I have never understood how the professionals dealing with Dementia patients who are so confused , can still maintain that those patients can make their own, responsible decisions. We had a Dr. who was still taking my DH's evaluation of his meds and how he was doing, and ignoring my (Caregiver) observations. When he began demanding a whole battery of tests--most repeats because it'd been a year, and some for things we wouldn't be able to treat if findings indicated it, I drew the line. Seems to me, if the person who's ill can't be llowed to drive, can't be trusted with their meds and other basics, they aren't capable of making resposible decisions at all.
Like leaving a toddler in a room with meds, knives, and cleaning supplies, with the door to the outside wide open, and expecting nothing bad will happen.