[Incidence of multiple sclerosis in Scandinavia and Finland]

Review of studies of incidence of multiple sclerosis (MS) over several decades in seven geographical areas scattered over Scandinavia and Finland have shown that incidence rates fluctuate significantly with time in most of the areas, but in an inconsistent pattern. The incidence appeared to be the lowest in the northernmost parts of Norway showing that the well-known north-south gradient for risk of MS does not hold true for high latitudes. The time-space variation in incidence rates supports the view that local non-persistent environmental factors may play a role in the aetiology of the disease.