Well, that's weird. I normally will sleep for five hours, no matter when I get to bed. The cardiologist put me on a new drug this past week that slows down my heart rate. Now, my pulse has always been fast, and since they've had me taking data, it had been averaging about 108. With the new medication, that's down to about 90 (although the outliers are 80 and 120). Now, that's not odd in and of itself (just shows the meds are working), but what's odd is that I'm sleeping well past 5 hours now.
It's almost like some OCD part of my brain is counting heart beats and has a built in alarm when I've hit what ever number it's decided is how long I need to sleep. At my old rate, that would be 6,480 beats an hour, with the new rate being only 5,400 beats an hour. If you take 6,480 and multiply it by 5 (my usual sleep time), then divide it by 5,400 you get 6 - which seems to be the new sleep interval I'm waking up at.
I guess 32,400 heart beats is what I need for sleep!