9 - Exploring the Impact of a Service Dog Training Program Intervention on Neurobehavioral Symptoms for those with and without a History of Traumatic Brain Injury

Abstract Text:

Background:
Since 2000, approximately 463,000 United States military service members have been documented as experiencing a traumatic brain injury (TBI).1 TBI has been associated with negative short- and long-term outcomes such as an increased risk of neurological dysfunction.2-4 Emerging research has found an association between animal assisted therapy and improved psychological outcomes for individuals with post-traumatic stress disorder (PTSD), often comorbid with TBI.5-7 The objective of this study was to determine the effect of a service-dog training program (SDTP) on Neurobehavioral Symptom Inventory (NSI) scores in those with and without a history of TBI participating in the Big Dog study.

Methods:
This study enrolled participants for 22 weeks, with baseline NSI scores obtained during weeks 1 through 4 (prior to intervention), followed by weekly scores between weeks 5 through 10 (during intervention), and one final post-assessment follow-up at week 22. To be eligible for NSI analysis, participants had to have at least one baseline and one follow-up NSI assessment. Means, standard deviations, frequencies, and proportions described demographic and study characteristics. NSI scores from week 1 through 4 were averaged to obtain a single baseline score due to missing data. Wilcoxon signed-rank test with Bonferroni correction calculated pairwise comparisons of NSI scores over time. Hedges g calculated between overall effects and Cohen’s D calculated within TBI group effects of the intervention on NSI scores over time. Linear mixed models examined NSI trends over time.

Results:
There were 162 subjects enrolled out of 177 screened for study participation; 22 participants did not participate after enrolling and a further 18 withdrew consent or were lost-to-follow up prior to the intervention period. Of the remaining 118 participants, 115 had baseline NSI scores for evaluation. Participants were, on average, 37.9 (SD: 11.5) years old, active duty military (76%), male (59%), white (57%), married (50%), employed (83%), had a dog at home (57%). Over half the participants (60%) had a history of TBI and most (83.5%) screened positive for PTSD on the baseline Post-Traumatic Stress Disorder Checklist-5 (score of 30 or greater). Pairwise comparisons found a significant difference in NSI scores from baseline to week 9 of the study (p < 0.001) overall. No other intervention time points were found to be significantly different from baseline scores, even on stratifying for history of TBI. The effect of the intervention was found to be small from baseline to week 5 (g = 0.26, 95% CI: 0.06-0.47), week 6 (g = 0.21, 95% CI: 0.03-0.41), week 8 (g = 0.23, 95% CI: 0.02-0.51), and week 9 (g = 0.24, 95% CI: 0.02-0.60). Among those with a history of TBI, small effect sizes were found from baseline to week 5 (D = 0.29, 95 %CI: 0.03-0.57) and week 8 (D = 0.23, 95% CI: -0.05-0.61). Among those without a history of TBI, small effect sizes were found from baseline to week 5 (D = 0.20, 95% CI: -0.11-0.47), week 6 (D = 0.27, 95% CI: -0.03-0.64), week 7 (D = 0.21, 95% CI: -0.09-0.54), week 8 (D = 0.23, 95% CI: -0.09-0.60), and week 9 (D = 0.44, 95% CI: 0.14-0.80). When omitting week 22 follow-up data there was a significant 0.31 point decrease (p = 0.002) in NSI per each increase in weekly study intervention. When including all week 22 data, there was a significant 0.38 point decrease (p = 0.002) in NSI score per each increase in weekly study intervention. No significant association with TBI history was observed.

Conclusions:
This study found a modest, but significant decrease in NSI scores over the course of the Big Dog study, though no significant differences were found among TBI history. This may be due to a smaller sample size than expected at each intervention time point, in part related to the impact of COVID-19 on study interventions. Next steps in this study would be to determine the potential impact, if any, on NSI scores for those with varying levels of PTSD. Further, exploration of the subscales of the NSI should be conducted to determine any impact of a SDTP on individual symptoms scores across time.

Keywords: Animal Assisted Therapy, Post-traumatic Stress Disorder, Service Members, Big Dog, Rehabilitation