Medical research - the key to understanding what causes MS

Thursday, 2 June 2016 - 3:05pm

Twenty-five years ago when Professor Bruce Taylor first started to care for people with Multiple Sclerosis (MS), little was known about what causes this debilitating disorder. Back then, the MS Society used to give out booklets on the disease (to those newly diagnosed) entitled “MS - the mystery illness”. There was no effective treatment. People with MS were advised not to have families and, in some cases, to give up working.

Fast forward to 2016 and there is now a range of different therapies that can be used to treat MS. Although MS cannot be cured, for the majority of those living with the condition progress can be halted or slowed down. There is now a far greater understanding of what causes MS, that in no small degree has come from research conducted in Tasmania at the Royal Hobart Hospital and Menzies Institute for Medical Research. This research has been supported to a significant extent by the RHH  Research Foundation.

Around 80% of the risk of developing MS can now be explained from five major interacting factors. Firstly, genetics - MS occurs more frequently in families, some more than others,  and this is due to the action of nearly 200 genes. MS is not an inherited feature like blue eyes or cystic fibrosis. The risk of MS is increased in those who carry these genetic variants, but it is not absolute. Many people without MS have these genetic variants, but do not have the disease.

Secondly, there are environmental factors. For example, MS is more common in European populations the further you move from the equator. In Tasmania the rate of MS is nearly seven times higher than it is in Northern Queensland, even though the populations are genetically similar. Much work has been done exploring the fact that this is due to decreased sun exposure and lower D vitamin levels, over the last 15 years we have shown proof that these two factors do play a role in MS risk.

Thirdly, it is now known that MS is almost exclusively found in people who have been exposed to the Epstein Barr Virus (EBV). EBV is the virus that causes glandular fever. Additionally, we know that the timing of EBV infection is important as having glandular fever during adolescence almost doubles the risk of developing MS. Similarly, having higher levels of antibodies to EBV in the circulation also increases the risk of MS.

We also know that cigarette smoking significantly increases the risk of MS and in all likelihood makes MS worse for those living with the disease.

Finally, we know that adolescent obesity also increases the risk of MS.

Importantly, there is no one single cause for MS and not everyone has all the risk factors, nor do these factors act independently. Many of the factors are known to interact with each other to increase the risk of MS. We also know that the timing of exposure is very important, with the risk of MS probably being determined by factors that act in the adolescent period, such as sun exposure, glandular fever, cigarette smoking and obesity.

The risk of getting MS can be thought of by using the analogy of falling off a cliff. If you are walking along the top of a cliff, you can think of the genetic risk as being how close the pathway is to the cliff’s edge with the more genetic risk being associated with the path being closest to the edge but in itself not causing you to fall. Other factors are needed to increase the risk of falling, such as rain making the rocks slippery, high winds and  darkness. If all these factors come together the risk of falling is significantly greater but not absolute. Hopefully by understanding these factors better we can allow more people to pass safely to the next beach.