Nordic clues for uncovering the aetiology of Multiple Sclerosis.

Our understanding of the etiology of multiple sclerosis (MS) is inadequate to effectively combat the increasing incidence and prevalence of the disease. Environmental factors are of crucial importance but more information about them is needed. Recent results of incidence trends over several decades in Denmark, Norway and Finland provide suggestions for further studies on the subject. Since incidence trends show marked differences by region and sex taking these factors into account when investigating birth cohort exposures could provide important new insights. Exposures during the first 15 years of life should be prioritized. International and multidisciplinary co-operation is needed.