Just one season of professional rugby could cause a decline in a player’s blood flow to the brain and cognitive function, according to a University of South Wales study.
The research, reported by the BBC, also suggests that repetitive contact events, rather than only concussions, incurred through rugby caused the declines seen in the players.
Researchers from the University of South Wales followed a professional team playing in the United Rugby Championship over the course of a season, testing the players pre-season, mid-season and post-season.
The peer-reviewed study found that over the season the squad experienced reduced blood flow to the brain and cognitive function – the ability to reason, remember, formulate ideas and perform mental gymnastics. And while previous research has focused predominantly on the incidence of concussion, there has been little investigation of the physiological toll of repetitive contact on the field.
According to The Guardian, some studies suggest professional rugby players could be exposed to thousands of contact events each season. Increasingly, further research is beginning to show that it may not be concussions alone that may affect the brain, but the cumulative effect and volume of contact events as well.
The team behind the study said further research was needed on the long-term effects.
The issue of brain injury in the sport came under the spotlight last year when a group of former players sued the game’s authorities after being diagnosed with early-onset dementia, which they believe was caused during their rugby careers.
In a statement responding to the University of South Wales study, the sport’s governing body, World Rugby, said: “World Rugby welcomes all research that can inform and support our recently launched strategy to cement rugby as the most progressive sport on player welfare. It is at the heart of everything that we say and do as a sport.”
It added: “World Rugby recently committed to double our investment in player welfare and new concussion research and initiatives.”
Funded by the Royal Society Wolfson Research Fellowship, the research recorded six concussion incidents among the players that took part over the course of the year. Every player involved in the study recorded a decline in blood flow to the brain and cognitive function between pre- and post-season results.
Prof Damian Bailey, one of the authors, said that even over a short period there was a greater decline in brain function. “And we’re assuming our baseline is a normal healthy baseline but many of these players have already had many years playing the game, so that baseline is probably still impaired,” he told the BBC.
The study also found a correlation between an increase in contact amount, playing position and rate of decline on the main measures tested. In forwards, who are involved in more contact, a greater degree of impairment was noticed, relative to backs.
Asked whether any comparison could be made between professional and grassroots level, Bailey told the BBC: “It’s difficult to say, but we don’t think why it would be terribly different,” adding that while professional players have less opportunity to recover, bigger physiques, and potentially bigger impacts as a result of contact, amateurs could have arguably poorer technique and be at risk as a result.
“We have every reason to believe that the damaging effects could be cumulative over time,” Bailey added. The team is also working on a similar study, comparing both current and retired players against a control group to determine whether there is a faster rate of decline in brain function in rugby players. They said further research was needed on the long-term effects of such a decline.
World Rugby said: “We are currently undertaking a wide-ranging evaluation of contact training volume across the game and look forward to the results of the ongoing Otago Rugby Community Head Impact Detection study, which is the largest ever study of playing and training head impacts in men’s and women’s community rugby. “Both will inform the further introduction of guidelines and preventative measures that best support the welfare of all players.”
Contact events in rugby union and the link to reduced cognition: evidence for impaired redox-regulation of cerebrovascular function
Thomas S. Owens, Thomas A. Calverley, Benjamin S. Stacey, Angelo Iannatelli, Lucy Venables, George Rose, Lewis Fall, Hayato Tsukamoto, Ronan M. G. Berg, Gareth L. Jones Ronan M. G. Berg, Gareth L. Jones, Christopher J. Marley, Damian M. Bailey,
Published in Experimental Physiology 5 August 2021
• What is the central question of this study?
How does recurrent contact incurred across a season of professional rugby union impact molecular, cerebrovascular and cognitive function?
• What is the main findings and its importance?
A single season of professional rugby union increases systemic oxidative–nitrosative stress (OXNOS) confirmed by a free radical-mediated suppression in nitric oxide bioavailability. Forwards encountered a higher frequency of contact events compared to backs, exhibiting elevated OXNOS and lower cerebrovascular function and cognition. Collectively, these findings provide mechanistic insight into the possible cause of reduced cognition in rugby union subsequent to impairment in the redox regulation of cerebrovascular function.
Contact events in rugby union remain a public health concern. We determined the molecular, cerebrovascular and cognitive consequences of contact events during a season of professional rugby. Twenty-one male players aged 25 (mean) ± 4 (SD) years were recruited from a professional rugby team comprising forwards (n = 13) and backs (n = 8). Data were collected across the season.
Pre- and post-season, venous blood was assayed for the ascorbate free radical (A•–, electron paramagnetic resonance spectroscopy) and nitric oxide (NO, reductive ozone-based chemiluminescence) to quantify oxidative–nitrosative stress (OXNOS). Middle cerebral artery velocity (MCAv, Doppler ultrasound) was measured to assess cerebrovascular reactivity (CVR), and cognition was assessed using the Montreal Cognitive Assessment (MoCA). Notational analysis determined contact events over the season. Forwards incurred more collisions (Mean difference [MD] 7.49; 95% CI, 2.58–12.40; P = 0.005), tackles (MD 3.49; 95% CI, 0.42–6.56; P = 0.028) and jackals (MD 2.21; 95% CI, 0.18–4.24; P = 0.034). Forwards suffered five concussions while backs suffered one concussion. An increase in systemic OXNOS, confirmed by elevated A•– (F2,19 = 10.589, P = 0.004) and corresponding suppression of NO bioavailability (F2,19 = 11.492, P = 0.003) was apparent in forwards and backs across the season. This was accompanied by a reduction in cerebral oxygen delivery (, F2,19 = 9.440, P = 0.006) and cognition (F2,19 = 4.813, P = 0.041). Forwards exhibited a greater decline in the cerebrovascular reactivity range to changes in PETCO2 ( compared to backs (MD 1.378; 95% CI, 0.74–2.02; P < 0.001).
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