A person with dementia usually lives, on average, about 4 1/2 years after the onset of the condition, according to the Fisher Center for Alzheimer's Research Foundation. Of those with dementia, women tend to live longer than men.
These figures come from a large study done in the United Kingdom over 14 years, where University of Cambridge researchers tracked the progress of over 13,000 people.
Younger people with the condition were found to live longer than the elderly, the rule of thumb being half the life expectancy of an unaffected person of the same age. Cognitive decline does not appear to greatly influence life expectancy after the onset of the condition. Those living at home had a slightly higher life expectancy when compared to those living in nursing homes.