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October 23, 2019   4 mins

Footballers are more likely to die of neurodegenerative diseases like Alzheimer’s: that is the conclusion of a widely reported study just out, looking at former Scottish professionals and comparing them to the public at large. The report has already led to calls for major changes to the game, and in particular banning the use of headers. Several high-profile cases of dementia among former pros — most notably the great West Brom forward Jeff Astle, who died at just 59 — have raised the issue in the public consciousness as well.

But is banning anything a good idea? It’s worth looking at the numbers a bit. The links between head injuries and dementia among professional sportspeople are in the news quite a lot, but I think the risks and the certainty of the science are sometimes overstated, and it could put people off playing sports, which is unambiguously good for you on the whole.

The comment piece I just linked to points out that professional footballers were at a 350% increased risk of death from neurodegenerative disorders, Alzheimer’s being the main one. And that is absolutely true.

However, as I’ve said on one or two occasions, learning about the increase in relative risk is no use for helping you make decisions. If your risk of something goes up from one in a billion to 4.5 in a billion, that’s a 350% increase, but you might not care about it very much.

In this case, the “absolute risk” of neurodegenerative disease among the control population was 0.5%; among the Scottish footballers it was 1.7%. That is indeed a 345% increase, but in real terms, it means that if you’re a Scottish professional footballer, there’s a 1.2% chance that you’d die of a neurodegenerative disorder that you wouldn’t otherwise have died from.

That is not a negligible or irrelevant thing — a one-in-80-or-so chance of getting a horrible disease like Alzheimer’s is worth being aware of. But it’s much less scary-sounding than “a 350% increase”.

Also, we should note that these players mainly played a long time ago, in football terms. Their median age was about 65, suggesting that they would have retired at least 30 years ago, and in many cases much earlier. The rules of football have changed significantly in that time; balls have become lighter; the pitches have become smoother and more amenable to passing along the floor; and I think it’s fair to say that the influence of Wing Commander Charles Reep has waned, and players are less likely to lump it to the big man up front these days. It’s far from obvious that the risks of heading are the same as they once were.

That’s assuming that heading is indeed the cause of the problem, of course. The working theory is that repeated mild trauma causes something called “chronic traumatic encephalopathy”, a sort of steady tearing of small structures in the brain, and that leads to dementia. But it’s very hard to establish; there is still some dispute over whether the condition is real, although I think less so now than when I wrote that piece in 2016.

It was first noticed in American football players, but there was a selection problem, in that the only brains they dissected were those of players who’d shown symptoms of neurodegenerative disease, making it impossible to see whether the background rate was higher than you’d expect.

It could well be that these repeated minor traumas cause CTE, which then leads to dementia; but it’s not as though there are no other possibilities. The new study tried to control for one obvious factor, the socioeconomic status of the footballers — neurodegenerative disease, like so many other illnesses, is linked to poverty — but they don’t seem to have controlled for other things, such as alcohol use.

It would not be surprising to learn that footballers drink more than the average person. Alan Carson, a professor of neuropsychiatry at the University of Edinburgh who’s worked extensively on the links between head injury and dementia, told me that quite a lot of the ex-pros went on to become publicans, for instance, which was a common career move.

Of course, you could say that even though we can’t be sure, there’s still no need to be reckless — the precautionary thing to do would be to ban heading in football.

I would be sceptical of that, though. For one thing, heading is a beautiful part of the beautiful game and it would be poorer without it. There are already very sensible precautions against concussion, including the change in the ball itself. More importantly, though, if we make a big deal of it, then I worry it will scare people off playing sport outside the professional game — and that would be a catastrophe.

Something that hasn’t been hugely reported in coverage of the study is that, in general, the footballers were healthier than the control population. They were less likely to die of heart disease or lung cancer, and in fact were less likely to die of all causes below the age of 70 (their mortality rate over the age of 70 was higher). Playing football appears to be protective. And that’s exactly what you’d expect, because sport is unambiguously good for you.

Carson says that the study — led by William Stewart of the University of Glasgow — is well-executed and thoroughly interesting, and that it contains hints that do suggest a causal link with heading the ball: one point is that goalkeepers, who presumably head the ball less, were slightly less likely to die of dementia. “This is by far the best available data, and the team should be congratulated,” he says. But he adds that Stewart’s previous work suggests that CTE might not be the cause, and that the whole pathology is more complicated than that.

I don’t think anyone would suggest that we stop taking concussion or head injury in sport seriously. But it’s important to note that this data comes from professional sportspeople, playing in a less cautious era with heavier balls and different tactics, and even in that situation the overall effect of playing seems to have been to keep them healthier — and we can’t really be sure that headers are the problem anyway.

My worry is that the vague idea that Football Causes Head Injuries Which Cause Dementia will filter its way into the public consciousness, but there is absolutely no reason to think that this has any impact on amateur players, while there is loads and loads of evidence that sport keeps you fit. Exercise is good for your cardiovascular system, so it protects you against dementia specifically. If you want to avoid getting Alzheimer’s, it’s almost certainly better to play football than not.

Tom Chivers is a science writer. His second book, How to Read Numbers, is out now.