What is it they say about correlation?

I'm not a scientist but in a group of 60 year olds doom-scrolling in bed vs those who just read a book (or even just go to sleep) is it outside the realm of possibly that the former group may be more likely have other aspects to their life that are unhealthy general?

That's a very good point. There are lots of potential confounders here. But I also want to point out that this study isn't a shot in the dark for random correlations -- there are theoretical reasons to believe that poor sleep hygiene would increase the risk of diabetes. Cortisol is tightly coupled to the sleep-wake cycle and to blood sugar levels. It is known to be causative of diabetes in certain rare disease (Cushing disease, for example) and strongly associated in garden variety type 2 diabetes. The article passingly references this (but it uses the more general term glucocorticoid).

aHR and RR are broadly comparable.

Key findings from the diabetes study (this one):

    Night light exposure in the 90-100th percentile (brightest nights): aHR = 1.53 [1.32-1.77]
    Night light exposure in the 70-90th percentile: aHR = 1.39 [1.24-1.57]
    Night light exposure in the 50-70th percentile: aHR = 1.29 [1.14-1.46]

Key findings from N=1 million birth control use impact on depression study (https://scholar.google.com/scholar_lookup?journal=JAMA+Psych...) :

    Combined oral contraceptives: RR = 1.23 [1.22-1.25] for first use of antidepressants
    Progestin-only pills: RR = 1.34 [1.27-1.40] for first use of antidepressants
    Patch (norgestrolmin): RR = 2.0 [1.76-2.18] for first use of antidepressants
    Vaginal ring (etonogestrel): RR = 1.6 [1.55-1.69] for first use of antidepressants

In my opinion, if you are okay with birth control, you are probably okay with using light at night.

Light exposure was measured by a "wristwatch" worn on the dominant hand, so reading a book is going to get coded as more light than smartphone use probably.

It also seems the sample size was so large that it could easily convert these differences into a significant p-value. Is there a statistical compensation to make confounding factor adjustment more stringent with larger sample size?

We know that sleep is important. We know that light can mess up your sleep. It stands to reason that if it can mess up your important sleep, it can have negative consequences down the line.

In this study, day light is defined as light during 07:30–20:30, and night light, 00:30–06:00. They arrived at those definitions by doing a factor analysis.

so what is the time in between?

Data from times outside those 2 ranges were ignored, is my guess.

Twilight

I sleep in a light room wearing a mask. So my eyes are dark, but skin gets some light. My understanding is that melatonin is regulated by light through the eyes, so that should count as dark for circadian rhythm purposes. But I’d appreciate any corrections.

Seems like this study measured it with a wristwatch, which is a poor proxy for either light on the eyes or skin.

Would be great to see a study on using LED vs incandescent bulbs in this regard.

I switched to halogen incandescent at my desk and I feel much better.

There is something in the LED and neon light that get me dizzy, it might be the spectrum, it might be the flashing at 120hz.

We also need near infrared light for our mitochondria to work properly and we created an environment devoid of it.

A fair number of people seem to be sensitive to flicker that's too fast for conscious perception.

Would be difficult, because what is led? Is my tuned-to-low-temp Hue bulb the same as a cheap blueish led bulb?

Looking at the light spectrum, it's closer to the cheap, blueish led, yes.

Or any limited vs full specturm lighting for that matter. But blue level might be particularly interesting to correlate.

Maybe you could only run the green-red leds at nighttime?

You can use halogen bulbs if old school incandescent is not sold where you live.

They're still available and popular in many countries, often significantly cheaper than LED bulbs.

They are still sold, but now often as 'heaters' or specialty bulbs, when in fact normal, to skirt regulations.

It’s interesting that night light exposure is so important, but the much brighter day light seems to have almost no effect.