Baseline Intelligence Best Predicts TBI Outcome

WASHINGTON — High intelligence may be protective against brain injury-associated cognitive dysfunction, judging from follow-up data on veterans injured during the war in Vietnam, Jordan Grafman, Ph.D., said at a meeting sponsored by the Institute of Medicine.

Dr. Grafman, chief of the cognitive neurosciences section of the National Institute of Neurological Disorders and Stroke, presented new data from 35 years of following Vietnam War veterans with traumatic brain injury (TBI). The study is the most recent phase in the ongoing Vietnam Head Injury Study, a long-term follow-up of veterans who suffered head injuries in combat. The cohort included 199 men with TBI and 55 controls; their average age at most recent follow up was 59 years.

Participants completed a variation of a U.S. Army classification test used to assess mental ability. The test was similar to an intelligence test that the soldiers took when they first enlisted. Overall, 4.5% of the participants scored less than 24 on the Mini-Mental State Examination, but those who scored lower also had below-average baseline intelligence scores.

The controls showed a cognitive decline with age, and the soldiers with penetrating head injuries showed a slightly greater decline, even when investigators controlled for a host of variables.

“But if you look at subgroups, those with the lowest preinjury intelligence scores had the most cognitive decline from preinjury to follow-up, and the difference was statistically significant, compared with controls,” Dr. Grafman said. He also noted that soldiers with head injuries who show exacerbated cognitive decline as they age may be mistakenly diagnosed with dementia, when in fact their increased cognitive decline results from a combination of aging and the size of their lesions.

Based in part on these findings, Dr. Grafman does not believe that TBI is always a precursor to Alzheimer's disease. But the long-term findings suggest that the location of the injury contributes to late-life cognitive decline and other symptoms.

“Lesions of the caudate nucleus of the brain significantly and consistently predicted late-life cognitive decline, and may indicate the importance of certain neurotransmitters in maintaining functions as we age,” Dr. Grafman said.

By contrast, the location of a TBI can be protective, too. Posttraumatic stress is clearly part of the experience of war, especially if someone experiences combat, Dr. Grafman said. But none the men with injuries to the amygdala showed signs of posttraumatic stress disorder, whereas 18% of those men with ventromedial prefrontal cortex lesions and more than 40% of patients with lesions elsewhere in the brain had developed PTSD over time since their injuries.

Dr. Grafman emphasized the importance of longitudinal studies for brain injury patients in general, and for veterans in particular, because baseline data are often available. “Preinjury intelligence is by far the best predictor of outcome, no matter what other variables you throw in,” Dr. Grafman said, based on the 35-year data and data from the same group of veterans at 5 and 15 years' follow-up. Data gathered on the cohort at 10 years showed individuals who scored higher on baseline intelligence tests were more likely to be working years later, and they were more able to handle daily activities, compared with those who had lower baseline intelligence scores.

Veterans are an outstanding patient group, and a systematic plan is needed to keep them from being lost in the medical system, Dr. Grafman noted, adding, “There needs to be a well-run centralized database for the registry of head-injured soldiers with a small number of manageable variables.”

WASHINGTON — High intelligence may be protective against brain injury-associated cognitive dysfunction, judging from follow-up data on veterans injured during the war in Vietnam, Jordan Grafman, Ph.D., said at a meeting sponsored by the Institute of Medicine.

Dr. Grafman, chief of the cognitive neurosciences section of the National Institute of Neurological Disorders and Stroke, presented new data from 35 years of following Vietnam War veterans with traumatic brain injury (TBI). The study is the most recent phase in the ongoing Vietnam Head Injury Study, a long-term follow-up of veterans who suffered head injuries in combat. The cohort included 199 men with TBI and 55 controls; their average age at most recent follow up was 59 years.

Participants completed a variation of a U.S. Army classification test used to assess mental ability. The test was similar to an intelligence test that the soldiers took when they first enlisted. Overall, 4.5% of the participants scored less than 24 on the Mini-Mental State Examination, but those who scored lower also had below-average baseline intelligence scores.

The controls showed a cognitive decline with age, and the soldiers with penetrating head injuries showed a slightly greater decline, even when investigators controlled for a host of variables.

“But if you look at subgroups, those with the lowest preinjury intelligence scores had the most cognitive decline from preinjury to follow-up, and the difference was statistically significant, compared with controls,” Dr. Grafman said. He also noted that soldiers with head injuries who show exacerbated cognitive decline as they age may be mistakenly diagnosed with dementia, when in fact their increased cognitive decline results from a combination of aging and the size of their lesions.

Based in part on these findings, Dr. Grafman does not believe that TBI is always a precursor to Alzheimer's disease. But the long-term findings suggest that the location of the injury contributes to late-life cognitive decline and other symptoms.

“Lesions of the caudate nucleus of the brain significantly and consistently predicted late-life cognitive decline, and may indicate the importance of certain neurotransmitters in maintaining functions as we age,” Dr. Grafman said.

By contrast, the location of a TBI can be protective, too. Posttraumatic stress is clearly part of the experience of war, especially if someone experiences combat, Dr. Grafman said. But none the men with injuries to the amygdala showed signs of posttraumatic stress disorder, whereas 18% of those men with ventromedial prefrontal cortex lesions and more than 40% of patients with lesions elsewhere in the brain had developed PTSD over time since their injuries.

Dr. Grafman emphasized the importance of longitudinal studies for brain injury patients in general, and for veterans in particular, because baseline data are often available. “Preinjury intelligence is by far the best predictor of outcome, no matter what other variables you throw in,” Dr. Grafman said, based on the 35-year data and data from the same group of veterans at 5 and 15 years' follow-up. Data gathered on the cohort at 10 years showed individuals who scored higher on baseline intelligence tests were more likely to be working years later, and they were more able to handle daily activities, compared with those who had lower baseline intelligence scores.

Veterans are an outstanding patient group, and a systematic plan is needed to keep them from being lost in the medical system, Dr. Grafman noted, adding, “There needs to be a well-run centralized database for the registry of head-injured soldiers with a small number of manageable variables.”

WASHINGTON — High intelligence may be protective against brain injury-associated cognitive dysfunction, judging from follow-up data on veterans injured during the war in Vietnam, Jordan Grafman, Ph.D., said at a meeting sponsored by the Institute of Medicine.

Dr. Grafman, chief of the cognitive neurosciences section of the National Institute of Neurological Disorders and Stroke, presented new data from 35 years of following Vietnam War veterans with traumatic brain injury (TBI). The study is the most recent phase in the ongoing Vietnam Head Injury Study, a long-term follow-up of veterans who suffered head injuries in combat. The cohort included 199 men with TBI and 55 controls; their average age at most recent follow up was 59 years.

Participants completed a variation of a U.S. Army classification test used to assess mental ability. The test was similar to an intelligence test that the soldiers took when they first enlisted. Overall, 4.5% of the participants scored less than 24 on the Mini-Mental State Examination, but those who scored lower also had below-average baseline intelligence scores.

The controls showed a cognitive decline with age, and the soldiers with penetrating head injuries showed a slightly greater decline, even when investigators controlled for a host of variables.

“But if you look at subgroups, those with the lowest preinjury intelligence scores had the most cognitive decline from preinjury to follow-up, and the difference was statistically significant, compared with controls,” Dr. Grafman said. He also noted that soldiers with head injuries who show exacerbated cognitive decline as they age may be mistakenly diagnosed with dementia, when in fact their increased cognitive decline results from a combination of aging and the size of their lesions.

Based in part on these findings, Dr. Grafman does not believe that TBI is always a precursor to Alzheimer's disease. But the long-term findings suggest that the location of the injury contributes to late-life cognitive decline and other symptoms.

“Lesions of the caudate nucleus of the brain significantly and consistently predicted late-life cognitive decline, and may indicate the importance of certain neurotransmitters in maintaining functions as we age,” Dr. Grafman said.

By contrast, the location of a TBI can be protective, too. Posttraumatic stress is clearly part of the experience of war, especially if someone experiences combat, Dr. Grafman said. But none the men with injuries to the amygdala showed signs of posttraumatic stress disorder, whereas 18% of those men with ventromedial prefrontal cortex lesions and more than 40% of patients with lesions elsewhere in the brain had developed PTSD over time since their injuries.

Dr. Grafman emphasized the importance of longitudinal studies for brain injury patients in general, and for veterans in particular, because baseline data are often available. “Preinjury intelligence is by far the best predictor of outcome, no matter what other variables you throw in,” Dr. Grafman said, based on the 35-year data and data from the same group of veterans at 5 and 15 years' follow-up. Data gathered on the cohort at 10 years showed individuals who scored higher on baseline intelligence tests were more likely to be working years later, and they were more able to handle daily activities, compared with those who had lower baseline intelligence scores.

Veterans are an outstanding patient group, and a systematic plan is needed to keep them from being lost in the medical system, Dr. Grafman noted, adding, “There needs to be a well-run centralized database for the registry of head-injured soldiers with a small number of manageable variables.”