What would the longest somebody can live with dementia be?

Can be quite awhile!: Always remember, an individual is not an average. Without dementia, a 65 year old averages 18.5 more yrs - with dementia, only 10.7 yrs and less if frail. In a study of all ages, average survival with alzheimer's or dementia was 4.5 yrs. But, with good care and an otherwise strong, healthy body - life with dementia can exceed averages by a lot yet it definitely shortens avg life expectancy.