Resilience and vagal tone predict cardiac recovery from acute social stress

Diminished vagal tone is a predictive biomarker of necrotizing enterocolitis-risk in preterm infants

BACKGROUND

Necrotizing enterocolitis (NEC) is an acute neonatal inflammatory disease which may lead to intestinal necrosis, multisystem failure, and death. Currently, NEC is diagnosed by a combination of laboratory and radiographic tests conducted a posteriori i.e., when NEC is already clinically significant. Given the acute onset and rapid progression of NEC, a non-invasive biomarker that allows early detection of patients at risk is required as a matter of urgency. We evaluated whether the high frequency (HF) component of heart rate variability (HRV), a measure of vagal efferent tonic cholinergic activity may be used as a predictive biomarker for NEC-risk before the onset of clinical disease.

METHODS

In this prospective study, stable preterm (gestational age 28-35 weeks) infants had HRV power spectra analyzed from surface electrocardiogram waveforms taken at rest on day 5-8 of life. We used regression modeling to determine the utility of HF-HRV in predicting NEC.

KEY RESULTS

HF-HRV power was 21.5 ± 2.7 and 3.9 ± 0.81 ms(2) in infants that remained healthy and those that later developed stage 2+ NEC, respectively (p < 0.001). Nine of 70 enrolled infants developed NEC. The ROC discriminated a HF-HRV value of 4.68 ms(2) predictive for developing NEC with a sensitivity and specificity of 89% and 87%, and positive and negative predictive value of 50% and 98%, respectively. With predictive regression modeling, the risk (odds ratio) of developing NEC was 10 per every one SD decrease in HF-HRV.

CONCLUSIONS & INFERENCES

Our preliminary data indicate that HF-HRV may serve as a potential, non-invasive predictive biomarker of NEC-risk in NICU infants.

Dispositional resilience as a moderator of the relationship between chronic stress and irregular menstrual cycle

PURPOSE

Menstrual-cycle irregularity may have an important influence on the subsequent development of chronic diseases. Several risk factors for irregular menstrual cycles have been detected, including stress. Our aim was to extend research on the link between chronic stress and menstrual-cycle irregularity and to assess potential protective factors, such as dispositional resilience, which we hypothesize to be associated with the maintenance or promotion of a healthy menstrual cycle.

METHODS

For this cross-sectional study, data on 696 healthy women aged 20-40 years were obtained. The women completed measures of chronic stress, dispositional resilience and menstrual-cycle irregularity. Furthermore, potential confounds were assessed.

RESULTS

Of the participants, 383 (55%) reported no current use of hormonal contraceptives; 313 (45%) reported current use hormonal contraception and were included as a control group. The results suggest that in women not using hormonal contraception, chronic stress (OR = 1.05, 95%CI = 1.02-1.08, p = 0.001) and dispositional resilience (OR = 0.43, 95%CI = 0.31-0.59, p < 0.001) have a main effect on menstrual cycle regularity. In addition, women with greater dispositional resilience have reduced risk for irregular menstrual cycles in the face of low to moderate chronic stress; however, this association is changed at the highest level of chronic stress.

CONCLUSIONS

These findings suggest that dispositional resilience may be a protective psychological trait that modulates reproductive functioning.

How you perceive threat determines your behavior

The prioritization of processing emotional stimuli usually produces deleterious effects on task performance when it distracts from a task. One common explanation is that brain resources are consumed by emotional stimuli, diverting resources away from executing the task. Viewing unpleasant stimuli also generates defensive reactions, and these responses may be at least partially responsible for the effect of the emotional modulation observed in various reaction time (RT) paradigms. We investigated whether modulatory effects on RT vary if we presented threat stimuli to prompt different defensive responses. To trigger different responses, we manipulated threat perception by moving the direction of threatening stimuli. Threatening or neutral stimuli were presented as distractors during a bar orientation discrimination task. The results demonstrated that threat stimuli directed toward the observer produced a decrease in RT; in contrast, threat stimuli directed away from the observer produced an increase in RT, when compared to neutral stimuli. Accelerated RT during directed toward threat stimuli was attributed to increased motor preparation resulting from strong activation of the defense response cascade. In contrast, directed away threat stimuli likely activated the defense cascade, but less intensively, prompting immobility. Different threat stimuli produced varying effects, which was interpreted as evidence that the modulation of RT by emotional stimuli represents the summation of attentional and motivational effects. Additionally, participants who had been previously exposed to diverse types of violent crime were more strongly influenced by threat stimuli directed toward the observer. In sum, our data support the concept that emotions are indeed action tendencies.

Emotion and attention interaction: a trade-off between stimuli relevance, motivation and individual differences

Mounting evidence suggests that the neural processing of emotional stimuli is prioritized. However, whether the processing of emotional stimuli is dependent on attention remains debatable. Several studies have investigated this issue by testing the capacity of emotional distracters to divert processing resources from an attentional main task. The attentional load theory postulates that the perceptual load of the main task determines the selective processing of the distracter. Although we agree with this theory, we also suggest that other factors could be important in determining the association between the load of the main task and distracter processing, namely, (1) the relevance of the to-be ignored stimuli and (2) the engagement in the main task due to motivation. We postulate that these factors function as opposite forces to influence distracter processing. In addition, we propose that this trade-off is modulated by individual differences. In summary, we suggest that the relationship between emotion and attention is flexible rather than rigid and depends on several factors. Considering this perspective may help us to understand the divergence in the results described by several studies in this field.

Resting vagal control and resilience as predictors of cardiovascular allostasis in peacekeepers

The body's adaptive reaction to a stressful event, an allostatic response, involves vigorous physiological engagement with and efficient recovery from stress. Our aim was to investigate the influence of individual predispositions on cardiac responses to and recovery from a standardized psychosocial stress task (Trier Social Stress Task) in peacekeepers. We hypothesized that those individuals with higher trait resilience and those with higher resting vagal control would be more likely to present an allostatic response: a vigorous cardiac response to stress (i.e., reduction in interbeat intervals and heart rate variability (HRV)) coupled with a significant cardiac recovery in the aftermath. Fifty male military personnel with a mean age of 25.4 years (SD ± 5.99) were evaluated after returning from a peacekeeping mission. Electrocardiogram recordings were made throughout the experimental session, which consisted five conditions: basal, speech preparation, speech delivery, arithmetic task, and recovery. Mean interbeat intervals and HRV were calculated for each condition. An Ego-Resilience Scale and resting vagal control assessed individual predispositions. Stress tasks reduced interbeat intervals (tachycardia) and HRV in comparison with basal, with return to basal in the aftermath (p < 0.001, for all comparisons). Resilience and resting vagal control correlated positively with cardiac parameters for both stress reactivity and recovery (r ≥ 0.29; p < 0.05). In conclusion, peacekeepers showing higher trait resilience and those with higher resting vagal control presented a more adaptive allostatic reaction characterized by vigorous cardiac response to stress (i.e., tachycardia and vagal withdrawal) and efficient cardiac recovery after stress cessation.

Relation between Respiratory Sinus Arrythymia and Startle Response during Predictable and Unpredictable Threat

Research suggests that lower respiratory sinus arrhythmia (RSA) is associated with greater aversive responding. One physiological indicator of aversive responding is startle potentiation. While a few studies have demonstrated an inverse association between RSA and startle potentiation, no study to date has distinguished whether this relation is similar for predictable versus unpredictable aversive stimuli. This is an important distinction, given that degree of predictability has been shown to be an important determinant of aversive responding. The present study examined whether resting RSA was associated with startle eye blink responding during predictable and unpredictable threat of electric shock. Resting RSA was collected during a 6-minute seated baseline phase at the beginning of the experimental session. Participants then completed a computerized startle task in which predictable and unpredictable shocks were administered. Results indicated that lower resting RSA was associated with greater startle potentiation during unpredictable threat, but not during predictable threat. These findings are consistent with a growing body of literature suggesting that individual differences in RSA are associated with aversive responding, and extend previous work by suggesting that RSA may be more robustly associated with a heightened sensitivity to unpredictable threat. This pattern of results may have implications for the understanding of pathological anxiety given that individuals with anxiety disorders typically exhibit low RSA and heightened responding during unpredictable threat.

Insights into the clinical and functional significance of cardiac autonomic dysfunction in Chagas disease

INTRODUCTION

Exclusive or associated lesions in various structures of the autonomic nervous system occur in the chronic forms of Chagas disease. In the indeterminate form, the lesions are absent or mild, whereas in the exclusive or combined heart and digestive disease forms, they are often more pronounced. Depending on their severity these lesions can result mainly in cardiac parasympathetic dysfunction but also in sympathetic dysfunction of variable degrees. Despite the key autonomic effect on cardiovascular functioning, the pathophysiological and clinical significance of the cardiac autonomic dysfunction in Chagas disease remains unknown.

METHODS

Review of data on the cardiac autonomic dysfunction in Chagas disease and their potential consequences, and considerations supporting the possible relationship between this disturbance and general or cardiovascular clinical and functional adverse outcomes.

RESULTS

We hypothesise that possible consequences that cardiac dysautonomia might variably occasion or predispose in Chagas disease include: transient or sustained arrhythmias, sudden cardiac death, adverse overall and cardiovascular prognosis with enhanced morbidity and mortality, an inability of the cardiovascular system to adjust to functional demands and/or respond to internal or external stimuli by adjusting heart rate and other hemodynamic variables, and immunomodulatory and cognitive disturbances.

CONCLUSIONS

Impaired cardiac autonomic modulation in Chagas disease might not be a mere epiphenomenon without significance. Indirect evidences point for a likely important role of this alteration as a primary predisposing or triggering cause or mediator favouring the development of subtle or evident secondary cardiovascular functional disturbances and clinical consequences, and influencing adverse outcomes.

"Shift-and-Persist" Strategies: Why Low Socioeconomic Status Isn't Always Bad for Health

Some individuals, despite facing recurrent, severe adversities in life such as low socioeconomic status (SES), are nonetheless able to maintain good physical health. This article explores why these individuals deviate from the expected association of low SES and poor health and outlines a "shift-and-persist" model to explain the psychobiological mechanisms involved. This model proposes that, in the midst of adversity, some children find role models who teach them to trust others, better regulate their emotions, and focus on their futures. Over a lifetime, these low-SES children develop an approach to life that prioritizes shifting oneself (accepting stress for what it is and adapting the self through reappraisals) in combination with persisting (enduring life with strength by holding on to meaning and optimism). This combination of shift-and-persist strategies mitigates sympathetic-nervous-system and hypothalamic-pituitary-adrenocortical responses to the barrage of stressors that low-SES individuals confront. This tendency vectors individuals off the trajectory to chronic disease by forestalling pathogenic sequelae of stress reactivity, like insulin resistance, high blood pressure, and systemic inflammation. We outline evidence for the model and argue that efforts to identify resilience-promoting processes are important in this economic climate, given limited resources for improving the financial circumstances of disadvantaged individuals.

The interactive effect of change in perceived stress and trait anxiety on vagal recovery from cognitive challenge

The present study tested the hypothesis that the change in state negative affect (measured as perceived stress) after cognitive challenge moderates the relationship of trait anxiety and anger to vagal recovery from that challenge. Cardiac vagal control (assessed using heart rate variability) and respiratory rate were measured in a sample of 905 participants from the Midlife in the United States Study. Cognitive challenges consisted of computerized mental arithmetic and Stroop color-word matching tasks. Multiple regression analyses controlling for the effects of the demographic, lifestyle, and medical factors influencing cardiac vagal control showed a significant moderating effect of change in perceived stress on the relationship of trait anxiety to vagal recovery from cognitive challenges (Beta=.253, p=.013). After adjustment for respiratory rate, this effect became marginally significant (Beta=.177, p=.037). In contrast, for the relationship of trait anger to vagal recovery, this effect was not significant either before (Beta=.141, p=.257) or after (Beta=.186, p=.072) adjusting for respiratory rate. Secondary analyses revealed that among the individuals with higher levels of trait anxiety, greater reductions in perceived stress were associated with greater increases in cardiac vagal control after the challenge. In contrast, among the individuals with lower levels of trait anxiety, changes in perceived stress had no impact on vagal recovery. Therefore, change in perceived stress moderates the relationship of trait anxiety, but not trait anger, to vagal recovery from cognitive challenge.

Moderate vagal withdrawal in 3.5-year-old children is associated with optimal performance on executive function tasks

Vagal tone (measured via respiratory sinus arrhythmia, RSA) and vagal withdrawal (measured by decreases in RSA) have been identified as physiological measures of self-regulation, but little is known how they may relate to the regulation of cognitive activity as measured through executive function (EF) tasks. We expected that baseline measures of vagal tone, thought to be an indicator of attention, would correlate with EF performance. We also predicted that vagal withdrawal would allow for the reorientation of attention that is needed to succeed on EF tasks, but too much withdrawal would be detrimental. RSA measured at baseline was indeed related to EF performance in 220 3.5-year-old children, and those who exhibited a moderate decrease in RSA during the EF tasks outperformed children whose RSA decreased by too little or too much. These findings implicate vagal tone withdrawal as a psychophysiological measure of higher cognitive processes, most likely substantiated through increases in the levels of focused attention.

Long-term meditation is associated with increased gray matter density in the brain stem

Extensive practice involving sustained attention can lead to changes in brain structure. Here, we report evidence of structural differences in the lower brainstem of participants engaged in the long-term practice of meditation. Using magnetic resonance imaging, we observed higher gray matter density in lower brain stem regions of experienced meditators compared with age-matched nonmeditators. Our findings show that long-term practitioners of meditation have structural differences in brainstem regions concerned with cardiorespiratory control. This could account for some of the cardiorespiratory parasympathetic effects and traits, as well as the cognitive, emotional, and immunoreactive impact reported in several studies of different meditation practices.