Until recently, scientists had trouble answering the question: why do we sleep?
Now we know that sleep restores the immune system, body, and cleanses the brain.
But there's still a lot we get wrong and don't understand about sleep. The longstanding lack of knowledge has created a lot of sleep myths.
For something so fundamental to our lives, there's a lot that we don't get right about sleep.
Until recently, we didn't even have good answers to the question of "why" we sleep, as UC Berkeley neuroscience and psychology professor Matthew Walker explains in his recent book, "Why We Sleep: Unlocking the Power of Sleep and Dreams."
We're better at answering that question now. We know that sleep restores the immune system, balances hormone levels, lowers blood pressure, cleanses toxins from the brain, and more.
"[W]e no longer have to ask what sleep is good for," wrote Walker. "Instead, we are now forced to wonder whether there are any biological functions that do not benefit by a good night's sleep. So far, the results of thousands of studies insist that no, there aren't."
But while we know far more about sleep now than we used to, there are a huge number of myths about sleep that persist. Many of these stem from not understanding the full importance of sleep; other myths have been created by people trying to sell products to improve nightly rest.
These are some of the most prominent myths — and the facts.
Myth: You can become a morning person.
Spend enough time online and you'll certainly encounter some version of the "you can accomplish so much if you start waking up a 4:30 a.m. every day" blog post.
But the truth is more complex.
There are a number of factors that influence your chronotype — that is, whether you're a morning person, a night owl, or whether you fall somewhere in between. Your body clock changes throughout life and is influenced by factors like sunlight and genetics.
Researchers say that while most people can regulate their body clock to some degree (if you want to feel awake earlier, try getting morning sunlight), there's a limit to how much it can be changed. And for some people, becoming a morning person (or switching to become a night owl) is basically impossible.
Myth: You can get by on less than seven hours a night.
If you need a cup of coffee in the morning to feel awake, you didn't get enough sleep.
Scientists like Walker say that if you want to figure out how much sleep you actually need, you should spend about a week letting yourself fall asleep when you are tired and then waking up naturally, without an alarm.
As it turns out, the vast majority of people need between seven and nine hours of sleep a night. There are a few people out there who for biological reasons either need more sleep or can get by with less, but statistically, you're probably not one of them.
People tend to think they can get by with less sleep because after a few days or weeks of 5 or 6 hours, that just starts to feel like "normal." But even though people assume they've adjusted, tests show that they are performing in an impaired state.