I'm in my early 40s, and do nothing specifically for my physical health. I don't have cognitive decline, I don't suffer from little issues at all, (someone once

I'm in my early 40s, and do nothing specifically for my physical health. I don't have cognitive decline, I don't suffer from little issues at all, (someone once said that'll happen once past 40), some days I skip sleep entirely. I also learn new stuff and program on projects, which are cognitively demanding, almost every single day. I don't regularly watch TV shows. On occasion I binge-watch something, only to stop it again for many months. I don't drink alcohol at all, but I consume small amounts of THC. Your "mid 30s" claim might be true for people who are doing it wrong, which probably/likely is the vast majority, but there's absolutely no fair and objective way of putting an age on the beginning of cognitive or physical decline as if it was outside of ones personality responsibility/abilities to prevent it from happening until a much, much later age. But ... to be the exception that agrees with the rule: If I lived how most people around seem to be living, I'd likely suffer from decline as well.