Table 2

Relationship between concussion history and delayed recovery

PaperSubject characteristicsConcussion reportingOutcome measuresFindings/results
Guskiewicz et al31US College football athletes followed over 3 seasons (196 concussions were reported in 184 players, 12 repeat concussions)Prospective and retrospectiveGraded symptom checklist, health questionnaireSlowed recovery was associated with a history of previous concussions (30% of athletes reporting 3 or more previous concussions had symptoms lasting >1 week, compared with 14.6% of those reporting 1 previous concussion)
Slobounov et al103Male and female collegiate rugby players (38 players with no history of concussion, 9 with a repeat injury)ProspectiveSymptoms, NP testing, computerised balance measures (using a virtual reality system)All athletes were clinically asymptomatic at day 10 and allowed to return to competition. Balance deficits were present for at least 30 days after injury. Rate of recovery of balance function was significantly slower after a second injury
Echlin et al34Male fourth tier ice hockey players followed over 1 season (17 concussions, 5 of which suffered repeat concussion)Prospective and retrospectiveSCAT2 and computerised NP test batteryMinimal difference in return to play times between those who reported no previous concussions (8 players, mean 11.5±7.6 days to return to play) and 1 or 2 previous concussions (6 players 10.7±2.94 days). Two players who reported 3 or more previous concussions had delayed recovery
Benson et al17Professional ice hockey players followed over 7 seasons (559 concussions)ProspectiveSymptom checklist and time loss from sport postinjuryOn average, time loss (in days) increased 2.25× (95% CI 1.41 to 3.62) for every subsequent concussion
Castile et al12US high school students (data on 2417 concussions obtained from an injury surveillance database entered by certified athletic trainers)ProspectiveSymptoms and time to return to playSymptoms took 1 week to 1 month to resolve in 20.9% of recurrent concussions compared with 13.8% of new concussions (p=0.012). Similarly, symptoms in 6.5% of recurrent concussion took >1 month to resolve, compared to 0.6% of new concussions (p<0.001)
A greater proportion of athletes sustaining a recurrent concussion returned to play in >3 weeks (7.5%) or were medically disqualified (16.2%) than athletes sustaining a new concussion (3.8% and 2.9%)
  • NP, neuropsychological; SCAT2, Sport Concussion Assessment Tool 2.