Heading footballs may cause short-term brain changes
"Heading a football can significantly affect a player's brain function and memory for 24 hours, a study has found," BBC News reports.
The news is based on a small experimental study involving 19 amateur footballers. The players were asked to head a football 20 times. Memory tests and sensitive tests of their brain-muscle pathways were completed before and after the test.
Immediately after heading the ball the tests showed the time taken for communications between the brain and muscles had increased by about five milliseconds. They also scored slightly worse on a memory test. There was no lasting effect on any test by 24 hours and up to two weeks later.
The significance of these findings is hard to judge. None of the players actually suffered from concussion, this was a small sample, and testing of a single session of headers.
Longer term study in a much larger sample of football players is needed to see if these observations have any meaning in terms of the person's long-term health and function.
The benefits of playing regular football as a form of physical activity may outweigh any risks of heading the ball. But seeing that the sport is played by millions of people, further research would seem warranted.
Where did the story come from?
The study was carried out by researchers from University of Stirling, University of Glasgow and Northumbria University and was funded by the National Institute for Health Research (NIHR) Brain Injury Healthcare Technology Cooperative.
The study was published in the peer-reviewed journal EBioMedicine on an open-access basis so is free to read online or download as a PDF (PDF, 1.3Mb).
The UK media's reporting was generally accurate, though there were some minor inaccuracies. Players weren't continuously assessed up to 24 hours as the BBC News report may suggest, and by 24 hours there was no effect. They do though acknowledge that the effect was small but significant.
Both The Guardian and BBC News discuss the death of Jeff Astle, a West Bromwich Albion and England player who died at the age of 59 from early onset dementia. The coroner ruled that this was an "industrial disease" caused by heading footballs.
The English FA has asked FIFA to conduct an investigation into whether previous generations of footballers, who played with a much heavier ball, were exposed to an increased dementia risk.
What kind of research was this?
This was an experimental study that aimed to study the effect of heading a football in the short to medium term in a small sample of young footballers.
The reason for the study was the concern about the effects of sports impacts that can cause concussion, or just short of concussion or minor head injury.
Football regularly involves heading the ball, but there has been little study around the effects. This research aimed to look at this using sensitive brain imaging.
What did the research involve?
The study involved 19 amateur football players (five female), average age 22 years. The researchers excluded those with history of concussion in the past year, any head injury that had resulted in loss of consciousness, or those needing to take medication.
After 24 hours free of physical activity they took part in the football-heading test. This was where a standard football was projected at 39kph from a device positioned six metres from the player.
They were asked to perform a rotational header (a header where the direction of the ball is changed, like a goal attempt from a corner kick) on each ball.
Each player received 20 consecutive impacts in 10 minutes which is said to replicate normal heading practice. Rotational headers were used as they are often performed in training drills and corner kicks during matches and are believed to cause more injury than a linear header (where a ball is directly headed forwards or backwards).
After the practice the players had transcranial magnetic stimulation (TMS) applied to their scalp. TMS is said to be able to assess signs of concussion, and indicates how well the brain nerve pathways are communicating with the muscles in the body. It specifically looks at signals from the primary motor cortex (which helps control physical movement) and specific muscles.
Players were then asked to repeatedly extend their knee. They had electromyographic recordings (recordings of the electrical activity of the muscles) taken of the quadriceps muscles to look at nerve signals coming from the brain to the muscles.
Other outcomes included giving players a cognitive test to look at reaction time, attention, learning and memory. They also looked at their postural control.
All tests were carried out immediately after heading, at 24 hours, 48 hours and two weeks. Measures were compared with the person's recordings before heading.
What were the basic results?
Generally, heading caused a slight delay in nerve signals reaching the leg muscles from the brain – known as muscle silence. This is said to indicate corticomotor inhibition, a possible indicator for sub-concussion.
Immediately after the headers the period of silence was 123 milliseconds (ms) compared to 117ms before the headers. This was statistically assessed to be a small effect.
Immediately after the headers players also had slightly poorer spatial memory on the cognitive tests. This was again interpreted as a small effect on short term memory. There was also a 67% increase in error on the Paired Associated Learning task which is said to correlate with a medium effect on longer term memory.
There was no effect on any of the tests at the later 24 hour, 48 hour or two week assessments.
How did the researchers interpret the results?
The researchers conclude: "Sub-concussive head impacts routine in soccer heading are associated with immediate, measurable electrophysiological and cognitive impairments. Although these changes in brain function were transient, these effects may signal direct consequences of routine soccer heading on (long-term) brain health which requires further study."
Conclusion
The researchers' conclusions to their study are quite appropriate.
Firstly, these were routine headers that did not cause concussion. It is important to distinguish this from head injury and traumatic brain injury. The participants did not lose consciousness and no other signs or symptoms of head injury – such as headache, dizziness, sickness or vomiting – are reported.
The headers caused some immediate changes to the brain-muscle pathway and to memory which could be measured – but these effects were small to moderate in size, and only very transient. There was no lasting effect at any later follow-up time. The researchers say that TMS could possibly be used to detect acute changes in brain function following head impacts that don't cause concussion. However, as the researchers conclude, whether or not these minor observed changes could have any implications for brain health is completely unknown.
This research was carried out in a small sample of young, amateur footballers who faced a device used to mimic a shot taken from a corner. The device was also set to a specific speed. Though this was intended to replicate routine header practice, it's hard to know how well it will represent all the real life differences between players and shots on the pitch.
Research is ideally needed in a much larger sample of football players – or people from other sports carrying risk of head impacts – that follows them up in the much longer term to see if these observations have any meaning in terms of the person's long-term health and function.
This does not take away from the fact that any sports involving physical contact of any form can carry a small but real risk of serious consequences if the person does have serious head injury.
But the risks of not exercising enough, or at all, are much higher and are well documented. Team sports such as football can also improve a child's self-esteem and ability to work with others, as well as their fitness.
As football is played by millions of people every week at a grassroots level, further investigation into any potential harms associated with heading the ball would seem prudent.
