Let’s get straight to the point: four hours of sleep isn’t enough for the vast majority of us.
Even if you feel fine on four hours, your energy levels, productivity, and mental and physical health are probably impaired.
Below, we’ll cover what happens when you get four hours of sleep, how much sleep you need instead, and how you can use the RISE app to get more sleep if you find yourself only managing a measly four hours a night.
Four hours of sleep isn’t enough for most adults; most of us need much more than four hours of sleep to maintain cognitive function, emotional well-being, and overall physical health. Amongst our RISE users, the median sleep need is eight hours.
The amount of sleep you need is known as your sleep need. This number is unique to you and determined by genetics.
We looked at the sleep needs of 1.95 million RISE users aged 24 and up and found it ranged from five hours to 11 hours 30 minutes. You can see how few people need five hours — let alone four hours of sleep. We found 48% need eight hours or more sleep a night.
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Other sleep need research shows there are a few lucky people who can get by on four hours of sleep.
They may have what’s known as short sleep syndrome, which is caused by a gene mutation that allows them to sleep for about four to six hours without their well-being or performance taking a hit.
These natural short sleepers are incredibly rare, and even if you have one of the mutations, you’re still not guaranteed to be able to get by on four hours of sleep.
You can learn how much sleep you need here.
Heads-up: You can’t really time your sleep to your sleep cycles or otherwise hack your way into making four hours of sleep work if you need more.
Learn more about why it isn’t possible to sleep eight hours in four hours here.
And if you’re trying biphasic sleep (splitting your sleep into two chunks), be aware that this can lead to insufficient sleep and sleep experts agree that most of your nightly sleep should happen in one continuous chunk for better health and well-being.
There are only two times when four hours of sleep is enough:
Dr. Jamie Zeitzer, Co-Director of the Center for Sleep and Circadian Sciences at Stanford University and one of our sleep advisors, sums it up:
“For the vast majority of people, four hours of sleep isn’t enough. It’s not fatal in the short term, but you will definitely be impairing your daytime performance and health.”
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There are many negative health effects of sleeping for four hours (or any amount that’s less than what you need). You may be able to survive on four hours of sleep, but you probably won’t be even close to thriving.
In the short term, sleeping for four hours can lead to:
In the long term, sleeping for four hours can lead to:
Heads-up: Sleeping for four hours disproportionately affects how much time you spend in each sleep stage across the night. We spend more time in deep sleep at the start of the night and more time in REM in the second half. Research shows people getting four hours of sleep spend less time in light sleep and REM, but the same amount in deep sleep compared to an eight-hour night.
REM sleep is needed for creativity, emotional regulation, and memory consolidation.
When you get more sleep, you might experience REM rebound, when your body gets more REM to make up for what it missed out on. This could then affect your deep sleep. It’s not clear what happens if you chronically get four hours of sleep or the long-term impacts of messing with your sleep stages.
Four hours of sleep isn’t enough once a week. Your energy, health, and performance will be hugely impaired. Even if you get enough sleep on other nights, one night of four hours can still leave you feeling tired, irritable, and unfocused the next day (and beyond if you don’t catch up).
Four hours of sleep isn’t enough for a student. Research shows getting four or six hours of sleep a night for two weeks has the same cognitive impairments as pulling two all-nighters. Too little sleep impacts your energy and health, too. Sleep need is fixed from young adulthood, but younger people often need more sleep, meaning it’s even more unlikely four hours will be enough for a student.
There’s a slim chance you only need four hours of sleep. Even if you feel fine, you’re probably not doing as well as you think.
Your body produces more cortisol and adrenaline to keep you going on little sleep and your brain’s reward system fires up, so you feel more positive.
You can also subjectively adapt to some feelings of sleep deprivation. Research shows we might not notice the increasing objectively measurable declines in cognitive performance we get from sleep loss.
Plus, you might think yourself into feeling fine. A 2021 study found how people feel about their sleep impacted fatigue more than sleep duration. And a 2014 study found people performed better when they were told they’d had good-quality sleep.
There’s also your circadian rhythm, or body clock, to think about. This causes your energy to naturally fluctuate across the day. When you experience peaks in energy, you may feel like four hours of sleep is enough for you. But really, these peaks could be much higher if you got more sleep. RISE predicts the timing of your circadian rhythm each day, so you can see when these peaks and dips in energy will be.
Additionally, you might attribute symptoms of sleep deprivation to stress or poor diet, and your caffeine habit might be masking some of the sleepiness.
Learn more about why you feel energized on less sleep here.
Expert tip: Check RISE to see how much sleep debt you have. This is the amount of sleep you owe your body. We recommend keeping this below five hours to feel and function your best.
RISE users on iOS 1.202 and above can view their sleep debt here.
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Here’s what the National Sleep Foundation says are the recommended amounts of sleep by age group:
Not a four hour recommendation in sight!
But a word of warning: these guidelines are a good starting point, but they’re just guidelines. They’re based on how much sleep people get, not what they need, and on self-reported data, which can be inaccurate.
For example, older adults may not need less sleep than adults, they just get less sleep.
As one paper puts it, “there is no “magic number” for the ideal duration of sleep.”
Sleep affects everything important in life: energy, focus, health, mood. The list goes on. Don’t rely on generic guidelines or try to get by on a measly four hours. Instead, find out exactly how much sleep you need.
You can do this by waking up without an alarm for a week or two and keeping track of your sleep times. You can get an idea of how much sleep you need when your sleep times regularize. This method is tricky to get right, however, as it’s hard to figure out when you fell asleep and, for most of us, it’s tough to find a week or two when we can wake up without an alarm.
We’ve covered more on how to know if you’re getting enough sleep here.
RISE users on iOS 1.202 and above can view their sleep need here.
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You may only be able to sleep for four hours because:
Get more sleep by improving your sleep hygiene.
Here’s what to do:
Use RISE to make sleep hygiene even more effective. The app can send you personalized reminders letting you know the best time to do 20+ healthy sleep habits based on your body clock.
RISE users say these habits help them sleep and be more productive. This means you won’t have to cut your sleep to four hours to get everything done.
“I never imagined that what you do throughout the day has such a profound impact on your sleep quality AND the energy dip in the afternoon. I now sleep better than ever and feel so much more productive throughout the day. Thank you RISE!” Read the review.
RISE users on iOS 1.202 and above can set up their 20+ in-app habit notifications here.
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You can feel less tired after four hours of sleep by getting out in sunlight, taking a cold shower, and exercising to feel more awake. Check RISE for when you’ll feel most alert that day, so you can schedule your most important tasks for this time.
Then, catch up on lost sleep by getting to bed early, sleeping in, or taking naps.
Just to make it clear, we’re not advocating getting four hours of sleep! But we know that sometimes you’ll have an early flight, tight work deadline, or teething toddler.
You can learn how to function on no sleep here (only do this when you have to).
Expert tip: Do a HIIT session. A 2022 study found high-intensity interval training helps stop the reduction in myofibrillar muscle synthesis (key for maintaining muscle mass) that sleeping for four hours can cause. And a 2021 study found HIIT can counteract the reduced glucose tolerance and mitochondrial respiratory function (energy conversion in your cells) that comes with sleeping for four hours. And HIIT releases feel-good endorphins, too.
It’s not clear if this works long term, though. And be careful to avoid injury when working out on no sleep.
If you need the extra hours in the day (who doesn’t?), it’s tempting to try and get by on fewer hours of sleep — especially if you feel rested after just four hours.
But four hours of sleep isn’t enough for most adults. We all need a different amount of sleep, but it’ll most likely be much more than four hours.
Use RISE to find out how much sleep you need. And if you can’t get more than four hours when you try, follow RISE’s 20+ sleep hygiene habit recommendations to get a good night’s sleep.
RISE helps 80% of users get better sleep within five days!
RISE makes it easy to improve your sleep and daily energy to reach your potential
RISE makes it easy to improve your sleep and daily energy to reach your potential
