Multiple Sclerosis: international comparisons

International comparisons are made difficult by the lack of consistent case definitions between surveys, the varying completeness of case ascertainment and the small number of cases included in some studies.

Multiple Sclerosis (MS) appears to show a north-south gradient. On the basis of evidence from a large number of population surveys, Kurtzke (1997) suggested a high frequency band including Northern Europe, Canada and the Northern states of the US with crude prevalence rates around 30-60/100 000 population; a medium frequency band including Australia and Northern Scandinavia with prevalences around 5-15; and a low frequency band including eastern Asia, India and Africa with prevalences under 5.

In this context, the prevalence of MS in the United Kingdom as a whole is very high. Prevalence appears to be higher in the northern parts of the UK (Forbes, Wilson and Swingler (1999)) (140-190/100,000 population in Northern Ireland and around 180/100,000 in Scotland) than in southern parts (around 90-130 in England and Wales). Similar north-south gradients have been described within the United States, with higher prevalence in northern states (Kurtzke (1997)).

Migrants from low to high risk areas (and vice versa) tend to retain the risk of their country of origin (Kurtzke (1997)).