Sorry for exposing my personal medical data, but... I literally cannot fall asleep without at least some light. So I sleep with lights on. Trying to be like normal people would only make my overall health worse.
Maybe got one of those lights that slowly dim to simulate sunset. You can fall asleep in the light, but it will be dark while you sleep. I have 2 Philips branded ones that have worked well for 11 years now.
If you are from a cold area people needed to keep a camp fire alive throughout the night or they died, I'd bet those would have a hard time sleeping without lights on since their ancestors who did died.
DNA adapts very quickly to such hard selectors, and many populations has lived in such areas for many thousands of years by now.
If you live above 60 parallel, the night light is associated with summer. I also sleep with lights on, because dreams are about summer and happiness.
Worst thing is to wake up in total darkness in strange place. You dont remember were things are, cannot find the light switch, and start panicking, maybe I am gone blind?
Maybe they're exposed to light at night because they're awake at night more often, possibly shift workers, which we already know is unhealthy. I doubt just having light on is causing the effect.
Yes they tracked hours of light exposure (above some threshold? I don't see that they say.) and found this result in the 90-100th percentile. So almost certainly night shift workers.
They grouped the population into percentiles with 0-50% having quite low exposure (0.62 lux median, range of 0-1.21) vs the 90%-100% percentile being 105 lux (range of 48.3-6400). You can compare the daylight light exposure to the nighttime and basically see what a shift worker would be.
But they already deconfounded for shift workers, so that's irrelevant. And they also showed the amount of light exposure for both night and day.
I think it doesn't make any difference. Back in Russia, I used 2700K or 3000K LEDs. Here in the Philippines, high-CRI warm-color LEDs are unobtainable, and the culture exhibits a nearly-universal shift to 6500K indoor lights (unlike in Europe), so I use 6500K, just like everyone else here. It still works.
Is this one of those things where some element is considered desirable in the Western world (e.g. warm white lighting) but is associated with destitution in another culture (because it’s like incandescent lighting)?
Is this a medical condition that has a name?