Weird article because it offhandedly mentions the term "healthy vaccinee effect[0]" but does not explain it. So while I was reading and wondering whether all these studies they mention were observational, they drop the term somewhere in the middle and then just continue their breathless listing of vaccines' inverse correlation to dementia.

The word interventional is not found anywhere in the article and it is hard for me to believe there are no interventional studies in this field.

> Multiple large observational studies have found that routine adult vaccines are associated with a reduced risk of dementia, with some showing risk reductions of 25% to 40%.

The observed difference is most likely caused by people with declining health being less likely to vaccinate. My assumption is that the article was compiled to show a conclusion that is not supported if one looks only a little bit further.

[0] https://www.science.org/content/blog-post/healthy-vaccinee-e...

This is interesting to me given that another factor seemingly correlated with dementia is the bacteria that causes gingivitis. The obvious speculation for a naive layman like myself is if dementia is simply driven by cumulative damage done to the brain by infections pathogens over the course of one’s life.