Facilitators,Challenges,and Messaging Strategies for Hispanic/Latino Populations Participating in Alzheimer’s Disease and Related Dementias Clinical Research: A Literature Review

Abstract

Alzheimer’s disease and Alzheimer’s disease-related dementias (AD/ADRD) disproportionally affect Hispanic and Latino populations, yet Hispanics/Latinos are substantially underrepresented in AD/ADRD clinical research. Diverse inclusion in trials is an ethical and scientific imperative, as underrepresentation reduces the ability to generalize study findings and treatments across populations most affected by a disease. This paper presents findings from a narrative literature review (N = 210) of the current landscape of Hispanic/Latino participation in clinical research, including the challenges, facilitators, and communication channels to conduct culturally appropriate outreach efforts to increase awareness and participation of Hispanics/Latinos in AD/ADRD clinical research studies. Many challenges identified were systemic in nature: lack of culturally relevant resources; staffing that does not represent participants’ cultures/language; eligibility criteria that disproportionately excludes Hispanics/Latinos; and too few studies available in Hispanic/Latino communities. The paper also details facilitators and messaging strategies to improve engagement and interest among Hispanics/Latinos in AD/ADRD research, starting with approaches that recognize and address the heterogeneity of the Hispanic/Latino ethnicity, and then, tailor outreach activities and programs to address their diverse needs and circumstances. The needs identified in this article represent longstanding failures to improve engagement and interest among Hispanics/Latinos in AD/ADRD research; we discuss how the field can move forward learning from the experiences of the COVID-19 pandemic.

Keywords

Alzheimer’s disease clinical trial dementia Hispanic Latino research subject recruitment

INTRODUCTION

Clinical research studies on Alzheimer’s disease and Alzheimer’s disease-related dementias (AD/ADRD) have long struggled with adequate representation from racial and ethnic populations other than non-Hispanic White [1, 2]. Underrepresentation undermines researchers’ abilities to understand how ethnicity and cultural factors interact with genetic and environmental factors related to AD/ADRD [3 –6]. Despite ongoing outreach efforts and national mandates, the problem persists and is especially salient for Hispanic/Latino populations [7, 8]. Within the United States (U.S.), Hispanic and Latino (Hispanic/Latino) individuals experience AD/ADRD at higher rates than non-Hispanic Whites, and it is projected by 2060, U.S. Hispanic/Latino adults ages 65 and older will have the largest rise in AD/ADRD cases compared to non-Hispanic Whites and African Americans [9 –12]. As well, the growing U.S. Hispanic/Latino population is at high risk for dementia-related risk factors, such as cardiovascular disease, diabetes, high blood pressure, and obesity [9 , 13–16]. Yet, according to the National Institutes of Health’s (NIH) National Institute on Minority Health and Health Disparities, fewer than 8% of enrollees in clinical trials are Hispanic/Latino even though they constitute nearly 18% of the U.S. population [11].

Representation of Hispanic/Latino populations in clinical research studies is critical to finding treatments and cures for AD/ADRD that are safe and efficacious for all populations. Towards this goal, the National Alzheimer’s Project Act was signed into law in 2011 to support efforts to slow the trajectory of AD/ADRD [17]. The law specifically calls for a plan to accelerate research and improve the health outcomes for people living with AD/ADRD and their families. In response to this plan, the National Institute on Aging (NIA), which oversees NIH research on AD/ADRD, released Together We Make the Difference: National Strategy for Recruitment and Participation in Alzheimer’s and Related Dementias Clinical Research [18]. One of the aims of the national strategy is to improve recruitment and retention of underrepresented participants, including Hispanics/Latinos, to ultimately address the challenges around building awareness, interest, and trust among these populations. Related, the Clinical Trials Transformation Initiative (CTTI), a public-private partnership of 80 + organizations to develop and drive practices to increase the quality and efficiency of trials [19], has published a comprehensive set of recommendations to improve trial recruitment. CTTI recommendations focus on three areas: 1) trial design and protocol development; 2) trial feasibility and site selection; and 3) communication [20]. Central to CTTI’s comprehensive review is the need to first understand the interests, needs, and perspectives of potential trial participants and their influencers and then to address each of the three areas based on stakeholders’ insights.

The NIA is pursuing the development and implementation of a multipronged, long-term evidence-based strategy to increase awareness and interest in AD/ADRD clinical research studies among underserved populations, including Hispanic/Latino populations in the U.S. To inform its strategic development process, a narrative literature review was conducted to qualitatively understand the previously published challenges, motivations, and facilitators to increase Hispanic/Latino representation in AD/ADRD clinical research, and to provide insights into potential messaging and communication channels that may resonate among Hispanic/Latino communities. This paper presents the findings of the literature review. A similar review was conducted by Gallagher-Thompson and colleagues in 2003, though they predominantly focused on AD/ADRD barriers affecting participation of Hispanic/Latino caregivers in clinical research [21]. In their article, Gallagher-Thompson et al. summarized published barriers to recruitment over the previous decade and provided specific recommendations for recruitment and retention of Hispanic/Latino Americans in caregiving research. They also noted that much work needs to be done and that changes in society would potentially modify their findings moving forward.

We reviewed published literature over the past decade (2010–2021; N = 210) but also included seminal papers published earlier that were identified in articles’ reference sections (N = 20). The review used PubMed and Google Scholar to search both free text and Medical Subject Heading (MeSH) using the following terms: Alzheimer’s disease; Alzheimer’s disease and related dementias (ADRD); clinical trials; recruitment; Latino; Hispanic; recruiting minorities; elderly minorities; barriers; and recruitment messaging. Each article was reviewed by three authors and key findings were qualitatively categorized by recruitment challenges/barriers, facilitators, and messaging found to influence Hispanic/Latino involvement in AD/ADRD clinical research. In the remainder of this article, we provide an updated narrative of the landscape around participation of Hispanic/Latino individuals in AD/ADRD clinical research, particularly in relation to the findings almost 20 years prior.

Although we use the label “Hispanic/Latino” in this article, it is vital to recognize that Hispanics/Latinos in the U.S. represent a myriad of races, cultures, nationalities, language dialects, acculturation, educational attainment, migration histories, and economic levels, rather than one homogeneous group [22 –30]. According to a Pew Research Center (2012) nationally representative survey of Hispanic/Latino individuals in the U.S., 69% did not perceive there to be a shared common culture among the U.S. Hispanic population [31]. As described by Paredes (2013), “The term [Hispanic] is rooted in the use of language rather than in ethnicity” (p. 100) and carries the overtones of “oppression” exerted by Spaniards to colonize the Americas—describing Hispanics/Latinos as a homogeneous group leads to inaccurate and misleading generalizations [30].

Often, however, researchers aggregate data into one category “Hispanic” or “Latino” rather than measuring distinctions by subgroups; reasons for aggregating data are often a result of limited resources to sample by subgroups or limited/no access to large cohorts by subgroup [23 , 33]. Mateos et al. (2009) provide a thorough summary of the complications around measuring ethnicity and note that improving ethnicity classifications is a “trade-off between their validity and utility” (p. 1439): greater numbers of groups within a classification are more granular and inclusive, and therefore more valid; yet, with more granularity, the utility of the classification is reduced given the increased difficulty in interpretation and analyses [23]. Though this narrative review can only touch upon the limitations surrounding the measurement of ethnicity, we emphasize that in the context of a public health intervention, the aggregation of Hispanic/Latino groups can result in a general, one-size-fits-all approach—which risks lowering an intervention’s level of interest, relatability, and influence on its participants [34, 35]. Of the publications cited in this narrative review, many used the term “Hispanic” or “Latino” in describing their samples; as a result, we use the combined term “Hispanic/Latino” when discussing these articles. In all other cases, we note when an article references a specific Hispanic/Latino subgroup (e.g., Mexican American) or other group (e.g., immigrant).

CHALLENGES TO RECRUITMENT OF HISPANIC/LATINO POPULATIONS INTO CLINICAL TRIALS

Understanding challenges or barriers to Hispanic/Latino AD/ADRD clinical research participation is a necessary step in developing recruitment strategies that effectively resonate with and address the populations’ needs. A review of the literature identified nine thematic challenges/barriers reported to negatively impact participation of Hispanic/Latino individuals in AD/ADRD clinical research (see Table 1a). Most, if not all, are driven by systemic barriers, such as lack of community outreach or infrastructure, racial/ethnic inequities, or exclusion from research planning upfront [36 –41]; changes to address these barriers will require efforts beyond increasing individuals’ personal interest to participate in a clinical study.

Table 1

Challenges/facilitators affecting participation of Hispanic/Latino individuals in AD/ADRD research

(a) Challenges affecting Hispanic/Latino participation in clinical research	(b) Facilitators to Hispanic/Latino participation in clinical research
•Lack of educational outreach to Hispanic/Latino communities about AD/ADRD and clinical research	•Positive relationship with health care providers
•Limited cultural competency and linguistic diversity among researchers	•Altruistic intentions to help one’s family and community
•Low health literacy levels	•Involving family in medical decision-making
•Fear that participation may negatively affect immigration status	•Desire to increase health care knowledge and better one’s health
•Lack of trust in research/investigators	•Diversification of health care professionals and study staff
•Inequitable access to and engagement with health care	•Implementing broader community engagement efforts
•Logistical and financial challenges to attending study appointments
•Caregiver burden
•Stringent study inclusion and exclusion criteria

Lack of educational outreach to Hispanic/Latino communities about AD/ADRD and clinical research

In general, a lack of knowledge about AD/ADRD and clinical studies has been shown to negatively affect participation, as increased understanding may facilitate a willingness to participate in research [42 –46]. Several studies have reported that levels of knowledge about AD/ADRD and clinical research differ widely across Hispanic/Latino populations [42–44 , 47]. A national study examining public opinion on AD, specifically, found that Hispanic/Latino participants were significantly less likely than White respondents to know that AD was not the term for normal memory loss, or that certain steps may be taken to “maintain a healthy memory and reduce the chances of getting Alzheimer’s disease” (p. 235) [48]. A qualitative study assessing cultural beliefs about dementia and autosomal dominant Alzheimer’s disease (ADAD) among Mexican Americans found that while many participants understood that ADAD was inherited, most had a generally low level of knowledge about the disease and believed it was a part of normal aging or was a mental illness caused by bad habits [49]. Though findings indicate varying levels of knowledge among Hispanic/Latino populations regarding AD/ADRD and clinical trials, research also indicates that Hispanic/Latino individuals are often not made aware of AD/ADRD or clinical trial opportunities in their communities [44 , 50–52]. Garza et al. (2017), for example, reported that a key factor that increased Hispanic’s/Latino’s likelihood of participating in future research studies was “ever been asked to participate.” Of the 15% of their Hispanic/Latino sample (N = 1264) who had ever been asked to participate in medical research, 65% reported they went on to participate [51]. According to the National Hispanic Council on Aging, there is a dearth of health information resources available within Hispanic/Latino communities, including a lack of culturally and linguistically adequate Alzheimer’s resources for Hispanic/Latino populations [53]. More importantly, evidence highlights that many Hispanic/Latino individuals are willing to participate if they are made aware of clinical trial options [42 , 54–56]; thereby suggesting that participation might be influenced more by lack of access to information versus a lack of interest.

Limited cultural competency and linguistic diversity among researchers

Research has shown that cultural beliefs and practices play an important part in making decisions about one’s health, and yet, U.S. health care systems rely predominantly on Western constructs to provide health education and care [57, 58]. For example, among some Hispanic/Latino cultures the role of family members is elevated, and medical decisions are made by family consensus [59 –62]. However, researchers may not account for this cultural practice and subsequently fail to provide processes or resources that accommodate additional family involvement [63]. According to the literature, researchers must ensure their clinical study designs and processes are culturally competent, respectful, and acceptable if they are to successfully enroll greater proportions of Hispanic/Latino individuals in their AD/ADRD studies [13, 64]. Valuing and honoring diversity and cultural differences is central to cultural competence, as well as adapting services when needed [65]. Of key importance is the ability of clinical staff to communicate with participants in the language they are most comfortable speaking [47], which can be complicated for bilingual persons living with dementia who may revert to their native language as the disease progresses [66]. Despite the need for bilingual and Spanish language opportunities, Egleston et al. (2015) found that a growing proportion of trials registered with ClinicalTrials.gov are requiring English fluency to join the study, which may even more so exclude predominately Spanish-speaking participants [67].

Additionally, challenges occur when informational materials about AD/ADRD clinical research are not culturally competent or are not written in an individual’s preferred language [37 , 69]. Historically, Spanish health resources and materials have been generated in English first and then translated into Spanish; unfortunately, this method can lead to mistranslations and disregard of the audience’s cultural perceptions and understanding of the disease [70]. The decision to participate in a clinical study is often complicated, lengthy, and stressful [71 –73]. When researchers cannot communicate in participants’ preferred language or fail to provide study materials that are culturally and linguistically appropriate, they are ultimately creating additional hurdles for participants to overcome when deciding if a clinical study is right for them.

Low health literacy levels

The Patient Protection and Affordable Care Act defines health literacy as, “the degree to which an individual has the capacity to obtain, communicate, process, and understand basic health information and services to make appropriate health decisions” [74]. According to the Institute of Medicine (IOM), limited health literacy affects the management of one’s health and illnesses, including decision-making abilities, adherence to therapy, and health care utilization [75]. Low levels of health literacy have been documented across a range of demographic groups but disproportionately affect older adults and individuals identifying as Hispanic/Latino [76]. Among U.S. Hispanic/Latino subgroups, health literacy is understudied though some evidence suggests that primarily Spanish-speaking Hispanic/Latino immigrants in the U.S. are at risk for having low health literacy due in part to the many challenges they confront from a predominantly English-language system [76 –78]. Additionally, a long history of medical discrimination combined with inconsistent or unstable health insurance coverage has deterred many Hispanic/Latino individuals from accessing health care, which results in reduced health-literacy levels, since health literacy is closely linked to individuals’ experiences with the health care system [78 –81]. Moreover, these deterrents also prevent Hispanic/Latino individuals from visiting health care professionals, an important source of information for AD/ADRD clinical trials [82]. Within the context of clinical trial participation, low health literacy has the potential to affect individuals’ understanding of the disease, trial options, informed consent, study design, risks and benefits, and how to contact the study team [47, 83]. Therefore, any outreach efforts developed to increase interest in clinical research must be designed to accommodate a range of health literacy levels.

Fear that participation may negatively affect immigration status

Participating in the U.S. health care system, overall, may pose greater concerns to Hispanic/Latino individuals who have immigrated to the U.S. due to risks of discrimination based on immigration status and deportation [84 –87]. In a study of Hispanic/Latino participants with HIV, for example, many delayed health care or missed medical appointments due to their undocumented status, expressing difficulties related to paperwork and ID requirements, lacking paid leave or health insurance, or fearing they would lose their job [88]. Immigration status concerns also have been shown to affect decisions related to clinical trial participation [44 , 89]. In a small study that interviewed Hispanic/Latino family caregivers who were unable to participate in an intervention for the caregivers of people with AD, researchers found that fear of revealing their loved one’s immigration status was a perceived barrier to enrollment [90]. Some researchers recommend that clinical trial researchers clearly state that immigration status will not be asked, reported, or revealed as a result of participation, but it is unknown whether this will have a meaningful impact on Hispanic/Latino immigrants’ propensity to participate in research [91]. Regardless, asking participants’ immigration status should only be done so if it is justifiably related to a trial’s study design and its rationale described clearly and in plain language during the informed consent process.

Lack of trust in research/investigators

Another challenge to research participation among Hispanic/Latino individuals is a belief held by some that health care professionals are not trustworthy; this belief extends to mistrust in those conducting clinical trials, which in turn may contribute to reticence among Hispanic/Latino populations to participate in clinical research [47 , 92–94]. Mistrust among Hispanic/Latino individuals has been documented to stem from an array of elements, such as past mistreatment and discrimination from medical professionals, experiences of scientific misconduct, and an awareness of the history of mistreatment and abuses levied against diverse populations in research studies [43 , 94–98]. Several articles also reported that Hispanic/Latino individuals are more wary of medical or research institutions compared to non-Hispanic Whites, resulting in a lower likelihood that they would be willing to participate in clinical research [37 , 95]; however, such wariness might be a reaction to researchers’ implicit biases and stereotypes expressed toward diverse groups [99, 100]. A recent report by the Alzheimer’s Association highlights the discrimination faced by several racial and ethnic groups with respect to accessing and receiving dementia care [101]. Niranjan and colleagues (2020) found that some recruiters perceived some participants as more challenging to recruit based on their diverse, ethno-racial background and therefore recruiters were less likely to engage or share trial opportunities as a result of their stereotypes [102]. Researcher’s perception of mistrust has ramifications: Researchers who perceive a population as less likely to participate in clinical trials are often less likely to invest in a proper outreach strategy [103]. Addressing past misconduct in the field and undertaking systemic actions toward building trust between research investigators and communities is crucial and is among top recommendations of best practices for increasing recruitment into clinical studies [104, 105].

One avenue to increase trust that has been underutilized in clinical research is the sharing of study outcomes with participants [106 –109]. According to the World Medical Association’s Declaration of Helsinki (1964), clinical researchers have an ethical obligation to disseminate results to research participants, without whom the research would not have taken place [110], in order to solidify trust and lessen the power imbalances between researcher and participant [107, 111]. Sharing the results of a study has been shown to promote engagement in the research, establish trust in underserved communities, and increase participation [111, 112], while forgoing this practice can lead to feelings of disrespect and decreased motivation to participate in any future trials [113].

Inequitable access to and engagement with health care

Historically underserved populations are less likely to have access to medical care and often receive worse care when seeking it [114]. Moreover, research studies are not as readily available in underserved, racially and ethnically diverse communities [11 , 116]. This inequality in health care access derives from a multitude of socioecological factors whose relationships are complex and multifaceted [114 , 118]. Among Hispanic/Latino groups, there are documented high rates of individuals who lack health insurance, meaning they have limited access to physicians, who can be an important source of information about AD/ADRD and clinical trial opportunities [47 , 95]. According to an analysis of the 2017 American Community Survey one-year estimates by the Kaiser Family Foundation, even with the passage of the Affordable Care Act (ACA) and Medicaid expansion, Hispanic/Latino Americans remain one of the highest uninsured groups and are tied with American Indian/Alaska Native populations for the most uninsured group among Americans ages 65 and older in the U.S. [119]. One study examining participation in oncology clinical trials found that fears surrounding health insurance coverage is a major concern among individuals considering participating in a clinical trial [120]. Taken together, these findings demonstrate that low Hispanic/Latino participation in AD/ADRD clinical research has roots that extend into systemic social and ecological inequities.

Logistical and financial challenges to attending study appointments

Another major barrier to participation in AD/ADRD research involves the logistical and financial challenges of attending study appointments. One study that examined the attitudes of physicians towards clinical trials found that primary care physicians cited logistical issues as a common concern among their patients about clinical trials [121]. Logistical challenges include access and costs related to childcare, gas, transportation to and from the clinical study site, hotel stays during the study, and money lost from missing work [50 , 122]. Hispanic/Latino individuals for whom financial constraints are prohibitive are especially affected, as the out-of-pocket costs of caregiving are highest among Hispanic/Latino caregivers and Medicare payments are greater for Hispanic/Latino individuals with a dementia diagnosis than for non-Hispanic Whites [123, 124]. According to Rosenthal Gelman (2010), one-third of their Hispanic/Latino caregivers declined to participate in an AD study, after screening in as eligible, due to family priorities that would not allow them the time to participate [90]. Another study found that up to 30% of their older adult population relied on three or more unpaid caregivers, further compounding the complexities of coordinating study visits [125]. Several studies have addressed these concerns by identifying and addressing study-specific logistical barriers directly in the study’s trial design. A focus group of Mexican Americans found that a major incentive for participation in clinical studies was the elimination of logistical barriers, such as providing transportation options, compensating milage, and providing food [44]. In a study that recruited low-income multi-ethnic women, researchers employed strategies that successfully addressed logistical barriers to recruitment and retention such as holding baseline interviews in a convenient location, conducting brief follow-up interviews through the phone instead of in-person, and providing participants the opportunity to complete interviews during evenings and weekends [126]. Accessibility and outreach to Hispanic/Latino communities should be emphasized, as often participation in clinical trials is not a priority to individuals living with dementia and their overworked and stressed caregivers [59 , 103].

Caregiver burden

Caregiver burden is a significant issue in AD/ADRD clinical research [127] and data show that 21% of caregivers are Hispanic/Latino compared to only 16.9% non-Hispanic White [128]. Due to health care inequality and socioeconomic hardships that predominantly affect Hispanic/Latino caregivers, these individuals often face unique and significant burdens that affect their likelihood and ability to enroll in clinical research. Many caregivers have inflexible work situations, financial constraints, and increased mental and physical health concerns, and Hispanic/Latino caregivers are more likely to experience these conditions than non-Hispanic Whites [128, 129]. When compared to non-Hispanic Whites, Hispanic/Latino caregivers spend more time directly caring for a loved one, with almost one-third of Hispanic/Latino caregivers providing care equivalent to full-time [128]. In addition, a plurality of Hispanic/Latino caregivers are the adult children of individuals living with AD/ADRD rather than spousal partners [122, 128]. Because Hispanic/Latino caregivers are more likely to be younger, this introduces additional burdens, including a higher likelihood to be balancing a full-time job as well as having to care for children under the age of 18 [122, 128]. A 2014 study found that Mexican American caregivers express worries about finances, health insurance, and balancing caregiving with other activities [59]. These burdens increase the logistical challenges faced by Hispanic/Latino caregivers as described above and reduce the likelihood of participation in clinical research.

Stringent study inclusion and exclusion criteria

Eligibility criteria are an integral component of clinical trials, ensuring participant safety and reducing factors that may confound results; exclusion criteria are used extensively in neurological treatment research and prevent about three in four individuals from participating in research [130, 131]. While study criteria are often necessary, research indicates that diverse populations are disproportionately excluded from clinical research, raising concerns about the external validity of treatments and research findings [130, 132]. Even the most common, seemingly innocuous, exclusion criteria, such as excluding participants with certain comorbidities, may unwittingly remove a greater number of Hispanic/Latino individuals compared to non-Hispanic Whites [93 , 133]. The criteria that can contribute to the exclusion of Hispanic/Latino participants in research into neurological disorders include language restrictions, cardiovascular diseases, physical disabilities, psychiatric conditions, cognitive impairments, and diabetes [1 , 134–137]. Further, the underdiagnosis of underserved populations compounds the exclusion of Hispanic/Latino individuals, as AD clinical trials require participants to have an official physician diagnosis of AD for entry [90, 138]. High exclusions rates among Hispanic/Latino populations generate ethical concerns over the criteria themselves and thus should only be used where there is a strong rationale for the exclusion [130]. More equitable, scientifically justified exclusion criteria can have a positive impact on recruitment into clinical research.

FACILITATORS TO HISPANIC/LATINO CLINICAL RESEARCH PARTICIPATION

Compared to the literature on barriers to Hispanic/Latino participation in AD/ADRD clinical trials, the literature on facilitators to participating in clinical research is much more limited. However, a few key motivators were identified in the literature (see Table 1b): a positive relationship with physicians, altruistic intentions to help one’s family and community, and the desire to increase health care knowledge and better one’s health. In addition, this section focuses on two key needs beyond creating well-tested messaging materials that are called for in the research: diversification of health care professionals and research staff and implementing broader community engagement efforts.

Positive relationship with health care providers

Positive patient-provider relationships can facilitate participation in AD/ADRD clinical research, as clinicians play an important role in informing their patients about clinical trials. The literature suggests many Hispanic/Latino individuals report that having a positive, communicative relationship with their health care providers can be a motivating factor for deciding to participate in clinical research [42 , 139–141]. One study found that 81% of those who identified as Hispanic/Latino said they would participate in a clinical trial if their physician made them aware of it [141]. From the same study, however, 67% of the Hispanic/Latino group reported that their physician had not spoken to them about medical research studies. In general, physicians are reluctant to refer their patients with chronic diseases or comorbid medical conditions to clinical trials [121, 142]. This hesitancy may decrease referrals for Hispanic/Latino populations, in particular, because they experience a higher likelihood of comorbidities, such as cardiovascular diseases, physical disabilities, and diabetes, when compared to non-Hispanic Whites [1 , 143]. Taken together, these studies highlight that many within the Hispanic/Latino community are willing to participate in clinical trials if they are adequately and appropriately communicated with about their potential options [3]. Fostering more positive patient-provider relationships could help address this gap [140]. The respondents of one study highlighted the need for strong patient–provider communication, with the need for providers to be patient and understanding and to allow the individual to feel heard and be given compassionate care. From these findings it is recommended that, due to the influential nature of patient–provider relationships, health care practitioners should be well-informed, rely on culturally competent sources for communicating about AD/ADRD clinical trial options, and foster positive relationships with their patients [140 , 145].

Altruistic intentions to help one’s family and community

Altruism—more specifically, altruism toward family members and the community—is a strong cultural value among Hispanic/Latino communities. There is some evidence that the effects of altruism may be a motivating factor for Hispanic/Latino individuals to participate in research if they believed it might benefit the health of their family members and others in their community [43 , 51]. In an early study by Calderón et al., Hispanic/Latino participants reported that a motivator for their participation in clinical trial research is how prevalent the disease is within their families and communities [89]. Similarly, a later study of Latina women found that they would be more willing to participate in breast cancer clinical trials if it would help someone in their family or community who had the cancer [54]. These findings highlight that emphasizing the altruistic components of research may potentially resonate with Hispanic/Latino populations, particularly among individuals who place a high value on family and community.

Involving family in medical decision-making

Familial roles in caregiving and health decision-making have been reported as deeply embedded in many Hispanic/Latino cultures [59 , 147]. A seminal paper by Sabogal et al. (1987) summarized that the Hispanic/Latino value of familism—a strong attachment, identification, and loyalty to one’s family—resulted in greater expectations of support and involvement of family members, nuclear and extended, in health care and decision-making [148]. While some research supports the importance of family-centered decision making within Hispanic/Latino cultures [62 , 150], other research indicates that familial influence might be more at play when health decisions are for persons who are older, have lower levels of acculturation, or have limited access to formal health care services [151]. Still, others have reported familism as stress inducing and exacerbating. Rosenthal Gelman (2010), for example, referred to the “myth” of extended family support in describing the experiences of Latino family caregivers of patients with AD; her qualitative study reported that caregivers experienced high levels of intrafamily disagreements and division around a family member’s diagnosis or treatments [61]. A subsequent study found that family disagreements increased Hispanic/Latino caregivers’ depressive symptoms, and that caregivers who reported stronger familism beliefs were more reactive to such disagreements [152]. Given the variability reported in the literature of the impact of familism on Hispanic/Latino health decision-making, outreach efforts should not assume that familism is a high value or a positive experience for participants. Rather, efforts to engage Hispanic/Latino individuals in research should be adaptable and allow for a range of family involvement, asking participants and caregivers their preference without making assumptions. Furthermore, researchers should aim to provide a mix of bilingual, culturally appropriate information/resources that are well-tested and that will help to inform and educate family members about AD/ADRD and what it means to participate in clinical research studies [63].

Desire to increase health care knowledge and better one’s health

The literature indicates that some in the Hispanic/Latino community may be motivated to participate in clinical research by the desire to increase their knowledge about AD/ADRD as well as other health care information [89 , 153]. In at least two studies, some Hispanic/Latino participants expressed that the opportunity to learn about AD/ADRD and receive information about clinical research in general through assessments played a role in their desire to participate [43, 153]. These participants were further motivated by the idea that participating in clinical trials may provide health benefits [43 , 51]. A focus group comprised of Mexican American participants found that if participants thought they would receive access to health care or medications, they would be motivated to participate in clinical research [44].

Diversification of health care professionals and study staff

At the forefront, the literature overwhelmingly emphasizes the need for hiring culturally competent physicians, study staff, and health care professionals with diverse cultural backgrounds [3 , 154–160]. Staff who are familiar with dementia and are culturally competent with the communities they serve, even if they are not bilingual, contribute to recruitment and retention efforts by being more relatable and familiar to potential participants [13 , 94]. Research demonstrates that matching staff with participants of similar cultural backgrounds and languages can foster trust and rapport, which improves accrual onto clinical trials [13 , 161–163]. While diversity in health care professions has been gradually increasing, indicating a promising trend toward a workforce that adequately reflects the population, there is still a substantial shortage of Hispanic/Latino professionals in highly skilled jobs [164, 165]. When last reported, research stated that Hispanic/Latino individuals comprised less than 3% of physicians, 1.5% of nurses, 5% of all medical school graduates, 4% of medical school faculty, and of the U.S. workforce in STEM fields, only 7% are Hispanic/Latino [166 –168]. These numbers show deep disparities in the health and science workforce, due in part to systemic barriers to entry, such as a lack of access to information, inadequate resources, lack of diverse mentors, and rising educational debt [169 –171]. However, several fields—including community health, social work, healthcare support, and personal care/service occupations—demonstrate that a diverse workforce can be realized where Hispanic/Latino professionals receive salary justice and recognition for their work [172 –174]. Though achieving diversity and better representation in the medical and public health workforce is a crucial component to recruitment and retainment of Hispanic/Latino participants in clinical trials, it cannot be assumed that Hispanic/Latino staff members will automatically be culturally proficient toward Hispanic/Latino research participants, who are a very diverse group, without sufficient diversity training and preparation.

Implementing broader community engagement efforts

One way that researchers can amplify their recruitment efforts is to engage in broader outreach activities with Hispanic/Latino communities [94]. Community engagement may be as important, if not more, than other outreach strategies used to recruit Hispanic/Latino participants, as one survey demonstrates that self-identified Hispanic/Latino Americans are more likely to be recruited by word-of-mouth than non-Hispanic White participants [175]. Moreover, older Hispanic/Latino individuals may be less likely to use health management websites, search the web for health information, or use technology for health-related purposes [176]. Outreach can take the form of partnerships with existing community organizations and groups or the provision of pro bono services that meet community needs, even beyond health-related topics. Partnerships and the provision of services can help researchers establish trusting relationships with the community and increase exposure to clinical research, which can make those in historically underserved communities, in particular, more likely to trust the studies that the partnerships sponsor [44 , 177].

Several studies demonstrated higher research participation rates among Hispanic/Latino communities when recruitment strategies were based on community models, such as community-partnered participatory research and practice-based research networks [177 –181]. In a study focused on recruiting Hispanic/Latino families into an intervention program, all participants indicated that their discussion with a community liaison was important in their decision to participate [182]. This supports the importance of strategies involving personal contact that can be aided by other strategies, such as mailings or flyers. Examples of potential partners include national and regional health organizations supporting Hispanics/Latinos, community advisory boards, promotoras, or even more informal cultural insiders who have a significant involvement in the community, such as community leaders [161 , 184]. Historically, promotoras have focused on disease prevention (e.g., immunizations, physical activity, cancer screening), but they have increasingly become integral in connecting underserved populations with health services [185, 186]. Research has shown that promotoras are a key component to success in health-related interventions and could be a resource for clinical trial recruitment [187, 188]. Partnerships with community leaders aid researchers through cultural understanding and insights into the community of interest, as well as increasing trust by participants [177].

Trial sites within the community can also facilitate the inclusion of some Hispanic/Latino populations by bridging the gap between possibly distant academic settings and underserved communities [189]. As discussed above, some Hispanic/Latino individuals may lack transportation to sites and research studies are not as readily available in underserved communities [11 , 94]. Community study sites can remedy these challenges by bringing clinical research into the community itself. Community engagement and the utilization of community study sites is an integral part of improving the recruitment of participants in Hispanic/Latino communities in AD/ADRD clinical research.

MESSAGING/COMMUNICATION CHANNELS FOR HISPANIC/LATINO CLINCIAL RESEARCH RECRUITMENT

When developing messages for Latino AD/ADRD clinical research recruitment, messages should be designed to be culturally relevant while simultaneously adhering to plain language guidelines [190]. Though the research specific to messaging development guidelines for Hispanic/Latino populations and AD/ADRD is limited, what exists indicates a need for message testing with Hispanic/Latino audiences to identify culturally acceptable and informative messaging to increase awareness around all aspects of AD/ADRD and clinical research (see Table 2).

Table 2

Messaging and communication considerations for Hispanic/Latino AD/ADRD research recruitment

Messaging/Communication Considerations
•Develop culturally relevant messages
•Use plain language, images, and examples
•Utilize channels and media proven to effectively reach Hispanic/Latino populations to communicate recruitment information
○Flyers
○Local radio and newspaper advertisements
○Social media
○Telenovelas and videos

Develop culturally relevant messages

Culturally relevant message development is a critical component to effective communication with many Hispanic/Latino populations. Culturally relevant messaging refers to developing messages for specific audiences based on group-level cultural characteristics (e.g., values, norms, behaviors, beliefs, attitudes). The fields of health communication and social marketing provide several strategies to develop culturally appropriate and relevant messages, with the predominant principle requiring engagement with persons in the intended audience groups (e.g., Hispanic/Latino caregivers) at all development stages to listen to their needs, concerns, and interests and then create and test materials iteratively until they are acceptable and motivating to the respective audience [191 –194]. The goal is to ensure that both the English- and Spanish-language materials are aligned with the diversity of Hispanic/Latino cultural values and norms, and consequently are effective at recruiting Hispanic/Latino participants into AD/ADRD research [70, 195], such as the importance of family interdependence in making medical decisions and having high regard for their elders [146, 147].

Use plain language, images, and examples

Using plain language, images, and examples to facilitate consumers’ comprehension is important in the development of messages and communication materials [196]. Although there is not a standard reading level for health materials, the Joint Commission—a leading health care accreditation organization—recommends that materials should be written at a fifth-grade reading level [197]. Writing messages at an appropriate reading level may be especially important for Hispanic/Latino audiences, given the wide range of educational backgrounds, geographic locations, socioeconomic statuses, and preferred language (English versus Spanish) among the Hispanic/Latino population [91 , 199]. Additionally, health messages that are supplemented by images and examples can facilitate consumers’ understanding and comprehension of information. Research on clinical research recruitment has shown that simplifying highly technical information, providing examples, and substituting scientific language may lead to increased participation among underserved populations [200].

Utilize channels and media for communicating recruitment information to Hispanic/Latino populations

Communicating clinical trial recruitment information can occur through different channels and media, each with their own benefits and drawbacks. A variety of channels—flyers, local radio and newspaper advertisements, social media, telenovelas, and videos—are used in clinical research recruitment with different levels of effectiveness. Using channels and messaging that have been proven to effectively reach diverse communities facilitates successful recruitment of Hispanic/Latino participants and other underrepresented populations [94]. Similar to research on developing messages, much of the extant research on channels and mediums is not specific to Hispanic/Latino populations and AD/ADRD, indicating that additional information about appropriate and effective channels for communicating with this audience should be gathered during audience testing.

Flyers

Many researchers use flyers as a recruitment communication tool, but research on the effectiveness of flyers in clinical research recruitment has found mixed results. The benefits of using flyers are that they can be low cost and easy to post in a variety of relevant settings, such as in clinic waiting rooms, hospitals, and community settings [147, 201]. Despite these advantages, studies have found that flyers recruit fewer participants compared to other recruitment strategies [162, 202]. A study that specifically examined recruitment strategies among Mexican Americans found that responses to flyers alone were lower compared to community-based recruitment efforts [147]. However, flyers can be important ancillary resources for conducting in-person recruitment. Recruiters found that flyers are useful as handouts to facilitate conversations and provide potential participants with study information that can be shared with family members and friends [147, 177]. Similar findings have been noted across other health fields (e.g., smoking cessation, weight gain prevention) [203, 204]. This evidence suggests that the effects of flyers can be amplified when they are used to supplement in-person, community-based recruitment methods.

Local radio and newspaper advertisements

The use of local radio and newspaper advertisements has demonstrated mixed results as strategic recruitment media channels. Although proponents of these media cite that radio and newspaper advertisements can effectively reach niche audiences by matching the known interests of audiences (i.e., styles of music, writing content), these ads typically have low response rates and result in more ineligible screens [131, 147]. A study recruiting Mexican Americans in central and south Texas using a Spanish-speaking radio station and bilingual newspaper failed to recruit a single eligible participant after running these advertisements for several weeks [147]. Additionally, although some radio stations regard research recruitment advertisements as public service announcements and may offer discounts to researchers, many radio and newspaper advertisements are expensive [147]. Conversely, a study of men at high risk for developing diabetes used numerous recruitment channels and mediums (e.g., mainstream media- television, newspaper, radio, mail-outs, posters, social media, and online promotions by community organizations) and found that the most effective form of recruitment was radio advertising [205]. Nearly half of the participants (42%) for this study (N = 1,007) were recruited via radio advertising. These findings suggest that radio and newspaper advertisements have mixed results in effective recruitment strategies and warrant further research to understand what makes recruiting through these mediums most effective.

Social media

As previously discussed, many older Hispanic/Latino communities are more likely to be responsive to word-of-mouth and community engagement methods of recruitment and less likely to utilize technology to gather health information [175, 176]. Though a recent survey from Pew Research Center reported that Hispanic/Latino adults are less likely than non-Hispanic White adults to own a computer or have high-speed internet at home [206], emerging evidence and trends in media usage suggest that for those with internet access, the web may be an increasingly effective method to increase awareness of clinical trials and recruit underrepresented groups [42]. As well, Hispanic/Latino internet users are increasingly using social media, with many on Facebook (69%), YouTube (78%), Instagram (51%), and Snapchat (29%). Several studies have shown that Facebook advertising can be successful in increasing diversity in engagement with information about clinical trials [206 –208]. One study created social media advertisements to recruit English, Spanish, and Korean cancer survivors and found that Spanish-speaking, self-identified “Latinx” participants engaged by clicking on the ads to learn more information (984 clicks), and they more frequently clicked on ads compared to English speakers (420 clicks) [208]. An important consideration for any advertisement mode is cost, and there is some evidence that focused social media advertisements for conducting health research can be low cost [209]. For example, the average cost per unique ad click among Latinx participants in the cancer survivor study was $0.31 [208]. While these findings indicate social media is a promising avenue for Hispanic/Latino recruitment, research into this medium is still in its infancy, and more research is needed to determine the efficacy of social media as a recruitment tool [210, 211].

Telenovelas and videos

Another medium for recruiting Hispanic/Latino individuals is telenovelas and videos. Telenovelas, or dramatized televised stories, are a popular source of entertainment and modality of communication with some in Hispanic/Latino communities (e.g., diabetes educational programs, materials aimed at older Hispanic/Latino participants) [212, 213]. Researchers at Stanford’s Alzheimer’s Disease Research Center (ADRC) created a short video featuring a promotora—a lay health worker who works in Spanish-speaking communities—engaging with an AD/ADRD caregiver to promote awareness of the early signs of dementia. An evaluation of the video’s effectiveness demonstrated an increased likelihood among community members to have discussions about dementia with their family and friends [13]. Another study that evaluated different outreach efforts found that media broadcast was an effective method of recruitment for Hispanic/Latino participants [177]. Additionally, compared to print materials, videos are better able to circumvent literacy issues and can be used as supplementary recruitment materials for individuals with limited English proficiency [214, 215].

CONCLUSION

AD/ADRD clinical studies have long struggled with adequate representation of diverse and underserved communities. Underrepresentation undermines researchers’ abilities to understand how ethnicity and cultural factors interact with genetic and environmental factors related to AD/ADRD, rendering the quest for effective treatments and prevention strategies in adequate for large segments of the population. This literature review provides an updated narrative overview of the current landscape of Hispanic/Latino participation in clinical research, including the challenges, facilitators, and communication channels to conduct culturally appropriate outreach efforts to increase awareness and participation of Hispanics/Latinos in AD/ADRD clinical research studies. It also emphasizes that any effort to address the disparities gap among Hispanic/Latinos must first recognize the heterogeneity of the individuals who make up the group, and then, tailor outreach activities and programs to address the diverse needs and circumstances.

The literature review presented in this paper has its limitations. First, we chose to conduct a narrative review, rather than a systematic review, to gain a broader, contextual understanding of the factors influencing Hispanics’/Latinos’ participation in AD/ADRD clinical research. A narrative review, however, has a greater risk for selection bias by increasing the probability of not including all pertinent literature or overemphasizing select articles. To minimize these effects, we conducted multiple search queries with varying search terms and had multiple analysts review each source. Future efforts should consider a systematic literature review, though it would involve substantially narrowing the sample to address a specific research question. Second, many AD/ADRD studies we reviewed reported aggregated data across Hispanic/Latino subgroups or only focused on one specific nationality group, which limits the generalizability of their findings. To address this, our review focused on identifying patterns or themes reported across multiple sources. Last, many articles cited in this review had a tendency to report barriers in a manner that placed the onus of responsibility/change on Hispanic/Latino individuals, without sufficiently discussing the roles of sponsors or researchers in creating, maintaining, or addressing such barriers. To address this concern, we aimed to provide a perspective that included a discussion of the systemic inequities that perpetuate the reported barriers.

There are several systemic challenges that impede the recruitment of Hispanic/Latino participants into AD/ADRD clinical studies, with many centered around limited access to enrollment opportunities and logistical barriers: AD/ADRD studies are not readily available in underserved communities; eligibility criteria can disproportionately exclude Hispanic/Latino individuals from participation; culturally appropriate and bilingual information about trials can be lacking; staffing at clinical research sites do not readily represent participants’ culture and language; and discrimination or fear of risking one’s immigration status. Despite these challenges, the literature indicates that when made aware of trials, many Hispanic/Latino individuals may express similar interest as non-Hispanic Whites, particularly when studies are locally accessible and cultural norms and language differences are addressed.

Understanding factors that may disproportionately affect Hispanic/Latino populations within the clinical research environment is just one step among many to begin to close the disparity gap described in this paper. Applying the CTTI recommendations, noted earlier, would be a critical step in addressing the challenges and barriers many Hispanic/Latino populations face in clinical study participation. Based on those recommendations, a concerted effort is needed to analyze the AD/ADRD trial design and protocol development processes in the context of the intended participants, including a review of eligibility criteria and language requirements [5, 94] and the selection of neurocognitive tests that are culturally and linguistically valid [216]. In their editorial, Addressing Health Disparities Among Minority Populations: Why Clinical Trial Recruitment Is Not Enough, Wilkins, Schindler, and Morris (2020) advocate that AD/ADRD clinical trial investigators must factor in social determinants of health into their hypothesis generation and study design to improve representative recruitment, including a multidisciplinary approach with social scientists and individuals experienced with working with underserved communities [5]. CTTI also recommends an assessment of trial feasibility and site selection early on prior to activating a trial. According to Heller et al. (2014), who conducted a systematic review of clinical trial interventions to increase diverse representation, the most successful studies were those that emphasized recruitment planning, including input from the study sites, before completing their study protocol design [94]. Yet, Gilmore-Bykovskyi et al. (2019) found that early recruitment planning for underrepresented populations within AD trials was rare, with only one study of 22 reviewed in their analysis documenting a prospective recruitment intervention. In addition, they found that most of the studies reviewed generally lacked strategies that incorporate local and community contexts [3]. Among Hispanic/Latino populations, trial feasibility and site selection will need to consider logistics, including providing appointment times that can accommodate challenges such as inflexible work schedules and family obligations and opening sites within Latino communities and with Spanish-speaking staff, among others. Finally, CTTI highlights the critical importance of communication in the recruitment process. Among Hispanic/Latino populations that includes having culturally appropriate information about the trial in both English and Spanish and ensuring that the participants’ families have the ability to engage with the research team should that be the preference.

Engaging with and including Hispanic/Latino participants in AD/ADRD clinical research studies is essential both scientifically and ethically. The National Institutes of Health Revitalization Act of 1993 recognized the importance of ensuring that trials are “designed and carried out in a manner sufficient to provide for valid analysis of whether the variables being studied in the trial” [8]. AD/ADRD disproportionately affects Hispanic/Latino individuals—not ensuring their inclusion in trials is unethical as it reduces the ability to generalize study findings and treatments across population traits. Furthermore, Hispanic/Latino individuals currently represent 18% of the U.S. population and this number is expected to grow to 30% by 2050 [217]; therefore, it is an ethical and fiduciary obligation that Hispanic/Latino populations are included in AD/ADRD research.

To conclude this paper, we bring the conversation back to Gallagher-Thompson et al., who in their 2003 article identified key barriers to the recruitment and retention of Hispanic/Latino caregivers in AD/ADRD research, including: lack of access and availability of services, lack of education about AD/ADRD and related research, language barriers, time constraints, and cultural factors. Our review, which focused on literature published over the past decade, found these same challenges and more; demonstrating that progress toward ameliorating the hurdles have either been insufficient or unsuccessful.

To better realize the longstanding failures to improve engagement and interest among Hispanics/Latinos in AD/ADRD research, we need only to look at the experiences and lessons learned from the COVID-19 pandemic. Gilmore-Bykovskyi, Jackson, and Wilkins (2020) provide an excellent summary of the injustices around the inequitable representation of diverse populations in clinical research, highlighted by the enormous disparities gap posed by COVID-19 among non-White communities [36, 101]. They succinctly state, “Despite good intentions, we propagate and maintain a system where non-white populations bear the burden of disease but do not reap the benefits of research advances” (p. 97). Many of the same barriers that have existed in clinical research have been magnified by COVID-19, including limited access to linguistically and culturally competent COVID-19 information and participation in SARSCoV-2 trials, indicating the structural nature of these challenges [218 –221]. Though the NIH published policies and guidelines on the inclusion of women and minorities in clinical research in 1993 [8], studies indicate little oversight or accountability to their compliance [222]. COVID-19 also appears to have solidified the need for greater commitment by NIH. Dr. Francis Collins, the NIH Director, provided a public apology to the biomedical research enterprise who “have endured disadvantages due to structural racism”, and announced an NIH commitment through a new initiative, UNITE, to address structural racism by instituting new ways to support diversity, equity, and inclusion across the NIH, its stakeholders, and its extramural research ecosystem [223, 224].

Building a research enterprise that incorporates the challenge and barriers to participation for Hispanic/Latino populations, and all underrepresented groups, will require new and innovative ways to develop research studies from hypothesis generation to inclusive research protocols and community engagement and participation. While these efforts take time, effort, and resources, it is imperative that the research community build these bridges so that future AD/ADRD treatments and prevention strategies work for all people.

Footnotes

ACKNOWLEDGMENTS

There was no external funding for this project. The authors are full-time federal employees or federal contractors paid by the National Institute on Aging of the National Institutes of Health.

Authors’ disclosures available online ().

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