Think about it this way: If prolonged sleep were not absolutely essential to your survival and health, sleep would be the biggest mistake evolution has ever made. an animal spending 1/3 of its life unaware of it's surroundings is an incredibly steep evolutionary price to pay. It should be obvious that if we evolved to do that, there would be gigantic benefits to it, considering htat there is not a single known animal with a nervous system that does not sleep (including insects!). If caffine was actually helpful at reducing your need to sleep, an animal would have evolved by now to endogenously produce caffine.
There is a substantial body of sleep literature now showing huge benefits to physical / mental performance, willpower and creativity from sleep. Don't fight it, use it.
One statistic thats particularily compelling to me: Every year during daylight savings when everyone loses an hour of sleep, the rate of heart attacks rises by 25%. On the day of the year where everyone gains an hour of sleep, heart attacks fall by 21%. Thats the effect of gaining / losing a single hour of sleep.
I picked up the habit again just because it's nice to have that warm, tasty beverage to start the day, and decaf just isn't the same. As long as you keep it to one in the morning and maybe one in the early afternoon, it's fine.
> However, we are not in a natural situation, but a profoundly unnatural one. For children in particular, Matricciani et al 2012 demonstrated a drastic fall in their sleep time over the past century, indicating that they are not in any state of nature.
But you are of course right that sleep is essential for performing optimally.
My thinking is that evolutionary arguments should be somewhat trustworthy concerning humans and sleep because there's no evidence that we've found anything to replace sleep in humans. I think that the idea that caffeine could be an effective replacement for sleep silly because caffeine is something animals would have evolved to secrete if it was beneficial for them to do so.
That said, if we found an intervention that significantly increases people's sleep quality and efficiency or to mimic all the benefits of sleep in waking humans then yes evolutionary arguments about humans and sleep go out the window.
Sleep science suggests that if we must be sleep deprived we should do everything we can to limit it. If you're the parent of a newborn, that likely means napping every chance you get to at least limit the damage you've done to your sleep through constant interurptions. Caffine will reduce the effectiveness of those naps.
Had friends that did this. We never did, but after 3 kids and ~7 years of pretty consistently broken nights from one or other of the kids, I sometimes wish we did.
My only other advice would be to take turns with the other parent to give each other a break. Whether it be week on/week off or night on/night off, and may involve someone sleeping in another room to get away from the disruption.
I optimistically think a good night's sleep is just around the corner. Cultivating feelings of love and patience is well worth the effort.
Having kids that don't sleep well is a special kind of torture, I can see how it would break some people.
Try to learn some how to play some complex part (piano, guitar, drums, whatever) sometime in the evening. You struggle obviously, you spend a good hour trying to get it. Give up, go to sleep: the next day you're way better at playing this part than you were after one hour of non-stop training
Every year during daylight savings
Plants spend 100% of their time in that state. We only need to wake up to feed and fuck (and perform tasks to enable those things).
In some senses, wakefulness may be thought of as neurotoxic and much of whats going on during sleep is centred around repairing the damage caused by being awake.
For instance, the glial cells between your brain neurons shrink allowing your body to flush the beta amyloid from your brain with cerebral fluid. Beta-amyloid is a neurotoxic protein which causes Alzheimer's an is a byproduct of waking brain function. This explains the link between Alzheimer's and sleep deprivation.
Sleep is also the phase where short-term memories are evaluated and either discarded or integrated into long-term memory. It's also essential for your immune health and cancer prevention. Your body produces dozens of cancer cells daily, but they're killed by your immune system. After only a single night's sleep deprivation, your amount of cancer-killing immune cells plummets. This is why shift work is now classified as carcinogenic in several countries.
Edit: Just on the topic of sleep being for energy savings, did you know that during hibernation (a state actually used for energy savings), bears will actually leave their hibernating state in order to sleep? I think that fact really showcases how important sleep is and should put to rest any notion that sleep is for energy savings.
Allergies get worse.
Anxiety shows up more easily (in response to milder stressful stimuli), has stronger effects, and takes longer to subside.
In general cognitive function is impaired: alertness, memory, attention span, ...
The skin and hair get greasier.
In general, I've learned to moderate my caffeine intake and restrict myself to mornings only. The more you consume, the more you need of it to work at all, and the more likely you are to have side effects like feeling tired, having poor sleep rythm, headaches, etc.
When used in moderation it's a great tool for getting yourself productive after a lazy weekend on a monday morning. However, if you feel tired all the time, stop drinking coffee and get a few nights of good sleep in.
I've heard this over and over, but as far as I can tell, caffeine = caffeine = caffeine. I'm not a chemist, but I can't find any mention of any different forms -- it's C8H10N4O2. 
Is there any scientific evidence that alertness is related to anything but the quantity of caffeine, regardless of whether it's delivered as black tea, mate tea, coffee, pills, etc.? Assuming that the caffeine makes it into the bloodstream at the same rate?
But if a Coke is ~3mg caffeine 100ml and coffee is ~40mg per 100ml, drinking 13.3 "units" of cokes will not be equivalent to 1 "unit" of coffee.
1. Timing of the intake will affect the efficacy (x mg of caffeine over 2 hours vs. 20 minutes is very different to the body)
2. Controlling for time-dependent intake (the spherical human consumed both quantities instantly), concentration of the substance affects the rate / efficiency of absorption by the body (I cannot predict for which way it will go, this stuff is complex) so the net absorbed caffeine will be different between the two substances
3. Delivery mechanisms are different: Coke is very sugary, black coffee is not and is a colloidal suspension. The local chemical environment for the caffeine within these two substances will be different. Sugar is known to affect osmosis, meanwhile who knows wtf the gunk in coffee is doing at the chemical level.
So to sum up "caffeine = caffeine = caffeine" is probably a useful rule of thumb and will get pretty far, but at the physiological/biochemical level, that is as useful as armchair pseudoscience is.
To use a possibly relatable issue: most people find consuming shots of vodka more efficacious than consuming the equivalent amount of beer by alcohol. 3 shots will probably get you more wasted than necking 3 beers
I know it was just an example, but after looking into this earlier this year, coke and pepsi have a much higher caffeine content at 10mg/100ml and 13mg/100ml (for coke and pepsi respectively)
But it won't, after drinking 3 beers after each other your BAC will go to the same level, just takes a little more time to get there.
Subjectively, you start feeling drunk much more quickly because the change is faster with Vodka, but your capabilities are as much impaired.
Though my intuition tells me that chugging three beers would get me more drunk than drinking three shots. Sigh. The things I do for science.
The obvious question is what you're drinking - with the rise of craft beer scene, 3 beers could easily be substantially more alcohol than 3 shots. But assuming you match alcohol volume and consumption speed, absorption rates can still vary substantially.
From what I can find, it looks like beer actually would get you (and everyone) more drunk: diluting alcohol substantially speeds up absorption, and carbonating dilute alcohol probably does also.
The espresso I drink never contains sugar or milk.
The coca cola zero I drink doesn't contain sugar either.
I cannot stand the highs and lows of sugar. I notice it especially at birthday parties. I mean, its already boring... and them comes up of the sugar rush followed by a low where I start yawning and feeling sleepy. I so not wanna be there anymore at that point.
The general trick though, is dosages. You want to keep it stable when it matters, and at the end of the day wind down. Which means you do not want to drink caffeine drinks anymore in the evening.
For the rest, I can highly recommend mindfulness to help increase focus (but before I started it, I found it super annoying when someone suggested it and then I tried it myself and it didn't work out; so I am following a course on it, for people with autism). Meds can help out as well.
Their site says it contains 27g sugar/8.4 fl oz. Pretty sure sugar is a stimulant.
For me, the same whisky has very noticeable differences in the effect and after-effect depending on how it's served / mixed.
That's a big if. Others have listed a few factors to consider, another example is Guaraná powder which contains a lot of fiber, thereby slowing the caffeine intake.
I think yerba mate makes me more stimulated but less "wired" than coffee. I have mainly been making tea with the actual mate leafs and not so much the sugary club mate.
theobromine takes longer for your body to remove than caffeine. (also the main stimulant in chocolate, and the one that is bad for dogs, because they can't metabolize it).
mate has more theobromine than coffee, so it's effects should last longer. just measuring caffeine is not a good way to find out the total stimulant effect.
Do yourself a favour and take the next step. Stop ingesting daily and reserve coffee for sleep emergencies and medicinal purposes. Even a single daily cup of coffee is enough to build a tolerance to it.
Besides affecting alertness, caffeine is also a very effective way of increasing the potency of many drugs. For me, Advil by itself has little effect, but in combination with caffeine it works great.
I found a study of caffeine producing grapefruit-like inhibitory effects on some people https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5625156/
I recently heard about goody's when we ran a marketing campaign for them.
The nascar themed marketing was probably why i hadn't heard of it but I did end up trying it and the mixture of the two works great
For reference I got this mate mug https://smile.amazon.com/gp/product/B01GJXBR94/ref=oh_aui_se... and these straws ("bombillas") https://smile.amazon.com/gp/product/B01M1N9U23/ref=oh_aui_se... (because the one that came with the mug let a bit too much tea particulate through) and am very happy with that combo.
Here's a good video on the "ritual" of making it: https://www.youtube.com/watch?v=-BW1-pE4XaE
I've tried at least 10 different brands since I had my first Club Mate 15 years ago, and I hated every single one of them. A few friends hate Club Mate and only like a single other brand.
I only drink coffee when I need extra alertness.
Meditation can also increase your hability to be alert without resorting to drinks.
OP is on about Club Mate. A soda drink with mate.
Its not very good for the teeth, like other soda drinks (the acid, Co2, and sugar). Furthermore, tea is bad for keeping your teeth white. But other than the latter, normal yerba mate doesn't suffer from the other downsides soda has. Normal yerba mate doesn't contain acid, Co2, and sugar.
4 parts club-mate
2 parts lemonade
1-2 parts white rum
Glass filled with ice
Startup founders on the other hand always have more work than time, and they need to be careful not to burn themselves out by overdoing it on the stimulants and the work.
Edit, OK I see it is actually yerba mate based soft drink.
As someone who used to drink a LOT of cola-cola during their teens, caffeine really fucked me up good. I only noticed I was dependant (addicted)
on caffeine after a friend pointed out I only felt good again on certain days after coming back from a client where there was no cola available.
I took a little bottle with me to the client and felt "normal" that day. Didn't even know it had caffeine. Had fairly bad anxiety and panic attacks at the time.
I then quit caffeine cold turkey. Couldn't even sit upright when I woke up after 2 days of not taking any.
I've now tried it on and off and noticed my anxiety / panic attacks happened out of nowhere, somewhat related to consuming caffeine. I think it happens a couple hours,
sometimes a day after consumptions. Really took a couple years link it to caffeine. I've been to doctors, hospitals, psychiatrists, physical therapists, blah blah blah. It was just fucking caffeine.
If you read this and think consuming coffee or cola all day is fine see what happens when you stop taking it for just a couple days. Yeah I get it, you just use it to "boost" your energy during the day right, you're definitely not addicted, right? Yeah, headaches in the weekend are normal - everyone has them..
(As an aside, it's an interesting problem how long is 'long enough' when proving you can go without something.)
I still choose to drink coffee just because I love the taste and the ritual so much. I limit myself to 1 cup in the morning daily.
(try to get 1000mg a day)
In my personal experience, weaning yourself off caffeine over the course of a couple of weeks is drastically easier than attempting to quit cold turkey. My preferred method of reducing or eliminating caffeine dependence is to reduce intake by 25% every 3-4 days. Once you're down below 50mg per day, you can switch to tea or quit without any physical side effects.
I think the level I'm at now -- still ~2-4 cups -- is perfect. I find I'm productive and still sleep well.
Note: 2-4 cups still sounds like a lot, but I mean 1 cup = 250ml not 1 mug.
If you run any type of startup/company, you are already in a very stressful position, no need to make it worse.
Eventually, I realized the soda was doing bad things to my system and got off it. I didn't drink coffee or tea, so that mean almost zero caffeine as well.
Lately, I started drinking chai twice per day at work. I've found that I'm a lot more productive and active, both at work and at home, though I do tend to get really sluggish a couple hours before bed.
I don't know drinking so much caffeine permanently altered my metabolism/body chemistry so that I need caffeine, or if it was an inevitable consequence of aging. It's weird to find that I now "need" caffeine just like everyone around me, when I definitely didn't just 10 years ago.
2-4 still seems like a lot - this is coming from someone who doesn't drink at all anymore, but before 1, maybe 2. Now I only drink if I know I need the alertness. More effective for me considering the caffeine tolerance is gone and even a little has full effect.
Why did you hate it?
I can't really explain why I hated it with complete accuracy -- I think I just felt overall less energetic. And I felt this way when I was definitely over the effects of caffeine withdrawal.
I now substitute with a tea in the morning if necessary.
I don't know a lot about this topic, so feel free to correct me.
There is also a genetic variation in receptors/enzyme configurations, think of it like the global options/settings. One person may react quite differently due to slight changes in the shape of their receptor due to a different genetic allele.
It definitely is a consideration if you're drinking a lot of coffee.
Now that I'm a professional engineer and no longer in indentured servitude I stick to an 8 hour work day, get 7-8 hours of sleep a night, and have the rest of the day to spend with the family. There's no reason in this day and age to work yourself to the point of chemical dependence if your life isn't on the line.
Pour the grounds into the napkin to keep it all together, then pop it in like a plug of dip. The taste was brutal, but it got the job done.
Do what's best for you, personally, and not what some internet stranger thinks is the correct way to function.
I've also done sleep studies and endless 'preventative' medicines for migraines but nothing has worked so far.
Caffeine is definitely not a cure-all, and I don't want to argue that it's good to use, but it's also not fair to blanket statement and say that everyone should avoid it at all costs :)
Caffeine disrupts the quality of sleep even if you are not aware and feel like you are sleeping fine. I'm not saying this is the cause of any issues you have, but just want that to be considered.
Attention and focus have strong correlations with sleep quality. I say this as a fellow "ADD-er", and only point this out because, being in the health field, I see so many people who completely neglect proper sleep hygiene and then wonder why they feel like crap all the time. This makes me suspect that most of the population has no clue how important proper sleep is to quality of life.
This. Things happen (emergencies, sicknesses, etc.), but if you are sleep deprived due to work more than a couple of times a year, change it! For people saying they do not have this option, go make it (choices, like rights are never given; they are taken). It might take a while, but it is worth it. If you have in demand skills but are not appreciated at your work, move. If you do not have the skills to move, acquire them, etc.
Yeah if possible I will always choose a full, restful night's sleep. But if I can't for some reason, it's nice to know there are ways to mitigate this temporarily.
If only more people had this choice.
I may have missed it, but I don't see where they account for the diet of their test subjects.
(I'm not judging, I've been known to skip the odd meal here and there myself.)
I do notice particular things CAN give me GERD more often, particularly if I eat something high in sugar on an empty stomach, especially if I've had a lot of coffee that day. I need to have "real food" in my stomach before I can do candy, donuts, etc.
This is the primary reason I started skipping breakfast. I know, I know...donuts aren't an ideal breakfast, but they're hard to resist when someone brings them in the office and you don't remind yourself that you're going to suffer from heartburn all morning if you indulge.
Does anyone know a better resource?
Anyway, subjectively speaking I find that all the online estimates are too low, at least for the type of tea that I drink and in the concentration I prefer.
Also, subjectively it seems that tea has a more complex psychoactive effect that either pure caffeine or coffee. If I drink enough caffeine, I can avoid the symptoms associated with caffeine withdrawal, but I don't get nowhere near as strong as an effect as I get from from tea, even if I drink a lot of caffeine. It appears tea has other stuff in it apart from caffeine.
Now when I travel I take my own tea, cup, and immersion heater with me.
As I said, I really like tea, but only good tea that properly prepared is good. What passes for tea these days, sometimes even in tea shops (!) is usually poison. An easy litmus test is this: do they use a thermometer when making green or white ea? If not, that means they use boiling water which will destroy the tea. I think most people never had good tea in their life. I strongly dislike coffee, but I somehow suspect I only drank bad coffee that was not prepared correctly, and that I would enjoy good coffee.
I never found it affected me.
It's probably different for different people, but I can highly recommend trying to "get some good stuff" to see whether it can do the same for you. I wouldn't want to miss it.
Another curious thing I have noted: While living in Japan I was binging on houjicha (which has significantly less caffeine due to the roasting process) on late evenings so I would still be able to sleep. After several strong pots (we are talking litres of 1:1 water/leaf ration) I would often get into a different mind-space that is pretty close to what you are talking about. I tried to research if other catechins (like l-theanine) also disappear in the roasting process or if they could be the explanation, but weren't able to find anything to back this up.
It mostly seems to negate the negative effects of caffeine (apart from problems falling asleep) and gives a mood-boost and counteracting stress. It only goes so far of course, over-consumption of tea will still yield anxiety and dependence, but the threshold for this is a lot higher.
As George Orwell put it, "the best manner of making it is the subject of violent disputes" http://www.booksatoz.com/witsend/tea/orwell.htm
I am older, and drink both tea and coffee depending on mood, need for caffeine, etc.
There are some online guides that give ratios of caffeine in typical tea versus typical coffee. Of course, figuring out what "typical" is is the issue! What I've seen shows that black tea has quite a bit less caffeine per serving (bag, infuser full, etc): 1/10 to 1/5 of coffee caffeine. However, there seems to be a big difference in coffee strength! As an anecdote, I personally find little difference in caffeine between weak coffee (Dunkin Donuts regular is a good example) and a strong black tea (Tazo Awake, for example). On the other hand, Starbucks drip coffee is like getting a meth injection! Immediate symptoms: increased heartbeat, "speedy" feeling, fidgeting, etc.
Also, I hear you on water temps. At home I use an aeropress and 195 degree(F) water for coffee pressing. To me, there really is a taste difference (less bitterness, mainly) if I leave the water just below boiling, but some people don't see any difference and like their water hotter.
Experimentation seems to be the only way to get to your caffeine happy place!
Theanine and Caffeine Content of Infusions Prepared from Commercial Tea Samples
Caffeine in Tea Revisited
Caffeine Content in 39 Tea Samples
90% of the tea I drink is loose-leaf, and I'm sure there are definite differences between loose and tea bags, because tea bags very often have very fine almost tea "dust" instead of actual leaves, and the increased surface area makes it extract faster.
The psychoactive effects you are talking about are likely a result of L-Theanine, if I had to guess
A good approximation of that is taking 2/3 boiling water and 1/3 tap water (if you have 10°C tap water that works out to exactly 70°C). Don't forget stirring before adding it to tea, to make sure it's well mixed.
For optimal results obviously read the packaging of your tea and use a thermometer.
Link to evidence? I don't remember seeing anywhere in the literature that caffeine stops being effective when used daily and long-term, nor does it match my own experience.
48 hours without sleep isnt realistic for most cases, and I dont think these results have anything to say about daily caffeine.
Also, I think the best advice is to learn your body. I cycle caffeine every few months. 2 cups all at once before I need 5 hours of productivity.
In my own case I've been tracking caffeine use and some helpful strategies are:
- 30mg after a brief afternoon nap
- 50mg to 60mg after a long afternoon nap that resulted in grogginess
- 100mg after a terrible night's sleep and before a long meeting
- Extreme care if I have an exhaustion headache due to lack of sleep and overproduction; caffeine often triggers migraine here
Table 2 suggests that to match the performance of studies 3 and 4 (done by other researchers), which each gave 600 mg of caffeine, they were able to cut the dosage down to 500 mg and 400 mg respectively. But it's not clear to me that they're recommending that as the overall optimum, and that's the only place I'm finding "600" in the paper.
Sadly, my sleeping problems don't have clear external factors like that so I usually don't know if I'm going to have three days of bad sleep ahead of time like that.
In those with a high level of the enzyme, caffeine is metabolized quickly, so they can drink coffee in the afternoon and still fall asleep. They are less likely to get anxiety from caffeine, and do not suffer from a higher risk of heart attacks with coffee consumption.
In contrast, a small amount of CYPA12 prevents caffeine from being metabolized and prolongs its effects.
Perhaps he has a high level of CYP1A2? I am wondering if there's a cheap but effective method of measuring it.
Most likely he just has a tolerance to caffeine from drinking it. It sounds like he drinks it all day.
You can't make an assumption like that, you have no evidence and there's many possibilities.
I learned that caffeine makes adrenaline last longer by blocking it receptors in college. https://science.howstuffworks.com/caffeine4.htm
My trick is no adrenaline no caffeine effect. I would do 10 push ups or run around my car a few times and then drink down the caffeine and that changed everything.
As someone who, prior to being medicated, used to get a lot of panic attacks, I can safely say that the effects of too much adrenaline being dumped all at once is pretty inhibiting.
My only note is that none of those things seem hard for someone that works out.
What is the intensity for these things? I can do about 60 pushups before they start to get hard and run for 30 minutes.
Do you need it to be intense? Or just do some exercise?
Thanks for the tip
I couldn’t find the algorithm though...
I think the best advice is to learn your own body. Sure there are similarities between everyone, but good caffeine habits are more important than the dosage.
I couldn't find it after reading the abstract and quickly scanning the first page.
I don't have problems sleeping, headaches, or with fatigue. I look forward to the jitters; it actually cheers me up to know that soon I'll be so intense.
I wonder if perhaps there’s something related though.
Will that habit do long term damage to your physical, emotional, mental, and professional health? Absolutely.
It's so common and acceptable to be physically addicted to a stimulant (caffeine) that people tend to forget they are indeed physically addicted to a stimulant. Not saying I haven't been there in the past... but wouldn't you view your habit differently if 'I'm not alive before my second cup of coffee, hehe!' was replaced with 'I need a bump of cocaine to start my day'?
I'm not implying that cocaine and caffeine are equally harmful drugs, just pointing out that physical dependence on a stimulant is NOT healthy, even if it's the norm.
As far as I could find out, they are illegal (Amphetamine), prescription-only (Modafinil) and/or very bad for your health (Methamphetamine). Amphetamine and Methamphetamine are also rather addictive and apparently quitting once you formed a habit is no fun. Ephedrine might be an alternative, but in Germany, it's prescription-only, and I did not care enough to research the possible health issues it might cause. I vaguely remember there were a few substances that sounded promising, but they were fairly new, and I could not find out anything about their possible health effects, addictive-ness, etc...
So it's either caffeine or plenty of sleep, at least for me.
So I found that psudoephedrine (cold medicine) is pretty darn close to amphetamines.
Find the 12 hour, 120mg capsules. I think you get 20 pills for like 6 dollars. Basically I'd take 2 saturday morning. Wait a half hour and drink caffeine as needed through the day.
Wow. I'm talking from 5AM until 2AM I am able to work. Not just stuff I enjoy, but even the worst of work.
Gl, dont get screwed by CVS's placebo and crappy brand name psudoephedrine. Be responsible.
I dont get it more than 1 time a month, but I have noticed that stores dont use the same database. You can go from CVS to walmart to the local pharmacy if you needed to.
But if you need more than 10 days a month of psudoephedrine, I wish I never recommended it to you.
But on top of that, B-vitamin complex pills benefit from a lot of side-effects of high intake, including e.g. Niacin flushes and tingling effects, which I thin probably boost the perceived effect well beyond any actual effect.
(I could only find this abstract about US use.)
It's still one of the most popular (if not the most popular) illegal drugs in Japan. source:
However while Modafinil will keep you awake, it doesn't mitigate the downsides of being sleep deprived. At 4am you'll still be irritable, burnt out and not make good decisions. Regular sleep is really the only medicine.
The others have no trouble sleeping even with large doses, but experienced some bad headaches, or personality changes ("I just want to work all day now" -- this may not be bad depending on context).
I quit the trial when I developed large purple circles on my skin. Turns out skin problems, including some medically serious ones, are a relatively common side effect.
Proceed with caution!
Effect attenuates with regular daily use for me, despite most research to the contrary, which leads me to believe it's caused just by plain old lack of sleep during consumption days.
Care to elaborate on the skin issues? Were they planar circles (I know, oxymoron)? And what's "large"? I could maybe correlate some skin issues of mine (up to 1cm, but majority smaller than .5 tumor-like skin bumps, mostly colorless, but some red with darker aureola) to this.
The second time I took it was for an athletic competition to give me focus. It worked well, but I don't think it lasted the whole day.
Ephedrine was an excellent stimulant, but a few people died because they didn't understand what it would do. You wouldn't feel thirsty, and it was sold as a workout supplement, so people would take it and then exercise outside in the summer and suffer severe dehydration. After that it was made illegal in the US, which is too bad because for me it was much more effective than caffeine and sold over the counter.
Bronkaid works great as an appetite suppressant, a little energy boost without much of the caffeine jitters, and as its prescribed effect of opening up the lungs.
Anyone knows what PDF renderer Wiley is using? The performance is fantastic.
Is this PDF.js?
Edit: Found it https://www.readcube.com/
Edit 2: Apparently ReadCube uses PDF.js
This does not necessarily predict real-world effects.
Not legal in the US... :(
There are four different scenarios presented, and each has its own optimal strategy.
In general, their optimal model uses less caffeine overall, and seems to use it in proportion to expected sleep restriction as opposed to using it widely. They cite research on the difficult in recovering from large caffeine loads as their motivation for reducing overall caffeine intake.
The study is a meta study that doesn't actually test individuals but uses data from other studies that do test individuals to assess average group performance under sleep deprivation (either total or chronic restriction) using an algorithm that tries to use the other studies as inputs and predict their results to draw out patterns by finding dosing strategies that optimize performance.
The advice seems to be: reduce total caffeine amount because otherwise recovery to normal is worse, take more caffeine on days with less sleep, and less on days with more sleep, delay the dose to closer to sleep period ( otherwise your performance tanks as your approach sleep period, i.e., you only stay high for so long ), and if you can don't dose on the first and last days of your sleep restriction period, just go "natural".
Some are more vital than others. We have a pretty clear need for lots of air, and a fair amount of water.
But it isn't as reasonable to think that our evolution intended or makes accomodations for caffeine intake.
Ingest at your own risk, whatever the dose. My wallet and my brain tell me to just go without it in my life.
But, in sufficient dosages, caffeine can cause heart attacks, paranoia, spasms and so on. It is a neurotoxic substance.
Of course, you need to massively overdose for these things to happen. Water can be deadly if you overdose it as well. But perhaps we are missing minor damage that's occurring even with proper dosages