Rich Campbell of the Chicago Tribune noted the total number of concussions increased from 206 in 2014 to 271 the following season. Of those, 92 concussions in the regular season were from helmet-to-helmet impact, which is also at a four-year high and up from 58 in 2014.
The league's data shows there have been at least 200 reported concussions in every season since the current system for tracking began in 2012. Aside from helmet-to-helmet collisions, the playing surface (29) and the shoulder (23) were the other leading causes of regular-season head injuries in 2015.
The increase in concussion totals comes after three straight seasons in which the number dropped as the league implemented rules in an effort to reduce the number of head shots. The total had fallen from 261 in 2012 to 206 in 2014, the data shows.
Justin Tasch of the New York Daily News passed along comments Commissioner Roger Goodell made on SiriusXM NFL Radio about the issue back in December before the latest set of results were released.
"I think we're at 39 rule changes over the last 10 years to make our game safer," Goodell said. "They've had a dramatic impact on the game. We've seen reductions in concussions (by) 35 percent. We're seeing the rules protect the players from unnecessary injuries, and that's important."
The high watermark in concussions also comes despite the number occurring in practice falling to its lowest point since 2012. There were 37 concussions suffered in practice in 2015, down from 50 last year, leaving 234 that happened during game action, according to the data.
Head injuries are the biggest challenge facing the NFL right now, especially as more focus is placed on the issue.
Research has shown a connection between football, head injuries and chronic traumatic encephalopathy (CTE). And the situation was again brought to the forefront when the movie Concussion, starring Will Smith, was released in December.
The latest numbers show the NFL still has a lot of work to do in 2016 and beyond to limit head shots, especially those involving helmet-to-helmet collisions.