NFL players who suffered concussions last season spent an average of 16 days off the field, a significant increase from previous years, according to new injury data from 2012.
That is an increase of nearly 10 days per concussion since 2009, though the total number of concussions have remained relatively flat in that time, said Dr. Jesse David of Edgeworth Economics, which conducted an independent analysis of the data provided by the NFL Player's Association.
The extended recovery time for concussions is an indication that the league's efforts to better identify and treat head injuries are working, and not that the severity of head injuries is getting worse, NFL spokesman Greg Aiello told USA TODAY Sports.
Players missed an average of only 6.4 days after suffering a concussion in 2009, and only 4 days per concussion in 2005, according to the research.
"It is a reflection of how the injury is being treated more cautiously based on revised protocols and the current judgment of our medical staffs," Aiello said.
The NFL in recent years has changed its concussion protocol to add baseline testing for all players along with strict guidelines for removing players who might have suffered a head injury from games and practices.
Players must be cleared by two doctors, including one independent physician, before being allowed to return to practice. The league this year has mandated that an independent neurologist evaluate players on the sideline during games.
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The injury data, from the NFL's Injury Surveillance System, showed that players suffered 265 concussions in 2012, from the start of training camp through the end of the postseason, one fewer than in 2011 and five fewer than 2010, when the number of concussions diagnosed rose dramatically because of NFL policy changes.
Though the number of head injuries appears to have leveled out, the total number of severe injuries is up, David said. The study defines severe injuries as those that force a player to miss at least two games or requires surgery.
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Players in 2012 suffered 1,496 injuries that resulted in at least a two-game absence, and 345 injuries that required surgery. Both were all-time highs, David said.
"The key takeaway is that injuries continue to increase," David said. "The frequency -- whether you're talking about per player, per game or per season -- the numbers are going up, and they have been for about a decade. That's particularly true for severe injuries."
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