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Sunday, June 21, 2009

Cardiac events during sport on TV

The dangers of WATCHING elite sport - health checks needed!

If you're reading this (or are a regular reader), then you're probably also inclined to spend fairly large periods of time actually watching sport (and wondering where we've been lately, but that's another story).

Being sports fans, you probably make it a point to follow coverage of your teams whenever possible, and live and share in the emotions of the game. People follow sport differently, of course - some dress up in the playing kit, scream at television sets and referees, and feel more anxiety and stress than the players they are supporting. Others (and I'm in this group) tend to be more dispassionate and 'cool', watching with a more analytical eye.

Uncertainty and enjoyment

Regardless, the enjoyment comes largely from the uncertainty. In marketing terms, sport on television is classified as an "instantly perishable product", which is to say that the value of sport perishes instantly once the outcome is known. Few will watch a game with emotion and enjoyment if the result is known, though of course, there are other reasons to watch matches over and over (game analysis, for example).

But what if that uncertainty is also the cause of medical problems? I have no doubt that those of you who fall into the first group - the screamers who live and breathe every moment - have been told to calm down or you'll damage your health.

Well, it turns out that this may be true! A study published in 2008 in the New England Journal of Medicine (very prestigious) looked at the incidence of cardiac events in Germany during the 2006 Football World Cup, and found that spectators are almost four times more likely to suffer cardiac events when their team played, and particularly, when they played very close, high-stakes matches.

The reason this is topical, of course, is that my country, South Africa, is gearing up for the 2010 FIFA World Cup, and is currently hosting the Confederations Cup (though I must say, when we play, the uncertainty in the outcome is perhaps not as great...!). We're also hosting the British and Irish Lions rugby team (a team picked every 4 years from the best of England, Scotland, Ireland and Wales). Yesterday was the first test, and it probably gave a few people cause for some cardiac events....!

The study - a spike during matches

The study was done from Munich, during the World Cup in Germany, and it tracked the number of cardiac events reported during German matches, during the World Cup when Germany did not play, and during a control period that was made up of about 4 months in the years before and after the 2006 World Cup.

The graph below shows the spikes that occurred when Germany played, indicated by numbers on the red line. The blue and yellow lines represent the control periods of 2003 and 2005.

In particular, games 5 and 6 are the ones of interest - those were knock-out matches where Germany first defeated Argentina in a penalty shoot-out (Game 5 - huge tension for fans), and when Germany were defeated by Italy in the semi-final (Game 6). More than 60 cardiac events per day were reported, compared to the average of about 15 per day! (Match 2, by the way, was a group game between Germany and Poland - the stakes in that game are high because it's something of a local derby, with some animosity between the teams)

Once losing that semi-final, Germany played Portugal in the 3rd-4th play-off, and you'll see how there was no spike, which confirms that the 3rd-4th play-off lacks any tension or interest! The final (not involving Germany) produced more cardiac events than this game.

This was of course the final where Zidane infamously head-butted Italy's Marco Materazzi - this was an event that probably produced its fair share of cardiac events back in France...!

Breaking the numbers down a little further, the graph below shows the number of cardiac events reported during the three stages, separated into men and women's totals. The average number of cardiac events during German matches was 43 per day, compared to only 14.6 per day during the control period (and 18.2 during the World Cup when Germany did not play - the die-hard football fans, perhaps).
Differences between men and women

Perhaps not surprisingly, the increase in cardiac events is much greater in men than in women, with an almost four-fold increase in the number of events for men during German matches, compared to a two-fold increase for women.

This is further shown by the graph below, which shows the calculated incidence ratio of cardiac events for men (in blue) and women (in magenta) during German matches, during the World Cup when Germany does NOT play, and during the control period.

Just to explain, the incidence ratio is worked out on the basis that the chance of a cardiac event during the control period is equal to 1. For example, if there were 20 cardiac events a day during the control period, and 40 during matches, then the incidence ratio would be equal to 2 - effectively, you are twice as likely to have a cardiac event during a match. In this particular study, the calculation is complicated a little by the fact that the researchers adjusted the incidence for environmental factors such as barometric pressure (which is why you won't quite get the same values as these if you do the calculation yourself).

So the graph above shows that men are 3.26 times more likely to have a cardiac event during a German match than on another day, whereas women are only 1.82 times more likely. My first reaction is that this is pretty easy to explain - men tend to follow the game more and experience the stresses that would trigger heart attacks more than women (a generalization, certainly). However, there are a couple of other possibilities - one is that men have pathophysiological differences that make them more vulnerable to heart attack, or that they are more vulnerable to emotional triggers. I'd still suggest that TV viewership stats will reflect that men are perhaps 4 times more likely to be watching the game than women, which would explain the finding almost entirely.

The point is - preventative measures needed

So the point of all this is not simply to tell a story about an interesting scientific observation. It has some very serious implications. The spike caused by live sport (and there is no reason to think this is unique to soccer, though of course a World Cup is likely to produce the greatest spikes) is significant, and something needs to be done, quite literally, to save lives.

The authors suggested options such as taking or changing the dose of beta-blockers (drugs that block the stress response and potentially protect the heart), drugs including anti-inflammatories, anti-platelet drugs like aspirin, and behavioral therapy to counsel fans on how to cope with stress. One observation that is significant is that almost 50% of those who had cardiac events were diagnosed as having coronary artery disease BEFORE the heart attack, and so simply pre-screening will identify people most at risk, and they can then be counselled or treated to further reduce the risk.

So without wishing to throw a wet blanket on your baseball/rugby/soccer/cricket watching activities, try to reign in the stress - it might be life-saving. And it's just sport, after all!



Lucio said...

Nice post!
I would like to know what can trigger a cardiac event when you watch your team playing.
Is it too much adrenalin?

Ross Tucker and Jonathan Dugas said...

Hi Lucio

Thanks for the comment!

Yes, that's certainly part of it. The study actually went into quite a bit of detail, but I didn't want to make the post any longer (it was already long!) so I didn't go into detail!

Part of it that most of the cases were in people who already had coronary artery disease. What this means is that they have plaques that partially obstruct blood flow in the coronary arteries.

Under stress, when the heart is stimulated by the sympathetic nervous system, a combination of events happens that can cause these plaques to become dislodged, and then they can completely block the vessels. Heart rate rises, BP increases, the vessels constrict, and this can all lead to a sudden block in blood flow. What I didn't post was that this kind of problem, called a myocardial infarction, accounted for many of the cases.

So when the heart rate rises, and the blood vessels constrict, the risk rises. This is all mediated by adrenaline, so you're 100% right, adrenaline is the "messenger" that causes the problems down the line. There are a couple of other hormones (the stress hormones), but that's about the gist of it!


SportsBiz said...

So, if I understand you correctly, the study is not saying that watching sports by itself with trigger a cardiac episode without there being a hospitable environment for one to occur. By that I mean, there needs to be prior coronary artery blockage already present in the individual that is further complicated by the excitability triggered during the match being watched. No existing blockage; no cardiac episode during sporting event.

Of course, absent a prior trip to the cardiologist, few of us are aware of existing artery blockage to take the proper precautions.

Ross Tucker and Jonathan Dugas said...

HI Sportsbiz

Not necessarily. In the study, a large proportion of the cases had previously been diagnosed as having coronary artery disease, but not all.

That might mean that some of the cases had a blockage that had not been diagnosed (highly probable), and others may have had no existing coronary artery disease, but had another condition that might have predisposed them to a heart attack.

"unexplained" cardiovascular deaths do occur, often because of some underlying genetic problems, which can often not even be detected in tests.

But in general, what you say is correct - it's possible to predict who is at greatest risk based on that kind of pre-screening, which is what the authors pointed out in the study. So most (but not all), will have some existing disease, and that is why testing is important!