Epidemiology: the study of the geographical distribution of a condition and patterns of disease as it affects groups of people
Prevalence: the number of people with a condition. Usually measured in cases per 100,000
Incidence: the number of new cases of a condition within a set period of time, usually a year
An estimated 2,500,000 people in the world have multiple sclerosis. Research suggests the proportion of women with MS is increasing and that roughly between two and three women have MS for every man with the condition.
The distribution of MS around the world is uneven. Generally, the prevalence increases as you travel further north or south from the equator. Those parts of Asia, Africa and America that lie on the equator have extremely low levels of MS, whilst Canada and Scotland have particularly high rates.
A simple geographical spread is not the whole picture. Studies show that certain ethnic groups have a markedly lower prevalence of multiple sclerosis, despite living in countries where MS is common. For instance, the Sami or Lapps of northern Scandinavia and the Inuits in Canada have very low rates of MS. A similar pattern is observed amongst the Maoris of New Zealand.
The fact that multiple sclerosis is most prevalent in northern Europe, North America, Australia and New Zealand has led to speculation that it has been carried around the world by European colonists and settlers. It has been suggested that the origins can be traced back to the Vikings who colonised those parts of Northern Europe where MS is most pronounced and that 'Viking genes' can make people particularly susceptible to MS.
It has also been noted that Scotland has a much higher rate of multiple sclerosis than England or Wales and that areas of high MS prevalence around the world have been settled by Scottish immigrants. In Ireland, the north of which was extensively settled by immigrants from Scotland from the 17th century, the rate in Co Wexford in the south was recorded in 2004 as 121 per 100,000 whilst the rate in County Donegal in the north was 185. A study of Northern Ireland found a rate of 168 in 1996.
Multiple sclerosis in the UK
There is currently no accurate data on the exact number of people with MS in the UK. A study by McKenzie et al at the University of Dundee worked out a figure based on coding in GP records. This gave a figure of 127,000 people with MS in the UK in 2010. Concerns were raised that this figure may include some records where there was an element of doubt about the diagnosis. If these records were excluded it would give a total of 107,000 people with MS in the UK in 2012. The McKenzie study also found that the number of people with MS in the UK is growing by around 2.4% per year, due to people with MS living longer.
Prevalence rates vary around the UK. Based on the estimate of 107,000 people with MS in 2012, it is estimated that the number of people with MS in England is around 165 per 100,000; in Wales about 140; about 174 in Northern Ireland and as high as 212 in Scotland. Prevalence in the north of Scotland is particularly high. A study of north east Scotland found the level per 100,000 people in 2009 to be 229 in Aberdeen, 295 in Shetland and 402 in Orkney. .
There are two MS register projects underway.
- The UK MS Register is a scheme that allows people to upload information about their condition that allows researchers to look at different aspects of the condition across a large numbe rof people. There are more than 12,000 people registered.
- The Scottish MS Register gathers information from records on new diagnoses of MS. This register has been running since 2010. In that time about 430 new cases of MS have been reported each year in Scotland, a lower incidence rate than suggested by the Dundee study.
- London:Churchill Livingstone;2005. McAlpine's multiple sclerosis (4th ed).
- Journal of Neurology Neurosurgery and Psychiatry 2004;75:572–576. Full article (PDF 250KB) Latitudinal variation in the prevalence of multiple sclerosis in Ireland, an effect of genetic diversity.
- Neurological Sciences 2001;22:117-139. Summary The prevalence of multiple sclerosis in the world: an update.
- Lancet Neurology 2006;5(11):932-936. Summary Sex ratio of multiple sclerosis in Canada: a longitudinal study.
- Journal of Neurology 2007;254(12):1736-1741. Summary Incidence of multiple sclerosis in the United Kingdom: findings from a population-based cohort.
- Journal of Neurology, Neurosurgery and Psychiatry 2012;83(7):719-724. Summary A new prevalence study of multiple sclerosis in Orkney, Shetland and Aberdeen city.
- Journal of Neurology, Neurosurgery and Psychiatry 2014;85(1)76-84. Full article Incidence and prevalence of multiple sclerosis in the UK 1990-2010: a descriptive study in the General Practice Research Database.
- 2013 Download (pdf 43kb) MS in the UK
- Summary report (pdf 68kb) National Report 2015 - September 2015.
Last updated: 9 September 2015
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