I started residency at 34 and started my first attending job at 40. I wouldn't consider myself "older" but I was definitely older than most of my residency classmates. I honestly think I had it a little easier than some of them though because I'd had real jobs before so the responsibility and expectations, while dramatically different than previous jobs, weren't something I was unfamiliar with.
I've been in practice for a little over 3 years now. One thing that I think being "older" has helped me with is that several of my colleagues have told me, as early as halfway through my first year of practice, that I don't seem like a "fresh grad" in terms of my practice patterns.