Table 1

Data extraction

ReferenceObjectiveNumber of participants (n=); mean age (SD)Number of concussions:mean (SD)Definition of concussionCognitive outcome measuresFindingsDowns and Black Score; quality index
Gardner et al32To examine brain neurometabolite concentrations in retired rugby league playersRetired rugby players n=1638.3±(3)Controls n=1637.9±(4.9)Retired players reported an average of 33.44 (median=20; IQR=7–20; range 3–100) concussions,retired players reported an average of 5.9 concussions with LOC sustained during their careers (median=3.5; IQR=3.5–6; range 0–30).Not DefinedACS-TOPF, RAVLT, RCFT, TMT A and BCOWAT, WAIS-IV, RPQRetired players did not significantly differ in concentrations of 4 out of 5 neurometabolites tested. A significantly lower concentrations of grey matter glutathione (p=0.02) in retired players was detected. There were no significant differences between groups on measures of depression, anxiety or cognitive functioning.9; moderate
Lewis et al34To assess measures of corticomotor excitability and inhibition in retired rugby players.Elite rugby players n=2343±(7)Community-level rugby n=2845±(8)Retired non-contact sport controls n=2244±(9)Elite rugby players: 0 concussions (n=0; 0%)1–2 concussions (n=3; 13%)≥3 concussions (n=20; 87%)Community-level rugby:0 concussions (n=1; 4%)1–2 concussions (n=3; 11%)≥3 concussions (n=23; 85%)Retired non-contact sport controls:0 concussions (n=16; 75%)1–2 concussions (n=5; 21%)≥3 concussions (n=1; 4%)‘A blow to the head followed by a variety of symptoms that may include any of the following: headache, dizziness, loss of balance, blurred vision, “seeing stars”, feeling in a fog or slowed down, memory problems, poor concentration, nausea or throwing-up. Getting “knocked out” or being unconscious does NOT always occur with a concussion’.RPQ: predominantly early (RPQ-3) and late (RPQ-13) symptoms of brain injury.RMT was significantly higher, and LICI was greater in the elite rugby group compared with the control group.8; limited
Hume et al10To investigate cognitive function in former professional rugby players and assess the association between concussion history and cognitive function.Retired elite rugby n=10341.3±(7.5)Retired community rugby n=19544.9±(8.4)Retired non-contact sport Group n=6542.1±(7.7)Elite rugby=3.5±(2.0)Community rugby=2.9±(2.2)Non-contact=0.4±(0.8)‘A blow to the head followed by a variety of symptoms (LOC, headache, dizziness, loss of balance, blurred vision “seeing stars”, feeling in a fog or slowed down, memory problems, poor concentration, nausea or throwing up’.Online CNS-Vital Signs TestElite rugby group performed worse compared with non-contact sports on tests of complex attention −0.67 (−0.07 to −0.26) processing speed −0.51 (−0.89 to −0.12) executive functioning −0.41 (−0.80 to −0.02) and cognitive flexibility −0.37 (−0.74 to 0.00).11; limited
McMillan et al27 To investigate symptoms and a range of cognitive and health outcomes in retired rugby players with history of repeated concussion.Retired international rugby players n=5253.5±(13.0)Controls=2955.1±(9.0)Retired international rugby players 13.9±(18.9)Controls 0.3±(0.5)‘Being a blow or injury to your head where you may or may not have lost consciousness and then had symptoms, such as dizziness, blurred vision, nausea, vomiting, headache, poor concentration’.MOCA, SDT, TMT, RAVLT SART, JLO Test, Lafayette Grooved Pegboard, SF-36GOSERIRP performed poorer than controls on a test of verbal learning (p=0.022). No significant difference on the other cognitive tests were found (p>0.05).4; poor
Decq et al33 To assess the prevalence of major depressive disorder, mild cognitive disorders and headache in a population of retired rugby players.Age (years) median (IQR)Retired rugby players (RRPs)=23952 (49–55.75)Other retired sportsmen (ORS)=13852 (49–55)Retired rugby player: n=3.1±(5.01)Other sports: n=0.68±(1.83)Not definedSelf-administered questionnaireF-TICS-mA higher rate of major depressive disorder was observed among RRPs compared with ORS (p=0.04). The PHQ-9 score was increased with the number of reported concussions regardless of the type of sport (p=0.026). A higher rate of mild cognitive disorders was observed in RRPs compared with ORS (57% vs 40%) p=0.005.13; moderate
Thornton et al35 To examine the extent to which lifetime concussion exposure is associated with neurocognitive and symptomatic status in competitive versus recreational/retired players.Male and female studyretired players (all male) n=1639.25±(10.99)Recreational players n=1550.53±(9.80)Older players n=3144.71±(11.75)Competitive players n=8026.43±(6.53)Divided participants into no heavy concussion exposure groups (grade 2 or above) (n=37, 8:29), 1–2 heavy concussions (n=39, 4:35) and 3 or more (n=35, 1:34)Criteria from the American Academy of Neurology. Grade 1 – transient confusion that resolves within 15 min with no LOC. Grade 2 – transient confusions that persist with for more than 15 min with no LOC. Grade 3 – any LOC.ETS Kit, CCFT, WAIS-III, TMT-A and B,WMS-III, RAVLT, WCST, PCSCConcussion exposure did not predict neurocognitive functioning but did predict PCS. Participants with no heavy concussions reported significantly fewer memory complaints (d=−0.68), less distress (d=−0.76) and less overall (total) PCS (d=−0.65) than did those with three or more heavy concussions.12; moderate
  • ACS-TOPF, Advanced Clinical SolutionsTest of Premorbid Functioning; CCFT, Cattell’s Culture Fair Intelligence Test; COWAT, Controlled Oral Word Association Test; ETS Kit, Educational Testing Service; F-TICS-m, French version of the modified telephone interview for cognitive status; GOSE, Extended Glasgow Outcome Scale; JLO Test, Judgement of Line Orientation; LICI, long-interval intracortical inhibition; LOC, loss of consciousness; MOCA, Montreal Cognitive Assessment; PCS(C), Postconcussion Syndrome Checklist; PHQ-9, Patient Health Questionnaire; RAVLT, Rey Auditory Verbal Learning Test; RCFT, Rey Complex Figure Test; RPQ, Rivermead Post-concussion Symptoms Suestionnaire; RMT, resting motor threshold; SART, Sustained Attention to Response Task; SDT, Symbol Digit Test; SF-36, 36-Item Short Form Survey; TMT, Trail Making Test; WAIS, Wechsler Abbreviated Scale of Intelligence; WCST, Wisconsin Card Sorting Test; WMS, Wechsler Memory Scale.