On Tuesday 4 October 2022, a new paper was published which investigated the risk of developing a neurodegenerative disease, such as MND, among former Scottish international rugby players. The paper concluded that former Scottish international rugby union players had an increased risk of developing MND compared to the general population. We sat down with Dr Brian Dickie, Director of Research at the MND Association to discuss the paper and what this latest research means to people who play or have played rugby.
What did the study look at?
The study compared the health records of 412 former Scottish international rugby players against the health records of 1236 members of the general population, selected for similar age, where they lived and their socioeconomic circumstances. Both groups were from Scotland and were aged between 30 – 100 years old. As ‘elite’ international players they would have had significant demands on their bodies, more so than for most amateur club players
While this study focuses on rugby, there have been several previous reports on the increased risk of neurodegeneration in professional soccer players, although these are much larger studies. Smaller studies such as this have to be treated with more caution and they often raise more questions than answers.
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What was the study investigating?
The researchers wanted to understand the types of health conditions experienced and causes of death for both the former international rugby players and the general population. Comparing the two groups would then allow the researchers to pick up any particular conditions which could be more apparent in the rugby players. To do this the researchers looked at the health records of both groups over an average of 32 years, using hospital admission data, prescription records and death certificates.
What were the findings of the study?
The study looked at two main areas, the first investigated whether there were differences between the rugby players and the general population in how long they lived and what caused them to die. They found that the rugby players lived slightly longer, but the causes of death were the same as the general population.
The second area the study looked into was the number of rugby players who had been diagnosed with a neurodegenerative disease, such as dementia, Parkinson’s disease and MND. The study found that within the group of elite rugby players followed there was a two-fold increase in the risk of dementia, and a 15-fold increase for MND.
Is this a large risk?
A 15-fold increase certainly sounds large, but it is important to note that the sample size is small for a study like this. The results do need to be viewed with some caution, as the margin for error in their estimates is very large. The researchers do not actually tell us exactly how many of the players were diagnosed with MND, though from the information provided it would appear to still be a small proportion.
What is surprising from this research is that there were no cases of MND reported in the larger general population group. As MND is the most common neurodegenerative disease of mid-life, and the study included people within the ‘high risk for MND’ age range of 50-80 years old, we might have expected to see some cases recorded in the average 32 years of follow up.
Does this mean that people who play elite rugby will get MND?
No, MND is not a particularly common condition and, although there seems to be an increased risk associated with elite rugby, the overall risk is still low. While this research adds weight to previous reports on the increased risk of neurodegeneration in sports people, there are many other factors that could come into play when developing MND. As we have mentioned previously in our research blogs, there is good evidence to show that there are several factors or ‘steps’ needed to cause MND.
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At the moment we still do not know why some people develop MND, while others do not. The vast majority of cases of MND involve a complex mix of genetic and environmental risk factors. For studies like this it is important to ask the question whether there might be other factors at play. For example:
- We know MND does have a genetic link, meaning that in some cases of MND an increased risk of disease can be inherent in the family. Rugby union in Scotland is not as popular as other sports like soccer, so it’s more likely that several members of the same extended family go on to play internationally. Therefore, some of the cases of MND could have had a family link associated with genetics rather than being linked to actually playing rugby. In this study we do not know whether the players with MND had any wider family history of MND or indeed if they were related to each other.
- An increasing amount of research shows that people with MND have a mild hypermetabolism – in other words their bodies are burning energy at a slightly higher rate. It could be that this biological effect means that people who are more likely to develop MND are more likely to be athletic and therefore participate in sport. The increase in risk could be linked to general athleticism rather than a particular sport.
- Recent research indicates that these two factors may interact. MND Association funded researchers have shown that high levels of physical activity can be linked to the development of MND in some people who also have a l genetic risk. It is possible that some high-performance athletes, such as rugby players, may carry a different genetic risk to the general population.
Could cases of head injury lead to MND?
The current study does not look at whether head injury is linked to MND and it does not show that brain traumas are the cause of the increased MND risk. The authors state that there tends to be an increased level of concussion and brain trauma in people who undertake elite contact sports, but this does not mean this is a cause of MND.
Should I stop playing rugby?
As has previously been mentioned, the evidence that this risk is specific to rugby has not been demonstrated. In addition, this study followed only elite sportsmen who regularly played rugby at a very high level. We cannot assume that there is a similar risk in people who play recreational rugby, and the risk remains low.
Should I stop exercising?
The benefits of exercise greatly outweigh any potential risk. You should of course always follow the safety regulations of the sport you are participating in.
There is a lot of ongoing research looking at the potential impact of physical activity and exercise on developing MND, and at present there is not enough evidence to suggest that playing sports or being active directly leads to a person developing MND.
What’s next?
One thing is certain from this new research. It raises important questions. In order to get clearer answers, the work needs to be extended into much larger populations and include rugby players from across other nations. It also needs to look into other sports, both contact and non-contact. This will require close collaboration between the research community and rugby representative bodies across multiple countries.
As an Association we are eager to pinpoint all of the causes of MND and are currently funding research which we hope will lead to answers. MND researchers are working tirelessly to unravel the possible links between strenuous exercise, head trauma and MND, which will help us to uncover more about the causes of MND, the associated risks and potential ways to limit those risks.
By working together with researchers, institutions and other charities we are helping to facilitate research into the causes of this disease, and we are hopeful we will continue to gain new insights which will help to bring us closer to achieving our vision of a world free from MND.
