Age of puberty and the risk of multiple sclerosis: a population based study

Genetic and environmental factors have important roles in multiple sclerosis (MS) susceptibility. Given a potential role for sex hormones in MS, we have investigated whether or not the age of puberty influences the risk of developing MS in a population-based cohort. We identified 5493 MS index cases and 1759 spousal controls with age of puberty information from the Canadian Collaborative Project on Genetic Susceptibility to MS. Age of puberty was compared between index cases and controls, and any effect of age of puberty on the age of onset of MS was also investigated. There were no significant differences between male index cases and controls with respect to age of puberty, P = 0.70. However, a significant difference was observed between female index cases and female controls, with average age of puberty being 12.4 and 12.6 years respectively, P = 0.00017, providing a relative risk decrease of 0.9 per year increase of age of puberty. There was no effect of the age of puberty on the age of MS onset in either sex. Earlier age at menarche increases the risk of MS in women. Whether this association is a surrogate for a disease causative factor or directly involved in MS disease aetiology needs to be uncovered.