SAN FRANCISCO -- The U.S. Navy's top doctor says the service has made gains in developing new screening protocols and treatments for concussions, but acknowledged more research is needed.
"We're still a way's away from finding that one magic test that can tell you just how severe it is, but we've change the game," he said.
For example, in Afghanistan and in other combat zones, troops who get a concussion are now given a series of tests in which they have to answer questions and react to blinking lights, Nathan said.
"We now know, based on how they respond to those tests, whether or not they're fit to return to duty or need to take a timeout for a few days or take a timeout and be relieved from duty," he said. "And we have some pretty objective criteria now that can tell us what a concussion has done." He added, "We have a ways to go, but our situational awareness is much better now."
Interestingly, the vast majority of traumatic brain injuries that occur in the military come from non-combat injuries, such as motorcycle and motor vehicle accidents, Nathan said.
Indeed, of the 316,341 incidents of traumatic brain injury recorded across all branches of service from 2001 through the first quarter of 2015, just 47,925 -- or about 15 percent -- were combat-related, or "deployment associated," according to statistics recently provided to Military.com by the Pentagon's Defense and Veterans Brain Injury Center in Maryland, which oversees TBI research.
During the height of U.S.-led wars in Iraq and Afghanistan, the percentage climbed as high as 26 percent in 2007, and dropped below 23 percent only once through 2011, reaching 19 percent in 2009, the statistics show.
"We've learned a tremendous amount about concussion care from the combat arena," Nathan said. "What we've learned actually is care that we've brought back and is now being implemented at some universities and sports teams across the nation as we partner with professional sports as well to look at how we can reduce, prevent and care for concussions."
Nathan was referring the Defense Department's partnerships with the National Football League and the National Collegiate Athletic Association to research brain injuries. For example, the Army beginning in 2007 put blast sensors into tens of thousands of helmets to monitor head injuries from roadside bombs in Afghanistan. And the Pentagon and NCAA last year announced a joint study into concussions.
A recent article in The New York Times reported that boxing accounts for 20-25 percent of concussions at West Point, the Air Force Academy and the Naval Academy. "So far this school year, boxing has caused a quarter of all concussions at the Naval Academy -- more than twice as many as football," it stated.
Companies such as BAE Systems make small sensors that monitor and record the overpressures and accelerations experienced through head impacts or movements. The British-based defense contractor's Headborne Energy Analysis and Diagnostic Systems, for example, is mounted inside a combat helmet to measure the pressure and angular and linear accelerations from traumatic events.
"If an explosion, for example, causes quick head movements or pressures that exceed predefined thresholds, HEADS records the event," its website states. "This stored event data can later be easily downloaded through a USB connection, allowing medical personnel to receive information crucial in determining the potential for head and brain injuries."
Nathan said the partnerships with outside organizations are paying off.
"It's not standard practice yet, but the experimental prototypes are allowing us to determine what types of hits and what types of helmets provide the best protection against a concussion," he said.
"One of our challenges is that two individuals can receive the same apparent force injury to their heads and one comes out completely functional and doing fine and the other has headache and some post-concussive signs," Nathan said. "So what it is about individual makeup as well that may make you more susceptible to an injury than your buddy?"
He added, "The science, although it's fascinating, it's urgent, because we want to get on top of this in a hurry."
--Bryant Jordan contributed to this report.