My dad is still sharp as a whip! And he is 92 and mom is 90, they still live alone, (though my older sister lives on the same street), they still drive, go out to dinner, go to movies, doctor, shopping all on their own.
But my dad is starting to have a hard time getting up from his chair! He's starting to look rickety....
My mom is in great physical shape! Walks a mile every day! But her brain is not as sharp as she once was... She looks a good 20 years younger than she is!!! Even her doctor is amazed! I pray I have both her good genes and dad's good genes, when I get old!!! If my older sister is any indication of what I will be like, then I have a chance of keeping the brains and physical strength when old! Fingers crossed!
My point is, you can lose your physical strength when old, and still be sharp, mentally! It all depends on the person!