Could heading the ball in soccer lead to degenerative brain disease, like that seen in athletes in other sports?

That's the question addressed by a review in the January issue of Neurosurgery, official journal of the Congress of Neurological Surgeons.

As yet there's not clear evidence to link heading to short- or long-term brain injury, according to Dr Alejandro M. Spiotta of the Cleveland Clinic and colleagues. However, while research is ongoing, they stress the need for proper heading technique at all levels of organized soccer.

New Review of Evidence on Heading and Brain Injury Risk in Soccer

Soccer (called football outside the United States) is the only sport in which players use their unprotected heads to intentionally deflect, stop, or redirect the ball. Headed balls travel at high velocity both before and after impact, raising concerns about possible traumatic injury.

In 2002, English footballer Jeffrey Astle, known as a "formidable header," died with degenerative brain disease. The damage was consistent with chronic traumatic encephalopathy (CTE): a progressive neurodegenerative disease caused by repeated brain injury, seen in American football players and other athletes. Those reports have prompted concerns about similar risks in soccer players.

Although concussions are common in soccer, they more often result from the head striking another player or the goalpost, rather than heading the ball. But there's still concern about long-term injury related to repetitive trauma from heading.

Detailed biomechanical studies have been performed, showing that heading is a complex task in which significant energy is absorbed by the head. Emphasizing the importance of proper heading technique, studies have shown that anticipation and "pre-tensing" of the neck muscles play a key role in absorbing and redirecting the impact of a headed ball.

Pending Further Research, Emphasis on Proper Heading Technique

Older studies reported symptoms related to heading ("footballers' migraine"), but more recent research has not confirmed those effects. One factor may be the introduction of newer soccer balls that don't absorb moisture -- unlike the leather balls used in Jeffrey Astle's day.

Soft headgear has been suggested to protect against soccer-related head injuries, although studies have questioned the protective benefits. There are even concerns that wearing headgear might even lead to increased injury risk, if players develop a false sense of security.

For now, the data on heading and brain injury "leave us somewhat in the grey zone," according to Dr Spiotta and colleagues. While it's reassuring that there's no clear link to CTE, the potential for long-term brain injury remains. "Even if the cognitive impairment were to be mild, it would still present a major medical and public health concern because of the massive volume of soccer players worldwide," the researchers write. "Any possible detrimental effect…may only become clinically evident decades in the future."

Dr Spiotta and coauthors emphasize the need for further research -- including autopsy studies of players in the "light ball" era -- to see if there is any similarity to the patterns of brain injury seen in CTE. Meanwhile, "Proper heading technique should continue to be stressed at all levels of play." The authors also highlight the importance of using an age-appropriate ball size for younger soccer players, as they develop the neck strength and posture control needed for proper heading technique.