Monday, April 7, 2008

Headers, Neurochemistry and Brain Injury

In an effort to understand neurological problems associated with competitive sports, researchers have turned to investigations of various neurochemical markers of brain injury. S-100B is a neurochemical, a protein that is normally found in the brain. It is released into the blood immediately following an acute brain injury. Increased blood concentrations of S-100B have been found in traumatic brain injured patients immediately after injury. Some suggest that elevated blood concentrations in athletes might be indicative of head trauma and possible brain injury. A recent study in the journal Biomarker Insights shows that heading a soccer ball does not affect blood levels of S-100B. It appears to acquit heading as a potential cause of brain injury in soccer players. Despite this, it re-opens the discussion surrounding acute and long term head injuries, brain damage and headers. A full understanding of the available research helps understand why this issue remains controversial.

Earlier studies attempted to associate soccer, more specifically heading the ball, with diminished brain function. The first reports in the early 1990s linked cognitive dysfunction and neurological abnormalities to a history of playing soccer. This led some to conclude that soccer heading could cause chronic brain injury as seen in other sports such as boxing. Other studies, however failed to show any evidence of neurological brain damage in soccer players and many have questioned the experimental methods used in the early studies. Nevertheless, the idea that heading the ball may cause brain injury has persisted.

This controversy gave birth to a new industry promoting the use of protective headgear. Proponents of the protective headgear argue that repeated heading can raise the risk of brain damage. Use of the headgear lessens the impact force of heading the ball and reduces the chance of long-term brain damage. To bolster their argument, they cite several studies where blood levels of S-100B were found to be elevated following a soccer match. Two studies published in 2004 and 2006 showed elevated post-match S-100B in both men and women and that the levels were loosely correlated with the number of times the ball was headed. Therefore, since S-100B is elevated in the blood of brain injured patients, the increases found in the soccer players must be indicative of brain trauma.

Unfortunately, the above discussion of blood S-100B and soccer matches tells only part of the story. What is missing is a more thorough analysis of S-100B, exercise and head injury. First, following a soccer match, blood levels of S-100B may rise from around 0.10 to 0.15 ug/l. In brain injured patients, S-100B levels raise to a much greater level, some six to ten times that seen following a soccer match, to near 1.0 ug/l. While the post-match increases may be “statistically” significant, there is debate as whether such small changes have any “biological” significance. Second, several studies show that S-100B levels are elevated following several types of non-contact activity including basketball, running and swimming. In these activities, there is little evidence of trauma to the head. In training sessions with and without heading drills, S-100B increases are similar. S-100B is also elevated following orthopedic fractures and minor bruising. Thus, the increases in S-100B following a soccer match may simply reflect the effects of strenuous exercise and/or minor injuries rather than head trauma.

This discussion emphasizes that before firm conclusions can be drawn, coaches, players and parents should collect information and examine all sides of an issue before arriving at a conclusion. Don’t be mislead by a few, strategically selected pieces of information. Don’t base your conclusions on a single research study. Make sure you have the full picture. While some might argue that heading causes neurological changes in the brain, a complete analysis of the available evidence strongly suggests that there are no long term, adverse effects of this activity.

Further Reading

Mussack T, Dvorak J, Graf-Baumann T, Jochum M (2003) Serum S-100B protein levels in young amateur soccer players after controlled heading and normal exercise. European Journal of Medical Research, 8:457-464.

Otto M, et al. (2000) Boxing and running lead to a rise in serum levels of S-100B protein. International Journal of Sports Medicine, 21:551-558.

Stalnacke B-M, Sojka P (2008) Repeatedly heading a soccer ball does not increase serum levels of S-100B, a biochemical marker of brain tissue damage: an experimental study. Biomarker Insights, 3:87-91.

Stalnacke BM, Ohlsson A, Tegner Y, Sojka P (2008) Serum concentrations of two biochemical markers of brain tissue damage S-100B and neurone specific enolase are increased in elite female soccer players after a competitive game. British Journal of Sports Medicine. 2006, 40:313-316.

Unden J, Bellner J, Eneroth M, Alling C, Ingebrigtsen T, Romner B (2005) Raised serum S100B levels after acute bone fractures without cerebral injury.
Journal of Trauma, 58:59-61.

Zetterberg H, et al. (2007) No neurochemical evidence for brain injury caused by heading in soccer. British Journal of Sports Medicine, 41:574-577