The AARP Staying Sharp is a program devoted to helping the elderly stay at the top of their ability both physically and mentally. The following link takes you to a section that deals with that. It should be helpful of all.
https://stayingsharp.aarp.org/
In addition, the AARP provides people with access to a set of comprehensive tests that will evaluate how a person is doing mentally. Depending on the number of tests that a person takes, they can be completed in 30 to less than 60 minutes. People can take them every 30 days, as some may need a bit of adjustment the first time. I have taken the full set, and consider them to be an excellent evaluation as to how one uses their mind/brain. NOTE: They are required to be taken on a computer. In addition, your score will be lowered if you have uncorrected visual problems.