>Not because the incidence of disease is lower, but because it’s harder to diagnose. While it's seems true that "High IQ can mask early Alzheimer’s symptoms"[1

>Not because the incidence of disease is lower, but because it’s harder to diagnose. While it's seems true that "High IQ can mask early Alzheimer’s symptoms"[1] I would be surprised if that could explain such a large decline in incidence as they mention in that report that while it did mask the early symptoms, that just made the decline appear more sudden. The cognitive decline is really incredible, I saw it happen to my grandmother and she went from being a perfectly normal person to not recognising family members and becoming increasingly confused and aggressive all within a few years. So I think even more educated/intelligent people would eventually be diagnosed (perhaps a few months later) and thus any effect on the incidence would be small (due perhaps to these people dying prior to diagnosis). Furthermore, the Flynn effect is quite small, no - around 14 IQ points over more than half a century and now some talk of a decline, the "reversed Flynn effect" so it's not even clear how substantial an IQ difference we could expect. If the decline is due to "improvements in childhood nutrition, healthcare, and education" then I think that's quite good though, as those are things we can control. [1] https://www.heraldnet.com/news/high-iq-can-mask-early-alzheimers-symptoms/ https://www.heraldnet.com/news/high-iq-can-mask-early-alzhei...