Differences found among Black and white research study participants
Black participants in Alzheimer’s disease research studies were 35% less likely to be diagnosed with Alzheimer’s and related dementias than white participants, despite national statistics that indicate that Black Americans are overall about twice as likely to develop dementias than whites. The analysis of data on study participants from across NIA’s network of Alzheimer’s Disease Research Centers (ADRCs) also showed that Black participants with Alzheimer’s and related dementias had more risk factors for the disease, as well as greater cognitive impairment and symptom severity than white participants. Results of the study were published in the journal Alzheimer’s and Dementia.
Previous studies have shown that for the overall U.S. population, Black Americans are roughly 1.5 to 2 times as likely than whites to develop Alzheimer’s and related dementias. For the current study, investigators wanted to further explore if there were also related racial differences in cognition, neuropsychiatric symptoms, and functional abilities in diagnosed study participants. The researchers tracked 15 years of data (2005-2020) on 5,700 Black and 31,225 white participants using the Uniform Data Set of the National Alzheimer’s Coordinating Center (NACC), which aggregates data from ADRCs from across the country. At baseline visits, the data showed that 26.8% of Black participants were diagnosed with Alzheimer’s or related dementias, as opposed to 36.1% of white participants. The analysis also showed that Black participants had 35% lower odds of having an Alzheimer’s or dementia diagnosis at the initial visit relative to white participants.
Researchers found that Black study participants showed higher rates of cognitive impairment, particularly on measures of processing speed, executive function, and language, compared with white participants. Black participants also had higher rates of hypertension and diabetes, potential risk factors for Alzheimer’s and related dementias.
The research team found that neuropsychiatric symptoms were also more likely to occur in diagnosed Black participants than in white participants with a similar diagnosis. After accounting for demographic factors and education, Black participants were about twice as likely as white participants to experience delusions and hallucinations. Black participants were also more likely to have other symptoms, including agitation/aggression, loss of inhibition, irritability, motor disturbances, and abnormal sleep, behavioral, and appetite/eating changes. Black and white participants did not show significant differences in affective or anxiety symptoms, or apathy and indifference, other symptoms of Alzheimer’s and related dementias.
The investigators see their results as further evidence that Black patients often have to present with more severe clinical presentations to warrant a diagnosis of dementia from physicians than white patients. This is consistent with numerous studies that showed Black individuals were not being diagnosed with Alzheimer’s or related dementias or seeking treatment until the disease process was more advanced.
The scientists suspect these trends are partly tied to social attitudes and beliefs within the African American community. Many Black older adults tend to seek medical treatment when they encounter neuropsychiatric symptoms such as hallucinations, delusions, and personality changes, but delay help for memory problems, which are often viewed as a normal part of aging.
The investigators are not yet clear on the reasons behind these findings but suspect they can be explained in part by a referral bias or differences in diagnostic thresholds applied by providers. They see this study as further evidence for addressing racial disparities in Alzheimer’s disease and related dementias treatment, especially to avoid delayed diagnoses that could have major adverse consequences for patients and their families.
The researchers cautioned that the study was conducted with a clinic-based sample derived from ADRCs, and that their analysis may not generalize to the broader U.S. population. The scientists noted that because the study was a targeted comparison between Black and white research study participants, it also cannot be extended into any clear trends in overall Alzheimer’s and dementia prevalence rates for Latino or other underrepresented populations. The researchers hope to expand on this work to include data from other underrepresented groups. Given that ADRCs in certain parts of the country were more likely to enroll Black participants, the authors also hope to explore the impact of geographic location on dementia diagnosis.
The research team was led by the NIA Intramural Research Program in collaboration with colleagues from Adler University, Chicago; the Geisel School of Medicine at Dartmouth University, Hanover, New Hampshire; the University of Alabama at Birmingham School of Medicine; and the Rosalind Franklin University of Medicine and Science, Chicago. The research was funded by NIH grants K23 AG064122, U24 AG072122, and multiple grants supporting the NIA Alzheimer’s Disease Research Centers.
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.”
Reference: Lennon, et al. Black and white individuals differ in dementia prevalence, risk factors, and symptomatic presentation. Alzheimer’s and Dementia.2021; https://doi.org/10.1002/alz.12509