Researchers have found that 54 percent of older American Indians have cognitive impairment, including 10 percent 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, led in part by the University of Washington’s School of Medicine, 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, which NIH reported in May, were published in Alzheimer’s & Dementia, the Journal of the Alzheimer’s Association.

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 to 95 had some form of impairment. Of those, 35 percent  had mild cognitive impairment (MCI), 10 percent had dementia, and and 8 percent had a different form of cognitive impairment that was not due to MCI or dementia. There were 181 participants who showed no signs of cognitive impairment.

Based on previous studies, researchers estimated MCI levels at 12 percent to 21 percent of non-Hispanic whites, 22 percent to 25 percent of Black Americans, and 20 percent to 28 percent of Hispanics/Latinos.

NIH is a medical research agency and part of the U.S. Department of Health and Human Services.