If anything I'm a much better programmer in my 40s than when I was younger. My cognitive capacity (being able juggle more balls at the same time) is about the same, probably a bit better now. My lateral thinking has definitely improved. And then of course I'm wiser because I have more experience and my instincts are just better.

What surprises me is I learn much faster now than I used to. But I guess it makes sense. I never stopped learning new things (coding or otherwise) so I've learned to learn. I also have more data points to compare new stuff to.