A Comparison of Cognitive Function in Former Rugby Union Players Compared with Former Non-Contact-Sport Players and the Impact of Concussion History
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This study investigated differences in cognitive function between former rugby and non-contact-sport players, and assessed the association between concussion history and cognitive function.
Overall, 366 former players (mean ± standard deviation [SD] age 43.3 ± 8.2 years) were recruited from October 2012 to April 2014. Engagement in sport, general health, sports injuries and concussion history, and demographic information were obtained from an online self-report questionnaire. Cognitive functioning was assessed using the online CNS Vital Signs neuropsychological test battery. Cohen’s d effect size statistics were calculated for comparisons across player groups, concussion groups (one or more self-reported concussions versus no concussions) and between those groups with CNS Vital Signs age-matched norms (US norms). Individual differences within groups were represented as SDs.
The elite-rugby group (n = 103) performed worse on tests of complex attention, processing speed, executive functioning, and cognitive flexibility than the non-contact-sport group (n = 65), and worse than the community-rugby group (n = 193) on complex attention. The community-rugby group performed worse than the non-contact group on executive functioning and cognitive flexibility. Compared with US norms, all three former player groups performed worse on verbal memory and reaction time; rugby groups performed worse on processing speed, cognitive flexibility and executive functioning; and the community-rugby group performed worse on composite memory. The community-rugby group and non-contact-sport group performed slightly better than US norms on complex attention, as did the elite-rugby group for motor speed. All three player groups had greater individual differences than US norms on composite memory, verbal memory and reaction time. The elite-rugby group had greater individual differences on processing speed and complex attention, and the community-rugby group had greater individual differences on psychomotor speed and motor speed. The average number of concussions recalled per player was greater for elite rugby and community rugby than non-contact sport. Former players who recalled one or more concussions (elite rugby, 85 %; community rugby, 77 %; non-contact sport, 23 %) had worse scores on cognitive flexibility, executive functioning, and complex attention than players who did not recall experiencing a concussion.
Past participation in rugby or a history of concussion were associated with small to moderate neurocognitive deficits (as indicated by worse CNS Vital Signs scores) in athletes post retirement from competitive sport.
KeywordsExecutive Functioning Cognitive Flexibility Mild Traumatic Brain Injury Rugby Player Rugby Union
We thank Dr Martin Raftery (World Rugby/International Rugby Board [IRB]) for initiating the IRB/New Zealand Rugby/Auckland University of Technology (IRB/NZR/AUT) RugbyHealth project and for providing feedback on the technical report that formed the basis of this article. Thanks to Peter Griffiths and Serene Lorimer who provided research administration for the project, Dr Ian Murphy (New Zealand Rugby), Heath Mills (New Zealand Rugby Players Association) and Rob Nichol (New Zealand Cricket Players Association) who endorsed the project and helped with promotion of the study and recruitment of players. We also gratefully recognise the support of Alan Boyd, Chief Executive Officer (CEO) of CNS-VS, for his support and for providing advice on the analysis and interpretation of the data.
Professor Patria Hume collaborated in designing the overarching IRB/NZR/AUT RugbyHealth project, was responsible for the original conception of the study, wrote the funding application, obtained ethical approval, helped recruit participants, helped with analyses of data, provided interpretation of the results, and co-authored the manuscript. Dr Alice Theadom determined the assessment protocols, helped recruit participants, provided interpretation of the results, and co-authored the manuscript. Associate Professor Gwyn Lewis helped recruit participants, helped with analyses of data, provided interpretation of the results, and co-authored the manuscript. Dr Ken Quarrie (New Zealand Rugby) initiated the IRB/NZR/AUT RugbyHealth project, analysed the data, provided interpretation of the results, and co-authored the manuscript. Scott Brown provided liaison for participants for the study, helped recruit participants, and co-authored the manuscript. Dr Rosamund Hill provided clinical interpretation advice and co-authored the manuscript. Professor Stephen Marshall provided statistical advice and co-authored the manuscript.
Compliance with Ethical Standards
The study was funded by World Rugby (IRB), the Sport Performance Research Institute New Zealand (SPRINZ), the National Institute for Stroke and Applied Neurosciences (NISAN), and the Health and Rehabilitation Research Institute (HRRI) of AUT, and NZR.
Kenneth L. Quarrie was employed by NZR prior to and throughout the duration of the project. World Rugby and NZR provided funding for the project. Patria A. Hume, Alice Theadom, Gwyn N. Lewis, Scott R. Brown, Rosamund Hill and Stephen W. Marshall declare that they have no conflicts of interest.
The study was performed in accordance with the ethical standards of the Declaration of Helsinki, given ethics approval was obtained from the AUT Ethics Committee (AUTEC #12/252). Participants provided informed consent after reading a participant information sheet about the project.
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