I know that messing with national sport is poking a hornet’s nest, but the neuroscience is clear: repeated headers in football progressively destroy neurons in the brain, and a new study points out the mechanisms involved.
Jonathan Cherry’s team, from Boston University, in the USA, had access to cerebral cortex samples from 28 adults between 20 and 51 years of age, donated by their families after their death to two brain banks. Such banks are institutions that increasingly enable studies on the normal and abnormal development and function of the human brain, without which we are limited to comparing ourselves to laboratory animals.
Still, it is laboratory animals that pave the way for human health. Thanks to mice, we know that blows to the head – the light version of the broomsticks with which humans used to kill rodents at home – cause nerve fibers to stretch and immediately disrupt the blood-brain barrier that keeps brain tissue protected from blood, which is both vital and toxic to neurons. Even if they are not serious enough to cause immediate problems such as mental confusion or headache, without which there is no diagnosis of concussion, these changes caused by blows to the head have the potential to leave consequences when repeated without giving the brain a chance to recover.
This is the conclusion of the new study, recently published in the journal Nature, which compared the brains of 11 individuals who had been American football players and had a diagnosis of traumatic encephalopathy, and eight other individuals with no experience in the sport, with the group of interest: nine adults, between 27 and 50 years of age, who had been involved in the sport, but had no neurological diagnosis.
American football does not have a header on the ball, but there are frequent shocks and sudden decelerations of the entire body that cause an impact of the brain against the skull similar to that of headers in our football, as several studies have already shown. The blows to the brain are therefore comparable, and, in the long term, the mental health risks, including the increased likelihood of dementia, are the same between the two sports.
The new study suggests how this happens. The problem probably starts with that mini-rupture of the blood-brain barrier caused by the blow, especially at the bottom of the brain’s grooves, which is more vulnerable for reasons still unknown but probably mechanical, causing inflammation and depriving the neurons there of energy. If the lesions occur one on top of the other, neurons die, and their remains are removed by reactive microglial cells, which are immune system cells resident in the brain.
The more years of football practice, and therefore of exposure to blows of the brain against the skull, the greater the proportion of reactive microglial cells and the fewer neurons scientists found deep in the grooves of the cerebral cortex, even before there were signs of deposition of abnormal peptides that are diagnostic of neurodegenerative disease. Dementia may take time, but the damage to the brain is there, accumulating with each new blow.
What to do with this knowledge is beyond the scope of this column. It’s just up to me to make people think during the next football match.
References
Butler MLMD, Pervaiz N, Breen K, Calderazzo S, Ypsilantis P, Wang Y et al. (2025). Repeated head trauma causes neuron loss and inflammation in young athletes. Nature 647, 228-237.
Tagge CA, Fisher AM, Minaeva OV, Gaudreau-Balderrama A, Moncasster JA, Zhang X-L et al. (2018). Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model. Brain 141, 422-458.
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