Sounds like something someone < 40 would say. To anyone over, I feel like this study is pretty obvious. I'm in my early 40's and whatever change this is, has been discussed multiple times with my peers, active lifestyle or not, wealth or not, married or not, physical career or not. Everything starts to feel a little harder, whether it's exercise, problem solving, memory, sleep, sex drive, appetite, fuckin everything. Things change in your late 30s, for sure.
All young people think they are special and age is just a number. The rest of the population knows that isn't true. Spare me your weight lifting 80 year old, or "my grandpa worked the farm til he was 90" stuff, we all know those are extreme outliers.