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Light exposure at night predicts incidence of cardiovascular diseases

https://www.medrxiv.org/content/10.1101/2025.06.20.25329961v1
77•gnabgib•5h ago

Comments

patrickhogan1•4h ago
Each participant wore a wrist light tracker for 1 week.
ekianjo•3h ago
that seems very short
bracketfocus•2h ago
It is fairly short, but seems like enough time to get a baseline of habits across nearly 90,000 participants.
cluckindan•4h ago
Preprint not peer reviewed.

Also: ”A.J.K.P. and S.W.C. are co-founders and co-directors of Circadian Health Innovations PTY LTD.”

Lemme guess, looking for funding.

thimkerbell•3h ago
What can we do about the tendency of research articles to get their big flash of publicity before undergoing peer review?
cryptonector•1h ago
We need to make it a lot cooler for researchers to not do original research all the time but to do replication and peer review. We should also demand publication of failures -- it's ok to fail, but only if you publish about the failure.

The whole publish-or-perish culture is a disaster that incentivizes cheating.

It should be considered just as valuable to have a few grad students working on replication as on original research, and that should not hurt the students' prospects.

zer00eyz•1h ago
> We need to make it a lot cooler for researchers to not do original research all the time but to do replication and peer review.

This should be the work of grad students, not cranking out another paper or slaving for professors.

> We should also demand publication of failures -- it's ok to fail, but only if you publish about the failure.

I really want to have a journal that just publishes interesting duds. Someone else might look at your methodology and get their own idea.

cryptonector•16m ago
> > We need to make it a lot cooler for researchers to not do original research all the time but to do replication and peer review.

> This should be the work of grad students, not cranking out another paper or slaving for professors.

But the professors need to arrange for this.

kazinator•18m ago
Stop reading non-peer-reviewed stuff and sharing links to it?
frtannar•2h ago
The best thing to do is to take commonly held knowledge and make a study out of it.

Maybe the next study could be “live king cobra in the bed results in sleep reduction”.

Probably a book and a TED talk to go with it.

roenxi•12m ago
Eh, you never know with studies. They did this one to serve as a classic counterexample: https://www.bmj.com/content/363/bmj.k5094

You can almost see the grin as they wrote up the results.

hammock•2h ago
So was Moderna? Means nothing
pazimzadeh•13m ago
Peer review doesn't tell you if the data is valid or not. they published their methodology and anyone is free to repeat the study.

Peer review just checks for obvious errors in study design, asks for more info if needed, and decides whether the paper is a good fit for the journal.

Watson and Crick's paper describing the structure of DNA wasn't peer reviewed. if you think they're wrong, try it for yourself and publish the results.

When a few groups all get the same result then you can be confident about the claims made. until then, it's just kind of interesting to think about, which is fine.

> A.J.K.P. and S.W.C. are co-founders and co-directors of Circadian Health Innovations PTY LTD

I do agree that this paper alone should not be used to help sell a product. But it looks like this paper just confirms previous findings using more rigorous methodology (see background):

"Light at night causes circadian disruption, (21–23) and is therefore a potential determinant of cardiovascular disease risk. Higher risks for coronary artery disease (24) and stroke (25) have been observed in people living in urban environments with brighter outdoor night light, as measured by satellite. Brighter night light has been cross-sectionally related to atherosclerosis, (26,27) obesity, hypertension, and diabetes (28) in small but well-characterized cohorts, using bedroom (26,27) and wrist-worn (28) light sensors. Moreover, experimental exposure to night light elevates heart rate and alters sympathovagal balance. (29) However, current evidence linking night light with cardiovascular risk is mostly within small cohorts, or relies on geospatial-level measurements of outdoor lighting, rather than measures of personal light exposure. (30,31)"

croes•4h ago
So use the toilet in the dark?
_heimdall•4h ago
Do you have to turn the light on to use the toilet?
joe_the_user•4h ago
No but I think many people in fact turn the light on when using the toilet.
Krasnol•3h ago
I do have to, this is why I bought one of those IKEA smart bulbs and made it dark and blue. If I get up at night, I use my watch for light.
brador•3h ago
Why blue and not red/orange?
kwertyoowiyop•3h ago
Gotta look for large spiders under the seat.
abrookewood•3h ago
Hazards of living in Australia ...
zoom6628•2h ago
In HK village houses the spiders are outside ... we look for snakes swimming up from septic tanks (yes they are still used even in some new village houses) or coming through bath drain that goes to outside drain (yes still a thing).
goopypoop•2h ago
Do you have to leave the bed?
trollbridge•3h ago
I've always wondered about people who say that... there's enough light (particularly when it's not a new moon) to see to go the bathroom, but maybe my eyes adjust to the light better?
croes•1h ago
Unless you use shutters so the room is completely dark
greenavocado•3h ago
Red light
schrodinger•1h ago
I use iPhone flashlight on mild mode…
lunarcave•4h ago
> including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk

Wondering how much of this is due to geography and air quality. City centers have relatively bad air quality and a high amount of ambient lighting at night, compared to non urbanized areas.

The cardiovascular effects of poor air quality is arguably well understood.

danielschreber•3h ago
My bet is that cardiovascular problems cause light exposure at night.
trollbridge•3h ago
Most studies pull from urban populations and usually contrasting with a rural population is done for a demographic comparison. (Most people also live in cities.) The study was careful to use personal light monitoring, so urban residents who nonetheless find ways to live/sleep in the dark would be included in the study.
patrakov•4h ago
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.

Is this a medical condition that has a name?

1oooqooq•3h ago
does it make a difference if it's warm or blue light?
patrakov•1h ago
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.
xattt•1h ago
6500k? Deliberately in the home??

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)?

patrakov•8m ago
I don't know why 6500K is preferred here.
lr4444lr•3h ago
Nyctophobia.
codingrightnow•3h ago
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.
giraffe_lady•2h ago
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.
Buttons840•2h ago
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.
schrodinger•1h ago
Vampirism.
mpnsk1•11m ago
Have you tried exposing yourself to an hour or two of darkness before you sleep?
etimberg•3h ago
Is this detecting people who work overnights?
loeg•2h ago
Almost certainly some kind of 3rd variable, yeah.
giraffe_lady•2h ago
I believe so yes. They tracked hours of light exposure at night over a week, and found this result in the 90-100th percentile. The 90th percentile here is pretty much going to be people working at night yeah.
readthenotes1•3h ago
If the article had said regularly having to go to work before 9:00 a.m. predicts incidence of cardiovascular disease, would we be having the same conversation?
trollbridge•3h ago
Good catch, although there are plenty of studies and even metastudies on that topic (eg https://pmc.ncbi.nlm.nih.gov/articles/PMC11129786/ ); generally speaking, the healthiest people are those who work "normal" day shifts with "normal" hours (full time; not part time; no overtime).
3eb7988a1663•21m ago
Isn't that just a rough proxy for wealth? Outside of the coke-fueled hedge fund manager, the poor are more likely to have over-time/shift-work/irregular work hours. Your standard office drone can have a consistent work/sleep schedule.
Sporktacular•2h ago
Couldn't find the actual light levels associated with relative most/least bright.
softgrow•38m ago
It's in Table 1, of the paper. The "safe" night-time level for the bottom 50% of the population is surprising low, 0-1.21 lux. I've been sleeping for years with 10-20 lux (inner city, blinds open so I can enjoy the city lights). Maybe I'll need to close the blinds?
cjensen•2h ago
Under the "adjusted for established risk factors" they do not list an adjustment for age. I don't understand that -- doesn't age also correlate with insomnia frequency and cardiovascular disease?
alister•2h ago
Several comments here mentioned shift work as a possible explanation.

The paper concedes that shift work is unhealthy[1] but claims that shift work doesn't explain their finding[2]. And their conclusion is "avoiding night light may be a promising approach for preventing cardiovascular diseases," but without telling us why. It's going to be fascinating if there's a mechanism by which sleeping with light can cause heart disease.

[1] "Evidence demonstrates higher risks of adverse cardiovascular events, coronary heart disease, heart failure, atrial fibrillation, and mortality due to cardiovascular disease in rotating shift workers."

[2] "Following separate adjustments for pre-existing diabetes, hypertension, high BMI, high cholesterol ratio, short, long, or inefficient sleep, and exclusion of shift workers, the relationships of night light with cardiovascular risks were attenuated but remained statistically significant for all outcomes except stroke."

idiotsecant•1h ago
I would make the comment about correlation and causation but I don't think it matters.
bilsbie•1h ago
That sucks I keep a lamp on when I sleep.
ziofill•41m ago
How do they know the causal link? Can it be that people who stay up late sleep less and this causes issues, and there being light is only a consequence of staying up late?
kazinator•19m ago
Is this light exposure imposed by the experiment on random subjects, or is it something coming from their lifestyle?

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