Welcome to the Science of Sport, where we bring you the second, third, and fourth level of analysis you will not find anywhere else.

Be it doping in sport, hot topics like Caster Semenya or Oscar Pistorius, or the dehydration myth, we try to translate the science behind sports and sports performance.

Consider a donation if you like what you see here!

Did you know?
We published The Runner's Body in May 2009. With an average 4.4/5 stars on Amazon.com, it has been receiving positive reviews from runners and non-runners alike.

Available for the Kindle and also in the traditional paper back. It will make a great gift for the runners you know, and helps support our work here on The Science of Sport.

Monday, November 05, 2007

Sudden death during exercise - What does it mean for YOU?

Over the last few days, the world of sport and running in particular have been dominated by the New York Marathon, and the untimely and sad death of Ryan Shay, an elite marathon runner from the USA, during his country's Olympic Trials. Whenever a healthy and fit athlete dies during competition, we sit up and take notice, and the spotlight is turned away from the likes of Paula Radcliffe and Martin Lel, placed instead on the unanswerable questions of why people should die doing an activity that is supposed to be healthy?

And of course, it affects every one of us, and at The Science of Sport, as we've tried to bring you insights on these events this year, we've received questions and come across numerous discussion threads from people wondering just what to do with the knowledge that it seems anyone can be affected.

A bad year for perceptions of exercise

And let's face it - it's been a bad year. The Science of Sport was "born" in April, and already this year, we've seen:

So it's been a bad year, and this does not count a few other, "lower profile" cases that we haven't delved into in great detail. But what do we make of this? And how should we respond? A few of our readers have asked this question, many have even been diagnosed with some of the conditions that have been implicated in some of these deaths, and understandably, there's a great deal of anxiety over just how safe exercise is, given that these healthy, fit individuals collapse and die during exercise?

The first and most important point - if you exercise, you're better off

Perhaps at the outset, we must emphasize this vital point - people who exercise and are fitter are LESS likely to suffer from cardiovascular disease and die suddenly than people who do not. In otherwords, put simply, if you took a random sample of say 1000 people, those who are fit and who exercise stand a better chance of being healthy than those who do not. Unfortunately, when athletes collapse and die, it tends to be a highly public event, and gains a disproportionate level of media attention. In these individuals, there is almost always some underlying pathology, and it is the actual act of doing exercise that places the stress on the system to cause the problem. That is, they are more likely to experience a heart attack or cardiac arrest during exercise, but their overall chances of this happening are still lower than for the inactive population.

Therefore, we cannot over emphasize this truth - regular exercise protects the heart. It increases your HDL (good cholesterol), improves cardiac function, and increases life expectancy and quality of life. Therefore, the benefits of regular exercise deserve to be acknowledged, or at the very least, held up in the debate - exercise is not dangerous, it's highly beneficial and that should never be forgotten.

Sudden cardiac death - a rare event

Now, we cannot deny, in the light of the last few months' events, that sudden death is a problem during exercise. As we mentioned in our post on the weekend, the largest available studies have estimated that the incidence of Sudden Cardiac Death (SCD, for short) lies somewhere between 1 per 200 000 and 1 per 1 000 000 athletes per year.

Looking at the primary causes, the first 'crude' distinction can be made between athletes younger than 35 and those older than 35.

Older athletes - Coronary Artery Disease

In older athletes, the primary cause of SCD is coronary artery disease. This is what caused the death of running legend Jim Fixx in 1984, and is also responsible for Salazar's collapse (read more about this condition here). It has been found to be the cause of SCD in older athletes in anything between 70% and 90% of the cases, with an estmiated incidence of 1 in 16000 runners per year. If you think about that last statistic for a second, it means that out of every 16 000 runners, 1 is likely to experience a heart attack brought on by this condition each year. If that seems high, remember the very important point that these people are still at lower risk than they would be as a result of being inactive. In fact, the correct use of exercise is a recommended form of treatment for people who have CAD, and so rather than avoid exercise, these people should embrace it as a means to overcome the problem! Obviously, it does require sensible exercise and should be supervised or cleared by a physician first.

Younger athletes - a multitude of possibilities

In younger athletes, the possibilities are slighty more numerous and include Hypertrophic Cardiomyopathy and Coronary Artery abnormalities, which we described in more detail in a previous post. So we won't go into them in too much detail here, but rather focus on what you can do to minimize risk as one of those athletes who may be diagnosed with any of these conditions.

So what do YOU do if you think you're at risk, or are concerned about SCD during exercise?

First point - education. It's vital that you educate yourself and learn about the symptoms and signs of the condition. As we emphasized, in 21% of the reported cases of HCM, there were indications of a problem before the event. Things like fainting, shortness of breath, chest pains, dizziness, all reported retrospectively by family and friends. Similarly, in 30% of cases of Coronary Artery abnormalities, symptoms were present, but ignored.

So it is vital that you understand and recognize the symptoms. All too often, the first clinical manifestation of an underlying condition is death - this is not because it happens as a bolt from the blue - it was there, but went unrecognized. So rule number one - empower yourself through knowledge.

Second point - testing and screening. OK, things get a little bit hazy here, because:
  • Often, these conditions are difficult to detect, and;
  • Once detected, there's no guarantee that they will be clinically significant or limit exercise in any way.
In fact, it's been shown that there is generally an unfavourable cost-benefit ratio to doing this kind of mass, specialised testing, though understandably, every individual would not consider this relevant if it meant saving ONE life (Economics is great in that it reduces the whole down to one ratio and then decides its not beneficial!) But the point is, it's hit-and-miss as to whether you can adequately detect a condition AND predict its clinical outcome. On top of this, the incidence of death is SO SMALL, it actually doesn't pay to worry excessively about trying to pick up.

One condition that jumps to mind is Wolff-Parkinson-White syndrome - it happens in about 0.15% of the population, and the risk of sudden death, even in this small group, is only 0.1%! So once you've detected it, what do you do with that information? Do you tell an athlete to avoid exercise because there's a 0.1% chance of SCD? Because remember, by denying the athlete exercise, he INCREASES his risk of disease and death in all other areas...

Example of Mitral valve prolapse - education and knowledge are the key

Take the example of Mitral valve prolapse. It is a condition that has been found to occur in 2% of the population (some studies say it's as high as 5%). Therefore, in a field of 35000 runners in Chicago and 40000 runners in New York, there could be about 1500 runners with the condition (assuming they're unique and that they are representative of the population - big assumptions, I realise, but it's to make a point!).

Add to that the 15 000 other runners who don't do the marathon but stick to three or four weekly 5 mile jogs, and suddenly you see that a vast number of people are exercising with the condition. Yet only one death happened - that of Chad Schieber, and that's not even conclusively proven as due to the condition. So what you have is a condition that CAN increase your risk of SCD during exercise, but the risk is so small, and if you combine this with a screening procedure, and knowledge of the symptoms, then you are pretty much empowered to control that risk.

Obviously the severity or the degree to which the condition affects the function of the heart varies, but that's picked up in the symptoms and screenings - the degree of mitral valve regurgitation, for example, is important. But it does emphasize the point - empower yourself through knowledge, and test yourself through medical science, and you can control the risk as much as possible.

If you do this, and pay close attention to your symptoms, then as we've said, you do everything possible. Of course, we can never provide a guarantee that you'll be OK and nothing could happen - no doctor could even provide that, and we are not cardiologists! So we don't wish to propogate the myth that a few tests and some knowledge is all it takes. But what we are saying is that regular monitoring, awareness, and knowledge will go a long way to ensuring that you exercise safely. And ultimately, that's all you can do. That, and exercise with the knowledge that your training is lowering your risk in every area compared to those people who are not training. But remember, be safe rather than sorry, and make sure!

Ross & Jonathan


Shop Fitness said...

I have been close to individuals who have literally died during exercise. I appreciate this article, thank you.

Ross Tucker and Jonathan Dugas said...

Hi Shop Fitness, and thanks for visiting us here at The Science of Sport.

We are sorry to hear that you have known people who havedied during exercise, but at the same time we are really pleased that you could get something from this post. We really hope it helps you understand better the sudden death and exercise issue.

Kind Regards,

Alex Battisti said...

people who exercise and are fitter are LESS likely to suffer from cardiovascular disease and die suddenly than people who do not.

Exercise and 'being fit' is not equal to long distance running, where AFAIK most (relative to the number of participants) incidents of sudden death are reported. Meaning that it is not possible to infer from weightlifters and volleyballers and sprinters and wrestlers and gymnasts and runners and 'everybody else' on average being less likely to suffer from cardiovascular disease, that long distance running gives you a better 'overall health lookout'.

the incidence of Sudden Cardiac Death (SCD, for short) lies somewhere between 1 per 200 000 and 1 per 1 000 000 athletes per year.

If you're referring to the "Lausanne Recommendations" (PMID: 17143117) you should mention, that: "the incidence [of SCD] is higher in athletes (approximately 2/100,000 per year) than in non-athletes (2.5 : 1)" and that: "SCD was reported in almost all sports; most frequently involved were soccer (30%), basketball (25%) and running (15%)". Considering that there are probably (significantly) more soccer and basketball athletes (under the age of 35) than there are runners, it is a bit of a stretch (at least form this data) to say that the benefits of long distance running outweigh it's risk. Just to clear, I am not saying it does not, just that you can't conclude anything (in favor of running) from this data.

For competitive long distance running there is also the: "Sudden death during mass running events in Switzerland 1978-1987" study (PMID: 2655076). Which shows that: "The Swiss incidence of sudden cardiac death during organized mass runs was 50 to 1000 times higher than the incidence expected by chance alone (as estimated from national death register data)" and "This study confirms that there is probably a clearly increased risk of sudden death during running events with a competitive character, but this acute elevation of risk should probably not be overstated in view of both its very low population..."

So I would think you should (more) clearly differentiate between the risks of 'exercise in general' and competitive long distance running. As I can see it, the former has good favorable evidence, while the latter, well, is at least 'undecided', but (IMHO) probably more on the risky side of life.

Yours sincerely,
Alex Battisti

p.s. sorry english is not my primary language