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What is the risk of recurrent concussion in children and adolescents aged 5–18 years? A systematic review and meta-analysis
  1. Jacqueline van Ierssel1,
  2. Martin Osmond1,2,3,
  3. Jemila Hamid1,4,
  4. Margaret Sampson1,
  5. Roger Zemek1,2,3
  1. 1Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada
  2. 2Emergency Department, Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada
  3. 3Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada
  4. 4Department of Mathematics and Statistics, University of Ottawa, Ottawa, Ontario, Canada
  1. Correspondence to Dr Jacqueline van Ierssel, Children's Hospital of Eastern Ontario Research Institute, Ottawa, ON K1H 5B2, Canada; JMinnes{at}


Objective We aimed to examine the risk of concussion in children with a previous history of concussion.

Design Systematic review and meta-analysis. The primary outcome was number of children with and without a previous lifetime history of concussion who sustained a diagnosed concussion within each study period. Risk of bias was assessed using the Newcastle-Ottawa Scale. A random effects model was used to estimate a pooled risk ratio (RR) with corresponding 95% CIs; results were summarised in forest plots.

Data sources Four electronic databases (MEDLINE, Embase, CINAHL, SPORTDiscus) and selected reference lists were searched (PROSPERO registration No CRD42019135462).

Eligibility criteria Original English language peer-reviewed publications that compared concussion risk in children aged 5–18 years with and without a previous concussion history in which risk estimates were reported or able to be calculated.

Results Of 732 identified studies, 7 studies representing 23 411 children (risk of bias range, 7–9; maximum possible score=9) were included for meta-analysis. Pooled risk of sustaining a concussion was more than three times greater in children with a previous concussion compared with those with no previous concussion (RR=3.64; 95% CI: 2.68 to 4.96; p<0.0001; I2=90.55%). Unreported sex-stratified data precluded direct comparison of concussion risk in male versus female athletes.

Conclusion Previously concussed children have four times the risk of sustaining a concussion compared with those with no previous concussion history. This should be a consideration for clinicians in return to sport decision-making. Future studies examining subsequent recurrent concussion in youth sports must consider sex differences.

  • concussion
  • children
  • risk factor
  • sporting injuries
  • recurrent

Statistics from


  • Contributors JvI, MS and RZ contributed to the conception or design of the work. JvI, MO and JH collected the data. JvI, MO and JH contributed to the analysis and interpretation of the work. Jvl drafted the manuscript. MO, MS, JH and RZ critically reviewed the manuscript for important intellectual content. All authors approve of the final version and agree to be responsible for all aspects of the work ensuring accuracy and integrity.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests Jvl reported receiving speaking honoraria and travel expenses for presentations at scientific meetings; and is founder and an instructor for R2P Concussion Management. RZ reported being a coapplicant on a competitively funded grant administered by the National Football League through the independent scientific advisory board to fund a prospective concussion study with the goal of preventing concussions; he does not personally receive any funding for this work; his institution receives the operating funds to conduct the research; he has received honoraria from Parachute Canada (a Canadian non-profit for injury prevention) for his role on the Concussion Expert Advisory board.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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