Why 7 Hours Sleep Is Not Enough

Sleep deprivation is more serious than you think. After 16 hours without sleep, the brain begins to fail and needs 7+ hours to reset cognitive performance.
Not enough sleep deprivation sticker - thumbnail thumbnail.

How Sleep-Deprived Are You, Really?

This is Dr. Matthew Walker. He’s a neuroscientist and sleep specialist, and is the Director of the Center for Human Sleep Science at UC Berkeley’s Department of Psychology. He’s also the author of the international bestseller “Why We Sleep”.

What does he want us to know?

Sleep deprivation is more serious than many people think it is. After about 16 hours without sleep, the brain begins to fail, and needs more than 7 hours of sleep to “reset” cognitive performance.

Note: note “seven or more”, but “more than seven”.

After ten days with only 7 hours sleep (per day), Dr. Walker points out, the brain is as dysfunctional as it would be after going without sleep for 24 hours.

Here’s the study that sparked a lot of Dr. Walker’s work:

The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From Chronic Sleep Restriction and Total Sleep Deprivation

Importantly, in Dr. Walker’s own words:

Three full nights of recovery sleep (i.e., more nights than a weekend) are insufficient to restore performance back to normal levels after a week of short sleeping❞

~ Dr. Matthew Walker

See also: Why You Probably Need More Sleep

Furthermore: the sleep-deprived mind is unaware of how sleep-deprived it is.

You know how a drunk person thinks they can drive safely? It’s like that.

You do not know how sleep-deprived you are, when you are sleep-deprived!

For example:

❝(60.7%) did not signal sleepiness before a sleep fragment occurred in at least one of the four MWT trials❞

Source: Sleepiness is not always perceived before falling asleep in healthy, sleep-deprived subjects

Sleep efficiency matters

With regard to the 7–9 hours band for optimal health, Dr. Walker points out that the sleep we’re getting is not always the sleep we think we’re getting:

❝Assuming you have a healthy sleep efficiency (85%), to sleep 9 hours in terms of duration (i.e. to be a long-sleeper), you would need to be consistently in bed for 10 hours and 36 minutes a night. ❞

~ Dr. Matthew Walker

At the bottom end of that, by the way, doing the same math: to get only the insufficient 7 hours sleep discussed earlier, a with a healthy 85% sleep efficiency, you’d need to be in bed for 8 hours and 14 minutes per night.

The unfortunate implication of this: if you are consistently in bed for 8 hours and 14 minutes (or under) per night, you are not getting enough sleep.

“But what if my sleep efficiency is higher than 85%?”

It shouldn’t be.If your sleep efficiency is higher than 85%, you are sleep-deprived and your body is having to enforce things.

Want to know what your sleep efficiency is?

We recommend knowing this, by the way, so you might want to check out:

Head-To-Head Comparison of Google and Apple’s Top Sleep-Monitoring Apps

(they will monitor your sleep and tell you your sleep efficiency, amongst other things)

Want to know more?

You might like his book:

Why We Sleep: Unlocking the Power of Sleep and Dreams

…and/or his podcast:

The Matt Walker Podcast

…and for those who like videos, here’s his (very informative) TED talk:

!

Prefer text? Click here to read the transcript 😎

Want to watch it, but not right now? Bookmark it for later 🔖

Enjoy!

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  • Stop Cancer 20 Years Ago

    Dr. Jenn Simmons shares vital tips on preventing cancer and inflammation, advocating for lifestyle changes and proactive health management at any age.

    Get Abreast And Keep Abreast

    This is Dr. Jenn Simmons. Her specialization is integrative oncology, as she—then a breast cancer surgeon—got breast cancer, decided the system wasn’t nearly as good from the patients’ side of things as from the doctors’ side, and took to educate herself, and now others, on how things can be better.

    What does she want us to know?

    Start now

    If you have breast cancer, the best time to start adjusting your lifestyle might be 20 years ago, but the second-best time is now. We realize our readers with breast cancer (or a history thereof) probably have indeed started already—all strength to you.

    What this means for those of us without breast cancer (or a history therof) is: start now

    Even if you don’t have a genetic risk factor, even if there’s no history of it in your family, there’s just no reason not to start now.

    Start what, you ask? Taking away its roots. And how?

    Inflammation as the root of cancer

    To oversimplify: cancer occurs because an accidentally immortal cell replicates and replicates and replicates and takes any nearby resources to keep on going. While science doesn’t know all the details of how this happens, it is a factor of genetic mutation (itself a normal process, without which evolution would be impossible), something which in turn is accelerated by damage to the DNA. The damage to the DNA? That occurs (often as not) as a result of cellular oxidation. Cellular oxidation is far from the only genotoxic thing out there, and a lot of non-food “this thing causes cancer” warnings are usually about other kinds of genotoxicity. But cellular oxidation is a big one, and it’s one that we can fight vigorously with our lifestyle.

    Because cellular oxidation and inflammation go hand-in-hand, reducing one tends to reduce the other. That’s why so often you’ll see in our Research Review Monday features, a line that goes something like:

    “and now for those things that usually come together: antioxidant, anti-inflammatory, anticancer, and anti-aging”

    So, fight inflammation now, and have a reduced risk of a lot of other woes later.

    See: How to Prevent (or Reduce) Inflammation

    Don’t settle for “normal”

    People are told, correctly but not always helpfully, such things as:

    • It’s normal to have less energy at your age
    • It’s normal to have a weaker immune system at your age
    • It’s normal to be at a higher risk of diabetes, heart disease, etc

    …and many more. And these things are true! But that doesn’t mean we have to settle for them.

    We can be all the way over on the healthy end of the distribution curve. We can do that!

    (so can everyone else, given sufficient opportunity and resources, because health is not a zero-sum game)

    If we’re going to get a cancer diagnosis, then our 60s are the decade where we’re most likely to get it. Earlier than that and the risk is extant but lower; later than that and technically the risk increases, but we probably got it already in our 60s.

    So, if we be younger than 60, then now’s a good time to prepare to hit the ground running when we get there. And if we missed that chance, then again, the second-best time is now:

    See: Focusing On Health In Our Sixties

    Fast to live

    Of course, anything can happen to anyone at any age (alas), but this is about the benefits of living a fasting lifestyle—that is to say, not just fasting for a 4-week health kick or something, but making it one’s “new normal” and just continuing it for life.

    This doesn’t mean “never eat”, of course, but it does mean “practice intermittent fasting, if you can”—something that Dr. Simmons strongly advocates.

    See: Intermittent Fasting: We Sort The Science From The Hype

    While this calls back to the previous “fight inflammation”, it deserves its own mention here as a very specific way of fighting it.

    It’s never too late

    All of the advices that go before a cancer diagnosis, continue to stand afterwards too. There is no point of “well, I already have cancer, so what’s the harm in…?”

    The harm in it after a diagnosis will be the same as the harm before. When it comes to lifestyle, preventing a cancer and preventing it from spreading are very much the same thing, which is also the same as shrinking it. Basically, if it’s anticancer, it’s anticancer, no matter whether it’s before, during, or after.

    Dr. Simmons has seen too many patients get a diagnosis, and place their lives squarely in the hands of doctors, when doctors can only do so much.

    Instead, Dr. Simmons recommends taking charge of your health as best you are able, today and onwards, no matter what. And that means two things:

    1. Knowing stuff
    2. Doing stuff

    So it becomes our responsibility (and our lifeline) to educate ourselves, and take action accordingly.

    Want to know more?

    We recently reviewed her book, and heartily recommend it:

    The Smart Woman’s Guide to Breast Cancer – by Dr. Jenn Simmons

    Enjoy!