Current opinion: Racial and ethnic health disparities in multiple sclerosis: considering the social determinants of health.

PURPOSE OF REVIEW: We discuss racial and ethnic disparities in multiple sclerosis (MS), outcomes, and social determinants of health (SDoH). We also provide essential considerations needed to bridge the gap in inequalities, including broader representation of racial and ethnic people in clinical trials and research in general and the inclusion of better measures of living conditions. RECENT FINDINGS: The incidence and prevalence of MS have become more diverse in the USA. There is increased recognition that racial and ethnic health disparities and inequities exist due to adverse social conditions. Clinical trials have failed to be inclusive and diverse. Training in health disparity is an essential priority of funding sources, and designing clinical trials that consider the barriers these populations face can close significant gaps. SUMMARY: The incidence, prevalence, and awareness of MS have seen an incline in diverse racial and ethnic populations. Health disparities exist in MS with Black, Hispanic, and indigenous populations appearing to have worse outcomes. SDoH play a significant role in causing these health disparities. Accessibility to clinical trials and treatment are barriers these populations face. Strategic and earnest interventions considering SDoH are critically needed to develop solutions that collectively improve health and MS care for all.

Race and ethnicity in multiple sclerosis phase 3 clinical trials: A systematic review.

BACKGROUND: Distinctive differences in multiple sclerosis (MS) have been observed by race and ethnicity. We aim to (1) assess how often race and ethnicity were reported in clinical trials registered on ClinicalTrials.gov, (2) evaluate whether the population was diverse enough, and (3) compare with publications. METHODS: We included phase 3 clinical trials registered with results on ClinicalTrials.gov between 2007 and 2023. When race and/or ethnicity were reported, we searched for the corresponding publications. RESULTS: Out of the 99 included studies, 56% reported race and/or ethnicity, of which only 26% of those primarily completed before 2017. Studies reporting race or ethnicity contributed to a total of 33,891 participants, mainly enrolled in Eastern Europe. Most were White (93%), and the median percentage of White participants was 93% (interquartile range (IQR) = 86%-98%), compared to 3% for Black (IQR = 1%-12%) and 0.2% for Asian (IQR = 0%-1%). Four trials omitted race and ethnicity in publications and even when information was reported, some discrepancies in terminology were identified and categories with fewer participants were often collapsed. CONCLUSION: More efforts should be done to improve transparency, accuracy, and representativeness, in publications and at a design phase, by addressing social determinants of health that historically limit the enrollment of underrepresented population.

Ethnic and Socioeconomic Associations with Multiple Sclerosis Risk.

OBJECTIVE: Epidemiological research in multiple sclerosis (MS) has mainly been performed in socioeconomically and ethnically limited populations; influences on MS risk have not been studied in prospectively collected non-White populations. We set out to study the influence of previously described MS risk factors in an ethnically diverse population. METHODS: A nested case-control study was created using primary care records of >1 million individuals, >50% of whom identify as Black, Asian, and Minority Ethnic (BAME). MS cases were compared to an age- and sex-matched control cohort (1:4), and to a large unmatched cohort. Odds ratios (ORs) of disease were determined according to exposure of interest, and a multivariate model including all exposures was created. Potential pairwise interactions were considered where both indicated a significant effect. RESULTS: A total of 1,344 confirmed MS cases were included. MS OR in blacks aged <40 years was 1.15 (95% confidence interval [CI] = 0.81-1.62) compared to whites. MS odds in BAME current (OR = 1.71, 95% CI = 1.24-2.31) and ex-smokers (OR = 2.83, 95% CI = 2.14-3.72) were considerably higher than in Whites (OR = 1.09, 95% CI = 0.88-1.34; OR = 1.44, 95% CI = 1.19-1.74, respectively). Prior infectious mononucleosis was associated with increased odds of MS in Blacks (OR = 4.94, 95% CI = 1.23-17.89). An increase in MS odds was seen in the least-deprived quintile (OR = 2.46, 95% CI = 1.40-4.24), but no effect across deprived quintiles was seen. INTERPRETATION: This cohort provides novel data on factors potentially driving MS susceptibility in a diverse population, one-third of whom live in poverty. Environmental exposures have differential risk across ethnicity. ANN NEUROL 2020;87:599-608.

Race and ethnicity on MS presentation and disease course.

Multiple sclerosis (MS) has a strong racial and ethnic component and disproportionately affects whites of European background. Recent incidence reports suggest an increasing rate of MS among African Americans compared with whites. Despite this recent increase in MS in African Americans, Hispanics and Asians are significantly less likely to develop MS than whites of European ancestry. MS-specific mortality trends demonstrate distinctive disparities by race/ethnicity and age, suggesting that there is an unequal burden of disease. Inequalities in health along with differences in clinical characteristics that may be genetic, environmental, and social in origin may be contributing to disease variability and be suggestive of endophenotypes. The overarching goal of this review was to summarize the current understanding on the variability of disease that we observe in selected racial and ethnic populations: Hispanics and African Americans. Future challenges will be to unravel the genetic, environmental, and social determinants of the observed racial/ethnic disparities.

Feasibility of Using a Nationally Representative Telephone Survey to Monitor Multiple Sclerosis Prevalence in the United States.

BACKGROUND: Multiple sclerosis (MS) is the most common chronic neurologic disease of young adults, placing a heavy burden on patients, families, and the healthcare system. Ongoing surveillance of the incidence and prevalence of MS is critical for health policy and research, but feasible options are limited in the United States and many other countries. We investigated the feasibility of monitoring the prevalence of MS using a large national telephone survey of the adult US population. METHODS: We developed questions to estimate the lifetime prevalence and age of onset of MS using the US-based Behavioral Risk Factor Surveillance System (BRFSS) and piloted these questions in 4 states (MN, RI, MD, and TX). There was a total of 45,198 respondents aged 18 years and above. Analyses investigated individual state and combined prevalence estimates along with health-related comorbidities and limitations. MS prevalence estimates from the BRFSS were compared to estimates from multi-source administrative claims and traditional population-based methods. RESULTS: The estimated lifetime prevalence of self-reported MS (per 100,000 adults) was 682 (95% CI 528-836); 384 (95% CI 239-529) among males and 957 (95% CI 694-1,220) among females. Estimates were consistent across the 4 states but much higher than recently published estimates using population-based administrative claims data. This was observed for both national results and for MS prevalence estimates from other studies within specific states (MN, RI, and TX). Prevalence estimates for Caucasian, African American, and Hispanic respondents were 824, 741, and 349 per 100,000 respectively. Age and sex distributions were consistent with prior epidemiologic reports. Comorbidity and functional limitations were more pronounced among female than male respondents. CONCLUSIONS: While yielding higher overall MS prevalence estimates compared to recent studies, this large-scale self-report telephone method yielded relative prevalence estimates (e.g., prevalence patterns of MS by sex, age, and race-ethnicity) that were generally comparable to other surveillance approaches. With certain caveats, population-based telephone surveys may eventually offer the ability to investigate novel disease correlates and are relatively feasible, and affordable. Further work is needed to create a valid question set and methodology for case ascertainment before this approach could be adopted to accurately estimate MS prevalence.

Differential expression of STAT3 gene and its regulatory long non-coding RNAs, namely lnc-DC and THRIL, in two eastern Iranian ethnicities with multiple sclerosis.

OBJECTIVE: Genome-wide association studies (GWASs) revealed that variants of STAT3 are associated with multiple sclerosis (MS) risk. There are several studies showing the effect of ethnicity and genetic background on the characteristics of MS. Here, we aimed to investigate STAT3 gene expression status along with its two regulatory long non-coding RNAs, lnc-DC and THRIL, in order to compare the expression of these target genes among two different ethnicities in the east of Iran. METHODS: A case-control study was performed between two groups of MS populations in east of Iran. We recruited individuals with Kurdish ethnicity from North Khorasan and Sistani ethnicity from southeast of Iran. The peripheral blood mononuclear cells were obtained from all participants, and total RNA was extracted. The gene expression of the selected genes was evaluated by qPCR. RESULTS: The expression of THRIL in North Khorasan MS patients was significantly higher than controls (P = 0.03). The results of simultaneous analysis of expression of the target genes (STAT3, THRIL, and lnc-DC) in both ethnic groups failed to show any significant difference between the MS patients and controls (P > 0.05). In addition, the expression of STAT3 and THRIL genes in Sistani MS patients was statistically meaningful lower than healthy controls (P < 0.05). CONCLUSION: To our knowledge, this is the first study that compared the expression of the STAT3 gene and its regulatory molecules between two ethnic groups of Iranian MS patients. We suggested that STAT3 and its associated molecules might be differentially expressed and regulated in MS patients with different genetic background.

The higher prevalence of multiple sclerosis among Iranian Georgians; new clues to the role of genetic factors.

BACKGROUND: Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) with varied prevalence rates among populations with different ethnic backgrounds. Therefore, studies done on minorities have shed more light on the risk factors. OBJECTIVE: Comparing MS prevalence in Georgian-based population immigrated to Iran and other Iranians. METHODS: All records of MS patients enrolled in the two biggest registry systems were investigated. All of the patients born in Fereydunshahr and Buin va Miandasht (2 biggest cities with Georgian immigrants) were interviewed and their baseline characteristics were obtained. Patients' ethnic background information were obtained from the Iran National organization for civil registration. RESULTS: Forty-one patients from Fereydunshahr and Buin va Miandasht were identified. The population of the two cities combined and the estimated number of Georgian-based patients in both cities were reported 59817 and 12000, respectively. The estimated ethnicity-adjusted prevalence among the Georgian-based individuals was 2.3 times higher than the non-Georgian ones. Baseline characteristics were also compared. CONCLUSION: There was a higher prevalence of multiple sclerosis among the Georgian minority of Isfahan. Due to the ethnic background of the Georgian minority, genetic risk factors should be considered more as a risk factor.

A nationwide epidemiological study on the prevalence of multiple sclerosis and neuromyelitis optica spectrum disorder with important multi-ethnic differences in Malaysia.

OBJECTIVES: This study looked at observed crude prevalence/incidence of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) in Malaysia and identified any inter-ethnic differences for MS/NMOSD. METHODS: This was a nationwide tertiary hospital-based retrospective cross-sectional study using the capture-recapture method. It looked at the estimated crude prevalence of confirmed MS and NMOSD and annual incidence on 29 December 2017. Recapture of data was done between February and March 2018 on 1 March 2018. Public and referring private institutions were accessed. RESULTS: The survey identified 767 MS and 545 NMOSD subjects, with crude prevalence rates of 2.73 per 100,000 (95% confidence interval (CI): 2.53; 2.92 per 100,000 population) and 1.94 per 100,000 (95% CI: 1.77; 2.10 per 100,000 population) with observed crude annual incidence of 0.55 (95% CI: 0.43; 0.58) for MS and 0.39 per 100,000 (95% CI: 0.35; 0.47) for NMOSD. The MS:NMOSD ratios were 1.4:1.0. The capture-recapture method revealed 913 MS (95% CI: 910; 915.9) and 580 (95% CI: 578.8; 581.2) NMOSD with prevalence per 100,000 of 3.26 (95% CI: 3.05; 3.47) and 2.07 (95% CI: 1.90; 2.24), respectively. In the MS group, 59.4% were Malay, 16.6% Chinese, 20.5% Indian, and 3.5% were from indigenous groups. In the NMOSD group, 47.3% were Malay, 46.9% Chinese, 3.5% Indian, and 2.3% were from other indigenous groups. The ratio of NMOSD to MS among the Chinese was 2:1, but the ratio of MS to NMOSD among the Malays was 1.8:1, and that in Indians was 8.3:1. CONCLUSION: There is a modest increase in the prevalence of MS and NMOSD in Malaysia with inter-ethnic differences for MS/NMOSD.

Prevalence and Incidence of Multiple Sclerosis in the City of Biancavilla.

BACKGROUND: It is common that the epidemiology of multiple sclerosis (MS) varies with geography and ethnicity. Recent studies show a continuous growth of incidence and prevalence in Sicily, despite the controversial "latitude gradient theory." OBJECTIVES: The aim of our study is to ascertain incidence and prevalence rates of MS in the city of Biancavilla, Sicily, Southern Italy. METHOD: Case ascertainment approach and a clinical database collecting data of MS cases to Biancavilla, according to McDonald 2011 and Thompson 2018 criteria, from 1992 to 2018, have been used to the study. We further collected information regarding the familiarity of patients with Mesothelioma, highly incident in this geographic area. RESULTS: The results showed an increase of the mean annual incidence for the period 2012-2018 (16.8/100,000) compared to 1992-1996 (4.5/100,000), and a standardized incidence ratio of 1.41 (95% CI 0.74-2.45). On December 31, 2018, 70 patients suffering from definite MS and living in Biancavilla yielded a crude prevalence of 292.3 per 100,000 (198.2/100,000 for men; 380.7/100,000 for women) with a standardized morbidity ratio of 2.3 (95% CI 1.8-2.9). CONCLUSIONS: Our data confirmed Biancavilla is an area at high risk for MS, ascribable to increased survival, improved ascertainment, or maybe related to a genetic or environmental risk. At the time, any relation with mesothelioma was excluded.

Brain and retinal atrophy in African-Americans versus Caucasian-Americans with multiple sclerosis: a longitudinal study.

On average, African Americans with multiple sclerosis demonstrate higher inflammatory disease activity, faster disability accumulation, greater visual dysfunction, more pronounced brain tissue damage and higher lesion volume loads compared to Caucasian Americans with multiple sclerosis. Neurodegeneration is an important component of multiple sclerosis, which in part accounts for the clinical heterogeneity of the disease. Brain atrophy appears to be widespread, although it is becoming increasingly recognized that regional substructure atrophy may be of greater clinical relevance. Patient race (within the limitations of self-identified ancestry) is regarded as an important contributing factor. However, there is a paucity of studies examining differences in neurodegeneration and brain substructure volumes over time in African Americans relative to Caucasian American patients. Optical coherence tomography is a non-invasive and reliable tool for measuring structural retinal changes. Recent studies support its utility for tracking neurodegeneration and disease progression in vivo in multiple sclerosis. Relative to Caucasian Americans, African American patients have been found to have greater retinal structural injury in the inner retinal layers. Increased thickness of the inner nuclear layer and the presence of microcystoid macular pathology at baseline predict clinical and radiological inflammatory activity, although whether race plays a role in these changes has not been investigated. Similarly, assessment of outer retinal changes according to race in multiple sclerosis remains incompletely characterized. Twenty-two African Americans and 60 matched Caucasian Americans with multiple sclerosis were evaluated with brain MRI, and 116 African Americans and 116 matched Caucasian Americans with multiple sclerosis were monitored with optical coherence tomography over a mean duration of 4.5 years. Mixed-effects linear regression models were used in statistical analyses. Grey matter (-0.9%/year versus -0.5%: P =0.02), white matter (-0.7%/year versus -0.3%: P =0.04) and nuclear thalamic (-1.5%/year versus -0.7%/year: P =0.02) atrophy rates were approximately twice as fast in African Americans. African Americans also exhibited higher proportions of microcystoid macular pathology (12.1% versus 0.9%, P =0.001). Retinal nerve fibre layer (-1.1% versus -0.8%: P =0.02) and ganglion cell+ inner plexiform layer (-0.7%/year versus -0.4%/year: P =0.01) atrophy rates were faster in African versus Caucasian Americans. African Americans on average exhibited more rapid neurodegeneration than Caucasian Americans and had significantly faster brain and retinal tissue loss. These results corroborate the more rapid clinical progression reported to occur, in general, in African Americans with multiple sclerosis and support the need for future studies involving African Americans in order to identify individual differences in treatment responses in multiple sclerosis.

Replication study of GWAS risk loci in Greek multiple sclerosis patients.

OBJECTIVES: To validate in an ethnically homogeneous Greek multiple sclerosis (MS) cohort, genetic risk factors for the disease, identified through a number of previous multi-ethnic genome-wide association studies (GWAS). METHODS: A total of 1228 MS cases and 1014 controls were recruited in the study, from 3 MS centers in Greece. We genotyped 35 susceptibility SNPs that emerged from previous GWAS or meta-analyses of GWAS. Allele and genotype single locus regression analysis, adjusted for gender and site, was performed. Permutation testing was applied to all analyses. RESULTS: Six polymorphisms reached statistical significance (permutation p value < 0.05). In particular, rs2760524 of LOC105371664, near RGS1 (permutation p value 0.001), rs3129889 of HLA-DRA, near HLA-DRB1 (permutation p value < 1.00e-04), rs1738074 of TAGAP (permutation p value 0.007), rs703842 of METTL1/CYP27B1 (permutation p value 0.008), rs9596270 of DLEU1 (permutation p value < 1.00e-04), and rs17445836 of LincRNA, near IRF8 (permutation p value 0.001) were identified as susceptibility risk factors in our group. CONCLUSION: The current study replicated a number of GWAS susceptibility SNPs, which implies that some similarities between the examined Greek population and the MS genetic architecture of the GWAS populations do exist.

A comparison of brain magnetic resonance imaging lesions in multiple sclerosis by race with reference to disability progression.

BACKGROUND: We compared the magnetic resonance imaging (MRI) features between Japanese and Caucasian patients with multiple sclerosis (MS), and identified the relationships between MRI features and disability. METHODS: From the baseline data of phase II fingolimod trials, 95 Japanese and 246 Caucasian relapsing-remitting MS patients were enrolled. The number, volume, and distribution of brain MRI lesions were evaluated using T2-weighted (T2W) images. Cross-sectional total normalized brain volume (NBV), normalized cortical gray matter volume, normalized deep gray matter volume (NDGMV), normalized white matter volume (NWMV), and normalized thalamic volume were measured. RESULTS: Japanese patients had significantly lower Expanded Disability Status Scale (EDSS) scores than Caucasian patients (mean 2.0 vs. 2.3, p = 0.008), despite a similar disease duration. Japanese patients showed a trend towards fewer T2W-lesions (median 50 vs. 65, p = 0.08) and significantly lower frequencies of cerebellar and parietal lobe lesions (p = 0.02 for both) than Caucasian patients. There were no differences in T2W-lesion volume between races, whereas Japanese patients had a significantly larger T2W-lesion volume per lesion compared with Caucasian patients (median 140 mm3 vs. 85 mm3, p < 0.0001). T2W-lesion volumes were positively correlated with EDSS scores in Japanese patients (p < 0.0001). In both races, NBV, normalized cortical gray matter volume, NDGMV, and thalamic volume were negatively correlated with disease duration and EDSS scores (p < 0.01 for all). NWMV was negatively correlated with disease duration and EDSS scores only in Caucasian patients (p = 0.03 and p = 0.004, respectively). NBV, NDGMV, NWMV, and thalamic volume were consistently smaller in Japanese compared with Caucasian patients throughout the entire examined disease duration (p = 0.046, p = 0.01, p = 0.005, and p = 0.04, respectively). Japanese patients had a significantly faster reduction in NDGMV (p = 0.001), particularly for thalamic volume (p = 0.001), with disease duration compared with Caucasian patients. CONCLUSIONS: Gray matter atrophy is a common denominator for disability in Japanese and Caucasian patients. Additional contributory factors for disability include T2W-lesion volume in Japanese patients and white matter atrophy in Caucasian patients. Less frequent parietal and cerebellar involvement with fewer T2W-lesions may underlie milder disability in Japanese patients.

Racial disparities in Medicaid home and community-based service utilization and expenditures among persons with multiple sclerosis.

BACKGROUND: Medicaid home and community-based services (HCBS) provide services such as personal care, nursing, and home-delivered meals to aging adults and individuals with disabilities. HCBS are available to people across racial and ethnic groups, yet racial disparities in Medicaid HCBS utilization and expenditures have been understudied. Individuals with multiple sclerosis (MS) may be particularly impacted by HCBS, as nearly one-third requires assistance at home. The present study examined whether disparities exist in Medicaid HCBS utilization and expenditures among HCBS users with MS. METHODS: We used secondary data to conduct a retrospective cohort analyses including 7550 HCBS recipients with MS. Demographic data was obtained from the Medicaid Analytic eXtract Personal Summary file, Medicaid HCBS service utilization and expenditures were obtained from the Other Therapy file, and comorbidities from the Medicare Chronic Condition Warehouse. Univariate and bivariate statistics were used to describe the sample and provide comparisons of characteristic by race. Logistic regression predicted the likelihood of using HCBS type and gamma regression was used to predict Medicaid HCBS expenditures. RESULTS: Black HCBS users were younger, more likely to be female, and were more impaired than Whites. Multivariate analyses showed that Blacks were less likely to receive case management, equipment, technology and modification services, and nursing services compared to Whites. Additionally, Black men had the lowest Medicaid HCBS expenditures, while White men had the highest. CONCLUSIONS: Findings shed light on disparities among HCBS users with MS. As Blacks are already disproportionately affected by MS, these results reveal target areas for future research. Future work should examine the factors that contribute to these disparities, as well as determine the extent to which these inequities impact outcomes such as hospitalizations and nursing home admissions.

Hispanic Americans and African Americans with multiple sclerosis have more severe disease course than Caucasian Americans.

Whether disease course in Hispanic Americans (HA) with multiple sclerosis (MS) is different from Caucasian Americans (CA) or African Americans (AA) is unknown. We compared MS severity in the three main ethnic populations in our tertiary MS clinics using disease duration-adjusted rank score of disability: Patient-Derived Multiple Sclerosis Severity Score (P-MSSS). The age- and gender-adjusted P-MSSS was significantly higher in HA (3.9 ± 2.6) and AA (4.5 ± 3.0) compared to CA (3.4 ± 2.6; p < 0.0001 for both). Adjusting for insurance did not change these results. These findings suggest that HA, as AA, have more rapid disability accumulation than CA.

The killer immunoglobulin-like receptor KIR3DL1 in combination with HLA-Bw4 is protective against multiple sclerosis in African Americans.

We investigated the role of the KIR loci and their HLA class I ligands in a large cohort of African American multiple sclerosis (MS) patients (N=907) and controls (N=1456). No significant differences in carrier frequencies for any KIR locus or haplotype were observed between cases and controls. However, examination of KIR in the context of their cognate HLA ligands revealed a strong protective effect for KIR3DL1 in combination with HLA-A and -B alleles bearing the Bw4 motif (P=10(-8); odds ratio (OR)=0.60, confidence interval (CI)=0.50-0.71) and the Bw4 ligand alone (P<10(-6); OR=0.63, CI=0.53-0.75). The observed effect cannot be explained by either a specific HLA-B allele or by linkage disequilibrium with HLA-DRB1 or HLA-A. The protective effect was observed only in individuals who were not positive for the MS risk allele HLA-DRB1*15:01 (P<10(-6); OR=0.61, CI=0.51-0.74). Our study, the first investigation of KIR and MS in African Americans, confirms and refines previous findings in a European cohort.

Retinal damage and vision loss in African American multiple sclerosis patients.

OBJECTIVE: To determine whether African American (AA) multiple sclerosis (MS) patients exhibit more retinal damage and visual impairment compared to Caucasian American (CA) MS patients. METHODS: A total of 687 MS patients (81 AAs) and 110 healthy control (HC) subjects (14 AAs) were recruited at 3 academic hospitals between 2008 and 2012. Using mixed effects regression models, we compared high- and low-contrast visual acuity (HCVA and LCVA) and high-definition spectral domain optical coherence tomography measures of retinal architecture between MS patients of self-identified AA and CA ancestry. RESULTS: In HCs, baseline peripapillary retinal nerve fiber layer (RNFL) thickness was 6.1µm greater in AAs (p = 0.047), whereas ganglion cell/inner plexiform layer (GCIP) thickness did not differ by race. In MS patients, baseline RNFL did not differ by race, and GCIP was 3.98µm thinner in AAs (p = 0.004). AAs had faster RNFL and GCIP thinning rates compared to CAs (p = 0.004 and p = 0.046, respectively). AA MS patients had lower baseline HCVA (p = 0.02) and worse LCVA per year of disease duration (p = 0.039). Among patients with an acute optic neuritis (AON) history, AAs had greater loss of HCVA than CA patients (p = 0.012). INTERPRETATION: This multicenter investigation provides objective evidence that AA MS patients exhibit accelerated retinal damage compared to CA MS patients. Self-identified AA ancestry is associated with worse MS-related visual disability, particularly in the context of an AON history, suggesting a more aggressive inflammatory disease course among AA MS patients or a subpopulation therein.

Prevalence of multiple sclerosis in Iranian emigrants: review of the evidence.

Iran has the highest prevalence of multiple sclerosis (MS) in the Middle East and Asia. Rate of emigration has been significantly raised among Iranians and though, multiple studies have been published on prevalence of MS among Iranian emigrants. Here we systematically reviewed these publications. We performed a comprehensive literature search was performed on April 30, 2015 in data bases of MEDLINE, EMBASE, Scopus and Google Scholar for the terms 'multiple sclerosis', 'incidence', 'prevalence', 'epidemiology', 'migration', 'emigrant', 'immigrant', 'Iran', 'Parsis' and 'Persian'. Study location, prevalence day or period, and age of at disease onset were recorded for all the included publications. Nine publications from Sweden, Canada, Norway, UK, and India were included. Only three reported age-adjusted prevalence and six reported age of disease onset. MS prevalence among Iranian emigrants varied from 21 per 100,000 people in Bombay, India in 1985 to 433 per 100,000 people in British Columbia, Canada in 2012. Five studies reported the prevalence in the region of interest, ranging from 1.33 in Bombay, India to 240 in British Columbia, Canada. Five studies also reported the prevalence of MS in the population of the destination country, and in all of them, the prevalence of MS was higher in Iranian immigrants compared to native people. Prevalence studies performed in Iran and also on Iranian emigrants indicate roles for both genetic and environmental factors in MS susceptibility. Data might indicate that living in a high-risk area increases the susceptibility to MS.

Genetic contribution to multiple sclerosis risk among Ashkenazi Jews.

BACKGROUND: Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, with a strong genetic component. Over 100 genetic loci have been implicated in susceptibility to MS in European populations, the most prominent being the 15:01 allele of the HLA-DRB1 gene. The prevalence of MS is high in European populations including those of Ashkenazi origin, and low in African and Asian populations including those of Jewish origin. METHODS: Here we identified and extracted a total of 213 Ashkenazi MS cases and 546 ethnically matched healthy control individuals from two previous genome-wide case-control association analyses, and 72 trios (affected proband and two unaffected parents) from a previous genome-wide transmission disequilibrium association study, using genetic data to define Ashkenazi. We compared the pattern of genetic risk between Ashkenazi and non-Ashkenazi Europeans. We also sought to identify novel Ashkenazi-specific risk loci by performing association tests on the subset of Ashkenazi cases, controls, probands, and parents from each study. RESULTS: The HLA-DRB1*15:01 allele and the non-HLA risk alleles were present at relatively low frequencies among Ashkenazi and explained a smaller fraction of the population-level risk when compared to non-Ashkenazi Europeans. Alternative HLA susceptibility alleles were identified in an Ashkenazi-only association study, including HLA-A*68:02 and one or both genes in the HLA-B*38:01-HLA-C*12:03 haplotype. The genome-wide screen in Ashkenazi did not reveal any loci associated with MS risk. CONCLUSION: These results suggest that genetic susceptibility to MS in Ashkenazi Jews has not been as well established as that of non-Ashkenazi Europeans. This implies value in studying large well-characterized Ashkenazi populations to accelerate gene discovery in complex genetic diseases.

The burden of multiple sclerosis variants in continental Italians and Sardinians.

BACKGROUND: Recent studies identified > 100 non-HLA (human leukocyte antigen) multiple sclerosis (MS) susceptibility variants in Northern European populations, but their role in Southern Europeans is largely unexplored. OBJECTIVE: We aimed to investigate the cumulative impact of those variants in two Mediterranean populations: Continental Italians and Sardinians. METHODS: We calculated four weighted Genetic Risk Scores (wGRS), using up to 102 non-HLA MS risk variants and 5 HLA MS susceptibility markers in 1691 patients and 2194 controls from continental Italy; and 2861 patients and 3034 controls from Sardinia. We then assessed the differences between populations using Nagelkerke's R(2) and the area under the Receiver Operating Characteristic (ROC) curves. RESULTS: As expected, the genetic burden (mean wGRS value) was significantly higher in MS patients than in controls, in both populations. Of note, the burden was significantly higher in Sardinians. Conversely, the proportion of variability explained and the predictive power were significantly higher in continental Italians. Notably, within the Sardinian patients, we also observed a significantly higher burden of non-HLA variants in individuals who do not carry HLA risk alleles. CONCLUSIONS: The observed differences in MS genetic burden between the two Mediterranean populations highlight the need for more genetic studies in South Europeans, to further expand the knowledge of MS genetics.