I saw that as falling under #3. There are treatments for dementia and Alzheimer's but they all suck and one can rationally prefer the risk of immediate death to losing it all. This comes up a lot linked with assisted-suicide, as does the attendant legal risks for oneself and the cryonics org (some of Mike Darwin's blog touches on the effects of aging, and I think Ettinger himself took the dehydration route a few years ago).