Sports fanatics have long suspected it, but now German researchers have confirmed it just in time for Sunday's Super Bowl: Intense athletic contests and equally passionate interest in those games can be hazardous to viewers' health.
When Germany competed in pivotal soccer matches during the 2006 World Cup, the incidence of heart attacks and other acute cardiovascular conditions soared in Bavaria, scientists report in today's New England Journal of Medicine.
People with previously diagnosed heart problems stood the greatest risk: Cardiac episodes were four times higher for them when the German team was playing than on nongame days.
Overall, the German doctors found, the rate of heart attacks and other acute cardiac problems was 3.26 times higher for men and 1.82 times higher for women during World Cup matches.
The study confirms what specialists such as Rich Serino, the veteran chief of Boston's emergency medical services division, have long known. Though EMS has no statistics on game-day heart attacks, Serino said his staff has repeatedly treated fans who suffer heart trouble during sporting events, usually while watching them on television.
"It depends on the game," he said. "If it's a blowout, less so, but if it's the nail-biters, with a field goal or touchdown in the last few seconds," then, he said, "it's more stressful."
So what's a fan to do? First of all, heart patients "should regularly take their prescribed drug regimen," said the paper's senior author, Dr. Gerhard Steinbeck of Ludwig-Maximilians Universitat in Munich. "They should not stop it."
Do not drink too much alcohol or overeat junk food, he said. "Just be careful." In case of symptoms such as chest pain or heart palpitations, do not delay seeking treatment, he said.
Might it help, perhaps, to keep reminding yourself that it's just a game?
Unlikely, said Dr. Martin A. Samuels, chairman of neurology at Brigham and Women's Hospital, who researches the phenomenon of deadly excitement.
On one hand, he said, "watching a game, no matter how much of a fan you are, there is a part of you that knows this is a game, it's not real," and poses no personal threat.
But when the body is hit by a major storm of stress, it "is completely unconscious, you cannot access this part of your nervous system consciously," he said.
It is not completely understood how stress brings on heart attacks, but adrenaline, the stress hormone, is believed to be the central culprit.
Steinbeck emphasized that his findings by no means translate into general advice to fans to skip big games altogether.
The overall risk of heart attack is still small, Steinbeck said. He and his colleagues calculate that on a normal day, the general risk for cardiac trouble severe enough to need medical treatment is 1 in 100,000 people. On the day of a 2006 World cup game with Germans playing, the risk rose to between 2 and 3 per 100,000.
More sobering, perhaps: They calculated that for a man with known cardiac problems, over the course of all seven World Cup games, the risk was about 100 times bigger: 1 to 2 per 1,000 people. Furthermore, the German study found that the most deliciously exciting moments of games are also the most dangerous, whether the home team ultimately wins or not.
Heart problems increased in knockout games. when more was at stake, and in games that involved make-or-break penalty-shootouts and last-minute goals.
Still, Steinbeck suggested that Patriots fans "not be too much disturbed" about his findings.
Rather than the upcoming Super Bowl, the closest local comparison to the World Cup may be back in 2004, when the Red Sox were three games down in the American League Championship Series and fought back in four nail-biting games against the Yankees to earn a World Series berth.
Immediately after the Sox won the first Series game, a fan went into cardiac arrest and collapsed outside Fenway, recalled Serino. The man was resuscitated.
No published research tracked heart attacks during those heart-stopping Red Sox games, but one study did take a look at emergency room visits during two key ALCS and World Series games and found that they went down about 15 percent at a half-dozen metropolitan Boston hospitals. Apparently, patients with non-life-threatening illnesses were so riveted by the games that they postponed seeking medical help.
Those findings square with the general drop in calls that emergency services have long seen during high-stakes sports matches, despite cardiac risks, Serino said.
For this weekend, he said, the emergency services are making extra preparations, not for the cardiac cases, but for the expected revelers after a Patriots win.
Carey Goldberg can be reached at email@example.com.