I used to work at Miracle-Ear hearing aid center, so my view on age changed after working there and seeing different age ranges all the way up to 105! So, I honestly think middle aged is in your 60s, because many of those 60s-90s people were healthy, active and still doing things you wouldn't expect! Once you hit 60, you could still live for 40 more years! Wow, I'm only 35 and sometimes feel old, but if you think about that, 35 seems like a baby still!
Years of watching the elderly and young!