Another thought on this.

I think, in this day and age, age is largely a meaningless concept, because, as others mentioned, there are so many instances when young people get sick and die or become disabled.

I am not saying it's totally irrelevant. Generally speaking, of course, a person in their older age feels different from how they felt 20-30 years ago and a general loss of vitality that comes along with various health problems is a real thing that is age related.

But, people are so diverse and there are so many factors that play role in how healthy and functional a person can be. My husband and I had a mutual friend who died of leukemia when he was 32. We knew some people of our age, who died of various diseases. At the same time, I see people in their 70-s in my neighborhood who jog every morning, some of them even run, which is something I cannot do, even though I am about 20 years younger. I barely force myself to take a walk every day. I've seen many people who can be officially called "old", not just "older" and who had so much vitality that I've never had in my life, not even in my young years. The amount of work they could do in an hour would be something I'd do in a week or in a day, on a very good day.

Age, in and of itself, doesn't determine how healthy, functional, energetic and mentally alert a person will be. It's a combination of so many factors and variables which determines that, which, as I said, make the concept of age largely meaningless.