Prevalence of Multiple Sclerosis (MS) in Zanjan Province of Iran.

Background: The prevalence of multiple sclerosis (MS) varies in different geographical regions and has dramatically increased in Iran. Revealing the high prevalence rate draws the attention of policymakers and helps them allocate necessary resources. The aim of this study is to determine the prevalence of MS in Zanjan province of Iran.

Methods: We included all registered residents of Zanjan province with MS on the prevalence day (July 31, 2019). All cases met the McDonald criteria. All registered cases in Zanjan MS society were identified as index cases. Data regarding patient's national code, gender, age, age at the first symptom onset, city of residence, marital status, education level, occupation, ethnicity, family history of MS and the time span between symptom's onset and disease diagnosis were recorded.

Results: We identified 758 patients, 551 of whom (72.7%) were female. The mean age at the first symptom onset was 28.9 ±8.7 years old. The crude prevalence was 71.6 per 100,000 population (95% CI 66.6-76.9). The disease was most prevalent in Zanjan city (100.5 per 100,000). The gender-specific prevalence per 100,000 population was 105.4 for women (95% CI: 96.8-114.6) and 38.7 for men (95% CI: 33.6-44.1), with female to male ratio of 2.6. The standardized mortality ratio (SMR) was calculated as expected/observed for both men and women as 2.3 (207/88.2) (551/234.1).

Conclusions: Our data confirm that the MS prevalence rate is high in Zanjan province of Iran.