Epidemiology of multiple sclerosis in the Sultanate of Oman: A hospital based study

Background: The prevalence of multiple sclerosis (MS) has been changing not only globally but also in individual countries. We aim to estimate the prevalence of MS in the Omani population over the period from 2006-2019 as well as the incidence between 2015-2018. Methods: This is a retrospective observational hospital-based study. All MS patients diagnosed, as per the revised McDonald criteria, over the period from June 2006 and until May 2019, had their information reviewed for age at disease onset, gender and year of diagnosis. We obtained the population of Oman from the national census data. Results: A total of 422 patients were diagnosed with MS during the study period and the population of Oman as per the 2019 census data was 2,652,199. The estimated crude prevalence was 15.9 (95% confidence interval: 14.4 - 17.5) per 100,000 and the female to male ratio was 2.17:1. The mean age at disease onset was 27.3 ± 7.7 (range: 9 - 59) years in which 83% of the patients had the first clinical manifestation at the age of 19 - 40 years, while only 9% had a disease onset at <19 years. The annual incidence increased from 1.00 case per 100,000 in 2015 to 1.38 cases per 100,000 in 2018. Conclusion: The prevalence of MS in the Omani population is 15.9 per 100,000 placing Oman as a medium risk zone.