New world map of multiple sclerosis proposed
A generation ago, John Kurtzke (who developed the EDSS scale) proposed that the world of MS could be divided into three categories: regions with high prevalence (i.e. number of MS cases in a given population), medium prevalence and low prevalence. According to this plan, a high prevalence was 30-80 people with MS per 100,000 population whereas a low prevalence was fewer than 5 people with MS per 100,000.
Since that time, numerous studies have looked at the prevalence of MS in different countries, and some have found that MS is much more common than was originally thought. So a new study has proposed that the world of MS should be divided into five categories: Very High, High, Medium, Low and Very Low (Wade BJ. Mult Scler Int 2014;2014:124578).
Here is a list of how different countries compare with respect to the prevalence of MS.
Very high (170 to 350 MS cases per 100,000 population): Canada, some regions of Sweden and Finland, Scotland, and most of Ireland.
High (70-170 cases per 100,000): Northern United States, Norway, Sweden, Denmark, Finland, England, Netherlands, Belgium, Luxembourg, Germany, Austria, Switzerland, Slovenia, Croatia, Czech Republic, Italy and Turkey.
Medium (38-70): Southern United States, Russia, Belarus, Latvia, Lithuania, Estonia, Hungary, Moldova, Poland, Ukraine, Bulgaria, Serbia, Montenegro, Faroe Islands, Spain, Portugal, Israel, most of Australia and southern New Zealand.
Low (13-38): Argentina, Brazil, Uruguay, Martinique, Barbados, Kazakhstan, Slovakia, Romania, Jordan, Lebanon, Bahrain, United Arab Emirates, Saudi Arabia, Morocco, Tunisia, Malta, South Africa, India, parts of Australia and northern New Zealand.
Very low (0-13): Chile, Ecuador, Colombia, Paraguay, Peru, Panama, Guatemala, Nicaragua, Honduras, Costa Rica, Mexico, Cuba, Mongolia, Afghanistan, Iraq, Kuwait, Qatar, Algeria, Malawi, Cameroon, Nigeria, Guinea, Benin, Senegal, China, Taiwan, Japan, Korea, Singapore, Thailand, and Malaysia.
The list of countries isn’t inclusive and reflects places where MS studies have been done. Missing from the list is Iran, which doesn’t collect national statistics on people with MS. However, a recent report estimated a prevalence of 45 per 100,000 (i.e. low prevalence), although there is considerable variability: Isfahan province has a medium prevalence (45/100,000), while Sistan-Baluchestan province has a very low prevalence (6/100,000) (Izadi and colleagues. Iran J Med Sci 2014;39:152-153).
A number of factors can influence the reported prevalence of MS in a given region. MS may not be diagnosed if a doctor isn’t looking for it and thinks it’s an unlikely diagnosis. The more widespread use of MRI has helped diagnostic accuracy, and so it’s likely that some countries will find higher prevalences than have been reported thus far.
The observation that MS is most common in certain regions of the world and in people with higher-risk ethnicity remains generally true. MS is most prevalent in people of northern Europe stock (Scandinavia, Germany, UK, France) and their emigrant ancestors (Canada, northern U.S., Australia/New Zealand, South Africa), and is considerably less common in people of Asian or African ancestry. This is probably due to a combination of genetic and environmental effects. In some groups, such as the aboriginal peoples of North and South America and Australia, MS is extremely rare. It is also considered to be extremely rare in Central Asian peoples (Uzbeks, Kazakhs, Kyrygzs, Turkmen), the Samis of northern Finland, and native Siberians.
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