I work overnight shifts (11pm-7am) and take caffeine pills to stay awake. When I get home, even if I take more caffeine I’m sometimes still too tired and fall asleep. Why does it eventually stop working? Is there some sort of chemical limit? Why can’t caffeine replace sleep for longer periods of time (like days on end)?
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Your brain needs to rest and recover for a set period of time. We do this by falling asleep. Getting tired is just your body telling you it’s time to get some rest and go to sleep.
Caffeine is a stimulant, which means that it tricks you into thinking you are not tired. Basically “covering up” the tired feeling. What it does not do is actually refresh your brain and body in the same way sleep does.
So after a certain number of hours, when the caffeine stimulation wears off, you will feel tired again – likely more tired than before you consumed caffeine, because you “covered up” a few gradients of feeling tired, but did not stop the process of actually getting tired. Of course, you can just consume caffeine again.
But eventually, one of two things will happen:
* You will be so tired that even caffeine can’t cover it up enough, and you will crash, OR
* If you power through enough, your body will eventually give away in more dangerous ways (such as a heart attack) because you aren’t giving it the rest it has been needing to recover. Reaching this stage is relatively difficult as most of us just crash before getting to this.
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Think of it like a bad charger cable. You can put some tape around it, and it will hold enough to work again. The tape allows the cable to continue functioning, but it does **not** fix the cable. Eventually, the tape will wear away and the cable will deteriorate some more. You can always wrap it in tape again, but eventually, the cable will just rip completely no matter the amount of tape.
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