Many of us neglect sleep to make room for other things, whether it's staying up to cram for an 8 a.m. chemistry test, partying through the night, or watching one more episode on Netflix. In fact, a simple Google search for "How long can you go without sleep?" generates close to a billion search results.
But, we're here to shed light on why you shouldn't sacrifice sleep if you want better wakefulness. After all, there must be a reason why roughly a third of our lifetime is reserved for sleep.
Below, we explain why you can't get more out of your day by sleeping less, and the unwanted side effects of sleeplessness that start racking up almost immediately. Most importantly, we’ll tell you how the RISE app can help you meet your sleep need for better energy during the day.
How Long Can You Go Without Sleep?
For a science fair project in 1965, Randy Gardner set the world record by going 264 hours — roughly 11 days — without sleep. This resulted in significant declines in his concentration, motivation, perception, and higher-level mental processes. A 2017 NPR interview with Gardner revealed signs of nausea on the third morning of the experiment. Most worryingly, he complained of memory loss which felt like “an early Alzheimer's thing brought on by lack of sleep.” In other words, the human body isn’t made to withstand sleep deprivation to any degree.
Dr. Mark Rosekind — a former Director of Stanford University’s Sleep Center and current sleep science advisor to Rise Science — explains that sleep is as vital as air, food, and water. A lack in any of these basic essentials is akin to a death sentence. The same goes for sleep.
And it doesn’t take 11 days without sleep to start experiencing negative effects. In Matthew Walker's book, Why We Sleep, he points out, "The recycle rate of a human being is around 16 hours. After 16 hours of being awake, the brain begins to fail." So that means after being awake from 6 a.m. to 10 p.m., for example, you’re already starting to experience cognitive impairment.
So, let’s look at what happens if you go 1-3 days without sleep.
24 Hours of Sleep Deprivation
An all-nighter will immediately affect how lousy you feel and how poorly you function the next day. For instance, after a night without sleep, you will most likely become easily irritable at the slightest blunder. Not only that, but a full 24 hours without sleep also results in the same cognitive impairment as having a blood alcohol level (BAC) of 0.10%, which is higher than every state’s legal limit.
Research also shows 24 hours of total sleep deprivation impairs “molecular clearance from the human brain,” specifically leading to amyloid-beta (a metabolic byproduct) accumulation in the cortex. Incidentally, the buildup of amyloid-beta and the eventual formation of amyloid plaques is a distinctive hallmark of Alzheimer’s disease. As such, sleep deprivation (particularly in the long term) can heighten your risk of neurodegenerative disorders like Alzheimer’s disease.
36 Hours of Sleep Deprivation
When you’ve been awake for a day and a half, the stakes are even higher:
- One 2013 study involving young soldiers highlighted that 36 hours of wakefulness “significantly increased error rate” in participants.
- Another 1997 study confirms you’d likely have a slower reaction time, reduced attention span, and a higher likelihood of microsleeps (dozing off for a short while without conscious knowledge).
- The Journal of Sleep also reports sleep-deprived participants exhibit reduced speech eloquence and expressionless voices.
- A more recent study shares a fall in the body’s ability to retain heat coupled with higher-than-normal blood pressure after staying awake for 36 hours.
48 Hours of Sleep Deprivation
If you have gone two whole days without any sleep, brace yourself for the backlash:
- Your immune system drastically weakens after 48 hours of wakefulness. In fact, the Journal of Sleep Research warns of a drop in natural killer (NK) cell count, which are immune cells with anti-tumor and anti-viral properties.
- You’d likely face a decline in stimulus detection (an aspect of visual processing), which inevitably leads to cognitive impairment. Expect severe downgrades in your daily performance and productivity.
- You’re even more susceptible to the lure of microsleeps, which compromises your personal safety and doesn’t bode well for everyday tasks like driving. In fact, the AAA Foundation for Traffic Safety shared that up to one-fifth of all fatal crashes involve a sleep-deprived driver. Of course, you don’t have to go 48 hours without sleep to encounter this risk. A little sleep deprivation, for example, sleeping an hour less than you needed the night before, is enough to impair your driving skills.
- You may even start hallucinating, according to a 2018 systematic review.
72 Hours of Sleep Deprivation
If you’ve made it this far without any sleep at all, it's a major cause for concern. According to a study involving 12 astronauts who stayed up for 72 hours, you’re most likely struggling with a poorer mood, diminished information processing, and a faster heart rate. On top of that, animal studies indicate circadian misalignment, greater oxidative stress, heightened anxiety, and neuroinflammation following 72 hours of wakefulness.
Gradual Sleep Loss Is as Bad as All-Nighters
One thing to note before we go any further is that sleep deprivation isn't just the product of missing full nights of sleep and staying awake for extended periods of time. You can do just as much damage shaving off an hour of sleep every night for a week. For example, after 10 consecutive nights of getting seven hours of sleep — one hour less than the average eight-hour sleep need — your brain becomes as impaired as it would if you hadn’t slept for a full 24 hours.
Many of us can probably relate to this second scenario of small amounts of sleep loss every night. Perhaps you’ve stayed up an hour or two past your bedtime to catch up on work or binge watch your favorite show on Netflix. What you dismiss as insignificant sleep debt is actually critical sleep loss that’s on the same level as pulling an all-nighter.
Why that can be hard to comprehend (indeed, pulling an all-nighter vs. missing out on an hour or so of sleep across a week definitely feels different), we tend to adapt subjectively to sleep deprivation very quickly, so you may not feel immensely tired. That said, know that your cognitive, emotional, and physiological functions have already taken a significant hit. In fact, a 2017 study found that nine days of recovery sleep actually improved the moods of participants suffering from unrecognized sleep loss.
So, How Much Sleep Do You Need?
There’s a popular myth that everyone needs eight hours of sleep to feel good during the day. Unfortunately, there’s no one-size-fits-all solution when it comes to how much sleep you should be getting.
We all have a genetically determined sleep need that varies from person to person and changes over the course of our lifespan. For instance, you may need a sleep duration of 9.5 hours to function at your best while your gym buddy only needs 7.5 hours.
So, to answer the question of how long you can go without sleep, the general recommendation is the difference between one sleep-wake cycle (about 24 hours) and your individual sleep need. For example, if you need nine hours of sleep, then you should stay awake for 15 hours at most.
The Two Levels of Sleep Deprivation: Acute vs. Chronic
Even if you aren’t staying awake for days at a time, not meeting your sleep need will still lead to sleep deprivation, which is classified into short term (acute) and long term (chronic).
Acute Sleep Deprivation
Acute sleep deprivation (also known as acute sleep debt) is the amount of sleep you’ve missed relative to your biological sleep need over the past 14 days. You could rack up acute sleep debt by pulling an all-nighter or by, for example, only sleeping six hours every night in the past week when your sleep need is 9 hours per night.
Chronic Sleep Deprivation
Chronic sleep deprivation (or prolonged sleep deprivation) is much more than just losing a good night’s sleep (or two). Instead, with this type of sleep debt, you’re regularly not meeting your sleep need, much less paying back any of the deficit.
The American Academy of Sleep defines chronic sleep deprivation as restricted sleep for three months or longer. If you’ve been consistently undersleeping for most of your life, say, a nightly sleep duration of six hours on an 8-hour sleep need, you’re likely plagued with chronic sleep deficiency, and inevitably acute sleep debt too.
The Negative Effects of Acute and Chronic Sleep Deprivation
Sleep deprivation, both in the short and long term, makes you feel bone-weary and muddle-headed before your day has even started. You’re probably excessively sleepy and yawn with embarrassing frequency.
Of course, it’s possible the other side of the coin exists. You may not feel tired after a night of short sleep as you adapt quickly to sleep loss in a subjective manner. Research indicates the suprachiasmatic nucleus in your brain (i.e., your circadian clock) secretes more cortisol (a stress hormone) than usual the next day, particularly from the afternoon to evening. This tricks you into feeling more alert than you actually are to help you get through the day on minimal sleep.
And don’t forget, your circadian rhythm is still at play behind the scenes to promote wakefulness (especially during your energy peaks). Unfortunately, the higher stress levels take a toll on your mental health and slows down the recovery process of your body’s cortisol response.
Regardless of how you feel and subjectively assess how you’re functioning, sleep loss will still manifest as low-level brain damage, inciting daytime impairment. Below, we show you exactly how nasty sleep loss can be to your waking life.
What Happens With Acute Sleep Debt?
So, what are the effects of acute sleep debt? According to the Journal of Nature and Science of Sleep, short-term sleep loss comes with:
- Immediate changes to your metabolism, in which less leptin (a hormone that regulates fat storage) and more ghrelin (the hunger hormone) increase your appetite
- More intense morning sleep inertia, i.e., you feel groggier upon rousing
- More severe daytime sleepiness
- Poorer mental health — think greater stress, anxiety, and depression
- Physical and physiological effects, such as a higher frequency of headaches and abdominal discomfort
- Negative emotions, including irritability and impatience
- Impaired work productivity and school performance
- Reduced cognition, in terms of attention, memory formation, decision-making, and judgment
- Heightened risk-taking behavior, such as illicit drug use and drunk driving
What Happens With Chronic Sleep Deprivation?
The physiological, emotional, and psychological repercussions of chronic sleep debt are so deleterious, it’s now labeled as a public health epidemic. After all, research indicates “50 to 70 million Americans chronically suffer from a disorder of sleep and wakefulness.”
Where acute sleep debt incurs immediate, short-term downgrades in your waking moments, chronic sleep deprivation adds long-term mental and physical health complications to the towering pile.
The Journal of Nature and Science of Sleep details the injurious effects of prolonged sleep deficit as follows:
- Increased risk of heart diseases, such as hypertension and high blood pressure
- Heightened susceptibility to metabolic disorders, like obesity and Type 2 diabetes
- Increased body mass index (BMI), which is a likely indication of weight gain
- Higher risk of cancers, such as colorectal cancer and breast cancer
- Poorer mental health as indicated by the close association of suicide with sleep disturbances
On a more chilling note, chronic sleep deprivation is also the direct cause of death in rare genetic sleep disorders like fatal familial insomnia (FFI), in which you’re unable to fall asleep as the disease progresses.
It’s also worth pointing out that sleep is closely intertwined with your immune system. Prolonged sleep deficiency can aggravate the symptoms of existing health conditions, particularly gastrointestinal issues like irritable bowel syndrome (IBS) and acid reflux.
Get the Sleep You Need Every Single Night With RISE
As interesting as it is to probe the boundaries of sleeplessness, the near-term effects are feeling and functioning sub-optimally, and the ultimate endpoint is death. After all, getting enough sleep is as vital as the oxygen you’re breathing in. If you truly want to optimize your waking moments, you should focus on meeting your sleep need, rather than entertain the energy-sapping thought of “How long can you go without sleep?”
The RISE app will identify your sleep need and track your running sleep debt over the past 14 days. This will help you take steps to lower your sleep debt so you can feel and perform your best.
Get the sleep you need to be your best:
- How much sleep do I need? It's more than you think
- Only 5 hours of sleep? It's worse for you thank you think
- Is 6 hours of sleep enough? 5 reasons why it's not
- Is 7 hours of sleep enough?
- Is 8 hours enough sleep? First, find out your sleep need
- Why am I still tired after 8 hours of sleep? 3 likely culprits
- Is 9 hours of sleep too much?
- Why am I always tired and have no energy?
- How much deep sleep do you need? You don't need to know
- How much REM sleep do you need? You don't need to know
- How much sleep debt do I have?
- Learn more about sleep deprivation stages
- Can you catch up on sleep and reverse the damage?
- How long does it take to recover from sleep deprivation?
- Use this sleep calculator to find out how many hours of sleep you need
