Advance Directives

Every person should have an assigned, trusted individual(s) as a Health Care Proxy (HCP) and Power of Attorney (POA), they act as your agents when you can no longer do so.

Advanced Directive for Medical Care
Two-thirds of Americans have not established instructions for family and medical professionals to follow in the event they become physically or mentally incapacitated. As a results family members are left confused and with the responsibility of trying to figure out what a person "would have wanted" at the end of their life. This is a terrible thing to do to your children or loved ones. Every person should have a standard advance directive which designates who will make decisions (HCP) if the person becomes incapacitated, and often offers some details about a person's wishes regarding using/avoiding heroic life sustaining methods, feeding tubes, ventilators, etc. when death is imminent. While standard directives often address vegetative comas, they are often not helpful in the case of a person who is awake but severely confused with a terminal disease which progresses slowly over years.

Here's a helpful explanatory website with videos that can help you prepare, in advance, a written summary of your wishes should you become ill:
PREPARE™ For Your Care.

Dementia-specific Advance Directive
All types of dementia are the sixth leading cause of death in the US. This rises to the fifth place for those over 65 and to the third for those of 85 as this useful article in the NYT states: Alzheimer’s? Your Paperwork May Not Be in Order - The New York Times.

The biggest issue encountered in whether to prolong or end life is feeding. Dementia patients do not require feeding tubes, as they retain the primitive reflex of opening the mouth when touched by a utensil, like a spoon. However, in late-stage dementia the ability to swallow is lost and attempts at feeding can lead to choking and aspiration causing great discomfort.
The organization End of Life Choices New York says: "There are two purposes to completing an Advance Directive for Receiving Oral Food and Fluids In Dementia. The first is to document your wishes about when to stop efforts to provide assisted oral feeding because of an advanced dementia. The second is to ensure that your appointed health care agent is empowered to honor and implement those choices if you suffer from advanced dementia." Their document can be completed by a dementia patient before they lose capacity to make such decisions– Advance Directive for Receiving Oral Food and Fluids in Dementia.