05/17/2026
One more interesting thing about coffee:
There’s a molecule in your brain called adenosine- your body’s built-in “sleep pressure” signal.
All day long, as you burn energy, adenosine gradually builds up. The higher it gets, the sleepier you feel. It’s your brain saying: “It might be time to rest.”
At night, during sleep, adenosine levels naturally decrease, and you wake up refreshed.
Here’s where coffee comes in.
Caffeine works by competing with adenosine at its receptors in the brain.
So the sleep signal is still there… but it’s temporarily less noticeable.
That’s why coffee can make you feel alert even when your body is still accumulating fatigue.
Some people say: “Coffee doesn’t affect me.”
But that often refers to how they feel in the moment - not necessarily to how sensitive their sleep system might be.
In some people, caffeine intake later in the day may also influence sleep quality, even if they don’t clearly notice it the next morning.
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