Challenges in studying disparities in neuropsychiatric hyperkinetic movement disorders

Abstract

Purpose of review

The purpose of this review is to highlight challenges in studying disparities in neuropsychiatric hyperkinetic movement disorders, specifically Tourette syndrome and Huntington’s disease.

Recent findings

We highlight racial and ethnic disparities in understudied movement disorders, particularly the neuropsychiatric hyperkinetic movement disorders, Tourette syndrome and Huntington’s disease. These diagnoses are likely under-recognized and under-diagnosed in racial and ethnic minority groups, leading to disparities in access to subspecialty care and treatment. Factors contributing to disparities are complex and likely include patient mistrust of the medical community, stigma, and structural racism. Application of health disparities research frameworks used in other disciplines may have utility in the study of inequities in neurology.

Summary

There are significant challenges in studying disparities in Tourette syndrome and Huntington’s disease. We also highlight frameworks used in neurology as well as recommendations from the National Institute of Neurological Disorders and Stroke around training in health disparities and recommendations in reducing disparities in neurological disorders across the life span.

INTRODUCTION

Racial/ethnic disparities in access to neurological care, the quality of care received, and outcomes for common neurological disorders are well documented [1–9]. Disparities in neuropsychiatric hyperkinetic movement disorders specifically – Tourette syndrome (TS) and Huntington’s disease (HD) – have been the subject of far less study [10]. Although low disease prevalence may partially explain this limited interest, we believe an agnostic attitude to the existence of these disorders in minoritized communities, or the thinking that these disorders are nonexistent in minoritized communities, has contributed to this limited study of these disparities. Two of us are movement disorder specialists studying health disparities (in TS [M.E.D.] and HD [A.M.]) and draw on our experiences to describe challenges for the field in studying disparities in neuropsychiatric hyperkinetic movement disorders.

CURRENT ESTIMATES OF RACIAL AND ETHNIC DISPARITIES IN TOURETTE SYNDROME AND HUNTINGTON’S DISEASE

There are approximately 350–400 000 children and adults with TS in the United States (US) [11]. TS is often accompanied by neuropsychiatric comorbidities, with attention deficit hyperactivity disorder and obsessive compulsive disorder being the most common comorbidities [12,13]. The comorbidities can be more debilitating than the tics themselves. Delayed diagnosis or misdiagnosis of TS also placed individuals at risk for under-recognition or underdiagnosis of comorbidities, which can lead to a cascade of negative outcomes, including impaired school performance and lower quality of life.

The number of children and adults with HD in the US is smaller by an order of magnitude, about 40 000 [14]. HD was previously thought to be more common among White people compared with Black people [15], but more recent studies suggest this is not the case. A recent analysis of US claims data from 67 million individuals with private health insurance reported that the rate of new HD diagnoses for Black patients was 7.38/100 000 compared to 7.76/100 000 among White non-Latino patients, and 4.34/100 000 among Latino patients [16]. In an analysis of national Medicare claims data, the prevalence of HD was 15.1/100 000 Black Medicare beneficiaries, 13.0/100 000 White beneficiaries, and 11.7/100 000 among beneficiaries of other racial/ethnic groups (Asian, Latino, American Indian, unknown); incidence rates followed roughly similar patterns [17]. The same study included an analysis of Medicaid claims data from 17 states and found a prevalence of 21.6/100 000 among White insureds, 8.1/100 000 among Black insureds, and 11.5/100 000 among insureds of Asian, Latino, American Indian, and/or unknown racial/ethnic descent [17]. These findings suggest that HD prevalence is greater, and HD incidence is similar, among Black people than has been typically described.

LIMITATIONS OF THE PRESENT LITERATURE

Newer estimates suggest a higher overall disorder prevalence for TS [11] and HD, but there are limitations of these datasets. In HD, there may be challenges with claims data to estimate the prevalence in some communities, such as the Latino community. There is a suggestion that HD is less prevalent among Latino people compared to White people. In HD, these findings may not be representative of the diversity seen at individual centers of excellence. One of us (A.M.) sees adult and pediatric HD patients at UCLA’s Huntington’s Disease Society of America (HDSA) Center of Excellence (COE). On 2021 data pull of all HD patients ever seen at UCLA’s HDSA COE, 72 out of 346 patients (21%) were Latino. Furthermore, the largest epidemiologic dataset for HD (Eroll-HD) contains only 10% non-White/non-Hispanic patients [18], yet this study mostly takes place at COEs and does not capture patients seen in safety net hospitals, federally qualified health centers, and nonacademic clinics and institutions.

Existing TS registries have been based primarily on patient samples from urban academic centers and have relied on patient-reported diagnoses that often group tic disorders into a single category. Race and ethnicity may not be well captured in these registries [19–22]. In a highly curated and well phenotyped dataset of people with TS recruited for genetics research, the participants were highly educated and predominantly White, which made it challenging to estimate the extent of racial/ethnic disparities in the population and limited our ability to draw firm conclusions [23^■]. In clinical settings, one of us (M.E.D.) sees child and adolescent patients with tic disorders at the Mass General Brigham (MGB) TS COE; out of 393 pediatric patients seen at the TS COE between 2015 and 2021, 4 (1%) were Black and 9 (2.6%) were Latino. Other studies have reported lower prevalence of White individuals with TS than we have observed in the MGB TS COE pediatric population [20,24]. There may be a disparity at the individual level or other factors contributing to low prevalence of non-White patients with TS; we are currently examining factors contributing to these possible disparities.

THE CHALLENGE OF STUDYING DISPARITIES IN NEUROPSYCHIATRIC HYPERKINETIC MOVEMENT DISORDERS

Two of us (M.E.D. and A.M.) are junior physician-scientists studying racial/ethnic disparities in neuropsychiatric hyperkinetic movement disorders. We often face skepticism when we state our interests. The first question we frequently encounter is: “Do Black or Latino people have TS?” (or, “Do Black or Latino people have HD?”). This question, in and of itself, identifies significant methodological challenges in studying racial/ethnic disparities in the prevalence of these disorders: what proportion of Black and Latino patients with TS/HD are actually diagnosed with TS/HD?

Are there other factors that might contribute to their underrepresentation in clinical samples? One possibility is that Black and Latino people are misdiagnosed as having no TS/HD or as having other neuropsychiatric conditions. Another possibility is that Black and Latino are appropriately diagnosed but have worse access to care (i.e., to specialty clinics and COEs), resulting in their exclusion from spaces where study participants are recruited. The complexities of TS/HD care necessitates multidisciplinary care from neurology, psychiatry, and psychology experts [25,26]. Yet, this level of specialized care is often restricted to urban COEs [25,26]. Data from Enroll-HD suggests that Black patients with HD are diagnosed with HD (after the onset of symptoms) one year later than non-Latino White patients [27]. Disease severity at baseline was accordingly elevated among Black participants in the cohort [18].

Based on our experiences, and the experiences of our colleagues of color, in both undergraduate and graduate medical education, images and videos of patients with these disorders rarely portray people of color. Also in our experience, the fact that the gene for HD was discovered through the efforts of a decades-long longitudinal epidemiological study of a community in Lake Maracaibo, Venezuela [28] was not included in our medical school or residency HD lectures. The failure to recognize that these disorders can also affect our Black and Latino patients leads to delays in referral from primary care to specialty neurologic care, or from specialty neurologic care to movement disorders subspecialty care. These delays in disorder recognition are compounded by known challenges in access to neurologic services [1,4,5,8,9]. Even if Black and Latino patients are referred to specialty or subspecialty care and they can overcome structural barriers in accessing specialty or subspecialty care, clinicians in these fields may still not consider the possibility of these diagnoses because of the erroneous belief that “TS [or HD] is a White disorder.” Accurate data about the incidence and prevalence of these disorders among our Black and Latino patients will be pivotal to improving early diagnosis, patient education, and associated treatment.

In addition to barriers of access and disorder recognition, patients may also have reasons to delay seeking care. The US medical system has a history of disenfranchising communities of color through systemic racism, unethical experimentation, and lack of diversity in the field, with concomitant impacts on public health [29]. Even when Black and Latino patients are able to access the medical system, they experience innumerable micro and macro aggressions that may dissuade them from continuing to seek medical care [30]. Patients may also want to hide their symptoms or avoid a diagnosis due to the associated stigma attached to carrying an incurable neurological condition. People with TS face social stigma, social isolation, and higher bullying rates [31]. There is a long history of stigmatizing HD, primarily rooted in eugenic views, by the medical community [32]. As a result, many people with symptoms suggestive of HD or whose family histories place them at risk of developing HD choose to avoid genetic testing out of fear of losing health insurance, employment, or being treated differently by friends and families [33]; or out of fear of not knowing what to do with the information gained [34]. Although not well studied in communities of color, knowing the negative impact that race-based medicine has had in Black and Latino communities, compounded by the specific features of this genetic condition that has also stigmatized families, leads us to believe that historically disenfranchised communities may not seek timely diagnosis, counseling, or treatment.

Indeed, these challenges with appropriate recognition and diagnosis have led to our interest in studying health disparities in these disorders. Due to the relative rarity of these disorders, proposed studies are frequently challenged on the grounds that they may not be sufficiently powered to identify disparities. These challenges may generate publication biases with unpredictable effects [35]. It is possible that the large studies that dominate the published literature may not yield statistically significant differences in outcomes due to the small number of people of color included in these studies and therefore generate inaccurate estimates of disparities. It is also possible that the published literature is missing important smaller studies from underrepresented geographical regions or types of healthcare settings, resulting in underestimates of disparities. While many reviewers may recognize the need to avoid specifying White Non-Latino patients as the reference group, other reviewers continue to ask for comparisons to White Non-Latino groups, which is again challenging for disorders with low overall prevalence and even lower prevalence in minoritized groups.

OUR RECOMMENDATIONS AND HIGHLIGHTED FRAMEWORKS TO SUPPORT HEALTH DISPARITIES RESEARCH IN NEUROPSYCHIATRIC HYPERKINETIC MOVEMENT DISORDERS

Different frameworks exist in studying disparities and have been applied broadly across disciplines. In neurology, the social-ecological model [36] and the National Institute of Minority Health and Health Disparities (NIMHD) Research Framework [37^■,38–41] have been applied or suggested in studying disparities across neurologic disciplines, but not specifically in TS or HD. The NIMHD Research Framework assesses disparities across domains of influence (i.e., biological, behavioral, physical environment, socio-cultural environment, healthcare system) across the individual, interpersonal, community, and societal levels [41]. In addition, the National Institute of Neurological Disorders and Stroke (NINDS), recognizing the burden of neurologic disorders, disparities, and importance of health equity in neurologic disorders, also has provided recommendations not only in training in health disparities and in training individuals from historically under-represented backgrounds, but also in addressing and improving health equity in neurologic disorders across the life span [42,43^■■].

Given our current challenges, we provide a broad set of recommendations using the NIMHD framework for supporting work in this area across individual, interpersonal, community, and societal levels (Table 1). While there are many systematic challenges to recognizing, understanding, and studying rare neuropsychiatric hyperkinetic movement disorders in historically disenfranchised communities, we aim for this framework to guide investigators and institutions in improving our understanding of neuropsychiatric hyperkinetic movement disorders in purposefully forgotten populations.

Table 1.

Recommendations for studying disparities in neuropsychiatric hyperkinetic movement disorders within the healthcare system domain

Level of influence	Recommendations
Individual (patient)	Study disorder prevalence in minoritized communities. Consider the use of national claims datasets that do not rely on patients overcoming barriers to access specialized neurologic care. If available, consider large, multicenter, disorder-specific datasets.
Interpersonal (physician researchers)	Collect primary data at an individual center with, at minimum, variables for race, ethnicity, gender, preferred language, insurance payer, level of education, household income, food insecurity, geographical location, access to public transportation, access to Internet, literacy, and caregiver support. In addition to individual-level variables, disease-specific variables should be obtained. Attend scientific conferences to disseminate their work and identify potential collaborators at a national and international level. Build multicenter collaborations, particularly for disorders that do not have a robust disorder network. Create community partnerships with patients, patient advocacy groups, and clinics caring for underserved communities. Create appropriate systems for disorder-specific and sociodemographic data collection across different healthcare settings (e.g., centralized RedCap data registry).
Community (health system)	Given known barriers in access to neurologic care, consider studying the disorder outside of centers of excellence and academic medical centers. Other places of usual neurologic care for underserved patients may include federally qualified health centers, safety net hospitals including county hospital systems, and the Veterans Administration Health System. Improve clinical access to subspecialized care for individuals who are uninsured, minimally insured, or those who rely on public insurance payers such as Medicaid/Medicare.
Societal (institutional support nationally)	Improve data collection of race, ethnicity, and social/structural determinants of health across centers of excellence. Leverage existing disorder networks to understand disorder prevalence and sociodemographic characteristics of patients. If disorder networks are not available, consider curating center-specific data by pairing clinical data with sociodemographic data (e.g., race, ethnicity, sex, gender, preferred language). We recognize that enabling the collection of better data (and, in particular, disease-specific variables) will require additional infrastructure support. For example, a social worker may be needed if a patient reports suicidal ideation – psychiatric comorbidities are disproportionately present among individuals with HD and TS. Encourage pro-bono work for health disparities researchers engaging with marginalized communities. Incentives could be employed rather than strictly focusing on RVU generation alone, given the complex needs of individuals with neuropsychiatric movement disorders like TS and HD, and other hyperkinetic movement disorders [45]. Protect the time of subspecialists to provide clinical care in underserved communities. Acknowledge the inherent challenges in studying health disparities in neuropsychiatric hyperkinetic movement disorders. Investigators may rely on qualitative and longitudinal studies, which may lead to less publications in earlier years as they collect primary data, build partnerships, and engage with the community.

For researchers interested in studying health disparities in neuropsychiatric hyperkinetic movement disorders, reliance on large datasets may offer opportunities to identify and study disorders without access to patients being seen in specialized centers. Analyses of large disorder-specific datasets and individual center data can inform differences in access to care, disorder management, and outcomes. Understanding healthcare access disparities might require qualitative studies focused on understanding how minoritized patients access their current care. In addition, community partnerships with clinics in underserved areas may be needed to obtain the perspectives of patients who do not have access to specialized centers. Investigators should consider partnering with research and advocacy foundations for disorders like TS and HD.

We also provide recommendations for institutions at the societal level (Table 1). As previously described, some of the biases in academia and the publication and grant review process may make it more challenging for investigators to study health disparities for less common hyperkinetic neuropsychiatric disorders. We suggest academic institutions provide protected time and salary support for investigators to engage in this work. Both of us (M.E.D. and A.M.) would not have been able to engage in our current research without departmental (i.e., protected research time and salary support) and foundation support. Given the challenges of potential misdiagnosis and limited access to neurologic care, we recommend institutions provide protected time, resources, and additional remuneration to subspecialists. The early salary support and startup investment will be of significant value to investigators who may have fewer publications early on as they build community partnerships, identify multicenter collaborations, and engage in longitudinal data collection. The institutional support can also attract more trainees to these subspecialties, who, if appropriately allocated to underserved areas, can ultimately increase access to subspecialized care for minoritized populations.

CONCLUSION

There are currently many unanswered questions. The true prevalence of TS/HD in underrepresented minoritized groups is unknown. It will be important to understand: what we can do to increase the trust of underrepresented minoritized patients, additional barriers to accessing specialty and subspecialty care, how academic institutions can meaningfully support healthcare disparities researchers, and healthcare policies and interventions needed to improve access to specialty care. Given the change in the current clinical research landscape, there is more interest in collecting social and structural determinants of health and not only identifying disparities but also implementing interventions to eliminate disparities. Training more health services researchers from diverse backgrounds is also needed [42,43^■■,44]. Finally, it is important to have an equity lens integrated at all levels [46^■■].

KEY POINTS.

• Racial and ethnic disparities exist in neuropsychiatric hyperkinetic movement disorders such as Tourette Syndrome and Huntington’s disease.

• Challenges exist in studying health disparities in both Tourette Syndrome and Huntington’s disease.

• Frameworks for studying disparities and supporting health services researchers can help target areas for interventions for equitable care for patients with neuropsychiatric hyperkinetic movement disorders.