Abstract MP69: Effect of Post Traumatic Stress Disorder and Combat Exposure on Carotid Intima-Media Thickness in Vietnam Era Veteran Twins

Abstract

Introduction: Posttraumatic stress disorder (PTSD) is associated with an increased risk of ischemic heart disease, but the pathophysiologic mechanisms remains unclear. Genetic and shared familial and early environmental factors may confound this association. Carotid artery intima media thickness (cIMT) is a measure of atherosclerotic burden and is predictive of future cardiovascular events. In a study of Vietnam era twins, we assessed the hypothesis that PTSD and combat exposure are associated with cIMT after controlling for shared genetic and childhood environmental factors. Methods: We studied 465 middle-aged male twins from the Vietnam Era Twin Registry, who were part of the Emory Twin Studies, without a clinical history of cardiovascular disease. A diagnosis of PTSD was obtained with the Structured Clinical Interview for DSM-IV and combat exposure was measured using the Combat Exposure Scale. Carotid IMT was measured using B-mode ultrasound. Mixed effects regression models with a random effect for the twin pair were used to examine overall, between- and within-pair effects. Models were sequentially adjusting for traditional CVD risk factors, genetic and childhood environmental factors. Results: About 13% (60 out of 465) of participants met criteria for PTSD and 45% (209 out of 465) served in the Vietnam Theater. When twins were examined as individuals, PTSD was associated with 33.3 μm higher cIMT (p=0.03) after adjustment for potential confounders. In addition, the average cIMT for the twin pair increased by 43 μm for each additional twin affected by PTSD in the pair (p=0.04). However, there was no significant within-pair difference in cIMT comparing co-twins discordant for PTSD. Combat exposure showed a similar pattern of results but its association with cIMT weakened after adjusting for PTSD (unadjusted p=0.01, adjusted p=0.08). Conclusions: Among Vietnam era veterans, combat exposure and PTSD are both associated with cIMT, but such associations are largely mediated by shared familial or early environmental factors.