Parental ethnicity associated with risk for multiple sclerosis: A population-based incident case-control study in Iran

Background: The epidemiology of multiple sclerosis (MS) includes a consideration of geography and population ethnicity. To determine whether there is any association between ethnicity and risk of MS in a multiethnic, population-based case-control study. Methods: We conducted a population-based case-control of 547 incident MS cases and 1057 healthy controls between August 2013 and February 2015, Tehran, a multi-ethnic city. The patients were identified and enrolled through the Iranian MS Society. Case status was confirmed by a panel of MS specialists beside of 2010 McDonald criteria. Controls were selected through random digit dialing. A logistic regression model was applied to estimate the odds ratios (95% CI) adjusted for age, sex, tobacco smoking and socioeconomic status. Results: The risk of MS for Kurd, Turk and Fars ethnicities was apparently smaller compared to one specific ethnic background (Lor); OR 0.36 (0.15-0.86) for Kurd, OR 0.42 (0.24-0.74) for Turk and OR 0.53 (0.31-0.89) for Fars. Heterogeneity in parental ethnicity of common ethnic groups was significantly associated with increased risk of MS OR 1.61 (1.13-2.29). All associations remained after adjustment for relevant confounders. Conclusions: MS was unequally distributed in the ethnic groups. Moreover, heterogeneity in parental ethnicity seems to be a risk factor for MS.