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.
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 by sleeping less. Or maybe you consider short-sleeping a badge of honor. Similarly, a demanding work schedule or a teething newborn may be what’s barring you from meeting your sleep need.

The point is, you think you can survive (if not thrive) on five hours of sleep (or four, six, or seven). Unfortunately, you’re doing yourself a major disservice and in more ways than you might think. Denying yourself the sleep you need — and accumulating sleep debt 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.

Why You Aren’t Actually Doing Fine on Only 5 Hours of Sleep

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 you why you aren't coping as well as you thought:

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

If you think you belong to the minority that does well on little sleep — i.e., five hours of sleep — the odds are close to nonexistent. 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.” 

Matthew Walker further 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. The majority of adults need 7.5-9 hours of sleep per night to function optimally. 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 to prevent neurobehavioral impairment. (The RISE app will tell you your EXACT sleep need for better energy during the day. Read more about how to calculate your sleep need here.)

Your sleep need may also change as you age. To illustrate, preschoolers average 10-13 hours per night while older adults (aged 65 years old and above) usually need about 7-8 hours.

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. Spending five hours in bed almost certainly doesn’t equal five hours of sleep.

2. You’re Misinterpreting Cues

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 tremendous sleep debt. In fact, 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.

3. You Think You Can Hack Sleep

5 hours of sleep: driving man yawning

Thanks to the dubious concept of “sleep hacks,” much of the population is lured into focusing on sleep quality rather than sleep duration. We assume we can cram, with the right tips and tricks, our individual sleep need into only five hours of slumber and get away with it. Sadly, that’s not how sleep works.

Science explains the sleep cycle for humans 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. As a result, many of us aren’t physiologically primed to survive on only 5 hours of sleep a night.

Furthermore, research indicates that sleep restriction over one night, or multiple nights consecutively, preserves slow-wave sleep (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. 

Besides that, recovery sleep following sleep restriction shows the brain self-regulates in the face of sleep deficiency, invalidating “sleep hacks.” In other words, you as a person cannot dictate how much time you will spend in a particular stage of sleep. You can only remove the impediments to naturalistic, healthy sleep.

4. Your Brain and Body Are Tricking You

As humans, we adapt biologically 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 is subjectively 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. 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!)

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.

Why 5 Hours of Sleep Is Worse Than You Think

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 it over the past 14 days. What many people don’t realize 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, you are neither functioning optimally nor are you achieving much at all.

In the Long Term

Not meeting your sleep need over many 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.

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

5 hours of sleep: RiseScience mobile app
The RISE app keeps a running total of your sleep debt over the past 14 days.

You may choose to get fewer hours of sleep because you want to achieve more each day. That’s the ironic thing, though — 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 (the goal is to have five or fewer hours of sleep debt).
  • The RISE app shows your personal “Energy Schedule” on the Energy tab. This displays your energy peaks and dips throughout the day as well as your daily Melatonin Window, i.e., the ideal window of time to go to bed. Aligning your sleep time with your Melatonin Window helps you fall asleep easily and stay asleep throughout the night to feel good during the day.

But keep in mind, life tends to throw us curveballs, which may disrupt your usual sleep schedule 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 (which shows up on your “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.

How much sleep is right for you?

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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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