High Prevalence of Cognitive Impairment, Dementia Among Native Americans

Over half of Native Americans aged 65 years and older experience cognitive impairment, and 10% of older Native Americans have dementia, according to study results published in Alzheimer’s Dementia. Vascular brain injury (VBI) is a leading cause of this neurodegeneration, highlighting the urgent need for strategies to mitigate cardiovascular and VBI risks in this population.

Previous research has demonstrated significant disparities in the mental health of Native Americans. However, relatively little is known about the epidemiology and prevalence of neurodegenerative diseases among Native Americans – despite the higher burden of risk factors and comorbidities documented in this population. To address this knowledge gap, investigators conducted the first population-based study to estimate the prevalence of vascular and Alzheimer dementias among Native Americans.

The investigators used 30-year longitudinal data from the Strong Heart Study (SHS) and the ancillary Cerebrovascular Disease and Consequences in Native Americans (CDCAI) study to determine the prevalence of cognitive impairment and its underlying causes among Native Americans aged 65 years and older. Participants completed a wide battery of neurocognitive and functional assessments and underwent structural magnetic resonance imaging (MRI) and clinical examinations over 2 visits, approximately 7 years apart. An expert panel reviewed the results of these measures for a consensus-based adjudication of cognitive status and probable underlying etiology. The participants also self-reported their medical history, age, sex, years of formal education, smoking status, and recent alcohol use. The primary outcome of interest was cognitive status.

A total of 397 Native Americans aged 65 to 95 years from the Northern Plains, Southern Plains, and Southwest of the United States were included for analysis. Participants were primarily women (70%), had a mean (SD) age of 78.0 (4.7), and completed 13.0 (2.5) years of formal education.

The investigators found that 54.4% of Native Americans aged 65 and older were adjudicated with cognitive impairment. By cognitive impairment type, 35.3% had mild cognitive impairment (MCI), 10.3% qualified for dementia, and 8.8% displayed impaired cognition not MCI (IN-MCI). For MCI, the primary consensus etiology was VBI in 51% of cases and Alzheimer Disease (AD) in 41%. Similarly, the primary etiologies for dementia were VBI (44%) and AD (44%).

The investigators observed that the number of years of formal education was highest among the cognitively intact group (mean=13.6 years) and lowest among those with dementia (mean=12.0 years; P <.001). Additionally, men were more likely to have MCI (32%) and dementia (33%), than to be cognitively intact (24%).

“These are the first formally defined, population-based epidemiologic estimates of [neurodegeneration] for this population, providing novel information for clinicians and researchers interested in AD and related dementias, especially in the context of racial-ethnic health disparities,” the investigators concluded. However, the authors noted, “Mean scores for common dementia screening instruments – even among those adjudicated as unimpaired – were relatively low compared to other populations… suggesting the need for cultural and environmental adaptation of common screening and evaluation instruments.”

Study limitations include 1) the potential underestimation of individuals with severe cognitive impairment due to selective survival bias and incomplete data and 2) the reliance on self-reported daily living activities.

This article originally appeared on Psychiatry Advisor