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Vikings could be to blame for why Scots have highest levels of multiple sclerosis in the world, say scientists
Study found one in every 170 women in the Orkney Islands suffers from multiple sclerosisIt is the highest rate in the world and has been linked with their Norse ancestryScientists say Vitamin D deficiency could also be to blame
17:45 GMT, 10 December 2012
Genetic culprit The norse ancestry of Scottish people could be at least partly to blame for high levels of multiple sclerosis
People living on a group of Scottish islands could have the highest rate of multiple sclerosis in the world thanks to the Vikings, researchers claim.
Scientists at Edinburgh University found that one in every 170 women in the Orkney Islands suffers from the disease.
Dr Jim Wilson, who led the study, said their Norse ancestry may be at least partly to blame.
The Vikings used the islands as a base for their raids and they remained under the rule of Norwegian “jarls” until 1231.
Dr Wilson, a genetics expert at Edinburgh University, said: 'Something people have thought for a long time is that the prevalence of MS could be linked to the island’s Scandinavian history, and this could be an explanation for it, though not the entire story.
'Studies that I have done, as well as others, show that half of the general population of the isles originates from Scandinavia, through the Vikings.
'There are places in Scandanavia with a higher prevalence [of MS], but there is also a real Scottish element to this disease.
'We studied in Canada as well and area’s where there is a large Scottish heritage seems to have more people that suffer from the disease, compared to a place like Quebec where the descendents are mainly French.
'I think there is a combination of genetic and environmental factors- a lack of vitamin D from the limited sun exposure is also considered to be linked.'
Dr Wilson said that the 20,000 population on the Orkneys could be more exposed due to an inherited genetic weakness yet to be discovered by scientists.
He said: 'With this clustering, some people would try to say it is due to the soil or something in the water. But, at least in the past, people married in their own community very often.
'At some level with their genetic background people in a parish are part of the same extended family. Even if we have not been able to find a genetic factor [to explain the dense levels of MS] it does not mean that it is not out there.'
MS causes myelin – a layer that
insulates nerve cells in the brain – to break down. This weakens and
slows the messages sent through nerves cells from the brain to other
parts of the body. The symptoms include numbness, loss of eyesight,
fatigue, dizziness and muscle weakness that can accumulate, leading to
Up north: The Orkney islands have the highest rate of M.S in the world
MULTIPLE SCLEROSIS: AN UNPREDICTABLE CONDITION
Multiple sclerosis (MS) is a disease affecting nerves in the brain and spinal cord, causing problems with muscle movement, balance and vision.
It occurs when the immune system mistakenly attacks the myelin that protects the nerve fibres. This disrupts the transfer of nerve signals.
Around 8 out of 10 people with MS will have the relapsing remitting type of MS.
Someone with relapsing remitting MS will have periods of time where
symptoms are mild or disappear altogether. This is known as remission
and can last for days, weeks or sometimes months.
Remission will be followed by a sudden flare-up of symptoms, known as
a relapse. Relapses can last from a few weeks to few months.
Usually after around 10 years, around half of people with relapsing remitting MS will go on to develop secondary progressive MS.
In secondary progressive MS, symptoms gradually worsen and there are fewer or no periods of remission.
There is currently no cure for MS but there are disease modifying drugs that can slow its progression.
It is not fatal but does lower life expectancy by around 10 years.
It has long been known that Scotland,
and the Orkney islands in particular, have among the world’s highest
rates of MS along with parts of Canada and Scandinavia.
last comprehensive study was in 1974, which found the number of people
in Orkney diagnosed with probable or definite MS was 309 per 100,000.
The new research, published in the Journal of Neurology, Neurosurgery & Psychiatry, found this has now increased to 402 per 100,000, which would equate to roughly 80 people on the islands.
This compares to 295 per 100,000 in Shetland and 229 per 100,000 in Aberdeen. The most recently reported rates for Alberta and Nova Scotia in Canada were about 350 per 100,000.
Dr Wilson, of Edinburgh University’s Centre for Population Health Sciences, said better diagnostic tests, along with better survival chances, may help explain why the number of sufferers had increased.
He said: 'It could also be a real underlying trend – that there is a rise in the number of people developing the disease.'
There were 'in-comers' with MS as well as lifelong residents, but no evidence that lots of people chose to live in Orkney because they had MS.
MS has long been linked to the so-called sunshine-drug Vitamin D, but Dr Wilson said that as the Shetland Islands, further north, appeared to have less of a problem than Orkney this was unlikely to fully explain the Orkney situation.
A study measuring vitamin D levels in thousands of Orcadians is currently taking place.
Mr Wilson said: 'We saw within Orkney and Shetland there were hotspots and cold spots. Some isles and parishes and villages had a much increased rate and in other parts there were hardly any residents who had it.'