feel like everything makes more sense? That’s because sleep helps balance emotions and reduce stress. Your brain sorts through feelings and calms down which is why “sleeping on it” often leads to better decisions and a clearer head.

Hormone regulation | Sleep keeps your hormones in balance—reducing stress, regulating appetite, and stabilizing blood sugar. It’s like a nightly reset, keeping everything running smoothly. Without enough rest, things fall out of sync, leading to cravings, mood swings, and overall imbalance.

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 reading to 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.

You can read the full study here.

Sleep stages:

Sleep comes in 90 minute cycles of 4 stages, NREM and REM. A full night’s sleep has 4-6 of these cycles to fully recover:

How do I get more REM sleep?

REM sleep happens in longer chunks in the second half of the night so improving overall sleep quality and duration is key. Here are some tips to get more 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.

“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.

Sleep and skin

Sleep is essential for skin health and longevity. During sleep, your body repairs damage, boosts collagen production, and enhances blood flow, keeping your skin radiant and youthful.

However, lack of sleep accelerates aging. Increased cortisol levels from poor sleep break down collagen, leading to wrinkles, dullness, and sagging skin. Chronic lack of sleep also impacts skin longevity by reducing its ability to repair itself and resist environmental damage.

If you’re interested in learning more about collagen you can read more here:

• Liquid Collagen Benefits, Dosage and Possible Side Effects

• Is Liquid Collagen Better than Powder and Pills?

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.

• 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.

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.

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.

You might also find this study interesting: NMN Sleep Quality Human Trial: Breakthrough Results for Aging Adults

References:

1. 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
2. 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
3. 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.
4. 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

External links:

• 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