Reference | Objective | Number of participants (n=); mean age (SD) | Number of concussions:mean (SD) | Definition of concussion | Cognitive outcome measures | Findings | Downs and Black Score; quality index |
Gardner et al 32 | To examine brain neurometabolite concentrations in retired rugby league players | Retired 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 Defined | ACS-TOPF, RAVLT, RCFT, TMT A and BCOWAT, WAIS-IV, RPQ | Retired 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 al 34 | To 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 al 10 | To 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 Test | Elite 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 al 27 | 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-36GOSE | RIRP 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 al 33 | 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 defined | Self-administered questionnaireF-TICS-m | A 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 al 35 | 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, PCSC | Concussion 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.