One potential solution is ahead-of-time decision making.<p>When young and lucid, make the decision of what criteria would cause you to prefer physician-assisted suicide. Write that down in a document. Allow that document to have legal force.<p>In the US, we already have the notion of Advanced Health Care Directives, which allow for things like power of attorney, nominating a proxy decision-maker, and criteria were a caretaker is allowed, or even required, to stop providing life-extending treatment. Health care providers generally follow these directives if made aware of them.<p>Thinking about this sort of thing ahead of time is not something that people want to do. But, for people who do complete one (with sufficiently-rigorous criteria), it solves some of the ethical issues around consent and incapacity.<p>By the way, I strongly recommend more people complete an AHCD. I had to care for a close relative at the end of her life, and the fact that her wishes were written down on paper was an incomparable gift to me. This should really become more routine.