Rugby-dementia link established: study

Former male high-level rugby players in New Zealand have a 22 percent increased risk of developing Alzheimer’s and other dementias later in life compared to men in the general population, according to new research from the University of Auckland.

The project is co-led by senior lecturer Dr Stephanie D’Souza from the COMPASS Research Centre in the University’s Faculty of Arts and Education and Dr Ken Quarrie from New Zealand Rugby.

Researchers examined long-term neurodegenerative disease risk outcomes for almost 13,000 men who played provincial-level or higher rugby between 1950 and 2000 and compared them with 2.4 million New Zealand men, matched on age, ethnicity and birthplace.

Out of every 1,000 men in the general population, 52 died from, or were diagnosed with, a neurodegenerative disease over the follow-up period from 1988 to 2023, but among former rugby players, the number was 65 per 1000, says the study’s lead author, PhD student Francesca Anns.

“This is an extra 13 cases per 1,000 people over the study period, or around four extra neurodegenerative disease cases per year, given the size of the player cohort,” she says.

And she says both international/professional and provincial/first-class amateur players had higher risks than the general population, although the risks were greater at the higher playing level.

“Our analysis also showed that players in backline positions had greater risks than forwards, with the risk for backs increasing further the longer they played or the more matches they played, a pattern not observed for forwards.”
 

Anns says the increased risk of disease typically became apparent from the age of 70 onwards, with no evidence of earlier-onset illness.

Co-lead investigator Dr Stephanie D’Souza says these results are consistent with research into other collision sports from the US, Scotland and Italy, but the effect sizes in their study were slightly smaller than most previous reports.

“That may reflect differences in how the study was designed,” she says, “including the size and make up of our comparison group, the fact that our study included both provincial and international players, rather than only elite professionals, and how cases were identified, as well as differences in how rugby was played in New Zealand over the decades we studied.”

The study is part of the Kumanu Tāngata project, which is focused on investigating the long-term health outcomes of first-class rugby players using de-identified linked data, which mean names are removed.

It adds to growing evidence linking collision sports with later-life brain health risks, believed to be due to exposure to head knocks, says D’Souza.

“While the research can’t prove causation, the consistent pattern across multiple studies strengthens the case for a connection. In this study, higher risks were seen in players who competed at the international or professional level, as compared to those who only played provincially, and for backs whose risk increased with more years and matches played.”

She says these patterns showing higher risk with both greater intensity and longer duration of play suggest a possible ‘dose-response’ relationship.

“The position differences also indicate that the nature of contact, not just the number of head impacts, may be important in understanding risk.”

The study’s authors recommend that collision sports organisations limit player exposure to head impacts and manage suspected concussions proactively, while continuing to communicate openly about both the benefits and risks of participation in sports like rugby.

Neurodegenerative diseases in male former first-class New Zealand rugby players by Francesca Anns, Kenneth L. Quarrie, Barry J. Milne, Chao Li, Andrew J. Gardner, Ian R. Murphy, Evert Verhagen, Craig Wright, Susan Morton, Thomas Lumley, Lynette Tippett and Stephanie D’Souza has been published in Sports Medicine.

This study was supported by World Rugby Limited and the New Zealand Rugby Foundation. Statistics New Zealand, and its staff granted researchers access to the Integrated Data Infrastructure (IDI), a large research database which holds anonymous microdata about people and households in New Zealand.

The Public Policy Institute at the University of Auckland granted access to its Statistics New Zealand data lab. The funders had no role in the study design, data collection, analysis, interpretation, or writing of the manuscript.