Whether it's at practice or during a Fifa World Cup match, football players could unknowingly be putting their brain health at risk every time they take to the field.
Studies suggest that retired football players have a higher risk of developing dementia , particularly Alzheimer's disease , compared to the general population. It's currently thought that this increased risk is partly being driven by performing one particular skill: heading the ball.
Research testing the effects of repeated heading impacts during a training session or game found immediate but short-term changes in markers of brain health. This included reduced cognitive function , lower capacity to control brain blood flow and increases in blood biomarkers indicating neural damage .
These observations suggest that brain function may be temporarily compromised immediately following a single training session or game involving heading. Additionally, football players with a history of heading the ball are found to have reduced brain blood vessel function compared to people with no history of football heading. This suggests that heading the ball reduces brain vascular function, which is thought to be an early indicator of neurodegenerative disease.
But while there are links between heading a football and increased risk of neurodegenerative diseases, actually proving that this skill directly causes dementia or Alzheimer's is difficult.
This is partly because detecting subtle changes in brain function remains challenging . Even with sophisticated imaging techniques, small alterations in brain function may go undetected until it's too late.
Football heading also rarely causes signs and symptoms of concussion (traumatic brain injury), which has also been linked to dementia and Alzheimer's disease . As such, it's unlikely that a few headers during a match or training session will cause visible harm. Yet side-effects may still occur even without causing obvious symptoms.
Over time, these repetitive, "sub-concussive" ball-to-head impacts may cause cumulative damage to the brain. So the more headers that are performed across a person's career, the greater the risk of problems.
In fact, longer professional playing careers and playing in defensive positions (where heading is more frequent) were linked to higher rates of neurodegenerative disease . It therefore seems plausible that the risk of football heading is dose-dependent and accumulates over time.
No safe limit
Like with alcohol consumption, there is probably no amount of heading that would be defined as safe.
This is why the Football Association (FA) has banned heading in grassroots youth football matches for children under the age of 12. The FA also recommends that heading remains a low priority in training for those under 18 - with recommendations that heading is limited in training even after players turn 18. However, some feel this is not enough and are calling for a total ban until the age of 18.
These changes in regulation have been introduced to improve player welfare. However, they are arbitrary. They also don't do much to protect professional players, who might head the ball every practice or match.
While banning heading in football altogether could be viewed as the most effective risk-reduction strategy, heading is an integral component of the game and has been embedded within football for over a century.
This is why more research needs to be done to understand head-impact exposure from a performance perspective as well as a health perspective.
If heading exposure is associated with acute alterations in cognitive, neurovascular or neurological function, this may have implications not only for long-term brain health but also short-term player performance and decision-making. Understanding these relationships could therefore inform both player welfare initiatives and performance optimisation strategies within football.
Another major contributor to the safety of heading is the ball itself. Research shows the ball's material can strongly affect the transfer of energy from the ball to the brain . Working to develop safer playing balls would surely reduce the risk to players' brain health.
Additionally, the use of foam balls or virtual reality in training may provide an opportunity for developing players to improve heading technique without undue risk.
Samuel Francis Leaney receives funding from Alzheimer's Research UK.
Tiago Pecanha receives funding from Alzheimer's Research UK
