(Reuters Health) - Concussion rates plummeted in Ivy League football under new rules moving the kickoff line in an attempt to minimize the risk of high speed head-on collisions during this part of the game, a new U.S. study suggests.

The intention of the 5-yard (4.57 m) move was to have more kickbacks land in the end zone, reducing the likelihood that the receiving players would advance the ball. Ivy League football coaches recommended this change after reviewing 2015 data showing kickoffs accounted for 6 percent of all plays but 21 percent of concussions.

Over the first two seasons with the new kickoff rules, the average annual concussion rate plunged to about 2 per 1,000 kickoffs from almost 11 per 1,000 over the last three seasons before the rule change took effect.

That’s “a 69 percent reduction in the rate of concussion,” said lead study author Douglas Wiebe of the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.

“The action taken by Ivy League leadership based on epidemiologic evidence demonstrates how a simple but strategic policy change can reduce sport-related concussion,” Wiebe said by email.

Kickoffs can be one of the most dangerous plays in football because players rush toward each other over a long distance, creating the potential for severe head injuries during tackles when they collide at high speeds.

With approval from the National Collegiate Athletic Association (NCAA), the eight private universities in the Ivy League conference moved the kickoff line from the 35-yard line to the 40-yard line and moved the so-called touchback line from the 25-yard line to the 20-yard line.

Concussion rates for other types of plays also declined, researchers found, from an average of about 2.6 per 1,000 plays before the rule change to about 1.2 per 1,000 plays afterward. This difference, however, was too small to rule out the possibility that it was due to chance.

The study was funded by the Ivy League and the Big Ten athletic conference.

One limitation of the study is that the results might have been affected by a rule in 2016 eliminating full-contact hitting in practices, the study authors note in JAMA.

“It is difficult to know whether the concussion rates are due solely to the rule change versus the culture around preventing concussions during football in general such as avoiding contact, and better engineered and maintained helmets,” said Dr. Monica Vavilala, director of the Harborview Injury Prevention and Research Center at the University of Washington in Seattle.

“The higher rates prior to rule change may have been associated with greater ball advances and more collisions,” Vavilala, who wasn’t involved in the study, said by email.

While the study results show it’s possible for players to adapt to new rules and that rule changes can reduce concussions, it remains to be seen how scoring might be impacted by the 5-yard shift in the kickoff and touchback lines, Vavilala noted.

Still, the results suggest widespread implementation of this kickoff rule change could prevent more concussions in football, said Jonathan Godbout, faculty director of the Chronic Brain Injury Program at the Ohio State University Wexner Medical Center in Columbus.

“A simple rule change is having a positive impact and is reducing concussion risk in the players,” Godbout, who wasn’t involved in the study, said by email. “That’s precisely what it was intended to do.”

SOURCE: bit.ly/2IvUAbW JAMA, online October 1, 2018.