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Sports physiotherapyOct 4, 2022

Study on neurodegenerative disease among former rugby players prompts call to cut head injury risks

Former Scottish international rugby union players are two times more likely to develop a neurodegenerative disease than members of the population at large, according to a study published online in the Journal of Neurology Neurosurgery & Psychiatry today (5 October).

The risk varies by condition – from just over twice as high for dementia to up to 15 times higher for motor neurone disease, the researchers found. They call for the implementation of strategies that will cut the risks of head impact and traumatic brain injury in all sports, including in training sessions.

The study’s lead author is Willie Stewart, a consultant neuropathologist and honorary professor at the University of Glasgow. Professor Stewart is the lead researcher on FIELD (Football’s InfluencE on Lifelong health and Dementia risk), which reported the first data on neurodegenerative disease risk in former professional footballers.

Traumatic brain injury is a major risk factor for neurodegenerative disease and is thought to account for three dementia cases in every 100.

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The lights are shining at Murrayfield Stadium, the home of Scottish rugby union

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Rate of motor neurone disease/amyotrophic lateral sclerosis especially high

Professor Stewart and colleagues focused on 412 male rugby players who were former Scottish internationals (out of an initial total of 654). They had access to full health and field position data on the players, who were aged at least 30 by the end of 2020. The players were matched for age, sex, and socioeconomic status with 1,236 members of the public.

National electronic health record data on hospital admissions, prescription meds, and the most common causes of death among Scottish men – circulatory system disease; respiratory disease; and cancer – were used to track the health and survival of both groups for an average of 32 years from the age of 30 onwards.

During the monitoring period, 121 (29 per cent) of the former rugby players and 381 (31 per cent) of the comparison group died. Former rugby players were older when they died, reaching an average of nearly 79 compared with just over 76 in the comparison group. They also had lower rates of death from any cause until they reached the age of 70 – after which there was no difference between the two groups.

No differences in cause of, or age at, death were observed between former rugby players and the comparison group for the most common primary causes of death for Scottish men. But the chance of being diagnosed with a neurodegenerative disease was more than twice as high among the former rugby players (47; 11.5 per cent) than it was among the comparison group (67; 5.5 per cent), although risks varied by condition.

The risk of a dementia diagnosis was just over twice as high, while that of Parkinson’s disease was three times as high, and that of motor neurone disease/amyotrophic lateral sclerosis was 15 times as high.

Strategies to reduce exposure to head impacts and head injuries across all sports should continue to be developed and promoted, while measures to mitigate risk of adverse brain health in former athletes should be considered [Emma R Russell et al]

Field position irrelevant

Additional analysis showed that field position (forward or back) of the former rugby players had no bearing on neurodegenerative disease risk. Professor Stewart and his colleagues acknowledge that 37 per cent of former international rugby players who might have been eligible for inclusion in the study had to be excluded in the absence of matched health records, and that the study focused only on men.

No information available on total career length in rugby or history of head impact and traumatic brain injury or on other potential risk factors for dementia. But the study was relatively large and long term, and the findings echo those of previous studies of former professional footballers and former American footballers, say the researchers. 

‘Notably, in contrast to data from the NFL [National Football League] and soccer, our cohort of rugby players largely comprises amateur athletes, although participating at an elite, international level. In this respect, it is the first demonstration that high neurodegenerative disease risk is not a phenomenon exclusive to professional athletes.' 

Training sessions need attention

Rugby authorities have taken steps to improve the detection of concussion injuries and to reduce the risks during match play, they acknowledge. ‘However, head impact exposures and concussion risk are not isolated to match play. As such, measures to reduce exposures in training might also be considered a priority.

‘In addition to these primary prevention measures, interventions targeted towards risk mitigation among former rugby players with already accumulated head impact exposures might also be considered, including the development of specialist brain health clinics,’ they suggest.

And they conclude: 'These data add to our understanding of the association between contact sports and lifelong health outcomes, specifically risk of adverse brain health outcomes. 

‘There remains a need for further research exploring the relationship between contact sports and risk of neurodegenerative disease. In the meantime, strategies to reduce exposure to head impacts and head injuries across all sports should continue to be developed and promoted, while measures to mitigate risk of adverse brain health in former athletes should be considered.'

In recent years post mortem studies of brain tissue have uncovered evidence of neurological disease uniquely associated with a previous history of traumatic brain injury or repetitive head impact exposure – termed chronic traumatic encephalopathy neuropathologic change (CTE-NC) – in former professional athletes from sports, including American football, soccer, and rugby union.

To see the full version of Neurodegenerative disease risk among former international rugby union players doi 10.1136/jnnp-2022-329675 visit: https://jnnp.bmj.com/lookup/doi/10.1136/jnnp-2022-329675

Author: Ian A McMillan
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