Heading football just once increases brain injury risk, study suggests

Heading a football just once may temporarily release brain injury markers into the blood, a study of amateur male players suggests.

The research found greater changes in certain blood markers associated with neural damage the harder and more often players headed the ball.

For two of the six proteins tracked, levels rose higher the more frequently and the harder players headed the ball.

The study authors said this could point to acute brain injury, but more research is needed to assess whether repeated heading could increase the risk of a neurodegenerative disease such as Alzheimer’s.

A neurodegenerative disease is a condition in which nerve cells gradually become damaged or die.

In research published on May 18, researchers at Amsterdam University Medical Center found that amateur football players who headed the ball had higher concentrations of S100B in their blood right after a match than players who did not perform headers.

S100B is a protein mainly produced by astrocytes, star-shaped cells that support nerve cells in the brain.

The protein is widely used to help assess traumatic brain injury, or TBI, which means damage to the brain caused by an external force, and usually increases within one hour after a TBI.

Players who performed more than two headers, or several high-impact headers, also showed immediate increases in p-tau217.

This protein is one of the main blood-based biomarkers associated with Alzheimer’s disease.

Biomarkers are measurable signs in the body that may point to a biological process, injury or disease.

Tau is a protein that normally helps stabilise the internal scaffolding of neurons, the brain’s nerve cells.

The study suggested mechanical stress on the brain’s transmission cables may detach tau, with enzymes then modifying it into forms including p-tau217.

Levels of S100B and p-tau217 returned to baseline within 24 to 48 hours after each match, but the authors said this does not rule out lasting harm.

Samantha Bureau, assistant executive director of the Concussion Legacy Foundation Canada, who was not involved in the study, said: “The evidence we have so far suggests that brain damage is occurring from heading soccer balls, both short and long-term.

“Long-term consequences are more difficult to track due to the latency between exposure and symptom onset, but several studies have raised concerns about the risks associated with heading in soccer.”

The study in the Netherlands used blood samples from 302 higher-level amateur male football players across 11 matches.

Samples were taken before matches, immediately after matches and again between 24 and 48 hours later.

While 86 participants did not take part in the third blood draw, study co-author Marsh Königs, assistant professor of developmental neuroscience at Emma Children’s Hospital at Amsterdam UMC, said this was unlikely to have affected the results.

Cameras were used to record how often each player headed the ball and to estimate the force of each header.

Königs said researchers do not yet know exactly how headers caused the biomarkers to rise.

One possible explanation is that rapid acceleration and deceleration of the head could create a smaller-scale “concussion-like” effect.

Concussion is a mild traumatic brain injury that can happen when the brain is shaken inside the skull.

Another study published in April found that when a person’s head makes contact with a ball, a pressure wave travels through the head.

Researchers said the effects of heading may build up over time, potentially contributing to neurodegenerative disease.

A 2025 study found that years of repeated head trauma in football players can kill neurons and lead to brain inflammation.

Königs said: “It’s not the rise in biomarkers itself but rather what it reflects, which is concerning.”

He said repeating the study among elite footballers could lead to more pronounced results.

Peter Theobald, a medical engineer leading research on brain biomechanics at Cardiff University, who was not involved in the study, said governing bodies such as England’s Football Association are reducing permitted heading practice, despite limited evidence defining a “safe” level.

He said it was difficult to say whether the biomarker concentrations measured in the Dutch study were enough to cause concern.

Königs said the biomarker elevations seen in the study did not exceed clinical thresholds used to diagnose more serious injuries.

However, he said those thresholds are mainly designed to detect severe brain injuries or dementia, and that repeated exposure over hundreds or thousands of headers remains a concern.

Theobald said: “This is a relatively strong study, as it also features athletes from non-contact sports and so does provide confidence that heading is the cause of change.

“Tracking the same players throughout a season would have been interesting for example, as this would have enabled reporting of the cumulative effect of heading.”