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Light exposure at night predicts incidence of cardiovascular diseases
- patrickhogan1 1y agoEach participant wore a wrist light tracker for 1 week.
- ekianjo 1y agothat seems very short
- bracketfocus 1y agoIt is fairly short, but seems like enough time to get a baseline of habits across nearly 90,000 participants.
- trollbridge 1y agoN>88,000, so it has a huge sample size. Most people have the same patterns of sleep and nighttime/daytime habits week to week.
- cluckindan 1y agoPreprint not peer reviewed.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 1y agoWhat can we do about the tendency of research articles to get their big flash of publicity before undergoing peer review?
- cryptonector 1y agoWe 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 1y 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 1y 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.
- adrianN 1y agoThe people paying the professors need to arrange for this
- cryptonector 1y agoOften that's us.
- kazinator 1y agoStop reading non-peer-reviewed stuff and sharing links to it?
- nudgeOrnurture 1y agoan 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.
- frtannar 1y agoThe 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 1y agoEh, you never know with studies. They did this one to serve as a classic counterexample: https://www.bmj.com/content/363/bmj.k5094 https://www.bmj.com/content/363/bmj.k5094 You can almost see the grin as they wrote up the results.
- dotancohen 1y agoTo 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 https://www.bmj.com/content/363/bmj.k5094
- dvfjsdhgfv 1y agoOK, 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).
- sebastiennight 1y agoThis 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
- hammock 1y agoSo was Moderna? Means nothing
- pazimzadeh 1y agoPeer 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)"
- Dylan16807 1y ago> 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.
- 1y ago
- dotancohen 1y ago> 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?
- nurettin 1y ago> 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.
- krisoft 1y ago> 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?
- Llamamoe 1y agoThe result is, however, consistent with existing science.
- cluckindan 1y agoHowever, there is likely a correlation between nighttime light exposure and living in a city, on a lower floor, next to a street with medium or heavy traffic. There is likely also a significant correlation between living in such conditions and exposure to pollution, especially inhaled particulate matter. Such a correlation also holds elsewhere: living in a high-rise means no streetlights outside your window, and also yields cleaner air than living at or near street level; living in the countryside means practically no light pollution, but also much less traffic and thus much less particulates in the air. Inhaled particulate matter is a leading cause of cardiovascular disease. See e.g. https://www.sciencedirect.com/science/article/pii/S0735109718383554 https://www.sciencedirect.com/science/article/pii/S073510971...
- Llamamoe 1y agoI've skimmed lots of studies about the relationship between light and health in the past. In both humans and other animals, our internal sleep-wake clocks are synchronized to the day-night cycle through light exposure(and indeed, without it aren't even 24h-long), and have broad implications for mood, wakefulness, metabolism, and general health. I well might have seen something about cardiovascular problems specifically, though I don't remember.
- croes 1y agoSo use the toilet in the dark?
- _heimdall 1y agoDo you have to turn the light on to use the toilet?
- joe_the_user 1y agoNo but I think many people in fact turn the light on when using the toilet.
- Krasnol 1y agoI 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.
- kwertyoowiyop 1y agoGotta look for large spiders under the seat.
- abrookewood 1y agoHazards of living in Australia ...
- zoom6628 1y ago
- lunarcave 1y 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 1y agoMy bet is that cardiovascular problems cause light exposure at night.
- renmillar 1y agoAlmost believable. You'd probably instinctively want fresh air when your heart's acting up.
- trollbridge 1y agoMost 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.
- lowwave 1y ago>> 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.
- ethan_smith 1y agoThe 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.
- 1y ago
- patrakov 1y agoSorry 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 1y agodoes it make a difference if it's warm or blue light?
- patrakov 1y agoI 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 1y ago6500k? 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 1y agoI don't know why 6500K is preferred here.
- lr4444lr 1y agoNyctophobia.
- codingrightnow 1y agoMaybe 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.
- etimberg 1y agoIs this detecting people who work overnights?
- loeg 1y agoAlmost certainly some kind of 3rd variable, yeah.
- giraffe_lady 1y agoI 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.
- trollbridge 1y agoThe percentiles of 50-60, 60-70, 70-80, and 80-90, however, are obviously not shift workers (unless they're shift workers working in the dark); you compare the lowest percentile of daylight light exposure to the highest percentile of nighttime light exposure, and see that there just aren't that many shift workers present in the study. About 13% of the UK population is considered to be nighttime workers. We can safely assume nighttime workers aren't represented in the 50%-90% percentile, because there simply aren't enough of them to go around, and would not be statistically significant.
- readthenotes1 1y agoIf 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 1y agoGood catch, although there are plenty of studies and even metastudies on that topic (eg https://pmc.ncbi.nlm.nih.gov/articles/PMC11129786/ 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 1y agoIsn'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.
- trollbridge 1y agoIt's not, because the study specifically disambiguated for socioeconomic status. The effect was also seen outside of the night worker population (13% of the population).
- cjensen 1y agoUnder 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?
- Sporktacular 1y agoCouldn't find the actual light levels associated with relative most/least bright.
- softgrow 1y agoIt'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?
- trollbridge 1y agoIt's listed right in there. Search for "lux".
- alister 1y agoSeveral 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."
- WD-101000 1y ago> 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.
- idiotsecant 1y agoI would make the comment about correlation and causation but I don't think it matters.
- trollbridge 1y agoThe study is claiming correlation.
- aaron695 1y ago[dead]
- bilsbie 1y agoThat sucks I keep a lamp on when I sleep.
- ziofill 1y agoHow 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?
- circularfoyers 1y ago> 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/10.1101/2025.06.20.25329961v1.full-text https://www.medrxiv.org/content/10.1101/2025.06.20.25329961v...
- ltbarcly3 1y agoIt does not claim a causal link, just correlation.
- trollbridge 1y ago"Correlation is not causation!" is one of the sillier things that people say when a study comes out with meaningful, interesting data. If nobody ever finds correlations in the first place, then it won't be possible to figure out causation - and we certainly do want to eventually find more causation for things like heart attacks, don't we?
- NoPicklez 1y agoI agree. I see it constantly when a study comes out all of these statistics students come out of the wood work and say "Correlation doesn't mean causation" without any other thought. The study clearly claims only a correlation and absolutely, correlations help focus attention to try and find causal links in the future.
- ltbarcly3 1y agoI agree, correlation certainly hints at a relationship. However, I think you are just being triggered by past traumas, because nobody said that here.
- kazinator 1y agoIs this light exposure imposed by the experiment on random subjects, or is it something coming from their lifestyle?
- perilunar 1y agoAs 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.
- nudgeOrnurture 1y ago> 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.
- jamesholden 1y agoWhat about all the people that live in the North, like Finland, etc?
- pwdisswordfishz 1y agoDid they control for coffee drinking?
- seydor 1y agobut i leave only my screen on
- dubeye 1y agoI thought this was well established? My cardiologist always asks about sleep, isn't it obvious a darker room makes for better sleep
- bregma 1y agoI 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.
- amelius 1y agoMakes sense, people who work late tend to be more stressed.
- trollbridge 1y agoOnly 13% of the population works nights, yet people with high levels of exposure to light at night were far more than 13% of the sample.