I am currently a third year undergraduate student at Emory University studying Biology and Religion while on the pre-med track. I am also presently the Digital Marketing and Communications Intern at enlightenbio due to my passion for social media, public relations, molecular biology, and precision medicine. After graduating, I hope to facilitate the convergence of science and religion through a career in medicine domestically, and ultimately internationally, with special areas of interest in whole person care, global medicine, and serving underserved populations. I ultimately chose to write about this content due to my interest in how environmental and genetic factors overlap and affect people’s dispositions to specific diseases and the intersection with the medical field.
There is no question that medicine has made unbelievable strides over the course of history: Cutting-edge technologies, targeted medications, innovative procedures, and the evolution of precision medicine have all acted as key players in these advancements. All these accomplishments represent incredible milestones not only for the medical field, but also society, and new advancements continue to emerge every single day. However, with all this progress, there is still a glaring problem that needs to be addressed within the healthcare world: race disparities that impact people’s susceptibility to developing specific ailments and illnesses. This can most clearly be visualized through populations that are at a higher risk for Alzheimer’s disease and related dementias. Alzheimer’s disease is an irreversible, progressive brain disorder that is currently the fifth most common cause of death for Americans ages 65 and older. People living with Alzheimer’s undergo significant memory damage, and upon progression of the disease, they eventually struggle greatly with completing even basic tasks such as bathing, feeding, and dressing.
Figure 1: Breakdown of Alzheimer’s disease by race and ethnicity and projection of expected growth for Alzheimer’s disease by 2060. Image credit: CDC.
“By 2060, around 3.2 million Hispanics and 2.2 million African Americans alone will be affected by Alzheimer’s disease and related dementias.”
Through a CDC (Center for Disease Control) study, researchers found that among people ages 65 and older, African Americans have the highest prevalence of Alzheimer’s disease and related dementias (13.8%), followed by Hispanics (12.2%), non-Hispanic whites (10.3%), American Indian and Alaska Natives (9.1%), and Asian and Pacific Islanders (8.4%). The CDC deduces that as the U.S. population continues to increase, so will the number of people affected by Alzheimer’s disease and related dementias – especially within minority populations such as African Americans and Hispanic Americans. The CDC projects that by 2060, around 3.2 million Hispanics and 2.2 million African Americans alone will be affected by Alzheimer’s disease and related dementias, a number that is triple the current amount. This growth within the African American and Hispanic American population is predicted to result from a combination of a decrease in people dying from other chronic diseases and an increase in people surviving into older adulthood, and as such, an increase in risk for Alzheimer’s disease and related dementias. Evidently, minority populations, especially African American adults, experience a disproportionate incidence of Alzheimer’s disease.
Clear genetic link between Alzheimer’s disease and race
Several studies explore genetic disposition for Alzheimer’s disease for different races and have found that there is a clear genetic link between Alzheimer’s disease and race.
- In a discovery-based plasma proteomics study aimed to identify potential diagnostic biomarkers for Alzheimer’s disease, researchers analyzed plasma samples of adults that were either clinically diagnosed with Alzheimer’s disease or were cognitively normal and self-reported that they were either African American/Black or non-Hispanic White. (Khan et al., 2021). They identified 740 proteins and found that while 6 proteins were differentially-expressed in Alzheimer’s disease independent of racial and ethnic background, 25 proteins were differentially expressed in Alzheimer’s disease within one racial and ethnic background group. This differential racial expression illustrates the necessity for more study designs in Alzheimer’s disease biomarker discovery that are inclusive of varying racial and ethnic groups which are currently underrepresented (e.g., African American adults).
- In another proteomics-based study, researchers looked at postmortem brains from African American/Black and non-Hispanic white adults that were diagnosed with Alzheimer’s disease and compared it to counterpart individuals that were cognitively normal (Stepler et al., 2020). They examined several brain regions: the hippocampus, inferior parietal lobule, and globus pallidus regions and discovered 568 differentially-expressed proteins in Alzheimer’s disease. This study resulted in the identification of 185 proteins that exhibited statistically significant race and diagnosis interactions across these brain regions (Stepler et al., 2020).
- A third study conducted by the Knight Alzheimer Disease Research center at Washington University (Morris et al., 2019) looked at the cerebrospinal fluid (CSF) concentrations of tau protein between African American and white individuals affected by Alzheimer’s disease in order to better understand the racial disparities in molecular biomarkers. They found that out of the participants who reported past family history of dementia, the participants’ mean total hippocampal volumes and mean total CSF concentrations of the tau protein were lower. This difference, especially the lower CSF concentrations of total tau and phosphorylated tau in African American individuals, suggests a genetically linked risk factor for Alzheimer’s within African American individuals compared to white individuals. Another study corroborated these findings, revealing that African American participants had decreased cortical volumes compared to white participants indicative of greater neurodegeneration.
Evidently, there is a significant genetic link between African American/Black adults and susceptibility to Alzheimer’s disease and this may account for the disproportionate ratio of African Americans afflicted with Alzheimer’s disease.
“African American/Black adults… were less likely than their non-Hispanic white counterparts to seek out treatment when afflicted with mild cognitive impairment and were less likely…to accept Alzheimer’s disease pharmacotherapy treatment upon receiving a disease diagnosis.”
While a significant portion of this problem is a result of genetic dispositions of differing populations, factors that may affect expression of disease (e.g., the socioeconomic barriers, systemic inequalities, or lack of studies and research geared toward exploring this issue) are key contributors to the alarmingly evident disparity. For example, educational quality, healthcare access, willingness to seek care and treatment, the stress of continual discrimination, and increased susceptibility to comorbid diseases all contribute to socioeconomic disparities, psychological factors, and health risks. As a result, these all intertwine to impact racial differences in Alzheimer’s disease as found by Morris et al. (2019). In several studies that explored African American/Black adults and their willingness to seek out treatment for cognitive issues, they found that they were less likely than their non-Hispanic white counterparts to seek out treatment when afflicted with mild cognitive impairment (Burke et al., 2017). Furthermore, they were less likely than their non-Hispanic white counterparts to accept Alzheimer’s disease pharmacotherapy treatment upon receiving a disease diagnosis.
There is a severe lack of research that incorporates diverse study populations
Despite African Americans forming 13.3% of the population in the United States (Morris et al., 2019), they are usually underrepresented in Alzheimer’s disease clinical cohort studies. As a result, the majority of data gathered from research done for the Alzheimer’s field has come from white populations. Data from the National Alzheimer’s Coordinating Center revealed:
- Only 6.1% of the neuropathological data from 5283 brains was from African American individuals.
- Only a few studies have compared molecular biomarkers of Alzheimer’s disease between African American and white populations to determine potential disparities in Alzheimer’s disease mechanisms.
“Although racial and ethnic minorities make up 39% of the U.S. population, their participation in clinical trials only range from 2%-16%.”
Biological markers of Alzheimer’s disease are essential because they allow to study and monitor Alzheimer pathophysiologic characteristics in humans. Genetics, socioeconomic factors, and comorbidities all collaborate and interweave to have a significant impact on African American/Black adults and their susceptibility to Alzheimer’s disease. Not only is there a severe lack of medical research focused toward members of racial and ethnic minority groups within the realm of Alzheimer’s disease, but in the medical field in general, racial and ethnic minority groups and older individuals are rarely studied, as pointed out by Flores and team (2020).
This problem is especially prevalent in studies conducted for evaluation of potential therapeutics in clinical trials (Kantor, 2021):
- Although racial and ethnic minorities make up 39% of the U.S. population, their participation in clinical trials only range from 2%-16%.
- Less than 5% of trial participants are African American/Black despite the fact that they make up around 14% of the American population.
- 1% of trial participants identify as Latino despite making up 18% of the U.S. population.
Wide-range of racial and minority disparities across medicine
While I have described Alzheimer’s disease and dementia as an example, racial disparity can be observed across all areas of medicine, including vaccination, as a recent JAMA study by Flores and team (2021) pointed out. Despite advancements, equity in clinical trial enrollment remains an issue. In a report examining the frequency in which minorities were the primary focus of National Cancer Institute (NCI)–sponsored clinical trials, the researchers found, that less than 2% of clinical trials over a period of two decades [1993-2013] had minorities as the primary focus and that the percentage of manuscripts reporting their study data by race/ethnicity ranged from 1.5% to 58% (Chen et al., 2014). Sadly, this still applies today.
- Based on data from completed US-based COVID-19 vaccine trials: Registered through ClinicalTrials.gov, white individuals are being overrepresented and African American/Black individuals and American Indian/Alaska native individuals are being underrepresented (Flores et al., 2021).
- Pediatric trials: African American/Black individuals and Hispanic/Latino participants are vastly underrepresented (Flores et al., 2021).
- Age-related discrimination: Participants who were aged 65 years or older formed only 12.1% of trials that reported age. This illustrates the severe underrepresentation of older adults in US-based vaccine clinical trials and urgency of implementing more diverse populations in all vaccine trials (Flores et al., 2021).
- Race-related discrimination: American Indian/Alaska Native and Hawaiian/Pacific Islander participants were not included in the majority of trials that reported race/ethnicity (Flores et al., 2021).
- Demographic factors that affect cancer clinical trials: Sociodemographic factors played a large role in impacting enrollment, as determined through the use of multivariable regression analysis (Meyer et al., 2021) . Individuals from wealthier socioeconomic status, of Hispanic ethnicity, and of younger age were most likely to participate in cancer clinical trials. Through these findings the authors concluded that people of color are more likely to participate in cancer clinical trials. It is suggested that systemic barriers may have a larger effect on participation in clinical trials than race on its own.
Table 1: Rates of participation by demographic factor, unadjusted (Meyer et al., 2021).
The life science community needs to take action
This lack of diversity in clinical trials is alarming because it inhibits the ability to provide accurate and broadly applicable information for the discovery and development of medical advancements in the future. Stephanie Monroe, the executive director of African Americans Against Alzheimer’s, summarizes the need for diverse communities within clinical research well: “When you don’t have inclusion of diverse communities, you run the risk of making assumptions about drug safety and effectiveness that may not be accurate. Generalizing findings of the current majority of participants – white, European men – to African-Americans, Latinos, women and others may be embracing false assumptions about the lack of differentiation between what is fast becoming the new majority”.
“Research is in desperate need of incorporating more racial, ethnic, and socioeconomically diverse study populations in any type of population study, whether it being a research study or a clinical trial.”
Another action that could be taken would include focus on accessible care through relief of structural and financial barriers to enrollment as suggested by Meyer et al. (2021). As seen through various studies, minority populations, especially African American and Hispanic American populations, need to be represented and considered in Alzheimer’s disease studies, especially studies done on a larger scale (Stepler et al., 2020).
In summary, there is no doubt that minority populations, especially African American/Black populations, experience an extremely disproportionate rate of Alzheimer’s disease, and this is heavily influenced both by genetic links and social factors such as structural barriers, inaccessible healthcare, socioeconomic status, distrust of medical research, etc. This discrepancy is spurred on by the alarming lack of studies that incorporate diverse populations for their participants, as seen through the clinical trials mentioned previously. This lack of representation of all segments of the general population is and will be extremely detrimental in that it does not provide an accurate representation for the discovery and development of increasingly sophisticated medicine. It has resulted in neglect of the African American/Black community especially within the world of Alzheimer’s disease research and medicine in general. This underrepresentation has had extremely negative effects both directly and indirectly. This absence of sufficient research has inhibited the discovery and development of new methodologies or medications that might otherwise be significantly beneficial in decreasing this wide racial disparity.
In response to this,..
“..the medical research community has a duty to be racially and ethnically inclusive in their study demographics.”
Burke et al., Dementia-Related Neuropsychological Testing Considerations in Non-Hispanic White and Latino/Hispanic Populations. (2019) Psychol & Neurosci, Jun;12(2):144–168.
Chen et al., Twenty years post–NIH Revitalization Act: enhancing minority participation in clinical trials (EMPaCT): laying the groundwork for improving minority clinical trial accrual: renewing the case for enhancing minority participation in cancer clinical trials. (2014) Cancer. 2014;120 (suppl 7):1091-1096.
Eian Kantor, Why Racial Diversity in Clinical Trials Is so Important. (Nov 2020) antidote blog.
Flores et al., Assessment of the Inclusion of Racial/Ethnic Minority, Female, and Older Individuals in Vaccine Clinical Trials. (2021) JAMA Network Open, Feb; 4(2): e2037640.
Khan et al., Why Inclusion Matters for Alzheimer’s Disease Biomarker Discovery in Plasma. (2021) J Alzheimer’s Dis, 79(3):1327-1344.
Meeker et al., Socioeconomic Status Mediates Racial Differences Seen Using the AT(N) Framework. (2021) Ann Neurol. Feb;89(2):254-265.
Meyer et al., Sociodemographic Diversity in Cancer Clinical Trials: New Findings on the Effect of Race and Ethnicity. (2021) Contemp Clin Trials Commun,Jan 20;21:100718.
Morris et al., Assessment of Racial Disparities in Biomarkers for Alzheimer Disease. (2019) JAMA Neurology, JAMA Neurol, 76(3):264-273.
Stepler et al., Inclusion of African American/Black Adults in a Pilot Brain Proteomics Study of Alzheimer’s Disease. (2020) Neurobiol Disease, Dec;146:105129.