The prevalence of multiple sclerosis in the Outer Hebrides compared with north-east Scotland and the Orkney and Shetland Islands.

Multiple sclerosis has been reported to have a high prevalence in the Orkney and Shetland Islands and in Caithness in comparison with the highlands of Scotland and the Outer Hebrides-the Western Isles. For this reason a survey was undertaken in the Outer Hebrides and 25 probable and 30 probable and possible patients with multiple sclerosis were found. This is an increase from eight and 11 respectively found in 1954. The present prevalence rate of 97.3 per 100 000 for probable and possible multiple sclerosis is not significantly different from that found in a recent study in the Grampian region in north-east Scotland. Repeated studies in small populations generally show increasing prevalence of multiple sclerosis because some patients are missed in the earlier studies, and over a long period of time there may also be some increase in survival time. This increase has been found in the Orkney and Shetland Islands, in north-east Scotland, and also in the Outer Hebrides.