The relationship between ethnicity and Multiple Sclerosis characteristics in the United Kingdom: a UK MS Register study

Previous studies have suggested differences in Multiple Sclerosis severity between individuals from different ethnic backgrounds. However, these measures of severity have been focussed on markers of physical disability derived from clinical records. We sought to determine the association between self-reported ethnicity and Multiple Sclerosis severity across a range of domains in a prospective cohort based in the United Kingdom. Data were obtained from the United Kingdom Multiple Sclerosis Register, a longitudinal cohort study of >20,000 persons with Multiple Sclerosis. We examined the association between self-reported ethnic background and age at onset, site of onset, and a variety of participant-reported severity measures: the Expanded Disability Status Scale, the Multiple Sclerosis Impact Scale, the Multiple Sclerosis Walking Scale, the Fatigue Severity Scale, and the EuroQol-5D quality of life index. We used multivariable linear regression models adjusted for age, sex, and Multiple Sclerosis subtype (Primary Progressive vs other). We explored the association between ethnicity and impact of Multiple Sclerosis using Cox proportional hazards models to assess the rate of disability progression. Data were available for 14,264 people with Multiple Sclerosis, including 380 participants from self-reported Black (n=151) or South Asian (n=229) ethnic backgrounds. Age at Multiple Sclerosis onset and diagnosis was lower in the participants of South Asian (median onset 31.0) and Black (median onset 33.0) ethnicity compared with White ethnicity (median onset 35.0, n=13,884). We found no statistically-significant evidence for an association between ethnic background on baseline Multiple Sclerosis severity scores in any of the scores tested across a range of sensitivity analyses. In longitudinal analysis, we did not find evidence for an impact of ethnicity on five-year risk of disability progression. In this large, ethnically-diverse Multiple Sclerosis cohort with universal access to healthcare, we find no association between ethnic background per se and MS severity, whether in cross-sectional or longitudinal analyses. These findings suggest that other factors, such as socioeconomic status and structural inequalities, may explain previous findings of heterogeneity between ethnic groups. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement BMJ is funded by an Medical Research Council (MRC) Clinical Research Training Fellowship (CRTF) jointly supported by the UK MS Society (BMJ; grant reference: MR/V028766/1). This work was carried out at the Centre for Preventive Neurology Unit at Queen Mary University of London, which is partly funded by Barts Charity. The UK MS Register is funded by the UK MS Society. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The UK Multiple Sclerosis Register has research ethics approval from South West Central Bristol Research Ethics Committee initially as 16/SW/0194 currently 21/SW/0085. This project was approved by the UKMSR Scientific Steering Committee. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All analyses were conducted in R version 4.1.3 within the UKMSR secure research environment (UKSERP)27. All code used in these analyses is available at https://benjacobs123456.github.io/ukmsr_ethnicity/. Access to UKMSR data is open to all researchers on application. Details of how to apply for the data can be found here: https://ukmsregister.org/Research/WorkingWithUs.