Jigsaw puzzle, of a senior woman, falling apart
(Credit: Andrew Bret Wallis / Getty Images)

The first nationally representative study of cognitive impairment and dementia in more than 20 years found that almost one in 10 US older adults has dementia, and 22% have mild cognitive impairment. 

Adults with dementia or mild cognitive impairment are more likely to be older, have lower levels of education, and be Black or Hispanic, according to study findings by researchers from Columbia University. 

The data not only show the burden of dementia today but also will be an invaluable tool to track trends in the future, said study co-author Kenneth Langa, MD, PhD, from the University of Michigan Medical School. Most immediately, findings will help inform senior care today and in the near future.

“Following those trends will be especially important given the likely impact of COVID and other recent population health changes on the risk for dementia in the coming decades,” Langa said in a statement.

How they did it

Investigators tracked 3,500 older adults in the Harmonized Cognitive Assessment Protocol Project, part of the Health and Retirement Study. The HRS is an ongoing international research collaboration funded by the National Institute on Aging to measure, understand and compare dementia risk within studies of aging around the world. HCAP measures a range of key cognitive domains affected by aging, including attention, memory, executive function, language and visuospatial function. 

The study found that rates of dementia and mild cognitive impairment increased sharply with age — 3% of adults aged 65 to 69 had dementia, whereas 35% of those aged 90 or more years had a dementia diagnosis.

“Such data are critical for understanding the causes, costs and consequences of dementia and mild cognitive impairment in the US, and for informing policies aimed at reducing their impact on patients, families and public programs,” lead author Jennifer J. Manly, PhD, a professor of neuropsychology in neurology at Columbia University, said in a statement. “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 service for people with dementia.”

New dimensions examined

Unlike previous US dementia studies, this study also examined differences in the national prevalence of dementia and mild cognitive impairment by age, race and ethnicity, gender and education.

Researchers found a disproportionate burden of dementia among older Black adults, whereas Hispanic older adults had higher rates of mild cognitive impairment. Older adults with lower education levels had higher levels of both dementia and mild cognitive impairment compared with their higher educated counterparts. 

“This study is representative of the population of older adults and includes groups that have been historically excluded from dementia research but are at higher risk of developing cognitive impairment because of structural racism and income inequality,” Manly said. “If we’re interested in increasing brain health equity in later life, we need to know where we stand now and where to direct our resources.”

The study was published Monday in the journal JAMA Neurology.