Going to mention my crackpot theory on why polyphasic sleeping might end up killing you again:
Polyphasic sleep drastically reduces the amount of deep sleep you get. Sleep helps the body heal. Human aging and mortality seem to be modeled well by a Gompertz curve, where the thing that kills you at old age is the body's diminished healing ability, which lets cancer precursors in the body stay unfixed long enough to grow into something that kills you.
So for all we know, throwing out 4 hours of deep sleep daily(*) for years on end might make you look a lot more like an 80-year-old, as far as the Gompertz curve modeled mortality is concerned.
ETA: (*) All non-REM sleep isn't deep (SWS) sleep, see below. According to online hypnograms of sleep stages, the deepest sleep stages mostly happen during the first three hours of sleep, so a sleep cycle that maintains a 3-hour core sleep should be significantly better than a sleep cycle like Uberman that runs solely on power naps. The 4 hours of deep sleep bit is probably an oversimplification.
ETA2: If the first three hours of sleep are the most important for making the body heal, would a sleep cycle where you have two core sleeps daily, for example 3 to 6 AM and 3 to 6 PM, keep you more healthy than a single 8-hour sleep?
I'm currently adapting to polyphasic sleep and have been consistently getting about 2h of deep sleep during my ~3h core (according to my Zeo). Contrast that with e.g. gwern's Zeo charts which show about 1h of SWS during an entire night of 8 hours. Note that even when his ZQ (~sleep quality) was about 100 (a "good" score) he was still getting about an hour.
...and I'm not even fully adapted. That said, I'm currently not getting quite enough REM, but I'm working on this.
This is the public group instrumental rationality diary for the week of August 20th. It's a place to record and chat about it if you have done, or are actively doing, things like:
Or anything else interesting which you want to share, so that other people can think about it, and perhaps be inspired to take action themselves. Try to include enough details so that everyone can use each other's experiences to learn about what tends to work out, and what doesn't tend to work out.
Thanks to everyone who contributes!
Last week's diary; archive of prior diaries.