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    Air pollution directly linked to increased dementia risk

    (www.nature.com)
    275 points rntn | 14 comments | 07 Sep 25 13:13 UTC | HN request time: 0s | source | bottom
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    dynm ◴[07 Sep 25 15:20 UTC] No.45158964[source]▶
    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.

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    1. Avshalom ◴[07 Sep 25 17:08 UTC] No.45160008[source]▶
    Oh yeah, sure definitely it's just as likely that people predisposed to dementia move to places with high air pollution...
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    2. euroderf ◴[07 Sep 25 17:10 UTC] No.45160024[source]▶
    Another Red state theory about Blue cities ?
    3. lentil_soup ◴[07 Sep 25 17:21 UTC] No.45160169[source]▶
    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
    4. romaaeterna ◴[07 Sep 25 17:44 UTC] No.45160435[source]▶
    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.

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    5. JumpCrisscross ◴[07 Sep 25 17:51 UTC] No.45160516[source]▶
    > 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.

    replies(1): >>45160742 #
    6. badpun ◴[07 Sep 25 17:53 UTC] No.45160535[source]▶
    There might be some hidden variable at play that's correlated both air pollution that is really causing the dementia. Like street noise. Not saying it's likely, but it's not impossible.
    7. saltcured ◴[07 Sep 25 18:03 UTC] No.45160632[source]▶
    It's even worse... dementia sufferers are the ones emitting these particles ;-)
    replies(1): >>45160821 #
    8. romaaeterna ◴[07 Sep 25 18:13 UTC] No.45160742{3}[source]▶
    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.
    9. tylerflick ◴[07 Sep 25 18:22 UTC] No.45160821[source]▶
    Thanks, got a good laugh out of this one.
    10. Aurornis ◴[07 Sep 25 18:28 UTC] No.45160873[source]▶
    You’re being sarcastically dismissive, but this is a real possibility. The real world is complicated and disorders with environmental effects are often multi-factorial.

    Air pollution might not be the direct cause, it might be a proxy measurement that is correlated with some other factor or factors that contribute to dementia risk. For example, do areas with higher air pollution measurements also have higher or lower rates of something else that is actually contributing to the dementia directly? Do they simply correlate with overall development of the area, and therefore areas with poor pollution numbers also have high levels of water pollution?

    11. zosima ◴[07 Sep 25 18:31 UTC] No.45160906[source]▶
    People who are poorer and have worse health are predisposed to live in cheaper dwellings, many of which are closer to roads and thus more noisy and with more air pollution.

    People who are poorer and have worse health, also have an increased incidence of dementia, seemingly independently of the number of particles in their dwellings.

    replies(1): >>45160981 #
    12. jvanderbot ◴[07 Sep 25 18:39 UTC] No.45160966[source]▶
    Outlive (book) talks extensively about dementia risk and Alzheimer's as "type 3 diabetes".
    13. Insanity ◴[07 Sep 25 18:41 UTC] No.45160981[source]▶
    I’m not sure this is a completely valid statement. Take Ontario - the most expensive places to live are in Toronto with the most traffic, the cheapest places are more rural without that heavy traffic and thus less pollution.
    14. jvanderbot ◴[07 Sep 25 18:45 UTC] No.45161009[source]▶
    In rural areas it's pesticides. And in urban areas it's dry cleaners and air pollution. Parkinson's Plan is worth a read for the kind of details you can't get on a single article