Lead author Dr. Stacy Wood of North Carolina State University and colleagues at the University of South Carolina evaluated traffic fatalities after 271 professional and college football and basketball championship, tournament and rivalry games played from 2001 to 2008.
The researchers looked at traffic fatality data in the area where the game was played, and in the hometowns of the winning and losing teams. A panel of sports experts rated how close each game was on a scale from 1 to 5, with 1 a blowout and 5 a nail-biter.
The study, published in the Journal of Consumer Research, found traffic fatalities increased significantly after nail-biters -- each increase in the closeness rating was associated with a 21 percent increase in fatal accidents.
The increase in fatalities occurred in the hometown of the winning team, Woods says.
"During a close game, testosterone increases for the fans as well as the players -- that has been established by previous studies," Wood says in a statement. "After the game, testosterone levels drop for the losing side, but spike for the winning side. Because testosterone is linked to aggressive behavior and potentially aggressive driving, we hypothesize that this may play a role in the increased number of traffic fatalities in areas with a high proportion of winning fans."