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 body is very good at building tolerance to caffeine because sleep is important for survival so it will adjust itself to become more tolerant to higher doses as you ingest more and more coffee. Caffeine blocks adenosine from signalling that you’re tired so you feel awake but your body responds by building more adenosine receptors to counter this chemical from stimulating you.
Adenosine never leaves your body, it just builds up more and more while the receptor is blocked. Eventually your body will be so overloaded with this that it will collapse asleep the moment your half-life on caffeine hits or your tolerance builds up high enough.
Caffeine, and other stimulants, cannot actually give your body more energy. They can block feelings of tiredness or unlock energy reserves your body already has, but once these reserves run out they are out, and not everything that replenishes with sleep can be restored with a tablet, after a while even with ample stimulant you will start to go insane without sleep, and after an extended period of insanity you will expire. I believe the record for staying awake without death or disease is held by a radio DJ who was quite out of his mind towards the end of his attempt. I studied psychology at university and sold mattresses for a living; everything science reveals to us about sleep still does not give us the entire picture of why, precisely, we need to sleep, but we very much do, the only thing we need more frequently than sleep is water; you will perish more quickly if deprived of sleep than of food.
When you sleep deep you get fluids from the spine to issue out into your brain and rinse it of waste particles. Never sleeping leads to a buildup of bad things and then after four days of no sleep your normal functioning is inhibited to such a degree that you can’t do anything in a satisfactory way; not work, not socialize, not perform hobbies.
There is also a non-zero chance that staying awake for more than 72 hours can kill you through a stroke, heart attack or aneurysm, but this depends on what you are doing for those 72 hours. If you’re lying in bed you likely won’t fall into shock, but if you are playing high-stress multiplayer games, fleeing from assailants, or something else incredibly taxing, you might punch your own ticket.
Caffeine makes me sleepy af after half an hour, so if I took continuously caffeine I would sleep forever
Cause you’d die. You’d eventually collapse and fall asleep or worse. You really need sleep and caffeine only makes it feel like you don’t, but eventually you’d really really need to take a nap or a good night’s rest. It’s one of those things in the body that are non negotiable.
Ever been around someone with mania who’s been up for 3 days? That’s why.
Imagine that fatigue is the force that gradually, harder and harder, presses on the sleep lever.
Caffeine temporarily blocks the switch (adenosine receptors) and creates an opposite force (cortisol, dopamine) making sleep impossible. But the force that acts on the switch continues to increase as if nothing is happening.
Body becomes resistant to caffeine levels if you continuously take it your body operates normally as if you had never had any.
Caffeine fits into the pockets where adenosine is supposed to go. When the adenosine fills up the pockets, it makes you sleepy. When the caffeine is in the pockets, the adenosine can’t fit. Your body is all like “I made adenosine, but still no sleepy, I guess I’ll make extra tomorrow because if no sleepy, then dead.” Body then makes too much adenosine and the pockets get full too early. Don’t fill your adenosine pockets with caffeine. Get some sleeytime.
The way that I’ve always understood it is that caffeine takes up receptors in your brain that are intended for your natural sleep chemical.
But the sleep chemical builds up in your brain like a pressure and eventually the pressure will get so high that any more caffeine added to the mix simply won’t be able to reach those receptors before the sleep chemical can and your brain will fall asleep
I’m sure other people can add greater detail, or more information but I thought I’d keep it simple (plus I’m not an expert so that’s about the extent of my understanding anyway :P)
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