Because of the "brain-heart connection" between emotions and cardiac health, some of the most invested fans may literally live and die by how their team fares. When the Pittsburgh Steelers won a classic Super Bowl over Arizona in 2009, Pittsburgh-area doctors saw 25% fewer circulatory heart-related deaths than average over the next eight days, says Robert Kloner, a cardiology professor at the University of Southern California.
But after the New York Giants stopped the previously undefeated Patriots in the Super Bowl in 2008, the number of circulatory heart-related deaths in Massachusetts climbed 20% over the next eight days. It's not that people should stop watching sports, says Dr. Kloner, whose research was published in 2013 in Clinical Research in Cardiology. But he suggests that fans stay aware of emotional stressors that can have a negative physical impact, and try not to get too worked up.