Joining the military service comes with serious risks. Many soldiers die in military operations and those who managed to survive continue to be influenced and affected by their experience. Warfare-related injuries, in particular, have long term impact on health and a new study suggests that military veterans who experienced traumatic brain injury (TBI) have increased risks of developing cognitive problems and are likely to die an early death.

In a new study published in the journal Neurology on June 25, researchers followed 188,764 veterans who had no dementia at the beginning of the study, 1,229 of whom were diagnosed with traumatic brain injury.

By following the veterans for nine years, the researchers found that 16 percent of the study participants who had brain injury developed dementia and only 10 percent of the veterans who were not diagnosed with brain injury developed the condition. In the U.S., about 5.3 million people currently suffer from Alzheimer's disease, the most prevalent form of dementia, which is marked by a progressive decline in a person's ability to think and reason clearly.

Veterans who had traumatic brain injury also tend to develop dementia two years earlier than their counterparts who did not suffer from TBI developing dementia at 78.5 years of age compared with 80.7 in those who did not suffer from severe brain trauma. The risks are likewise higher with veterans who had severe brain injury and who also suffered from depression, cerebrovascular disease or post-traumatic stress disorder (PTSD).

"Our results suggest that TBI in older veterans may predispose toward development of symptomatic dementia and raise concern about the potential long-term consequences of TBI in younger veterans and civilians," the researchers wrote.

Early death also appeared to be associated with traumatic brain injury. Those diagnosed with TBI but did not develop dementia died at 77 years of age, more than two year earlier than those who suffered from severe brain trauma who died at 79.3 years old on average.

"Our results suggest that [brain injury] may increase the risk of developing dementia in older veterans, with an age of onset about two years earlier," study researcher Deborah Barnes, from the University of California-San Francisco, told Health Day. "So clinicians may want to keep an eye out for signs of cognitive impairment in older veterans with a history of [brain injury]"

Barnes said it isn't clear why injuries in the head play a role in the development of dementia. Nonetheless, she opined that the brain becomes more vulnerable to dementia when it had more injury. She also said that the brain injury may cause the development of brain plaques that are associated with Alzheimer's disease.