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 | You and Yours - Transcript BBC Radio 4 |
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| TX: 11.04.06 - MS - What causes it? PRESENTER: KAREN HOGGAN |
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| HOGGAN Sunlight, genetics, fish oils and the Vikings - they might not seem to have much in common but they all pop up in theories about what causes multiple sclerosis. All this week we're reporting on various aspects of this misunderstood condition and today we're looking at why some people are more likely to get it than others, conclusion - there are plenty of theories but no definite answer. We put the most common ideas to Alistair Compston, professor of neurology at Cambridge University and author of the standard text on the illness. MS FACTS AND MYTHS Multiple sclerosis was discovered by a French neurologist in 1868 but there's evidence of MS further back in history. COMPSTON Yes your statement is broadly correct in that Professor Jean-Martin Charcot gave a great account of the clinical features, he made pathological descriptions and he had some very clever ideas about what was actually going on. But he didn't discover the illness and there had been personal accounts of the illness from the early 19th Century. The English nobleman Augustus D'Este left a very tragic account of what was clearly multiple sclerosis. And shortly after that a Scottish pathologist showed the areas of abnormal tissue for the first time. So Charcot pulled the story together but he didn't discover it. MS FACTS AND MYTHS MS is generally found in the northern hemisphere. COMPSTON It is very common in Northern Europe, it is seen but much less often in Asians, there are occasional cases in Japan and China, it's a disease of legendary rarity in Africa. Of course Northern Europeans travel and North America and Australia are populated mainly by Northern Europeans and so the disease is seen there. But there are some exceptions. Individuals or groups of people in whom the illness appears to be uncommon, despite living in Northern Europe, the best example would be gypsies, another area where it is much less common than one might expect would be the people of Malta. Conversely Sardinia would be a good example in Northern Europe and perhaps the Parsees in India who have more multiple sclerosis than the Hindus. MS FACTS AND MYTHS Scotland has the highest rate of MS in the world. COMPSTON That is true. One can be a bit more specific in that it is the north eastern part of Scotland - the mainland around Aberdeen, the Orkney and Shetland islands which has the highest risk. And the best explanation for that is that this reflects genetic background because those are areas where there is a very high influence of Nordic genes, probably delivered by the Vikings, as I understand it they were in the habit of leaving behind their genetic material in the most generous way. So a strong case can be made for the Vikings having distributed the illness or distributed the risk of the illness probably through their genetic material, rather than any infectious agent that they carried. Whereas in those parts of Scotland where there is more of a Celtic influence then the rates are slightly lower. To put some numbers on that - the risk for people living in Orkney and Shetland is around 350 for every 100,000 of the population, which would compare with figures of around 120-150 per 100,000 in the southern part of England. MS FACTS AND MYTHS MS is affected by sunlight. COMPSTON You might find one or two people who would agree with you. Really they're looking at a global distribution and they're saying to themselves ah ha multiple sclerosis seems not to occur in places where there's lots of sunshine, the observation is probably true but the causal connection far from clear. However, they go on to make a further point that sunlight affects structures, chemicals, in the body, especially vitamin D and vitamin D increasingly is seen to have a role in the workings of the immune system. It's a theory and most people would not yet sign up to it, there are better interpretations of the epidemiological pattern. MS FACTS AND MYTHS Fish eating countries have a lower risk of MS. COMPSTON Some work was done in the 1950s which had suggested that there was scientific evidence to support the idea that a diet rich in fish oils was much better for people with MS than a diet saturated in animal fats. Now that hypothesis, and it is nothing more than a hypothesis, has been put to the formal test in clinical trials and those clinical trials do not show any advantage, either in terms of developing the illness or the way that it behaves, in people who take a large amount of fish oil versus animal oil but of course there are very good general reasons for adopting that kind of diet which are nothing to do with multiple sclerosis. MS FACTS AND MYTHS You should remove your mercury fillings. COMPSTON No, not in my opinion, unless you want white ones because of the appearance. There is no evidence to my mind that mercury - amalgam - fillings has anything whatsoever to do with multiple sclerosis and there's no reason to remove them, it's expensive. MS FACTS AND MYTHS Viruses could be the trigger for MS, for example glandular fever. COMPSTON Yes, there is something in the environment which triggers the illness in people who are at risk. Most people would, I think, feel that the environmental factors are germs, some form of microbe - a virus, a bacterium, or whatever it may be. And many, many such germs have been looked at as potential culprits. One which has hung around for quite some time and for which there is a certain amount of supportive evidence would be the organism called Epstein Barr virus, or glandular fever. But its relationship to multiple sclerosis is quite complex but it certainly is the strongest candidate at present and it has been for a number of years. There is an additional point though and it's not so much whether or not somebody is exposed to the Epstein Barr virus, it's more when this exposure occurs. So the tightest hypothesis is that multiple sclerosis is more common in people who are infected by the Epstein Barr virus and get glandular fever relatively late in childhood or early adult life. In those parts of the world where infections tend to occur very early in life there may paradoxically be a protection and that's why some people think the disease is relatively rare in Africa. Conversely in those parts of the world where one is protected from early viral exposure then the consequences for those people who do meet the organisms may be much greater - this is the so-called hygiene hypothesis. So we're not in the dark but we're certainly not in the light. HOGGAN That was Professor Alistair Compston unpicking some of the theories about the cause of MS. And tomorrow we'll be hearing about the difficulties that arise for people learning to live with the condition. Back to the You and Yours homepage The BBC is not responsible for external websites |
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