Just How Common Is Alzheimer’s Disease?

November 16, 2022

One in 10 Americans over 65 has Alzheimer’s disease or other forms of dementia, according to a new report. Another 22 percent of older Americans have mild cognitive impairment, a memory-impairing brain disorder that can progress to full-blown Alzheimer’s disease.

The findings show just how common problems with memory and thinking skills become with advancing age. And the older you get, the more likely you are to have serious deficits: While 3 percent of people between the ages of 65 and 69 have dementia, the study found, that number rose to 35 percent among people 90 and over. Alzheimer’s disease is the most common cause of dementia, accounting for some 60 percent to 80 percent of all dementia cases, the authors note.

“With increasing longevity and the aging of the Baby Boom generation, cognitive impairment is projected to increase significantly over the next few decades, affecting individuals, families and programs that provide care and services for people with dementia,” said study author Jennifer Manly, a professor of neuropsychology in neurology at Columbia University. The results were published in JAMA Neurology, from the American Medical Association.

The study looked at a broad cross-section of 3,496 men and women 65 and older who were living in the United States. Their average age was 76, and 60 percent were female. Participants were part of the ongoing Health and Retirement Study, an ongoing research project from the National Institute on Aging and Social Security Administration that includes information on age, race, ethnicity, education and gender.

“This study is representative of the population of older adults and includes groups that have been historically excluded from dementia research,” Dr. Manly said. Participants filled out detailed questionnaires and underwent extensive neuropsychological testing. Family members and caregivers were also consulted to further assess cognitive status.

The researchers identified racial disparities in the prevalence of dementia and mild cognitive impairment, or MCI. The rate of dementia was highest among Black adults, affecting some 15 percent of those who self-identified as Black (and not Hispanic), compared to 9 percent of older whites and 10 percent of older Hispanics. The rate of mild cognitive impairment was highest among Hispanic seniors, at 28 percent, compared to 21 percent of older whites and 22 percent of older Black adults.

There were also notable differences based on educational attainment. About 9 percent of older Americans with a college degree had Alzheimer’s disease or another form of dementia, compared to 13 percent of those who had not completed high school. Interestingly, in this study, men and women had similar rates of dementia and mild cognitive impairment in different age groups.

“Because age is the most potent risk factor for dementia and MCI, the number of adults with these conditions is projected to rise dramatically in the United States and around the world due to demographic trends that have transformed populations from mostly young adults to mostly older adults,” the authors write.

They continue: “The economic impact of dementia, including the large burden of unpaid family caregiving, has been estimated at $257 billion per year in the United States and $800 billion worldwide.” Unless more effective treatments are found, those numbers will only continue to grow in the coming years.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University. 

Source: Jennifer J. Manly; Richard N. Jones; Kenneth M. Langa; et al: “Estimating the Prevalence of Dementia and Mild Cognitive Impairment in the US: The 2016 Health and Retirement Study Harmonized Cognitive Assessment Protocol Project.” JAMA Neurology, October 24, 2022


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