EXPERT REACTION: Brain disease risk more than double among former rugby players

This paper makes a significant contribution to the body of literature on the relationship between the sport of rugby and various neurodegenerative diseases (disorders that affect the normal function of the nerve cells in the brain or peripheral nervous system). Particularly laudable is its extensive review of the datasets.

While this paper did show that there was significant increase in neurodegenerative diseases amongst past rugby players, it cannot explain which aspect of the sport of rugby itself was the cause for the increase. Of particular relevance for this issue is the fact that the study did not have any information on the history of head impact and traumatic brain injury exposure for the ex-rugby players it studied. 

In other words, while the study showed that rugby as a sport placed its players at greater risk of neurodegenerative diseases later on in life, it does not tell us why this is so. This means that it could be a number of unaccounted factors. These factors can range from things such as past dietary habits and use of medications, supplements or drugs by the athletes; to possibly non-head trauma-related exposure of the players to the various environmental factors linked to dementia. 

It is reasonable, based on other published studies, that the authors have suggested that the blame for the increase in risk they found lies with head trauma. However, more research that specifically targets this causative link needs to be done in order to go beyond mere assertion.

In a study examining records of 412 former international Scottish rugby players and 1236 men from the community (matched for age and socio-economic status), the rugby players had more than twice the rate of neurodegenerative diseases such as dementia and Parkinson’s disease. There were no differences in rates of other diseases examined. There was no difference between backs and forwards among the rugby players. A surprising finding was the higher rate of Motor Neuron Disease although numbers were very small and none of the comparison group developed MND.

This study builds to the growing evidence of the dangers of contact sports and repeated head injuries especially those leading to concussion or loss of consciousness.

The findings of this rigorous study into dementia risk in former international rugby union players strengthen existing evidence that CTE [chronic traumatic encephalopathy] is caused by the accumulation of head injury, be it concussive or subconcussive. We are yet to see the data emerge on CTE according to duration of play and age of commencement in rugby union, as has long been identified in American football or NFL but research is gearing up. An association between CTE and motor neurone disease (MND) is again highlighted in the literature, with 15 times the risk of MND in this population. 

Although this study remains relatively low in case number, the long-term data acts as a siren on the need to invest heavily in longitudinal clinical prospective studies on CTE involving rugby union players. That Australia is behind with respect to our own football codes should raise substantive concern. Indeed, studies extending outside of sport to other environments of repeated head injury such as domestic and family violence will be crucial, calling for the backing of Government to this wide-ranging issue. Without a focussed, careful approach of transition to safer concussion sport, there is a risk that participation will dive, raising potential cardiovascular risk in children.

Regardless of the eventual incidence and prevalence of CTE in the rugby playing population from ongoing studies, the need to proactively restrict training and match-related head injury is clear. Not only will this implicate changes to the age of commencement of contact but potential restrictions on the duration of an individual’s career or 2-5 yearly neurological monitoring of players to detect the clinical features of CTE. Sporting leadership should act now for the safety of the community and longevity of their own sports or face the consequences.

This study used a powerful technique called data linkage, which matches people to their health records. This enabled researchers to access de-identified information including disease diagnoses, medications prescribed, and cause of death for each individual person in the study. With this rich data set, the health of the rugby players could be tracked over 32 years, and compared to members of the general public over the same time frame.
 
Researchers found that the risk of neurodegenerative disease was more than double in the rugby group compared to the general public group. When looking at specific diagnoses, they found that the rugby group were twice as likely to be diagnosed with dementia, three times as likely to be diagnosed with Parkinson’s disease, and 15 times more likely to be diagnosed with motor neurone disease. These rates are similar to those found for other contact sports.
 
This study contributes to a growing body of evidence that participation in contact sports increases the risk of neurodegenerative disease later in life, regardless of the sport or level of play. Similar studies on AFL players are needed to understand whether the same risk applies.
 
Due to the nature of the study, researchers were not able to assess the effects of career length or the number of brain injuries. The influence of these factors will be important for future studies, and may help inform guidelines and personal decisions on when it’s time to hang up the boots.

The study by Russell et al., shows that the risk of neurodegenerative disease is 2.6x higher former rugby union players than the general population. These results corroborate findings from previous studies that examined neurodegenerative disease risk in former NFL players and soccer players. The rugby cohort largely comprised players that played at elite amateur level, which indicates the increased risk of neurodegenerative disease now reported across multiple sports is not limited to professional athletes.

"It is notable that the risk varied by disease subtype with motor neuron disease risk being the highest, followed by Parkinson’s disease and dementia not otherwise specified. The authors were not able to distinguish other specific types of dementia in their study, such as frontotemporal dementia, Alzheimer’s disease. The authors also did not have access to date on the length of the athletes playing career so were not able to determine whether the risk of neurodegenerative disease correlated with the career duration as has been shown in both former NFL and soccer players. Overall, these findings support the idea that repetitive head injury is a risk factor for a range of neurodegenerative diseases. Chronic Traumatic Encephalopathy (CTE) is the most widely known brain pathology linked repetitive head injury in sport. However, this study reinforces the idea that head injury risk is not limited to CTE, and former contact-sport athletes should be monitored for all types of dementia. Every type of dementia is devastating.

"It is unclear whether these findings will be applicable to female athletes or non-elite athletes. This is a limitation of all current studies as we have very little data on these groups. The collection of this data should be a priority as women's sport and amateur sport continues to grow and it is vital that we understand whether the long-term risk of neurodegenerative disease differs in these populations.

"This study is valuable for us in New Zealand due to the popularity of rugby and other contact sports. The findings of this study emphasise the importance of developing strategies to reduce exposure to head impacts in training and games and to be cautious in our approach to head injury management and return to play. We should also investigate strategies to proactively monitor and improve the brain health of contact sport athletes during and after their athletic career.

"This study also highlights the need for additional research exploring the mechanisms of how head injuries alter the brain and how these changes can progress into neurodegeneration. Here at the University of Auckland Centre for Brain Research we have developed the sports brain bank initiative as part of the Neurological Foundation Human Brain Bank. We are studying the donated brain tissue of deceased former athletes with and without cognitive symptoms to understand how repetitive head injury exposure alters the microscopic structure of the brain.

The evidence that collision sports are associated with increased rates of death from neurodegenerative diseases is continuing to accumulate. The repeated findings of brain health issues in former rugby players in the NZ RugbyHealth and UK RugbyHealth studies, and now in this Scotland study, are adding weight to the call for reduction in risk factors for brain diseases – including repeated head impacts in sport.

The finding of death from a neurodegenerative disease being greater in former rugby players (2x greater for dementia and 3x greater for Parkinson’s disease) than a general population group, based on analysis of hospital and prescription data, despite no data on rugby career length or history of concussion, does again raise the question, why is there a greater risk of brain disease in former rugby players?

This is the second major study from Willie Stewart’s group who showed previously an increased risk of neurodegenerative disease in Scottish soccer players.

While this study is smaller in sample size, the data clearly shows increased risks of neurodegenerative disease in Scottish rugby union players and increases the evidence worldwide of the exposure risk of neurodegenerative diseases such as chronic traumatic encephalopathy (CTE) following the recently published paper by 14 international experts from five countries led by Christopher Nowinski, which argues a causative association between repeated head impacts and neurodegenerative risk.

Consequently, we need a concerted effort to change how we approach these sports in not only concussion management but also in reducing exposure to adult athletes, as well as modifying contact sports for junior players (children and young adolescents) up to the age of 14 years.