By David Shaw
On the 16th of January it was reported that the Scottish Football Association is to ban children under the age of 12 from heading the ball at football training. The change is due to the results of a study published in 2019, which showed that death rates from neurodegenerative disease including dementia are higher among former professional footballers. The ban has met with widespread approval and support, and it may be prudent to use this measure to protect the future health of children playing football. However, the risks in this case have been widely misreported, the data used to generate the results are quite old, and the ban is unlikely to protect those it seeks to help.
First, the media reporting of the risks has been highly misleading. The Guardian stated “there was a five-fold increase in the risk of Alzheimer’s, a four-fold increase in motor neurone disease and a two-fold increase in Parkinson’s.” The BBC claimed that “former players are three-and-a-half times more likely to die of dementia.” But these are relative risks, and responsible science journalism must report absolute or baseline risks. To take one example, the study found that “Mortality with neurodegenerative disease listed as the primary cause was 1.7% among former soccer players and 0.5% among controls.” This means that 99.5% of the controls did not die of a neurodegenerative disease, versus 98.3% of former soccer players. So the absolute risk increase among men who played football professionally for decades is in fact 1.2%, not the 350% reported by the BBC. This poor reporting does a disservice to the public debate on this important issue. (Note also that these are the statistics before adjusting for footballers’ reduced risk of dying from cardiovascular disease, meaning that the increase in risk is actually even less; footballers are more likely to die because of neurodegenerative disease because their greater physical fitness means they are less likely to die of another cause earlier in life.)
Second, the data used in the study concern men who were born between 1900 and 1977. Many of these men played professionally and trained as children when footballs were substantially heavier than the modern ball, which could both explain the increased risk found in the study and suggest that today’s modern balls may not have the same effect. Daniel Mackay, the study’s lead author, claimed on Radio Scotland that there is no reason to think that differences in ball weight and size might weaken the study’s conclusions, stating “It [the old ball theory] sounds like a good idea but really until there’s data we need to act with caution”. This is somewhat ironic, as there are not yet sufficient data for banning heading either, and further research is indeed needed on both hypotheses.
Finally, even if the data are sound, banning children from heading the ball may not actually have the intended effect. Most children never become professional footballers (less than 0.5%, with only 0.012% making it to the English Premier League), and most professional footballers (almost 99%) do not die because of a neurodegenerative disease. It is possible that the slight increase in risk of death from such disease is primarily caused by repeatedly heading the ball as an adult professional player, rather than at training as a child. Indeed, if heading the ball as a child was the problem, we would expect men who never became professional footballers to have a similar risk of death from this cause as those who did become professional footballers. The study did not show that. While professional footballers are perhaps more likely to have spent longer training as a child than young footballers who did not become professional players, there is no evidence to suggest that heading the ball as children has any causal link with the increase in risk of neurodegenerative disease.
Ultimately, less than 2% of professional footballers died of neurodegenerative disease, versus less than 1% of the general population. Most footballers do not die because of such disease, and this study did not show that footballers are more likely to get dementia or that they got it because they headed the ball as children. These key facts are entirely absent from the media coverage and the public debate. It may reassure the public if children are banned from heading the ball, but it seems highly likely that this shot will miss the goal.
Author: David Shaw
Affiliation: Care and Public Health Research Institute, Maastricht University and Institute for Biomedical Ethics, University of Basel.
Competing interests: the author’s elder son is 9, plays centre mid for Cambuslang Red Star 2010s, and isn’t keen on the ban.