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Comment by JumpCrisscross | Hacker News Reader

> Pesticides used in the 1960s were neurotoxins, and she feared that they could cause neurological disorders. We now use different pesticides

The "younger generations" in this study were born between 1944 and 1948. (Older, 1890 to 1913.) Pesticides don't explain why those born in the former have less dementia than those born between 1939 and 1943.

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They do if the effects are cumulative.

They additionally cite in the article that perhaps it's smoking that's changed, yet that also didn't really significantly change in public until the 90s.

40 additional years of pesticides/lead/smoking/etc will take their toll.

> They additionally cite in the article that perhaps it's smoking that's changed, yet that also didn't really significantly change in public until the 90s.

Prevalence of smoking in the US peaked at around 45% in the 1950s, and had dropped to around 25% by the 1990s. (Depending on your own age, this may feel wrong because there was a surge in youth smoking from the 80s peaking in the mid-1990s, so its easy for people in a certainnage range to feel like smoking was very prevalent through the 1990s, and then dropped like a rock.)

> Prevalence of smoking in the US peaked at around 45% in the 1950s, and had dropped to around 25% by the 1990s

Wouldn't you expect to see more variation between the American and European cohorts if smoking were the culprit?

And while smoking has plummeted, nicotine usage is resurgent

As is smoking of other things

Interestingly, there's reasonably good basis to suspect nicotine (though not smoking) can reduce rates of neurodegenerative disease like Alzheimer's and Parkinson's.

You are correct but you really need to provide a source when making this claim because it sounds so unbelievable:

https://www.healthline.com/health/alzheimers-dementia/nicoti...

(Not calling healthline a source, but it has links to publications for those interested).

It's important to note, of course, that smoking increases the risk of pretty much every bad health related thing that can happen to you, including dementia. However, using nicotine without smoking might have benefits due to its effects on acetylcholine receptors.

Of course nicotine addiction is one problem and putting ash in your lungs is another

Smoking reduces the risk of dementia because you die first.

I expect the two world wars & a Great Depression might have more to do with it than pesticides or leaded gasoline.

I would think pesticides in the 1890’s through 1930’s were not as dangerous as what came later.

Is that a poor assumption?

It is, mainly because the history of pesticide research has basically been looking for the least harmful pesticides to humans.

Before DDT went into wide use in the 1940s, aersnic based pesticides were common.

Here's a particularly nasty one that was commonly used up until DDT replaced it.

https://en.wikipedia.org/wiki/Lead_hydrogen_arsenate?wprov=s...

My great-grandma is the only one in my family who died of cancer and she used to apply farm chemicals by hand

this is a thousand percent due to lead

The younger generations would've been exposed to much more leaded gasoline per body mass when they were young, whereas the older generations were already at least young adults by the time leaded became commonplace.

The older generation would have been consuming lead arsenic in the form of pesticides at higher rates than the younger generation.

IDK if there's a way to measure who got the most poison though.

I dread to think what diseases the even 'younger generations' are going to get with all the microplastics in just about everything we eat, drink, and in some cases breathe.

Microplastics have recently become understood, but humans have lived with a lot of plastic for many, many decades now.

Wouldn't it most likely be nothing significant? We love plastic because it's so inert..

The problem with microplastics is that it's forever breaking down in very small amount of very reactive substances.

Hell, when chewing gum is made of plastic, I don't think we need to worry about the microplastics in the food.

Why is that? Chewing gum is perfectly avoidable, ingesting food not so much.

>Pesticides don't explain why those born in the former have less dementia than those born between 1939 and 1943

If only there was something big in the world happening from 1939 to 1945 ...

Very loose speculation as a non-biologist. Could it have been that most of the healthy males (e.g. good testosterone levels, and whatever else made virile young males) were away at war, and the men left to father children had some sort of deficiency which also correlates with better protection against dementia?

Probably not. you'd have to prove that people who were able bodied in their youth are less likely to have dementia than people with disabilities or bad physical health. To my knowledge there is no such link. Besides, a big part of this sample was from the US who didn't enter the war before the very end of 41 (December 7th so might as well be 1942). Occupied Europe also didn't really have it's men "away at war". Also, men at war, even during WW1, were able to go back home from time to time, so I don't think the argument holds.

> a big part of this sample was from the US who didn't enter the war before the very end of 41 (December 7th so might as well be 1942). Occupied Europe also didn't really have it's men "away at war"

The nail in the coffin for the hypothesis is the lack of significant variation between the US and European cohorts. Europeans were killed indiscriminately. Our men were selectively slaughtered. If there was a selection effect, you'd expect that to present in the American cohorts and not European ones; that is not observed.

Could they prove this, as well?

> Could it have been that most of the healthy males (e.g. good testosterone levels, and whatever else made virile young males) were away at war

A lot of healthy males were not away at war, because staying and performing their job was important.

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