Health Council of the Netherlands Reports 2003 - Gezondheidsraad

Incidence of brain injury
Not a great deal is known about the prevalence of brain injury in boxing or other
fighting sports. Given that inflicting brain injury is one of the intrinsic aims of
boxing in particular, little or no research has been conducted into the prevention
of such injuries. No attempt has ever been made to quantify the incidence of
acute brain injury in professional boxers. However, studies showed that one in
eight amateur contests ends in concussion. Information from the Amateur
International Boxing Association (AIBA) indicates that the percentage of
contests at world championship and Olympic tournaments stopped because of
brain injury has declined in recent decades, from about 10 per cent to no more
than 3 per cent. This may indicate a fall in the incidence of concussion at such
tournaments, but this possibility has not been investigated. It has been
convincingly demonstrated that between 40 and 80 per cent of professional
boxers suffer chronic brain injury. The seriousness of the abnormalities appears
to be related to the number of bouts. Amateur boxers are also affected by chronic
brain injury, but no data on the incidence is available and the evidence suggests
that the problem is much less serious than among professional boxers.
With regard to soccer, the most informative research data indicates that there
are six cases of concussion in every ten thousand men’s matches/training
sessions, and four cases in every ten thousand women’s matches/training
sessions. The average player has about a 50 per cent chance of suffering
concussion at some point in his/her playing career. There is no evidence to
suggest that heading the ball can cause concussion. The Committee knows of
only one study reported to date that looked at the subject of chronic brain injury
in ex-professional soccer players. Neuropsychological tests indicated that eight
of the ten former players participating exhibited abnormalities (albeit mild in
some cases). It is not clear to what extent the subjects are comparable with
modern-day players, since various aspects of the game have changed over the
years. Studies involving active soccer players have produced mixed findings;
some have suggested that soccer is associated with chronic brain injury, while
others have found no link. Notably, chronic injury has been observed only in
players who have executed more than a thousand headers.
The interpretation of data on sports-related brain injuries is complicated by
significant inter-study inconsistency in the definition of acute and chronic brain
injury. In fact, the findings of the studies reported to date cannot properly be
compared. If insight into the incidence of acute and chronic sports-related brain
10 Health Council of the Netherlands; Reports 2003