No, we don’t. My four grandparents’ bodies deteriorated with advanced age, but their minds were as sharp as ever. Hopefully, those good genes will stand me in good stead over the decades.
You are blessed.
My paternal grandfather was as sarcastic as ever until the day he went into a final coma. My maternal great-grandmothers both went dotty but lived to a hundred — oddly enough, they slipped back into lucidity on their deathbeds. Maybe they were both playing a 15 year joke.