Both my grandmothers. It's brutal - from what we can tell in retrospect both of them were probably very aware of it, possibly for 2-3 years, but terrified of admitting to it.

One had a breakdown when her husband was going into hospital for a minor operation and she was terrified she wouldn't be able to take care of herself. The other had to be tricked to come in for an evaluation because she was scared of being left at the hospital.

Both lived for years after they stopped recognising anyone or reacting to stimuli, and the worst part to me was that both my grandfathers ended up spending years putting their own last years on hold to care for someone who no longer showed any signs of remembering who they were.

For all intents and purposes they were gone, but because they were still physically alive, it locked people in this waiting pattern. One of my grandfathers pretty much spent all his waking hours sitting next to his wife in a nursing home from he turned 80 until ca. 90. When she finally died, he was able to do other things again, but then died two years later of heart failure (he'd had heart problems since his 50s)

My grandmother had it too. In my aunt's words, after she passed: "It's like losing my mother twice - first the person dies, then the body"