Sports Related Brain Injury and Neurodegeneration in Athletes

Incidence Rates and Pathology Types of Boxing-Specific Injuries: A Systematic Review and Meta-analysis of Epidemiology Studies in the 21st Century

Background

To the best of our knowledge, an evidence-based investigation into 21st-century boxing-specific injury rates and types has yet to be performed.

Purpose

To provide an overview and quantitative synthesis of the incidence rates (IRs) and pathological categorizations of boxing-specific injuries in the 21st century.

Study Design

Systematic review; Level of evidence, 3.

Methods

Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we searched literature published from January 2000 to November 2021 in PubMed and the Cochrane Library systematically for qualifying epidemiology studies of organized boxing activities across the world. Two independent reviewers completed the literature review, data extraction, and quality assessment. The IRs of injuries per 1000 boxers (IR_N), per 1000 competition exposures (IR_E), and per 1000 minutes of competition (IR_C) or training (IR_T) were subsequently calculated. Single-arm meta-analyses were performed for the subgroups of different types of boxing. Sample size weighted means were calculated using a random-effects model in all studies with 95% CIs.

Results

Out of an initial 9584 articles, 14 studies were included, with most (11/14) having a moderate level of quality. The pooled IR_N in overall injuries was 223.9 (95% CI, 157.5-290.4), the IR_E was 233.3 (95% CI, 161.3-305.2), and the IR_C was 13.0 (95% CI, 8.9-17.1). In professional boxing, the IR_N (399.8), IR_E (379.8), and IR_C (23.9) were all significantly higher than in the amateur and female groups. The IR_E (76.6 vs 250.6; P < .000) and IR_C (9.2 vs 15.4; P < .000) in amateur boxing were significantly lower in studies between 2010 and 2019 than in earlier studies. For pathology categorization, the pooled frequencies were 12.3% (95% CI, 8.7%-15.9%) for concussion, 21.4% (95% CI, 14.1%-28.6%) for skin laceration, 30.2% (95% CI, 22.1%-38.2%) for soft tissue contusion, 15.3% (95% CI, 7.7%-22.9%) for sprain and muscle/ligament injury, and 11.4% (95% CI, 2.7%-20.1%) for fracture.

Conclusion

IRs of injury remain high in professional boxing, although they have decreased in the past 10 years in amateur boxing. Soft tissue contusion was the most common injury type. Better exposure measurements and epidemiologic indicators should be applied in future studies.

Registration

CRD42021289993 (PROSPERO).

Is dementia more likely following traumatic brain injury? A systematic review

BACKGROUND

The association between traumatic brain injury (TBI) and dementia is controversial, and of growing importance considering the ageing demography of TBI.

OBJECTIVE

To review the scope and quality of the existing literature investigating the relationship between TBI and dementia.

METHODS

We conducted a systematic review following PRISMA guidelines. Studies that compared TBI exposure and dementia risk were included. Studies were formally assessed for quality with a validated quality-assessment tool.

RESULTS

44 studies were included in the final analysis. 75% (n = 33) were cohort studies and data collection was predominantly retrospective (n = 30, 66.7%). 25 studies (56.8%) found a positive relationship between TBI and dementia. Clearly defined and valid measures of assessing TBI history were lacking (case-control studies-88.9%, cohort studies-52.9%). Most studies failed to justify a sample size (case-control studies-77.8%, cohort studies-91.2%), blind assessors to exposure (case-control-66.7%) or blind assessors to exposure status (cohort-3.00%). Studies that identified a relationship between TBI and dementia had a longer median follow-up time (120 months vs 48 months, p = 0.022) and were more likely to use validated TBI definitions (p = 0.01). Studies which clearly defined TBI exposure (p = 0.013) and accounted for TBI severity (p = 0.036) were also more likely to identify an association between TBI and dementia. There was no consensus method by which studies diagnosed dementia and neuropathological confirmation was only available in 15.5% of studies.

CONCLUSIONS

Our review suggests a relationship between TBI and dementia, but we are unable to predict the risk of dementia for an individual following TBI. Our conclusions are limited by heterogeneity in both exposure and outcome reporting and by poor study quality. Future studies should; (a) use validated methods to define TBI, accounting for TBI severity; (b) follow consensus agreement on criteria for dementia diagnosis; and (c) undertake follow-up that is both longitudinal, to determine if there is a progressive neurodegenerative change or static post-traumatic deficit, and of sufficient duration.

A systematic review on the risk of neurodegenerative diseases and neurocognitive disorders in professional and varsity athletes

Objective

The aim of this systematic review (SR) was to gather all available epidemiological evidence on former participation in any type of sport, at a professional and varsity level, as a potential risk factor for neurodegenerative diseases (NDs) and neurocognitive disorders (NCDs).

Design

Systematic searches were performed on PubMed, the Cochrane databases, and the ISI Web of Knowledge databases. Included studies were assessed using the NOS checklist.

Eligibility criteria for selecting studies

All epidemiological studies reporting data on the possible association between a clinical diagnosis of amyotrophic lateral sclerosis (ALS)/motor neuron disease (MND), dementia or mild cognitive impairment (MCI), Parkinson’s disease (PD), chronic traumatic encephalopathy (CTE) at any stage and with any clinical pattern and the former participation in any types of sport at a varsity and professional level were included.

Results

Data from the 17 included studies showed a higher frequency of NDs and NCDs in former soccer and American football players. Updating the previous SR confirmed a higher frequency of ALS/MND in former soccer players. Data reported a significantly higher risk of dementia/AD in former soccer players, and of MCI in former American football players. Results also showed a significantly higher risk of PD in former soccer and American football players, and a significantly higher risk of CTE in former boxers and American football players.

Summary/conclusions

This SR confirmed a higher risk of NDs and NCDs in former professional/varsity athletes. However, the pathological mechanisms underlying this association remain unclear, and further high-quality studies should be performed to clarify whether the association could be sport specific.