I will answer very quickly.
In the past year in Quebec, 76% of patients who received medical assistance in dying had cancer. Cognitive and neurodegenerative diseases such as Alzheimer's are now the second leading reason why people seek medically assisted deaths.
Why should the bill include the diseases? The reason is that more and more people are going to contract them. As you know, after the age of 60, the older a person is, the more at risk they are. As people age, the more common cognitive and neurodegenerative diseases become.
When patients reach the later stages of disease, which, for Alzheimer's, generally coincides with stage four, they are no longer really capable of making their own decisions. Patients in stage four and beyond spend the last two or three years of their lives living without dignity—at least, in the estimation they held when they were capable.
In Quebec, a committee studied the issue of advance medical directives and released its report in late January. Except from a religious standpoint, a broad consensus exists over the ability to obtain medical assistance in dying through advance medical directives. It is up to the person to decide when they would receive medical assistance in dying. They might decide that it is when they no longer recognize their children, for instance. The person decides on their own beforehand, of course, in the presence of witnesses.
That is a very short answer to a complex question.