May 21, 2024

Cognitive impairment among older American Indians

At a Glance

  • Researchers found that more than half of American Indians about age 70 and older had some form of cognitive impairment, much higher than previous estimates.
  • The findings highlight the importance of addressing diabetes, high blood pressure, and other modifiable factors to reduce cognitive risks in this population.
Pensive older Native American man in the countryside. The study suggests higher rates of cognitive impairment among Native American people than previously thought. Light and Vision / Shutterstock

As the population of older adults in the U.S. continues to rise, a growing number are grappling with age-related health conditions. These include cognitive impairment, dementia, and cardiovascular disease. The risk of getting these disorders can vary depending on several factors. These include race, environmental stressors, and access to health care.

Studies have found that American Indian and Alaska Native people have a disproportionately high rate of cardiovascular disease. This may harm blood vessels and the brain, which in turn can lead to cognitive problems. Previous research suggested that the prevalence of cognitive impairment and dementia in American Indians is similar to that of non-Hispanic Whites. But these studies relied on data from electronic health records, which had limitations affecting accuracy. Medical records may undercount health disorders in groups that have low access to health care.

To take a closer look, a research team led by scientists at the Huntington Medical Research Institutes and the University of Washington drew on data from about 400 American Indians. Participants were from 11 American Indian tribes. Analysis of cognitive status relied on detailed surveys and individual medical assessments rather than on health records.

The data were gathered as part of a large-scale NIH-funded study of American Indians called the Strong Heart Study. The study was conducted over 30 years in three regions. An ancillary study on dementia and cognitive health included neurologic exams, extensive cognitive testing, and MRI scans. These exams occurred during two visits, about seven years apart. Initial cognitive tests were conducted between 2010 and 2013. Follow-up exams occurred between 2017 and 2019. The participants were 70 to 95 years old.

An expert panel reviewed the data to determine each participant’s cognitive status. They classified participants as healthy or affected by mild cognitive impairment (MCI), dementia, or some other cognitive problem. The panel also assessed likely causes of cognitive problems. Results were published on May 15, 2024, in Alzheimer’s & Dementia, the Journal of the Alzheimer’s Association.

Overall, the researchers found that 54% of participants had some type of cognitive impairment. Specifically, 35% (140) had MCI, 10% (41) had dementia, and 9% (35) had another type of cognitive impairment.

The estimate that 35% of older American Indians have MCI is higher than that seen for other U.S. groups. Previous studies found that MCI affects 12%-20% of non-Hispanic Whites; 22%-25% of Blacks; and 20%-28% of Hispanics/Latinos.

In assessing the likely causes of cognitive impairment, the researchers found that vascular brain injury was a primary culprit, affecting 44%-51% of those with MCI or dementia. Alzheimer’s disease was deemed about equally responsible. It was blamed for 41%-44% of such cases. The findings suggest that targeting modifiable risk factors, like hypertension and diabetes, could help to reduce the risk of cognitive impairment among American Indians.

“These results underscore that cognitive impairment among elder American Indians is highly prevalent, more than previously thought,” says Dr. Amy S. Kelley, deputy director of NIH’s National Institute on Aging (NIA). “Considering how these new prevalence figures for American Indians are much higher than other groups, as we continue to pursue prevention strategies and treatments, it is imperative that we address health disparities to help us find solutions that will work for all older adults.”

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References: Epidemiology and prevalence of dementia and Alzheimer's disease in American Indians: Data from the Strong Heart Study. Suchy-Dicey AM, Domoto-Reilly K, Nelson L, Jayadev S, Buchwald DS, Grabowski TJ, Rhoads K. Alzheimers Dement. 2024 May 15. doi: 10.1002/alz.13849. Online ahead of print. PMID: 38747387.

Funding: NIH’s National Institute on Aging (NIA) and National Heart, Lung, and Blood Institute (NHLBI).