Background: Despite changes in rules and equipment, boxing has been associated with a range of acute and chronic injuries, especially those related to the brain. Because of a suspected association between boxing and chronic traumatic brain injury, organizations in several countries have called for a ban on the sport. Loosemore and colleagues examined the evidence associating chronic traumatic brain injury with participation in amateur boxing.

The Study: The systematic review included a search of several electronic databases and the bibliographies of relevant papers and books to identify studies of the association between amateur boxing and chronic traumatic brain injury. Each study was assessed for quality based on prospective study design, comparability of groups, adjustment for confounding factors, duration of follow-up, outcomes, statistical analysis, and strategies to avoid bias. Whenever possible, original data were extracted from each study for the analysis.

Results: Out of more than 900 citations, 36 articles met the inclusion criteria. Seventeen studies were case series, 11 were case-control studies, four were controlled before and after studies, and four were cohort studies. Outcome assessments were psychometric testing (16 studies), electroencephalography (EEG; 14 studies), neurologic examination (12 studies), and brain imaging (11 studies). Several studies used more than one outcome assessment. Overall study quality was poor.

Several studies used different designs to assess changes in psychometric tests. Most of these studies found no significant effect, and boxers outperformed persons in the control group in three studies. Studies of brain imaging, including computed tomography (CT) and single-photon emission CT, found no consistent abnormalities in boxers and no correlation between imaging findings and psychometric and other test results. EEG was used until the 1960s. Early studies reported acute EEG changes in about one half of the boxers studied; however, more recent studies with longer follow-up reported no consistent changes from baseline or when compared with controls when adjusted for age. Several studies using neurologic examination reported positive findings, especially in high-exposure boxers. Nevertheless, these studies showed a wide variation in the type, prevalence, and severity of neurologic abnormalities. Regardless of the outcome measure, only four (24 percent) of the higher-quality studies indicated an association between chronic traumatic brain injury and amateur boxing.

Conclusion: The authors conclude that there is no strong evidence associating amateur boxing with chronic traumatic brain injury.