Is the sharp increasing trend of multiple sclerosis incidence real in Iran?

Background: Some epidemiologic studies have reported a sharp increase in multiple sclerosis (MS) incidence in different provinces in Iran. This report aimed to investigate more closely the increasing trend of MS incidence in the past 10 years in Iran. Methods: In this longitudinal study, the data for all MS patients meeting the McDonald criteria were obtained from a national registry, coordinated by the Ministry of Health (MOH). Joinpoint (JP) regression was used for time trend analysis of MS incidence and determine the optimal number of significant joinpoints. Finally, an annual percentage change (APC) in MS incidence for each segment of the trend line was estimated with 95% confidence interval. Results: The mean age of the patients and the mean annual incidence rate of MS were 30.9 +/- 1.1 and 5.3 +/- 1.9 per 100,000 population, respectively. The overall incidence rate of MS had increased significantly from 2.14 in 2006 to its peak (7.5) in 2014, per 100,000 population (APC = 12%, P < 0.001). The first JP was observed in 2011 in both male and female groups. The overall APC in the first segment was 22.6% (17.2-28.2%, p < 0.01). Besides, the corresponding APC values for males and females were 22.1% (14.7-30%, p < 0.01) and 22.5% (17.5-27.8%, p < 0.01), respectively. After 2011, the MS incidence underwent a more or less decreasing trend in both genders. Conclusion: Contrary to previous studies, the MS incidence trend in Iran was rising just before 2011, and in the recent decade, Iran has a stable rate of MS cases.