Brain measures after fighters stop competing

What does this study show about cognition, brain structure and a blood marker of nerve-cell injury after fighters stop competing, and how firmly can the changes be attributed to stopping?

By Casey C. Sears (ORCID 0009-0000-6344-1143). Fight Medicine Research Institute, Tuscaloosa, Alabama, United States.

EA-001. Selected-paper appraisal of one published source. Version 1.2, . Not a systematic review, a clinical review or new data.

Source appraised

Xiaowei Zhuang, Lauren Bennett, Rajesh Nandy, Dietmar Cordes, Charles Bernick, Aaron Ritter. Longitudinal Changes in Cognitive Functioning and Brain Structure in Professional Boxers and Mixed Martial Artists After They Stop Fighting. Neurology. 2022;99(20):e2275-e2284. https://doi.org/10.1212/wnl.0000000000201158

Library record FH-004, with the source’s population, rights and publication status. The authors, journal and DOI are the source’s own.

Design and findings

A matched longitudinal comparison included 45 male fighters who stopped competing and sparring and 45 who remained active. Cognitive testing and MRI were repeated; about half had repeated neurofilament-light measurements. The inactive group improved on several cognitive measures and had lower neurofilament-light levels, while cortical-thickness trajectories differed between groups.

Methodological appraisal

Repeated measurements and demographic matching strengthen the comparison. Retirement was not randomized. Baseline cognitive differences, unmeasured fatigue and mood, incomplete biomarker sampling, and imprecise head-impact exposure complicate attribution. The study included no women or nonfighter controls. Measured outcomes included cognitive performance, cortical thickness, and neurofilament-light levels.

Fight Medicine Research Institute contribution

Study-design appraisal, examination of exposure measurement and confounding, and identification of outcomes relevant to long-term fighter follow-up.

Publication record

Output
EA-001 in the Fight Medicine Research Institute’s output register.
Type
Selected-paper appraisal. It covers one source and makes no claim about the wider literature.
Author

Casey C. Sears, Fight Medicine Research Institute, Tuscaloosa, Alabama, United States. ORCID: https://orcid.org/0009-0000-6344-1143

An LLM was utilized as a research tool with direct human oversight.

Version

Version 1.0, . First published.

Version 1.1, . Author, ORCID iD, output number and structured review record added. Funding statement corrected. The appraisal text is unchanged.

Version 1.2, . Second qualified review by David Williams, MD, recorded. The appraisal text is unchanged.

Method
One published source, appraised under policy P-05. Figures and limitations were checked against the source’s full text. Access basis: Full text at PubMed Central (PMC9694836).
Participants
None. The work used published literature only, with no human participants and no participant data.
Funding

Funding was received for this work. The funder is not yet named in this record. For the source’s own funding and disclosures, see the source.

Correction. This page earlier gave the funding as “None”. Funding was received for this work. The statement was corrected on 10 November 2026.

Conflicts
The author’s interests are listed under Disclosed interests.
Identifier
This appraisal has no DOI. Its permanent address is https://fightmed.institute/evidence-appraisals/brain-measures-after-fighters-stop-competing/. The DOI under “Source appraised” belongs to the source article.
Cite as
Sears CC. Brain measures after fighters stop competing [selected-paper appraisal]. Version 1.2. Fight Medicine Research Institute; 2026. https://fightmed.institute/evidence-appraisals/brain-measures-after-fighters-stop-competing/
Source notices
No correction, retraction or expression of concern was found in PubMed, Crossref or Scite when this record was checked.

Review record

Each review of this appraisal is listed with who did it and what it covered. A review is credited only after it has been carried out.

  1. Editorial approval

    Completed

    Reviewer
    Casey C. Sears, Founder
    Expertise
    Combat-sports regulation; ringside clinical operations; emergency care; refereeing and judging
    Independence
    Not independent. The approving editor is the author.
    Scope
    Figures and limitations checked against the source’s full text. Approval to publish as a selected-paper appraisal.
    Date
    Decision
    Approved for publication
    Record
    Publication approval of 9 November 2026.

  2. Second qualified review

    Completed

    Reviewer
    David Williams, MD
    Expertise
    Sports medicine
    Independence
    Independent of the author, the Fight Medicine Research Institute, Fight Medicine Journal and its publisher, as stated by the author.
    Scope
    The appraisal checked against its source, as required by policy P-05.
    Date
    Decision
    Approved as written. No changes required.
    Record
    Reported to the output register by the author on 10 November 2026.

  3. Methods or statistical review

    Not assigned

    Policy P-05 assigns this review according to content. None has been assigned or carried out.

  4. Clinical review

    Not assigned

    Policy P-05 assigns this review according to content. None has been assigned or carried out. This appraisal is not clinical guidance.

The rules are in policy P-05. Approving editor: Casey C. Sears, Founder. An LLM was utilized as a research tool with direct human oversight.

Research program: Chronic traumatic encephalopathy (CTE)

Report an error in this appraisal: corrections@fightmed.institute