I did not say that over 60 indicates dementia. In fact my reference to dementia was more proximate to my reference to those who are driving at 15.
Advancing age is certainly a risk factor, although you can get a dementia younger than 60 too. I too have had a family member with severe dementia, one day I found that the rest home manager had half filled an electoral enrolment form for them.
Looking online:
Dementia doesn’t change your right to vote
https://alzheimers.org.nz/get-suppor...mentia/voting/