In the past few years I went from having relaxed 11AM daily meetings to rigid 8AM meetings, and my sleep has suffered immensely. But nothing else in my life has changed, so it wouldn't show up in my socioeconomic data.
this one selected about 100k people from a dataset of around 500k. All from one country/region (UK)
furthermore they dont measure sleep but they estimate if someone was maybe asleep based data from an accelerometer. so they cannot measure what sleep state someone acheived or if they were actually really sleep or just u know staring at the ceiling in an existential crisis....
These two goals are kind of at odds with one another. We can only get insight into depth of sleep achieved if we bring you into a sleep clinic, but we can't do that for a significant sample size...
If others in the house prefer to sleep from 10-6 and you prefer to sleep from 12-6, but others start making noise a 6, your sleep quality in the last two hours is destroyed. Then over time, it just results in poor sleep regularity, as you cycle between exhaustion and trying to sleep according to your internal clock.
The study authors aren't even purporting to show a casual relationship (i.e. that improving sleep would necessarily reduce mortality), just that irregular sleep predicts mortality.