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Prevalence and incidence of multiple sclerosis

Vikings touring the world

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.

Terminology

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

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

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. The 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.

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 suggests that there are about 110,000 people with MS in the UK.

Prevalence rates vary around the UK. Based on the figure of 110,000 people with MS, it is estimated that the number of people with MS in each nation is:

  • England is around 90,500 or 164 per 100,000
  • Wales about 4,300 or 138 per 100,000
  • Northern Ireland about 3,200 or 175 per 100,000
  • Scotland about 11,300 or 209 per 100,000

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.

A little over 5,000 people are diagnosed with MS each year, roughly 100 a week.

Changes over time

There is evidence to suggest that both MS incidence and prevalence rates have increased over the last few decades. Better access to neurology services and better diagnostic criteria mean that more cases of MS are detected than previously. Also, as people now tend to live longer in general and live longer with MS, the prevalence of MS appears to be greater as well.

It is likely that lifestyle factors that have changed over the years will have affected the rates of prevalence and incidence as well. A study of these rates in Norway over the last eighty years suggested that people smoked more and got less vitamin D from being outside than at the start of the study period, and that this could have affected the rate at which people acquired MS.

MS registers

There are two MS register projects underway in the UK.

  • 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 number of people. There are almost 15,000 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.

Last updated: August 2018
Last reviewed: September 2015
This page will be reviewed within three years