Abstract
BACKGROUND: Accumulating evidence suggest that Epstein-Barr virus (EBV) is crucial in the development of multiple sclerosis (MS), with inadequate infection control possibly contributing to disease onset. Past infectious mononucleosis (IM) has been found to interact with smoking, obesity, and sun exposure. We aimed to investigate potential interactions between a history of IM and the following risk factors for MS: passive smoking, alcohol consumption, fish consumption, vitamin D status, adolescent sleep duration and sleep quality. METHODS: We analyzed data from a Swedish population-based case-control study (3128 cases and 5986 controls). Subjects were categorized based on IM status and each exposure variable and compared regarding MS risk by calculating odds ratios (OR) with 95% confidence intervals (CI) using logistic regression models. Additive interaction between aspects of IM status and each exposure was assessed by calculating the attributable proportion due to interaction (AP) with 95% CI. RESULTS: The OR of developing MS among those who reported a history of IM was 1.86 (95% CI 1.63-2.12), compared with those who had not suffered from IM. We observed synergistic effects between a history of IM and each exposure variable with respect to risk of MS, with significant APs ranging between 0.20 and 0.35. CONCLUSIONS: The concept of EBV infection as a crucial factor for MS gains further support from our findings suggesting that MS risk factors synergize with a history of IM in disease development. Targeting modifiable MS risk factors that impede effective immune regulation of the virus holds promise for preventive interventions.