Author + information
- Received November 19, 2012
- Revision received March 4, 2013
- Accepted April 16, 2013
- Published online September 10, 2013.
- Viola Vaccarino, MD, PhD∗,†∗ (, )
- Jack Goldberg, PhD‡,
- Cherie Rooks, PhD∗,
- Amit J. Shah, MD, MSCR†,
- Emir Veledar, PhD†,
- Tracy L. Faber, PhD§,
- John R. Votaw, PhD§,
- Christopher W. Forsberg, MS‡ and
- J. Douglas Bremner, MD‖
- ∗Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia
- †Division of Cardiology, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia
- ‡Vietnam Era Twin Registry, Seattle VA Epidemiology Research and Information Center and Department of Epidemiology, University of Washington, Seattle, Washington
- §Department of Radiology, Emory University School of Medicine, Atlanta, Georgia
- ‖Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia
- ↵∗Reprint requests and correspondence:
Dr. Viola Vaccarino, Department of Epidemiology, Emory University, 1518 Clifton Road, Room 3011, Atlanta, Georgia 30322.
Objectives The aim of this study was to determine whether post-traumatic stress disorder (PTSD) is associated with coronary heart disease (CHD) using a prospective twin study design and objective measures of CHD.
Background It has long been hypothesized that PTSD increases the risk of CHD, but empirical evidence using objective measures is limited.
Methods We conducted a prospective study of middle-aged male twins from the Vietnam Era Twin Registry. Among twin pairs without self-reported CHD at baseline, we selected pairs discordant for a lifetime history of PTSD, pairs discordant for a lifetime history of major depression, and pairs without either condition. All underwent a clinic visit after a median follow-up of 13 years. Outcomes included clinical events (myocardial infarction, other hospitalizations for CHD and coronary revascularization) and quantitative measures of myocardial perfusion by [13N] ammonia positron emission tomography, including a stress total severity score and coronary flow reserve.
Results A total of 562 twins (281 pairs) with a mean age of 42.6 years at baseline were included in this study. The incidence of CHD was more than double in twins with PTSD (22.6%) than in those without PTSD (8.9%; p < 0.001). The association remained robust after adjusting for lifestyle factors, other risk factors for CHD, and major depression (odds ratio: 2.2; 95% confidence interval: 1.2 to 4.1). Stress total severity score was significantly higher (+95%, p = 0.001) and coronary flow reserve was lower (−0.21, p = 0.02) in twins with PTSD than in those without PTSD, denoting worse myocardial perfusion. Associations were only mildly attenuated in 117 twin pairs discordant for PTSD.
Conclusions Among Vietnam-era veterans, PTSD is a risk factor for CHD.
Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by a persistent maladaptive reaction to exposure to severe psychological stress (1). In the general population, the lifetime prevalence of PTSD is 10% to 12% in women and 5% to 6% in men (2). Military personnel exposed to combat are especially affected by PTSD. The lifetime prevalence of PTSD in veterans who served in Southeast Asia during the Vietnam War is 15% to 19%, and many continue to have PTSD decades after the war (3). PTSD is even more prevalent in service members from the recent Iraq and Afghanistan conflicts (4).
A characteristic of PTSD is enhanced sympathetic nervous system response with trauma-reminiscent stimuli coupled with chronic dysregulation of the hypothalamic-pituitary-adrenal axis (5). These biological perturbations could affect the cardiovascular system. Indeed, a wealth of studies have documented many physical health problems in patients with PTSD, especially cardiovascular symptoms (6). However, a major limitation of many studies is a cross-sectional design, which limits the ability to demonstrate a temporal relationship between PTSD and coronary heart disease (CHD). The few longitudinal studies performed have examined symptoms of PTSD rather than a diagnosis of PTSD (7,8) or have relied on death certificate codes (7,9,10) or administrative records (11–13) for definition of outcomes. Most studies were also based on self-reported symptoms of CHD rather than objective measures (7,14–19). Finally, not all studies have found an increased cardiovascular risk with PTSD (14,17,20) or military trauma exposure (21–23). As a result, the long-term effects of PTSD on the risk of CHD remain unclear.
The main objective of this study was to clarify the relationship between PTSD and CHD using a prospective co-twin study design and objective measures of CHD by clinical history and positron emission tomography (PET) myocardial perfusion imaging.
The VET (Vietnam Era Twin) registry is a national sample of male monozygotic and dizygotic twins from all military branches who served on active duty during the Vietnam era (1964 to 1975). The methods of construction have been described in detail (24). The present study is based on a follow-up of subgroups of VET Registry twin pairs selected based on their PTSD and major depression status as part of the Emory Twin Studies (25,26). We selected twin pairs born between 1946 and 1956 in which at least one member had PTSD or depression as well as twin pairs in which both members were free of PTSD and depression. We excluded pairs in which at least one member reported a previous history of cardiovascular diseases and those with contraindications to PET with adenosine stress as previously described (25). Zygosity was obtained by DNA typing.
Demographics and Other Baseline Factors
Data on demographics and military service were obtained from military records. Detailed sociodemographic information as well as information on combat exposure, previous history of CHD, risk factors for CHD, and medications were obtained through a series of registry-wide surveys conducted between 1987 and 1992 (24,27).
Assessment of PTSD and Other Psychiatric Diagnoses
Our primary measure of PTSD was a diagnosis of PTSD based on the Diagnostic Interview Schedule (DIS) for psychiatric disorders according to the Diagnostic and Statistical Manual of Mental Disorders-Third Edition-Revised (DSM-III-R) criteria, which was administered in 1992. Surveys were conducted using trained interviewers and a computer-assisted telephone version of the DIS. For 19 twins, a DIS diagnosis of PTSD was missing, and it was imputed based on a calculated Mississippi scale score of 80 or greater (28). A 15-item PTSD symptom scale according to the DSM-III-R diagnostic criteria was also obtained in 1987. This scale has high internal consistency and acceptable reliability (27). A 2010 to 2011 VET Registry survey found a high correlation (r = 0.90) between the 15-item PTSD symptom scale and the more contemporary 17-item PTSD checklist based on the Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (N. Smith, unpublished data, January 2011). The 1992 DIS allowed assessment of other psychiatric diagnoses, including major depression and alcohol and drug abuse and dependence.
After a median follow-up of 13 years, the selected twin pairs underwent an in-person clinic visit between 2002 and 2010, including a detailed medical history, physical examination, and review of current medications by a research nurse or physician assistant. Anthropometric measurements, blood samples, and behavioral questionnaires for measurement of risk factors for CHD were obtained (25,26). All assessments were performed blindly with respect to PTSD status.
Incidence of cardiovascular diseases
Symptomatic CHD was defined as having had a prior myocardial infarction or any other overnight hospitalization for CHD, based on typical signs and symptoms of acute coronary syndromes (unstable angina or acute myocardial infarction), or having undergone coronary revascularization procedures (coronary bypass surgery or percutaneous coronary angioplasty). We also collected information on cerebrovascular accidents, including strokes and transient ischemic attacks.
Myocardial perfusion measurements
Twins underwent myocardial perfusion imaging with [13N]ammonia PET at rest and following pharmacological (adenosine) stress during a single imaging session as previously described (25). All twins were admitted overnight to the research facility on the day before the PET scan. They were instructed to abstain from smoking and from drinking alcoholic or caffeinated beverages, and all medications were held the morning of the PET scan.
Myocardial perfusion was quantified by means of the Emory Cardiac Toolbox (Syntermed Inc., Atlanta, Georgia), a computer technique that provides objective (operator-independent) quantitative assessment of perfusion with established validity and reproducibility (29). Briefly, the 3-dimensional tracer uptake distribution in the left ventricular chamber was synthesized onto a 2-dimensional polar map. A stress total severity score (STSS) was computed according to published methodology (30). Moreover, we examined the percentage of subjects with an STSS of 100 or greater, which is associated with approximately a 10% decrease in event-free survival at 2 years in patients with established coronary artery disease (31).
We also performed myocardial blood flow quantitation for the assessment of coronary flow reserve (CFR), an index of coronary vasodilator capacity that is a useful measure of coronary microvascular function (32). To calculate CFR, measurements of myocardial blood flow at rest and during adenosine hyperemia were obtained as previously described (25). Our main outcome was the overall measure of CFR for the entire myocardium (across all 20 regions), defined as the ratio of maximum flow during stress to flow at rest. We also examined abnormal CFR, defined as a CFR <2.0, which has prognostic significance (33). This research was approved by the Emory Institutional Review Board, and all twins provided signed informed consent.
SAS software version 9.2 (SAS Institute Inc., Cary, North Carolina) was used for statistical analysis. To assess possible response bias, we compared baseline characteristics between eligible twins who did and did not participate in our study. We also examined whether mortality differed according to PTSD status over the follow-up period in participants compared with nonparticipants. We used generalized estimating equation models for categorical variables (such as incidence of CHD) and mixed effects models for continuous variables (such as STSS and CFR) with a random intercept for each pair (34). Because STSS was not normally distributed, it was log transformed; results are presented as geometric means and percent differences. We fitted a series of sequential models that adjusted for the following a priori chosen baseline factors: sociodemographics (age, education, income); service in Southeast Asia; lifestyle and CHD risk factors (smoking, alcohol consumption, physical activity, hypertension); major depression; and alcohol and drug abuse or dependence. Each model retained all variables in previous models. The interaction between PTSD and major depression was tested, and risk factors for CHD at follow-up were also examined. For analysis of CFR, we further adjusted for perfusion abnormalities (STSS). Analyses were repeated for a 3-level classification of PTSD, including a “subthreshold” category, defined as meeting both the A (exposure to traumatic stress) and B (re-experiencing) criteria for PTSD and either the C (avoidance and numbing) or D (increased arousal) criteria. Analyses were further repeated for quartiles of the PTSD symptom scale score.
Next, we compared twins discordant for PTSD. The within-pair effects are inherently controlled for demographic, shared familial, and early environmental influences; in addition, daily activities and other environmental factors during the examination day were controlled by design because twin pairs were examined together. Monozygotic pairs share 100% of their genetic material in addition to early environment; thus, any association within monozygotic pairs cannot be ascribed to genes or early shared environment. Dizygotic twin pairs share familial factors but on average only share 50% of their genetic material. Therefore, comparison of the effect size between the individual-level analysis and the discordant-pair analysis of monozygotic and dizygotic twins provides information on whether genetic or other familial or shared environmental confounding is present (35).
Overall, 307 twin pairs were recruited and tested between 2002 and 2010. The response rate was similar in the PTSD-discordant twin pairs (127 of 318 twin pairs, 40%), in the depression-discordant twin pairs (93 of 201 twin pairs, 46%), and the control pairs (87 of 229 twin pairs, 38%). There were no differences in demographic characteristics, military variables, and risk factors for CHD between participant and nonparticipant twins. There was also no evidence of differential mortality in participants and nonparticipants. In the approximately 10 years between assessment of PTSD in 1992 and the start of recruitment in our study in 2002, there were only 43 otherwise eligible twin pairs in which one or both twins had died, and deaths were not associated with PTSD (3.1% vs. 2.3%, p = 0.31). Over the entire period between 1992 and 2009 (the last year mortality was updated in the VET Registry through death certificates), PTSD tended to be associated with total and cardiovascular mortality, but the association was similar in participants and nonparticipants. Among participants, the relative risk comparing those with and without PTSD was 1.8 (p = 0.19) for total mortality and 1.6 (p = 0.55) for cardiovascular mortality; among nonparticipants, the corresponding relative risks were 1.8 (p = 0.001) and 1.8 (p = 0.10).
After eliminating the second visit of 26 twin pairs with repeated assessments, our sample included 562 twins or 281 twin pairs (170 monozygotic and 111 dizygotic pairs). Of these, 137 subjects met the criteria for PTSD at baseline, and 117 twin pairs (77 monozygotic and 40 dizygotic) were discordant for PTSD. Approximately one-half of the sample served in Southeast Asia. Twins with PTSD were more likely to smoke, to drink alcohol, and to have a history of hypertension, but there were no differences in other risk factors such as body mass index and diabetes (Table 1). Twins with PTSD were also more likely to have a diagnosis of major depression and of alcohol and drug abuse.
Incidence of cardiovascular diseases
In total, 69 twins developed CHD during follow-up. As shown in Figure 1, the incidence of CHD was more than double in twins with PTSD (22.6%) than in those without PTSD (8.9%). This difference held for the subcategories of acute myocardial infarction (n = 31), other hospitalizations for CHD (n = 20), and revascularization procedures (n = 39) (all p < 0.05). The association between PTSD and the incidence of CHD remained robust after adjusting for sociodemographic factors, service in Southeast Asia, lifestyle and other CHD risk factors, major depression, and other psychiatric diagnoses (Table 2). In the fully adjusted model, the odds ratio (OR) was 2.1 (95% confidence interval [CI]: 1.1 to 3.9).
Only 18 twins reported cerebrovascular accident events during follow-up. These events were approximately twice as common in twins with PTSD (5.1%) than in those without PTSD (2.5%), but the difference did not reach statistical significance (p = 0.14).
PET myocardial perfusion imaging
PET myocardial perfusion data and CFR could not be obtained in some twins. Overall, 479 twins (116 with PTSD) were included in the STSS analysis and 416 (92 with PTSD) were included in the CFR analysis.
The STSS was 95% higher in twins with PTSD than in those without (p = 0.001), denoting more perfusion defects (Table 3). An STSS of at least 100 was found in 59.5% of twins with PTSD versus 38.6% of twins without PTSD (OR: 2.0; 95% CI: 1.3 to 3.1; p = 0.001). The extent of hypoperfusion expressed as percent of the left ventricle affected was also significantly higher in twins with PTSD than in those without (p = 0.001). Forty-two percent of twins with PTSD had an extent of hypoperfusion >10% of the left ventricular mass versus 26% of twins without PTSD (OR: 1.9; 95% CI: 1.2 to 2.8; p = 0.003). Multivariable analysis did not substantially affect the relationship between STSS and PTSD (Table 3).
Overall, CFR was significantly lower in twins with PTSD than in those without PTSD (absolute difference: −0.21; p = 0.02) (Table 4). The reduction in CFR was primarily due to lower myocardial blood flow during pharmacological stress in twins with PTSD than in those without (148 vs. 160 ml/min/g, p = 0.01), while myocardial blood flow at rest was not different (67.8 vs. 66.6 ml/min/g, p = 0.46). Adjustment for sociodemographic factors and service in Southeast Asia did not substantially alter the results, but further adjustment for lifestyle factors weakened the association. Adjustment for STSS did not materially alter the difference in CFR due to PTSD (2.29 vs. 2.51; absolute difference: −0.22), suggesting that the microvascular circulation was involved. An abnormal CFR, defined as <2.0, was also more frequent in twins with PTSD (43.5%) than in those without (24.7%, p < 0.001).
As shown in Table 5, the odds of CHD were 90% higher in twins with PTSD than their brothers without PTSD (22.2% vs. 12.8%, p = 0.04). Additionally, twins with PTSD had an STSS that was 72% higher (p = 0.02) and a CFR that was 0.22 points lower (p = 0.03) when compared with their brothers without PTSD. Adjusting for service in Southeast Asia, lifestyle and CHD risk factors and other psychiatric diagnoses did not diminish the association for incidence of CHD and STSS, although the association for CFR was attenuated and no longer significant. Results were similar in monozygotic and dizygotic twin pairs.
The interaction between PTSD and major depression was tested for all CHD outcomes and was not statistically significant. When analyses were repeated after excluding the 19 twins with a missing DIS diagnosis of PTSD who had their PTSD imputed based on symptoms of PTSD, the results were virtually identical. Specifically, among twins with a complete DIS diagnosis of PTSD, the incidence of CHD was 22.2% in twins with PTSD and 8.6% in those without PTSD (OR: 3.1; p < 0.001); STSSs were 59.3 and 30.8 (p = 0.002) and CFR values were 2.33 and 2.51 (p = 0.04), respectively.
When analyses were conducted according to a 3-level classification of PTSD, including no PTSD (n = 210), subthreshold PTSD (n = 207), and PTSD (n = 126), only PTSD, and not subthreshold PTSD, was associated with a higher risk of CHD compared with the group without PTSD (Fig. 2). However, when analyses were conducted using quartiles of the PTSD symptom scale score, a graded association of increasing risk of CHD with increasing PTSD symptom quartiles was found for both diagnosis of CHD and STSS (Fig. 3). For incidence of CHD, but not for STSS, adjustment for service in Southeast Asia as well as lifestyle and CHD risk factors diminished this trend; additional adjustment for other psychiatric diagnoses further reduced the OR of CHD for the fourth quartile of PTSD.
At the end of the follow-up period, twins with PTSD at baseline continued to show adverse lifestyle behaviors such as current smoking (37.2% vs. 21.6%), alcohol consumption (a mean of 6.4 vs. 4.6 drinks/day), and sedentary behavior (Baecke physical activity score of 6.9 vs. 7.3). However, there were no differences in other traditional risk factors for CHD such as blood pressure, history of hypertension, history of diabetes mellitus, and body mass index. The low-density lipoprotein cholesterol level was significantly lower in twins with PTSD (116.6 mg/dl) than in those without PTSD (122.3 mg/dl). There were also no differences in the use of cardiovascular medications, including beta-blockers, statins, and aspirin.
In this study of middle-aged Vietnam-era veteran twins, we found that PTSD was associated with greater than twice the risk of CHD over a median follow-up of 13 years. This association held for a clinical diagnosis of CHD as well as for objective quantitative measures of myocardial perfusion using cardiac PET. Except for CFR, the associations remained robust after adjusting for risk factors for CHD at baseline and were independent of major depression. Additionally, the estimates were only modestly reduced when comparing twins discordant for PTSD, who are matched for sociodemographic, early environment, and, in the monozygotic twins, genetic factors.
Our study is the first investigation linking PTSD to CHD using objective measures of myocardial perfusion in addition to a clinical diagnosis of CHD. Using a co-twin design and both clinical and imaging endpoints, our study clarifies inconsistent results in previous research. The co-twin design also controls for unmeasured genetic and familial confounders that could be shared between PTSD and cardiovascular diseases.
The mechanisms underlying the link between PTSD and CHD have yet to be clarified, but alterations in the central and autonomic nervous system and neuroendocrine dysregulation are believed to play a role (1,5). Patients with PTSD exhibit higher catecholamine levels and higher heart rate and other physiological parameters compared with controls, particularly after exposure to traumatic reminders such as the sound of gunfire and combat slides (1,36). Repeated sympathetic system responses to traumatic reminders could lead to hemodynamic hyperactivity during everyday life, which may eventually affect cardiovascular health. They could also affect myocardial electrical stability and the risk of cardiac arrhythmias (37) and could contribute to reduced heart rate variability and baroreflex function, which are important risk factors for cardiac events (38). Although chronic perturbations in the hypothalamic-pituitary-adrenal axis could theoretically increase the risk of CHD by enhancing metabolic risk factors, we found little evidence of this in our data. There was no association between PTSD and metabolic risk factors at baseline except for a higher rate of self-reported hypertension. Notably, PTSD was also unrelated to measured metabolic risk factors at follow-up.
PTSD may also influence the risk of CHD through lifestyle factors. As expected, adverse lifestyle behaviors were more common in twins with PTSD than in those without PTSD. However, adjusting for these factors generally accounted for a small portion of the relationship between PTSD and CHD outcomes except CFR. The impact on CFR may reflect the established effect of cardiovascular risk factors, particularly smoking, on coronary vasodilator capacity even in the short-term and in the absence of obstructive coronary stenosis (32).
The associations persisted when comparing twins discordant for PTSD, although the estimates were slightly reduced. This indicates that, to some extent, the relationship is due to familial influences or other early environmental confounding factors shared by the twins. However, even within pairs, twins with PTSD had a higher incidence of CHD, a more compromised myocardial perfusion, and a lower CFR compared with their brothers without PTSD. Thus, the basis of the association between PTSD and CHD does not involve confounding by familial and other shared environmental factors.
The differences in imaging endpoints based on PTSD in this study are clinically meaningful. The extent and severity of myocardial hypoperfusion using operator-independent measures carries substantial prognostic value both in persons with and without coronary artery disease (31). Compared with twins without PTSD, those with PTSD had twice the odds of an STSS of 100 or greater, which is associated with approximately a 10% decrease in event-free survival in cardiac patients (31). They also had 90% higher odds of hypoperfusion affecting more than 10% of the left ventricle. The CFR was significantly reduced, and a clinically abnormal CFR (<2.0) was 80% more common in twins with PTSD than in those without PTSD.
Our study required participants to travel for an in-person examination, and our rate of participation was modest. It is possible that twins who elected to participate were systematically different from those who did not. However, responders and nonresponders were quite similar in their distribution of risk factors, and therefore bias due to nonresponse is unlikely. In addition, our within-pair results of PTSD-discordant twin pairs are free of this potential bias, because both twins participated. The use of the DIS in assessing PTSD has limitations, as do all semistructured instruments. According to a reanalysis of PTSD in Vietnam veterans, however, the DIS produces estimates of the prevalence of PTSD that are similar to those of other instruments (39). We had no access to participants' medical records to validate clinical endpoints, because this information is not routinely collected by the VET Registry. However, clinical endpoints were assessed at the in-person examination by clinical personnel. Misclassification of CHD events is low when self-reported history is compared with medical record review (40). It is anticipated that such misclassification is even lower when information is collected by clinicians during health examinations rather than by self-report. Indeed, data gathered during health examinations has often been used as the gold standard (41,42). An additional limitation is that we did not have PET data at baseline. Nonetheless, our PET results corroborate the results of the incidence of CHD. Our sample was all male and predominantly non-Hispanic white; therefore, our findings should be generalized with caution to other demographic groups. However, our study has the advantage of a prospective design and objective measures of CHD using cardiac imaging. In addition, the twin sample offers the unique advantage of controlling for potentially unmeasured confounding familial factors that may affect both the risk of PTSD and the risk of CHD.
Among Vietnam-era veterans, PTSD is associated with an increased risk of CHD, confirmed with quantitative measures of coronary perfusion and myocardial blood flow. This increased risk is not due to a higher rate of established risk factors for CHD. It is also not explained by adverse health behaviors such as smoking and alcohol consumption or by familial risk factors shared by PTSD and CHD. Future studies should address the mechanisms underlying the increased cardiovascular risk in persons with PTSD, because this information will help guide effective prevention and treatment strategies aimed at reducing cardiovascular morbidity and mortality in persons with PTSD.
Numerous organizations have provided invaluable assistance, including the VA Cooperative Study Program; Department of Defense; National Personnel Records Center, National Archives and Records Administration; Internal Revenue Service; National Institutes of Health; National Opinion Research Center; National Research Council, National Academy of Sciences; and Institute for Survey Research, Temple University. The authors acknowledge the continued cooperation and participation of the members of the Vietnam Era Twin Registry and their families and thank the tireless staff at Emory University.
This work was supported by grants from the National Institutes of Health (K24HL077506, R01 HL68630, R01 AG026255, K24 MH076955, R21HL093665-01A1S1), the American Heart Association (0245115N), the National Center for Advancing Translational Sciences of the National Institutes of Health (UL1TR000454), and the Emory University General Clinical Research Center (MO1-RR00039). The sponsors of this study had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript. The U.S. Department of Veterans Affairs has provided financial support for the development and maintenance of the Vietnam Era Twin (VET) Registry. Dr. Faber is deceased. Dr. Faber was a consultant and shareholder and received royalties from Syntermed Inc., which licenses the Emory Cardiac Toolbox that was used for some analyses in this study. All other authors have reported that they have no relationships relevant to the content of this paper to disclose.
- Abbreviations and Acronyms
- coronary flow reserve
- coronary heart disease
- confidence interval
- Diagnostic Interview Schedule
- Diagnostic and Statistical Manual of Mental Disorders-Third Edition-Revised
- odds ratio
- positron emission tomography
- post-traumatic stress disorder
- stress total severity score
- Received November 19, 2012.
- Revision received March 4, 2013.
- Accepted April 16, 2013.
- American College of Cardiology Foundation
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