Sudden deaths among athletes make headlines and grab our attention precisely because they’re so rare: when the European Society of Cardiology (ESC) reviewed the relevant research, they found the highest estimate of rates of sudden death in young athletes to be two in 100,000. This January, the New England Journal of Medicine published a study that puts the rate of death among 10 million US runners at 0.54 per 100,000.
Closer to home, the medical director of the London Marathon, Professor Sanjay Sharma, says that the overall death rate for the VLM is one in 80,000. There have been 11 deaths in 32 years of the race – and remember that as Britain’s biggest marathon, London attracts tens of thousands of novice runners of all ages and fitness levels. (It’s difficult to find research that allows for an exact like-for-like comparison, but in 2006, researchers at University College London reported estimated rates of sudden cardiac death among the general population to be one in 1,000.)
Deaths among runners, then, are very rare, but they do occur – and heart problems are by far the most common cause. In athletes under 35, around 90 per cent of sudden deaths are due to underlying genetic heart conditions. Under the stress of training and the adrenaline of racing, these can trigger cardiac arrest, a sudden crisis in which the heart can’t pump oxygenated blood out to the rest of the body. The remaining 10 per cent? This is accounted for by causes including asthma, heat stroke and hyponatraemia (dangerously low levels of sodium).
In over 35s, sudden death is also largely a matter of the heart. But rather than underlying genetic problems, cardiac arrests in older athletes are much more likely to be caused by ischaemic (or degenerative) heart disease.
It's a problem usually caused when arteries are narrowed by plaque, thanks to a range of lifestyle risk factors including poor diet, high blood pressure, obesity and smoking. It also ups your risk of a heart attack, where the heart itself is starved of blood by a clot or other obstruction.
Your risk increases with age, and not just for runners: according to the Office of National Statistics, ischaemic heart disease is the leading cause of death among men in the general population aged 35 plus, and women aged 65 plus.
“And as the marathon distance is most popular among the age groups 35-40 and 40-45, the vast majority of the deaths at VLM have been men with signs of this type of degenerative coronary artery disease,” says Sharma.
Genetics v lifestyle choices
So there’s a pretty stark divide: under 35 and sudden cardiac death is likely to be down to the genes; over 35 and it’s almost exclusively degenerative disease influenced by age or lifestyle choices. While the risks of either event are very low, sudden cardiac death (SCD) among marathon runners is more common in men than women, in older athletes than the under 35s, and in people with risk factors for degenerative heart disease such as high blood pressure, high cholesterol or obesity.
This is why, on April 22, 2012, as Sharma sprinted down Birdcage Walk being cheered on by spectators who mistook him for a racer, he was half expecting to see a 70-year-old man. “To find Claire Squires, an extremely young, athletic female lying there lifeless was a real shock,” he says. “I was horrified.”
A 30-year-old female in good shape, Claire seemed the complete opposite of the type of marathoner most at risk of SCD. The truth is that her death wasn’t just an absolute tragedy. It was also a striking statistical anomaly.
Under 35? Check your genes…
What Claire’s case does highlight is how crucial it is to tread carefully, if, like her, you fall into an at-risk group. Her exact cause of death was still unknown at the time RW went to press, and Sharma says the post-mortem showed her heart to be structurally normal. But she had previously been diagnosed with an arrhythmia, or irregular heartbeat, which would have been a red flag for a doctor examining her before the race.
“Heart flutters, chest pains, disproportionate breathlessness, giddiness or even a blackout while running are ominous signs which need checking,” says Sharma.
You should also get checked if a first-degree relative – a parent, sibling or child – has either died from or been diagnosed with a serious heart condition below the age of 50. This check would include an electrocardiogram (ECG), hopefully the only excuse you’ll ever get to stick electrodes all over your chest.
With only a nine per cent false positive rate, an ECG is a reliable way to pick up on problems including irregular heartbeats and possible abnormalities in the heart muscle itself, such as the thickening of the left ventricular wall associated with hypertrophic cardiomyopathy (HC).
This is important because HC is by far the most common cause of sudden cardiac death in under 35s; the Cardiomyopathy Association charity says that it could affect up to one in 500 people, many of whom never experience any symptoms. It’s closely related to the ‘idiopathic cardiomyopathy’ – that is, thickening of the heart muscle without a single identifiable cause – which recently came back as cause of death in the autopsy of legendary barefoot runner Micah True.
It’s unlikely that you’ll get screened on the NHS unless you’re in an at-risk group or have already had some symptoms. “This is because the data in support of preparticipation screening is mixed,” says Dr Graham Stuart, a consultant cardiologist at Spire Bristol Hospital. “Italian studies suggest it cuts the rate of SCD by 90 per cent but other research has found it to make no difference.”
Without symptoms or a family history, you could get an ECG for a donation of £35 courtesy of the charity Cardiac Risk in the Young, which runs regular screenings for people aged 14-35 across the UK. Check out c-r-y.org.uk/ecg.htm, but be aware that spaces fill up quickly. Your final option is to visit a private clinic. Stuart’s Bristol-based screening service, Sports Cardiology UK, charges £55 for basic tests.
If you do turn out to have a heart condition, your doctor may prescribe drugs such as beta blockers or ACE inhibitors, while an internal defibrillator or a pacemaker may be another potential treatment option. However you manage it, Sharma warns that you need to be wary of performance-enhancing supps.
You should also consult a doctor about how much exercise is safe for you. Under the age of 35, athletes are two and a half times more likely to suffer sudden death than non-athletes – but remember that even this increased rate is still less than two in 100,000. It’s what Sharma calls ‘the paradox of exercise’: in a very small handful of people with underlying genetic conditions, staying active can abruptly end, instead of prolong – and enhance – their lives.
On the next page: Find out why running is one of the best ways to avoid degenerative heart disease.