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. 2021 May 27;8(5):733–742. doi: 10.1002/mdc3.13240

Multiculturalism: A Challenge for Cognitive Screeners in Parkinson's Disease

Marta Statucka 1, Kirsten Cherian 2,3, Alfonso Fasano 1,4,5, Renato P Munhoz 1,4,5, Melanie Cohn 1,6,✉
PMCID: PMC8287166  PMID: 34307746

ABSTRACT

Background

The Montreal Cognitive Assessment (MoCA) and the Dementia Rating Scale‐2 (DRS‐2) are recommended screeners for Parkinson's disease mild cognitive impairment (PD‐MCI). Cross‐cultural studies examining their diagnostic precision have not addressed cultural bias in a multicultural setting.

Objectives

To compare DRS‐2 and MoCA performance between patients born in Canada, the USA, and the UK (Anglosphere group) and immigrant patients born elsewhere (International group). To identify sources of cultural bias by comparing group characteristics, and by assessing the relationships between performance and immigration and socio‐development variables. To examine the diagnostic precision of both tools in detecting PD‐MCI in each group.

Methods

We conducted a clinical chart review of advanced PD patients who completed cognitive screeners (MoCA: n = 288, 30% International group; DRS‐2: n = 426, 31% International group). All completed a comprehensive neuropsychological assessment to apply Level II PD‐MCI diagnostic criteria.

Results

The International group performed worse than the Anglosphere group on the MoCA and DRS‐2, and the only variable that accounted for some of the group difference was the Historical Index of Human Development, a societal variable, which fully mediated the group effect on the DRS‐2. Diagnostic precision of the MoCA was at chance level in the International group, and was poorer than that of the DRS‐II in this group and that of the MoCA in the Anglosphere group, although these were considered poor.

Conclusions

Our results support the recommendation to exert caution in using cognitive screeners to capture PD‐MCI in all patients and particularly with first generation immigrants.

Keywords: mild cognitive impairment, Montreal Cognitive Assessment, Dementia Rating Scale, immigrants

Cognitive decline is a prevalent symptom of Parkinson's disease (PD). While a comprehensive neuropsychological assessment is the gold standard for PD dementia (PDD) 1 and mild cognitive impairment (PD‐MCI) 2 diagnoses, resources are often limited and repeating assessments over time is not feasible. Instead, cognitive screeners are more amenable to routine care and tools such as the Mattis Dementia Rating Scale‐2 (DRS‐2) 3 and the Montreal Cognitive Assessment (MoCA) 4 are recommended for use in PD. 5 Both scales are translated into numerous languages and are validated for PD around the globe, albeit with variable pass/fail scores. These cross‐cultural initiatives, however, do not address the challenge of cognitive testing in a multicultural setting.

Cultural bias on cognitive tasks within multicultural societies is seldom examined in PD research. In other clinical groups, bias was mainly demonstrated in testing of racial/ethnic groups in the USA, with the confounds of education, literacy, socioeconomic status and general health differences. 6 , 7 Such research may not generalize to multicultural societies such as Toronto, Canada where immigrants represent 50% of the population, 8 and are generally healthy 9 , 10 and highly educated. 8 Because normative data from immigrants' country of birth do not take acculturation effects into account and the development of norms for all subgroups of immigrants is impractical, 11 a first step in multicultural research is to identify the magnitude and sources of bias on existing tools. One source may lie in the degree of correspondence between the patients' country of origin and where the tests are designed and validated. Cognitive tests were mainly developed in “Anglosphere” countries, such as the USA (DRS‐2) and Canada (MoCA). The “Anglosphere”, a term coined by the writer Neal Stephenson, reflects a broad societal context characterized not only by the predominance of the English language, but also by shared cultural and historical roots, and similarly high levels of economic and social development. It typically includes Canada, the UK, the USA, Australia, and New Zealand. We recently demonstrated that measures of visuospatial and executive functions, but not of attention and memory, were biased against PD patients born outside Anglosphere countries, 12 and this was not related to demographic, linguistic, clinical, or immigration variables, but was mediated by the degree of socio‐development of their country of birth as measured by the Historical Index of Human Development (HIHD). 13

Here, we investigate cultural bias on the DRS‐2 and MoCA in PD patients by examining whether performance differs between individuals born in Canada, the USA, and the UK (Anglosphere group) and other countries (International group). To identify sources of bias, we compare the two groups' socio‐demographic and clinical characteristics, investigate the relationships between test performance and immigration variables, and assess whether the HIHD 13 of participants' country of birth mediates group differences in performance. Lastly, we examine the diagnostic precision of the DRS‐2 and MoCA in detecting PD‐MCI in each group.

Method

Participants

We conducted a chart review of advanced PD patients who completed neuropsychological and neurological assessments to determine their candidacy for Deep Brain Stimulation (DBS) at Toronto Western Hospital UHN between January 2009 and September 2020. A flow diagram depicting included and excluded patients is presented in Figure 1. Exclusion criteria applied sequentially were age less than 45 years‐old, other neurological conditions, developmental disorders, pre‐PD severe psychiatric disorder, no MoCA or DRS‐2 score, assessments wherein interpreters provided assistance to patients with limited English proficiency and to English‐as‐a‐second language (ESL) patients who opted for this service, assessments that did not meet Level II PD‐MCI diagnostic criteria which require at least two tests in each of five cognitive domains, patients with severe ratings on a depression scale [Beck Depression Inventory‐II (BDI‐II) 14  > 28 or Geriatric Depression Scale (GDS) 15  > 19], assessments of questionable validity, diagnosis of PDD (Level II), and a patient born in country with no HIHD data.

FIG 1.

FIG 1

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Flow diagram of the study and reasons for exclusion.

In total we included 288 patients with a MoCA score (Anglosphere: n = 203; International: n = 85), and 426 patients with a DRS‐2 score (Anglosphere: n = 294; International: n = 132), and of these, 286 patients completed both measures (Anglosphere: n = 203; International: n = 83). Individuals in the Anglosphere group were born in Canada (89%), the UK/Ireland (9%) and the USA (2%), and individuals in the International group emigrated from 48 different countries primarily from Asia (47%) and Europe (28%; breakdown presented in Table S1).

Diagnosis of PD‐MCI

We applied the MDS PD‐MCI Level II diagnostic criteria 2 based on patients' comprehensive neuropsychological assessment. PD‐MCI diagnosis required: (1) self‐ or family‐report of progressive cognitive decline during a semi‐structured clinical interview sampling changes in memory, attention, executive functions and language, or current elevation (>1.5 SD normative mean) and a change in ratings relative to pre‐PD status (1.5 SD difference) on the executive dysfunction subscale of the Self or Family Frontal Systems Behavior Scale (FrSBe); 16 (2) preserved independence with instrumental activities of daily living (iADLs) from a cognitive (rather than physical) perspective based on a semi‐structured interview sampling activities such as finances, shopping, medication, driving, hobbies, and cooking; and (3) performance 1.5 SD below normative mean on at least two neuropsychological tests (tests used and group performance data are presented in supplementary). Tests were administered by trained psychometrists and diagnoses were reached via consensus by licensed neuropsychologists (M.S. and M.C.).

Disease‐Related, Demographic, Immigration and Societal Variables

Indicators of disease severity include PD duration (years since diagnosis), scores on the Unified Parkinson's Disease Rating Scale part 3 (UPDRS part 3) 17 ON medications, and levodopa equivalent daily dose (LEDD). 18 The MDS‐UPDRS part 3 19 was used in a subgroup (n = 117) and scores were transformed to be equivalent to the older version. 20 Demographic variables include age, sex, and years of education. We also coded whether patients were native English‐speakers and whether English was the language of instruction during part of their education. Group assignment reflects the country of birth but some Anglosphere patients are ESL and some International patients are native‐English speakers. Many ESL individuals in the International group attended school in English in their country of birth (n = 23), or in Canada after immigration (n = 26 starting from elementary and/or secondary school; n = 30 starting in college or university). Depressive symptom severity was coded as present/absent based on the BDI‐II (≥14) or GDS (≥10).

For the International group, immigration variables included age at immigration and years in Canada. All participants were assigned a socio‐development context score, namely the HIHD, based on their country and year of birth. The HIHD reflects a country's development and well‐being in a scalable (0 to 1) manner by averaging key dimensions of human development including health (life expectancy), education (literacy and school enrollment), and standard of living (gross domestic product). The HIHD is available in 5‐year intervals and scores closest to patients' year of birth were used. No HIHD values are available from 1939 to 1949, and the nearest value was used for these years (1938 or 1950). The average HIHD of participants per country of birth are presented in Table S2.

Cognitive Screening Measures and Procedures

The DRS‐2 was administered during the comprehensive neuropsychological assessment and the English version of the MoCA was administered during a neurology visit within 12 months of the neuropsychological assessment (time difference in years: M = −0.38; SD = 0.28). Variables for the MoCA and DRS‐2 are the total scores and the frequency of scores below PD‐specific suggested cutoffs (MoCA ≤ 26; 21 , 22 , 23 , 24 , 25 DRS‐2 ≤ 139). 24 , 26

Statistical Analyses

Using SPSSv22, 27 differences between the Anglosphere and International groups were examined with t‐test or chi‐square for disease‐related, socio‐demographic, and cognitive variables. We investigated whether group differences on the MoCA and DRS‐2 remained when controlling for the presence of depressive symptoms using ANCOVA, and when restricting analyses to patients educated in English using t‐test. We used Pearson correlations between DRS‐2 and MoCA scores versus age at immigration and years in Canada in the International group to examine potential sources of bias. Significance level was set at P < 0.05 and effect sizes are reported as Cohen's d. After ensuring that the HIHD correlated with MoCA and DRS‐2 scores, we investigated whether it mediated the relationships between group (Anglosphere vs International) and DRS‐2 and MoCA scores using PROCESSv.3.3 28 and significance level based on bootstrapping (5000 resamplings) with 95% CI.

Diagnostic precision of the MoCA and DRS‐2 in detecting PD‐MCI was examined with receiver‐operating characteristic (ROC) analyses for each test in each group using MEDCALCv19.4.0 29 . We report the area under the curve (AUC), cutoff scores associated with 80% sensitivity (optimal for screening) and with 80% specificity (optimal for diagnosis) for cognitive tests showing significant AUCs, and the associated proportion of correct diagnoses. We compared the AUCs of tests within each group (patients who completed both the MoCA and DRS‐2), and between groups for each test using the empirical nonparametric method. 30

Results

Demographic and Clinical Characteristics

There were no significant differences between the International and Anglosphere groups on demographic (age, years of education, sex) or clinical (LEDD, disease duration, UPDRS ON, presence of mild–moderate depression) variables (Table 1). There were also no group differences in rates of PD‐MCI diagnoses (Level II).

TABLE 1.

Characteristics of Canadian PD patients based on their region of birth

MoCA sample DRS‐2 sample Statistics a
Anglosphere (n = 203) International (n = 85) Anglosphere (n = 294) International (n = 132) MoCA sample DRS‐2 sample
Socio‐demographic
Age 63.44 (6.62) 62.55 (6.24) 63.41 (6.74) 62.45 (6.31) P = 0.29, d = 0.14 P = 0.16, d = 0.15
Female% 33.5% 32.9% 32.7% 33.3% P = 0.93, d = 0.01 P = 0.89, d = 0.01
Education (years) 14.49 (2.86) 14.60 (3.05) 14.63 (2.91) 14.80 (2.98) P = 0.77, d = 0.04 P = 0.58, d = 0.06
English 1st language 96.6% 20.0% 95.9% 21.2% P < 0.001, d = 2.63 P < 0.001, d = 2.46
English education 100% 80.0% 100% 81.1%
Immigration age 26.81 (13.18) 25.69 (13.48)
Years in Canada 35.74 (15.90) 36.76 (15.72)
HIHD .487 (0.049) .240 (0.113) .488 (0.048) .243 (0.114) P < 0.001, d = 3.35 P < 0.001, d = 3.27
Disease‐related
PD duration (years) 10.10 (4.03) 9.84 (4.13) 10.27 (4.57) 10.24 (4.08) P = 0.61, d = 0.06 P = 0.94, d = 0.01
UPDRS part3 ON 14.52 (9.66) 15.58 (9.77) 14.42 (9.43) 15.07 (9.28) P = 0.40, d = 0.11 P = 0.51, d = 0.07
LEDD (mg) 1372.93 (627.76) 1271.72 (571.28) 1345.53 (607.75) 1249.23 (558.17) P = 0.20, d = 0.17 P = 0.12, d = 0.16
Mild–moderate depression scores 21.2% 31.8% 22.4% 29.5% P = 0.06, d = 0.23 P = 0.12, d = 0.15
Cognitive
PD‐MCI (%) 59.6% 64.7% 60.2% 67.4% P = 0.42, d = 0.09 P = 0.16, d = 0.19
MoCA score (/30) 26.75 (2.41) 25.78 (3.11) P = 0.005, d = 0.37
MoCA ≤26 (%) 40.9% 52.9% P = 0.06, d = 0.22
DRS‐2 score (/144) 139.58 (3.78) 138.25 (4.58) P = 0.002, d = 0.33
DRS‐2 ≤139 (%) 38.8% 54.5% P = 0.002, d = 0.30
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a

All P‐values and Cohen's d were calculated using t‐tests or Chi‐square χ2. Data are reported as frequency or mean (SD). HIHD, Historical Index of Human Development; UPDRS, United Parkinson's Disease Rating Scale, LEDD, levodopa equivalent daily dose; PD‐MCI, Parkinson's disease mild cognitive impairment; MoCA, Montreal Cognitive Assessment; DRS‐2, Dementia Rating Scale 2nd edition.

Effect of Immigration Status on Cognitive Screeners

The International group had lower scores on the MoCA and DRS‐2 compared to the Anglosphere group (Table 1). The International group's DRS‐2 scores also fell below the suggested cutoff more frequently than those of the Anglosphere group (15.7% difference; P = 0.002, d = 0.30), but the difference was not statistically significant for the MoCA (12% difference; P = 0.06, d = 0.22). Group differences in scores remained after covarying the presence of depressive symptoms [DRS‐2: F (1,423) = 9.10, P = 0.003, d = 0.29; MoCA; F (1,286) = 7.60, P = 0.006, d = 0.33], and when limiting analyses to individuals educated in English [MoCA: t(269) = 2.75, P = 0.006, d = 0.39; DRS‐2: t(399) = 2.37; P = 0.02, d = 0.27].

Relationship between Screeners and Immigration and Societal Variables

In the International group, age at immigration did not significantly correlate with the MoCA (r = 0.09, P = 0.43) or the DRS‐2 (r = −0.05, P = 0.56), nor did years in Canada (MoCA: r = −0.17, P = 0.12; DRS‐2: r = −0.02, P = 0.81). The HIHD was higher in the Anglosphere group than in the International group (Table 1; Table S2), and showed small positive correlations with the MoCA (r = 0.17, P = 0.003) and the DRS‐2 (r = 0.19, P < 0.001) in the full sample. This motivated simple mediation analyses with group (X), HIHD (M), and MoCA or DRS‐2 score (Y). For the MoCA, path b was not significant (HIHD predicting MoCA controlling for group), and thus the HIHD was not a significant mediator (coefficient = −0.55; 95% CI −1.71 to +0.54). In contrast, all assumptions were met for the DRS‐2, and HIHD completely mediated the group effect on DRS‐2 scores (coefficient = −1.58; 95% CI −3.03 to −0.22; Fig. 2).

FIG 2.

FIG 2

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Mediation model for the DRS‐2.

Diagnostic Performance of Screening Tests across Groups

ROCs: As shown in Figure 3, the MoCA did not discriminate between intact cognition and PD‐MCI in the International group (AUC = 0.524, 95% CI 0.397–0.652, P = 0.71), but the DRS‐2 achieved significant, though poor diagnostic precision (AUC = 0.667, 95% CI 0.568–0.765, P < 0.001). Furthermore, the precision of the DRS‐2 was greater than that of the MoCA in the International subgroup assessed with both instruments [n = 83; MoCA: AUC = 0.532, 95% CI 0.402–0.662; DRS‐2: AUC = 0.710, 95% CI 0.591–0.829; z = 2.53, P = 0.01]. In the Anglosphere group, both the MoCA and the DRS‐2 showed significant, though poor diagnostic precision [MoCA: AUC = 0.679, 95% CI 0.606–0.752, P < 0.001; DRS‐2: AUC = 0.684, 95% CI 0.622–0.746, P < 0.001], with no significant differences between instruments in patients assessed with both [n = 203; MoCA: AUC = 0.679, 95% CI 0.606–0.752; DRS‐2: AUC = 0.688, 95% CI 0.614–0.762; z = 0.19, P = 0.85]. Comparisons between groups revealed significantly weaker precision in the International group relative to the Anglosphere group for the MoCA (z = 2.07; P = 0.038), but not for the DRS‐2 (z = 0.29, P = 0.77).

FIG 3.

FIG 3

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Receiver‐operator characteristic (ROC) curves for the MoCA and DRS‐2. Note. Panels A‐B demonstrate the ROC curves of the MoCA and DRS‐2 in the Anglosphere and International groups; Panels C‐D illustrate the ROC curves in the International and Anglosphere subgroups who completed both the MoCA and DRS‐2.

Suggested cutoff scores: Because the AUC for the MoCA in the International group was not significant, no cutoff score is suggested. In the Anglosphere group, a score of ≤28 on the MoCA was optimal to maximize sensitivity (0.81; specificity: 0.39) and ≤25 had optimal specificity (0.87; sensitivity: 0.37). Diagnostic accuracy was 63% and 67% at these levels. For the DRS‐2 in the Anglosphere group, ≤142 optimized sensitivity (0.86; specificity: 0.31) and ≤139 optimized specificity (0.80, sensitivity: 0.51), and these were associated with 64% and 68% correct diagnoses. For the DRS‐2 in the International group, ≤141 was optimal for sensitivity (0.82; specificity: 0.40) and ≤ 136 was optimal for specificity (0.81; sensitivity: 0.33), which were associated with 67% and 65% correct diagnoses. Detailed data across ranges of scores are provided in Table S3.

Discussion

In a culturally‐diverse PD sample from Toronto, Canada, we demonstrated that the MoCA and DRS‐2 are biased against immigrant patients born outside Canada, the UK or the USA (International group), although this group was comparable to patients born in the Anglosphere in terms of demographic and disease variables, including rates of PD‐MCI based on Level II diagnostic criteria. In the International group, performance on cognitive screeners was not related to age at immigration and years in Canada, and persisted when limiting analyses to individuals educated in English. However, the HIHD, a socio‐developmental context variable of the country and year of birth, completely mediated the relationship between group and DRS‐2 performance. This effect was not found for the MoCA, possibly due to the reduced power in this smaller sample. The fact that the HIHD mediates DRS‐2 performance is consistent with similar findings with visuospatial and executive function tasks reported in an overlapping pre‐DBS PD sample. 12 A few studies in other populations also demonstrate a relationship between human developmental indices and cognitive test scores, notably with measures of executive functioning in first generation immigrants with psychosis in Norway, 31 and on the Test of Memory Malingering in healthy older adults living in eight Latin American countries. 32 In sum, although the HIHD is coarse and encompasses only a few aspects of a society and its culture, it nonetheless relates to cognitive test performance which is particularly relevant to neuropsychological research in highly diverse settings such as ours and to international collaborations.

Our study also demonstrates that the diagnostic precision of the MoCA was no better than chance at identifying PD‐MCI in the International group, so no cutoff scores are proposed. It was also weaker than that of the DRS‐2 in the International subgroup tested with both tools, and that of the MoCA in the Anglosphere group. Interestingly, the diagnostic precision of the DRS‐2 was not significantly different between the Anglosphere and the International groups despite differences in total scores, suggesting that culture relates to performance on these measures differently. Importantly, though significant, the diagnostic precision of the DRS‐2 in both groups and of the MoCA in the Anglosphere group remains poor (<0.70 AUC). With respect to cutoff scores, ≤28 (screening) and ≤25 (diagnostic) are suggested for the MoCA in the Anglosphere group, ≤142 (screening) and ≤139 (diagnostic) are suggested for the DRS‐2 in the Anglosphere group, and ≤141 (screening) and ≤136 (diagnostic) for the DRS‐2 in the International group. For context, Figure 4 23 , 25 , 26 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 shows our AUC results and cutoff scores alongside those of other published studies in PD‐MCI conducted both in and outside Anglosphere countries. The latter show a very broad range of precision (from chance 33 , 34 to excellent levels) 35 , 36 for both cognitive tests, but in general, cutoff scores for the MoCA are lower than ours while those for the DRS‐2 are similar.

FIG 4.

FIG 4

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Diagnostic precision and suggested cutoffs for the MoCA and DRS‐2 across studies of PD‐MCI. Note. All studies compared PD‐MCI to PD‐intact. Screening cutoffs reflect >80% sensitivity and diagnostic cutoffs reflect >80% specificity, unless specified (a) where positive predictive value and negative predictive were also considered (~80%).

The discrepant findings across studies can be due to variability in the gold standard used to diagnose PD‐MCI and differences in patient characteristics (age, disease duration, education). One additional consideration is the cultural diversity of the samples. Previous studies do not report the ethnocultural diversity of their samples, 21 , 22 , 24 , 25 , 33 , 35 , 37 , 43 , 44 with the exception of a few studies where race was reported as 95%–100% Caucasian 23 , 26 , 45 with no report of immigration history. In our sample, although immigration status was accounted for, we did not consider the degree of acculturation in the Anglosphere group, which likely includes many second generation immigrants as they represent 28% of Toronto's population. 8 Transgenerational cultural effects are found in neuropsychological studies 7 , 46 and as populations become more culturally diverse, this line of inquiry will become increasingly important.

The sources of cultural bias are likely numerous and remain mostly elusive despite our findings with the HIHD. There is growing recognition that psychology and neurology research is ethnocentric as it is predominantly conducted in Anglosphere countries often in samples with limited diversity. 47 , 48 , 49 While basic cognitive processes are considered universal, 50 a person's culture impacts how these processes are expressed in behavior which extends to their performance on cognitive tests. 51 , 52 , 53 Culture also influences the design of cognitive tests. 54 We argue that the degree of correspondence between patients' culture of origin and that of cognitive tools may be a significant contributor to the observed bias on testing, and this may vary across tools. This could explain why people from the Anglosphere outperform people born in other regions on several tasks devised and validated in the Anglosphere, and although some experimental tasks do favor non‐Anglosphere populations, 48 , 55 , 56 these are not typically integrated in clinical screeners or standardized tests. As such, careful consideration should be taken when interpreting test performance as reflecting neurobiological mechanisms in diverse populations, and this should extend beyond performance on verbal tasks and to those fluent in English.

Our study's limitations are instructive for future research. As this is a review of clinical charts, there is variability in the test battery used across participants and between groups as some culturally‐biased tasks are often substituted when assessing diverse patients. Despite this, the rates of PD‐MCI between groups were not different. How our data was collected also varied in that the DRS‐2 was administered during the comprehensive neuropsychological assessment but the MoCA was administered during a neurology clinic visit approximately 4 months earlier. While this may generate some variability, it increases the generalizability of the findings given that the MoCA is often administered as a screener, prior to initiating a referral for neuropsychological assessment. Furthermore, the use of data collected within clinical care may be less subject to a selection bias compared to prospective trials where diverse populations tend to be under‐represented.

Second, our sample consisted solely of patients evaluated for DBS candidacy. They had longer disease duration and greater LEDD than those in comparable studies, although our MoCA AUC in the Anglosphere group is similar to that from a multi‐center study, which included our site, with non‐surgical PD patients. 25 The only other study in DBS candidates reported the same DRS‐2 diagnostic cutoff score (≤139) but seemingly stronger ROC properties (AUC 0.81). 38 Notably, this study from the Netherlands required speaking Dutch as a first language as an inclusion criterion, which likely resulted in the exclusion of immigrants.

Third, linguistic factors may contribute to performance to a greater degree than documented here. We attempted to limit the effect of English proficiency by first excluding patients assessed with interpreters, which also controlled for deviations in standardized test administration, but at the cost of reducing the generalizability of our findings to the broader immigrant population. Secondly, we also replicated our findings in a subgroup educated in English. We recognize that these approaches are coarse, but unfortunately there is no straightforward way to address this limitation as the selection of a language proficiency measure is challenging given linguistic differences across countries and regions that share a common language. As existing language measures reflect both proficiency and cultural effects, their use to equate or control for proficiency is problematic as it may eliminate or reduce the effect of interest: culture. Importantly, English proficiency is unlikely to fully explain cultural bias on testing. Notably, it cannot reconcile the significantly different ROCs between the MoCA and DRS‐2 in the International patients who completed both tests given that both instruments include verbal items such as verbal fluency, semantic reasoning, auditory attention, and verbal memory. Furthermore, we previously demonstrated and also show in the current patients' comprehensive assessment (Table S3) that scores on verbal memory measures (eg, word list and story recall) are not different between Anglosphere and International groups despite differences on classic measures of language (eg, semantic verbal fluency, naming), and demonstrate strong group differences on tasks devoid of language material (eg, Matrix Reasoning, Judgement of Line Orientation). 12 This cultural effect on non‐verbal tasks may seem counterintuitive, but is in line with the cultural neuroscience literature, which we discussed in depth previously. 12

Lastly, another linguistic variable to consider is bilingualism. Although we provide some information as to whether patients were ESL (and thus bilingual), we do not report the proportion of bilinguals in native English‐speakers, nor information on the degree of bilingualism. This may be relevant in light of research, in part conducted in Toronto, on the beneficial effect of bilingualism to executive functioning 57 , 58 and its protective effect on age‐related cognitive decline. 59 As such, an advantage in cognitive prognosis may be present in bilingual PD patients who certainly represent a larger proportion of the International group than of the Anglosphere group.

To conclude, although cognitive screeners such as the MoCA and DRS‐2 generally show good diagnostic precision in PD dementia24, 35, 45, 60, 61, 62, 63, 64 several studies recommend caution when used to diagnose PD‐MCI, 22 , 24 , 33 , 43 as the level of precision desirable to support diagnosis (sensitivity and specificity >0.80) is seldom achieved in this group. Instead, their use is advised solely for screening and triaging. Our data illustrate that such reservations are paramount when assessing patients who are first generation immigrants. In fact, the use of the MoCA is not advised in this group and the DRS‐2 should be interpreted with caution with all patients given its poor diagnostic accuracy. Together, our study and the limited literature investigating the impact of multiculturalism on cognitive assessment across clinical populations highlight the importance of developing and identifying bias‐free assessment tools, which are essential to ensure greater diagnostic accuracy in ethnoculturally diverse populations. Efforts should not be limited to the investigation of cognitive tasks, and should extend to other elements of diagnostic criteria (eg, subjective cognitive complaints), to individuals with more limited English‐proficiency, and to the relationship between culture and prognosis.

Author Roles

(1) Research Project: A. Conception, B. Organization, C. Recruitment, D. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique.

M.S.: 1A, 1B, 1D, 2A, 2C, 3A, 3B

K.C.: 2C, 3A, 3B

A.F.: 2C, 3B

R.M.: 2C, 3B

M.C.: 1A, 1B, 1D, 2A, 2B, 2C, 3A, 3B

Disclosures

Ethical Compliance Statement

This study was approved by the Research Ethics Board at University Health Network. Informed patient consent was not necessary for this work given the clinical chart review design. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Funding Sources and Conflict of Interest

No specific funding was received for this work and the authors declare that there are no conflicts of interest relevant to this work. This work was internally funded by UHN through salary support to M.S. and M.C.

Financial Disclosures for the Previous 12 Months

M.S. and K.C. declare that there are no additional disclosures to report. A.F. received honoraria from AbbVie, Abbott, Boston Scientific, Ceregate, Ipsen, Medtronic and UCB and research support from AbbVie, Boston Scientific and Medtronic; R.P.M. received honoraria from Medtronic; M.C. received honoraria from Medtronic.

Supporting information

Table S1. Number of PD patients per country of birth for each cognitive screener sample.

Click here for additional data file. (26.7KB, docx)

Table S2. Comprehensive neuropsychological assessment Note. Description of tasks used per cognitive domains, including Table S2. Mean performance of the Anglosphere and International groups on neuropsychological tests and correlations with cognitive screeners.

Click here for additional data file. (44.3KB, docx)

Table S3. Performance characteristics of the MoCA and DRS‐2 for detecting PD‐MCI in the Anglosphere and International groups across cutoff scores.

Click here for additional data file. (25.5KB, docx)

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Table S1. Number of PD patients per country of birth for each cognitive screener sample.

Click here for additional data file. (26.7KB, docx)

Table S2. Comprehensive neuropsychological assessment Note. Description of tasks used per cognitive domains, including Table S2. Mean performance of the Anglosphere and International groups on neuropsychological tests and correlations with cognitive screeners.

Click here for additional data file. (44.3KB, docx)

Table S3. Performance characteristics of the MoCA and DRS‐2 for detecting PD‐MCI in the Anglosphere and International groups across cutoff scores.

Click here for additional data file. (25.5KB, docx)

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