The following is from my real life observations:

There is longevity in my family. Many have lived past one hundred or have gotten close within a couple of years. My great-grandfather was one hundred and six and both of my grandmothers were ninety nine when they passed - all living unassisted and on their own. My grandmother's sister passed at one hundred and three. None of my family suffered with mental decline, that is, until my mother's generation. What changed?

I have 3 aunts on my mother's side, all in their late eighties and early nineties. One died from Alzheimer's last year. She had a heart attack in her fifties and was put on a statin and blood pressure medication. In her mind, eating any kind of fat was akin to signing her death warrant. She barely ate anything and was obsessed with the scale. She literally starved herself to death besides taking a statin. She had all the hallmarks of having an eating disorder. As her condition declined, even more meds were prescribed. My other two aunts also suffer with cognitive decline - both have been taking statins for years along with other meds that have increased over time. Sadly, we have had to witness this decline. "But the doctor said this statin was good for me. You don't know what you are talking about and you are full of crap!"

Of my six uncles, only one is still living at ninety three. He takes no statins and his brain is fully functional. The other five, all suffered from mental decline in their last years. All were polypharma, starting with the statins. They only lived to their eighties. Who knows if they would have lived longer if not for their mental decline.

My mother will turn ninety early next year. She is as sharp as a tack and very active. I know this for a fact because she lives with me. I wish I had her energy. A few years ago she was still playing soccer with her great-grandchildren in the back yard. Not bad for an old lady. She refuses to take statins even though her doctors have tried pushing them on her for years. I educated her on statins at least thirty years ago. The only med she takes is for thyroid. I fully expect her to reach the century mark and beyond. I pray I follow in her footsteps.

The common denominators in my family with this generational change in mental decline seems to be polypharma, especially statins, and doctor recommended low fat "heart healthy" diets. Those that followed doctor's orders had their brains turn to mush, and those that didn't follow their doctor's advice are intact and very healthy for their age.