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"A 2008 peer-reviewed study in the Annals of Neurology, for example, found that TCE is “a risk factor for parkinsonism.” And a 2011 study echoed those results, finding “a six-fold increase in the risk of developing Parkinson’s in individuals exposed in the workplace to trichloroethylene (TCE).”"

It doesn't strike me as fair to dismiss studies like the ones quoted (from the article) as simple correlations.

> It doesn't strike me as fair to dismiss studies like the ones quoted (from the article) as simple correlations.

I didn't see the particular studies and I am not dismissing them out of hand, but I've seen a lot of studies, lost a lot of battles against all sorts of unsound statistical analysis. When I taught Intro Stats, I had no trouble finding examples of what not to do to illustrate in class: Just look at the front page of the campus newspaper which seemed intent on filling pages with bogus "studies".

Again, I am not calling this one[1] bogus, but I am going to point out that study seems to consist solely of finding people who have Parkinson's and have worked around the chemical.

Causality requires (not p) => (not q).

[1]: https://hero.epa.gov/hero/index.cfm/reference/details/refere...

While this is always something to consider, generally, 6-fold increase in risk due to exposure is likely not just a population demographic artifact.

TCE and its relation to Parkinson's has been studied for at least the last 15 years. Though I haven't come across anything definitive on the mechanism of action, there seems to be indication that a combination of TCE or its analogues combined with other risk factors (assumed to be genetic) generates substantial progressive dopaminergic neuron loss, a hallmark of Parkinson's disease progression.

> 6-fold increase in risk due to exposure

Interestingly, the Guardian article does not cite a source for that claim, so it is impossible to evaluate it soundly.

However, just above, it states:

>> the number of people with Parkinson’s has increased 35% the last 10 years

which is completely in line with the increase in at risk population + improved probability of diagnosis.

That doesn't mean there is no link.

This is a very important, often overlooked point.

Also food malnutrition is way less common, than it was before.

But we also are exposed to many new chemicals, not occuring in nature, so we could not adopt to them.

So ... I guess there is no definite, simple answer.

Honestly what good comes out of any “industrial scale” chemical? I think people are screwed because this is _one_ chemical; what about all of the synthetic materials in peoples houses these days (the carpet itself)?

We need to go back to basics here instead of trying to over-science things. Bust out that bottle of vinegar and keep things simple in my opinion.

The whole world runs on industrial scale chemicals. Virtually everything in our modern society relies on them. They are base inputs to almost every chain of goods from foodstuffs to textiles to manufactured items of every sort. Even your vinegar example is primarily produced as an industrial scale chemical.

A comparison can still be made between the same age cohorts i.e. compare rates of Alzheimer’s for the cohort 60 to 65 year olds. There is always a potential for confounding factors, but if the rates are up 35% for all cohorts then that says something.

Also the beautiful flow graph https://images2.minutemediacdn.com/image/upload/c_fit,f_auto... (graph for US Women I think) does show that after about 70 “mental” starts being a significant percentage of deaths, although Parkinson’s is only one component of that I think.

Source for graph is: https://flowingdata.com/2016/01/05/causes-of-death/

This can be done by 'Controlling for age' in statistics. If your cohort gets older, you get more prevalence of old age diseases of course. But by isolating by sufficiently small age groups (assuming the age distribution is approximately constant, or flat, within a group[1]), we can tell if the rate per given age is increasing or not. In this case simple multivariate statistics to judge if the changes are significant.

[1] The variation in distribution among age groups can be controlled by more sophisticated methods, but it may be sufficient to make the groups small and multivariate analysis (although results might be weakened by assumptions of independent errors if groups are too small).

A six-fold increase in the risk in individuals exposed in the workplace to trichloroethylene is more like a natural experiment than "simple correlation".

It’s not the only thing they were exposed to though in the natural experiment, so it’s entirely possible that third factor C is what’s driving it.

There are more studies according to the article that make the solid case, but one instance of correlation is not necessarily a smoking gun.

> > in the US, the number of people with Parkinson’s has increased 35% the last 10 years

> 10 years ago, the oldest U.S. baby boomers were reaching 65. Now, they are reaching 75[1].

The numbers do match up rather well. The US population over the age of 65 has grown around 33% in the last 10 years.

I see conflicting information regarding the average/median age at diagnosis, but it seems to be around there.

https://fred.stlouisfed.org/series/POPTOTUSA647NWDB

https://fred.stlouisfed.org/series/SPPOP65UPTOZSUSA

> population over the age of 65 has grown around 33% in the last 10 years

Which strikingly echoes GP's "birth rate went from 19/1000 to 27/1000 between 1935 and 1946".

But 10 years too late ? I'm confused maybe.

The data was intended to back up the GP's point, pointing out the growth in the underlying population of those diagnosed very closely mirrors the growth in number diagnosed.

I know. I meant the echoing wavefront seems 10y late : 1935+65 = 2000

> I know. I meant the echoing wavefront seems 10y late : 1935+65 = 2000

Good point. I believe I was thinking about 75. 65 crept in because I was also going to mention that at the beginning of the US Social Security program (1935), the assumption was no one lived much beyond 65.

Here is a table that might cast light on the diagnosis of Parkinson's by age: https://academic.oup.com/view-large/1251178

Note population pyramids for 2000[1], 2010[2], and 2020[3].

[1]: https://www.populationpyramid.net/united-states-of-america/2... [2]: https://www.populationpyramid.net/united-states-of-america/2... [3]: https://www.populationpyramid.net/united-states-of-america/2...

Thank you. Your population links are fascinating.

Going [1]->[2]->[3] shows that the real boom after all is the cohort born around 1960.

> real boom after all is the cohort born around 1960.

There is a boom in birth rates which remains sustained high for about 10 years. However, the conditions of early childhood environment keep improving along with a reduction the hazard of early death. The 1945 cohort does end up being hit by the Vietnam war whereas people born in the 60s do not face any of that.

Population numbers reflect who survived.