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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The purpose of sleep in humans is to do maintenance on the body. Running your body on caffeine acts on receptors in your body but won’t let your body maintain itself. This leads to memory problems and cardiac problems, leading to heightened risk of stroke or Alzheimer’s.
Focusing on the sleep side.
The US military has done multiple studies on the effects of sleep deprivation on service members, because it’s not uncommon for personnel in combat or other crisis situations to be unable to consistently get enough sleep. These include studies where they kept people awake with amphetamines or other drugs for multiple days.
In a fairly short period of time (less than a week) humans begin hallucinating and suffer other serious side effects from not having time to rest their brains. There is no drug or technique that can safely stave off sleep for long, so caffeine is simply a short term boost for daytime tiredness.
Also, caffeine isn’t 100% safe. There are cases of people having heart rhythm problems or other issues from energy drinks or the caffeine pills sold in some gas stations, or from the fake Molly sometimes sold in bars that’s really caffeine.
Impprtant info, when you drink a coffee even 12 hours later you still have 25% of the coffeeine your system. Especially when you get old this can become a huge fucking problem with sleep.
Once i started experimenting with caffeein free coffee it opened my eyes. Now i only use caffeein in the morning, its a gamechanger. If you think you can only function coffee you are screwing yourself.
If you’re interested in learning more about what a lack of sleep does, there is a disease called Fatal Familial Insomnia which is a genetic prion disease that stops those afflicted from sleeping. Pretty much 100% fatal. [https://www.bbc.com/future/article/20160118-the-tragic-fate-of-the-people-who-stop-sleeping](https://www.bbc.com/future/article/20160118-the-tragic-fate-of-the-people-who-stop-sleeping)
Caffeine can help you stay awake and alert for a while, but it can’t fully replace the need for sleep because they work differently in your body.
When you’re awake for a long time, your body builds up a chemical called adenosine, which makes you feel tired. Caffeine blocks adenosine receptors in your brain, which is why it helps you stay awake by temporarily reducing that tired feeling.
However, your body keeps producing adenosine, and eventually, caffeine can’t block all of it. So, even if you take more caffeine, your body’s natural sleep drive becomes stronger, and you’ll feel extremely tired.
Brain needs to turn off and on again, caffeine just tricks it into not thinking it needs to for a while.
Caffeine makes you more alert, active and energetic by binding to adenosine receptors which slow down nerve activiity and prepare you to sleep. Your body is used to the amount of caffeine you normally take so to feel the same effect you did, you have to up the dosage, but your body will adjust to the higher dosage, so you’ll have to up the dosage again. It’s a vicious cycle. Caffeine can’t replace sleep because caffeine isn’t a reset switch like sleep is.
There’s various mechanisms that regulate our bodies sleep cycle. Also not sleeping for too long is simply deadly by the way. We have evolved to need sleep for various ‚upkeep‘ processes to happen; like memory formation etc.
Caffeine only affects one specific mechanism of sleep regulation. During the day a chemical called adenosine accumulates in the brain. Once levels are too high it signals your brain that sleep is warranted.
Caffeine blocks the receptors that sense this adenosine. However no medication 100% completely blocks those receptors. Most medications won‘t even do so if you grossly overdose them.
So caffeine pretty much only reduces your brains capability to sense adenosine. Eventually more adenosine will accumulate, and your brain will still get the same strength of signal from the adenosine, it would have gotten at night if you hadn’t taken caffeine.
Additionally your body notices when receptors are messed with, which means if you take caffeine daily, there‘ll be more adenosine receptors in your brain, so it gets more sensitive to adenosine, and taking your regular caffeine dose will just make things normal, rather than suppressing the signal like it would when you take caffeine for the first time.
Anyway, since adenosine keeps accumulating, and caffeine only reduces your brains sensitivity to adenosine, eventually enough adenosine will build up to make you feel tired.
However there’s more mechanisms at play that control the sleep cycle, so other chemicals get produced when you in low light, melatonin that is, and there‘s even more signaling chemicals involved.
So even if you totally broke the adenosine part of the system; you would eventually fall asleep.
Things have to get reeeeeeally really messed up for you zo actually become incapable of sleep.
There‘s a genetic disorder that causes progressively worsening insomnia and you do eventually die.
But caffeine doesn‘t get anywhere close to stopping you from being able to sleep.
Additionally in conditions like ADHD caffeine can even make it easier to fall asleep, because like other stimulant drugs it reduces the racing thoughts in people with adhd, which makes you calmer which allows you to fall asleep more easily.
As for other way of blocking sleep even if you take strong stimulants like amphetamine or methamphetamine, they will indeed allow you to stay awake for quite a bit longer, but they will not at all reduce the negative effects of lacking sleep, so you will be less good and doing tasks, miss steps etc.
And after several days even with stimulants you will pass out, and if you dose them even higher you‘ll experience a psychotic break as well, from lack of sleep plus the stimulants side effects.
There‘s other drugs like modadinil that has virtually no stimulant like effects, unlike amphetamines or caffeine, that allows you to stay awake longer without being as drastically impaired. And is actually fda/EMA approved for exactly like your use case: shift worker sleep cycle disorders.
However even modafinil doesn‘t prevent you from eventually falling asleep. It just slows down many of the negative effects of being out of sleep accumulating, as well as allows you to willingly stay awake.
If you were to take modafinil for your shifts, you‘d still be able to fall asleep when you come home, go to bed and turn of the light/close the blinds.
It would however unlike the caffeine, prevent you from ‚accidentally‘ falling asleep because you are too tired.
And this is pretty much the best way humankind has found to delay onset/need of sleep.
Either way for caffeine specifically, it simply reduces your brains sensitivity to the ‚we should get sleep‘ chemical that continuously accumulated every hour. So it can simply delay the time at which you will feel tired, but it does not actually block you from being able to feel tired.
Also shifting sleep cycles are EXTREMELY toxic to your mind and body. Life expectancy for nurses working changing shifts is massively reduced compared to nurses who stay on a complete nightshirt cycle even on their days off, but they also still have reduced life expectancy.
So don‘t Switch your sleep rhythm around frequently. Keep to a schedule.
Since all the sleep regulations mechanisms in the body aren’t tightly linked, they will be out of sync if you aren’t awake during the same daylight hours every day.
That’s because some mechanism are basically just running on a somewhat close to 24hr clock, while other systems are set to outside events, like ambient light, and others to physical activity.
If these systems don‘t align, risk of heart disease for example goes up.
Your brain is like the ice cream machine at McDonalds. It needs down time for maintenance. Without the maintenance, it stops working. But because it’s like the ice cream machine at McDonalds, some times it stops working even when it does get the maintenance.
Why can’t we take the fuel gauge off the car and never need gas?
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