Ken Ono comes to mind, although he was slightly younger.

I’m not aware of any specific research but I have heard many mathematicians profess that they lost some of their sharpness by their mid-late thirties. At the same time, more experienced mathematicians have developed a wider range of schema from which they dream up new ideas. My doctoral supervisor was in his fifties and was sharp enough for me!

Lastly, it is never too late to discover one’s mathematical talents for the first time.