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March 17, 2008 -- A new study shows about one in five Americans over age 70 has mild cognitive impairment without dementia, and a large portion of them may progress to dementia.
"These findings illustrate that nearly every family will be faced with the challenges of caring for a family member with some form of memory impairment," says researcher Brenda Plassman, PhD, associate research professor of psychiatry at Duke University, in a news release.
"Even among the people age 71-79, a sizeable number had cognitive impairment," says Plassman. "This is an age at which most people expect to have many productive years ahead."
Based on the results of this study, researchers estimate that 5.4 million adults (22.2%) age 71 or older have mild cognitive impairment that does not meet the level of dementia. This may include problems with memory, attention, language, judgment, or communication. But is not severe enough to affect their ability to complete daily activities and may not be noticeable.
That's in addition to the estimated 3.4 million Americans who have dementia, which is a more severe form of memory loss that affects the ability to function independently.
Researchers say that although dementia has been widely studied, it's unclear how many older people have milder forms of age-related memory loss or cognitive impairment. Previous studies in other countries have estimated that 3%-29% of the elderly are affected by cognitive impairment without dementia.
In the study, researchers examined 856 participants from the National Health and Retirement Study over a period of nearly five years.
The results, published in the Annals of Internal Medicine, show that 22% of the elderly participants had cognitive impairment that did not meet the criteria for dementia.
The study also shows that 12% of those with mild cognitive impairment progressed to dementia and 8% died annually.
Researchers estimate that nearly a quarter of cases of mild cognitive impairment are tied to underlying chronic medical conditions, such as diabetes and heart failure. The researchers write that their findings "suggest that the number of individuals with cognitive impairment without dementia in the United States is about 70% higher than that with dementia ..."
"As the population ages and works longer, understanding the extent of cognitive impairment in the older population is critically important," says Richard Suzman, PhD, director of the National Institute of Aging's Behavioral and Social Research Program, which funded the study.
"Research is now beginning to suggest that interventions -- such as controlling hypertension and diabetes or perhaps cognitive training -- might help maintain or improve mental abilities with age," says Suzman.