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

Abstract 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.