4 ms·

This article repeats the common mistake of conflating correlations and causality. The main results are (1) that PM2.5 exposure is correlated with dementia in hu

by dynm 1y ago

This article repeats the common mistake of conflating correlations and causality. The main results are (1) that PM2.5 exposure is correlated with dementia in humans, (2) some experimental results with mice. This does not establish causality in humans. The paper is careful to stay juuuust on the right side of the line by carefully using "associated" in the right places. But the press release discards that pretense at rigor and jumps straight to full-on claims of causality in people: > Long-term exposure accelerates the development of Lewy body dementia and Parkinson’s disease with dementia in people who are predisposed to the conditions. I think it's entirely possible (perhaps even likely) that this is true. But the paper does not show it.

bitmasher9 1y ago
Why is this brought up here every time an association article is mentioned, every undergraduate that took a statistics course has covered the difference between correlation and causation. We do population level correlation studies because sometimes a double blind study is unethical, and double blind studies is the bar for establishing causation in the medical community. We cannot give one person randomly worse air to breath, and even if it were experimentally feasible it would be ethically impossible because there is strong suspicion we would be harming the subjects. Let’s discuss the actual data. The dose dependent result that was found is an indicator of a strong relationship. There is a clear potential mechanism of action (Air -> Lungs -> Bloodstream -> Brain). This isn’t a controversial result in the literature, it’s more evidence for what we already know —- air pollution is very bad.
- dynm 1y ago
  You seem to be responding as if I claimed that population-level correlational studies are bad, or that I claimed that air pollution is not bad for you. But I did not claim either of those things. What I claimed is that this press release takes a population-level correlational study and presents it in a misleading way that implies causation was established. Which this press release most certainly does.
  - bitmasher9 1y ago
    The correlation != causation argument at large is usually a sophomoric dismal of valuable data, and I’d rather see discussion on the data or specifics to research methodology then this meta criticism. Ultimately both exaggerating pop-sci articles and dismissive comments are contributing to public distrust of science.
    - dpkirchner 1y ago
      Maybe the thought-terminating cliche should be posted as a comment by a bot at the top of every submission so there's a home for this sort of complaint.
    - deleted 1y ago
      [deleted]
- bossyTeacher 1y ago
  > This isn’t a controversial result in the literature, it’s more evidence for what we already know —- air pollution is very bad. It is certainly controversial for individuals whose way of life (see non-electric car-centric society) is being questioned by this science. Just look at some of the cynic answers in this thread pretending that air pollution is not bad
  - lazide 1y ago
    Just because air pollution is bad, doesn’t mean it is bad in this way. It could just as easily be that some other lifestyle thing is causing dementia AND leading to living in areas with worse pm2.5. Especially since pm2.5 tends to be higher in areas with higher population densities, near roads, industrial areas, etc. Hell, maybe the underlying major risk factor is actually time spent in the car. Or repeated viral exposures of a specific type. Or a specific type of air pollution. Either way, it’s not like everyone is going to be moving out of high pm2.5 areas anytime soon, or that we’ll be able to just solve the sources of pollution right now even if it is the cause.
    - bitmasher9 1y ago
      How is pm2.5 not something we can have a direct impact on based on environmental laws?
      - lazide 1y ago
        Ask California and all the wildfires.
        bitmasher9 1y ago
        How is wildfire frequency and severity not directly impacted by regulation?
        lazide 1y ago
        Wildfires are already illegal in California. As is producing a lot of noxious smoke! They even have an entire (rather large) government division (CALFIRE) responsible for stopping them. For some reason, nature DGAF. Or do you have some other policy proposal? Banning lightning or fire perhaps? Making trees illegal?
goalieca 1y ago
The maps in the article wasn’t even super clear when you inspect it visually. Didn’t read the study but it can’t be that strongly correlated.
- hn_throwaway_99 1y ago
  I was going to say something similar. Obviously I was just taking a visual look and not doing any rigorous analysis, but California certainly sticks out like a sore thumb. It has many areas in the Central Valley and Southern California with very high PM2.5 levels, but no "purple" areas with high dementia levels in the state. I also just read the article and not the study but I'd hope they give an explanation for that glaring outlier. I'd be interested to compare the disease map with a map of average income, because at first glance the disease data looks to be correlated with wealth, and we already have tons of research that shows that wealth is one of the biggest determinants of health outcomes in the US.
  - selimthegrim 1y ago
    New Orleans is another one.
- mikeiz404 1y ago
  I noticed this too. I do wonder what it would look like if you controlled for relocation (moving to another region and then developing symptoms), disease onset (both maps are for the same time ranges), and the types of pm 2.5 exposure.
Avshalom 1y ago
Oh yeah, sure definitely it's just as likely that people predisposed to dementia move to places with high air pollution...
- euroderf 1y ago
  Another Red state theory about Blue cities ?
- lentil_soup 1y ago
  Probably not that, but it could be something else that also correlates with pollution like living in big cities, or working in a factory, walking more/less, noise levels, lifestyle, etc
- romaaeterna 1y ago
  Well, in some cases we know that they do. Dementia is linked to diabetes. And diabetes risk is increased for African-Americans. And African-Americans live in high-pollution urban areas for entirely historical reasons. So some amount of the causation here does go in the way opposite to what a person might naively suspect.
  - JumpCrisscross 1y ago
    > Dementia is linked to diabetes. And diabetes risk is increased for African-Americans. And African-Americans live in high-pollution urban areas for entirely historical reasons A is correlated with B. B is causally correlated with C, i.e. C causes B. (C is correlated with D.) Hence C causes A. Let’s replace. Flowers are correlated with bees. Bees are caused by hives. (Hives are correlated with trees.) Hence, hives cause flowers. Loosely, yes. Formally, no.
    - romaaeterna 1y ago
      We know that diabetes causes some amount of dementia and that flowers cause no amount of bees. And so on. Your example is specious, and obviously so.
  - 1y ago
mikeiz404 1y ago
It is unfortunate that the title and subheading of the article use a causal phrasing. Fortunately the body of the article does maintain the correct distinction.
dropacid 1y ago
Another fossil fuel shill
jvanderbot 1y ago
The Parkinson's Plan talks extensively about the risk factors associated with the disease, and discussed the link between air pollution and the disease. They say that it is a trigger / cause that only sometimes works for reasons unknown (paraphrasing). Is a "sometimes cause" still causal?
npunt 1y ago
(OP makes a good point, just going on a slight tangent here) We really need a term that sits between correlation and causation in situations where data is difficult to come by. There's such a huge rift of meaning between these terms, and too often 'correlation is not causation' gets wheeled out in a room of people that already know that and are trying to figure out the nuances. How about plausal? Aka it's rather plausible that there is a causal relationship between two things but causality is hard to prove. "Air quality and dementia have a plausal relationship". The bar for plausation is much lower, yet many correlates still won't meet it. "Bad air quality causes dementia" is a categorically different statement than "ice cream sales cause shark attacks", if we establish the category of plausal relationships.

by dynm 1y ago

bitmasher9 1y ago

Why is this brought up here every time an association article is mentioned, every undergraduate that took a statistics course has covered the difference between correlation and causation. We do population level correlation studies because sometimes a double blind study is unethical, and double blind studies is the bar for establishing causation in the medical community. We cannot give one person randomly worse air to breath, and even if it were experimentally feasible it would be ethically impossible because there is strong suspicion we would be harming the subjects. Let’s discuss the actual data. The dose dependent result that was found is an indicator of a strong relationship. There is a clear potential mechanism of action (Air -> Lungs -> Bloodstream -> Brain). This isn’t a controversial result in the literature, it’s more evidence for what we already know —- air pollution is very bad.

dynm 1y ago
You seem to be responding as if I claimed that population-level correlational studies are bad, or that I claimed that air pollution is not bad for you. But I did not claim either of those things. What I claimed is that this press release takes a population-level correlational study and presents it in a misleading way that implies causation was established. Which this press release most certainly does.
- bitmasher9 1y ago
  The correlation != causation argument at large is usually a sophomoric dismal of valuable data, and I’d rather see discussion on the data or specifics to research methodology then this meta criticism. Ultimately both exaggerating pop-sci articles and dismissive comments are contributing to public distrust of science.
  - dpkirchner 1y ago
    Maybe the thought-terminating cliche should be posted as a comment by a bot at the top of every submission so there's a home for this sort of complaint.
  - deleted 1y ago
    [deleted]
bossyTeacher 1y ago
> This isn’t a controversial result in the literature, it’s more evidence for what we already know —- air pollution is very bad. It is certainly controversial for individuals whose way of life (see non-electric car-centric society) is being questioned by this science. Just look at some of the cynic answers in this thread pretending that air pollution is not bad
- lazide 1y ago
  Just because air pollution is bad, doesn’t mean it is bad in this way. It could just as easily be that some other lifestyle thing is causing dementia AND leading to living in areas with worse pm2.5. Especially since pm2.5 tends to be higher in areas with higher population densities, near roads, industrial areas, etc. Hell, maybe the underlying major risk factor is actually time spent in the car. Or repeated viral exposures of a specific type. Or a specific type of air pollution. Either way, it’s not like everyone is going to be moving out of high pm2.5 areas anytime soon, or that we’ll be able to just solve the sources of pollution right now even if it is the cause.
  - bitmasher9 1y ago
    How is pm2.5 not something we can have a direct impact on based on environmental laws?
    - lazide 1y ago
      Ask California and all the wildfires.
      - bitmasher9 1y ago
        How is wildfire frequency and severity not directly impacted by regulation?
        lazide 1y ago
        Wildfires are already illegal in California. As is producing a lot of noxious smoke! They even have an entire (rather large) government division (CALFIRE) responsible for stopping them. For some reason, nature DGAF. Or do you have some other policy proposal? Banning lightning or fire perhaps? Making trees illegal?

goalieca 1y ago

The maps in the article wasn’t even super clear when you inspect it visually. Didn’t read the study but it can’t be that strongly correlated.

hn_throwaway_99 1y ago
I was going to say something similar. Obviously I was just taking a visual look and not doing any rigorous analysis, but California certainly sticks out like a sore thumb. It has many areas in the Central Valley and Southern California with very high PM2.5 levels, but no "purple" areas with high dementia levels in the state. I also just read the article and not the study but I'd hope they give an explanation for that glaring outlier. I'd be interested to compare the disease map with a map of average income, because at first glance the disease data looks to be correlated with wealth, and we already have tons of research that shows that wealth is one of the biggest determinants of health outcomes in the US.
- selimthegrim 1y ago
  New Orleans is another one.
mikeiz404 1y ago
I noticed this too. I do wonder what it would look like if you controlled for relocation (moving to another region and then developing symptoms), disease onset (both maps are for the same time ranges), and the types of pm 2.5 exposure.

Avshalom 1y ago

Oh yeah, sure definitely it's just as likely that people predisposed to dementia move to places with high air pollution...

euroderf 1y ago
Another Red state theory about Blue cities ?
lentil_soup 1y ago
Probably not that, but it could be something else that also correlates with pollution like living in big cities, or working in a factory, walking more/less, noise levels, lifestyle, etc
romaaeterna 1y ago
Well, in some cases we know that they do. Dementia is linked to diabetes. And diabetes risk is increased for African-Americans. And African-Americans live in high-pollution urban areas for entirely historical reasons. So some amount of the causation here does go in the way opposite to what a person might naively suspect.
- JumpCrisscross 1y ago
  > Dementia is linked to diabetes. And diabetes risk is increased for African-Americans. And African-Americans live in high-pollution urban areas for entirely historical reasons A is correlated with B. B is causally correlated with C, i.e. C causes B. (C is correlated with D.) Hence C causes A. Let’s replace. Flowers are correlated with bees. Bees are caused by hives. (Hives are correlated with trees.) Hence, hives cause flowers. Loosely, yes. Formally, no.
  - romaaeterna 1y ago
    We know that diabetes causes some amount of dementia and that flowers cause no amount of bees. And so on. Your example is specious, and obviously so.
- 1y ago

mikeiz404 1y ago

It is unfortunate that the title and subheading of the article use a causal phrasing. Fortunately the body of the article does maintain the correct distinction.

dropacid 1y ago

Another fossil fuel shill

jvanderbot 1y ago

The Parkinson's Plan talks extensively about the risk factors associated with the disease, and discussed the link between air pollution and the disease. They say that it is a trigger / cause that only sometimes works for reasons unknown (paraphrasing). Is a "sometimes cause" still causal?

npunt 1y ago

(OP makes a good point, just going on a slight tangent here) We really need a term that sits between correlation and causation in situations where data is difficult to come by. There's such a huge rift of meaning between these terms, and too often 'correlation is not causation' gets wheeled out in a room of people that already know that and are trying to figure out the nuances. How about plausal? Aka it's rather plausible that there is a causal relationship between two things but causality is hard to prove. "Air quality and dementia have a plausal relationship". The bar for plausation is much lower, yet many correlates still won't meet it. "Bad air quality causes dementia" is a categorically different statement than "ice cream sales cause shark attacks", if we establish the category of plausal relationships.