With a solid month of sleep data now captured (using my Zeo Sleep Coach), I've been able to tease out an important contributor to how rested I feel when I wake up in the morning.
I had initially assumed that my body would allow me to sleep enough hours each night in order for it to fully recuperate. In other words, if I go to bed late I figured that my body would just sleep in a bit longer and wake me up a bit later. But based on the recordings from my Zeo, this turned out to not be the case at all. In fact, no matter how late I went to bed, my body would just 'wake up' at right around 6am the next morning.
So even if I went to bed very late - 2am for example - I would still wake up around 6am. Of course, I didn't feel well rested, but I was never able to go back to sleep. Once the eyes were open, they stayed that way.
That told me that if I wanted to feel more rested in the mornings, that my only realistic option was to go to bed earlier. So that is what I did - adjusted by bedtime to 10pm, no exceptions. Sure enough, I still woke up just about 6am, but I felt much better rested.
The results of adjusting my bed time to 10pm are shown in the chart below. I made the shift on Thursday, 8/27. Notice how my total sleep time jumped by over an hour? I could definitely feel the difference:
A bit of research into why this might be the case lead me to this article: Differential rescue of light- and food-entrainable circadian rhythms. In the study, the scientists show how circadian rhythms are strongly influenced by feeding/meal times. As it turns out, I eat dinner very consistently at 6pm each night. So my speculation is that my circadian clock says "Jason - you will wake up 12 hours after your last meal, no matter how much time you spent sleeping."
Although I'm not sure meal time dictates my wakeup time completely, it sure does seem to be a strongly contributing factor.
