Childhood infections affect timing of multiple sclerosis onset in adults: EnvIMS study

Background and aims: Since early-life challenge o f the immune system can affect the risk of later development of autoimmune diseases, childhood infections have been suggested as risk factors/triggers for multiple sclerosis (MS). Except for Epstein Barr Virus, the role of other infectious agents in the pathogenesis of MS remains poorly understood. We aimed at investigating the association between MS and exposure to childhood infections and its role on timing of disease onset. Methods: We analyzed data collected within the EnvIMS study, a multinational case-control population-based study, including information on measles, rubella, mumps, and chickenpox of Italian and Norwegian populations. Crude and adjusted odds ratio for index age, smoking habit, infectious mononucleosis, and low sun exposure are presented with 95% confidence intervals. An ANCOVA was performed to investigate the association between infections and age at MS onset, with smoking habit and infectious mononucleosis as covariates. Stratification by sex is presented. Results: 2,040 Italians, and 2,674 Norwegians were included. MS was not associated with any of the infections considered. Measles was significantly associated with delayed MS onset in all populations, as were rubella and mumps in Norwegians, especially in women. An earlier MS onset was instead associated with chickenpox in Italians and Norwegians and with rubella in Italian men. Conclusion: Childhood infections are not associated with MS status. Measles consistently delays the MS onset, while chickenpox anticipates it. Mumps and rubella show different effects depending on the population considered. These findings suggest an influence of childhood infections, especially measles and chickenpox, on MS course.