Rugby players and others involved in physical contact sports suffer a shrinkage in the part of the brain responsible for memory, even if they have not suffered major concussion injuries, according to research.

Researchers in the United States closely examined a group of American Rules footballers over two years, carrying out detailed cognitive tests to track the impact of the sport upon the hippocampus – which processes short-term memories into long-term ones.

Players who had previously had concussion injuries had hippocampus that are a tenth smaller than those who had not, but the hippocampus is also reduced in size for those who had played for years without reporting injury.

"If anything, rugby players get even more blows to the head than American football players," the head of the research, Dr Patrick Bellgowan, told The Irish Times last night when asked if the research had implications for rugby.

"Many of the neurological and psychiatric findings from concussion research in American Rules football are being replicated in rugby players," said Dr Bellgowan, who is based at the Laureate Institute for Brain Research, Tulsa, Oklahoma.

'Brain injury'
The findings, carried out between 2011 and 2013, suggest "that, particularly in young athletes, concussion should be treated conservatively keeping in mind the possible long-term consequences of the brain injury", according to the report, published by JAMA Network.

Footballers had smaller hippocampi than those from a control group who did not play contact sports at all, while players “with a history of concussion” had smaller hippocampi than players who had not suffered such injuries.

In addition, the size of the hippocampus and the time taken by players to answer detailed cognitive tests increased in proportion to the number of years that they played the sport – even if they had never knowingly suffered concussion.

“Even in the absence of concussion, compromised white matter integrity has been documented in the hippocampus of collegiate contact-sport athletes,” according to the report, adding that repetitive mild concussion injuries to animals quickly produce scarring in the hippocampus.