Hva skyldes endringen i kjønnsratio ved multippel sklerose?

Abstract

Abstract Multiple sclerosis (MS) is commonly known to be more frequent in women than in men. However, in the early 1900s, the sex ratio was estimated to be close to unity or even in favor of a male excess. The increase in female-to-male ratio has been evolving throughout the century and is now estimated to vary between 1.5:1 and 3:1. This change is due to a disproportional increase in incidence of MS in women. The causal agents of the growing preponderance in women are yet to be discovered. The change in sex ratio is too rapid to be due to genetic factors. It may partly be attributed to skewed improvement in case ascertainment, especially for more benign forms of relapsing remitting MS (RRMS), probably affecting women more frequently than men. Moreover, the change in sex ratio has been shown to be driven by birth cohort effects. This implicates the presence of one or more environmental risk factors that occur in young age and determine MS lifetime risk for an entire generation. These yet unknown environmental factors or gene-environment interactions have necessarily affected the sexes differently in order to cause the change in the sex ratio.