Comment by keeda

Somewhat related, I once met the author of a book about sleep [1] and asked about my specific case. At that time I was splitting half my time across two continents 10 time zones apart but working largely in the same timezone, about 2 - 3 months at a time. That is, every 2 - 3 months I switched from a 1st shift sleep schedule to a "2.5th shift" one. So I asked him how bad that was for my health.

He said that as long as people are mostly regular in their sleep hours, the actual timings don't matter much. However, extended periods of irregular sleep schedules are actually (his words) "classified as a type of carcinogen."

I briefly looked into the evidence at the time but did not find it very concerning. TFA does make a more compelling case by linking it to all-cause mortality.

[1] I believe it was The Sleep Solution by M. Chris Winter, though I may be wrong. I can only remember it had a blue cover, but turns out pretty much ALL books about sleep have a blue cover. ¯\_(ツ)_/¯