Sample of one, but I went back to grad school at 45. Was living at home with wife and son, so was firmly grounded in the present. However being around energetic, enthusiastic, and optimistic fellow students in their early 20s was a real boost. Many factors at work - the program required a ton of energy and an openness to considering new ideas - something I had not experienced in corporate life in many years. Definitely did not reverse aging, but really lifted my energy and optimism considerably.