SU#001. Why do I sleep well even if I drink coffee?

 "God…. wasn’t I supposed to finish that assignment until tomorrow? I might have to take some deep strong coffee right away."
"That’s good for you… Every time I drink coffee to get away from drowsy condition, it doesn’t work at all !!"

You might have seen people who drinks coffee just to take caffeine but doesn't get easily awaken no matter HOW MUCH THEY DRINK. Are you this kind of person? If you couldn’t see any effect of caffeine in your life, you really wanted to know exact reason what makes this situation sense. 'I wish I can get some help of caffeine like everybody else'.So why do I sleep well even if I drink coffee at night?


And do I really sleep well after I drink coffee?



"What makes us sleep? "
When a cup of coffee awakes us, it is pretty sure that coffee did interrupt our sleep. However, when coffee did not bother our sleep, it means coffee has not affected my sleep at all. So, we need to understand how we get into sleep to know when caffeine interfere our sleep.

degree of sleep = sleep pressure – degree of body awakening according to biological clock

When we are awake, the brain continues to use energy. As a result, a substance called adenosine is produced and is combined with adenosine receptors in nerve cells. This combination inhibits the secretion of dopamine. Dopamine is a substance involved in the awakening of the brain. Therefore, sleep is induced when the secretion of dopamine is inhibited.

The longer you stay awake, the more adenosine builds up. Then the combination of adenosine and adenosine receptors increases. The more these bonds, the more inhibited dopamine secretions are and the more sleepy our bodies become. This level of sleepiness is called sleep pressure. In other words, the longer you stay awake, the greater the sleep pressure.



reference : principles and practice of sleep medicine


In the picture above, S is the sleep pressure and C is the degree of awareness according to the biological clock.(Actually, the longer you stay awake, the greater the sleep pressure.) S - C is the extent to which the body wants to sleep. This value is the area colored in the figure. If this colored area exceeds a certain level, you will fall asleep. And the reason why sleep pressure decreases during sleep is because adenosine decreases.

Let's think about it on this basis.
What can we do to stay awake?

It is possible if you reduce the amount of sleep you want. However, the awareness caused by the biological rhythm is not adjustable because it is 24 hours. Therefore, the bonds between adenosine and adenosine receptors should be reduced.


"Caffeine"
Caffeine in coffee or energy drinks has a similar structure to the adenosine described earlier. It can also easily pass through the brain-protecting Blood Brain Barrier (BBB), which can then combine with adenosine receptors and have a direct effect on the brain. As a result, the body's increased caffeine binds to nerve cells, which prevents subsequent adenosine from being combined with nerve cells. As a result, the body is tired, but the brain is not feeling tired. It's what we call a wake-up call.



Caffeine on the left and adenosine on the right.


So is it because caffeine did not properly interfere with adenosine in people who can sleep well even if they drink coffee? What is the difference between people who wake up when they drink coffee and those who don't?


"What's different?"
After all, caffeine is a factor that hinders sleep. Because of caffeine, people don't feel tired. So why can't caffeine affect people who aren't affected? Let's assume that their body caffeine dissolves at a faster rate than normal. In fact, there are enzymes in our bodies that break down caffeine. It is an enzyme called CYP1A2. This enzyme breaks down toxins, especially those related to caffeine decomposition. The liver is also known to be responsible for detoxifying our bodies. Thus, CYP1A2 is an enzyme secreted by the liver and its activity depends on a person's genes. Moreover, since CYP1A2 is an enzyme, it is affected by external factors other than genes. Among them, tobacco is known to increase the activity of the enzyme and foods such as grapefruit and ginseng are known to decrease the activity of the enzyme.

Those who were less affected by caffeine were essentially due to genes involved in caffeine decomposition. Because of the additional effects of eating habits, caffeine was absorbed into the body and quickly disintegrated.



CYP1A2 Aesthetic Diagram of how enzymes are created and operated


So, can we drink coffee before going to bed?"
According to the paper published in the Journal of Clinical Sleep Medicine, those who said they drank coffee but slept well also found that the quality of sleep had decreased. The subjects, who answered that they slept well even if they drank coffee, also responded that they slept well in the survey. However, based on actual figures, he did not sleep as usual. No specific reason was given, but the subjects were not physically able to experience the decreased quality of sleep caused by caffeine.

It is generally known that it takes about seven hours for the body to reduce caffeine. In a paper just cited, he also reported that coffee, which he drank six hours before he fell asleep, lowers the quality of sleep. Therefore, even those who think they are not affected by caffeine should avoid drinking caffeine just before bed for the next day's condition.


"How to maximize the efficiency of caffeine"
To be exact, I'm not saying you should drink coffee before you go to bed. It is about how to increase the efficiency of coffee. We try to apply what we learned earlier to real life. I learned two things from the beginning.


1. Why does caffeine wake you up?
This is because adenosine prevents it from binding to nerve cells.

2. What is the correlation between Tiredness and sleep?
As you sleep, adenosine decreases, and your tiredness decreases too.And all food must get through digestion process and coffee cannot be an exception.


If you drink coffee and sleep while caffeine is absorbed, the adenosine that has already been produced will disappear. But when you wake up, absorbed caffeine will take up the vacancy of adenosine. Therefore, the efficiency of caffeine can be maximized in this way.


"Another way to maximize efficiency"
According to a paper published in the NCBI, there is also a way to inject powdered caffeine directly to speed up the absorption of caffeine. Because it has sufficiently small molecular size, it could be inhaled smoothly into the brain and could be delivered immediately right through the lungs. The exact mechanism has not been identified, but when caffeine is moved to the lungs immediately, it can also be absorbed into the blood and transmitted to the heart. However, the FDA has warned against powdered caffeine. The method of taking refined caffeine tablets is inexpensive, but the effect is equivalent to two to four cups of Americano. There is also the possibility of consuming too much caffeine at once when taken carelessly.

There are conflicting opinions about caffeine ingestion in any form. But I do not want to recommend these two methods I just introduced. The specific process that occurs in our body after caffeine ingestion will be discussed next time. 

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Reference
http://jcsm.aasm.org/ViewAbstract.aspx?pid=29198
https://www.e-jsm.org/upload/0301006.pdf
https://www.everydayhealth.com/news/snorting-caffeine-powder-could-damage-your-heart/
https://www.fda.gov/food/dietary-supplement-products-ingredients/pure-and-highly-concentrated-caffeine