I think it is relevant because dementia is "a decline in thinking skills, also known as cognitive abilities, severe enough to impair daily life and independent function."[0]

If a decrease in cognitive abilities leads to impaired independence (and consequently life outcomes), then it would make sense that an increase in cognitive abilities leads to improved life outcomes. Here, I am assuming that this effect is monotonic across the whole range of cognitive abilities, which the submitted article seems to confirm.

Of course, I am comparing individuals having a medical condition (dementia) with, as far as I understand, cognitively intact study participants, but I think it doesn't meaningfully weaken my argument. If you disagree, I'd love to understand why.

0. https://www.alz.org/alzheimers-dementia/what-is-dementia

> Of course, I am comparing individuals having a medical condition (dementia) with, as far as I understand, cognitively intact study participants, but I think it doesn't meaningfully weaken my argument.

This is exactly why.

Because dementia has specific non-global effects on cognitive ability. It's a disease. The impairments caused by dementia aren't a linear projection down from a non-diseased state. Even if outcomes in terms of how the study defined them end up in a similar place, dementia isn't actually supporting evidence in any meaningful way.

Because it represents significant cognitive decline, which is a good comparison against those with significant cognitive advantage.

I don't think the greatest genius has anywhere near the cognitive advantage over an average person that an average person has over a dementia patient.