There are two processes in sleep that determine when we want to be awake and when we want to be asleep.
The first process is called “Process-C,” the circadian process. This has a linear relationship with our drive to be awake. As this increases, so does our ability to stay awake. As you can see in the graph below, our drive to be awake ebbs and flows throughout the day. It rises up until the afternoon, and then starts to slide down. The second process is called “Process-S,” which is sleep pressure. The longer we are awake, the more pressure we have to go back to sleep. From the moment we wake up, a chemical called adenosine that causes this drive to sleep continues to build, making you sleepier and sleepier.
As shown in the graph below, our greatest urge to sleep is when these two processes are farthest apart, around 11PM! The period when these two processes come together is when you naturally wake up.
Of course, when you throw coffee into the equation, this gets all messed up! As we talked about in our article on coffee, this psychoactive drug disrupts the adenosine process and masks the sleep pressure we feel throughout the day, so that when coffee finally wears off, we CRASH.
So stay away from coffee and let these two processes work naturally!