Repetitive Contact in Rugby Reduces Cerebral Blood Flow, Compromises Brain Function Over a Single Season

Pavankumar Kamat

August 10, 2021

Repetitive exposure to contact events in rugby union players promotes a decline in cerebral hemodynamic function and cognition and an increase in markers for oxidative stress over the course of a single playing season, a new study published in  Experimental Physiology  suggests.

The findings may help in better understanding the risk of neurodegenerative disease later in life among athletes.

A longitudinal study included 21 players from a professional rugby union team (13 forwards and 8 backs) who played a total of 31 games in a season of the Guinness PRO-14 league. The researchers determined life-long concussion history through the players' medical records provided by the team doctor. Oxidative-nitrosative stress (OXNOS) was assessed using venous blood samples. Measures of cerebral hemodynamic function and cognition were also assessed.

Forwards versus backs experienced a greater frequency of collisions (mean±standard deviation [SD], 12±6 vs 5±3; P=.005), tackles (mean±SD, 7±4 vs 4±1; P=.028) and jackals (mean±SD, 3±3 vs 1±0; P=.034). Similarly, for every concussion experienced by backs, there were five concussions among forwards. The overall rate of concussions was 10 for every 1000 hours of play.

There was a significant elevation in OXNOS, as evidenced by an increase in ascorbate free radical and a corresponding reduction in the bioavailability of nitric oxide, which did not vary across different player positions.

Impairments in cerebral oxygen delivery and cerebrovascular reactivity range were seen among all players, but were more marked in forwards. The players also witnessed a decline in scores of cognition tests, but there were no significant differences among forwards and backs.

Professor Damian Bailey, senior author involved in the study said in a press release: "We hope that this study will encourage more rugby teams to engage in larger scale studies of this nature to determine the life-long implications associated with recurrent contact and concussion in rugby, including the potential links to neurodegeneration in later life. Our ultimate goal is to make the sport safer for the players and minimise the damage they incur through contact."

According to experts, these findings are no doubt compelling but need substantiation through larger studies.

Commenting on the findings, Prof Willie Stewart, consultant neuropathologist and Honorary Clinical Associate Professor at the University of Glasgow, stated: "Although a relatively small study in respect of number of rugby players followed, there are intriguing findings here that require pursuit in further research and, although there is suggestion that the measures here might have relevance to development of neurodegenerative disease, this is, at best, speculative."

A key limitation of the study was that it did not account for concussions occurring during training. Dr Susan Kohlhaas, Director of Research at Alzheimer's Research UK, said: "To better understand the specific factors of a rugby professional's career that might affect their brain health, future studies should also consider collisions in training. Comparing rugby players with players of non-contact sports could also help to determine whether factors other than collisions could be playing a role in these findings."

With the emergence of new factors potentially influencing the risk of neurodegeneration, Dr Kohlhaas also emphasises the need for increased funding into dementia research.

The authors of the study declared no competing interests.

References:

Owens TS, Calverley T, Stacey BS, Iannetelli A, Venables L, Rose GA, Fall L, Tsukamoto H, Berg RMG, Jones GL, Marley CJ, Bailey DM. Contact events in rugby union and the link to reduced cognition: evidence for impaired redox-regulation of cerebrovascular function. Exp Physiol. 2021 July 5 [Epub ahead of print]. doi: 10.1113/EP089330.

This article originally appeared on Univadis, part of the Medscape Professional Network.

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