A new study entitled “Environmental exposures and the risk of multiple sclerosis investigated in a Norwegian case–control study” published in October issue of BMC Neurology reported an increased risk for developing Multiple Sclerosis with smoking and infections, as well as the potentially protective role that exposure to cats during childhood can play in preventing the disease.
Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, and many environmental factors have already been associated with increased susceptibility to developing MS – smokers and infection by Epstein–Barr’s virus (EBV), for example. However, in this new case-control study, the authors proposed to determine how hygiene-related environmental exposures during childhood impact MS susceptibility in a Norwegian cohort. Specifically, the authors studied the role of severe infections, vaccinations, and exposure to animals. The authors performed a standardized questionnaire to 756 MS patients from the Oslo MS Registry, and 1,090 randomly selected healthy-control individuals. The questionnaire focused on environmental exposures, lifestyle, demographics, and previous as well as current diseases.
The study results confirmed infectious mononucleosis (IM), the clinical manifestation of infection with EBV, and smoking as risk factors for MS in the Norwegian cohort. Additionally, the study showed that exposure to animals during childhood can also influence MS susceptibility. While common childhood infections were previously studied in relation to MS risk, the authors focused on severe infections during childhood, such as pneumonia and meningitis. However, no differences were observed between MS and the healthy group. Notably, both groups reported similar participation in the childhood immunization program, thus excluding any risk of childhood vaccination in increased risk for MS.
The authors further suggested that exposure to cats during childhood may have a protective effect on MS, in agreement with the hypothesis that exposing the immune system to infectious agents, as the ones carried by a domestic animal, may decrease the risk of autoimmune diseases, like MS.