Examining Associations Between Environmental Exposures and Neurobehavioral Symptoms in Post-9/11 Veterans With a Probable History of TBI

OBJECTIVE: Prior research has established several risk factors for poor neurobehavioral outcomes after traumatic brain injury (TBI) in Iraq/Afghanistan-era-Veterans. However, no studies have examined the impact of environmental exposures on neurobehavioral symptoms in this population. The purpose of this study was to examine the relationship between environmental exposures and neurobehavioral symptoms in post-9/11 Veterans with a probable history of TBI. SETTING: Veterans Affairs (VA) Million Veteran Program (MVP). PARTICIPANTS: Participants included MVP-enrolled Veterans who completed the Veterans Health Administration's (VHA's) TBI Screening and Evaluation Program. Eligible participants were those who screened positive for TBI on the VHA Clinical Reminder Screen (N = 3370). DESIGN: Retrospective, cross-sectional design using secondary data analysis. MAIN MEASURES: Primary outcomes were 6 indices derived from the Neurobehavioral Symptom Inventory (NSI): total score (overall symptom severity), positive symptom total (symptom breadth), and 4 system clusters (vestibular, somatic/sensory, cognitive, and affective). Environmental exposures were self-reported by MVP surveys and included an exposure burden score and 7 individual exposure types: chemical or biological warfare agents; solvents/fuels; petroleum/combustion products; lead; other metals; pesticides; and open-air burn pits. RESULTS: The most frequently reported environmental exposures included petroleum combustion products (90.38%), burn pits (87.58%), and solvents/fuels (84.25%). Adjusted linear regression analyses, controlling for age, sex, race/ethnicity, and posttraumatic stress disorder status, showed significant positive associations between exposure burden and most neurobehavioral symptom outcomes (β = 0.13-1.08, all Ps < .001). In addition, there were several significant associations observed between each individual exposure variable and NSI outcomes, with the most consistent effects observed for other metals (β = 0.37-3.14, all Ps = <.001) and solvents/fuels (β = 0.88-2.95, all Ps = <.001). CONCLUSIONS: In post-9/11 Veterans with a probable history of TBI, environmental exposure burden and specific exposure types (particularly other metals and solvents/fuels) were associated with greater neurobehavioral symptom severity and breadth, suggesting environmental exposures as an additional, important contributor to chronic symptoms.