Thank you for the question.
Usually at the onset of the disease, after diagnosis, people are asked to write down their choices. They usually do this in front of a notary and in the presence of family members. They must then designate the individuals responsible for them, a proxy or a trusted person. In some cases, they must give specific instructions on the disposal of assets. They must also record their personal care preferences in anticipation of when it will be needed.
We're talking here about stage 3 out of 7, in the case of Alzheimer's disease. Stage 3 is mild cognitive impairment. However, new biological tests now enable us to diagnose the cause of these mild disorders.
The next stage is mild dementia, which usually occurs at stage 4 out of 7. At this stage, people still drive their cars, but in familiar places. They need help managing their taxes or their more complex finances, but they're still independent.
There's no real debate about whether these people are competent at these two stages, meaning stages 3 and 4 out of 7.