IQ is a protective factor for some (but not all) forms of dementia [1]. Could the Flynn effect, by raising IQs, reduce the risk of some forms of dementia?
Immigration is another factor that could be increasing IQs, which in turn may decrease the incidence of dementia. Many countries have immigration programs that give preference to skilled professionals, who are likely to have above average IQs. Another immigration route which favours above average IQ is education-based immigration – come for university, stay after graduation.
IIRC the Flynn effect has been in reverse since the mid 90's. Here's a quote from Wikipedia:
"Research suggests that there is an ongoing reversed Flynn effect, i.e. a decline in IQ scores, in Norway, Denmark, Australia, Britain, the Netherlands, Sweden, Finland, France and German-speaking countries, a development which appears to have started in the 1990s".
In my country, Australia, we saw zero improvement on the Colored Porgressive Matrices from 1975-2003, and a decline since then.
It'd be interesting to see if reversal of the Flynn effect is correlated with massive unskilled immigration (esp from third world countries), which has accelerated in many European countries.
If we examine countries with extremely strict immigration policies that favor the skilled (e.g. Singapore), will we see IQs going up?
The birth rate differences between high IQ and low IQ sections of the population have been suggested as the primary driver of this. The fact that it's been suggested at all is amazing due to the western world's strong avoidance of any topic that resembles an argument for eugenics.
Immigration is another factor that could be increasing IQs, which in turn may decrease the incidence of dementia. Many countries have immigration programs that give preference to skilled professionals, who are likely to have above average IQs. Another immigration route which favours above average IQ is education-based immigration – come for university, stay after graduation.
[1] https://www.research.ed.ac.uk/portal/files/14297193/McGurn_D...