Why does it seem like so many of our grandparents lived longer and better than our moms and dads?

The title… I recently lost my mom to Parkinson’s and dementia after an excruciating, long battle. By the end, I was her caregiver, and she was on hospice in my home for 2 months. Hardest thing I’ve ever done. My dad is 80 and also going downhill. I see so many people here with similar situations — parents in their 60’s and 70’s who are falling apart. And yet — three of my four grandparents lived into their late 80’s or 90’s. And again I see echoes of this in many posts here.

What is going on with this generation? I admit there is some selection bias here but I don’t think that explains all of it. My grandma was still alive when my mom was in her 60’s. I’m 40 and Mom is gone. I’ll be lucky if I get another 5 years with my dad.

Anyone else notice this? Feel similar? Gosh it’s painful. And I hope to end up like my grandparents — NOT my mom and dad. So it’s scary, too.