Excellent. Do you cite any references? I know they exist because I've done some reading on the topic.
I hate to say this, but take comfort in the fact that I have developed a few gray hairs myself... As people age and become less active for whatever reason, their brains physically shrink. Older, inactive people could benefit just from starting a walking routine. That will grow some neurons. However, use-it-or-lose-it still applies to the new neurons. So either the physical exercise needs to challenge your brain to form new connections, or you need to go and learn sudoku or something while your brain is primed for learning.
Here is some support for my claims: http://biomed.gerontologyjournals.or...act/61/11/1166
I love the fact that we can change our own biology.