Abstract
Background:
To examine the association between race, ethnicity, and parental educational attainment on tic-related outcomes among Tourette Syndrome (TS) participants in the Tourette Association of America International Consortium for Genetics database.
Methods:
723 participants in the TAAICG dataset aged ≤ 21 years were included. The relationships between tic-related outcomes and race and ethnicity were examined using linear and logistic regressions. Parametric and non-parametric tests were performed to examine the association between parental educational attainment and tic-related outcomes.
Results:
Race and ethnicity were collapsed as Non-Hispanic white (N=566, 88.0%) versus Other (N=77, 12.0%). Tic symptom onset was earlier by 1.1 years (p<0.0001) and TS diagnosis age was earlier by 0.9 years (p=0.0045) in the Other group (vs. Non-Hispanic white). Sex and parental education as covariates did not contribute to the differences observed in TS diagnosis age. There were no significant group differences observed across the tic-related outcomes in parental education variable.
Discussion:
Our study was limited by the low number of non-white or Hispanic individuals in the cohort. Racial and ethnic minority groups experienced an earlier age of TS diagnosis than Non-Hispanic white individuals. Tic severity did not differ between the two groups, and parental educational attainment did not affect tic-related outcomes. There remain significant disparities and gaps in knowledge regarding TS and associated comorbid conditions. Our study suggests the need for more proactive steps to engage individuals with tic disorders from all racial and ethnic minority groups to participate in research studies.
Keywords: Tourette Syndrome, disparities, race, ethnicity, social determinants of health
Introduction
Tourette Syndrome (TS) is a relatively common neurodevelopmental disorder characterized by chronic motor and vocal tics.1 It is frequently associated with high rates of co-occurring neuropsychiatric conditions, most prominently attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD).1 The population prevalence of TS is approximately 0.6%2, and has been described in all racial and ethnic groups worldwide.3–11 Although prevalence patterns across racial and ethnic groups have not been extensively studied, at least two studies from the United States have found racial and ethnic disparities in TS diagnoses where Black and Non-Hispanic children are less likely to receive a diagnosis of TS compared to white Non-Hispanic children.12,13 One study found similar rates of TS diagnosis between Hispanic and Non-Hispanic children. However, the sparsity of data in that study limited the extent to which conclusions could be drawn about other racial and ethnic groups.14 Meta-analyses indicate no significant differences in TS prevalence rates by geographical region.2,15
In addition to disparities in the diagnosis of TS, studies have also found disparities related to socioeconomic status and insurance status. Among affected adults with persistent TS, tic severity is correlated with unemployment and disadvantaged socioeconomic status.16 For those diagnosed with TS, severity is greater among children on public insurance with higher rates of neuropsychiatric comorbidities (vs. private).13 Furthermore, children with TS and co-occurring neuropsychiatric conditions are less likely to have a medical home defined as a comprehensive family/patient centered and coordinated primary care center (vs. without TS).17,18
Racial and ethnic differences (at times likely due to racial and ethnic disparities) have also been observed in commonly occurring comorbidities observed in TS. For example, Black and Hispanic children are less likely to be diagnosed with ADHD and are more likely to experience undertreatment compared to white children.19 There is less known about racial and ethnic disparities in OCD.20
Disparities such as delayed diagnosis, delay in treatment, underdiagnosis, and treatment failure are well-documented in other neurologic conditions. For example, African Americans with Parkinson’s disease (PD) are more likely to have delays in diagnosis and treatment (including deep brain stimulation) compared to white individuals with PD.21–23 In pediatric epilepsy, Hispanic patients are less likely to achieve seizure freedom than white non-Hispanic patients.24 In autism spectrum disorder, racial and ethnic disparities have led to increased challenges with accessing specialty care.25
In this present study, our goal was to examine possible delays in care of individuals with TS from racial and ethnic minority groups by examining the relationship between race, ethnicity, parental education, and tic-related outcomes of individuals with TS, including TS age of symptom onset, TS age at diagnosis, time-to-TS-diagnosis, tic severity measures, rates of comorbid conditions (i.e., ADHD and/or OCD), and the number of medications taken in a large clinical dataset collected by the Tourette Association of America International Consortium for Genetics (TAAICG). Based on disparities described in common co-occurring conditions in TS and other neurologic conditions, we hypothesized that individuals from racial and ethnic minority groups would have a delayed diagnosis of TS and more severe disease compared to non-minority groups. Based on disparities described in pediatric neurologic conditions and associations with socioeconomic status such as parental educational attainment,26 we also hypothesized that individuals whose parents have higher educational attainment would have an earlier diagnosis of TS and less severe disease than individuals whose parents have lower parental educational attainment.
Methods
Study population
We examined a research dataset of individuals with TS and their family members collected by the TAAICG for an NIH-funded genetic study.27,28 The Massachusetts General Brigham institutional review board approved all aspects of this work. The TAAICG dataset was collected as part of a larger genetics study conducted at tic disorder clinics in North America and Europe and through the Tourette Association of America (TAA) and is a well-characterized dataset of individuals with TS and co-occurring conditions.
Participants with a DSM-III-R or DSM-IV-TR diagnosis of TS were eligible for participation. Individuals with intellectual disability, another primary neurologic disorder, a known genetic syndrome, or tardive tics were excluded. All participants received detailed phenotypic assessments for tics, ADHD, and OCD using a structured clinical interview and validated scales such as the Yale Global Tic Severity Scale as described previously.27,28 Participants of European ancestry were specifically recruited for the parent genetics study, and are thus over-represented in the sample.
Demographic and socioeconomic measures included subjects’ self-reported age at the time of the interview (years); biological sex assigned at birth (male, female); race (white, Black, American Indian, Asian, Native Hawaiian, or More than one race); ethnicity (Non-Hispanic, Hispanic); and highest maternal and paternal education level attained (Under 7 years of schooling, Partial High School, High School, 2-Year College Degree, 4-year College Degree, Graduate/Professional Degree). Due to the small number of individuals from racial (7.4%) and ethnic (5.8%) minority groups in the cohort, race and ethnicity were collapsed for higher statistical power as Non-Hispanic white versus Other (Hispanic white, Black, American Indian, Asian, Native Hawaiian, More than one race). Individuals who only answered either race or ethnicity but not both (for example answering Black for race, but leaving ethnicity blank), were coded as Other. Individuals identifying as white but missing ethnicity were excluded. Race and ethnicity information was available on probands only. According to the highest parental education levels, education was collapsed into three mutually exclusive categories: 1) Both parents with less than a college degree, 2) At least one parent with a college degree or higher, and 3) Both parents with a college degree or higher. A college degree was defined as having achieved a 4-year college degree. We restricted analyses to individuals aged 4 to 21 at the time of the interview. We excluded individuals from analyses if they were missing data for both race and ethnicity, and sex.
Clinical information included subjects’ level of tic impairment using the lifetime worst-ever-YGTSS Total Tic Score (we-YGTSS TTS; combined motor and vocal severity, range 0–50); age of TS symptom onset (years); age of TS diagnosis TS (years); presence ADHD and/or OCD (yes, no); the age of symptom onset of ADHD and/or OCD if present (years), the age of diagnosis of ADHD and/or OCD if present (years); if individuals ever took medications for tics and/or TS (yes, no), and a list of medications taken for conditions discussed above (total number). Time-to-TS-diagnosis (years) was calculated from the available data and defined as the time from the age of symptom onset to the age of diagnosis by a clinician or, as determined by the TAAICG investigators based on standardized assessments if never formally diagnosed. The median age for the appropriate grade or age range was used for individuals who provided a non-exact age, such as grade in school or an age range. We created a variable that captured the total number of medications taken (range 0–20) using the three questions about medications taken for tics/TS, ADHD, and OCD and one additional question about other medications. The variable was collapsed into three categories based on the overall distribution of the categories: 1) 0–1 medications, 2) 2–4 medications, and 3) ≥ 5 medications.
Data Availability Statement:
Data will be shared through collaborative arrangements with qualified investigators.
Statistical analysis
The primary tic-related outcome variables were TS age of symptom onset, TS age of diagnosis, time-to-TS-diagnosis, measures of tic severity (i.e., we-YGTSS TTS), ADHD or OCD clinical measures, and the total number of medications (i.e., 0–1, 2–4, ≥5). The primary explanatory variable was the collapsed race and ethnicity category (Non-Hispanic white vs. Other). T-tests were performed for normally distributed continuous outcome variables: TS age at diagnosis, and we-YGTSS TTS. Chi-square tests were performed for categorical outcomes, such as OCD and ADHD diagnosis, and the total number of medications taken. We fitted linear and logistic regression models to estimate the association between the collapsed race and ethnicity variable and these outcomes of interest after adjusting for sex and parental educational attainment.
To assess whether individuals with a higher parental educational achievement experienced better outcomes than those with lower levels of parental educational achievement, our variable of interest was derived by combining both parents’ levels of education. The outcome variables of interest were the same as in the Non-Hispanic white vs. Other analyses. One-way ANOVA tests were performed for normally distributed continuous outcome variables: TS age at diagnosis, and we-YGTSS TTS. Kruskal-Wallis test was performed for continuous non-normally distributed outcome: TS age of symptom onset. Chi-square statistics for categorical variable outcomes were performed: OCD presence, ADHD presence, and the total number of medications. Statistical significance was set at the p=0.05 level. Data were analyzed using STATA 16.1 (College Station, TX).
Results
There were 723 individuals included in our study, with a predominantly male (N=578 [79.9%]) and white (N=627 [92.6%]) sample (Table 1). The race and ethnicity categories were collapsed as Non-Hispanic white (N=566, [88.0%]) vs. Other (Hispanic, Black, American Indian, Asian, or More than one race), with N=77 [12%] being in the Other category. Most subjects (N=480 [73.6%]) had at least one parent with a 4-year college degree.
Table 1.
Demographic Characteristics of Participants with Tourette Syndrome in the TAAICG Database
| Categorical Measures | N (%) |
|---|---|
| Sex | 723 |
| Male | 578 (79.9) |
| Female | 145 (20.1) |
| Race | 677 |
| white | 627 (92.6) |
| Black | 5 (0.7) |
| American Indian | 1 (0.2) |
| Asian | 12 (1.8) |
| More than one race | 32 (4.7) |
| Ethnicity | 640 |
| Non-Hispanic | 603 (94.2) |
| Hispanic | 37 (5.8) |
| Race/Ethnicity Collapsed * | 643 |
| Non-Hispanic white | 566 (88.0) |
| Other | 77 (12.0) |
| Paternal Education | 657 |
| Under 7 years school | 2 (0.3) |
| Junior High School | 4 (0.6) |
| Partial High School | 22 (3.4) |
| High School | 169 (25.7) |
| 2-Year College | 69 (10.5) |
| 4-Year College | 192 (29.2) |
| Graduate/Professional | 199 (30.3) |
| Maternal Education | 674 |
| Under 7 years school | 1 (0.15) |
| Junior High School | 2 (0.3) |
| Partial High School | 10 (1.5) |
| High School | 138 (20.5) |
| 2-Year College | 101 (15) |
| 4-Year College | 230 (34.1) |
| Graduate/Professional | 192 (28.5) |
| Combined Parental Education ** | 652 |
| Both Parents Less Than College | 172 (26.3) |
| One Parent At Least College | 157 (24.1) |
| Both Parents At Least College | 323 (49.5) |
Abbreviations:
TAAICG= Tourette Association International Consortium for Genetics
TS= Tourette Syndrome; YGTSS=Yale Global Tic Severity Scale
Race/Ethnicity Collapsed: Non-Hispanic white= white, Non-Hispanic; Other= white, Hispanic; Black, Asian, American Indian, More than One Race
College Degree is defined as 4-Year College
Table 2 summarizes the clinical characteristics of the individuals. Subjects’ age at the time of the interview ranged from 4 to 21 years (mean 12.5 ± 4). The mean TS age of onset of symptoms was 5.6 ± 2.4 years. The mean TS age of diagnosis was 8.4 ± 2.9 years. The median (Q1, Q3) time-to-TS-diagnosis was 2 (1, 4) years. The mean we-YGTSS TTS was 31.3 ± 7.9. ADHD or OCD was present in 53.5% of individuals. The average number of medications taken for any diagnosis (i.e., TS, ADHD, OCD) was 3.7 ± 3.4 (range, 0–20), with 32.1% of the individuals taking 5 or more medications overall. More than half of the individuals took medications for tics (67.2%) or OCD (69.1%), and (43.6%) took medications for ADHD.
Table 2.
Clinical Characteristics of Participants with Tourette Syndrome in the TAAICG Database
| Continuous Measures | N | Mean (SD) |
|---|---|---|
| Age at Interview (4–21 Years) | 723 | 12.5 (4) |
| TS Age of Symptom Onset (Years) | 717 | 5.6 (2.4) |
| TS Age of Diagnosis (Years) | 618 | 8.4 (2.9) |
| we-YGTSS Mean (SD) | 686 | 31.3 (7.9) |
| ADHD Age of Symptom Onset (Years) | 344 | 4.2 (1.7) |
| ADHD Age of Diagnosis (Years) | 318 | 7.7 (3) |
| OCD Age of Symptom Onset (Years) | 363 | 6.4 (3) |
| OCD Age of Diagnosis (Years) | 247 | 9 (2.7) |
| Total Number of Medications Taken (0–20) | 604 | 3.7 (3.4) |
| Categorical Measures | N/Total (%) | |
| ADHD Presence | 369/690 (53.5) | |
| OCD Presence | 375/701 (53.5) | |
| Indicated Took TS Medications | 360/536 (67.2) | |
| Indicated Took ADHD Meds | 277/636 (43.6) | |
| Indicated Took OCD Meds Taken | 142/460 (69.1) | |
Abbreviations:
TAAICG= Tourette Association International Consortium for Genetics
SD= standard deviation; TS= Tourette Syndrome; ADHD= Attention Deficit Hyperactivity Disorder
OCD= Obsessive Compulsive Disorder; YGTSS= Yale Global Tic Severity Scale
Differences by race and ethnicity are given in Table 3. Individuals in the Other group were diagnosed with TS 0.9 years earlier than the Non-Hispanic white group (7.6 years vs. 8.5 years, t=2.9; p=0.0045). There were no significant differences in we-YGTSS TTS, the number of medications taken, or the proportion of OCD or ADHD diagnoses. When subjects were categorized by parental educational attainment, no differences were observed in age of tic symptom onset, age of TS diagnosis, tic severity measures (i.e., we-YGTSS TTS), number of medications taken, or proportion with OCD or ADHD (Table 4). In a multivariable linear regression model, the estimated association between the combined race and ethnicity variable, parental educational attainment, sex and TS age at diagnosis was not statistically significant (b= −0.7, p=0.07) (Table 5).
Table 3.
Study Sample Stratified by Other vs Non-Hispanic white*
| Continuous Measuresa | Other* | Non-Hispanic white* | test statistic† | p-value |
|---|---|---|---|---|
| Age at Interview, Mean Years (SD) | 12.0 (3.8) | 12.7 (4.0) | 1.6 | 0.1 |
| TS Age of Symptom Onset, Mean Years (SD) | 4.7 (2.0) | 5.8 (2.5) | 4.3 | <0.0001 |
| TS Age at Diagnosis, Mean Years (SD) | 7.6 (2.3) | 8.5 (2.9) | 2.9 | 0.0045 |
| TS Time-to-Diagnosis, Median Years (Q1, Q3) | 3 (1, 4) | 2 (1, 4) | −0.9 | 0.4 |
| Worst-ever YGTSS, Mean (SD) | 31.6 (9.2) | 31.4 (7.7) | −0.2 | 0.9 |
| ADHD Age of Symptom Onset, Mean Years (SD) | 4.3 (1.4) | 4.1 (1.7) | −0.9 | 0.4 |
| ADHD Age at Diagnosis, Mean Years (SD) | 7.4 (2.9) | 7.8 (3.0) | 0.7 | 0.5 |
| ADHD Time-to-Diagnosis, Median Years (Q1, Q3) | 2 (1, 3.5) | 3 (1, 5) | 0.6 | 0.6 |
| OCD Age of Symptom Onset, Median years (Q1, Q3) | 5 (3, 8) | 6 (4, 8) | 1.7 | 0.09 |
| OCD Age of Diagnosis, Mean Years (SD) | 8.1 (2.6) | 9.1 (2.7) | 1.6 | 0.1 |
| OCD Time-to-Diagnosis, Median Years (Q1, Q3) | 2 (1, 3) | 2 (1, 4) | 0.1 | 0.9 |
| Categorical Measures | Other N (%) | Non-Hispanic white N (%) | test statistic† | p-value |
| OCD Presence | 39/74 (52.7) | 304/555 (54.8) | 0.1 | 0.7 |
| ADHD Presence | 44/76 (57.9) | 272/538 (50.6) | 1.4 | 0.2 |
| Total Number of Medications | N=61 | N=483 | 0.3 | 0.8 |
| 0–1 | 19 (31.2) | 151 (31.3) | ||
| 2–4 | 20 (32.8) | 174 (36.0) | ||
| >=5 | 22 (36.1) | 158 (32.7) |
Abbreviations: TS=Tourette Syndrome; YGTSS=Yale Global Tic Severity Scale; we-YGTSS=Worst-ever YGTSS
Total numbers for each variable
-Age at Interview: Non-Hispanic white N=566; Other N=77; Age TS Symptom Onset: Non-Hispanic white N=560; Other =77; -Age TS Diagnosis: Non-Hispanic white N =499, Other= 65; -Age TS Time-to-Diagnosis: Non-Hispanic white N=498; Other=65; we-YGTSS: Non-Hispanic white N=551, N=74; excluded individual with we-YGTSS score of 0; Age ADHD Symptom Onset: Non-Hispanic white N=257; Other N=41; Age ADHD Diagnosis: Non-Hispanic white N=249; Other N=32; Age ADHD Time-to-Diagnosis: Non-Hispanic white N=200; Other N=28; Age OCD Symptom Onset: Non-Hispanic white N=295; Other N=37; Age OCD Diagnosis: Non-Hispanic white N=204; Other N=24; Age OCD Time-to-Diagnosis: Non-Hispanic white N=177; Other N=21
white= white, Non-Hispanic; Other= white Hispanic, Black, Asian, American Indian, More than One Race
t-tests performed for normally distributed variables; Wilcoxon rank-sum (Mann-Whitney) test performed for non-normally distributed variables; chi-squared testing performed for categorical variables (OCD or ADHD presence df=1; Total Number of Medications df=2) bold indicates p <0.05
Table 4.
| Continuous Measures | Both Parents Less Than College | One Parent At Least College | Both Parents At Least College | test statistic† | p-value |
|---|---|---|---|---|---|
| Age at Interview, Mean Years (SD) | 11.9 (3.7) | 12.5 (3.9) | 12.7 (4.1) | 2.1 | 0.13 |
| TS Age of Symptom Onset, Median Years (Q1, Q3) | 6 (4, 7) | 6 (4, 7) | 5 (4, 7) | 0.8 | 0.7 |
| TS Age at Diagnosis, Mean Years (SD) | 8.6 (3.1) | 8.3 (2.5) | 8.5 (2.8) | 0.5 | 0.6 |
| TS Time-to-Diagnosis, Median (Q1, Q3) | 2 (1, 4) | 2 (1, 4) | 2 (1, 5) | 3.1 | 0.2 |
| we-YGTSS, Mean (SD) | 31.2 (7.8) | 31.2 (8.6) | 31.4 (7.6) | 0.04 | 0.96 |
| Categorical Measures | Both Parents Less Than College | One Parent At Least College | Both Parents At Least College | test statistic† | p-value |
| OCD | N (%) | N (%) | N (%) | 0.3 | 0.8 |
| Presence | 92/166 (55.4) | 81/155 (52.3) | 169/315 (53.7) | ||
| ADHD | N (%) | N (%) | N (%) | 0.5 | 0.8 |
| Presence | 88/164 (53.7) | 81/152 (53.3) | 157/309 (50.8) | ||
| Total Number of Medications | N (%) | N (%) | N (%) | 4.2 | 0.4 |
| 0–1 | 50 (35.0) | 40 (31.5) | 89 (31.6) | ||
| 2–4 | 46 (32.0) | 41 (32.3) | 112 (39.7) | ||
| >=5 | 47 (33.0) | 46 (36.2) | 81 (28.7) |
Abbreviations: TS= Tourette Syndrome; we-YGTSS= worst-ever Yale Global Tic Severity Scale; ADHD= attention deficit hyperactivity disorder; OCD= obsessive compulsive disorder
Total numbers for each variable
Age at Interview: Both Parents Less Than College N=172; One Parent At Least College N=157; Both Parents at Least College N=323
-Age TS Symptom Onset: Both Parents Less Than College N=172; One Parent At Least College N=155; Both Parents at Least College N=322
-Age TS Diagnosis: Both Parents Less Than College N=141; One Parent At Least College N=141; Both Parents at Least College N=290
-Age TS Time-to-Diagnosis: Both Parents Less Than College N=141; One Parent At Least College N=140; Both Parents at Least College N=290
-Worst-ever YGTSS: Both Parents Less Than College N=166; One Parent At Least College N=155; Both Parents at Least College N=315
College Degree= 4-Year College
one-way ANOVA performed for normally distributed variables; Kruskal-Wallis test performed for non-normally distributed variables; chi-squared testing performed for categorical variables (OCD or ADHD presence df= 2; total number of medications df= 4)
Table 5.
Regression Analysis Tourette Syndrome Age of Diagnosis
| Model 1: Race/Ethnicity | Model 2: Race/Ethnicity, Sex, Education | |||||
|---|---|---|---|---|---|---|
| β | SE | p-value | β | SE | p-value | |
| white Non-Hispanic | Reference | Reference | ||||
| Other | −0.9 | 0.4 | 0.02 | −0.7 | 0.4 | 0.07 |
| Male | Reference | |||||
| Female | 0.3 | 0.31 | 0.3 | |||
| Both Parents Less than College* | Reference | |||||
| One Parent At Least College* | −0.3 | 0.4 | 0.5 | |||
| Both Parents At Least College* | −0.10 | 0.3 | 0.7 | |||
College Degree= 4-Year College
Discussion
In this secondary analysis of a large, international research dataset from the TAAICG, contrary to our hypothesis, we found few substantive differences between Non-Hispanic white individuals with TS and those from other racial and ethnic groups. The primary finding, that individuals from racial and ethnic minority groups, when combined, experienced an earlier age of TS diagnosis than Non-Hispanic white individuals, was no longer significant after controlling for parental educational attainment, and became even less notable when controlling for co-occurring ADHD. There were no differences in tic severity or prevalence of OCD or ADHD between the two groups. In addition, there was no evidence of group differences by combined parental level of education. These findings were not consistent with our initial hypotheses. Based on other studies examining racial, ethnic, and sociodemographic disparities in ADHD, OCD, and other neuropsychiatric/neurologic conditions,24,25 we had hypothesized that children from under-represented minority groups or whose parents had lower levels of formal education would have worse clinical outcomes.
Our primary finding of a lack of racial and ethnic disparities in outcomes may be due to selection bias as the individuals that enrolled in research were likely from higher socioeconomic status as the majority of individuals were highly educated. In addition, combining racial and ethnic minority groups could have potentially confounded possible racial and ethnic differences between non-white subgroups. Race and ethnicity were collapsed to allow for higher statistical power. This has been done in other disorders assessing race and ethnicity.24 However, homogenizing individuals from different racial and ethnic groups may influence outcomes, affect the interpretations of the data, and mask potential racial and ethnic disparities.
The dataset also does not include information on additional socioeconomic factors (e.g., income, type of health insurance, access to specialty clinics), which may play a role in TS outcomes. Families who participated in the TAAICG genetics study were highly educated (>50% of parents completed a college degree) and recruitment strategies focused on individuals of European ancestry, so the sample was predominantly white. Thus, although our analysis represents one of the largest studies of TS to date, there was only limited representation of individuals from non-white or lower-educated families. Therefore, our dataset is not necessarily representative of the true TS population. Other studies have also observed the under-representation of racial and ethnic minority groups with TS.13,17 One study, using national surveys, found that non-Hispanic white and Hispanic individuals have similar rates of TS, but data was not available for other races (e.g., Black and Asian).14
There is also the possibility that educational achievement may help families overcome race and ethnicity-related barriers to achieve better health outcomes29 as has been seen in other disorders.30 However, whether a larger sample of families from racial and ethnic minority groups with lower parental educational attainment would support the hypothesis of racial and ethnic disparities in TS outcomes remains unknown.31 Another possibility is that once individuals from racial and ethnic minority groups are seen in specialty clinics, there are no disparities in outcomes based on race and ethnicity.
We also do not have information on type of schooling a child was enrolled in (e.g., public vs private school) to understand if type of schooling affected tic-related outcomes.We also intended to separate individuals into separate age groups (e.g., child, adolescent), but due to the low number of individuals from racial and ethnic minority groups, we did not have sufficient power to examine these groups separately.
To better understand whether there are true racial and ethnic differences in individuals with TS compared to white individuals with TS, we suggest a different population-based study design with efforts focused on recruiting participants from diverse backgrounds to understand better where racial and ethnic disparities may exist in TS. The initial parent study was biased toward European individuals, similar to early studies on human genetics;32 thus, our study cohort was predominantly white. In addition, the study participants were highly educated. The high level of parental educational achievement and the small sample of individuals from racial and ethnic minority groups may mask potential disparities for historically disadvantaged groups.
This study has several strengths. First, our study uses a dataset of well-defined and carefully assessed individuals with TS and associated comorbid conditions (i.e., ADHD and OCD) using structured clinical interviews following a best-estimate process. Second, our dataset includes standardized and validated severity measures for tics (e.g., we-YGTSS TTS and impairment), which provided the opportunity to examine disparities in individuals with TS with a well-curated, clinician-administered diagnostic instrument, including in-depth individual symptom-level data.
As noted, there are multiple limitations of this study. The most important ones being, collapsing race and ethnicity, a highly educated cohort, and only ~10% of the individuals being from racial and ethnic minority groups affecting generalizability. As mentioned, we collapsed race and ethnicity as “Other” to maximize sample size for statistical analysis given the low representation of racial and ethnic minority groups in our sample. We recognize that this binary framework approach has several issues such as perpetuating bias and stereotypes, and does not account for specific differences within racial and ethnic minority groups.33 Despite these limitations, the findings of this study have potential implications for clinical practice and research. First, they demonstrate the need to design studies focused on racial and ethnic minority groups and associations with social determinants of health in TS to better understand whether there are true racial and ethnic differences in individuals with TS compared to white individuals. An inclusive approach to improve recruitment of racial and ethnic minorities includes community engagement and collaborating with stakeholders to develop research protocols and recruitment strategies. This may simultaneously forge strong community partnerships and help transcend the history of medical distrust that patients may face.
Conclusions
Using the TAAICG dataset, a large international research dataset of a well-characterized group of individuals with Tourette Syndrome, we identified that individuals from racial and ethnic minority groups with TS received an earlier diagnosis of TS compared to white individuals with TS but failed to identify other differences in outcomes by race and ethnicity or parental educational attainment. These findings were not expected. However, it highlights the need for future studies conducted in a larger, more diverse population to characterize possible differences in outcomes among non-white individuals, to understand why historically marginalized individuals may experience earlier diagnoses of TS, and/or to determine if additional factors contribute to our findings. There may be multiple barriers to overcome such as 1) mistrust and discomfort with the clinical trial process; 2) lack of information about clinical trials; 3) resource and time barriers associated with participation; and 4) lack of awareness of clinical trials and their importance. Further, different cultures may have different thresholds for considering a tic disorder a medical disorder.4,34,35 Therefore, we also need to understand if there are potential factors or biases that impact referral rates to subspecialty clinics, such as physician bias and patient perspectives. We suggest that research efforts include a multi-modal approach (e.g., quantitative, qualitative, and mixed methods) at different levels (i.e., individual, provider, community, systems)36 to understand where disparities may exist and begin to propose interventions at each level to provide equitable care and improve the quality of life of individuals with tic disorders and families taking care of individuals with tic disorders.
Supplementary Material
Acknowledgements:
We are grateful to the individuals with TS and their families that participated in the study. We also acknowledge members of the Tourette Association of America International Consortium for Genetics. The authors would like to acknowledge the editorial support provided by Susan Sheng, PhD as part of the MGH Center for Faculty Development and the MGB Scientific Writers Group; Alexander Tsai, MD, PhD for review of the manuscript; Heather Fullerton, MD, PhD for review of the manuscript, and the CNCDP-K12 Works in Progress Group for review of the manuscript.
Study Funding:
This study was funded by the Tourette Association of America and NINDS, NIH K12NS098482, R01 NS102371, and R01 NS105746. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Financial Disclosures of all authors:
Marisela E. Dy-Hollins has received research support from the Tourette Association of America and NIH K12NS098482.
Samuel J. Carr reports no disclosures relevant to the manuscript.
Angela Essa reports no disclosures relevant to the manuscript.
Lisa Osiecki reports no disclosures relevant to the manuscript.
Daniel T. Lackland reports no disclosures relevant to the manuscript.
Jenifer H. Voeks reports no disclosures relevant to the manuscript.
Nicte I. Mejia receives funding for projects she leads: Massachusetts General Brigham receives funding from the following non-profit entities Biogen Foundation, Massachusetts Life Sciences Center, and Muscular Dystrophy Association.
Nutan Sharma has received research support from NIH grants NIH P01 NS087997 and R21 NS118541. Dr. Sharma has received honoraria from John Wiley Publishing for serving as editor-in-chief for Brain and Behavior.
Lori B. Chibnik reports no disclosures relevant to the manuscript.
Cathy L. Budman reports no disclosures relevant to the manuscript.
Danielle C. Cath has no financial disclosures. She has been an unpaid member of the steering committee of the European Society for the Study of Tourette Syndrome (ESSTS), and is a member of the Dutch TS advisory board..
Marco A. Grados reports no disclosures relevant to the manuscript.
Robert A. King reports no disclosures relevant to the manuscript.
Gholson Lyon reports no disclosures relevant to the manuscript.
Guy A. Rouleau reports no disclosures relevant to the manuscript.
Paul Sandor reports no disclosures relevant to the manuscript.
Harvey S. Singer receives royalties from the 3rd edition of book, Movement Disorders in Childhood, Elsevier.
Carol A. Mathews has received research support from NIH grants R01NS105746 and R01NS102371. She is an unpaid member of the International OCD Foundation Scientific and Clinical Advisory Board and the Family Foundation for OCD Research Advisory Board.
Jeremiah Scharf has received research support from NIH grants R01NS105746 and R01NS102371. Dr. Scharf is also an unpaid member of the Tourette Association of America Scientific Advisory Board.
Co-author receives funding for projects she leads: Massachusetts General Brigham receives funding from the following non-profit entities Biogen Foundation, Massachusetts Life Sciences Center, and Muscular Dystrophy Association- NIM
Co-author has received research support from NIH grants NIH P01 NS087997 and R21 NS118541. Dr. Sharma has received honoraria from John Wiley Publishing for serving as editor-in-chief for Brain and Behavior- NS
Co-author is an unpaid member of the steering committee of the European Society for the Study of Tourette Syndrome (ESSTS), and is a member of the Dutch TS advisory board- DCC
Co-author receives royalties from the 3rd edition of book, Movement Disorders in Childhood, Elsevier- HSS
Co-author has received research support from NIH grants R01NS105746 and R01NS102371. She is an unpaid member of the International OCD Foundation Scientific and Clinical Advisory Board and the Family Foundation for OCD Research Advisory Board- CAM
Co-author has received research support from NIH grants R01NS105746 and R01NS102371. Dr. Scharf is also an unpaid member of the Tourette Association of America Scientific Advisory Board- JS
Footnotes
Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Data Availability Statement
Data will be shared through collaborative arrangements with qualified investigators.