Depressive symptoms and heart rate variability: evidence for a shared genetic substrate in a study of twins

Heart Rate Variability, Deceleration Capacity of Heart Rate, and Death: A Veteran Twins Study

BACKGROUND

Autonomic function can be measured noninvasively using heart rate variability (HRV), which indexes overall sympathovagal balance. Deceleration capacity (DC) of heart rate is a more specific metric of vagal modulation. Higher values of these measures have been associated with reduced mortality risk primarily in patients with cardiovascular disease, but their significance in community samples is less clear.

METHODS AND RESULTS

This prospective twin study followed 501 members from the VET (Vietnam Era Twin) registry. At baseline, frequency domain HRV and DC were measured from 24-hour Holter ECGs. During an average 12-year follow-up, all-cause death was assessed via the National Death Index. Multivariable Cox frailty models with random effect for twin pair were used to examine the hazard ratios of death per 1-SD increase in log-transformed autonomic metrics. Both in the overall sample and comparing twins within pairs, higher values of low-frequency HRV and DC were significantly associated with lower hazards of all-cause death. In within-pair analysis, after adjusting for baseline factors, there was a 22% and 27% lower hazard of death per 1-SD increment in low-frequency HRV and DC, respectively. Higher low-frequency HRV and DC, measured during both daytime and nighttime, were associated with decreased hazard of death, but daytime measures showed numerically stronger associations. Results did not substantially vary by zygosity.

CONCLUSIONS

Autonomic inflexibility, and especially vagal withdrawal, are important mechanistic pathways of general mortality risk, independent of familial and genetic factors.

A Pilot Study of Neurobiological Mechanisms of Stress and Cardiovascular Risk

Objective

Coronary heart disease is a leading cause of death and disability. Although psychological stress has been identified as an important potential contributor, mechanisms by which stress increases risk of heart disease and mortality are not fully understood. The purpose of this study was to assess mechanisms by which stress acts through the brain and heart to confer increased CHD risk.

Methods

Coronary Heart Disease patients (N=10) underwent cardiac imaging with [Tc-99m] sestamibi single photon emission tomography at rest and during a public speaking mental stress task. Patients returned for a second day and underwent positron emission tomography imaging of the brain, heart, bone marrow, aorta (indicating inflammation) and subcutaneous adipose tissue, after injection of [18F]2-fluoro-2-deoxyglucose for assessment of glucose uptake followed mental stress. Patients with (N=4) and without (N=6) mental stress-induced myocardial ischemia were compared for glucose uptake in brain, heart, adipose tissue and aorta with mental stress.

Results

Patients with mental stress-induced ischemia showed a pattern of increased uptake in the heart, medial prefrontal cortex, and adipose tissue with stress. In the heart disease group as a whole, activity increase with stress in the medial prefrontal brain and amygdala correlated with stress-induced increases in spleen (r=0.69, p=0.038; and r=0.69, p=0.04 respectfully). Stress-induced frontal lobe increased uptake correlated with stress-induced aorta uptake (r=0.71, p=0.016). Activity in insula and medial prefrontal cortex was correlated with post-stress activity in bone marrow and adipose tissue. Activity in other brain areas not implicated in stress did not show similar correlations. Increases in medial prefrontal activity with stress correlated with increased cardiac glucose uptake with stress, suggestive of myocardial ischemia (r=0.85, p=0.004).

Conclusions

These findings suggest a link between brain response to stress in key areas mediating emotion and peripheral organs involved in inflammation and hematopoietic activity, as well as myocardial ischemia, in Coronary Heart Disease patients.

Rethinking the risk for depression using the RDoC: A psychophysiological perspective

Considering that the classical categorical approach to mental disorders does not allow a clear identification of at-risk conditions, the dimensional approach provided by the Research Domain Criteria (RDoC) is useful in the exploration of vulnerability to psychopathology. In the RDoC era, psychophysiological models have an important role in the reconceptualization of mental disorders. Indeed, progress in the study of depression vulnerability has increasingly been informed by psychophysiological models. By adopting an RDoC lens, this narrative review focuses on how psychophysiological models can be used to advance our knowledge of the pathophysiological mechanisms underlying depression vulnerability. Findings from psychophysiological research that explored multiple RDoC domains in populations at-risk for depression are reviewed and discussed. Future directions for the application of psychophysiological research in reaching a more complete understanding of depression vulnerability and, ultimately, improving clinical utility, are presented.

Modulation of Heart and Brain Function by Surah Al-Rehman Recitation Among Distressed Diabetic Patients in Pakistan

Distress causes psychophysiological alterations that affect autonomic function. The current study explores psychophysiological modulation in diabetic distress in response to Surah Al-Rehman recitation. A single-group experimental study with before and after intervention assessments was conducted during April 2018 to February 2019 in which participants (n = 10) listened to Surah Al-Rehman recitation. Blood pressure, blood glucose, cortisol, ECG and EEG were recorded before and after recitation. Significant reduction in systolic blood pressure, increase in low frequency and absolute alpha power at Fp2 were observed. Heartbeat evoked potentials (HEP) were also significantly modulated at Fp1, Fp2 and F4. These findings suggest that Surah Al-Rehman modulated baroreflex activity thereby reducing sympathetic activity and improved heart brain coherence as reflected by HEP.

The temporal relationships between sleep disturbance and autonomic dysregulation: A co-twin control study

INTRODUCTION

Sleep disturbance is associated with autonomic dysregulation, but the temporal directionality of this relationship remains uncertain. The objective of this study was to evaluate the temporal relationships between objectively measured sleep disturbance and daytime or nighttime autonomic dysregulation in a co-twin control study.

METHODS

A total of 68 members (34 pairs) of the Vietnam Era Twin Registry were studied. Twins underwent 7-day in-home actigraphy to derive objective measures of sleep disturbance. Autonomic function indexed by heart rate variability (HRV) was obtained using 7-day ECG monitoring with a wearable patch. Multivariable vector autoregressive models with Granger causality tests were used to examine the temporal directionality of the association between daytime and nighttime HRV and sleep metrics, within twin pairs, using 7-day collected ECG data.

RESULTS

Twins were all male, mostly white (96%), with mean (SD) age of 69 (2) years. Higher daytime HRV across multiple domains was bidirectionally associated with longer total sleep time and lower wake after sleep onset; these temporal dynamics were extended to a window of 48 h. In contrast, there was no association between nighttime HRV and sleep measures in subsequent nights, or between sleep measures from previous nights and subsequent nighttime HRV.

CONCLUSIONS

Daytime, but not nighttime, autonomic function indexed by HRV has bidirectional associations with several sleep dimensions. Dysfunctions in autonomic regulation during wakefulness can lead to subsequent shorter sleep duration and worse sleep continuity, and vice versa, and their influence on each other may extend beyond 24 h.

Traditional and Emerging Sex-Specific Risk Factors for Cardiovascular Disease in Women

Cardiovascular disease (CVD) remains a major health threat in women. While traditional CVD risk factors such as hypertension, hyperlipidemia, diabetes, and smoking have been recognized for over 50 years, optimal control of these risk factors remains a major challenge. Unique sex-specific risk factors such as adverse pregnancy outcomes, premature menopause and low estrogen states, and chronic autoimmune inflammatory disorders also contribute to increased CVD risk in women. In addition, psychological risk factors such as stress, depression, and social determinants of health may have a disproportionately adverse impact in women. An improved understanding of traditional and emerging sex-specific CVD risk factors and management of modifiable factors is critical for clinicians who provide care for women. Early recognition and treatment of risk factors may alter the trajectory of adverse CVD events. A multi-disciplinary approach with team-based care involving multiple specialists and improved, targeted educational efforts are needed to reduce CVD risk factors and its adverse consequences in women.

Heart Rate Fractality Disruption as a Footprint of Subthreshold Depressive Symptoms in a Healthy Population

OBJECTIVE

Psychopathology (and depression in particular) is a cardiovascular risk factor independent from any co-occurring pathology. This link is traced back to the mind-heart-body connection, whose underlying mechanisms are still not completely known. To study psychopathology in relation to the heart, it is necessary to observe the autonomic nervous system, which mediates among the parts of that connection. Its gold standard of evaluation is the study of heart rate variability (HRV). To investigate whether any association exists between the HRV parameters and sub-threshold depressive symptoms in a sample of healthy subjects.

METHOD

In this cross-sectional study, two short-term HRV recordings (5 min - supine and sitting) have been analyzed in 77 healthy subjects. Here we adopted a three-fold approach to evaluate HRV: a set of scores belonging to the time domain; to the frequency domain (high, low, and very low frequencies) and a set of 'nonlinear' parameters. The PHQ-9 (Patient Health Questionnaire-9) scale was used to detect depressive symptoms.

RESULTS

Depressive symptoms were associated only with a parameter from the non-linear approach and specifically the long-term fluctuations of fractal dimensions (DFA-α2). This association remained significant even after controlling for age, gender, BMI (Body-Mass-Index), arterial hypertension, anti-hypertensive drugs, dyslipidemia, and smoking habits. Moreover, the DFA-α2 was not affected by the baroreflex (postural change), unlike other autonomic markers.

CONCLUSIONS

Fractal analysis of HRV (DFA-α2) allows then to predict depressive symptoms below the diagnostic threshold in healthy subjects regardless of their health status. DFA-α2 may be considered as an imprint of subclinical depression on the heart rhythm.

A Web-Based Cognitive Behavioral Therapy, Mindfulness Meditation, and Yoga Intervention for Posttraumatic Stress Disorder: Single-Arm Experimental Clinical Trial

BACKGROUND

Posttraumatic stress disorder (PTSD) is a debilitating, undertreated condition. The web-based delivery of cognitive behavioral therapy supplemented with mindfulness meditation and yoga is a viable treatment that emphasizes self-directed daily practice.

OBJECTIVE

This study aims to examine the effectiveness of a web-based cognitive behavioral therapy, mindfulness, and yoga (CBT-MY) program designed for daily use.

METHODS

We conducted an 8-week, single-arm, experimental, registered clinical trial on adults reporting PTSD symptoms (n=22; aged 18-35 years). Each participant received web-based CBT-MY content and an hour of web-based counseling each week. Pre-post outcomes included self-reported PTSD symptom severity, depression, anxiety, chronic pain, and mindfulness. Pre-post psychophysiological outcomes included peak pupil dilation (PPD) and heart rate variability (HRV). HRV and PPD were also compared with cross-sectional data from a non-PTSD comparison group without a history of clinical mental health diagnoses and CBT-MY exposure (n=46).

RESULTS

Pre-post intention-to-treat analyses revealed substantial improvements in PTSD severity (d=1.60), depression (d=0.83), anxiety (d=0.99), and mindfulness (d=0.88). Linear multilevel mixed models demonstrated a significant pre-post reduction in PPD (B=-0.06; SE=0.01; P<.001; d=0.90) but no significant pre-post change in HRV (P=.87). Overall, participants spent an average of 11.53 (SD 22.76) min/day on self-directed mindfulness practice.

CONCLUSIONS

Web-based CBT-MY was associated with clinically significant symptom reductions and significant PPD changes, suggesting healthier autonomic functioning. Future randomized controlled trials are needed to further examine the gains apparent in this single-arm study.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03684473; https://clinicaltrials.gov/ct2/show/NCT03684473.

DNA Methylation of TXNIP Independently Associated with Inflammation and Diabetes Mellitus in Twins

Thioredoxin-interacting protein (TXNIP) plays a key role in diabetes development and prognosis through its role in pancreatic β-cell dysfunction and death as well as in upregulating the inflammatory response in hyperglycemia. DNA methylation (DNAm) of TXNIP (TXNIP-cg19693031) is associated with the prevalence and incidence of type 2 diabetes (T2D); however, its role in inflammation and its relationship with T2D remain unclear. We aimed to investigate the epigenetic associations of TXNIP-cg19693031 with a panel of inflammatory biomarkers and to examine whether these inflammatory biomarkers modify the association between TXNIP-cg19693031 methylation and diabetes in 218 middle-aged male twins from the Emory Twin Study. We confirmed the association of TXNIP-cg19693031 DNAm with T2D, as well as with HbA1c, insulin and fasting glucose. We found that hypomethylation at TXNIP-cg19693031 is strongly associated with both type 2 diabetes and higher levels of inflammatory biomarkers (VCAM-1, ICAM-1, MMP-2, sRAGE and P-selectin); however, the relationship between TXNIP-cg19693031 and T2D is independent of the levels of these inflammatory biomarkers. Our results suggest that DNA methylation of TXNIP is linked with multiple biological processes, through which the TXNIP may have broad influence on chronic disease risk.

Plasma homocysteine concentrations and depression: A twin study

Background

Homocysteine is an amino acid formed during metabolism of the essential amino acid methionine that plays an important role in energy metabolism and neurotransmitter synthesis. High levels of homocysteine have been linked to both depression and cardiovascular disease, however studies of depression have not always been consistent, possibly related to differences in methodology among studies. The study of twins in clinical research can be useful in controlling for confounding factors. The purpose of this study was to assess the relationship between depression and plasma homocysteine in a study of twins.

Methods

Homocysteine concentration was assessed in twins (N = 202) from the Vietnam Era Twin Registry, including twin pairs discordant for the diagnosis of Major Depressive Disorder (MDD) and twin pairs without MDD. Self reported depressive symptom levels were also measured as a continous variable using the Beck Depression Inventory (BDI).

Results

The average homocysteine concentration was 7.9 μmol/L (2.1 μmol/L SD, range of 2.0-17.1 μmol/L). There were no within twin pair differences in homocysteine concentration within twin pairs discordant for MDD and within twin pairs that differed for BDI score. There was a significant pair-level relationship between depressive symptoms as measured by mean BDI score and homocysteine concentration, such that the higher the mean BDI score of the twin pair, the higher the mean homocystein of the pair (p < .001). Every 10 point increase in BDI score was associated with an 0.8 μmol/L increase in homocysteine concentration at the pair level.

Conclusions

These findings are not consistent with a causal role for elevated homocysteine in the development of depression, but rather point to familial confounding or other factors that are shared by twin brothers and that contribute to both depression and homocysteine levels.

Association of Depressive Symptoms with Sleep Disturbance: A Co-twin Control Study

BACKGROUND

Few studies have comprehensively evaluated the association of depression with sleep disturbance using a controlled twin study design.

PURPOSE

To cross-sectionally evaluate the association of depression with both objective and subjective sleep disturbance.

METHODS

We studied 246 members of the Vietnam Era Twin Registry. We measured depressive symptoms using the Beck Depression Inventory-II (BDI) and assessed major depression using structured clinical interviews. Twins underwent one-night polysomnography and 7-day actigraphy to derive measures of objective sleep and completed the Pittsburgh Sleep Quality Index for subjective sleep. Multivariable mixed-effects models were used to examine the association.

RESULTS

Twins were all male, mostly white (97%), with a mean (SD) age of 68 (2). The mean (SD) BDI was 5.9 (6.3), and 49 (20%) met the criteria for major depression. For polysomnography, each 5-unit higher BDI, within-pair, was significantly associated with 19.7 min longer rapid eye movement (REM) sleep latency, and 1.1% shorter REM sleep after multivariable adjustment. BDI was not associated with sleep architecture or sleep-disordered breathing. For actigraphy, a higher BDI, within-pair, was significantly associated with lower sleep efficiency, more fragmentation and higher variability in sleep duration. BDI was associated with almost all dimensions of self-reported sleep disturbance. Results did not differ by zygosity, and remained consistent using major depression instead of BDI and were independent of the presence of comorbid posttraumatic stress disorder and antidepressant use.

CONCLUSIONS

Depression is associated with REM sleep disruption in lab and sleep fragmentation and sleep variability at home, but not with sleep architecture or sleep-disordered breathing.

Transcutaneous cervical vagal nerve stimulation reduces sympathetic responses to stress in posttraumatic stress disorder: A double-blind, randomized, sham controlled trial

Objective

Exacerbated autonomic responses to acute stress are prevalent in posttraumatic stress disorder (PTSD). The purpose of this study was to assess the effects of transcutaneous cervical VNS (tcVNS) on autonomic responses to acute stress in patients with PTSD. The authors hypothesized tcVNS would reduce the sympathetic response to stress compared to a sham device.

Methods

Using a randomized double-blind approach, we studied the effects of tcVNS on physiological responses to stress in patients with PTSD (n = 25) using noninvasive sensing modalities. Participants received either sham (n = 12) or active tcVNS (n = 13) after exposure to acute personalized traumatic script stress and mental stress (public speech, mental arithmetic) over a three-day protocol. Physiological parameters related to sympathetic responses to stress were investigated.

Results

Relative to sham, tcVNS paired to traumatic script stress decreased sympathetic function as measured by: decreased heart rate (adjusted β = -5.7%; 95% CI: ±3.6%, effect size d = 0.43, p < 0.01), increased photoplethysmogram amplitude (peripheral vasodilation) (30.8%; ±28%, 0.29, p < 0.05), and increased pulse arrival time (vascular function) (6.3%; ±1.9%, 0.57, p < 0.0001). Similar (p < 0.05) autonomic, cardiovascular, and vascular effects were observed when tcVNS was applied after mental stress or without acute stress.

Conclusion

tcVNS attenuates sympathetic arousal associated with stress related to traumatic memories as well as mental stress in patients with PTSD, with effects persisting throughout multiple traumatic stress and stimulation testing days. These findings show that tcVNS has beneficial effects on the underlying neurophysiology of PTSD. Such autonomic metrics may also be evaluated in daily life settings in tandem with tcVNS therapy to provide closed-loop delivery and measure efficacy.ClinicalTrials.gov Registration # NCT02992899.

Alterations in heart rate variability are associated with abnormal myocardial perfusion

BACKGROUND

Abnormalities in the autonomic nervous system may occur in ischemic heart disease, but the mechanisms by which they are linked are not fully defined. The risk of cardiac events is increased during morning hours. Studying the contributions of autonomic mechanisms may yield insights into risk stratification and treatment. We hypothesize that autonomic dysfunction, measured by decreased heart rate variability (HRV), associates with abnormal stress myocardial perfusion imaging (MPI).

METHODS

We performed a cross-sectional study of the association between abnormal myocardial stress perfusion with HRV using 276 middle-aged veteran twins without known ischemic heart disease. The primary independent variable was cardiac autonomic regulation measured with 24-hour electrocardiogram (ECG) monitoring, using linear and non-linear (multipole density, or Dyx) HRV metrics. The primary outcome was abnormal perfusion (>5% affected myocardium) during adenosine stress on [13N]-ammonia myocardial perfusion imaging with positron emission tomography.

RESULTS

The mean (SD) age was 53 (3) years and 55 (20%) had abnormal perfusion. HRV (by Dyx) was reduced during morning hours in subjects with abnormal perfusion. At 7 AM, each standard deviation (SD) decrease in Dyx was associated a 4.8 (95% CI, 1.5 - 15.8) odds ratio (OR) for abnormal MPI. With Dyx < 2.0, the 7 AM OR for abnormal MPI was 11.8 (95% CI, 1.2 - 111.4).

CONCLUSIONS

Autonomic dysfunction, measured by non-linear HRV in the morning hours, was associated with an increased OR of abnormal MPI. These results suggest a potentially important role of ECG-based biomarkers in risk stratification for individuals with suspected ischemic heart disease.

Expectations of Racism and Carotid Intima-Media Thickness in African American Women

OBJECTIVE

Several researchers have argued that racism-related stressors play an important role in adverse cardiovascular outcomes among African American women. However, studies have primarily focused on experiences of racism; thus, the role of expectations of racism is insufficiently understood. The current proof-of-concept study was designed to examine associations among expectations of racism, self-reported experiences of racism, and carotid intima-media thickness (IMT), a marker of cardiovascular risk, in African American women.

METHODS

Participants were 52 healthy African American women, aged 30 to 50 years (M (SD) = 40.8 (4.3)). Expectations of racism were assessed with a modified version of the Race-Based Rejection Sensitivity Questionnaire, experiences of racism were assessed with the Schedule of Racist Events, and carotid IMT was measured using B-mode ultrasound.

RESULTS

In linear regression analyses adjusted for age, expectations of racism were associated with higher levels of carotid IMT (b = .04, SE = .014, p = .013), after adjusting for experiences of racism. Findings remained significant after additional adjustments for cardiovascular risk factors (b = .03, SE = .014, p = .032). Associations were not confounded by additional stressors, hostility, or negative affect (depressive symptoms).

CONCLUSIONS

Independent of actual reports of racism, "expectations" of racism may be associated with increased cardiovascular risk in African American women. In addition, although experiences of discrimination were associated with depressive symptoms, expectations of racism were not, suggesting that other negative emotions likely play a role. Future studies are needed to replicate these results in larger samples and to explore the psychological and physiological pathways through which expectations of racism might affect cardiovascular disease risk across a range of populations.

Changes in negative affect and changes in heart rate variability among low-income latinos with type 2 diabetes in a randomized, controlled stress management trial

BACKGROUND

Structural equation modeling examined the relationship between change in negative affect (NA) and change in heart rate variability (HRV) among 121 Latinos with type 2 diabetes.

METHODS

This study leveraged data from the Community Health Workers Assisting Latinos Manage Stress and Diabetes (CALMSD) study which compared diabetes education vs diabetes education plus stress management. Participants completed surveys of NA at baseline and again 8-10 weeks later. They also wore 7‑lead, 3-channel ambulatory ECG monitors for 24 h at both time points. The latent variable NA was modeled by observed scores on symptoms of depression, anxiety, diabetes distress, and wellbeing (reversed). The latent variable HRV was modeled by observed scores in the time domain (the standard deviation of the R-R interval [SDNN] and the root mean square of the successive differences [RMSSD]) and in the frequency domain, i.e., log-transformed ultra-low frequency, very-low frequency, low frequency, and high frequency.

RESULTS

At baseline, there were strong, negative cross-sectional associations between NA and HRV. Baseline NA predicted change in HRV, whereas baseline HRV did not predict change in NA. Controlling for fasting glucose and treatment assignment did not meaningfully alter the findings. Stress management improved NA but not HRV. At followup, a greater reduction (improvement) in NA was associated with a larger increase (improvement) in HRV, with a small-to-medium negative association that approached statistical significance.

CONCLUSIONS

Findings indicate a longitudinal relationship between NA and HRV, and suggest that improvement in one may be associated with improvement in the other.

Association of Depressive Symptoms and Heart Rate Variability in Vietnam War-Era Twins: A Longitudinal Twin Difference Study

IMPORTANCE

Depressive symptoms are associated with lower heart rate variability (HRV), an index of autonomic dysregulation, but the direction of the association remains unclear.

OBJECTIVE

To investigate the temporal association between depression and HRV.

DESIGN, SETTINGS, AND PARTICIPANTS

A longitudinal, cross-lagged twin difference study, with baseline assessments from March 2002 to March 2006 (visit 1) and a 7-year follow-up (visit 2) at an academic research center with participants recruited from a national twin registry. Twins (n = 166) from the Vietnam Era Twin Registry, who served in the US military during the Vietnam War, and were discordant for depression at baseline were recruited.

MAIN OUTCOMES AND MEASURES

At both visits, depressive symptoms were measured using the Beck Depression Inventory-II (BDI-II), and HRV was measured through 24-hour electrocardiogram monitoring. To assess the direction of the association, within-pair differences in multivariable mixed-effects regression models were examined, and standardized β coefficients for both pathways were calculated. The associations were evaluated separately in monozygotic and dizygotic twins.

RESULTS

In the final analytic sample (N = 146), all participants were men, 138 (95%) were white, and the mean (SD) age was 54 (3) years at baseline. Results showed consistent associations between visit 1 HRV and visit 2 BDI score across all HRV domains and models (β coefficients ranging from -0.14 to -0.29), which were not explained by antidepressants or other participant characteristics. The magnitude of the association was similar in the opposite pathway linking visit 1 BDI score to visit 2 HRV, with β coefficients ranging from 0.05 to -0.30, but it was largely explained by antidepressant use. In stratified analysis by zygosity, significant associations were observed in monozygotic and dizygotic twins for the path linking visit 1 HRV to visit 2 BDI score, although the associations were slightly stronger in dizygotic twins.

CONCLUSIONS AND RELEVANCE

The association between depression and autonomic dysregulation, indexed by HRV, is bidirectional, with stronger evidence suggesting that autonomic function affects depression risk rather than vice versa. The opposite causal pathway from depression to lower HRV is mostly driven by antidepressant use. These findings highlight an important role of autonomic nervous system in the risk of depression and contribute new understanding of the mechanisms underlying the comorbidity of depression and cardiovascular disease.

Untargeted metabolomics reveals multiple metabolites influencing smoking-related DNA methylation

AIM

We conducted a joint metabolomic-epigenomic study to identify patterns of epigenetic associations with smoking-related metabolites.

PATIENTS & METHODS

We performed an untargeted metabolome-wide association study of smoking and epigenome-wide association studies of smoking-related metabolites among 180 male twins. We examined the patterns of epigenetic association linked to smoking-related metabolites using hierarchical clustering.

RESULTS

Among 12 annotated smoking-related metabolites identified from a metabolome-wide association study, we observed significant hypomethylation associated with increased level of N-acetylpyrrolidine, cotinine, 5-hydroxycotinine and nicotine and hypermethylation associated with increased level of 8-oxoguanine. Hierarchical clustering revealed common and unique epigenetic-metabolic associations related to smoking.

CONCLUSION

Our study suggested that a joint metabolome-epigenome approach can reveal additional details in molecular responses to the environmental exposure to understand disease risk.

Mental Stress and Ventricular Arrhythmias

Anger and other negative emotions can precipitate sudden death, as shown in studies of population stressors. Clinical studies of patients with implantable defibrillators demonstrate that anger can trigger ventricular arrhythmias. Long-term negative emotions also increase vulnerability to arrhythmias. Mechanisms linking anger and arrhythmias include autonomic changes, which alter repolarization, possibly enhanced in patients with sympathetic denervation, which in turn trigger potentially lethal polymorphic ventricular tachycardias. Interventions which decrease negative emotions and resultant autonomic responses may be therapeutic in patients with implantable cardioverter defibrillators.

The effects of respiratory sinus arrhythmia on anger reactivity and persistence in major depression

The experience of anger during a depressive episode has recently been identified as a poor prognostic indicator of illness course. Given the clinical implications of anger in major depressive disorder (MDD), understanding the mechanisms involved in anger reactivity and persistence is critical for improved intervention. Biological processes involved in emotion regulation during stress, such as respiratory sinus arrhythmia (RSA), may play a role in maintaining negative moods. Clinically depressed (MDD; n = 49) and nondepressed (non-MDD; n = 50) individuals were challenged with a stressful computer task shown to increase anger, while RSA (high frequency range 0.15-0.4 Hz) was collected. RSA predicted future anger, but was unrelated to current anger. That is, across participants, low baseline RSA predicted anger reactivity during the task, and in depressed individuals, those with low RSA during the task had a greater likelihood of anger persistence during a recovery period. These results suggest that low RSA may be a psychophysiological process involved in anger regulation in depression. Low RSA may contribute to sustained illness course by diminishing the repair of angry moods.

High frequency heart-rate variability predicts adolescent depressive symptoms, particularly anhedonia, across one year

BACKGROUND

Few prospective studies examine the link between lower heart rate variability (HRV) and depression symptoms in adolescents. A recent animal model specifically links HRV to anhedonia, suggesting a potential translational model for human research.

METHOD

We investigated the association between spectral measures of resting HRV and depressive symptoms measured one year later, among 73 adolescents, aged 11-18 years. We evaluated (1) the predictive power of relative high frequency (HF) HRV, relative low frequency (LF) and relative very low frequency (VLF) HRV for depressive symptoms; and (2) the relative strength of association between HF HRV and depressive symptomatology (anhedonia, negative mood, interpersonal problems, ineffectiveness, negative self-esteem).

RESULTS

HF HRV significantly predicted self-reported depressive symptoms across one year, controlling for age, puberty and sex. HF HRV was most strongly associated with anhedonia one year later, after considering other facets of depressive symptomatology.

CONCLUSIONS

Results provide support for the prospective relationship between relative HF HRV and depressive symptoms among adolescents across one year. Findings concur with rodent models that suggest a specific link between HF HRV and anhedonia.

LIMITATIONS

We investigated relative spectral power HF HRV and depressive symptom dimensions. We cannot make strong claims about these associations in clinical depression. Physical activity levels could be controlled in future work.

Cumulative stress and autonomic dysregulation in a community sample

Whether cumulative stress, including both chronic stress and adverse life events, is associated with decreased heart rate variability (HRV), a non-invasive measure of autonomic status which predicts poor cardiovascular outcomes, is unknown. Healthy community dwelling volunteers (N = 157, mean age 29 years) participated in the Cumulative Stress/Adversity Interview (CAI), a 140-item event interview measuring cumulative adversity including major life events, life trauma, recent life events and chronic stressors, and underwent 24-h ambulatory ECG monitoring. HRV was analyzed in the frequency domain and standard deviation of NN intervals (SDNN) calculated. Initial simple regression analyses revealed that total cumulative stress score, chronic stressors and cumulative adverse life events (CALE) were all inversely associated with ultra low-frequency (ULF), very low-frequency (VLF) and low-frequency (LF) power and SDNN (all p < 0.05). In hierarchical regression analyses, total cumulative stress and chronic stress each was significantly associated with SDNN and ULF even after the highly significant contributions of age and sex, with no other covariates accounting for additional appreciable variance. For VLF and LF, both total cumulative stress and chronic stress significantly contributed to the variance alone but were not longer significant after adjusting for race and health behaviors. In summary, total cumulative stress, and its components of adverse life events and chronic stress were associated with decreased cardiac autonomic function as measured by HRV. Findings suggest one potential mechanism by which stress may exert adverse effects on mortality in healthy individuals. Primary preventive strategies including stress management may prove beneficial.

X chromosome-wide analysis identifies DNA methylation sites influenced by cigarette smoking

Background

Tobacco smoking is a major cause of chronic disease worldwide. Smoking may induce cellular and molecular changes including epigenetic modification, with both short-term and long-term modification patterns that may contribute to phenotypic expression of diseases. Recent epigenome-wide association studies (EWAS) have identified dozens of smoking-related DNA methylation (DNAm) sites. However, the X chromosomal DNAm sites have been largely overlooked due to a lack of an analytical framework for dealing with the sex-dimorphic distribution. To identify novel smoking-related DNAm sites on the X chromosome, we examined the modality of each X chromosomal DNAm site and conducted a sex-specific association study of cigarette smoking.

Results

We used a discovery sample of 139 middle-age twins, and three replication samples of 78 twins, 464 and 333 unrelated individuals including 47, 17, 22, and 89 current smokers, respectively. After correction for multiple testing, the top smoking-related DNAm sites in BCOR and TSC22D3 were significantly hypermethylated and hypomethylated, respectively, among current smokers. These smoking-associated sites were replicated with meta-analysis p-values of 9.17 × 10⁻¹² and 1.61 × 10⁻⁹. For both sites, the smoking effects on methylation levels were larger in males than that in females.

Conclusions

Our findings highlight the importance of investigating X chromosome methylation patterns and their associations with environmental exposures and disease phenotypes and demonstrate a robust statistical methodology for such study. Existing EWAS of human diseases should incorporate the X chromosomal sites to complete a comprehensive epigenome-wide scan.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0189-2) contains supplementary material, which is available to authorized users.

Reduced heart rate variability in schizophrenia and bipolar disorder compared to healthy controls

OBJECTIVE

Despite current diagnostic systems distinguishing schizophrenia (SZ) and bipolar disorder (BD) as separate diseases, emerging evidence suggests they share a number of clinical and epidemiological features, such as increased cardiovascular disease (CVD) risk. It is not well understood if poor cardiac autonomic nervous system regulation, which can be indexed non-invasively by the calculation of heart rate variability (HRV), contributes to these common CVD risk factors in both diseases.

METHOD

We calculated HRV in 47 patients with SZ, 33 patients with BD and 212 healthy controls. Measures of symptom severity were also collected from the patient groups.

RESULTS

Heart rate variability was significantly reduced in both these disorders in comparison with the healthy participants; however, there were no HRV differences between disorders. Importantly, these reductions were independent of the medication, age or body mass index effects. There was also preliminary evidence that patients with reduced HRV had increased overall and negative psychosis symptom severity regardless of SZ or BD diagnosis.

CONCLUSION

We suggest that HRV may provide a possible biomarker of CVD risk and symptom severity in severe mental illness. Thus, our results highlight the importance of cardiometabolic screening across SZ and bipolar spectrum disorders.

The variable heart: High frequency and very low frequency correlates of depressive symptoms in children and adolescents

BACKGROUND

Work examining the link between lower heart rate variability (HRV) and depression in children and adolescents is lacking, especially in light of the physiological changes that occur during pubertal development.

METHOD

We investigated the association between spectral measures of resting HRV and depressive symptoms among 127 children and adolescents, ages 10-17. Using spectral analysis, we evaluated (1) the association between relative high frequency (HF) HRV and depressive symptoms; (2) the predictive power of relative HF HRV for depressive symptoms in the context of relative low frequency (LF) and relative very low frequency (VLF) HRV; and (3) the relationship between relative HF, LF, and VLF band activity, age and pubertal maturation.

RESULTS

Consistent with previous work, results revealed that relative HF HRV was negatively associated with self-reported depressive symptoms. As well, relative VLF HRV was positively associated with depressive symptoms. Regression analyses revealed that relative HF HRV and relative VLF HRV significantly predicted self-report depressive symptoms while controlling for age, sex and pubertal maturation, with relative VLF HRV emerging as the strongest indicator of depressive symptoms. Developmental findings also emerged. Age and pubertal maturation were negatively associated with relative HF HRV and positively correlated with relative VLF HRV.

CONCLUSIONS

Results provide support for the relationship between HRV and depression and suggest that both HF and VLF HRV are relevant to depression symptom severity. Findings also reinforce the importance of considering pubertal development when investigating HRV-depression associations in children and adolescents.

LIMITATIONS

Influences on cardiac control including physical activity levels and exercise patterns could be controlled in future work. Our data speak to a depressive symptom dimension and relative spectral power HRV. Thus, we cannot make strong claims about relative spectral power HRV and clinical depression.

Exposure to Discrimination and Heart Rate Variability Reactivity to Acute Stress among Women with Diabetes

Exposure to racial discrimination has been linked to physiological reactivity. This study investigated self-reported exposure to racial discrimination and parasympathetic [high-frequency heart rate variability (HF-HRV)] and sympathetic (norepinephrine and cortisol) activity at baseline and then again after acute laboratory stress. Lifetime exposure to racial discrimination was measured with the Schedule of Racist Events scale. Thirty-two women (16 Black and 16 White) with type 2 diabetes performed a public speaking stressor. Beat-to-beat intervals were recorded on electrocardiograph recorders, and HF-HRV was calculated using spectral analysis and natural log transformed. Norepinephrine and cortisol were measured in blood. Higher discrimination predicted lower stressor HF-HRV, even after controlling for baseline HF-HRV. When race, age, A1c and baseline systolic blood pressure were also controlled, racial discrimination remained a significant independent predictor of stressor HF-HRV. There was no association between lifetime discrimination and sympathetic markers. In conclusion, preliminary data suggest that among women with type 2 diabetes mellitus (T2DM), exposure to racial discrimination is adversely associated with parasympathetic, but not sympathetic, reactivity.

Depressive symptoms in heart failure: Independent prognostic factor or marker of functional status?

OBJECTIVE

The prognostic potential of depressive symptoms independent of somatic features of heart failure severity has repeatedly been demonstrated. However, patient-reported functional status has rarely been accounted for in these studies. Thus, it has remained unclear to what extent the predictive power of depressive symptoms may mirror functional status. We therefore aimed to evaluate the prognostic value of depressive symptoms adjusting for patient-reported functional status in a large, well-characterized sample of patients with systolic heart failure.

METHODS

Eight hundred sixty-three patients, 67±12 years old, 72% men, and 42% with New York Heart Association functional classes III/IV, who participated in the extended Interdisciplinary Network Heart Failure (INH) study were investigated. We assessed depressive symptoms using the Patient Health Questionnaire (PHQ-9) and patient-reported functional status with the Kansas City Cardiomyopathy Questionnaire (KCCQ). Data on survival was obtained after a follow-up of 18 months (100% complete).

RESULTS

Depressive symptoms predicted mortality risk (HR per PHQ-9 scale point=1.07, 95% CI 1.04-1.09, p<.001), even after adjustment for heart failure severity and co-morbidities (HR=1.04, 95% CI 1.01-1.07, p=.017). However, they were no longer significant predictors (HR=1.01, 95% CI 0.98-1.05, p=0.46) after additional adjustment for patient-reported functional status, which proved predictive of mortality risk (HR=0.90, 95% CI 0.82-0.99, p=.025).

CONCLUSION

Our results suggest that the association of depressive symptoms with functional status may at least partly explain the prognostic potential of depressive symptoms.

Behavioral influences on cardiac arrhythmias

Stress can trigger both ventricular and atrial arrhythmias, as evidenced by epidemiological, clinical, and laboratory studies, through its impact on autonomic activity. Chronic stress also increases vulnerability to arrhythmias. Novel therapies aimed at decreasing the psychological and physiological response to stress may decrease arrhythmia frequency and improve quality of life.

Depressive symptomatology and respiratory sinus arrhythmia in a non-clinical sample of middle-aged African Americans

Decreased heart rate variability and depression are both independent risk factors for cardiac mortality in clinical and non-clinical samples. The purpose of the current study is to examine the hypothesis that severity of depressive symptomatology is inversely associated with respiratory sinus arrhythmia (RSA) in a non-clinical sample of African Americans. The sample included 77 African Americans with a mean age of 48.4 (SD = 11.7). Participants completed the Beck Depression Inventory-II (BDI-II) and a 5-min resting baseline measurement of RSA was collected. The BDI-II total score was positively associated with RSA (β = .334, p = .008). Given the unexpected direction of the association, we separated the BDI-II into cognitive and somatic affective subscales to identify which construct was driving the relationship. The somatic affective, was related to RSA (β = .328, p = .010), but not the cognitive subscale. Given this unexpected positive result, future research should further examine the nature of the relationship between depressive symptomatology and RSA in African Americans, as the relationship may vary based on levels of depressive symptomatology.

Interoceptive dysfunction: toward an integrated framework for understanding somatic and affective disturbance in depression

Depression is characterized by disturbed sleep and eating, a variety of other nonspecific somatic symptoms, and significant somatic comorbidities. Why there is such close association between cognitive and somatic dysfunction in depression is nonetheless poorly understood. An explosion of research in the area of interoception-the perception and interpretation of bodily signals-over the last decade nonetheless holds promise for illuminating what have until now been obscure links between the social, cognitive-affective, and somatic features of depression. This article reviews rapidly accumulating evidence that both somatic signaling and interoception are frequently altered in depression. This includes comparative studies showing vagus-mediated effects on depression-like behaviors in rodent models as well as studies in humans indicating both dysfunction in the neural substrates for interoception (e.g., vagus, insula, anterior cingulate cortex) and reduced sensitivity to bodily stimuli in depression. An integrative framework for organizing and interpreting this evidence is put forward which incorporates (a) multiple potential pathways to interoceptive dysfunction; (b) interaction with individual, gender, and cultural differences in interoception; and (c) a developmental psychobiological systems perspective, emphasizing likely differential susceptibility to somatic and interoceptive dysfunction across the lifespan. Combined with current theory and evidence, it is suggested that core symptoms of depression (e.g., anhedonia, social deficits) may be products of disturbed interoceptive-exteroceptive integration. More research is nonetheless needed to fully elucidate the relationship between mind, body, and social context in depression.

Ambulatory assessment as a means of longitudinal phenotypes characterization in psychiatric disorders

Ambulatory Assessment (AA) comprises the use of in-field methods to assess individuals' behavior, physiology, and the experience as they unfold in naturalistic settings. We propose that AA is favorable for the investigation of gene-environment interactions and for the search for endophenotypes, being able to assess the experienced environment and to track basic regulatory processes, such as stress reactivity, affective instability, and reward experience, which are potential common factors that underlie psychiatric disorders. In this article, we (a) first describe briefly the rationale of AA and summarize the key advantages of the approach, (b) highlight within-subject regulatory processes, such as stress reactivity, affective instability, and reward experience, (c) describe studies that used AA to examine genetic influences in psychiatric disorders, and (d) briefly review longitudinal studies that have investigated phenotypes of psychiatric disorders. The reported studies yielded promising, although sometimes inconclusive evidence for genetic effects on endophenotypes of psychiatric disorders. Moreover, most studies were twin or family studies, especially in stress-sensitivity research; thus, it is unclear which specific single nucleotide polymorphisms contribute to the endophenotypes of psychiatric disorders. We do hope that within-subject regulatory processes will enable us to clarify the fundamental psychological dimensions that cut across traditional disorders and link them to their genetic underpinnings.

Heart rate variability measurement and clinical depression in acute coronary syndrome patients: narrative review of recent literature

AIM

We aimed to explore links between heart rate variability (HRV) and clinical depression in patients with acute coronary syndrome (ACS), through a review of recent clinical research literature.

BACKGROUND

Patients with ACS are at risk for both cardiac autonomic dysfunction and clinical depression. Both conditions can negatively impact the ability to recover from an acute physiological insult, such as unstable angina or myocardial infarction, increasing the risk for adverse cardiovascular outcomes. HRV is recognized as a reflection of autonomic function.

METHODS

A narrative review was undertaken to evaluate state-of-the-art clinical research, using the PubMed database, January 2013. The search terms "heart rate variability" and "depression" were used in conjunction with "acute coronary syndrome", "unstable angina", or "myocardial infarction" to find clinical studies published within the past 10 years related to HRV and clinical depression, in patients with an ACS episode. Studies were included if HRV measurement and depression screening were undertaken during an ACS hospitalization or within 2 months of hospital discharge.

RESULTS

Nine clinical studies met the inclusion criteria. The studies' results indicate that there may be a relationship between abnormal HRV and clinical depression when assessed early after an ACS event, offering the possibility that these risk factors play a modest role in patient outcomes.

CONCLUSION

While a definitive conclusion about the relevance of HRV and clinical depression measurement in ACS patients would be premature, the literature suggests that these measures may provide additional information in risk assessment. Potential avenues for further research are proposed.

Posttraumatic stress disorder and impaired autonomic modulation in male twins

BACKGROUND

Posttraumatic stress disorder (PTSD) has been linked to increased morbidity. An inflexibility of the autonomic nervous system might be the underlying mechanism. We aimed to assess whether PTSD and combat trauma exposure are associated with lower heart rate variability (HRV), a measure of autonomic function and a predictor of death.

METHODS

We measured HRV by power spectral analysis on 24-hour ambulatory electrocardiogram in 459 middle-aged veteran male twins. Combat trauma was assessed with the combat exposure scale, and current and remitted PTSD was assessed with the Structured Clinical Interview for Psychiatry Disorders. Mixed-effects regression models were used to test associations of PTSD and HRV between and within twin pairs.

RESULTS

Of all twins, 211 had combat exposure, 31 had current PTSD, and 43 had remitted PTSD. Current PTSD was inversely associated with very-low-frequency and low-frequency HRV both in individual twins and within 20 pairs discordant for current PTSD. Twins with current PTSD had a 49% lower low-frequency HRV than their brothers without PTSD (p<.001). Remitted PTSD was not associated with HRV. Results were robust to adjustment for depression and other risk factors. Combat exposure was inversely associated with most HRV frequencies, but this association mostly diminished after adjustment for current PTSD.

CONCLUSION

In middle-aged veteran men, combat exposure and current PTSD are associated with measures of autonomic inflexibility previously shown to have prognostic significance. The negative health impact of combat exposure on autonomic function is mediated largely through PTSD and might reverse with remission of PTSD.

Association between posttraumatic stress disorder and inflammation: a twin study

The association of posttraumatic stress disorder (PTSD) with cardiovascular disease risk may be mediated by inflammation. Our objective was to examine the association between PTSD and measures of inflammation and to determine whether these associations are due to shared familial or genetic factors. We measured lifetime history of PTSD using the Structured Clinical Interview for DSM-IV in 238 male middle-aged military veteran twin pairs (476 individuals), selected from the Vietnam Era Twins Registry, who were free of cardiovascular disease at baseline. We assessed inflammation using levels of high-sensitivity C-reactive protein (hsCRP), interleukin 6 (IL-6), fibrinogen, white blood cells, vascular cell adhesion molecule-1, and intercellular adhesion molecule-1 (ICAM-1). Geometric mean levels and percent differences by PTSD were obtained from mixed-model linear regression analyses with adjustment for potential confounders. Within-pair analysis was conducted to adjust for shared family environment and genetics (monozygotic pairs). Overall, 12.4% of participants had a lifetime history of PTSD. Adjusted mean levels of hsCRP and ICAM-1 were significantly higher among those with vs. without PTSD [hsCRP: 1.75 vs. 1.31mg/l (33% difference); ICAM-1: 319 vs. 293ng/ml (9% difference)]. Adjustment for depression rendered the association of PTSD with hsCRP non-statistically significant. For IL-6, no consistent association was seen. Within-pair analysis produced associations that were similar in direction for all three markers but lesser in magnitude for hsCRP and IL-6. There was no evidence of interaction by zygosity. Elevated hsCRP and ICAM-1 are associated with PTSD, and these associations may be confounded by shared non-genetic, antecedent familial and environmental factors.

Cardiovascular disease, psychosocial factors, and genetics: the case of depression

Psychosocial factors are associated with cardiovascular disease, but little is known about the role of genetics in this relationship. Focusing on the well-studied phenotype of depression, current data show that there are shared genetic factors that may give rise to both depression and CVD, and these genetic risks appear to be modified by gender. This pleiotropic effect suggests that a single pathway, when perturbed, gives rise to the dual phenotypes of CVD and depression. The data also suggest that women contribute disproportionately to the depression-CVD comorbidity, and this unbalanced contribution is attributable, in part, to genetic factors. While the underlying biology behind this relationship is unclear, recent data support contributions from inflammatory or serotonergic pathways toward the comorbidity between CVD and depression. Even without knowledge of a specific mechanism, epidemiological observations offer new directions to explain the relationship between depression and CVD that have both research and clinical applications.

Vitamin D status and coronary flow reserve measured by positron emission tomography: a co-twin control study

CONTEXT

Vitamin D insufficiency is associated with increased cardiovascular events in the general population. Additionally, low serum 25-hydroxyvitamin D [25(OH)D] is associated with endothelial dysfunction and arterial stiffness. However, little is known about the association between serum 25(OH)D level and myocardial blood flow.

OBJECTIVE

Our objective was to examine the association between serum 25(OH)D levels and coronary flow reserve (CFR) measured by (13)N-positron emission tomography in asymptomatic middle-aged male twins.

DESIGN

The Emory Twin Study is a cross-sectional study of soldiers from the Vietnam Era Registry.

SETTING

The study was conducted at the General Clinical Research Center, Emory University, Atlanta, GA.

PARTICIPANTS

A total of 368 middle-aged male twins were enrolled for the study. Serum 25(OH)D levels were measured in all subjects and classified as vitamin D insufficiency [25(OH)D <30 ng/ml] or sufficiency [25(OH)D ≥30 ng/ml]. Positron emission tomography with [(13)N]ammonia was used to evaluate myocardial blood flow at rest and after adenosine stress. CFR was measured as the ratio of maximum to rest myocardial blood flow.

MAIN OUTCOME MEASURE

Primary outcome was CFR measurement.

RESULTS

Mean overall serum 25(OH)D concentration was 37.0 ± 21.4 ng/ml; 167 twins (45%) were vitamin D insufficient. CFR was significantly lower in subjects with vitamin D insufficiency compared with subjects with vitamin D sufficiency (2.41 vs. 2.64; P = 0.007), even after adjustment for traditional cardiovascular risk factors, serum PTH, calcium, and phosphorus levels, and season. An abnormal CFR (CFR <2) was more prevalent in subjects with vitamin D insufficiency than with vitamin D sufficiency (31 vs. 20%; P = 0.03). In addition, in vitamin D status-discordant twin pairs, CFR was significantly lower in the vitamin D-insufficient twin than in the vitamin D-sufficient co-twin (2.35 vs. 2.58; P = 0.037).

CONCLUSION

Vitamin D insufficiency is associated with lower CFR in men. This association may help explain some of the increased cardiovascular risk reported in individuals with vitamin D insufficiency.

Heart rate time irreversibility is impaired in adolescent major depression

We aimed to study heart rate time irreversibility--a nonlinear qualitative characteristics of heart rate variability indicating complexity of cardiac autonomic control at rest and in response to physiological stress (orthostasis) in never-treated major depressive disorder (MDD) adolescent female patients.

METHODS

We studied 20 MDD girls and 20 healthy age-matched girls at the age of 15 to 18 years. The ECG was recorded in supine position and in response to position change from lying to standing (orthostasis). Time irreversibility analysis was performed using Porta's (P%), Guzik's (G%) and Ehlers' (E) index. The depressive disorder severity was evaluated using Montgomery-Asberg Depression Rating Scale (MADRS) and Children's Depression Inventory (CDI).

RESULTS

Resting heart rate time irreversibility indices (logG%, logP%, Ehlers' index) were significantly reduced in MDD female patients without significant differences in response to orthostasis in MDD girls compared to controls. No significant correlations between time irreversibility and MDD severity were observed.

CONCLUSION

This study revealed the impaired heart rate asymmetry pattern indicating an altered complexity of cardiac autonomic regulation in adolescent female patients suffering from MDD.

Heartache and heartbreak--the link between depression and cardiovascular disease

The close, bidirectional relationship between depression and cardiovascular disease is well established. Major depression is associated with an increased risk of coronary artery disease and acute cardiovascular sequelae, such as myocardial infarction, congestive heart failure, and isolated systolic hypertension. Morbidity and mortality in patients with cardiovascular disease and depression are significantly higher than in patients with cardiovascular disease who are not depressed. Various pathophysiological mechanisms might underlie the risk of cardiovascular disease in patients with depression: increased inflammation; increased susceptibility to blood clotting (owing to alterations in multiple steps of the clotting cascade, including platelet activation and aggregation); oxidative stress; subclinical hypothyroidism; hyperactivity of the sympatho-adrenomedullary system and the hypothalamic-pituitary-adrenal axis; reductions in numbers of circulating endothelial progenitor cells and associated arterial repair processes; decreased heart rate variability; and the presence of genetic factors. Early identification of patients with depression who are at risk of cardiovascular disease, as well as prevention and appropriate treatment of cardiovascular disease in these patients, is an important and attainable goal. However, adequately powered studies are required to determine the optimal treatment regimen for patients with both depression and cardiovascular disorders.

Early trauma and inflammation: role of familial factors in a study of twins

OBJECTIVE

Although early trauma (trauma in childhood) has been linked to adult inflammation and adult disease of inflammatory origin, it remains unknown whether this relationship is due to long-term consequences of early life stress or other familial factors.

METHODS

We examined 482 male middle-aged twins (241 pairs) born between 1946 and 1956 from the Vietnam Era Twin Registry. Childhood traumatic experiences, before the age of 18 years, were measured retrospectively with the Early Trauma Inventory and included physical, sexual, emotional abuse and general trauma. Lifetime major depressive disorder and posttraumatic stress disorder were assessed with the Structured Clinical Interview for DSM-IV. Traditional risk factors for cardiovascular disease were also assessed. Plasma C-reactive protein and interleukin 6 were measured to determine levels of inflammation. Mixed-effects regression models with a random intercept for pair were used to separate between- and within-twin pair effects.

RESULTS

When twins were analyzed as individuals, increasing levels of early trauma were positively related to C-reactive protein (p = .03) but not to interleukin 6 (p = .12). When estimating within- and between-pair effects, only the between-pair association of early trauma with the inflammatory markers remained significant.

CONCLUSIONS

The link between early trauma and inflammation is largely explained by familial factors shared by the twins because levels of inflammation were highest when both twins were exposed to trauma. Exposure to early trauma may be a marker for an unhealthy familial environment. Clarification of familial factors associated with early stress and adult inflammation will be important to uncover correlates of stress and disease.

Depression and history of attempted suicide as risk factors for heart disease mortality in young individuals

CONTEXT

Although depression is associated with increased cardiovascular morbidity and mortality, there is virtually no information on whether it also increases the risk in young populations.

OBJECTIVES

We sought to determine the association of unipolar and bipolar depression and a history of attempted suicide with mortality due to ischemic heart disease (IHD) and cardiovascular disease (CVD) in young US adults and to examine potential sex differences.

DESIGN

Longitudinal epidemiologic study.

SETTING

Nationally representative sample of US adults.

PARTICIPANTS

A total of 7641 US adults aged 17 to 39 years from the 1988-1994 Third National Health and Nutrition Examination Survey.

MAIN OUTCOME MEASURES

Cardiovascular disease and IHD mortality. Unipolar/bipolar depression and a history of attempted suicide were assessed via the Diagnostic Interview Schedule.

RESULTS

After a median follow-up of 14.9 years, a total of 51 subjects (0.67%) died of CVD causes and 28 (0.37%) died of IHD. Depression (538 individuals [7.04%]) and history of attempted suicide (419 [5.48%]) were each associated with an increased risk of IHD death, with adjusted hazard ratios of 3.70 (95% CI, 1.32-10.35) for depression and 7.12 (2.67-18.98) for a history of attempted suicide. Women with depression or a history of attempted suicide had a 3-fold adjusted risk of CVD (adjusted hazard ratio, 3.20 [95% CI, 1.12-9.17]) and a 14-fold adjusted risk of IHD (14.57 [2.65-80.10]). Corresponding figures for men were 2.37 (0.85-6.58) and 3.52 (1.05-11.76).

CONCLUSION

In adults younger than 40 years, depression and history of attempted suicide are significant independent predictors of premature CVD and IHD mortality in both sexes.

Is depression an inflammatory disorder?

Studies consistently report that groups of individuals with major depressive disorder (MDD) demonstrate increased levels of a variety of peripheral inflammatory biomarkers when compared with groups of nondepressed individuals. These findings are often interpreted as meaning that MDD, even in medically healthy individuals, may be an inflammatory condition. In this article, we examine evidence for and against this idea by looking more closely into what the actual patterns of inflammatory findings indicate in terms of the relationship between MDD and the immune system. Data are presented in support of the idea that inflammation only contributes to depression in a subset of patients versus the possibility that the depressogenic effect of inflammatory activation is more widespread and varies depending on the degree of vulnerability any given individual evinces in interconnected physiologic systems known to be implicated in the etiology of MDD. Finally, the treatment implications of these various possibilities are discussed.

Heart rate variability during motor and cognitive tasks in females with major depressive disorder

Research indicates that major depressive disorder (MDD) is associated with alterations in autonomic control, particularly cardiac control as measured by heart rate variability (HRV). In this preliminary study, we investigated the neural correlates of autonomic control by measuring both HRV and associated brain activity during the performance of mildly stressful tasks. Medically healthy female subjects with MDD (N=10) and healthy controls (N=7) underwent H(2)(15)O-positron emission tomography (PET) and electrocardiographic ECG recording while performing a handgrip motor task and an n-back task. Indices of HRV were calculated and correlated with regional cerebral blood flow (rCBF). Differences in the rCBF and HRV correlations between depressed and healthy subjects were evident in both the medial and lateral orbital cortices. In addition, these areas appeared to be involved in different facets of autonomic control with regard to sympathetic or parasympathetic dominance of cardiac control. These results are consistent with the known roles of networks within the orbital cortex in both autonomic control and the pathophysiology of MDD.

Effects of smoking on coronary microcirculatory function: a twin study

BACKGROUND

In asymptomatic smokers, coronary microcirculatory dysfunction, assessed by coronary flow reserve (CFR), is an early indicator of cardiovascular risk. Inflammation and oxidative stress may be the mechanisms through which smoking affects the microvasculature.

OBJECTIVES

The purpose of this study was to determine the relationship between smoking and CFR, taking into account potential shared genetic effects.

METHODS

We examined 360 male middle aged twins (288 non-smokers and 72 smokers), including 46 twin pairs discordant for current smoking. Coronary flow reserve (CFR) in response to adenosine was measured with positron emission tomography [N(13)] ammonia and quantitation of coronary blood flow at rest and after adenosine stress. Inflammation was assessed by measuring interleukin-6 and C-reactive protein, and oxidative stress was determined by measuring plasma hydroperoxides, glutathione (GSH), the oxidized form of GSH, GSSG, and the ratio of GSH to GSSG.

RESULTS

CFR was significantly lower in smokers compared to nonsmokers (2.25 vs. 2.75, p<0.01). This relationship persisted after accounting for known cardiovascular disease risk factors, and was marginally affected by adjusting for inflammatory and oxidative stress biomarkers. In addition, in smoking-discordant twin pairs, CFR in the smoking twin was significantly lower than in the non-smoking co-twin (2.25 vs. 2.67, p=0.03) even after adjustment for cardiovascular risk factors.

CONCLUSIONS

Our results demonstrate the adverse effects of smoking in the early phases of cardiovascular disease. Mechanisms other than peripherally measured inflammation and oxidative stress are involved.

Is heart rate variability related to memory performance in middle-aged men?

OBJECTIVE

Heart rate variability (HRV), a measure of autonomic function, has been associated with cognitive function, but studies are conflicting. Previous studies have also not controlled for familial and genetic influences.

METHODS

We performed power spectral analysis on 24-hour ambulatory ECGs in 416 middle-aged male twins from the Vietnam Era Twin Registry. Memory and learning were measured by verbal and visual Selective Reminding Tests (SRTs). Mixed-effect regression models were used to calculate associations between and within twin pairs, while adjusting for covariates.

RESULTS

The mean age (standard deviation) was 55 (2.9) years. A statistically significant positive association was found between measures of HRV and verbal, but not visual, SRT scores. The most statistically significant unadjusted association was found between very low frequency HRV and verbal total recall SRT, such that each logarithm of increase in very low frequency was associated with an increased verbal SRT score of 4.85 points (p = .002). The association persisted despite the adjustment for demographic and cardiovascular risk factors, and after accounting for familial and genetic factors by comparing twins within pairs. A significant interaction was found between posttraumatic stress disorder (PTSD) and HRV, such that total power and ultra low frequency were associated with SRT in twins (n = 362) without PTSD, but not in those with PTSD.

CONCLUSIONS

Lower frequency spectra of HRV are associated with verbal, but not visual, learning and memory, particularly in subjects without PTSD. This association may indicate that autonomic nervous system dysregulation plays a role in cognitive decline.

[Psychosomatic aspects of cardiac arrhythmias]

Emotional stress facilitates the occurrence of cardiac arrhythmias including sudden cardiac death. The prevalence of anxiety and depression is increased in cardiac patients as compared to the normal population. The risk of cardiovascular mortality is enhanced in patients suffering from depression. Comorbid anxiety disorders worsen the course of cardiac arrhythmias. Disturbance of neurocardiac regulation with predominance of the sympathetic tone is hypothesized to be causative for this. The emotional reaction to cardiac arrhythmias is differing to a large extent between individuals. Emotional stress may result from coping with treatment of cardiac arrhythmias. Emotional stress and cardiac arrhythmias may influence each other in the sense of a vicious circle. Somatoform cardiac arrhythmias are predominantly of psychogenic origin. Instrumental measures and frequent contacts between physicians and patients may facilitate disease chronification. The present review is dealing with the multifaceted relationships between cardiac arrhythmias and emotional stress. The underlying mechanisms and corresponding treatment modalities are discussed.