This terrific article from the Wall Street Journal in the fall of 2021 notes:
“As the number of people with dementia grows, more of them are speaking out to challenge assumptions about what they can and can’t do. A group of advocates, many in the earlier stages of this condition, say that people around them often struggle with understanding the full range of symptoms. … Life expectancy for those with early-onset dementia varies. One 2019 study showed a mean survival time of 17 years after symptoms start and 10 years after a diagnosis.”