Epidemiology of Multiple Sclerosis in Torbat-e Heydarieh (Northeast of Iran) during 1982-2016.

It was believed that the risk of multiple sclerosis (MS) is associated with latitude gradient. Due to the increasing prevalence of MS in some areas around the equator such as Iran, this theory has been criticized in recent years. Since the distribution of MS in Iran is not uniform, this study was designed to describe the prevalence and incidence of MS in the northeastern area of Iran. The patients were registered in the MS center of Torbat-e Heydarieh County and all of them were living in this county during the study period (during 1 January 1982 to 31 December 2016). Data of the patients were extracted from their files in the MS center. Because of the long-term span of this study, we used different diagnosis criteria according to the files of the patients to proven case missing. In addition, population data were obtained from the website of Statistical Centre of Iran. The total number of the MS patients during the study period was 110 cases. The prevalence of the disease at the beginning and end of the research period was 0.33 (95% CI, 0.008-1.85) and 30.48 (95% CI, 25.25-37.03) patients per 100,000 persons, respectively. The incidence of the disease in this 36-year period was 1.41 (95%CI, 1.15-1.69) patients per 100,000 persons. The average age of the patients was 35.01 (95% CI, 33.37-36.65) years and the female to male ratio was 2.8:1. The prevalence of MS has been increased in the 36-year period in Torbat-e Heydarieh, especially for women. More epidemiological studies are needed to determine the factors affecting this increasing trend.