Soccer’s developing headcase

Bad news for soccer fans: a new study suggests repetitive headers and accidental head impacts in the sport are leading to changes in brain signalling that could have long-term implications for brain health.

In this small-sample, exploratory study, experts from the Norwegian School of Sport Sciences analysed blood samples from 89 professional soccer players, as well as samples generated by other high intensity exercise that does not involve head impacts.

The results, published in the journal Brain Injury, showed specific alterations in the levels of the brain’s microRNAs – blood biomarkers associated with signalling pathways in the brain. These micoRNAs were found to be unaffected by other high-intensity sports that did not involve head impacts.

“This is a relatively small sample-size exploratory study,” says Stian Bahr Sandmo, of the Oslo Sports Trauma Research Centre at the Norwegian School of Sport Sciences. “But future findings expanding upon our research could ultimately lead to an improved understanding of the potential hazardous effects of repetitive head impacts.

“With millions of people playing soccer worldwide, this might ultimately have a substantial influence on public health.”

MicroRNAs – small molecules found in our cells and blood –help to regulate gene expression. The researchers used bioinformatics to identify what genes were targeted by the eight microRNAs deregulated by these head impacts, to better understand their roles in the brain’s signalling.

They found that the target genes affected were linked to 12 signalling pathways, including the Wnt pathway. Wnt signalling is an important pathway at the synapse, required for synaptic plasticity and maintenance in the adult brain. But the different kinds of injury affected different microRNAs, so understanding the type of impact may help medical professionals to assess the damage when looking at a person with sports-related brain injuries.

Understanding these subtleties is important, because not all sports-related brain injuries are the same. For example, evidence shows that female soccer players are at much higher risk of head injuries than their male counterparts, but these injuries are most likely to come from colliding accidentally with an object, like the goalpost or the ball itself, rather than through repetitive headers.

The header is an iconic move in soccer, so understanding its impacts on brain health is important. And this isn’t the first time the move has come under scrutiny; in 2018, a study found purposeful headers were more likely to lead to concussion than other accidental head impacts in the sport.

That’s important, because repetitive concussions are known to cause long-term brain injuries.

Soccer isn’t the only sport to come under scrutiny in recent years; the Australian-rules Football league has faced intense pressure to address its mounting concussion problem. In June last year, a five-year study found AFL players are returning to play from concussion with high levels of damaged brain cells, putting them at risk of long-term effects.