I wonder how this translates if the irregularity is by choice . I can certainly see why people working back to back night and day shifts, or otherwise frequently being at a sleep debt that was compensated for later, would die younger. But as a freelancer, my sleep schedule is more or less my own. I go to sleep when I'm tired and usually try to sleep as long as I want to. Sometimes that's 11pm-10am, sometimes 6am-11am…
However, I eventually overcame those challenges and created my own schedule to work with, and my sleep cycle became better then onwards.