Footballers and neurodegenerative diseases
It turns out that if you become a professional footballer, your risk of Alzheimer’s Disease goes up five fold! Unless, that is, you play in goal, which seems to be a bit safer. These are the results from a new study by Glasgow University’s Willie Stewart. He tells Chris Smith how they discovered this, and why it might happen...
Willie - To do this properly, you really need a large core of people to look at. You need a large study population. So we looked at a study population of just over 7000 former professional Scottish football players, and we compared them to people in the community who were as near as we could make them there. So they were born in the same year, they lived in the same postcode areas, but they've never played professional football, and we dug into their health records to see how they were dying.
Chris - And what trends emerged?
Willie - The headline is that people who participate in professional football were more likely to die of neurodegenerative diseases and dementia but three and a half times greater risk. As well as that risk of neurodegenerative disease, we saw the other health measures looked better, so they had less cardiovascular disease, less death through some cancers, and that resulted in a small lengthening of life span, so our footballers were living for about three years longer.
Chris - And it wasn't just because they were living longer that they were succumbing to the dementia. Were they getting the dementia at an earlier age than one would anticipate, or were they at least getting the dementia when other people who are equivalent to them but not footballers were not getting dementia?
Willie - That's a very valid point. That was one of the first questions we asked because here we're seeing our footballers doing better, living longer. So maybe, what we were reflecting was, that older age population where dementias come in. What we could do, because we had a properly set up study with lots of individuals to look at, we factored into the benefits they were getting in cardiac disease and cancer. So we could factor those in, and adjusting for that, they still had three to half times higher risk of death through neurodegenerative diseases.
Chris - And was it right across the spectrum of neurodegenerative diseases? Because that term can embrace a large range pathologies, can't it?
Willie - Exactly. That's the headline, ‘dying of neurodegenerative diseases’. We looked beneath that to people who were dying with them. The way the death certificates are written, they have at the top line the actual direct cause of death, that maybe a heart attack, say, and then beneath that the doctor will also record other diseases and conditions that were there at the end but may not have contributed to death. And that's where things like Alzheimer's disease may appear. Using that, we could look in more detail at individual diseases, and when we did that, what we found is that Alzheimer's disease risk was the highest. Footballers were more likely to die with Alzheimer's disease up to a factor of five times more likely. Then motor neurone disease, which is a rare condition but nevertheless, we saw about four times as often in our former footballers down to Parkinson's disease where there was a doubling of risk.
Chris - Does it matter where on the pitch someone plays? Because arguably in some positions they're going to get exposed to more head injuries than in others.
Willie - Yes. We looked at outfield players against our goalkeepers. Our goalkeepers had less than half the likelihood of getting drugs for dementia.
Chris - I know it wasn't part of the scope of this study, which was very much observing relationships between two different groups of people, but why do you think people who play in these certain positions or play these sports are at these exaggerated risks of getting these sorts of conditions?
Willie - That's the challenge now, to try and identify what it is about the brain injury event that somehow changes the brain. There's a number of things that we're recognizing though, that happen at the instant of injury. For instance, the blood brain barrier can break down at the time of injury and can persist for some time. We see inflammatory changes in the brain that can happen in some of these individuals and can persist for some time. And we also see that the white matter, the fine fiber tracts that run from the brain cells, can become stretched and damaged and broken and that again can persist and evolve over some time. So there's a few candidates that we can work with, but at the moment we don't have the smoking gun, the one thing that we can say ‘this is what happens’ and ‘this is what we're chasing down’.
Chris - Can you say, though, what would be the best way to mitigate this? Is it just to say to people ‘we've got to ban heading of the ball’? Because the Football Association, or representatives of that movement, have said ‘oh well, we're going to have a special monitoring for people who have a concussion or have a head injury on the pitch’. But from what you've been saying, by then the horse has bolted, hasn't it? It's too late, they've already sustained what could be eventually a life changing injury when they're older.
Willie - I think it's important to say that one concussion, one mild brain injury, we haven't got evidence yet would be a risk later in life. So it's still okay to bang your head and not worry too much about dementia. That's important, but it's the cumulative effects. While we may take years to figure out what the pathology is that's driving this, I think there's enough in the evidence from our recent publication and work going back several years to say ‘can we do something to reduce the cumulative small impacts that may not even cause any significant injury that we can detect?’, so ‘can we cut back a bit on things like training for heading during the week? do we need to do as often as we do now? do we need to do as many times in a week as we do now?’. It’s the ways of just making those changes that could be the difference in the long run.