Distinguishing the Relative Impact of Post-Traumatic Stress Disorder and Traumatic Brain Injury on iPad-Measured Cognitive Function

Normative Reference Values for Crystallized-Fluid Discrepancy Scores for the NIH Toolbox Cognition Battery

INTRODUCTION

The purpose of this study was to translate NIH Toolbox Cognition Battery (NIHTB-CB) Crystallized-Fluid discrepancy scores into research and clinical practice with adults by providing normative data for discrepancy scores for both age-adjusted standard scores (SSs) and demographically adjusted T-scores.

METHOD

We included adult participants from the NIHTB-CB standardization sample who denied having neurodevelopmental, medical, psychiatric, or neurological conditions (n = 730; M = 47.4 years old, SD = 17.6, range: 18-85; 64.4% women; 63.1% White). Descriptive statistics were calculated for the Fluid and Crystallized composite scores and Crystallized-Fluid discrepancy score, along with correlations between the composite scores and reliability estimates of the discrepancy score. Percentiles were calculated for the discrepancy score, with stratifications by the gender, education, and Crystallized composite for the age-adjusted SSs and demographically adjusted T-scores (T).

RESULTS

Crystallized-Fluid discrepancy scores ranged from -40 to 44 (M = -0.63, SD = 14.89, Mdn = -1, interquartile range [IQR]: -11 to 10) for age-adjusted SSs and from -29 to 27 (M = -0.39, SD = 10.49, Mdn = -1, IQR = -8 to 7) for demographically adjusted T-scores. Crystallized-Fluid discrepancy scores of SS = 15 and T = 11 were at the 16th percentile (1 SD below the mean) and discrepancy scores of SS = 21 and T = 15 were at the 7th percentile (1.5 SD below the mean).

CONCLUSIONS

Crystallized-Fluid discrepancy scores may be, with future research, a useful within-person interpretive approach for detecting a decline from pre-injury or pre-disease levels of cognitive functioning. These normative reference values assist clinicians and researchers in determining the frequency at which given Crystallized-Fluid discrepancy scores occurred among healthy adults in the normative sample.

Post-Traumatic Stress Disorder Symptoms Are Related to Cognition after Complicated Mild and Moderate Traumatic Brain Injury but Not Severe and Penetrating Traumatic Brain Injury

Although post-traumatic stress disorder (PTSD) has been associated with worse cognitive outcomes after mild traumatic brain injury (TBI), its impact has not been evaluated after more severe TBI. This study aimed to determine whether PTSD symptoms are related to cognition after complicated mild, moderate, severe, and penetrating TBI. Service members (n = 137) with a history of complicated mild/moderate TBI (n = 64) or severe/penetrating TBI (n = 73) were prospectively enrolled from United States Military Treatment Facilities. Participants completed a neuropsychological assessment one year or more post-injury. Six neuropsychological composite scores and an overall test battery mean (OTBM) were considered. Participants were excluded if there was evidence of invalid responding. Hierarchical linear regressions were conducted evaluating neuropsychological performance. The interaction between TBI severity and PTSD Checklist-Civilian version total score was significant for processing speed (β = 0.208, p = 0.034) and delayed memory (β = 0.239, p = 0.021) and trended toward significance for immediate memory (β = 0.190, p = 0.057) and the OTBM (β = 0.181, p = 0.063). For each of these composite scores, the relationship between PTSD symptoms and cognition was stronger in the complicated mild/moderate TBI group than the severe/penetrating TBI group. Within the severe/penetrating TBI group, PTSD symptoms were unrelated to cognitive performance. In contrast, within the complicated mild/moderate TBI group, PTSD symptoms were significantly related to processing speed (R²Δ = 0.077, β = -0.280, p = 0.019), immediate memory (R²Δ = 0.197, β = -0.448, p < 0.001), delayed memory (R²Δ = 0.176, β = -0.423, p < 0.001), executive functioning (R²Δ = 0.100, β = -0.317, p = 0.008), and the OTBM (R²Δ = 0.162, β = -0.405, p < 0.001). The potential impact of PTSD symptoms on cognition, over and above the impact of brain injury alone, should be considered with service members and veterans with a history of complicated mild/moderate TBI. In addition, in research comparing cognitive outcomes between patients with histories of complicated-mild, moderate, severe, and/or penetrating TBI, it will be important to account for PTSD symptoms.

Utility of the iPad NIH Toolbox Cognition Battery in a clinical trial of older adults

BACKGROUND

To demonstrate feasibility and utility of the iPad version of the NIH Toolbox Cognition Battery (NIHTB-CB) in a clinical trial of older adults.

METHODS

Fifty-one adults, aged 55 and older without dementia were tested twice on NIHTB-CB and more traditional paper-and-pencil neuropsychological measures after meal ingestion, with approximately a 4-week interval. We also compared performances at Time 1 and Time 2 for significant change. We also extracted the response times and errors for available NIHTB-CB subtests to determine subtle changes in performance.

RESULTS

Over the interval, improvement in fluid cognitive measures was noted at Time 2 (t = -3.07, p = 0.004), whereas crystallized measures were unchanged. Tests of fluid cognition negatively correlated with age, particularly for the second visit. Analysis of the average speed per item showed that, for two of the tests, speed increased at Time 2. Traditional neuropsychological tests correlated with many of the NIHTB-CB measures. Response times for all five timed tests decreased at Time 2, although only statistically significant for Picture Sequence and Picture Vocabulary.

CONCLUSIONS

The iPad version of the NIH Toolbox Cognition Battery appears to be an adequate measure to assess cognitive functioning in a clinical trial of older adults. Psychometric analyses suggest stability in measures of crystallized functioning, whereas measures of fluid abilities revealed improvements over the short time frame of the study. Response times and errors for individual tests revealed intriguing relationships that should be further evaluated to determine the utility in clinical sample analysis, as this could aid identification of subtle cognitive change over short periods. Additional studies with larger sample sizes will be helpful to understanding the reliability, sensitivity, and specificity of the NIHTB-CB sub-scores in older adults. In addition, further evaluations with clinical populations, including individuals with cognitive impairment, are warranted.

Assessment of Neuropsychological Function in Veterans With Blast-Related Mild Traumatic Brain Injury and Subconcussive Blast Exposure

Objective: The majority of combat-related head injuries are associated with blast exposure. While Veterans with mild traumatic brain injury (mTBI) report cognitive complaints and exhibit poorer neuropsychological performance, there is little evidence examining the effects of subconcussive blast exposure, which does not meet clinical symptom criteria for mTBI during the acute period following exposure. We compared chronic effects of combat-related blast mTBI and combat-related subconcussive blast exposure on neuropsychological performance in Veterans. Methods: Post-9/11 Veterans with combat-related subconcussive blast exposure (n = 33), combat-related blast mTBI (n = 26), and controls (n = 33) without combat-related blast exposure, completed neuropsychological assessments of intellectual and executive functioning, processing speed, and working memory via NIH toolbox, assessment of clinical psychopathology, a retrospective account of blast exposures and non-blast-related head injuries, and self-reported current medication. Huber Robust Regressions were employed to compare neuropsychological performance across groups. Results: Veterans with combat-related blast mTBI and subconcussive blast exposure displayed significantly slower processing speed compared with controls. After adjusting for post-traumatic stress disorder and depressive symptoms, those with combat-related mTBI exhibited slower processing speed than controls. Conclusion: Veterans in the combat-related blast mTBI group exhibited slower processing speed relative to controls even when controlling for PTSD and depression. Cognition did not significantly differ between subconcussive and control groups or subconcussive and combat-related blast mTBI groups. Results suggest neurocognitive assessment may not be sensitive enough to detect long-term effects of subconcussive blast exposure, or that psychiatric symptoms may better account for cognitive sequelae following combat-related subconcussive blast exposure or combat-related blast mTBI.