Why does the prevalence of MS vary depending on where you live?

One of the unsolved mysteries about Multiple Sclerosis (MS) is that is that the prevalence of the condition varies geographically with a high MS prevalence in Scotland. 

Understanding why this is could help prevent or even cure the condition.

Research shows that how likely you are to get MS depends on the distance you live from the equator, as Patrick Kearns, Rowling Scholar for the Anne Rowling Clinic and a researcher at Edinburgh University explains. “The rates of MS vary widely and there’s more to it than simply latitude:  at any given degree of latitude there is a large amount of variability as well. Even within countries, MS is several-fold more common in certain areas than it is in others.” says Kearns. 

Worldwide variations in the prevalence of multiple sclerosis

“There’s a long-recognised latitude effect so the further you get away from the equator – in either hemisphere – on average the higher the rate of MS,” he continues. 

It’s also recognised that Scotland has probably the highest incidence of MS in the world. 

The nature of MS means we can rely on the available data, says Kearns. 

“MS is usually diagnosed by a specialist neurologist. It [MS] is fairly distinctive in the way it presents, which means the data is really reliable. So, for example, I can be pretty sure that a neurologist diagnosing MS in Hungary, in Romania and in South Africa is diagnosing the same thing we’re diagnosing in Edinburgh and Glasgow.”

This is in contrast to neurological conditions such as lupus or orther autoimmune conditions, like Rheumatoid Arthritis (RA) where rates might be quite different dependent on local healthcare practices.

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Migration studies and multiple sclerosis (MS)

Migration studies show that MS varies by place, but also that when you migrate to – or from - a specific country or region has a direct impact on how likely you are to develop MS.

“If you move from somewhere that’s high risk to somewhere that’s low-risk before a certain age, approximately before age 14, then you can acquire the risk of the place that you move to. If you move after that age – it seems even if you move a decade or more before you get MS, you’ll keep the risk of the place where you grew up,” says Kearns.

“Scotland has extremely high rates of MS; higher than the rest of the world, and higher than the rest of the UK and so it’s a good place to study it because the awareness of MS is very high here.”

Understanding the possible causes of multiple sclerosis?

There is, says Kearns, a good understanding of the factors that are important in MS, “There’s an important role for the Epstein-Barr virus, and the evidence for this is strong.”

However, it’s a virus that we all get and “so the puzzle is what’s different about what it’s doing in healthy people versus the rest of the population.”

Some clues may come from studying regional variations, particularly in Scotland. 

Higher prevalence of MS in Scotland

MS is especially prevalent in Scotland where Kearns is based, which makes it an ideal environment for conducting research.  “There’s a big opportunity in Scotland to expand on what we know about MS.”

Initiatives by the Scottish Government have contributed to an environment that’s conducive to researching MS. In 2010, for example, the Scottish government made it compulsory that anyone diagnosed with MS is contacted by a specialist nurses within 10-days. 

There is also a national register for people diagnosed with MS.

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“That opens up the possibility to study the patterns in a lot of detail because everyone in the NHS has a national identifier so we can be very precise about where cases occur.”

Another “happy coincidence”, says Kearns, is the increasing focus on so-called human geography by the Scottish and UK governments. 

Why is there a higher prevalence in Scotland?

Part of this work has divided Scotland into 6,970 communities of around 700 people in each. 

Kearns’ focus is on getting a more detailed understanding of regional differences in MS within Scotland. “[We know] the Orkneys has a very high rate of MS, and there are lots of really unique things about Orkney.

“But 98 per cent of the Scottish population lives on the mainland,” he says. “So the question is: can we work out which towns are very high risk and which towns are very low risk, because when we know where there is high and low risk it will be much easier to ask questions as to why.”

He and his team have already proven a statistically significant higher risk in certain parts of Scotland. The challenge now is to look at differences locally. 

Read our Q&A with Scotland’s County Co-ordinator, Chris Grant

The hope is that understanding more about high and low risk areas could “give us a real clues about what is causing these differences and then the real goal is to understand this so that we get new ideas about how we could improve treatments and prevention,” says Kearns. 

A collaborative approach to researching MS

The Anne Rowling clinic for whom Kearns is Rowling Scholar has a focus on neurodegenerative conditions and regenerative medicine.

The focus is on MS and Motor Neurone Disease. There are NHS clinics at the Anne Rowling Centre, too. That and Kearns connections with Edinburgh University means that it is an environment that brings together “Patients, the NHS, philanthropy, charities, clinical and lab researchers,” all working together on MS.

There is an MS Society for MS Research based at the University of Edinburgh funded by a grant from the MS Society. 

Harry Potter author JK Rowling whose mother died of the condition has funded a research centre at Edinburgh University.

These connections are important and help motivate Kearns to solve the age old mystery around geographic differences in MS.

“It’s an unsolved problem, but one I think we can solve,” he says. “The connection with the MS Society and other patient focussed groups is really important; having connections with these groups reminds us all why we are doing what we are doing and ensures that we stay focussed on what matters to real people living with MS.”