There are many dimensions to dementia, leading to different paths for different individuals.
I have known individuals whose dementia took years to degrade the mental faculties enough that the brain’s autonomous functions eventually failed the body. Mentally they failed early on but the body continued O.K. for many years. And I have known one individual whose dementia was not advanced at all for years, and then in 2-3 years took her life, with her regular body functions shutting down. Someday they may understand why the path of dementia is not the same for each individual affected by it, and when they understand that they may learn how to control it.
Pat Summitt, the UT basketball coach, lasted less than five years from diagnosis to death.