Associations among pain, PTSD, mTBI, and heart rate variability in veterans of Operation Enduring and Iraqi Freedom: a pilot study.

OBJECTIVE The objective of the study was to determine if there is dysregulated autonomic nervous system activity as manifested by depressed heart rate variability (HRV) among veterans of Operations Enduring and Iraqi Freedom (OEF/OIF). PARTICIPANTS AND SETTING The study used a convenience sample of OEF/OIF veterans (n = 28) seen at a Level II Polytrauma Network Site at the Michael E. DeBakey VA Medical Center. Participants were similar to other OEF/OIF veterans who received care at this site. DESIGN Cross sectional study. MEASURES Time domain analysis (standard deviation of beat-to-beat intervals [SDNN]) of HRV, diagnoses of mild traumatic brain injury and post-traumatic stress disorder (PTSD), and pain ratings from medical records. RESULTS As a group, the sample evidenced markedly depressed HRV (as reflected by SDNN) as compared with available age and gender corrected normative data. Pain (71%), PTSD (57%), and mild traumatic brain injury (mTBI) (64%) were prevalent. Thirty-six percent had all three measures (P3). Pain and P3 were significantly and negatively associated with SDNN (r = -0.460, P = 0.014; r = -0.373, P = 0.05, respectively). CONCLUSIONS These preliminary findings support the high prevalence of depressed HRV and P3 among veterans seen in a level II Polytrauma Center. The findings also suggest a possible synergistic effect of pain, PTSD, and mTBI on depressed HRV. The nature and implications of these relationships require additional research to elucidate.