How much sleep do you need?

The question I’m asked most, and the one I’m most reluctant to answer (unless you’ve got at least 30 minutes to kill), is: “How many hours of sleep do I need?”

This is like asking how many glasses of water you should drink per day. The popular answer seems to be “eight”—but whom does that number apply to? Professional athletes at the height of training, or sedentary office workers? Teenagers living in Arizona or great-grandmothers living in the Amazon jungle?  I can’t imagine that they all need exactly the same amount of water. Just as I can’t imagine everyone needing the same amount of sleep.

I do a deep dive into how sleep works (and how you can get to know yours) in my upcoming book Hello Sleep: The Science and Art of Overcoming Insomnia Without Medications. Let’s hone in on some highlights here to answer the million-dollar question: How many hours of sleep do you really need?

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The short answer: As many hours as your body wants to and is able to sleep.

The long answer: To understand sleep need, we need to review a few concepts and bust a few myths.

1. Myth: Everyone needs 8 hours of sleep.

In 2015, the National Sleep Foundation published a set of guidelines for appropriate amounts of sleep for each age group. Their recommendations were based on expert opinions from a panel of doctors and scientists from various disciplines, and currently serves as the go-to reference for how much sleep we should all get. Notice this: not only does the amount of appropriate sleep differ by age group, there is also considerable range within each age group. For young adults, as few as 7 hours could be fine, and as many as 11 hours. For older adults, you could get as few as 5 hours, and as many as 9 hours.

National Sleep Foundation (2015).

This reflects natural individual differences in how much sleep we each need. Not everyone needs 8 hours—some need more, and some do just fine on fewer.

So how to figure out how many hours you need? Well, how many hours are you consistently able to sleep? If you are falling asleep as soon as your head hits the pillow every night, and you often doze off in class or while watching TV…you probably need more nighttime sleep than you are getting*. However, if you take a long time to fall asleep, or you’re consistently awake for big chunks of time during the night, and you can’t nap even if you tried…you likely need less sleep than you think.  

Your body knows how much sleep you need, and it will tell you so by making you feel sleepy (not tired, but sleepy) when you haven’t gotten enough. Just like your body knows how much water it needs, and will tell you so by making you feel thirsty when you haven’t gotten enough. Your only job is to notice these cues from your body. Don’t overpower the natural sleepiness you feel by playing Grand Theft Auto late into the night, and don’t go to bed before you’re sleepy just because it’s “a decent bedtime.”

2. Myth: Good quality sleep means uninterrupted sleep.

“Ok, so I don’t necessarily need 8 hours. But if I wake up during the night, that must be breaking up my sleep and reducing its quality, right?”

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Probably not. Did you know that good sleepers wake up 10-15 times per night? They don’t tend to remember most of those awakenings, but they do occur, and that’s a good thing! If you truly sleep like a log and never stir at all during the night, I would be worried, because that’s what someone in a coma would look like, not someone who is sleeping well.

Good quality sleep is composed of several different stages that cycle several times throughout the night (more on that in a future post), and about half of the night is supposed to be spent in light stages of sleep, with another 20-25% spent in the very active stage of rapid eye movement (REM) sleep. During these stages and when you’re transitioning between stages, your brain often pops up into wakefulness, like a whale surfacing after a dive.

Even if a few of these awakenings last long enough for you to remember in the morning, that’s okay! Your brain will simply resume what it was doing in sleep land.

3. Myth: If I’m often tired, I must be sleep-deprived.

Tired and sleepy are not the same thing. Tired means feeling worn out, low on energy, “done for the day,” exhausted. Sleepy means your eyelids are heavy, your head is nodding, and you’ve read the same sentence three times and keep not following it. If you’re often sleepy or falling asleep at inappropriate times—during meetings and classes, while driving, while reading or watching TV—you are likely sleep deprived. But if you’re often tired, without actually being sleepy, you may be stressed, bored, dehydrated, over-worked, under-worked…there are many other things to blame besides sleep!

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4. Myth: If I have insomnia, I must be sleep-deprived.

Probably not. If you were sleep-deprived, you would be sleepy, and if you are sleepy, you likely wouldn’t have insomnia. This is somewhat oversimplifying, but the general rule of thumb tends to hold true*. Actually, if you have insomnia and are worried about sleep deprivation, this belief may actually worsen your insomnia. Believing that you are sleep-deprived may drive you to spend more time in bed or try harder to fall asleep, which only adds performance pressure and decreases your likelihood of falling asleep.

5.  Fact: You earn your sleep by being awake and active.

Just as you can earn more appetite by exercising, you can earn more sleepiness by being awake and active. In fact, for every moment that you’re awake (and bonus points if you’re burning energy by moving your body), you are saving up “sleep drive.” The more sleep drive you have saved up by the end of the day, the more you have to cash in for good quality sleep.

So, I would in fact reverse the question that we began with. Instead of asking, “How much sleep do I need in order to function well during the day,” we should ask, “How much wakefulness do I need in order to sleep well at night?” If you listen to your body’s cues, instead of forcing it to sleep more or less than it wants to, you will be able to strike the perfect balance for both good sleep and good wake.

*One caveat about daytime sleepiness: If you are often sleepy during the day, it might be because you’re not getting enough sleep at night, but it also might mean that you have a sleep-related disorder like sleep apnea or hypersomnia. These are serious health conditions and you should ask your doctor about it if you are sleeping 8+ hours/night and still feeling often sleepy during the day.