Every once in a while someone does a "study" like this. Mainly, I think because their professional career is enhanced by publishing. Most of them, including this one, aren't very applicable to the real world. Yes indeed a positive attitude makes a difference. It is a lot easier to have a positive attitude if you have the right genes. As has been pointed out there is often a significant difference between Life and Healthy Life. At its' extreme there is a saying in EMS that with drugs and electricity a rock can be made to have a heartbeat and be "alive". A bit overstated but makes the point.

We all know people who are in those facilities that, by any name, are functionally warehouses for the dying. The contents of these facilities often seem happy. That is a testimony to the ability of the human mind to adapt and make the best of a situation. In many ways no different than the Black Humor of people in jobs where they have to deal with gross things.

Personally, I have always had a saying that is appropriate here: "Don't build a box around yourself and you won't have to learn to think outside it". In many ways people who "think young" are not thinking young as much as they are thinking outside the society imposed box.