I hear Peat describing two ends of the spectrum of sleep:
- One, restful and restorative, involving "slow wave" sleep that, on an EEG, shows up as delta waves, and with a minimum of cortisol even upon waking; and
- Two, what Peat calls a "torpor," which has very little slow wave sleep, and is marked by high cortisol and metabolic shutdown -- by analogy, a torpor might be like hibernating rather than sleeping.
While healthy people with little metabolic stress spend 20% of the night in "slow wave" sleep, people who are in the early stages of metabolic decline spend only 10% in that stage. As metabolic death approaches, it is down to less than 5%, and sometimes maybe 2%.
Other factors notwithstanding, you could look at a person‚Äôs EEG chart for a night and get an estimate of how old they are, in metabolic terms, from the amount of "slow wave" sleep.
So, an interesting question might be, does sleeping on the floor with a mat increase "slow wave" sleep? To find out, you could wear an EEG to bed, or try one of the wrist monitors (Basis, Fitbit, Onefit, etc.).
You could also measure your reaction times the next day, which correlate with how much slow wave sleep you are getting day to day.
But waking up and not feeling like you need more sleep is some indication, too. For example, after nights with lesser deep sleep, you are more likely to choose to self-administer sleeping pills. (See http://www.nature.com/npp/journal/v20/n3/full/1395251a.html