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A to Z of MS

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A to Z of MS Prevalence and incidence of multiple sclerosis

Terminology

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

The study of the geographical distribution of a condition and patterns of disease as it affects groups of people is called epidemiology.

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.

Race

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

Studies in the UK have suggested that the prevalence rate in England and Wales is perhaps between 100 and 140 per 100,000, about 170 in Northern Ireland and as high as 190 in Scotland. A study of north east Scotland found the level to be 229 in Aberdeen, 295 in Shetland and 402 in Orkney.

There is as yet no complete national register of people with MS in the UK, though projects are underway (see sidebar for links). In 2009, research by the London School of Hygiene and Tropical Medicine based on records held by GPs suggested that there may be around 100,000 people with MS in the UK. This research has not yet been published in a peer reviewed journal.

Research published by the University of Dundee used the same source of records as the 2009 study and reached a total of 127,000 people with MS and 6,000 new cases in 2010.

Bibliography

Compston A, et al.
McAlpine's multiple sclerosis (4th ed).
London:Churchill Livingstone;2005.

McGuigan C, et al.
Latitudinal variation in the prevalence of multiple sclerosis in Ireland, an effect of genetic diversity.
Journal of Neurology Neurosurgery and Psychiatry 2004;75:572–576.
read online (pdf 250kb)

Rosati G.
The prevalence of multiple sclerosis in the world: an update.
Neurological Sciences 2001;22:117-139.
abstract

Orton SM, et al.
Sex ratio of multiple sclerosis in Canada: a longitudinal study.
Lancet Neurology 2006;5(11):932-936.
abstract

Prevalence of MS in the UK revised
MS Trust news item - 12 June 2009
read news item

Alonso A, et al.
Incidence of multiple sclerosis in the United Kingdom: findings from a population-based cohort.
Journal of Neurology 2007;254(12):1736-1741.
abstract

Visser EM, et al.
A new prevalence study of multiple sclerosis in Orkney, Shetland and Aberdeen city.
Journal of Neurology, Neurosurgery and Psychiatry 2012;83(7):719-724.
abstract

Mackenzie IS, et al.
Incidence and prevalence of multiple sclerosis in the UK 1990-2010: a descriptive study in the General Practice Research Database.
Journal of Neurology, Neurosurgery and Psychiatry 2013 Sep 19. [Epub ahead of print].
Read online

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