Concussion rates in college football players have doubled since new rules were put in place to help manage the number of head injuries, a new study shows.

Researchers found that the number of concussions reported by players at three different Division 1 college football programs went from 23 head injuries in the season before new NCAA concussion rules went into effect in 2010 to 42 during the next season.

The increase in the number of concussions is not simply that more athletes are getting hurt playing football, which may increase their risk of brain injuries as they get older. Another explanation might be improved awareness of the problem and that symptoms from these head injuries were previously under-recognized.

"The timing of the new NCAA regulations and the increase in reported concussions could certainly be attributed to under-reporting from players and coaches in the past, researcher Kelly G. Kilcoyne, MD, says in a news release. He is an orthopaedic surgeon at the Walter Reed Army Medical Center in Bethesda, Md.

The study looked at concussion data from football practices and games at three U.S. military service academies: the U.S. Naval Academy in Annapolis, Md., the U.S. Military Academy at West Point, N.Y., and the U.S. Air Force Academy in Colorado Springs, Colo. It compared the number of head injuries reported to athletic trainers by players and coaches during the 2009-2010 season to those occurring in 2010-2011.

The new findings were presented at the American Orthopaedic Society for Sports Medicine annual meeting in Baltimore.

New rule, new concussion rates

In April 2010, the National Collegiate Athletic Association put in place new guidelines for college sports teams that required each school to have a concussion management plan.

As part of this plan:

Athletes are informed of concussion symptoms at the start of each season.

Athletes sign a statement agreeing to report concussion-related symptoms to the medical staff.

Athletes who have a concussion must be removed from the sport for at least one day.

Athletes cannot return to play until a team doctor clears them to participate once symptoms have been resolved.

All three of the football programs at the schools had an increase in the number of reported concussions in the first season after the new NCAA rules took effect.

When data from the three programs was combined, researchers found 42 concussions in more than 36,000 athlete exposures in games or practices during 2010-2011 compared to 23 concussions in nearly 40,500 exposures the previous season. This meant the concussion injury rate for football had doubled under the new guidelines.

Concussion symptoms may occur hours or days after a bump or blow to the head. They may include a headache, vomiting or nausea, weakness, dizziness, blurred vision, concentration and memory problems, and irritability.

This study was presented at a medical conference. The findings should be considered preliminary, as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.