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)"
> Peer review doesn't tell you if the data is valid or not.
Sure but nobody claimed that.
> Watson and Crick's paper describing the structure of DNA wasn't peer reviewed.
I'd point out that outliers exist but that was before peer review become so popular.
Right now there's a good correlation between competency and peer review.
> if you think they're wrong, try it for yourself and publish the results.
Watson and Crick or the article?
For a balanced discussion of the article, it's reasonable to point out a lack of peer review to give context to what stage this is at. If "try it yourself" is the bar then I guess nobody comments? That doesn't seem like a good way to learn anything.
This creates a perfect setup for manipulation - the high barriers to entry for proper equipment, organization, and funding needed to produce quality reproductions mean that if someone posts fake content that mimics scientific paper formatting and includes all the right academic signals, most people will accept it as legitimate without question.
> Also: ”A.J.K.P. and S.W.C. are co-founders and co-directors of Circadian Health Innovations PTY LTD.”
The other edge of the "not impartial" sword: these are people who are highly familiar, likely experts, in the related field. Who else is more qualified to conduct such a study?
> Who else is more qualified to conduct such a study?
Whoever does not have a monetary interest in the studied subject is the one who is more qualified. Same with smoking related research, same with children's toy paint related research. But the third edge is: These are phases of fraud that societies go through. They will happen, some will think they are legit, some won't, they disappear into some third world country after taking their sum. It always works like that. And that's predictive science right there.
> Whoever does not have a monetary interest in the studied subject is the one who is more qualified.
I’m not really understanding the monetary interest angle. The monetary interest in this subject is the curtain and window-blind manufacturers.
The researches here have a company who sells body worn light sensors. And if their light sensor is good maybe other researchers interested in verifying this phenomena will purchase a few units from them. But they are far from the only company making light sensors. In fact if i want to verify this study i would buy sensors from anyone but them. For the sake of having independent proof free from biases.
> they disappear into some third world country after taking their sum
What sum, please tell me? Where do you see the riches here?
You don’t have to pretend anything. Just go on and explain where you see the monetary incentives with this research and researchers. (If you see them.)
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.
an active, public pre-review discussion. we nurture critical thinking before the nudge.
some charismatic, intelligent dude or dudette or couple with a curious but rather uneducated mind inviting grad students and scientists to discuss studies and pre-prints and so on, constantly babbling scientifically more or less correct nonsense but getting semantically corrected by the guests or something ... ... so viewers can feel "smartypants" and or relate and learn.
I'm sure there's podcasts but I don't listen to podcasts.
The Beth Israel Deaconess Medical Center ran a trial on parachute use to prevent death and major trauma when jumping from aircraft, and gave half the people jumping a placebo (empty backpack) instead of a parachute. No joke.
> Parachutes are routinely used to prevent death or major traumatic injury among individuals jumping from aircraft. However, evidence supporting the efficacy of parachutes is weak and guideline recommendations for their use are principally based on biological plausibility and expert opinion.
Results :
> Parachute use did not significantly reduce death or major injury (0% for parachute v 0% for control; P>0.9). This finding was consistent across multiple subgroups.
Methodology might have an influence on the result:
> Compared with individuals screened but not enrolled, participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001).
Conclusions
> Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention.
Implications
> Should our results be reproduced in future studies, the end of routine parachute use during jumps from aircraft could save the global economy billions of dollars spent annually to prevent injuries related to gravitational challenge.
Limitations
> However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps.
I can already see the YouTube thumbnails: THIS IS THE STUDY PARACHUTE MAKERS DON'T WANT YOU TO SEE
OK, I read the article, wondered a bit, then started to read the responses (first aligning with the one "April Fools' in December?"). I mean, what's the point of asking people to jump from airplanes on the ground, write a study on it, and waste everybody's time
But then, reading other responses, and taking into account the name of the journal, and the fact that it did get published, I realized it's a very good example of a flawed study, where everybody see a flaw because it's evident, whereas in other studies a flaw of the same magnitude might be quite difficult to see (I could give quite a few examples from my field).
> 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.
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.
The study measured personal light exposure via wrist-worn trackers for a week rather than using geographic light pollution data, which would better control for the urban air quality confounding you've identified.
No, measuring light doesn't remove the air quality confounder. Measuring air quality would allow to remove the air quality confounder. What are you smoking?
>> including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk
And also light at night inhibits melatonin production. That along should already be able to lead to all kinds of healthy issues.
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.
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)?
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?
Correlation is not the same as causation. The research indicates a correlation. Assuming causation is a classical mistake with any research.
In any case, light sensitivity and sleep patterns are well linked. If you live far away from the equator, you are dealing with pretty short nights half of the year. I lived in Helsinki for a while. That can really mess up your sleep though some people manage to adapt. There's a reason coffee is popular in places like
I currently live in Berlin. I sleep about 2-3 hours less in the summer than in the winter.
Somehow that works for me. But it's really annoying to be wide awake at 6 when you've set your alarm for 8. I'm literally typing this on my laptop early morning on a Sunday. But it's light very early this time of year.
I've experimented with wearing sleep masks. They really work. But I find them slightly uncomfortable. What works better is just doing sane things like trying to live healthy. Less alcohol, more sport. Etc. Work stress can cause all sorts of issues with that.
> I sleep about 2-3 hours less in the summer than in the winter.
That's not OK, I don't know a single person affected so (live in cca same latitude as Berlin). Have you tried some radical solutions like good window blinds or similar sun blocking mechanisms? I don't mean some cheap crap that still lets strips of light through, I mean full block. Of course if then some chopper or ambulance wakes you up regardless it doesn't matter.
> These relationships were robust after adjusting for established risk factors for cardiovascular health, including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk.
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?
As an inveterate night owl these sorts of results bother me, but if I try to force myself to sleep and wake earlier I feel like shit. Better to listen to my own body than do something because of a population-wide correlation I guess. Or hope, anyway.
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."
> It's going to be fascinating if there's a mechanism by which sleeping with light can cause heart disease.
I suspect everyone in the field already knows the top-level answer: light at night blunts the output of the circadian pacemaker (SCN), with all sorts of downstream effects including control of various hormones. So the levels will be different with light at night. "at night" means biological night. If someone consistently sleeps on some schedule with bright enough light during their awake time, and it's dark during their sleep time, it's fine.
I'm not in the field. I read up on it at one point at a shallow level and talked to some researchers about it informally.
I do not have sleep problems. I can sleep anywhere, light or dark. It is completely obvious to me that ambient light and sleep are uncorrelated in any way.
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.
> Incidence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke
> People with the brightest nights (90-100th percentiles) had significantly higher risks of developing coronary artery disease (adjusted-HR range: 1.23-1.32), myocardial infarction (aHRs: 1.42-1.47), heart failure (aHRs: 1.45-1.56), atrial fibrillation (aHRs: 1.28-1.32), and stroke (aHRs: 1.28-1.30), compared to people with dark nights (0-50th percentiles).
> These relationships were robust after adjusting for established risk factors for cardiovascular health, including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk. Relationships of night light with risk of heart failure and coronary artery disease were stronger for women, and relationships of night light with risk of heart failure and atrial fibrillation were stronger for younger individuals in this cohort.
These relationships were *robust*.
The observed associations between nighttime light exposure and increased incidence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke may be driven by complex and multifactorial pathways. These cardiovascular conditions can arise from numerous interrelated long- and short-term physiological and behavioral factors, making it difficult to isolate the causal role of nighttime light exposure alone.
It is plausible to hypothesize that if individuals in the lower-exposure group were subjected to increased nighttime light exposure under controlled conditions—where all other lifestyle factors remained constant and stress levels were actively managed—their cardiovascular risk might not increase. This would suggest that ambient light exposure at night, in isolation, may not be a direct etiological factor.
Although the study adjusted for a broad range of established cardiovascular risk factors—including physical activity, smoking, alcohol consumption, diet, sleep duration, socioeconomic status, and polygenic risk—these adjustments do not capture acute or chronic variations in psychological stress. Since stress is a known contributor to cardiovascular disease, the inability to directly account for its temporal dynamics represents a potential limitation in the interpretation of these findings.
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?
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?
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).
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.
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?
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).
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.
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)"
> Peer review doesn't tell you if the data is valid or not.
Sure but nobody claimed that.
> Watson and Crick's paper describing the structure of DNA wasn't peer reviewed.
I'd point out that outliers exist but that was before peer review become so popular.
Right now there's a good correlation between competency and peer review.
> if you think they're wrong, try it for yourself and publish the results.
Watson and Crick or the article?
For a balanced discussion of the article, it's reasonable to point out a lack of peer review to give context to what stage this is at. If "try it yourself" is the bar then I guess nobody comments? That doesn't seem like a good way to learn anything.
This creates a perfect setup for manipulation - the high barriers to entry for proper equipment, organization, and funding needed to produce quality reproductions mean that if someone posts fake content that mimics scientific paper formatting and includes all the right academic signals, most people will accept it as legitimate without question.
> Who else is more qualified to conduct such a study?
Whoever does not have a monetary interest in the studied subject is the one who is more qualified. Same with smoking related research, same with children's toy paint related research. But the third edge is: These are phases of fraud that societies go through. They will happen, some will think they are legit, some won't, they disappear into some third world country after taking their sum. It always works like that. And that's predictive science right there.
> Whoever does not have a monetary interest in the studied subject is the one who is more qualified.
I’m not really understanding the monetary interest angle. The monetary interest in this subject is the curtain and window-blind manufacturers.
The researches here have a company who sells body worn light sensors. And if their light sensor is good maybe other researchers interested in verifying this phenomena will purchase a few units from them. But they are far from the only company making light sensors. In fact if i want to verify this study i would buy sensors from anyone but them. For the sake of having independent proof free from biases.
> they disappear into some third world country after taking their sum
What sum, please tell me? Where do you see the riches here?
I'm sorry I can't continue this conversation of pretending the thing right there doesn't exist.
You don’t have to pretend anything. Just go on and explain where you see the monetary incentives with this research and researchers. (If you see them.)
What can we do about the tendency of research articles to get their big flash of publicity before undergoing peer review?
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.
> 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.
> > 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.
The people paying the professors need to arrange for this
Stop reading non-peer-reviewed stuff and sharing links to it?
an active, public pre-review discussion. we nurture critical thinking before the nudge.
some charismatic, intelligent dude or dudette or couple with a curious but rather uneducated mind inviting grad students and scientists to discuss studies and pre-prints and so on, constantly babbling scientifically more or less correct nonsense but getting semantically corrected by the guests or something ... ... so viewers can feel "smartypants" and or relate and learn.
I'm sure there's podcasts but I don't listen to podcasts.
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.
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.
To those who don't follow the link.
The Beth Israel Deaconess Medical Center ran a trial on parachute use to prevent death and major trauma when jumping from aircraft, and gave half the people jumping a placebo (empty backpack) instead of a parachute. No joke.
https://www.bmj.com/content/363/bmj.k5094
This is the best study I've read this year.
The motive behind the study:
> Parachutes are routinely used to prevent death or major traumatic injury among individuals jumping from aircraft. However, evidence supporting the efficacy of parachutes is weak and guideline recommendations for their use are principally based on biological plausibility and expert opinion.
Results :
> Parachute use did not significantly reduce death or major injury (0% for parachute v 0% for control; P>0.9). This finding was consistent across multiple subgroups.
Methodology might have an influence on the result:
> Compared with individuals screened but not enrolled, participants included in the study were on aircraft at significantly lower altitude (mean of 0.6 m for participants v mean of 9146 m for non-participants; P<0.001) and lower velocity (mean of 0 km/h v mean of 800 km/h; P<0.001).
Conclusions
> Parachute use did not reduce death or major traumatic injury when jumping from aircraft in the first randomized evaluation of this intervention.
Implications
> Should our results be reproduced in future studies, the end of routine parachute use during jumps from aircraft could save the global economy billions of dollars spent annually to prevent injuries related to gravitational challenge.
Limitations
> However, the trial was only able to enroll participants on small stationary aircraft on the ground, suggesting cautious extrapolation to high altitude jumps.
I can already see the YouTube thumbnails: THIS IS THE STUDY PARACHUTE MAKERS DON'T WANT YOU TO SEE
OK, I read the article, wondered a bit, then started to read the responses (first aligning with the one "April Fools' in December?"). I mean, what's the point of asking people to jump from airplanes on the ground, write a study on it, and waste everybody's time
But then, reading other responses, and taking into account the name of the journal, and the fact that it did get published, I realized it's a very good example of a flawed study, where everybody see a flaw because it's evident, whereas in other studies a flaw of the same magnitude might be quite difficult to see (I could give quite a few examples from my field).
Grin?
> All authors suffered substantial abdominal discomfort from laughter.
So was Moderna? Means nothing
> 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.
My bet is that cardiovascular problems cause light exposure at night.
Almost believable. You'd probably instinctively want fresh air when your heart's acting up.
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.
The study measured personal light exposure via wrist-worn trackers for a week rather than using geographic light pollution data, which would better control for the urban air quality confounding you've identified.
No, measuring light doesn't remove the air quality confounder. Measuring air quality would allow to remove the air quality confounder. What are you smoking?
>> including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk And also light at night inhibits melatonin production. That along should already be able to lead to all kinds of healthy issues.
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?
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?
Have you tried exposing yourself to an hour or two of darkness before you sleep?
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.
Vampirism.
Nyctophobia.
does it make a difference if it's warm or blue light?
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.
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)?
I don't know why 6500K is preferred here.
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?
Correlation is not the same as causation. The research indicates a correlation. Assuming causation is a classical mistake with any research.
In any case, light sensitivity and sleep patterns are well linked. If you live far away from the equator, you are dealing with pretty short nights half of the year. I lived in Helsinki for a while. That can really mess up your sleep though some people manage to adapt. There's a reason coffee is popular in places like
I currently live in Berlin. I sleep about 2-3 hours less in the summer than in the winter. Somehow that works for me. But it's really annoying to be wide awake at 6 when you've set your alarm for 8. I'm literally typing this on my laptop early morning on a Sunday. But it's light very early this time of year.
I've experimented with wearing sleep masks. They really work. But I find them slightly uncomfortable. What works better is just doing sane things like trying to live healthy. Less alcohol, more sport. Etc. Work stress can cause all sorts of issues with that.
In addition, seasonal disorders are equally common in Madrid and Helsinki, so that cannot explain any difference in sleep disorders.
Btw, did you take a D vitamin supplement and use a light therapy lamp in the mornings?
> I sleep about 2-3 hours less in the summer than in the winter.
That's not OK, I don't know a single person affected so (live in cca same latitude as Berlin). Have you tried some radical solutions like good window blinds or similar sun blocking mechanisms? I don't mean some cheap crap that still lets strips of light through, I mean full block. Of course if then some chopper or ambulance wakes you up regardless it doesn't matter.
> These relationships were robust after adjusting for established risk factors for cardiovascular health, including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk.
There's more details further in the article[1].
[1] https://www.medrxiv.org/content/10.1101/2025.06.20.25329961v...
It does not claim a causal link, just correlation.
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?
As an inveterate night owl these sorts of results bother me, but if I try to force myself to sleep and wake earlier I feel like shit. Better to listen to my own body than do something because of a population-wide correlation I guess. Or hope, anyway.
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."
> It's going to be fascinating if there's a mechanism by which sleeping with light can cause heart disease.
I suspect everyone in the field already knows the top-level answer: light at night blunts the output of the circadian pacemaker (SCN), with all sorts of downstream effects including control of various hormones. So the levels will be different with light at night. "at night" means biological night. If someone consistently sleeps on some schedule with bright enough light during their awake time, and it's dark during their sleep time, it's fine.
I'm not in the field. I read up on it at one point at a shallow level and talked to some researchers about it informally.
I thought this was well established?
My cardiologist always asks about sleep, isn't it obvious a darker room makes for better sleep
I do not have sleep problems. I can sleep anywhere, light or dark. It is completely obvious to me that ambient light and sleep are uncorrelated in any way.
Each participant wore a wrist light tracker for 1 week.
that seems very short
It is fairly short, but seems like enough time to get a baseline of habits across nearly 90,000 participants.
Is this detecting people who work overnights?
Almost certainly some kind of 3rd variable, yeah.
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.
That sucks I keep a lamp on when I sleep.
Makes sense, people who work late tend to be more stressed.
What about all the people that live in the North, like Finland, etc?
Is this light exposure imposed by the experiment on random subjects, or is it something coming from their lifestyle?
> Incidence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke
> People with the brightest nights (90-100th percentiles) had significantly higher risks of developing coronary artery disease (adjusted-HR range: 1.23-1.32), myocardial infarction (aHRs: 1.42-1.47), heart failure (aHRs: 1.45-1.56), atrial fibrillation (aHRs: 1.28-1.32), and stroke (aHRs: 1.28-1.30), compared to people with dark nights (0-50th percentiles).
> These relationships were robust after adjusting for established risk factors for cardiovascular health, including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk. Relationships of night light with risk of heart failure and coronary artery disease were stronger for women, and relationships of night light with risk of heart failure and atrial fibrillation were stronger for younger individuals in this cohort.
These relationships were *robust*.
The observed associations between nighttime light exposure and increased incidence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke may be driven by complex and multifactorial pathways. These cardiovascular conditions can arise from numerous interrelated long- and short-term physiological and behavioral factors, making it difficult to isolate the causal role of nighttime light exposure alone.
It is plausible to hypothesize that if individuals in the lower-exposure group were subjected to increased nighttime light exposure under controlled conditions—where all other lifestyle factors remained constant and stress levels were actively managed—their cardiovascular risk might not increase. This would suggest that ambient light exposure at night, in isolation, may not be a direct etiological factor.
Although the study adjusted for a broad range of established cardiovascular risk factors—including physical activity, smoking, alcohol consumption, diet, sleep duration, socioeconomic status, and polygenic risk—these adjustments do not capture acute or chronic variations in psychological stress. Since stress is a known contributor to cardiovascular disease, the inability to directly account for its temporal dynamics represents a potential limitation in the interpretation of these findings.
Did they control for coffee drinking?
Couldn't find the actual light levels associated with relative most/least bright.
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?
but i leave only my screen on
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?
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).
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.
I would make the comment about correlation and causation but I don't think it matters.
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So use the toilet in the dark?
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?
You must live in the city.
Unless you use shutters so the room is completely dark
Do you have to turn the light on to use the toilet?
Gotta look for large spiders under the seat.
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).
Hazards of living in Australia ...
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.
Why blue and not red/orange?
I did have red but it didn't feel as good as blue.
I've also read somewhere that even the US Navy is changing to blue in their ships for some readability reasons.
No but I think many people in fact turn the light on when using the toilet.
Do you have to leave the bed?
I use iPhone flashlight on mild mode…
Buy one of those darkness-sensing nightlight plugs and leave it in the bathroom. They cost under a $1 a month to run.
Red light