I had a cousin with Pick's disease, which is a rare form of early-onset dementia which has similar symptoms to Alzheimer's.

(See https://www.dementia.org/picks-disease-and-dementia )

His sister (my other cousin) devoted a decade of her life taking care of him. (Neither cousin had married). Extremely sad and the effects traumatized the entire family. It is unimaginably sad to see a younger person succumb to dementia.

At no time did anyone even think of assisted suicide. I can't imagine how this can be done fairly unless someone is of sound mind.