Eli5 why can’t we continuously take caffeine and never sleep?

Question

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)?

In: 595

Answer 1

Actual ELI5: Caffeine doesn’t keep you awake, it just stops you feeling tired. That might help you stay awake longer, or make it harder to settle to sleep if you had a coffee before bed, but eventually you’re going to drop off.