Smarter? Depends, but generally yes.
Before you scream, what what? hold your horses..
Smart and Intellect are not the same thing.
Intelligence is a given. We get that with birth.
Smartness is earned. It is the result of learning.
Now, to repeat the question.
Do people get smarter as they get older?
Generally yes, but that requires the person to put some efforts into it.
If you abandon brain work, if you abandon thinking (which some older people tend to do), then you surrender it.
And you might end up dumber than you were when you were still more active.