A while back I read Silent Spring, and the author made an interesting note: 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.
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.
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.)
Wouldn't you expect to see more variation between the American and European cohorts if smoking were the culprit?
As is smoking of other things
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.
Is that a poor assumption?
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...
IDK if there's a way to measure who got the most poison though.
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 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.
If only there was something big in the world happening from 1939 to 1945 ...
Diseases (and especially virii) are showing to leave behind WAY more damage than everybody thought. Nutritional stress leaves behind lasting damage as well.
The early cohort being compared went through the Spanish Flu and the Great Depression. Who knows how much damage those left?
I have some friends that had Hashimoto's disease. Type 1 diabetes. Friends with lupus. 4-5 friends that had Guillain-Barre syndrome. My mom died of ITP. I have sarcoidosis. I have friends who for unexplained reasons are 'unwell'
ITP is an interesting one. The antibodies target an enzyme that's needed to keep your blood platelets from binding together in your blood. Thus the idea that you can have autoimmune syndromes that can mess with thousands of different enzymes and proteins. Or stimulate inappropriately. Seriously why not.
I can totally believe that infection with childhood diseases of yore could lead to dementia later in life.
Most flavor compounds in herbs and spices are also neurotoxins, coffee and chocolate contain many neurotoxins, nearly every naturally occurring stimulant or psychoactive substance humans use is a neurotoxins targeting a different creature. We happen to find many of them pleasant or tasty because they evolved to target very distant relatives or we are just weirdos that find mildly poisoning ourselves fun.
Silent Spring leaned far too much on fear and exaggeration which is a disservice to the much more complicated issues we face with synthetic chemistry and controlling our environment.