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Air pollution directly linked to increased dementia risk

dynm

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.

mikeiz404

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.

Avshalom

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

euroderf

Another Red state theory about Blue cities ?

goalieca

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.

mikeiz404

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.

hn_throwaway_99

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.

bitmasher9

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

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

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.

firesteelrain

Dementia rates in Miami Dade are among the highest in the country while Utah is on the low end. What is striking is that Utah has worse air quality, which is a known risk factor, yet still shows lower prevalence.

Why is that?

dragonwriter

Because where people live in retirement doesn’t always reflect where they lived while gathering exposure, and particularly Florida is a place that attracts retirees and perhaps most especially retirees with respiratory health issues (which, like dementia, are influenced by air quality they qere exposee to over their earlier life.)

chongli

Gotta control for age. Even if air pollution is a major cause of dementia, the disease takes decades to appear.

Utah has the highest birth rate and therefore the youngest population of the 50 states (median age 31.5 years). Florida is not the oldest state, but it's near the top (median age 42.7 years).

biophysboy

Dementia by state comparisons that look at prevalence above age 65 give the conclusion for Utah & Florida

AvAn12

Also need to adjust for moving. A lot of people retire to Florida but would have accumulated exposures in wherever they lived most of their working life.

Mistletoe

There are obviously lots more factors affecting dementia than air quality.

Also Utah has worse air quality than Miami? Where in Utah? My trips to Utah I remember pristine air but of course I didn’t have an air monitor on board other than my nose.

Edit: Oh I see

>Utah, particularly in urban areas like the Wasatch Front, frequently experiences worse air quality than Miami. Utah's air quality issues are often caused by unique geographical and meteorological conditions. In winter, temperature inversions trap cold, polluted air in the valleys, leading to high levels of particulate matter (PM2.5) pollution. In the summer, heat and sunlight can create high levels of ground-level ozone. The American Lung Association has ranked cities in the Salt Lake City-Provo-Orem area among the worst for ozone and short-term particle pollution.

>In contrast, Miami's air quality is generally "Good" throughout the year, with occasional exceptions. The primary pollutants are also PM2.5 and ozone, but the geographical and weather conditions do not contribute to the same level of pollutant trapping as in Utah. The city has programs in place for air quality monitoring and standards.

gausswho

Salt Lake is a ticking time bomb as it evaporates and exposes heavy metals downwind to major population centers.

sleepyguy

Perhaps there are more elderly people in Miami-Dade.

What we should be asking is why aren't countries like China, India, and a lot of others in Asia suffering catastrophic rates of Dementia?

firesteelrain

Good point. If air quality is a risk factor then how much?

idiotsecant

China's population skew heavily to middle age, whereas the US population pyramid is more like a population rectangle. It's entirely possible that they have an epidemic of dementia, but for a combination of social and demographic reasons that doesn't show in the data. Getting honest health data out of China, for example, is going to be pretty difficult.

https://en.m.wikipedia.org/wiki/File:China_population_sex_by...

https://www.populationpyramid.net/united-states-of-america/2...

maldonad0

Life is psychologically worse in the cities.

bichiliad

I'd argue that's only true if you ignore loneliness in areas outside of cities. I would have a hard time living somewhere that I didn't run into people.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6179015/

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jl6

Do we see reducing rates of dementia in cities like London which have dramatically improved their air quality over the last ~80 years?

phoenixhaber

I'd like to know the effects of air pollution on at risk populations that use inhalable drugs or smoke as well. I believe the results would be much worse.

Potentially related

https://m.slashdot.org/story/446420

EDIT commenting to child so as not to start a flame war. Lung scarring, emphasema, bronchial illness and so forth can cause the lungs to trap particulates in the lungs longer than they should over the long term this exacerbating health risks. It definitely makes sense.

cluckindan

Not all inhalable drugs are the same. Also, not all inhalations are the same.

Your idea could hold for people who smoke cigarettes or use combustion-heated pipes to consume hard drugs like meth or crack, or for people who smoke a lot of poor quality cannabis, especially without any kind of filtering.

It probably doesn’t hold for people who use a dry herb vaporizer to consume cannabis, since the method of consumption doesn’t generate PM2.5 or combustion gases, and the volatile constituents of cannabis are well established to have local and systemic anti-inflammatory effects.

hopelite

That does not make any sense to me. Now [inhalable] drug users and smokers are "at risk populations" and it's not the drug use or the direct inhaling of smoke, soot, and ash…usually without filtration…that is the issue and problem, but the air pollution is the thing they need to worry about?

But maybe you will be happy to hear that the rates of pollution in the whole European civilization block are orders of magnitude lower than non-European blocks[1]

[1] https://elements.visualcapitalist.com/mapped-air-pollution-l...

neom

Anyone knowledgable on this research area able to enlighten me on how pesticides are included (nor not) in these air particulate studies? In my head PM studies are primality focused on combusted stuff? Do pesticides factor into PM readings in a geography? I ask because I seem to recall there being some articles linking pesticides to dementia/Parkinson.

Havoc

Only so much you can do about ambient pollution in your city.

Looking carefully at your cooking situation is worthwhile though. Was horrified by the spike in readings from stuff like steak in a pan

skybrian

An air purifier is pretty cheap and will cut down on indoor pollution from cooking a lot. Or at least that’s how it seemed from the somewhat unreliable sensor I was using.

https://www.nytimes.com/wirecutter/reviews/best-air-purifier...

dynm

FWIW, I think the wirecutter's quality for air purifiers is pretty bad, and likely more influenced by affiliate payments than science: https://dynomight.net/ikea-purifier/

thadk

I tried the cheap IKEA model and with my severe dust mite allergies the model was insufficient in comparison to calm my sixth sinus-bound sense.

My main suspicion: In my last 3 abodes with pre-1955 construction in East Coast, the pre-filter on the top Wirecutter pick needs to be cleaned 3x per carbon filter replacement in order to reduce largest particle accumulation on the carbon or HEPA filters.

The inexpensive IKEA model did not have a viable and easily cleaned pre filter as far as I could figure out.

FollowingTheDao

I am homeless, I live in a minivan, and I have a solar battery charger with a small carbon filter/HEPA air filter that I use every night and it helps me so much. I am a very "sensitive" person to many things in the environment, but many times while traveling i find myself in the midst of wildfire smoke. (I also carry a facemask respirator for the same reason).

ZYbCRq22HbJ2y7

Are there studies showing indoor air pollution from cooking in a residential setting is linked to dementia?

csallen

Study: Household fuel use and motoric cognitive risk syndrome among older adults: Evidence from cohort study and life course analysis

Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC12413735/

Conclusion: "Clean fuel use for cooking and transitioning from solid to clean fuels decreases MCRS risk among older adults. Moreover, earlier adoption of clean cooking fuels is associated with a lower prevalence of MCRS in later life..."

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Study: Association between cooking fuels and mild cognitive impairment among older adults from six low- and middle-income countries

Link: https://www.nature.com/articles/s41598-022-17216-w

Conclusion: "In this large representative sample of older adults from multiple LMICs, unclean cooking fuel and a lack of chimney or hood when cooking were associated with a higher risk of MCI..."

---

Study: Household air pollution from solid fuel use as a dose-dependent risk factor for cognitive impairment in northern China

Link: https://www.nature.com/articles/s41598-022-10074-6

Conclusions (summarized by ChatGPT):

> People who use solid fuels (like wood, coal, or crop residue) for cooking or heating tend to do worse on cognitive tests compared to those who use clean fuels (like electricity or natural gas). This effect shows up across several areas of thinking, but the biggest impacts were on attention (for cooking) and orientation (for heating).

> The more often people currently use solid fuel stoves, the worse they do on attention-related tasks. For example: if someone cooks with a solid fuel stove 100 extra days in a year, their attention score drops by about 0.05 points (a small but measurable decline).

> Long-term exposure matters too. For every 5 extra years of solid fuel stove use (over the past 20 years), people scored about 0.07 points lower in attention tests. In other words: the longer you’ve been exposed, the worse your performance tends to be.

krapht

I've seen media reports from China about elevated lung cancer rates in non-smoking women. Just as scary, IMO. That being said, Chinese cooking makes much greater usage of stir-frying, and it's well known that most residential ventilation hoods are wholly inadequate for the task.

Havoc

Not sure - it may very well be a different kind of pollution, but the raw PM2.5 values definitely look scary fast with any kind of "dry" cooking where you're browning anything

jodrellblank

The raw PM2.5 values also skyrocket with just boiling tap water, on my Ikea Vindstyrka. Which makes me question how useful it is, presumably even with "dry" cooking a lot of meats and vegetables have water in them?

https://www.ikea.com/gb/en/p/vindstyrka-air-quality-sensor-s...

FollowingTheDao

Good question, but I will say yes just based on the science I know. The type of pollutant does not matter, it is whatever effects heat shock proteins to effect protein folding.

Heat shock proteins (and cold shock proteins) are affected by more than temperature, but temperature is really important as well.[1][2]

[1] https://pubmed.ncbi.nlm.nih.gov/21848409/ [2] https://academic.oup.com/biomedgerontology/article/80/4/glae...

ajkjk

Well studies like this are often directed at policymakers, who actually can do something about it.

lazide

Policy makers generally only give a damn if someone else makes them - or they get something from it.

tim333

They can do the old fashioned make things better to make the voters happy and get reelected. In London the mayor has brought in a lot of anti pollution measures and although the tabloids and right wing media go on about how awful he is, he gets reelected, including my voting.

This thing says roadside ppm2.5 is down from 17 to 8 in central where I live https://www.theguardian.com/environment/2025/mar/07/london-a...

FollowingTheDao

And lobbyists are also directed at those policy makers...which is the bigger problem.

Big spikes in soft money group spending in 22 and 24 elections...

https://www.opensecrets.org/industries/indus?cycle=2024&ind=...

jader201

Wouldn't we see dementia occurrence higher among cooks, then? Or do we?

it_citizen

What level of PM2.5 are they considering? I cannot read the full study

hopelite

It feels like manipulative lying to me when they show the distribution of PM2.5 in the USA through that heat map, where the scale of pollution only goes to 15 when the most non-European block countries are way higher than 15.

[1] https://elements.visualcapitalist.com/mapped-air-pollution-l... polluted place

bamboozled

I've heard the argument made that it's better to stop burning fossil fuel, even if you're a climate change denier for reasons like this.

Even if you think climate change is a hoax, why not reduce pollution anyway?

graemep

I agree. It also reduces the world's dependence on unstable regions.

However, some things that are regarded as renewable (e.g. wood burning, such as the notorious Drax power station in the UK) are more polluting than fossil fuels. Personally I doubt they are even effective at CO₂ reduction. What we need is clean energy.

FollowingTheDao

> It also reduces the world's dependence on unstable regions.

Do you think the world might have made these regions unstable because they have the oil?

acdha

It’s definitely a combination of both but I think oil wealth is inherently destabilizing because it tends to be concentrated in areas which were not previously rich and densely populated (most of the world by area) and because the way the market works allows a relatively small number of people to be wealthy without much local support compared to, say, high-end manufacturing which require lots of skilled workers and local investment. Norway is basically the only example of a petrostate where the money is invested in the betterment of the entire country.

graemep

Yes. Not just the rest of the world wanting influence over the oil supply, resources. Natural resources have harmful effects: making currencies uncompetitive, corruption as people compete for a share of the wealth rather than creating new wealth..

https://moneyterms.co.uk/dutch-disease/

lazide

The middle east was literally roving bands of desert Bedouins and warring religious states long before fossil oil was known to be useful, let alone of major geopolitical importance.

Have people meddled since? Of course. Such is how power works. But you'd have to go back to Roman times to find a period of stability in the middle east, and the factors that led to that have nothing to do with Oil.

hereme888

I'm on that boat. Though no one denies that the climate changes (but rather argue the about degree of human contribution and climate warming), destroying the beauty of nature and polluting the environment should go against global human conscience.

melling

“The climate is always changing”

Yes, those people are mostly imbeciles.

They argue that because Obama has a house near the ocean… and because people fly…

You can have a discussion with them but be prepared to start over in the same place the next time the subject comes up.

hereme888

I think it's imbecile for self-righteous people to not spare a few moments of patience to politely try to correct those who were exposed to wrong information that caters to their bias. It's almost guaranteed that you also believe some sort of ridiculous conspiracy or bias, just like everyone else.

Maybe try listening to them. After all, scientists did switch from "global warming" to an unspecific term like "climate change", which gives them a reason for distrust. Same for other aspects of scientific notion, like distrust against scientists when they and politicians tried to cover up information on COVID and COVID vaccines.

globular-toast

The people who benefit from the status quo are also the people who have the power to change it, and they don't have to live in the polluted areas.

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ck2

directly related, really hoping AirGradient got their US warehouse setup before the tariff implosion blocked every other country postal deliveries

mc32

Does this imply that in 30 years or more we should expect spikes in China, India and other places with exceptional air pollution?

I don't doubt it and they could expect other implications if the pollution also included heavy metals and other chemicals in the air, water and land.

elric

Hopefully China will improve its care of dementia patients. N=1, but a Chinese friend's mother has dementia, and basically the family is expected to care of her full time, there seem to be no facilities (at least not for regular non-rich folks), and even getting a diagnosis was apparently a very hush-hush affair. Seems like it's something that isn't talked much about over there? Again, N=1.

hollerith

The air pollution in China and India was already awful 30 years ago, so "spike" is not be best choice of word. "Continuation of a high level of dementia" would be better.

mc32

I guess it would be a large and massive upswell in the coming decades because dementia isa trailing indicator and takes decades to have effect on populations. China only started pumping out massive amounts of dirty pollution in the mid 90's and China probably in the 2010s or so, so the impact is yet to hit them but if the conclusions are correct then wow...

hollerith

I remember reports of terrible air pollution in China in the 1990s. China is burning much more coal now than it did then, and has about a thousand times more cars, but since the 1990s they've also instituted controls on how much air pollution a car or a unit of coal produces.

FollowingTheDao

In my opinion, the reason air pollution effects dementia risk is through activation of Heat Shock Proteins and I think it is the most valuable place to be investing in research.

Heat Shock Proteins in Alzheimer’s Disease: Role and Targeting

https://pmc.ncbi.nlm.nih.gov/articles/PMC6163571/

hereme888

It seems to be multifactorial. Per an OpenEvidence query, which cites many recent studies:

"In summary, the mechanism of PM2.5-induced brain damage involves entry via the olfactory system and BBB, activation of glial cells, neuroinflammation, oxidative stress, BBB disruption, and downstream neurodegenerative changes."