Researchers from the London School of Hygiene and Tropical Medicine (LSHTM), Queen Mary University of London and the Institute of Occupational Medicine found those over 75 with three or more reported concussions had significantly worse cognitive function on average than their peers who had fewer, after working with former England, Oxford University or Cambridge University players aged 50 or over.
The BRAIN Study found those under-75 who reported three or more concussions in their career had no worse average cognitive function than those who reported two or fewer. However, the study found that the 29 per cent (14 out of 48) of over-75s who reported three or more head injuries did have significantly worse cognitive function on average than those of the same age but with a smaller number, or none at all.
Professor Neil Pearce, from LSHTM, said: "Evidence is accumulating on the possible long-term health risks in former contact sport athletes. However, each sport is different and there is currently little evidence from rugby players.
"This study adds to this knowledge gap, and shows that playing elite rugby may affect cognitive function in older age.
"It's important more research is conducted to confirm this, and on those who played in the early years of professional rugby."
After adjusting for a large number of potential confounding factors including age, smoking and player playing position, participants over 75 with three or more concussions scored about two points lower on the Pre-clinical Alzheimer Cognitive Composite score. This does not indicate disease, but may indicate an increased risk of eventually developing neurodegenerative conditions such as Alzheimer's disease.
In total, 116 of the respondents (80 per cent) reported at least one rugby-related concussion.
Dr Simon Kemp, the Rugby Football Union's medical services director, said: "This study, that started in 2017, adds to our developing understanding of the potential long-term consequences of head impacts and concussions.
"The agreed group of participants were aged 50-plus principally because of the greater likelihood that we might detect any neurocognitive decline if present. It is important to also conduct research with younger retired players.”