What do you know about it?
What is the best test for it? Ie distinguishing normal decine from dementia.
Looking for a test that can be taken twice some 6 months apart to show cognitive changes over a time period.
Background reading
The following article says that nobody knows what mental decline with age is. Because lateral studies are flawed due to differing education standards over time and because longitudinal studies are flawed due to the practice effect and due to rejecting participants who die before age 80.
Lateral studies show peak cognitive performance near age 25 and longitudinal studies give peak cognitive performance near age 60. Both types of studies separate cognitive performance into many different facets.
https://medium.com/psyc-406-2015/how-fast-does-iq-decline-can-you-do-anything-about-it-f5ca370d8b62