In Colorado we voted in a law the allows for physician-assisted suicide in the event of bad health scenarios with no hope of a good life.
I’m not sure if your situation would apply, but there may be some way of declaring Alzheimers to be in that category for you, in a way that would provide the consent for the euthanasia.
But if you with alzheimers is there claiming you don’t want to die, it’s hard to imagine a doctor assisting in your death under those circumstances.
If you wanted to address this problem directly you might be able to rig up some kind of neurotoxin that kills you unless you enter a code whose value is determined by applying an algorithm based on the date. It would be a “forgetful man’s switch” instead of a dead man’s switch. Basically your intact memory would be necessary for your life to continue.
But that would require you to commit to correctly running that algorithm in your head each day and entering the code without error in order to stay alive.