A recently published review of 45 studies concluded that approximately half of individuals who sustain a single mild traumatic brain injury (MTBI) experience long-term cognitive impairment (McInnes et al. Mild Traumatic Brain Injury (mTBI) and chronic cognitive impairment: A scoping review. PLoS ONE 2017;12:e0174847). Stratified by age, they reported that 50% of children and 58% of adults showed some form of cognitive impairment. We contend that the McInnes et al. review used a definition of “cognitive impairment” that was idiosyncratic, not applicable to individual patients or subjects, inconsistent with how cognitive impairment is defined in clinical practice and research, and resulted in a large number of false positive cases of cognitive impairment. For example, if a study reported a statistically significant difference on a single cognitive test, the authors concluded that every subject with a MTBI in that study was cognitively impaired–an approach that cannot be justified statistically or psychometrically. The authors concluded that impairment was present in various cognitive domains, such as attention, memory, and executive functioning, but they did not analyze or report the results from any of these specific cognitive domains. Moreover, their analyses and conclusions regarding many published studies contradicted the interpretations provided by the original authors of those studies. We re-reviewed all 45 studies and extracted the main conclusions from each. We conclude that a single MTBI is not associated with a high incidence of chronic cognitive impairment.
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Bibliographical noteFunding Information:
The author(s) received no specific funding for this work. GLI has received salary support from the Harvard Integrated Program to Protect and Improve the Health of National Football League Players Association Members. He acknowledges unrestricted philanthropic support from ImPACT Applications, Inc., the Heinz Family Foundation, and the Mooney Reed Charitable Foundation. NDS received salary support from a Clinician-Scientist Career Development Award from the Vancouver Coastal Health Research Institute and a Health Professional Investigator Award from the Michael Smith Foundation for Health Research. AJG has previously received grant funding from the NSW Sporting Injuries Committee, the Brain Foundation (Australia), the Hunter Medical Research Institute (HMRI), supported by Jennie Thomas, and HMRI, supported by Anne Greaves. He is currently funded through an NHMRC Early Career Fellowship, the HNELHD Research, Innovation and Partnerships – Health Research & Translation Centre and Clinical Research Fellowship Scheme, and the University of Newcastle’s Priority Research Centre for Stroke and Brain Injury.
© 2019 Iverson et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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