What is the association of field position, career length, and playing era with risk of neurodegenerative disease in male former professional soccer players?
In this cohort study of 7676 Scottish male former professional soccer players and 23 028 general population control individuals matched by sex, year of birth, and area socioeconomic status, risk of neurodegenerative disease among former soccer players varied by field position and career length but was similar across era of participation.
In this study, risk of neurodegenerative disease was higher among former professional soccer players with longer careers and among those in nongoalkeeper positions, indicating that factors associated with nongoalkeeper positions should be scrutinized to mitigate risk; meanwhile, strategies to reduce head impact exposure may be advisable to reduce negative outcomes in this population.
Neurodegenerative disease mortality is higher among former professional soccer players than general population controls. However, the factors contributing to increased neurodegenerative disease mortality in this population remain uncertain.
To investigate the association of field position, professional career length, and playing era with risk of neurodegenerative disease among male former professional soccer players.
Design, Setting, and Participants
This cohort study used population-based health record linkage in Scotland to evaluate risk among 7676 male former professional soccer players born between January 1, 1900, and January 1, 1977, and 23 028 general population control individuals matched by year of birth, sex, and area socioeconomic status providing 1 812 722 person-years of follow-up. Scottish Morbidity Record and death certification data were available from January 1, 1981, to December 31, 2016, and prescribing data were available from January 1, 2009, to December 31, 2016. Database interrogation was performed on December 10, 2018, and data were analyzed between April 2020 and May 2021.
Participation in men’s soccer at a professional level.
Main Outcomes and Measures
Outcomes were obtained by individual-level record linkage to national electronic records of mental health and general hospital inpatient and day-case admissions as well as prescribing information and death certification. Risk of neurodegenerative disease was evaluated between former professional soccer players and matched general population control individuals.
In this cohort study of 30 704 male individuals, 386 of 7676 former soccer players (5.0%) and 366 of 23 028 matched population control individuals (1.6%) were identified with a neurodegenerative disease diagnosis (hazard ratio [HR], 3.66; 95% CI, 2.88-4.65; P < .001). Compared with the risk among general population control individuals, risk of neurodegenerative disease was highest for defenders (HR, 4.98; 95% CI, 3.18-7.79; P < .001) and lowest for goalkeepers (HR, 1.83; 95% CI, 0.93-3.60; P = .08). Regarding career length, risk was highest among former soccer players with professional career lengths longer than 15 years (HR, 5.20; 95% CI, 3.17-8.51; P < .001). Regarding playing era, risk remained similar for all players born between 1910 and 1969.
Conclusions and Relevance
The differences in risk of neurodegenerative disease observed in this cohort study imply increased risk with exposure to factors more often associated with nongoalkeeper positions, with no evidence this association has changed over the era studied. While investigations to confirm specific factors contributing to increased risk of neurodegenerative disease among professional soccer players are required, strategies directed toward reducing head impact exposure may be advisable in the meantime.
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CME Disclosure Statement: Unless noted, all individuals in control of content reported no relevant financial relationships. If applicable, all relevant financial relationships have been mitigated.
Accepted for Publication: May 27, 2021.
Published Online: August 2, 2021. doi:10.1001/jamaneurol.2021.2403
Correction: This article was corrected on September 9, 2021, to add data that were missing from eTables 2 and 3 in the Supplement.
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Russell ER et al. JAMA Neurology.
Corresponding Author: William Stewart, MBChB, PhD, Department of Neuropathology, Queen Elizabeth University Hospital, 1345 Govan Rd, Glasgow G51 4TF, United Kingdom (firstname.lastname@example.org).
Author Contributions: Ms Russell and Dr William Stewart had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: K. Stewart, MacLean, Pell, W. Stewart.
Acquisition, analysis, or interpretation of data: Russell, Mackay, Pell, W. Stewart.
Drafting of the manuscript: Russell, W. Stewart.
Critical revision of the manuscript for important intellectual content: Mackay, K. Stewart, MacLean, Pell, W. Stewart.
Statistical analysis: Russell, Mackay, Pell, W. Stewart.
Obtained funding: W. Stewart.
Administrative, technical, or material support: K. Stewart, MacLean.
Supervision: Mackay, W. Stewart.
Conflict of Interest Disclosures: Ms Russell reports grants from the Football Association and Professional Footballers Association during the conduct of the study. Dr William Stewart reports grants from the Football Association, the Professional Footballers Association, and National Health Service Research Scotland during the conduct of the study, and is a nonremunerated member of the Football Association’s Expert Panel on Concussion and Head Injury in Football and of the Fédération Internationale de Football Association (FIFA) Independent Football Concussion Advisory Group. No other disclosures were reported.
Funding/Support: This study received funds from the Football Association and the Professional Footballers Association, as well as funds paid to Dr William Stewart from the National Health Service Research Scotland and the US National Institute of Neurologic Disorders and Stroke (grant U54NS115322).
Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
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