Narrative review: The spectrum of acute and chronic consequences of neurotrauma in professional and amateur boxing

Why this study matters

Boxers still die from injuries sustained in the ring, and repeated head injury can have lasting effects. The authors state that published figures on deaths and long-term harm may not reflect the real situation. They describe scientific evidence on sudden ringside deaths as “practically non-existent”. The main source of data is a collection of death reports that was not gathered as a scientific study. The authors add that an unknown number of deaths in unofficial bouts go unrecorded.

What the researchers did

The authors, who write as neurosurgeons, carried out a narrative review. A narrative review summarizes published work chosen by its authors. It does not follow the fixed search and selection rules of a systematic review. They searched PubMed and Google Scholar for terms such as mortality, boxing, acute subdural hematoma and concussion, and checked the reference lists of key articles.

They also analysed the latest version of the Velazquez collection of boxing deaths, which they requested in April 2023 from the person who updated and digitized it. The collection is built from clippings of boxing magazines, news articles and medical journal papers. The authors looked at age at death, historical period, location, type of bout, round, and whether the death followed a knockout (KO) or a technical knockout (TKO). A KO is when a boxer goes down and cannot get up before the referee counts to ten.

What they found

The collection lists 2076 deaths, about 10 a year. Of these, 294 (14.2%) date from 1720 to 1880, the bare-knuckle era, 993 (47.8%) from 1880 to World War II and 789 (38.0%) from after the war. The mean age at death was 23 years. Professional bouts accounted for 1505 deaths (73%), amateur bouts for 547 (26%) and Toughman contests, whose entrants generally have no professional and limited amateur experience, for 18 (1%).

Brain injury was the recorded cause of 1134 deaths (54.6%). Heart and lung causes accounted for 191 (9.2%), neck fractures for 27 (1.3%) and other causes for 724 (34.9%). A KO came before 1354 deaths (65.2%) and a TKO before 233 (11.2%). The article reports that 1670 of the fatalities (80.4%) happened in the ring, 313 (15.1%) within 24 hours after the bout and 89 (4.3%) later than that.

Recorded deaths fell after 1983, when professional bouts were shortened from 15 rounds to 12. The authors found no evidence that the rule change explains the fall. They cite an earlier analysis suggesting that shorter careers and fewer fights might be involved.

From earlier studies, the authors report that acute subdural hematoma, a bleed between the brain and its outer covering, is the most common life-threatening injury in boxing. They describe a period after concussion, lasting up to 7 to 10 days, in which the brain’s energy use is disturbed and it may respond less well to another injury. They also describe second impact syndrome, in which a second head injury before recovery from the first is followed by rapid brain swelling. For long-term harm, they cite sources reporting symptoms of chronic brain injury in up to 40% of retired professional boxers in the United States, and clinical dementia at an incidence of about 20%, far more often in professional than in amateur boxers.

Strengths and limits

The review covers acute injury, death and long-term effects in one article, and its fatality counts come from the latest version of the collection.

The authors state the limits of that collection. It was not built with scientific methods. Its information comes from newspaper articles and not from national databases or other verified sources, so the data may be incomplete or incorrect. The authors did not carry out a full analysis and point to an earlier, more thorough one. The figures are counts of recorded deaths. The article does not relate them to the number of boxers or bouts.

As a narrative review, the article does not describe how studies were selected or assess their quality. Some of the long-term figures are quoted from single earlier sources. The 40% figure, for example, is cited from an online guide. The authors found very little data on brain injury in female boxers, and the review reports none.

What it adds to research on fighter health

The article sets recent counts from the main source of data on boxing deaths beside a summary of acute and chronic brain injury in the sport. The authors conclude that deaths and long-term harm continue despite rule changes, and that their true extent is poorly known. They call for systematic registration of boxing deaths, for biomechanical studies of protective equipment and for research on female boxers. They suggest that similar considerations apply to other combat and contact sports.