Depending on position, soccer players can head the ball 500-1,500 times per year. This can mean thousands of headers over several years for many players.
So how does the brain typically react to 20 headers in a couple of hours – a typical soccer match for many players? (These 20 head impacts can also happen in a much shorter time during drills.)
Memory Performance Can Drop by 50% After Multiple Headers
An experiment conducted by the University of Stirling in Scotland sought to look at the short term effects of multiple headers on brain function.
Study participants (all soccer players) were asked to head a ball 20 times, fired from a ball machine to simulate the pace and power of a corner kick. Before and after the heading sessions, the players were tested on a number of memory performance tests.
The study results found that football heading resulted in immediate and measurable changes in brain function, including a 41% to 67% reduction in memory test performance.
The (somewhat) good news is that these changes in brain function were transient, with effects normalizing within 24 hours. The bad news is that the science isn’t very clear on the cumulative long term effects of hundreds, or thousands of headers.
Growing Awareness of “Minor” Head Impacts from Sports
In a 2013 study conducted at Albert Einstein School of Medicine, 37 amateur adult soccer players (average 22 years of amateur soccer play) underwent an advanced MRI-based imaging called diffusion tensor imaging, known as DTI.
DTI “sees” the movement of water molecules within and along axons, the nerve fibers that constitute the brain’s white matter. Disrupted movement of water molecules along axons indicates white matter damage. White matter in the brain functions as the connectors between neurons and between different brain networks.
The Einstein School study results showed that soccer players who headed the ball at a threshold above 885 times a year had significantly reduced white matter integrity in several brain regions. This study provides compelling preliminary evidence that brain changes resembling mild traumatic brain injury are associated with frequently heading a soccer ball over many years, and can manifest itself in a number of concussion symptoms.
What is also becoming clear is that youth sports teams need to take proactive steps to protect the brains of younger players — between the ages of 6 and 18, the human brain undergoes massive reorganization and growth, and is especially vulnerable to concussions.