A national registry-based study of ethnic differences in people with multiple sclerosis in Iran.

The relationship between MS and ethnicity has been understudied in the Middle East compared to the United States and Europe. As Iran as the highest prevalence of MS in the Middle East, we decided to investigate the demographic and clinical differences in people with MS (pwMS) from major ethnicities Iran. In a cross-sectional study using data from National Multiple Sclerosis Registry in Iran. PwMS from six provinces were chosen and interviewed for determining their ethnicity. Persians (Fars), Kurds, Lurs, Azeris and Arabs with a clear ethnic background were included. Recorded data from the registry was used to compare the demographic and clinical features. A total of 4015 pwMS (74.2% female) were included in the study with an average age of 36.76 ± 9.68 years. Persians and Kurds had the highest percentage of pwMS in youngest and oldest age groups, respectively, with 2.9% and 5.7% (p<0.01). The highest average age of onset was seen in Persians (29.47 ± 8.89) and the lowest observed in Mazandaranis (26.82 ± 7.68, p<0.01). Azeris and Kurds had the highest proportions of pwMS diagnosed <18 and >55, at rates of 12% and 1.6%, respectively (p<0.01). There were statistically significant differences in distribution of phenotypes (p<0.01) and time to progression to secondary progressive MS (p<0.01) such that Persians had the highest rate of clinically isolated syndrome (CIS) at 19.3% and Arabs had highest rates of relapsing-remitting MS (86.2%) and secondary progressive MS (16.4%). Lurs, Azeris and Mazandaranis had significantly more patients progressing to secondary-progressive MS <5 years from diagnosis (p<0.01). There was a significant difference in number of relapses between the ethnicities (p<0.01) with Lurs having the highest proportion of participants reporting >4 relapses with 23.0% and Azeris having the highest percentage of pwMS reporting no relapse (53.0%). Kurds had the highest Expanded Disability Status Scale (EDSS) average at 2.93 ± 1.99 and Lurs had the lowest with 1.28 ± 1.25 (p<0.01). The differences in prevalence of positive family history for the whole cohort between ethnicities were significant (P=0.02), ranging from 12.8% in Kurds to 19.6% in Persians. We found Persians to have higher rates of pediatric MS and higher rates of CIS. Kurds and Lurs had higher and lower EDSS scores, respectively. Lurs and Persian had higher annual relapse rates. We also found lower rates of SPMS among Arabs and earlier progression to SPMS in Lurs, Azeris and Mazandaranis. Such differences highlight the importance of the potential role of ethnicities in diagnosis and prognosis of MS, especially considering their observation within the geographical limits of a single country.

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Declaration of Competing Interest The authors declare no conflict of interest.