Characterization of dementia and Alzheimer's disease in an older population: updated incidence and life expectancy with and without dementia.

Abstract

We estimated dementia incidence rates, life expectancies with and without dementia, and percentage of total life expectancy without dementia. We studied 3605 members of Group Health (Seattle, WA) aged 65 years or older who did not have dementia at enrollment to the Adult Changes in Thought study between 1994 and 2008. We estimated incidence rates of Alzheimer's disease and dementia, as well as life expectancies with and without dementia, defined as the average number of years one is expected to live with and without dementia, and percentage of total life expectancy without dementia. Dementia incidence increased through ages 85 to 89 years (74.2 cases per 1000 person-years) and 90 years or older (105 cases per 1000 person-years). Life expectancy without dementia and percentage of total life expectancy without dementia decreased with age. Life expectancy with dementia was longer in women and people with at least a college degree. Percentage of total life expectancy without dementia was greater in younger age groups, men, and those with more education. Efforts to delay onset of dementia, if successful, would likely benefit older adults of all ages.