B-53 Inefficient Clock-Checking is Associated with Reduced Prospective Memory Performance in Veterans with Blast-Related Mild Traumatic Brain Injury

Objective We investigated whether clock-checking frequency during a prospective memory (PM) task differed between Veterans with reported histories of blast-related mild traumatic brain injury (mTBI) and Veteran Controls (VCs) without a history mTBI. We hypothesized that, compared to controls, the mTBI group would less frequently clock check. Additionally, we expected that reduced clock-checking would contribute to poorer time-based PM performance in the mTBI group. Method Twenty-seven Veterans (9 mTBI and 18 VC) with sufficient effort testing completed a structured TBI history interview, the Post-Traumatic Stress Disorder Checklist (PCL) and the Memory for Intentions Test (MIST) as a PM task. During MIST administration, examiners recorded clock-checking behavior each time a participant physically turned a digital clock to observe the current time. Results Compared to VCs, the mTBI group performed worse on the Time subscale of the MIST [Mean (SD) VC = 6.7 (1.1), mTBI = 5.7 (1.1), p < .05], and demonstrated significantly fewer clock-checks over the duration of the test [VC = 14.2(4.7), mTBI = 10.2 (3.4), p < .05]. Clock-checking significantly correlated with MIST Time subscale performance (r = .38, p < .05). Groups did not significantly differ in PCL scores, and PCL scores did not significantly correlate with clock-checking counts. Conclusion Our preliminary results are the first to show that clock-checking behavior may contribute to reduced performance on time-based PM tasks in Veterans with histories of mTBI. Specifically, our findings demonstrate that participants with mTBI employ an inefficient time monitoring strategy wherein infrequent clock checking contributes to poorer test performance. These findings suggest that strategies to improve clock checking may improve PM performance.