Prevalence of Dementia Increases Dramatically After Age 90, Study Finds
By Jennifer Warner
WebMD Health News
Reviewed by Laura J. Martin, MD
May 9, 2011 -- More than four in 10 women over age 85 have some type of cognitive impairment, according to a new study.
The results show nearly 18% of women over 85 have dementia and 23% more have mild cognitive impairment, and the prevalence of dementia doubles after age 90 compared to women who are 85 to 89 years old.
"People 85 years or older are often referred to as the oldest old," researcher Kristine Yaffe, MD, of the University of California at San Francisco, and colleagues write in the Archives of Neurology. "This group is the fastest-growing segment of the U.S. population and is expected to increase in number by 40% during the next decade alone."
Dementia in the Oldest Old
In the study, researchers screened 1,299 women aged 85 or older for cognitive impairment. The results show that 41% of the women had dementia or mild cognitive impairment and the risk increased dramatically with age.
But the distribution of different types of dementia, such as Alzheimer's disease, vascular dementia, and others, was similar across all age groups, with Alzheimer's disease and mixed dementia each accounting for about 40% of dementia cases.
Compared with women with normal cognitive function, women with dementia or cognitive impairment were more likely to be older, live in a nursing home, have a history of depression or stroke, and were less likely to have completed high school.
Researchers say that by 1994 the oldest old already represented nearly 40% of people with dementia, despite accounting for just over 1% of the population.