Abstract Text: Two highly prevalent and impactful consequences of traumatic brain injury (TBI) are cognitive dysfunction and chronic pain. The literature indicates greater cognitive dysfunction in non-TBI-related chronic pain populations versus healthy controls across cognitive domains and outcome measures (i.e., objective and subjective). For TBI-related chronic pain, only a few studies have investigated the relationship between cognition and chronic pain. These studies were exclusive to posttraumatic headaches following mild TBI and reported discordant results, likely due heterogeneity in outcome measures and a potential moderation of TBI-related emotional distress. No study to date has measured cognition and co-occurring chronic pain in persons with TBI of all severities, nor has any study directly compared cognition in groups of individuals with TBI separated by the presence of chronic pain. A cross-sectional analysis was conducted on data collected during the baseline visit of an experimental study (full protocol doi: 10.1016/J.CONCTC.2022.100963). A convenience sample (age 18-65) with TBI of any severity at least one year prior was recruited. Cognition-related exclusion criteria included current uncontrolled psychiatric illness (e.g., major depression), a history of neurological disorders beyond TBI (e.g., stroke), a history of substance abuse, and current use of medications that might impact cognition (e.g., steroids). Neuropsychological assessments administered included the California Verbal Learning Test-II (CVLT-II), Symbol Digit Modalities Test (SDMT), Trail Making Test (TMT), the Wechsler Adult Intelligence Scale Letter Number Sequencing (WAIS-IV LNS) subtest, and Test of Premorbid Functioning (TOPF). Self-report questionnaires administered included the Attention Processing Training-II (APT-II), Neurobehavioral Symptom Inventory (NSI), Everyday Cognition (eCog), Brain Injury Coping Skills Questionnaire (BICSQ), and TBI Quality of Life (TBIQOL). Any participant who reported current chronic pain, defined as pain at least every other day for the last three months, also completed the McGill Pain Questionnaire (MPQ). Using a dichotomous variable of chronic pain (1= yes, 0 = no), differences between groups across all baseline measures were analyzed using independent t-tests in SPSS version 26 (IBM, Inc., Armonk, NY). Of the 24 participants who completed the baseline visit, 10 (42%) reported chronic pain. The proportion of females was greater in the chronic pain group (60% vs 14.29% female). In each group, three individuals sustained injuries of mild (or complicated mild) severity, resulting in a slightly higher proportion of mild TBI in the chronic pain group (30% vs 21.43%). The chronic pain group reported significantly worse subjective global cognitive function, with specific complains in areas of learning-memory and executive function. Specifically, the chronic pain group reported a higher score on the eCog total (average: 103.90 [standard error: 14.12] vs 60.86 [5.47], t(11.72)=-2.84, p=0.004), on the TBIQOL executive function subscale (35.20 [3.32] vs 43.29 [1.69], t(22)=2.36, p=0.028), and TBIQOL learning-memory subscale (18.70 [2.25] vs 24.93 [1.05], t(22)=2.76, p=0.012). The only difference on an objective neuropsychological assessment to support subjective memory deficits with chronic pain was worse performance on the CVLT-II Short Delay Cued Recall (standardized score -1.20 [0.59] vs 0.04 [0.26], t(22)=2.11, p=0.046) in the chronic pain group. The final significant group difference was on the TBIQOL fatigue subscale (28.60 [3.92] vs 18.29 [2.25], t(22)=-2.44, p=0.023) suggesting greater fatigue with chronic pain. It is clear that persons with TBI-related chronic pain report more subjective cognitive deficits across several domains than those without TBI-related pain. This relationship deserves further investigation and may greatly impact everyday function, despite similar objective scores on several neuropsychological assessments to those without chronic pain. However, the battery of neuropsychological assessments administered here was small, and to better understand the relationship between chronic pain and objective cognition, future studies should employ a more comprehensive battery of assessments. While most emotional symptoms (e.g., anxiety or depression) were similar across groups, fatigue was significantly worse and should be measured more consistently in research on persons with TBI and co-occurring chronic pain. This analysis is limited by the small sample, but nevertheless supports inclusion of chronic pain in research and treatment interventions as an influential factor on cognition following TBI of any severity.
