I went to a program this evening on end of life issues put on by our community interfaith organization. The two panelists were a hosptial chaplain and a professor of nursing who specializes in policy. I asked what happens when a person prepares a clear advance directive about medical treatment at the end of life before they develop dementia, but then as the dementia develops they might change their mind. Both speakers answered that if doctors certified that the person was not able to make decisions for themselves then their earlier directive should be followed.
But I don't think it is so simple. When we are adults at the height of independence we think that we would never want to live dependent and not in control of ourselves. But perhaps the spiritual lesson we might learn towards the end of life is that we don't have to be in control of everything to have a worthwhile life, to have value. I do think it better to die of something else first than to die of Alzheimer's, as my grandmother did. But I also don't think a statement in advance that "I would never want to live like that" is necessarily worth more than what the person is actually experiencing even if their awareness of the world around them has become limited.