Test your sleep knowledge on these 6 "facts." Can you tell true from false?
Science is famously sketchy on why, exactly, we have to sleep. Luckily, though, research over the past 50 years has revealed a ton of insights into the hows and whens and whats of sleep. But when it comes to us non-scientists, how much of what we know about sleep is true, and how much is outdated/urban myth/made up by mom so we'd go to bed on time? Here are some facts you may have heard - and whether they're actually fiction.
Here are some facts you may have heard about sleep - and whether they're actually fiction.
1. When you sleep, your brain turns off.
This is FALSE. Your brain goes through stages of sleep - four of them, in fact - and in some, your brain is even more active than when you're awake! Scientists are still working on what, precisely, is going on in there - but they think it's related to memory consolidation, long-term memory formation, processing newly learned tasks and information, and other important functions.
2. REM is the last, deepest, and most important element of the sleep cycle.
This is FALSE. First of all, REM is only sort of the last stage. There are 3 other sleep stages, and a "cycle" actually goes like this: 1-2-3-2-1-REM. The "deepest" stage of the sleep cycle is actually the third - in fact, this stage is often called "deep sleep" or "slow-wave" sleep (referring to the lower brain activity in this stage). You can think of it like swimming : you jump in (fall asleep), dive down into deep sleep, then come back up, stopping just before the surface and freestyling there for a while before coming all the way up. That last part - where you're close to the surface, but just below - that's REM sleep, and that's where a lot of the interesting sleep stuff happens in your brain.
REM is known as "active" sleep because a lot is going on in your brain (most dreams take place here), but it's also called "paradoxical sleep" because while your brain is flashing all over the place, your muscle activity is so low that your limbs are practically paralyzed. Crazy, right? But despite all this activity, REM sleep isn't better sleep - just one part of the cycle.
3. You go through 2 or 3 sleep "cycles" per night.
This is FALSE. Most people go through 4 or 5 sleep cycles on a typical night, each lasting between 60-120 minutes. Toward the beginning of the night, the stages are shorter, and involve more of Stage 3, the "deep" sleep. Toward the end of the night, cycles are longer, and involve more REM sleep.
4. If your sleep cycles are interrupted, you'll feel groggy in the morning.
This is TRUE. Each stage of the sleep cycle appears to have a distinct function that's important to the health of the body and mind. If sleep is interrupted or if stages are missing for some reason (eg. sleep disorders, chronic pain, certain medications, or because your alarm clock went off right in the middle of deep sleep), those functions aren't completed, and you can feel tired and groggy even after an apparently "full" night's sleep.
5. We spend most of the night in deep sleep.
This is FALSE. Sleep stages 1 and 2 - together called "light sleep" - make up around 50% of most people's night.
6. A good night's sleep is unbroken - if you wake up, you're not sleeping well.
This is FALSE. There's a period of a few seconds to a few minutes in between sleep cycles when you're awake or close to it - you likely don't remember them. Even if you come completely awake and fluff the pillow and maybe use the bathroom, it's still completely normal. In fact, through most of history (when many went to bed and woke up with the sun), a whole night of unbroken sleep wasn't the norm at all. Often people slept for a few hours, woke up to complete some task - feeding the baby, checking the animals, starting the breakfast bread - and then slept for a few more hours until sunrise. So don't worry!