Soccer heading can alter brain chemistry, new research shows

Amateur Sydney soccer player Oliver Lee-Young remembers countless heading sessions when he was an aspiring young player.

"My dad took me to the park in the north of Sydney and we used to practice heading all the time, coaches as well, the school programs, all that kind of thing," Lee-Young said.

"It's so important — you can't really play the game without heading for defence, for attack, for scoring goals, for pretty much every facet of the sport."

But Lee-Young said new research that has found any soccer heading alters the brain's chemistry and electrical activity has given food for thought.

The work, published today in the journal Sports Medicine — Open, found changes in the brains of players who participated in a heading study by researchers at the University of Sydney and Griffith University.

"Overall, I'd say we found that soccer heading has a subtle effect on the brain even when there's no concussion and cognitive impairment detected," said researcher Dr Danielle McCartney, a research fellow at the Lambert Institute of Cannabinoid Therapeutics at Sydney University.

The study recruited 15 male amateur soccer players between the ages of 18 and 35 to head a ball launched 20 times in 20 minutes from a machine at a fixed distance and speed.

The players then underwent MRI scans and gave blood samples.

Dr McCartney said the results showed the players' brain chemistry had changed immediately after doing the headers.

"We found altered electrical conductive and altered chemistry in certain regions of the brain," she said.

The changes included altered chemistry in a part of the brain involved in motor control and decreased electrical conductivity across several areas.

"We also found that two blood biomarkers, which have previously been associated with head trauma and dementia, were elevated following the heading task," Dr McCartney said.

The blood samples showed elevated levels of two proteins, GFAP and NFL.

Elevated levels of these two proteins are also seen in cases of concussion and dementia, albeit at much higher levels than were seen in the study's participants.

These proteins are currently considered some of the best available blood biomarkers of brain injury and future dementia risk.

But Dr McCartney was quick to point out that the players in the study didn't suffer any cognitive effects.

"It tells us that they (the effects) are subtle," she said.

"It tells us that we need to do further work to really understand the clinical and long-term significance of these effects."

Dr Nathan Delang, who led the research as a PhD candidate and is now a postdoctoral researcher at the University of Queensland, said more studies were being done to understand the patterns.

"Elevated levels of these biomarkers indicate brain cells have been disturbed at a microstructural level," Dr Delang said.

"The clinical and long-term significance of such small elevations is still being studied, particularly in relation to how much, and what pattern, of exposure might lead to effects on brain structure and function."

But Dr McCartney said determining the long-term impact of soccer heading was difficult because it was virtually impossible to sort out the effects of sub-concussive knocks — like heading a soccer ball — from more severe head knocks.

"Often people who are experiencing a lot of non-concussive impacts are also experiencing concussive impacts, and so, it makes it hard to do these observational studies," she said.

"Our research shows that heading has acute effects on the brain.

"Certainly, we need more studies to determine whether or not these effects persist, whether they not they accumulate over time.

"Those kinds of things will help us better understand the effects of heading on long-term health."

The research will add to the debate in Australia about whether children should be allowed to head the ball.

In the United States and the United Kingdom, young children are banned from heading until they're in their early teens.

Certain clubs in Australia have also initiated a ban, but it hasn't been adopted across the country.

In a statement, Football Australia said it released updated guidelines on concussion for junior and community sport last month.

"Junior football is played on smaller fields, with a reduced number of players and small goals," the statement said.

"Modifications to the laws of the game, including no throw-ins and the requirement for goalkeepers to release the ball by rolling or throwing, help reduce the incidence of heading at a junior level.

"Football Australia has approved an expert project team to consider a Football Australia Expert Working Group's suggestions on strategies to reduce the incidence, magnitude and burden of heading in youth football, commencing with a comprehensive literature review."

Lee-Young said the University of Sydney research might make people consider the potential dangers of heading, but he didn't believe it would ever be banned from the game.

"It's like saying you can't bowl a bouncer in cricket — it's part of the sport. It wouldn't really be soccer with heading," he said.

"But for kids, it might be a different story."

Dr McCartney said there needed to be caution.

"As a starting point, I think we need to be exercising caution in and around heading," Dr McCartney said.

"Making an effort to limit exposure as appropriate.

"Undertaking intense training sessions involving a lot of heading might not be the best plan based on our results."