Background: Epidemiological studies suggest that environmental factors play a significant role in the development of multiple sclerosis. This article presents current knowledge on the impact of the environment on disease risk and disease course.
Method: We have conducted searches in PubMed for «multiple sclerosis» combined with «environment» as well as relevant environmental factors.
Results: It is highly likely that an interaction between genetic and environmental factors determines who will develop multiple sclerosis. Epstein-Barr virus infection, smoking, and low vitamin D levels are the environmental factors that have shown the strongest and most consistent association with development of the disease. Low vitamin D levels are also associated with high disease activity. Other risk factors include obesity and high salt intake.
Interpretation: Although epidemiological studies have identified a number of environmental factors with potential aetiological relevance, and the importance of these is supported by experimental studies, there is still insufficient evidence to establish a causal role for these factors in multiple sclerosis.