I think middle age starts soon or varies after 40. If you've ever seen the movie "10", they mention it as "patchwork". Scars don't go away, wrinkles start forming and persist, eye vision focus changes, hair thinning or loss, more white hairs, extra hair starts growing in undesirable places, back aches more, etc.
Ironically, even with all the glut of fad "health" and alternative products out there , it's been reported recently that average lifespan hasn't improved or gotten worse for everyone. So it could be while maybe people can look younger longer, true aging hasn't really been slowed and life threatening diseases and conditions, cancer, Alzheimer's etc. still has much to do with luck in surviving.