Racial and ethnic disparities in subjective cognitive decline: a closer look, United States, 2015–2018

The United States population has become increasingly diverse. The proportion of racial and ethnic minorities has been growing steadily over the last decade. Minorities, classified as those of any race other than non-Hispanic, single-race Whites by the US Census Bureau, currently constitute about one third of the U.S. population and are composed of several different race categories—Black or African American, American Indian or Alaska Native Asian, Native Hawaiian or Other Pacific Islander. Hispanics are also considered a minority, although strictly speaking Hispanic, or Latino, is defined as an ethnicity rather than a race by the Census Bureau. July 2019 census figures show African Americans to be the largest racial minority, comprising an estimated 13.4% of the population and Hispanics as the largest ethnic minority, comprising an estimated 18.3% of the population [1].

According to the Pew Research Center, minority populations are projected to rise to 56% of the total U.S. population in 2060 [2]. By 2060, minority populations aged ≥65 years will represent 45% of the U.S. population, which is up from 22% in 2014. By 2060, the percentage increase in total population by race and ethnicity is estimated to be 75% for non-Hispanic Whites, 172% for African Americans, and 391% for Hispanics [1, 2]. As the population ages and becomes more diverse, the burden of age-related chronic conditions, such as Alzheimer’s disease and related dementias (ADRD) are projected to disproportionately impact minorities, both in terms of prevalence and severity [3‐5]. Studies indicate that older Blacks and Hispanics are up to twice as likely to have ADRD as older Whites [5]. Minority patients with Alzheimer’s disease (AD) oftentimes present with greater cognitive impairment than their white counterparts. Not only are Hispanic and Black older adults at a higher risk for ADRD than non-Hispanic White older adults; research evidence shows there are disparities in the number of years in late life spent with dementia [4]. It is documented that Hispanics and Blacks at age 50 are estimated to spend a greater number of years with dementia and, consequently, a greater proportion of their remaining lifespan with lower quality of life. The number of years expected to be spent with dementia is approximately three times more for Blacks and 3.5 times more for Hispanics relative to Whites at age 50 [4, 5].

Burden of ADRD, a condition with escalating costs and very limited treatment options, is a growing public health problem for which early detection is critical. In 1982, Reisberg and colleagues [6] classified the course of Alzheimer’s disease progression and introduced the concept of Subjective Cognitive Decline (SCD), possibly one of the earliest detectable symptoms for dementia. SCD characterized by self-experience of deterioration in cognitive performance not detected objectively through formal neuropsychological testing, is considered among the earliest clinical manifestations of AD when individuals have sustained only mild neuronal damage and are able to functionally compensate [7]. SCD has garnered significant interest since it was first put forward. Some research findings indicate as many as 60% of individuals with SCD decline to AD over a 15-year period [8, 9]. Regardless of whether or not SCD leads to more significant cognitive disruption (ADRD, or another dementia), there is a great chance it will impact a person’s ability for self-care, activities of daily living and managing comorbid chronic conditions [10].

The construct of SCD came with a caveat. Since its inception, there has been much confusion in the extant literature about how SCD is formally diagnosed particularly its differentiation from subjective memory concerns [11]. The notion of SCD as a predictor for objective memory impairment and/or progression to ADRD faces an additional challenge in minority groups. Disparate burden of chronic stress and mental health conditions such as depression and anxiety in vulnerable communities may influence the experience of cognitive impairment. Reporting of subjective decline may also be influenced by cultural practices and language barriers [12]. In a community study of African Americans in Baltimore, SCD was found to be associated primarily with factors of psychological well-being, such as higher levels of perceived stress, unrelated to objective cognitive impairment [12]. In another community study in North Carolina that directly compared African Americans and Caucasians, African Americans were less likely to complain of deterioration in memory, despite greater evidence of objective cognitive decline [13]. In a clinic -based sample of Hispanic older adults, SCD was found to be associated with symptoms of depression rather than with concurrent cognitive performance [14]. Measures of cognition, especially subjective measures, appear to be racially biased in terms of efficacy.

Another reason to focus attention on minority populations relates to the severe limitations placed by their social and physical environment [15]. Health status including a person’s risk for dementia is strongly influenced by the environment in which people live, known collectively as the social determinants of health (SDOH). Minority communities are more likely to experience limited access to health care, lower level of education, less income and loneliness/ lack of social support. Research findings have shown a relationship between these factors and dementia [15, 16]. Differences in SDOH contribute to the stark and persistent disparities in other chronic diseases among racial and ethnic minorities. Disparate burden of certain disorders such as heart disease and diabetes that are associated with a higher risk for ADRD [16, 17], make these communities more vulnerable. Furthermore, SCD with a concomitant chronic condition(s) is likely to compound functional limitations and amplify barriers to treatment in these vulnerable communities.

Few population-based studies have explored SCD across race and ethnicity in detail [3]. In recent years, a few national studies have reported on SCD by race/ethnicity [17‐20]. However, their findings were mostly limited to overall SCD prevalence. Disparities by sociodemographic characteristics, functional limitations and chronic conditions amongst racial/ethnic groups with SCD have not been explored in detail at the population level.

This study takes a closer look at ethnoracial disparities in cognitive decline using the Centers for Disease Control and Prevention (CDC) Behavioral Risk Factor Surveillance System (BRFSS) national data. The main objective of this study was to examine the prevalence of SCD by select sociodemographic characteristics and describe SCD associated functional limitations amongst non-Hispanic Whites and the two largest minority populations - non-Hispanic Blacks and Hispanics. Additionally, association of comorbid chronic conditions (angina, heart attack, stroke, high cholesterol, high blood pressure and diabetes) and social determinants (education, income, living alone and health care access) were also described among racial/ethnic groups with and without SCD.

Given persistent disparities in access to quality health care, not all population subgroups reap the benefits of public and private health ADRD initiatives, raising a critical public health issue, especially in lieu of the aging minority population [3‐5]. Our hypothesis is that SCD subgroup is more strongly associated with cognitive risk factors such as chronic disease(s) and SDOH with a disproportionately higher burden in minority populations. Study results will support informed decisions and facilitate prioritization of resources for minority groups with SCD.

Regardless of race/ethnicity, SCD prevalence was associated with differences in comorbid chronic conditions and social determinants. Adults with SCD not only had two or three times the prevalence of some chronic conditions but were also disproportionately affected by social determinants compared to those without SCD. Study findings demonstrated several adverse determinants such as poverty, low education, access to health care and isolation compounded by a higher prevalence of chronic conditions across racial/ethnic subgroups with SCD compared to without SCD.

Previous work has identified statistically significant associations between each of the above listed social determinants and risk for ADRD [25‐28]. Prior research has also elucidated the complications in management of comorbid chronic conditions [17] and association with a higher risk of developing Alzheimer’s or other dementias [5, 16, 29] in persons with SCD. Cognitive dysfunction in areas of learning, memory, and decision-making increase the need for assistance in chronic disease self-management, such as help with medication schedule or medical appointments. Presence of comorbid chronic condition or its treatment may also result in a missed or delayed SCD consult as memory problems could be attributed to the chronic condition or treatment side-effects If a person has memory problems co-occurring with a chronic condition or treatment, cognitive dysfunction might be regarded as related to the condition or the treatment and not to early stages of ADRD. The patient may not report these symptoms or if reported, the provider may misattribute them to medication side effect [16, 17, 29].

SCD is a concern, by itself. It is also poignant that measures, which are necessary to manage SCD and reduce the risk for progression to ADRD, are maybe exponentially more difficult for those with both adverse social determinants and comorbid chronic conditions. Within this context, disparities by race were evident. Blacks and Hispanics with SCD were disproportionately affected by social inequalities and comorbid chronic conditions compared to whites with SCD. These two minority groups with SCD were more likely to be less educated, had lower annual household incomes and lack of access to health care as compared to whites with SCD. In contrast to the white subgroup with SCD, Hispanics and Blacks with SCD also reported a greater likelihood of living alone. Individuals with cognitive impairment who live alone are more vulnerable [27, 28]. They may have an increased risk for injury to self or others and report more unmet needs such as managing money, medications, mobility, and some activities of daily living. Older adults who live alone are less likely to use health services and are at a risk for poor health outcomes [27, 28]. In addition, Hispanics and Blacks also reported highest prevalence of SCD in the relatively younger, 45–54-year age group as compared to Whites. Irrespective of the reasons, it is safe to comment on the health and financial consequences ensuing from a higher SCD prevalence in the less than 55 years age group. Adults aged 45–54 years are at the peak of their careers regards salary, productivity and contributions to their retirements [17, 18]. SCD may lead to functional limitations that have substantial social and economic impact on these individuals and their families [18, 30].

High cholesterol, high blood pressure and diabetes were the most prevalent chronic conditions across racial/ethnic groups in this study. Blacks with SCD had the highest prevalence of high blood pressure while Hispanics with SCD led the prevalence for diabetes. A significantly higher burden of chronic conditions was evident in Blacks with SCD- close to 80 % reported at the least one chronic condition.

Significant disparities in functional limitations were noted by race and ethnicity among those with SCD. Functional impairment in activities of daily living has been documented in prior studies of older adults with cognitive impairment [17, 18, 31, 32]. Population-based estimates have reported weighted prevalence of ≥1 functional limitation varying from 45% [31] and 51% [18] to 57% [33]. Hispanics and Blacks had a higher prevalence of SCD-related limitations that affected work, household chores, or social activities as compared to whites. Functional limitations predict significant increase in support from formal and/or informal caregiver resources [33, 34]. This care represents a significant time commitment for families and a significant economic cost to society [33].

Less than half of Blacks (46.8%) and Hispanics (44.5%) with SCD had discussed their cognitive decline with a health-care provider. Given the association of AD with dependence and disability for a long duration, the earlier the detection, the sooner people and their families can receive information regarding better management. The benefits of early assessment, diagnosis, and disclosure of that diagnosis are well known, so efforts focused on care navigation and culturally competent physician-initiated conversations on cognitive health are recommended [35]. Opportunities for improvement could also build on the frequent interactions amongst vulnerable age groups and nonphysician care providers. Trusted culture -sensitive relationship with health care providers could encourage older adults and their families to express concerns about the older adult’s cognition facilitating earlier diagnosis of dementia [36]. It is interesting to note that Healthy People 2030, a vital framework for prioritizing health issues in U.S. has included a new objective of increasing the proportion of adults with SCD who discuss their confusion or memory loss with a health-care professional by five percentage points over the next decade [37].

This study is subject to several limitations. First. BRFSS is a telephone survey that samples from noninstitutionalized adults. People living in nursing homes and long-term care facilities without cell phones assigned by a phone company may not be included. It is likely that both SCD and chronic conditions are more common among older adults living in these institutions. Second, SCD by definition is self-reported, and not an objective assessment. Third, it may underrepresent people who have severe cognitive impairment because of the functional capacity required to participate in the survey. Additionally, BRFSS measure of SCD asks only about changes in memory or thinking which may not capture the full domain of cognitive dysfunction [22]. Despite these limitations, the BRFSS is a uniquely powerful tool to provide the national prevalence of cognitive decline and related health issues among racial and ethnic groups, due to its large sample size and proven reliability and validity.

In lieu of an aging U.S. population, SCD is a critical public health issue. Of particular concern is the demographic projection for aging minority populations and anticipated rise in burden of ADRD. Given the gravity of this situation, it is vital to put a spotlight on cognitive impairment related disparities that may exist among minority communities. Population-based measures of SCD can be extremely useful to the public health community, health care providers, and policymakers in prioritization and planning efforts [38]. This study uses population data to explore the profile of ethnoracial minority groups with SCD. Notable findings include a significantly higher burden of chronic conditions and adverse social determinants among Blacks and Hispanics with SCD, predicting worse cognitive health outcomes. Not surprisingly, SCD associated functional limitations were also found to be significantly higher in Hispanics and Blacks compared to whites, foretelling a need for increased support from caregivers. Moreover, less than 50% of the minority groups had discussed their SCD with a provider. Healthy People 2030’s new objective to increase the proportion of adults with SCD who discuss their confusion or memory loss with a health-care professional by five points encourages ongoing analyses of SCD data. It would be interesting to measure progress towards this goal amongst minority groups over time. Study results are expected to help public health stakeholders make data -driven decisions and be better prepared for the challenges associated with disparities in cognitive decline. Lastly, this study also serves to inform and bolster clinical SCD related research in minority subgroups. Population -level results as presented in this study can guide future researchers in targeted study design and sampling from vulnerable groups.