1. we were talking about dementia, not "getting old". 81y life expectancy means if you look at the cohort of females born 81 years ago, about half of them will have already died, heart disease being the biggest cause. The relevant question is how many of them (both the dead and living ones) will have had bad enough dementia to have needed to be in a care home for it specifically? I don't mean for mild forgetfulness, occasional senior moments, etc.

2. 81y (actually 80y per 2021 table, https://www.ssa.gov/oact/STATS/table4c6.html ) is the life expectancy at birth. For a 80yo US female, life expectancy from the same table is 9.38y. So the ones who are still alive at 80 still have some "gas in the tank". My mom is up there in age and she needs a lot of assistance getting around etc, but it's mostly physical issues.

She is in a "adult community" (i.e. apt. complex for old folks) and I spend a lot of time there seeing her. I see tons of over-80's there. A few really do have serious dementia, but most are at other levels of independence with many rolling around in wheelchairs while still mentally present. Dementia care is a different thing and it's not that common for someone who is "only" 81 to need it.

My mom at 81 was still mentally quite sharp. She's slowed down since then but it's mostly mobility and sleeping a lot. President Biden seems to have some dementia issues but again, they aren't severe enough that he needs to be in a care home for it.

3. It now sounds like Kay Granger is/was in a care home but at least according to the spin, it wasn't specifically for dementia, so who knows.

See also: https://en.wikipedia.org/wiki/Dementia_caregiving

I'm sad to hear that. Yes it happens but it's not really common from what I can tell. Currently theory about Alzheimer's is that it is also caused by sustaining viral infections earlier in life.