The Effect of Month of Birth on Multiple Sclerosis: A Sase-Control Study in Northeast Iran.

Background: Multiple sclerosis (MS) is an autoimmune and multi-factorial (e.g. environmental, genetic) disease. We conducted a case-control study of month and season of birth (MOB and SOB) and multiple sclerosis (MS) risk in the east of Iran.

Methods: The MS patients registered in Mashhad and Torbat Heydariyeh MS Society until 20 March 2018 was compared with the MOB and SOB in the healthy population during 1988 to 2018. Case group was matched for age, sex and place of residence with the control group. Differences in the distributions of MOB and SOB between the patients and the control groups were assessed using the chi-square test.

Results: There were 2,160 MS patients in case group and 2,245 in control group. There was a significant relationship between MOB ans SOB with the risk of MS (P less than 0.05). Analysis showed a significant (p less than 0.01) peak in the MOB during Mar-Apr (OR is equal to 1.60), May-Jun (OR is equal to 1.30) and Aug-Sep (OR is equal to 2.42).

Conclusion: The findings show a relationship between MOB and SOB as risk factor for MS in Northeast Iran. Further studies are needed to confirm this result. Keyword: Multiple sclerosis, Month of Birth, seasonality, case-control, Iran.