Influence of playing rugby on long-term brain health following retirement: a systematic review and narrative synthesis.

Objectives: The aim of this review was to systematically investigate long-term brain health in retired rugby players.

Methods: Six databases were systematically searched from inception to January 2018 using Medical Subject Headings and keywords. Two reviewers independently screened studies for inclusion. Cross-sectional studies of living retired male or female rugby players in which at least one cognitive test was used as an outcome measure were included. Data extraction was performed using Strengthening the Reporting of Observational Studies in Epidemiology guidelines. Methodological quality was assessed independently by two reviewers using the Downs and Black methodological quality tool.

Results: This review yielded six studies with an overall methodological quality of 'moderate'. A total of 672 male retired rugby players (mean ages of 38-52 years) were included in this review. Three studies investigated neuropsychological functioning in retired rugby players in comparison with controls, with no significant evidence of decreased performance in the majority of tests when compared with controls. Five out of the six studies explored self-reported measures of cognition. Three studies compared retired rugby players to controls, one of which found significantly increased subjective cognitive complaints among retired rugby players. The other two studies found that persistent postconcussion symptoms were associated with a higher number of self-reported concussions. Two studies reported decreased fine motor control in retired rugby players in comparison with controls. Neurometabolites and electrophysiological changes were explored by two studies, with minimal and non-significant findings.

Conclusions: Overall findings are mixed. Methodological biases reduce the overall study quality and limited the conclusions that can be drawn. Findings of decreased fine motor control in retired athletes may be influenced by lack of controlling for evidence of upper limb musculoskeletal injuries. While some studies show evidence of reduced cognitive function among former athletes, the results are not significantly lower than population norms. Cognitive findings from this review are inconsistent within and across study cohorts and are biased towards positive findings when self-report methods were selected. Current evidence suggests that large gaps remain in the understanding of the cause-and-effect relationships between playing rugby and long-term brain health in retired players.