For combat vets, the Veterans Administration has a tough message. To get a diagnosis of traumatic brain injury (TBI), it takes more than just having your bell rung by a roadside bomb in Iraq and Afghanistan. For the docs in the VA, the bell has to be still ringing.

That’s a very different standard than employed by the Department of Defense.  Between 2000 and 2012, the DoD diagnosed five times more of its soldiers with TBI than the VA did. And even the DoD figures fall short of what the Rand Report had predicted five years ago.

In 2008, the Rand Corp. did an independent survey of 1,965 service members and veterans. Due primarily to the prevalence of roadside bombs (improvised explosive devices, or IEDs), it estimated that 19 percent of the 1.6 million soldiers serving in Iraq and Afghanistan – about 320,000 soldiers – would come home with possible TBIs.

But the conflict lasted longer than Rand had expected, and more than 2.4 million service members have cycled through Iraq and Afghanistan. According to the Defense and Veterans Brain Injury Center, 266,810 soldiers were diagnosed with TBI from 2000-12.

By comparison, the VA has only diagnosed about 54,000 Iraqi/Afghan vets with TBI.

So what’s been happening here? Did most of the soldiers who had had their bells rung by bombs suddenly get better after they left the service?

Actually, that’s pretty much what the VA says.

According to Dr. David Cifu, national director of the VA’s Physical Medicine and Rehabilitation Services, about 55 percent of the soldiers returning from Iraq and Afghanistan, some 700,000 vets, have sought VA health care, and 7.8 percent of them – about 54,000 vets — have been diagnosed with TBI. By comparison, the VA had diagnosed 834,000 Iraqi/Afghan vets with PTSD as of last year, which is more than the Rand Report projections.

Cifu told me that in 2007, a four-question screening exam was devised to determine the existence of a traumatic brain injury. Administered in person by 108 TBI screening teams, the assessment was also presented to those who had previously complained of possible TBI systems. It found that about 20 percent of the returning vets had a possible injury and about 40 percent of them tested positive, i.e. about 8 percent of the total.

All vets who have suffered an alteration of consciousness in combat remain in a registry, Cifu said, but only those who have experienced 17 to 21 symptoms lasting three months or longer are offered treatment if they wish it. Without symptoms, he said, there’s no need for treatment.

Note that this 8 percent is only of the 55 percent in the VA system; another 45 percent chooses not to participate in the VA system or opts for private care. The Center for Investigative Reporting also said that 900,000 vets have filed claims and are waiting for the VA to process them, a number that could grow to 1 million by the end of this month.

But Cifu told me that his TBI assessment teams have interviewed 99 percent of the vets in the VA system who have claimed head injuries and only this small 7.8 percent continue to experience persistent symptoms.

That begins to make sense, though, after taking a closer look at the DoD’s TBI numbers. More than 82 percent of the TBIs are classified as mild, which is defined as “a confused or disoriented state which lasts less than 24 hours; loss of consciousness for up to 30 minutes; memory loss lasting less than 24 hours; and structural brain imaging (MRI or CT scan) yielding normal results.” And the majority of them were everyday concussions from workplace or home accidents, not the result of battlefield injuries.

In fact, only 28,700 active-duty soldiers were diagnosed with moderate, severe or penetrating TBIs in that period.

On another topic, Cifu is skeptical of preliminary studies at Boston University and the Boston VA Healthcare System that have concluded that brain injuries may result in degenerative brain disorders, known as chronic traumatic encephalopathy (CTE).

“Time-release brain degeneration following minor head trauma is not scientifically proven,” said Cifu, noting that CTE is rare, it may have many cause, and it appears to be associated with multiple injuries, moderate to severe injuries, and concomitant psychological factors – but any association with an isolated, single concussion has not been proven scientifically in longitudinal studies.

“Typically, it only occurs in people who have had multiple injuries and conditions, and particularly those with initial injury that is at least moderately severe,” he added.

Before jumping to conclusions, “I would wait until the real research has been done,” he said. “Telling someone that they had a brain injury five years ago or five minutes ago that may in some way cause their brain to eventually decline isn’t particularly helpful to a patient, other than causing anxiety. Since we don’t have any longitudinal studies that follow patients for anything longer than six months, we don’t really understand this phenomenon.

“We certainly can educate patients that there may be a risk, just as there may be a risk from smoking, drinking, high cholesterol, high blood pressure, but these are all better defined risks and ones we have a specific treatment (or prevention) for. There may also be a genetic risk of trauma related degenerative brain disease and those with an elevated risk should also manage all their other potential risks closely. So while it’s important to be aware of the emerging literature and research from sports and military injury, there are no clear conclusions that have been reached and more importantly, no meaningful advice to offer someone who’s had a brain injury other than to avoid future activities that may cause another one and to optimize their overall health (as you would with any patient).

“This information should be conveyed clearly to patients in a way to encourages them to work hard to enhance their physical and emotional wellness rather than scaring them with some vague fear of inevitable neurodegeneration. I’d rather empower them by saying if you follow your exercise program, eat well, don’t smoke, drink in moderation, see a primary care clinician regularly, utilize relaxation strategies, do things that encourage your productivity and your intellectual stimulation, be part of social groups, have family time, then you are doing everything possible to prevent, lower the risk or reduce the speed of degenerative processes of the brain that may occur. I’d rather give the patient control and give them choices rather than just plant the seed that they’re going to get dementia.

“The key take away point is that there really is no rigorous evidence — zero — in any study that a single concussion can lead to CTE or any cognitive decline,” Cifu said.