THURSDAY, Dec. 4 (HealthDay News) -- A new report provides evidence linking traumatic brain injury sustained by troops in combat in Iraq and Afghanistan to a variety of long-term health problems including dementia, aggression, depression and symptoms similar to those seen in Parkinson's disease.

But the Institute of Medicine committee charged with developing the report also pointed to a troubling lack of scientific data on such injuries, which are fairly recent in the history of warfare.

"The real bottom line significant finding is that there's not a good human literature on the kinds of neurotrauma seen in Iraq and Afghanistan caused by blasts," said Dr. George W. Rutherford, vice chair of the department of epidemiology and biostatistics at the University of California, San Francisco, School of Medicine. "The human literature is really about people who've had [brain injury] from car crashes or falling down stairs and, in the military, from shrapnel or gunshots. We're all worried that blast neurotrauma hasn't really made it into the human literature."

This makes it difficult, if not impossible, to anticipate and hopefully mitigate the long-term consequences of such injuries, added Rutherford, who chaired the committee that wrote the report.

"They focused on blast-induced neurotrauma, a blast injury that leaves the head without any external marks of even being knocked about," explained Keith Young, vice chair for research at Texas A&M Health Science Center College of Medicine and Neuroimaging and Genetics Core Leader for the VA Center of Excellence for Research on Returning War Veterans. "The blast is so close and so large, it seems to be shaking the brain. My guess is that this causes micro-bleeds," Young said.

The current U.S. conflicts in Afghanistan and Iraq, which have been ongoing since Oct. 7, 2001 and March 2003, respectively, differ vastly from previous combat deployments in terms of injuries sustained. They differ even from injuries seen in the 1991 war, with more deaths, multiple traumas and more traumatic brain injuries (TBI).

Blast injuries are considered the "signature" wound of the Iraq war and are largely a result of newer, more powerful explosive devices.

"One cause of the high rates of TBI is relatively simple: survival," Young said. "The reason more people are surviving is better on-the-scene treatment and medivacing to facilities within minutes rather than hours."

According to the Department of Defense (DOD), more than 5,500 soldiers had suffered TBIs as of January 2008, accounting for about 22 percent of all casualties, as compared with only 12 percent to 14 percent of all combat casualties during the Vietnam War.

In an effort to detail the long-term consequences of TBI, the committee looked at almost 2,000 studies on the subject.

The committee found evidence of a causal relationship between penetrating TBI and unprovoked seizures as well as death, and between severe or moderate TBI with unprovoked seizures.

There was "sufficient" evidence of an association between TBI and decline in neurocognitive function, long-term unemployment and problems with social relationships; Alzheimer's-like dementia, endocrine dysfunction, depression, aggressive behavior, memory problems and early death.

There was "limited/suggestive" evidence of an association between moderate or severe TBI and diabetes or psychosis; and between mild TBI and visual problems, dementia, post-traumatic stress disorder and suicide.

"Inadequate/insufficient" evidence existed on the relationship between moderate or severe TBI and brain tumors; mild TBI and employment and social functioning problems, bipolar disorder or attempted suicide; TBI and multiple sclerosis or amyotrophic lateral sclerosis (Lou Gehrig's disease).

The committee put forth a number of recommendations.

"Three of the recommendations are really directed towards the DOD and the VA about how to keep track of this stuff so people in the future can put registries together," Rutherford said. "Once you know that, you can start answering questions, are five of these five times as bad as one, what's the long-term risk of any bad outcome."

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