And there are at least 3 different metabolic rates for caffeine, rapid, standard, and slow. As a holder of the slow gene, none of these calculators work for me since for me caffeine has a ~9 hour half life. Caffeine after about 11 am is a bad plan.
I'm 57 now, I started noticing poor sleep related to late night coffee in my mid 30s. I do got fairly hard earlier in the day though, I've usually had 4 double espressos (somewhere between 17-21g of beans) by mid morning, and usually another one or two before my current self imposed 2:30pm cut off.
Then something changed, and now I am sensitive to it like a normal person. It does wake me up after a sip or two I can feel it, and I can easily have 'too much' if I have 2-3 cups in too short of a timespan, so I've had to learn to slow down.
Having said all of this, my personal 'last call' is 6pm, with the idea that I will be able to sleep at 12-1am. But if I drink coffee after 6pm I might be delaying that bedtime a little.
It will be interesting to learn more about the effects of how much, and how long. Should I be tapering off hours before 'last call'? What is the best 'last call' time in the day and should it be earlier? I'll have to track some of this and figure this out!
Update: did a quick search, Reddit says it could be overtraining or dehydration.
https://www.lesswrong.com/posts/E4cKD9iTWHaE7f3AJ/melatonin-...
I'm envious of your 100 grams of beans a day consumption - if I have more than about 10g / one single espresso I'm a wreck for the entire day! The area-under-curve for slow metabolizers is 9 times larger - 3x the duration, 3x the concentration.
One thing I am fairly sure about, the amount of caffeine makes a difference to my sleep quality. If I have a single cup of coffee in the morning, no more, then my sleep quality seems not to be impacted. If I have several cups of coffee, only in the morning, I feel great for the morning, very stimulated, but my sleep is impacted. I wake up with a buzzing several times a night and have never been able to understand what is causing the buzzing.
Most likely it's the leftover caffeine still in your system that's beyond your personal threshold for quality sleep.
I have the same issue. If I drink two double espressos very early in the morning and then no more after that for the rest of the day, I have no problem falling asleep at night but I keep waking up several times during the night with a buzz, while my gf can drink 3 coffees per day and an espresso after dinner and still sleep.
The only way to get rid of this is reduce my caffeine intake to absolute zero, which is hard when you get the smell and taste of fresh single origin beans. I guess some people are just that much more sensitive to it than others, genetics be dammed. I wish there was a cheap way to measure the caffeine content in the coffees I make so I can precisely determine my personal threshold.
Yes, that's me. I can fall asleep, but I wake up a lot.
If you ask anyone who works in genetics, though, they'll advise you never to do it. It can be bad news, but there's virtually no good news there.
And I take exception to your “no good news”.
I discovered a gene polymorphism that led to the discovery the reason for my immune deficiency and mood disorder.
I found it gave me agency as well since I know that these genes are all risk genes and not fully determinant genes.
I would regard that as one of the exceptions in the "virtually no" caveat.