Wouldn’t exposure to bright outdoor light just be a proxy for living in a highly urban environment? How did they come to the conclusion that it’s the light itself and not everything else that...
Wouldn’t exposure to bright outdoor light just be a proxy for living in a highly urban environment? How did they come to the conclusion that it’s the light itself and not everything else that comes with city living like air/water pollution, noise, sleep disruption, stress, etc ?
That's certainly something they were conscious of in their analysis - they looked at different pollution particulates and provided hazard ratios for those as well. They did try to account for...
That's certainly something they were conscious of in their analysis - they looked at different pollution particulates and provided hazard ratios for those as well. They did try to account for pollution levels and compare how that might correlate with light exposure, but their analysis suggests that light exposure at night can affect cerebrovascular health independently from pollution.
And I want to emphasize here: they did not conclude that light itself is the sole risk factor for these cerebrovascular pathologies. Also, this is a very rudimentary, gross sampling. Regardless, we already know that light at night can have big impacts on health whether it's due to impaired sleep or broader disruptions to circadian rhythm.
Yeah, it sounds like it would be difficult to isolate specifically the light variable, especially when they are using satellite images to define the levels of light pollution. More light means...
Yeah, it sounds like it would be difficult to isolate specifically the light variable, especially when they are using satellite images to define the levels of light pollution. More light means more urban generally, and a lot of other things change when you make that transition, including noise and air pollution.
Noise specifically seems important to me. As described in this video on the issue of noise pollution, it too can disrupt sleep and therefore lead to a range of health problems including hypertension. I don't doubt that light does as well, but I'm not sure it's the biggest problem, and it's more easily solved (with blackout curtains for example) than noise is.
It's one piece of a bigger puzzle and there are lots more things to fix in the urban environment than light.
A large body of evidence has been built up around the fact that exposure to light at night time, particularly blue light, has adverse impacts on our health on a multitude of fronts. A lot of that...
A large body of evidence has been built up around the fact that exposure to light at night time, particularly blue light, has adverse impacts on our health on a multitude of fronts. A lot of that seems to look at what people are doing in their homes as the use of entertainment devices has become an ubiquitous component of our lives.
I'm passionate about light pollution because it has many negative effects on animals and plants as well as the hampering of viewing a full night sky, and this is just another nail in the coffin for me. I don't think that we should get rid of street lights or things like that - they provide a very real, practical purpose in terms of safety. But maybe there are ways we can shift how we use lights. For instance, maybe transitioning to far red wave-lengths that could reduce impact on many animals, while still allowing us to see - unfortunately, it would still have some impact on plants.
There isn't a perfect solution, but curious to people's thoughts on it.
I'm not necessarily against the interventions you mention but is there actually evidence that exposure to light at night is directly causing these adverse health impacts? Because unless I've...
A large body of evidence has been built up around the fact that exposure to light at night time, particularly blue light, has adverse impacts on our health on a multitude of fronts.
I'm not necessarily against the interventions you mention but is there actually evidence that exposure to light at night is directly causing these adverse health impacts? Because unless I've missed something, it seems more like lower quality/quantity of sleep has adverse health impacts and increased exposure to light at night impacts that.
So impairments on sleep are certainly one factor, but the major component is disruptions to our circadian rhythm which go beyond sleep. Our circadian rhythms are regulated by the perception of...
However, I want to gently push back a little bit about "directly causing". I see where your interpretation is coming from, and it certainly could be poor phrasing on my part (and please correct me if I read you wrong); it doesn't seem like the energy from light is physically causing these effects, but it's the perception of it during times when our bodies are prepping for sleep, which yes I wholeheartedly agree. But to me, that's just the mechanism of how light at night impacts health. We know that light at night disrupts the cellular clocks in the hypothalamus that coordinate the processes that are tied to our circadian rhythm, and we know that this can result in a cascade of issues primarily revolving around sleep disruption and metabolic disorders.
I guess to further extend your line of thought, is there a way we could decouple light at night from disruptions to our circadian rhythm? I don't think we could without either massive changes to our bodies, beyond just the circadian cells in the hypothalamus, which would require a much better understanding of our nervous system and the rest of our physiology as well as a clearer picture on our genetics. Certainly not anytime soon.
Probably not! But I think I'd prefer a paper that consciously at least tried to at least decouple it from quantity of sleep at the very least -- even just including hours of sleep per night as a...
I guess to further extend your line of thought, is there a way we could decouple light at night from disruptions to our circadian rhythm?
Probably not! But I think I'd prefer a paper that consciously at least tried to at least decouple it from quantity of sleep at the very least -- even just including hours of sleep per night as a control variable.
This would at least help in figuring out how much of these effects is just losing sleep and how much is from other effects on your circadian rhythm. This could affect how someone prioritizes different lifestyle changes.
Hopefully this comment is coherent, I myself only got like 5 hours of sleep last night 😅
So they assessed outdoor light exposure by using satellite imagery. That seems like a strange way to conduct the study, but it sounds like it's probably cheaper than assessing indoor lighting, but...
So they assessed outdoor light exposure by using satellite imagery. That seems like a strange way to conduct the study, but it sounds like it's probably cheaper than assessing indoor lighting, but still seems tenuous enough that it might not mean much scientifically. Did they just measure the light visible from space at the addresses of each participant? In addition to ignoring blackout curtains, as the article mentioned, that also seems odd because it only tracks the light that is going into space. Lights aimed at the ground will look dimmer than lights that glow upward as well.
I don't think the purpose of the study was to assess indoor lighting. We already have pretty good evidence that light at night isn't great for us. I think this is more looking at a matter of...
I don't think the purpose of the study was to assess indoor lighting. We already have pretty good evidence that light at night isn't great for us. I think this is more looking at a matter of degree. Perhaps when you're at home you take all these precautions to limit light in your house, but there could still be this time where you are exposed to light as you commute home from work or are out grocery shopping. Or even just considering people who spend more time out at night. They wanted to identify if there were any broad trends in outdoor light exposure and incidences of cerebrovascular disease. This is not causal, but the scientific value is that there might be a link we hadn't considered, which would require further investigation.
Regarding how the assess light exposure, I pulled this from the supplementary material from the research article:
Outdoor Light At Night (LAN) was obtained from the global nighttime light images produced by the Earth Observation Group. Monthly cloud-free day and night band (DNB) composite images are publicly accessible at https://eogdata.mines.edu/products/vnl/. These products are based on cloud-free nighttime imagery synthesized by the Visible and Infrared Imaging Suite (VIIRS) DNB on the joint polar satellite system, excluding data impacted by stray light. The VIIRS-DNB can capture nightlight at wavelengths of 500 to 900 nm with a spatial resolution of 15 × 15 arc-seconds, rasterized to night light luminance equivalent to ~500m 36. Outdoor LAN was provided in radiometric units (nW/cm2/sr) 37 and monthly average levels of outdoor LAN for each participant were extracted according to geographic address with a buffer of 500m using ArcGIS software (version: 10.8). In this cohort study, we extracted outdoor LAN monthly mean values during 2013-2017 (before the baseline). Finally, we assigned 1-year average levels of outdoor LAN before baseline to each participant.
So it sounds like they looked at a 500 m area centered around participants' addresses, but it might be some jargon I'm misinterpreting. I'm not sure how they distinguish between light pointing towards space or the ground. As you point out the latter is dimmer, and reflected light might also have different properties compared to emitted light.
I don't think the point is about traveling to the grocery store (artificially illuminated place to artificially illuminated place). I think it's more about light coming in and disturbing sleep.
I don't think the point is about traveling to the grocery store (artificially illuminated place to artificially illuminated place). I think it's more about light coming in and disturbing sleep.
It certainly could be one interpretation and is likely a primary factor, but since they noted that they didn't check indoor illumination they can't make any claims about that. They can only...
It certainly could be one interpretation and is likely a primary factor, but since they noted that they didn't check indoor illumination they can't make any claims about that. They can only identify a connection between outdoor light levels and stroke incidence.
The analysis of data including six years of follow-up with participants found:
-1,278 people developed cerebrovascular disease, including 777 ischemic (clot-caused) stroke cases and 133 hemorrhagic (bleeding) stroke cases.
-People with the highest levels of exposure to outdoor light at night had a 43% increased risk of developing cerebrovascular disease compared to those with the lowest levels of exposure.
-People with the highest levels of exposure to particulate matter 2.5 (PM2.5 is primarily emissions from combustion of gasoline, oil, diesel fuel or wood) had a 41% increased risk of developing cerebrovascular disease compared to participants with the lowest levels of exposure to PM2.5.
-Participants with the highest levels of exposure to PM10 (PM10 is primarily from dust and smoke) had a 50% increased risk of developing cerebrovascular disease compared to those with the lowest exposure to PM10.
-Participants with the highest exposure to nitrogen oxide (emissions from cars, trucks and buses, power plants and off-road equipment) had a 31% higher risk of developing cerebrovascular disease compared to those with the lowest exposure.
Wouldn’t exposure to bright outdoor light just be a proxy for living in a highly urban environment? How did they come to the conclusion that it’s the light itself and not everything else that comes with city living like air/water pollution, noise, sleep disruption, stress, etc ?
That's certainly something they were conscious of in their analysis - they looked at different pollution particulates and provided hazard ratios for those as well. They did try to account for pollution levels and compare how that might correlate with light exposure, but their analysis suggests that light exposure at night can affect cerebrovascular health independently from pollution.
And I want to emphasize here: they did not conclude that light itself is the sole risk factor for these cerebrovascular pathologies. Also, this is a very rudimentary, gross sampling. Regardless, we already know that light at night can have big impacts on health whether it's due to impaired sleep or broader disruptions to circadian rhythm.
Yeah, it sounds like it would be difficult to isolate specifically the light variable, especially when they are using satellite images to define the levels of light pollution. More light means more urban generally, and a lot of other things change when you make that transition, including noise and air pollution.
Noise specifically seems important to me. As described in this video on the issue of noise pollution, it too can disrupt sleep and therefore lead to a range of health problems including hypertension. I don't doubt that light does as well, but I'm not sure it's the biggest problem, and it's more easily solved (with blackout curtains for example) than noise is.
It's one piece of a bigger puzzle and there are lots more things to fix in the urban environment than light.
A large body of evidence has been built up around the fact that exposure to light at night time, particularly blue light, has adverse impacts on our health on a multitude of fronts. A lot of that seems to look at what people are doing in their homes as the use of entertainment devices has become an ubiquitous component of our lives.
I'm passionate about light pollution because it has many negative effects on animals and plants as well as the hampering of viewing a full night sky, and this is just another nail in the coffin for me. I don't think that we should get rid of street lights or things like that - they provide a very real, practical purpose in terms of safety. But maybe there are ways we can shift how we use lights. For instance, maybe transitioning to far red wave-lengths that could reduce impact on many animals, while still allowing us to see - unfortunately, it would still have some impact on plants.
There isn't a perfect solution, but curious to people's thoughts on it.
I'm not necessarily against the interventions you mention but is there actually evidence that exposure to light at night is directly causing these adverse health impacts? Because unless I've missed something, it seems more like lower quality/quantity of sleep has adverse health impacts and increased exposure to light at night impacts that.
So impairments on sleep are certainly one factor, but the major component is disruptions to our circadian rhythm which go beyond sleep. Our circadian rhythms are regulated by the perception of light, and this is used to coordinate our bodies for sleep but also to regulate energy stores, repair tissue, synaptic remodeling, among other processes. For instance, people who work the night shift are more likely to be overweight and get type II diabetes, which could indicate a mechanism independent of sleep assuming these people are getting a full night's rest, and even short disruptions to circadian rhythm through light at night can impact glucose metabolism.
However, I want to gently push back a little bit about "directly causing". I see where your interpretation is coming from, and it certainly could be poor phrasing on my part (and please correct me if I read you wrong); it doesn't seem like the energy from light is physically causing these effects, but it's the perception of it during times when our bodies are prepping for sleep, which yes I wholeheartedly agree. But to me, that's just the mechanism of how light at night impacts health. We know that light at night disrupts the cellular clocks in the hypothalamus that coordinate the processes that are tied to our circadian rhythm, and we know that this can result in a cascade of issues primarily revolving around sleep disruption and metabolic disorders.
I guess to further extend your line of thought, is there a way we could decouple light at night from disruptions to our circadian rhythm? I don't think we could without either massive changes to our bodies, beyond just the circadian cells in the hypothalamus, which would require a much better understanding of our nervous system and the rest of our physiology as well as a clearer picture on our genetics. Certainly not anytime soon.
Probably not! But I think I'd prefer a paper that consciously at least tried to at least decouple it from quantity of sleep at the very least -- even just including hours of sleep per night as a control variable.
This would at least help in figuring out how much of these effects is just losing sleep and how much is from other effects on your circadian rhythm. This could affect how someone prioritizes different lifestyle changes.
Hopefully this comment is coherent, I myself only got like 5 hours of sleep last night 😅
So they assessed outdoor light exposure by using satellite imagery. That seems like a strange way to conduct the study, but it sounds like it's probably cheaper than assessing indoor lighting, but still seems tenuous enough that it might not mean much scientifically. Did they just measure the light visible from space at the addresses of each participant? In addition to ignoring blackout curtains, as the article mentioned, that also seems odd because it only tracks the light that is going into space. Lights aimed at the ground will look dimmer than lights that glow upward as well.
I don't think the purpose of the study was to assess indoor lighting. We already have pretty good evidence that light at night isn't great for us. I think this is more looking at a matter of degree. Perhaps when you're at home you take all these precautions to limit light in your house, but there could still be this time where you are exposed to light as you commute home from work or are out grocery shopping. Or even just considering people who spend more time out at night. They wanted to identify if there were any broad trends in outdoor light exposure and incidences of cerebrovascular disease. This is not causal, but the scientific value is that there might be a link we hadn't considered, which would require further investigation.
Regarding how the assess light exposure, I pulled this from the supplementary material from the research article:
So it sounds like they looked at a 500 m area centered around participants' addresses, but it might be some jargon I'm misinterpreting. I'm not sure how they distinguish between light pointing towards space or the ground. As you point out the latter is dimmer, and reflected light might also have different properties compared to emitted light.
I don't think the point is about traveling to the grocery store (artificially illuminated place to artificially illuminated place). I think it's more about light coming in and disturbing sleep.
It certainly could be one interpretation and is likely a primary factor, but since they noted that they didn't check indoor illumination they can't make any claims about that. They can only identify a connection between outdoor light levels and stroke incidence.
Key findings: