By Lauren F Friedman

If it seems like your heart is pounding especially loudly as you tensely watch your team move up and down the soccer field, it’s probably not your imagination.

A 2008 study in the New England Journal of Medicine concluded that “viewing a stressful soccer match more than doubles the risk of an acute cardiovascular event.”

We first saw this research reported by Vox. And while the rather stunning chart below makes the researchers’ frightening conclusion look perfectly clear, it turns out that there’s actually a surprisingly thick stack of studies investigating this very question.

It turns out the real story about soccer stress and heart attacks is much more complex.

What Does It Really Mean?

Here’s a look at the chart from that NEJM paper, which shows heart attacks (and related problems, like irregular heartbeats) among the 4,279 German patients in the study. You can see that during six of Germany’s seven World Cup matches in 2006 (red line), many more heart problems were reported than at the same time in previous years:

The study’s conclusions are not as airtight as they seem from this graph.

The first point we need to make when looking at this scary-seeming data: If your risk of having a heart attack is already very small, your risk will still be very small even after you double it. That being said, this finding of increased risk is something to keep in mind for those who do have heart disease, who are already at high risk.

The rise was sharpest among men and among those with existing heart disease, and the real danger period seemed to be in the two-hour period right after the start of the game:

Even if the perceived connection between the World Cup and heart attack incidence holds up, the researchers note, importantly, that it’s impossible to say whether the stress of the games or other associated activities — things like lack of sleep, excess drinking, forgetting to take medication — are the real trigger.

A Controversial Link

In some ways, the findings are not surprising. It’s already known, the NEJM researchers note, that “events that induce environmental stress in a large number of people in defined areas — such as earthquakes, war, and sporting events — may increase the risk of cardiovascular events.”

That said, they continue, “reports of the association between soccer matches and rates of illness or death from cardiac causes have been controversial.”

While a number of previous studies support the NEJM findings, there are other researchers who have come to the opposite conclusion, suggesting that in spite of one admittedly striking chart, this is not a settled question.

One earlier study found a similar result among Dutch men (but not women), during soccer matches involving their national team. The findings of another study, on local teams within the U.K., agreed. And a third study, a large analysis of hospital admission in the U.K., found an alarming spike “on the day England was eliminated from the 1998 World Cup by Argentina in a penalty shoot-out and on the two subsequent days.”

Those researchers concluded that while an ordinary soccer game might not be dangerous, a heart attack “can be triggered by emotional upset, such as watching your football team lose an important match.”

But it might be too soon to conclude that getting excited about the World Cup is a real risk.

First of all, when French researchers re-analyzed the Dutch study on this heart attack-soccer link, they found no evidence of that link among the French. (It’s worth noting, though, that they were looking in particular at a match where the Dutch team was eliminated by the French team — probably more stressful for the Dutch.)

Another French study pointed out that the question of whether watching sporting events increases the risk of a heart attack is actually more nuanced than previous research has shown. “On one hand the emotional and mental stress, and alcohol and tobacco consumption, could increase [heart attack] mortality,” the authors write. “But on the other hand the immense fervor and the collective euphoria observed at the time of a victory could decrease this mortality.”

Indeed, in the NEJM study, one Seattle doctor noted in a response, “the two highest peaks in cardiac events occurred during the days of the two most emotionally wrenching matches.”

Especially damning, however, was an analysis by a second team of Dutch researchers, who found that after looking at a larger set of games from an earlier time period, the supposed spike in heart attacks during games basically vanished.

“That our analysis using the same methodology failed to show increased mortality after five major matches suggests that the original finding may have been a chance finding, or that the 1996 game against France featured peculiarities that were not shared by the games we analyzed,” they concluded.

What Now?

Studies following up on the NEJM study that produced the chart above have also come to a wide variety of different conclusions. That study, in fact, has been cited almost 200 times since 2008, suggesting that World Cup researchers have as many opinions as World Cup fans.

At least of a few studies of the very same events — the 2006 German World Cup matches — did not support the original findings at all.

A 2010 study (title: “It is just a game”) pointed to the German study as an outlier, noting that among 10 studies on the topic, most found a relative risk on game days of 0.7 to 1.3, which are close to meaningless. “The cardiovascular effects of watching football matches are likely to be, if anything, very small,” the researchers wrote.

The authors of another study that year (title: “It is not just a game”) disagreed, calling sporting events “predictable triggers of cardiovascular events… more likely to affect passionate fans and patients with known cardiac disease” — especially when the games are high-stakes, or the home team loses.

Earlier this year, a study that looked at the German national team’s matches from 1995 to 2009 again called the 2008 study into question. Their conclusion? “There is no relevant increase or decrease in mortality on match days of the German national soccer team.”

Blowback

Given how controversial this line of research is, it’s no surprise that the NEJM study prompted a number of spirited letters right after its publication.

One Italian doctor pointed out that “increased intake of saturated fat from typical Central European foods such as french fried potatoes, beef fat, pork, lard, and cheeses, are commonplace among people who are watching sports on television.” Those foods, he notes, can trigger acute heart symptoms, especially when paired with things like stress and smoking.

A University of Michigan doctor offered another perspective, arguing that the conclusion of the NEJM researchers “is weakened considerably” because they didn’t analyze the data in the weeks and months after the matches, which might have revealed that the heart attacks during the World Cup were events that were about to happen very soon anyway.

His reasonable argument exposes just how futile, and ultimately depressing, this line of inquiry may be. “Although the stress of World Cup soccer may precipitate a cardiac event,” he wrote, “it may not be changing the inevitable outcome of the underlying coronary artery disease.”

IMAGES:

world cup chart New England Journal of Medicine

world cup chart hours New England Journal of Medicine

For more on this story go to: http://www.businessinsider.com/can-world-cup-stress-really-give-you-a-heart-attack-2014-7#ixzz36QYuVx3Y

Heart attack photo: guardianlv.com