51 Impact of Blast Exposures on the Cognitive Abilities of Warfighters

Abstract

Objective:There is growing evidence to indicate that blast exposure military personnel experience throughout their career can have a negative impact on their brain health. The majority of research in the area of blast related neurotrauma has been focused on traumatic brain injury (TBI); however, the blast exposure may often be independent of TBI. It is common in both active duty military and veterans to report years of blast exposure from combat and training. The objective of this study was to explore the relationship between blast exposure and cognitive functioning in military personnel seeking treatment for a mild TBI.Participants and Methods:Participants were recruited from a military hospital while enrolled in a multidisciplinary treatment program for TBI. All patients had at least one diagnosed mTBI as well as persistent cognitive complaints. Exclusion criteria included invalid performance on a performance validity test and a symptom validity test. 97 participants were included in the analysis with an average age of 34.0 (SD = 7.9) and average 4.0 combat deployments (SD = 3.6). Blast exposure history was measured by the overall score from the Blast Exposure Threshold Survey (BETS) which assessed the frequency and duration of use of various blast sources. Outcomes included the Neurobehavioral Symptom Inventory (NSI) and the Global Deficit Scale (GDS) an objective measure of cognitive deficiency. GDS was calculated from seven measures: Hopkins Verbal Learning Test-Revised Total and Delayed Recall (HVLT-TR and HVLT-DR); DKEFS System Color-Word Condition 3 Inhibition (CW3), Color-Word Condition 4 Switching (CW4) and Trail Making Condition 3 Letter Sequencing (TM3), Paced Auditory Serial Addition Test (PASAT), and the Symbol Digit Modality Test (SDMT). Demographically corrected t-scores (M=50, SD = 10) were converted to deficit scores and averaged to calculate GDS. To adjust for nonnormal distributions, non-parametric statistics were examined.Results:The BETS was not related to GDS (rho = -.055); however, there was a significant correlation between higher levels on the BETS and better performance on measures of selective attention (PASAT rho = .307) and processing speed (SDMT rho = .218). The correlation between BETS and the other neuropsychological measures were not meaningful (all rho’s <.10). Those with an impaired GDS, did not differ from others on the BETS. BETS was also not associated with neurobehavioral symptoms (rho = .125). BETS had moderate correlations with number of combat deployments (rho =.483), severity of combat exposure (rho =.556). It was not related to education (rho = .004) or pre-morbid intelligence (rho =-.029).Conclusions:The BETS was not related to GDS (rho = -.055); however, there was a significant correlation between higher levels on the BETS and better performance on measures of selective attention (PASAT rho = .307) and processing speed (SDMT rho = .218). The correlation between BETS and the other neuropsychological measures were not meaningful (all rho’s <.10). Those with an impaired GDS, did not differ from others on the BETS. BETS was also not associated with neurobehavioral symptoms (rho = .125). BETS had moderate correlations with number of combat deployments (rho =.483), severity of combat exposure (rho =.556). It was not related to education (rho = .004) or pre-morbid intelligence (rho =-.029).