Older American Indians may experience higher levels of cognitive impairment than previously thought

NIH-funded research exposes additional health disparities for American Indians.

Researchers have found that 54% of older American Indians have cognitive impairment, including 10% with dementia, highlighting a significant disparity with the rates of cognitive impairment and dementia in the general American population. The National Institutes of Health (NIH)-funded study also identified vascular injury, which can result from untreated hypertension and diabetes, and Alzheimer’s disease as equally responsible contributors to dementia in American Indians, with substantial overlaps between the two. The findings were published in Alzheimer’s & Dementia, the Journal of the Alzheimer’s Association.

“These results underscore that cognitive impairment among elder American Indians is highly prevalent, more than previously thought,” said Amy S. Kelley, M.D., 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.”

Previous studies that relied on medical records estimated that cognitive impairment and dementia levels in American Indians were similar to non-Hispanic whites. However, for this new study, the researchers used survey and screening techniques with individual assessments that did not rely on previous access to the medical care system. They found that 216 American Indian participants aged 72-95 had some form of impairment. Of those, 140, or 35.3%, of them had mild cognitive impairment (MCI), 41 (10.3%) had dementia, and 35 (8.8%) had a different form of cognitive impairment that was not due to MCI or dementia. There were 181 (45.6%) participants who showed no signs of cognitive impairment.

These results suggest the levels of MCI and dementia in American Indians who are 72-95 years of age are higher than those in other groups. Based on previous studies, researchers estimated MCI levels at 12% to 21% of non-Hispanic whites, 22% to 25% of Black Americans, and 20% to 28% of Hispanics/Latinos. Vascular brain injury measures were seen more often than Alzheimer’s markers in the MCI cases, suggesting that both Alzheimer’s disease and vascular brain injury may have been drivers of cognitive impairment for many of the participants.

“This research also suggests that vascular risk factors, such as hypertension and diabetes, are known to be modifiable and therefore could be prioritized to potentially reduce the risk of cognitive impairment among American Indians,” said Dallas Anderson, Ph.D., M.P.H., an NIA program director and neuroepidemiologist.

Led by a team of scientists at the Huntington Medical Research Institutes in Pasadena, California, and University of Washington School of Medicine, Seattle, the study harnessed the data of 397 participants in the NIH-funded Strong Heart Study. A population-based study of American Indian Tribes, the Strong Heart Study was conducted over 30 years and in three U.S. geographic regions — the Northern Plains, Southern Plains, and Southwest. An ancillary study included detailed cognitive testing, neurological examination, and brain imaging during two visits approximately seven years apart.

This research was supported in part by NIH grants R01HL093086, P50AG005136, and K01AG057821.

These activities relate to NIH’s Alzheimer’s and Related Dementias Research Implementation Milestone 1.D, “Develop state-of-the-art protocol for assessing dementia on large nationally representative samples that (a) includes racial/ethnic subsamples large enough to support disparities research and (b) is adaptable for use in comparable studies around the world” and Milestone 1.F, “Population Studies: Inclusion of non-AD cohorts.”

About the National Institute on Aging (NIA): NIA leads the U.S. federal government effort to conduct and support research on aging and the health and well-being of older people. Learn more about age-related cognitive change and neurodegenerative diseases via NIA’s Alzheimer’s and related Dementias Education and Referral (ADEAR) Center website. Visit the main NIA website for information about a range of aging topics, in English and Spanish, and stay connected.

About the National Institutes of Health (NIH):
NIH, the nation’s medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

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