It's good to to understand how your body knows when it's time to wake up or go to sleep. This video explains the two factors that regulate this.
Video by Better Than Yesterday
Key Takeaways
This is Mike. Like a lot of people out there, his sleep schedule has gone a little out of hand. Instead of going to bed at 10pm like he should, he instead plays video games until 3am on daily basis.
However he wants to change that, so he asks others what he should do. He finds out that a common approach to resetting your sleep, is to pull an all-nighter.
Basically you don’t sleep for one day, and you go to bed at the desired time the next day. This means he needs to stay awake for 37 hours, as he usually wakes up at 9am and his desired bed time is 10pm.
This makes sense to Mike, and he plans to do it the next day. He wakes up around 9am, after getting his 6 hours of sleep and goes through his daily routine. He always wakes up tired, but he uses coffee to get him up and running.
When his usual bed time rolls around, which is 3am, he doesn’t go to sleep, but instead pushes forward and stays awake. Mike has loaded himself with coffee and energy drinks, just to make sure he can keep on going and is using video games to distract himself. He feels tired, but he’s also confident in his ability to make it sleepless.
However at 11am, when Mike has been awake for 26 hours, he feels a sudden drop in his energy. He decides to take a quick 30 minute nap and even sets up his alarm just in case. But when he wakes up, it’s already 7pm.
Without even realizing it, he turned off that alarm and instead of napping for 30 minutes, he slept for 8 hours. Now he’s just 3 hours away from his desired bed time. But Mike is fully awake and is not tired at all.
He messed up his sleep schedule even more and now he’s set to be awake during the night. Not good. Mike was set up for failure the moment he decided to pull an all-nighter.
Even if he hadn’t fallen asleep and had made it through those 37 hours, in a few weeks he would most likely be going to bed at 3am again.
All-nighters are like buying a fat loss pill. Sure it could help you suppress your appetite, and you could even lose a few pounds because you’re not as hungry. But if you don’t fix your eating habits, those pills won’t do much. It’s like putting a band-aid on a bigger problem.
Rather than pulling an all nighter, Mike should focus on fixing his sleep habits.
A much better approach for Mike, would be to go to sleep earlier and wake up earlier. If he just moved his sleep schedule 15 minutes backwards, every day, it would be a much better choice. It’s not an immediate fix, but slowly he would get to his desired bedtime.
However a common problem with this strategy is that even if you go to sleep 15 minutes earlier, you will just toss and turn in bed for 15 extra minutes. And waking up in the morning will also feel like a chore.
It’s good to to understand how your body knows when it’s time to wake up or go to sleep.
There are two factors that regulate this:
Two Factors Regulate This
1. Circadian Rhythm
The first factor that determines when you feel sleepy and awake is your circadian rhythm.
Basically this is our internal 24 hour clock and this rhythm controls our bodies.
- There are certain times of day when your body is designed to adjust its temperature and release specific hormones. And the timing of it all, comes down to this internal clock.
- One of the hormones, that is controlled by this body rhythm, is called melatonin. We start to produce it in the evening, and this hormone is the reason we feel sleepy at night.
- However in the early morning melatonin levels drop and we start to produce a different hormone, called cortisol.
- Cortisol is what makes us feel awake and energetic in the morning.
So circadian rhythm controls those two hormones, but what controls our circadian rhythm?
- In 1938, two researchers where curious what would happen if humans lived in complete darkness.
- Would our wakefulness and sleeping pattern become completely erratic or would it still follow a 24 hour schedule?
- The researchers decided to be their own guinea pigs and the took a trip into Mammoth Cave in Kentucky. A cave so deep that no detectable sunlight can penetrate in.
In total they lasted 32 days in complete darkness and two discoveries have been made.
- The first is that humans generate their own circadian rhythm in the absence of external light from the sun.
- Neither of the researchers had random spurts of wake and sleep, but instead expressed a predictable and repeating pattern. About 15 hours of wakefulness, along with consolidated 9 hours of sleep.
- The second finding was that their reliably repeating cycle of wake and sleep, was not precisely 24 hours.
- Instead it was consistently and slightly longer.
In the 80+ years since their experiment, we have now determined that the average duration of adult human’s circadian clock is about 24h and 15min.
This is why it’s much easier to stay awake longer and move your sleep schedule forward. But because we routinely experience the light from the sun, we reset our circadian rhythm daily. The sunlight overruns our imprecise internal clock and winds it back to precisely 24 hours.
Daylight is the most reliable signal that we have in our environment, but it’s not the only signal the brain can use for the internal clock resetting.
As long as they are reliably repeating, the brain can also use other external cues, such as food, temperature fluctuations, exercise and even regularly timed social interaction.
All these events have the ability to reset our internal clock.
It’s the reason why individuals with certain forms of blindness do not entirely lose their circadian rhythm. Despite not receiving light cues due to their blindness, other factors act as their resetting triggers.
- So Mike shouldn’t just move his sleep schedule 15 minutes backwards every day. He should move his entire daily routine. He should be exercising 15 minutes sooner, eating his breakfast, lunch and dinner 15 minutes earlier and most importantly, getting sunlight as soon as he woke up.
Almost everything in your daily routine can act as a checkpoint for you circadian rhythm and by manipulating the timings, you can trick your body into recognizing what time it is.
Sunlight is the primary signal for your internal clock. However, there’s one big problem we face nowadays. Artificial light.
- Our indoor lights are bright enough to disrupt our circadian rhythms, because they mimic the sun.
- This artificial light confuses your body about what time it is, because it can’t tell the difference between a light bulb and sunlight. It doesn’t mimic it to the full extent, but just enough to disrupt your rhythm.
- The problem is not the exposure to artificial light itself, but the timing. The goal is to control the timing in a way that mimics the natural cycle of the day and night.
That means Mike should dim out the lights, use weaker light bulbs or use candles in the evening.
- But it’s even more important to avoid looking at screens at night. The TV, computers and smartphones all emit blue light, which triggers your body into producing more daytime hormones, such as cortisol. And production of melatonin, the sleepiness hormone, gets interrupted as well.
- Two apps that help: twilight and f.lux. They block out most of the blue light, however they are not enough.
- Avoid any kind of screen time, at least 1 hour before bed. Optimally 2 hours.
So the 24 hour circadian rhythm is the first factor determining our wake and sleep pattern.
2. Sleep Pressure
The second factor is sleep pressure.
At this very moment, a chemical called adenosine is building up in your brain and will continue to do so with every waking minute. The longer you’re awake, the more adenosine will accumulate and along with it, so will your desire to sleep.
High concentrations of adenosine turn down the volume of wake-promoting regions in the brain, while simultaneously turning up the dial on sleep-inducing regions.
As a result of that, when adenosine concentrations peak, an irresistible urge for sleep will take hold. That’s assuming you have a stable circadian rhythm and you’re not experiencing jet lag. The peak, for most people, comes after being awake for about 12 to 16 hours.
However, you can artificially mute the sleep pressure of adenosine by using a chemical that makes you feel more alert and awake: caffeine.
- Caffeine works by successfully latching onto adenosine receptors in the brain. By hijacking these receptors, caffeine blocks the sleepiness signal. So it actually tricks you into feeling alert and awake, despite the high levels of adenosine that would otherwise seduce you to sleep.
If you try to stay awake by drinking coffee, you should be prepared for nasty consequence when your body finally removes caffeine from your system. That phenomenon is known as a caffeine crash.
- We now understand why this happens. For the entire time that caffeine is in your system, adenosine, the very sleepiness chemical caffeine blocks, continues to build up regardless.
- Once your liver dismantles that barricade of caffeine, you’re hit with the sleepiness you should have experienced hours ago. But you also get hit by all the extra adenosine that was building in the hours in between, impatiently waiting for caffeine to leave.
- When this happens you are hit by a forceful sleep pressure. Unless you consume even more caffeine to push back against the weight of adenosine you are going to find it very, very difficult to stay awake.
This is what happened to Mike when he attempted his all-nighter. When his body metabolized all the caffeine he had consumed, he was hit by that infamous caffeine crash.
That’s why he fell asleep after being awake for 26 hours. So much sleep pressure had accumulated and he was hit by it all at once.
By now you probably understand that if you consume caffeine before bed, it will negatively impact your ability to fall asleep. You want that sleep pressure to make you feel sleepy in the evening after all.
- What’s problematic though is caffeine’s persistence in your system. It has a half-life of around 5 to 8 hours, which means that half of the caffeine you consume will still remain in your system after 5-8 hours.
- Since you want to feel sleepy in the evening and actually be able to fall asleep, it’s recommended that you don’t consume anything caffeinated 8 hours before bed. (For Mike, that would mean no more coffee after 2pm, since he wants to sleep at 10pm.)
But Mike is also using coffee to function properly. He’s extremely tired during the day and can’t think straight, without it. That’s because he doesn’t give his body a chance to remove all the adenosine from his system.
After approximately 8 hours of quality sleep, the brain degrades and removes the adenosine load. But if you’re like Mike and you routinely get only 6 hours of sleep per night, some adenosine will remain in your system from the previous day and you’ll wake up already tired.
- This means that if you’re not getting both the quality and quantity of sleep on a regular basis, the adenosine doesn’t get fully cleared out and actually keeps building on itself.
- Keep this up long enough, and the result is chronic tiredness and fatigue.
Caffeine masks all the sleep pressure building up, and is used to compete with all the adenosine that’s accumulating.
So if you’re like Mike and need to use coffee to even function, it’s a clear sign you’re not getting enough quality sleep.
If you wake up in the morning and you could easily fall back asleep, then actually getting more sleep should be your top priority. It doesn’t mean you’re lazy, it means your body needs it.
Those two factors determine when you feel tired. The 24 hour internal clock and sleep pressure.
6 Ways to Manipulate your Sleep Schedule
1. Avoid an all-nighter. Sleep depriving yourself by staying up all night, is one of the worst things you can do for your health, even if the end goal is a healthy sleep schedule.
2. Move not just your sleep schedule, but also your entire daily routine. Anything that is consistently repeating in your day, can be used as a cue for your circadian rhythm.
3. Get sunlight first thing in the morning. Light is the primary signal that lets your body know it’s time to wake up. By exposing yourself to sunlight you set your daily tempo.
4. Avoid artificial light at night. Lights that are too bright will confuse your body about what time it is, plus your melatonin and cortisol production will get messed up. Especially try to avoid any kind of screen time in the evening.
5. Don’t consume caffeine at least 8 hours before bed. Caffeine isn’t found just in coffee, it’s also prevalent in different teas, dark chocolate, fat loss pills and even ice cream. In the evening you want the sleep pressure from adenosine to seduce you to sleep.
6. Get enough sleep. If you’re not getting enough quality and quantity of sleep, your body won’t be able to form a normal rhythm. Sleep without an alarm clock. This way your body will actually get the sleep it requires and you will allow your brain to clear out all the adenosine that’s accumulated.