How Long Can You Go Without Sleep? Probably Not As Long As You Think

All of us have at least one major thing in common: Every one of us sleeps. Some of us seem to function fine on five hours of rest. Others can’t “human” properly without their full eight hours. For many, naps are a daily requirement. And some of us haven’t napped on purpose in years.

Though there are many reasons some people can’t seem to get enough sleep — no matter how hard they try — science has proven time and again that sleep deprivation hurts. But exactly how much does it affect your brain?

Why do humans sleep, anyway? Is it really that harmful to go a day or two without a snooze? How long could you, theoretically, live without it? Here’s what researchers know so far.

Why do we sleep?

Man asleep on his side

Man asleep on his side | YakobchukOlena/Getty Images

Have you ever thought about how strange it is that humans — and many other living species — lay down and close their eyes at a certain point in the day and remain unconscious for hours at a time? In terms of survival, it doesn’t seem practical. In the middle of a forest, a predator could sneak up behind you during a snooze and you’d be completely vulnerable.

Even stranger is that despite having had many years to attempt to answer this question, researchers still don’t know exactly why we need to sleep. We know that going without sleep for too long can kill us — so it must be important.¬† We’re also pretty sure the reasons we sleep have to do with a process in our brains we don’t yet understand.

Do our brains “recharge” when we sleep? Do they use that time to clear out toxins? Store memories? All of the above? It could be years or more before this becomes clearer. If it ever does.

Sleep deprivation hurts — no matter how severe

One thing’s for sure: Not getting enough sleep — or going completely without — isn’t good. After about 24 hours without sleep, you might feel tired, fatigued, and have trouble concentrating. Symptoms only go downhill from there.

After 3 days (72 hours) without sleep, it becomes nearly impossible for a person to stay awake on their own. You’re much less likely to be able to complete tasks that require communicating with others or making decisions or calculations. You’d probably get a little cranky, too.

By day 4, people generally start hallucinating. This is also when you’d start to experience “micro-episodes” of sleep. Microsleep occurs when your body is trying to fight off sleep. For anywhere from one to 10 seconds, your body actually does attempt to sleep, even if you don’t realize it. This becomes extremely dangerous when you’re doing something like driving.

It’s not very common for someone to last much longer than this without sleep — they’d eventually lose control of their ability to stay awake. This is why it’s extremely rare to die from sleep deprivation specifically. Technically, you could stay awake longer than four or five days straight. But it wouldn’t be pretty.

How long can you go without sleep?

Sleep deprivation

Sleep deprivation | iStock.com/monkeybusinessimages

According to the¬†International Journal of Occupational Medicine and Environmental Health, the longest a human has ever been recorded going without sleep was about 11 days. But it only takes half that time to enter a state researchers call “sleep psychosis.”

At this point — around the sixth night of severe sleep deprivation — a person can no longer distinguish between what’s real and what isn’t. Thankfully, it’s possible to recover from this stage of sleeplessness. You’d just have to sleep for awhile first.

You’d likely never make it to that point if you were trying to stay awake on your own. But even if you did manage to go 10 days or more without sleep, you wouldn’t really be experiencing it.

There’s a reason you feel like a zombie the morning after staying up too late. Even though we don’t know why our brains need us to sleep, they can’t function properly without it.

Get some sleep. Even if you don’t think you need it, you won’t be fine going too long without.