Only 5 Hours of Sleep? It’s Worse For You Than You Think

Think you’re able to function fine on only five hours of sleep? We’ll explain how your brain is tricking you and how to use RISE to get the sleep you need.
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Jamie Zeitzer, PhD, Rise Science Scientific Reviewer
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We bring sleep research out of the lab and into your life. Every post begins with peer-reviewed studies — not third-party sources — to make sure we only share advice that can be defended to a room full of sleep scientists.
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Updated Regularly
We regularly update our articles to explain the latest research and shifts in scientific consensus in a simple and actionable way.
Woman sleeping at desk in front of laptop after only five hours of sleep.

There are many possible reasons why you’re a five-hour sleeper, some by choice and some due to necessity. Perhaps you think you can accomplish more when you sleep less. Or maybe you consider short-sleeping a badge of honor. Similarly, a demanding work schedule or a teething newborn may be what’s getting in the way of a good night’s sleep.

The point is, many of us think we can survive (if not thrive) on five hours of sleep (or four, six, or seven). And while that may be a dream when life is busy, it’s, sadly, not one that’s possible. Denying yourself the sleep you need — and accumulating sleep loss in the process — is the surest way to short-circuit every aspect of your life.

Ahead, we show you how only five hours of sleep is synonymous with sleep deprivation and what that means for your waking life. Plus, we’ll show you how the RISE app can tell you the amount of sleep you should be getting instead, and how exactly you can get it.

Is 5 Hours of Sleep Enough?

After one night — or several successive nights — of short sleep (defined as less sleep than you biologically need — more on that later), we overrate our ability to stay awake and alert. You probably think, “Hey, I’m actually not doing so bad after all!” The reality is, you’re actually doing very poorly!  

Here are five compelling reasons to dispel that common misconception, and show we don’t cope as well as we think:

1. Your Actual Sleep Need is Definitely More Than Five Hours

There are a few lucky ones who can survive on little sleep, but they are very — very — few and far between. As Dr. Thomas Roth says in Matthew Walker’s book, Why We Sleep, “The number of people who can survive on 5 hours of sleep or less without any impairment, expressed as a percent of the population, and rounded to a whole number, is zero.” 

Walker elaborates, “It is far, far more likely that you will be struck by lightning (the lifetime odds being 1 in 12,000) than being truly capable of surviving on insufficient sleep thanks to a rare gene.”

Getting only five hours of shut-eye means you aren’t meeting your biological sleep need — an individual trait that’s genetically determined, like your height or eye color. Despite what you hear, it’s not simply eight hours for everyone. One study suggests the average sleep need is 8 hours 40 minutes, plus or minus 10 minutes or so, but 13.5% of the population may need 9 hours or more sleep a night. (The RISE app will tell you your exact sleep need down to the minute for better energy during the day.)

If you’re a young adult reading this, know your sleep need may also change as you age. Per the National Sleep Foundation, preschoolers may need 10-13 hours per night while teenagers may need 8 to 10. Older adults (aged 65 years old and above) need for the most part the same amount as they did when they were younger, but falling and staying asleep is much harder as we age. 

However, generic guidelines like this are exactly that: guidelines. Guidelines are largely reliant on observational studies and self-reported data, which is often inaccurate. They’re based on how much sleep people are getting, not what they actually need, and don’t take into account everyone’s individual sleep need.

To figure out your own sleep need you can:

  • Wake up without an alarm for a week: Keep track of how long you sleep for when you don’t force yourself awake with an alarm. This method can easily be inaccurate, however, as it’s hard to figure out when exactly you fell asleep and remember all the times you woke up during the night. Plus, if you sleep for a long period of time, it’s hard to tell whether this means you have a longer sleep need or whether you’re catching up on sleep deprivation from all your nights of only getting five hours of shut-eye. 
  • Use the RISE app: To take the guesswork out of it, turn to a sleep calculator like the RISE app. RISE uses your phone use behavior and proprietary sleep-science-based models to work out your sleep need and give you a number to aim for down to the minute. 

RISE users on iOS 1.202 and above can click here to view their sleep need.

Moreover, even if you think you’re sleeping for five hours per night, you’re probably actually asleep for even less. Research points out that we tend to subjectively inflate our sleep duration compared to the actual amount of shut-eye we get. 

To compound the issue, sleep fragmentation is a pretty common phenomenon, as many tend to stay awake up to an hour per night, and we often don’t remember. “Retrograde amnesia” occurs where we forget the minutes just before falling asleep and the sub 10-minute micro-awakenings throughout the night. So we aren’t able to take into account sleep efficiency, the measure of how long we spend actually asleep while in bed, which combines the time it takes you to fall asleep with the time you spend awake during the night. All this is to say: spending five hours in bed almost certainly doesn’t equal five hours of sleep.

You can learn more about how much sleep you need here. 

2. You’re Misinterpreting Cues

RISE app screenshot showing how much sleep debt you have
The RISE app can work out how much sleep debt you have.

Falling asleep as soon as your head hits the pillow makes you think you are a “good” sleeper. And you may chalk up mild sleepiness during the day to not having your morning coffee yet or think it’s perfectly normal. 

However, falling asleep immediately can signal extreme sleep deprivation. Meanwhile, what you feel is mild sleepiness is in fact another warning signal of sleep debt (the amount of sleep you owe your body compared to your sleep need). 

Indeed, William Dement, one of the founders of the field of sleep medicine, was often found quoting his world-famous mantra, “Drowsiness is red alert.” Even if you're only feeling slightly tired during the day, it's actually an indication that your body is already suffering from sleep deprivation. And this sleep deprivation doesn’t just tank your energy levels, everything from your productivity to your emotion and physical health will be impacted. 

The RISE app can work out how much sleep debt you have. Got a better night’s sleep than usual and still feeling tired? We’ve covered why you’re still tired after 8 hours of sleep here.  

RISE users on iOS 1.202 and above can click here to view their sleep debt. 

3. You Think You Can Hack Sleep

With busy jobs, family obligations, and errands to run, wouldn’t it be great if we could get some more time in the day by sleeping less at night? But, sadly, that’s not how sleep works.

The human sleep cycle consists of four stages: there are three stages of non-rapid eye movement (non-REM) sleep (N1, N2, N3) and the fourth stage is REM sleep. Every night, we cycle through these stages roughly 4-6 times, averaging 90 minutes in each stage. But these cycles don’t look exactly the same throughout the night. We spend more time in deep sleep in the first half of the night and more time in REM in the second half of the night. 

When you meet your sleep need, you allow your brain to spend the ideal amount of time in each stage, resulting in better energy, health, and performance. When you only get five hours of sleep, however, you miss out on one of these important sleep stages, depending on if you head to bed late or force yourself up early. As a result, we’re depriving ourselves of the restorative sleep we need to function. 

Furthermore, research indicates that sleep restriction over one night, or multiple nights consecutively, preserves slow-wave sleep (also known as deep sleep or stage N3) while reducing stage N1, stage N2, and REM sleep. Since REM sleep is needed for vital functions like memory consolidation and problem-solving, shortening this sleep stage will likely lead to a cognitive decline in your waking moments. 

But you can’t decide how long you spend in certain sleep stages. And even when you get more sleep to recover from nights with a lack of sleep, your brain self-optimizes, often getting more REM sleep than usual to make up for what it lost out on, at the expense of other sleep stages. All this to say that the only good sleep and energy hack that actually works is meeting your sleep need.  

4. Your Brain and Body Are Tricking You

RISE app screenshot showing your energy peaks and dips
The RISE app can predict your circadian rhythm each day.

As humans, we subjectively adapt within a few nights of short sleep. You may think you’re doing fine, but in reality, your performance is in decline. In as short as a few days, your subpar energy levels start to feel normal, while behind the scenes, your daytime functioning and overall well-being are objectively crumbling.

Another reason why you might not feel particularly tired after a night, or several nights, of short sleep is due to a surge in your cortisol levels (a stress hormone that boosts alertness) the next day. 

On top of that, your circadian rhythm (i.e., your body’s internal clock that dictates your energy peaks and dips throughout the day) is still marching on in the background, as it operates independently of your sleep drive, or your need for sleep. High stress levels coupled with your circadian energy peaks allow you to keep functioning (albeit not at your best) even when you’re massively sleep-deprived. (Do note that these peaks could be so much better if only you’d met your sleep need!)

The RISE app can predict your circadian rhythm and show you when your peaks and dips will be each day. It can also tell you when your body naturally wants to wind down for bed, the best time to go to sleep, and when your body wants to wake up, so you can work towards a healthier, more productive sleep schedule.

RISE users on iOS 1.202 and above can click here to see their upcoming energy peaks and dips on the Energy screen. 

5. You Aren’t Using Those Extra 3 Hours Productively

Contrary to your game plan of sleeping less to do more, sleep deprivation prevents you from productively using those extra hours of wakefulness. Matthew Walker explains it perfectly in his book Why We Sleep, "The recycle rate of a human being is around 16 hours. After 16 hours of being awake, the brain begins to fail." In other words, you think you’re doing yourself a favor with less sleep, but that’s just not true cognitively, emotionally, or physiologically.

Is 5 Hours of Sleep Bad For You?

Five hours of sleep (or four, six, or seven, or, more to the point, any period of time that is less than your biological sleep need) will result in sleep deprivation, which comes with both immediate and long-term side effects.

In the Short Term

Acute sleep deprivation or sleep debt is the amount of sleep you’ve missed out on relative to your sleep need. In the RISE app, we calculate this over your past 14 days. What might come as a surprise is, the immediate effects of sleep debt far outweigh the subtle cues that you aren’t functioning and feeling your best. Its repercussions can be felt:

  • Physically, such as intensified daytime sleepiness
  • Emotionally, such as increased irritability
  • Cognitively, for example, poorer decision-making skills

For example, not sleeping for 24 hours impairs your cognition to the extent of having a blood alcohol level (BAC) of 0.10%, which is higher than every state’s legal limit.

But the effects of sleep debt aren’t just from pulling an all-nighter. These negative effects will mount from slightly missing your sleep need over multiple nights — such as only sleeping for seven hours per night when your sleep need is eight hours. In fact, getting an hour less of sleep over 10 consecutive nights will make your brain as impaired as it would if you had stayed up for a full 24 hours — even though it very well might not feel that way.

Despite the extra hours of wakefulness, there’s a very good chance you’re not achieving more than if you’d used those hours to sleep. 

In the Long Term

As well as having no energy, not meeting your sleep need over many months and years will result in chronic sleep deprivation, and its negative effects are even more insidious, possibly due to being in a constant cortisol influx. Sure, cortisol feels good in the short term. Yet, continually pumping your body full of it is one of the reasons why so many debilitating chronic diseases are associated with chronic sleep deprivation.

A 2022 study found sleeping for five hours or less a night at age 50, 60, and 70 was associated with a higher risk of multimorbidity, or having two or more long-term health conditions. And a 2018 study found sleeping for four hours a night has the same effect on your mental abilities as aging eight years.

Research shows not meeting your sleep need over time can lead to an increased risk of health problems, such as:

Sacrificing a few hours of sleep to get more things done isn’t just futile. It’s also shortchanging your overall health and wellness, and consequently, your quality of life.

Start Meeting Your Sleep Need to Be at Your Best

We know it’s tempting to get fewer hours of sleep because you want to achieve more each day. But to be at your best, you first have to get enough sleep to meet your need.

That’s why we created the RISE app to help people meet their sleep need every night so they can feel better and perform better every day. Here’s how the app can help you:

RISE calculates your personal sleep need using the sleep and activity data in your phone measured over the last 365 nights. It also reveals your running sleep debt on the Sleep tab to show if you’re getting too little sleep. We recommended keeping sleep debt below five hours to feel and perform your best.

But keep in mind, life tends to throw us curveballs, which may disrupt your usual sleep patterns and bump your sleep debt up to more than five hours. If things get off track, you don’t need to stress. Nor do you have to go from a 5-hour sleep habit to your actual sleep need overnight, especially with existing work and societal obligations that may be hard to shift around in your schedule.

Instead, prioritize and celebrate the incremental improvements. Go to bed 15-30 minutes earlier tonight to get more sleep over the course of a couple of weeks. If you find yourself slightly drowsy during the day, nap during your afternoon dip (the time of your dip can be found on the “Energy Schedule” in the app) to better maintain your energy levels. With simple, gradual adjustments to your sleep and wake routine, you will eventually meet your sleep need every single night.

Summary FAQs

Is 5 hours of sleep OK?

5 hours of sleep is not OK. Studies show getting five hours or less sleep puts you at greater risk of having two or more long-term health conditions. Not getting enough sleep can lead to weight gain, type 2 diabetes, heart disease, and a weakened immune system, and in the short term, your mood, productivity, and daytime energy will all take a hit.

Is 5 hours of sleep better than none?

5 hours of sleep is better than none, but to maximize your energy levels, mental health, and performance, you need to be meeting your sleep need — which will most likely be more than five hours.

How little sleep can you survive on?

You may be able to survive in the most literal sense on less sleep than you biologically need, but everything from your health to your mental performance will be seriously impacted. It’s not clear how long you can survive with no sleep at all. There aren’t many studies looking into sleep deprivation beyond 48 hours as they’re deemed unethical.

Is 5 hours of sleep enough once a week?

No, 5 hours of sleep isn’t enough once a week. For optimum energy levels, good health, and maximum performance, you need to meet your individual sleep need each night — which is most likely more than 5 hours.

How to survive on 5 hours of sleep?

If you need to survive on 5 hours of sleep, try to live in sync with your circadian rhythm and get more sleep through naps, if possible, to minimize the effects of the sleep deprivation. Get bright light, drink coffee (not too close to bedtime), exercise, and take a cold shower to boost your energy levels.

I only sleep 4-5 hours a night

If you only sleep for 4-5 hours a night, you may have a sleep disorder like insomnia or sleep apnea. Poor sleep hygiene — like getting late-night bright light, eating large meals before bed, or drinking coffee too late in the day — may also keep you up past bedtime. Maintain good sleep hygiene to get more and better sleep.

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About Rise
Rise is the only app that unlocks the real-world benefits of better sleep.

Instead of just promising a better night, we use 100 years of sleep science to help you pay down sleep debt and take advantage of your circadian rhythm to be your best.

Over the past decade, we've helped professional athletes, startups, and Fortune 500s improve their sleep to measurably win more in the real-world scenarios that matter most.

Rise Science is backed by True Ventures, Freestyle Capital, and High Alpha; investors behind category winners Fitbit, Peloton, and Salesforce Marketing Cloud.
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