The interaction between pupil function and cardiovascular regulation in patients with acute schizophrenia

Altered cardiac autonomic functioning associates with self-disorders in schizophrenia

Elevated resting heart rate (RHR) and reduced heart rate variability (HRV) are signs of autonomic nervous system dysfunction identified in schizophrenia (SCZ). This dysfunction has been found to manifest prior to the onset of the clinical diagnosis. Yet whether such autonomic dysfunction is associated with vulnerability to schizophrenia remains unknown. This case-control study included recent onset SCZ patients (n = 35) and healthy controls (HC) (n = 33). Patients were scored for self-disorders (SD's) using the EASE manual and all participants underwent a 5-minute resting state electrocardiogram (ECG) recording. Patients were included from outpatient clinics in Denmark. The main measures comprised EASE total scores (SDs), RHR (beats per minute) and three standard HRV measures usually included in testing autonomic nervous system dysfunction: root mean squared of successive differences (RMSSD), standard deviation of normal-to-normal interval (SDNN) and high-frequency/ low frequency ratio (HF/LF). Pearson correlations and linear regression models adjusted for age, sex and medication were used in the SCZ group. The main finding was a positive moderate association between SDs and RHR (r = 0.463; p = 0.005) and a negative association between SDs and HRV (RMSSD) (r = -0.440; p = 0.008) in the SCZ group. Linear regression models found SDs to explain 22 % of the variance of RHR and 19 % in RMSSD. SDs correlated with LF/HF (r = 0.434; p = 0.009), but non-significantly with SDNN. The study provides evidence of an intriguing link between SDs as a susceptibility trait for schizophrenia spectrum disorders and altered cardiac autonomic functioning.

Quantitatively characterizing reflexive responses to pitch perturbations

Background

Reflexive pitch perturbation experiments are commonly used to investigate the neural mechanisms underlying vocal motor control. In these experiments, the fundamental frequency–the acoustic correlate of pitch–of a speech signal is shifted unexpectedly and played back to the speaker via headphones in near real-time. In response to the shift, speakers increase or decrease their fundamental frequency in the direction opposing the shift so that their perceived pitch is closer to what they intended. The goal of the current work is to develop a quantitative model of responses to reflexive perturbations that can be interpreted in terms of the physiological mechanisms underlying the response and that captures both group-mean data and individual subject responses.

Methods

A model framework was established that allowed the specification of several models based on Proportional-Integral-Derivative and State-Space/Directions Into Velocities of Articulators (DIVA) model classes. The performance of 19 models was compared in fitting experimental data from two published studies. The models were evaluated in terms of their ability to capture both population-level responses and individual differences in sensorimotor control processes.

Results

A three-parameter DIVA model performed best when fitting group-mean data from both studies; this model is equivalent to a single-rate state-space model and a first-order low pass filter model. The same model also provided stable estimates of parameters across samples from individual subject data and performed among the best models to differentiate between subjects. The three parameters correspond to gains in the auditory feedback controller’s response to a perceived error, the delay of this response, and the gain of the somatosensory feedback controller’s “resistance” to this correction. Excellent fits were also obtained from a four-parameter model with an additional auditory velocity error term; this model was better able to capture multi-component reflexive responses seen in some individual subjects.

Conclusion

Our results demonstrate the stereotyped nature of an individual’s responses to pitch perturbations. Further, we identified a model that captures population responses to pitch perturbations and characterizes individual differences in a stable manner with parameters that relate to underlying motor control capabilities. Future work will evaluate the model in characterizing responses from individuals with communication disorders.

Blunted pupil light reflex is associated with negative symptoms and working memory in individuals with schizophrenia

Two largely separate lines of research have documented altered pupillary dynamics in individuals diagnosed with schizophrenia. An older set of studies has demonstrated reductions in the pupillary light reflex (PLR) in individuals with schizophrenia; however, clinical and cognitive correlates of this blunted PLR have been relatively unexplored. More recently, a large body of work has demonstrated reductions in pupillary dilation in response to cognitive demands in individuals with schizophrenia, and the degree of this blunted pupil dilation has been related to more severe cognitive deficits and motivational negative symptoms. These clinically relevant alterations in the cognitive modulation of pupil size have been interpreted as reflecting insufficient information processing resources or inappropriate effort allocation. To begin to bridge these two lines of work, we investigated the PLR in 34 individuals with schizophrenia and 30 healthy controls and related the amplitude of the PLR to motivational negative symptoms and cognitive performance. Consistent with prior work, we found that the PLR was reduced in individuals with schizophrenia, and furthermore, that these measurements were highly reliable across individuals. Blunted constriction was associated with more severe motivational negative symptoms and poorer working memory among individuals with schizophrenia. These observed correlates provide a bridge between older literature documenting an altered PLR and more recent work reporting associations between negative symptoms, cognition, and blunted pupillary dilation in response to cognitive demands in individuals with schizophrenia. We provide possible mechanistic interpretations of our data and consider a parsimonious explanation for reduced cognitive- and light-related modulation of pupil size.

Development of Autonomic Nervous System Assays as Point-of-Care Tests to Supplement Clinical Judgment in Risk Assessment for Suicidal Behavior: A Review

PURPOSE OF REVIEW

A biomarker point-of-care (POC) test that supplements the psychiatric interview and improves detection of patients at risk for suicide would be of value, and assays of autonomic nervous system (ANS) activity would satisfy the logistical requirements for a POC test. We performed a selective review of the available literature of ANS assays related to risk for suicide.

RECENT FINDINGS

We searched PubMed and Web of Science with the strategy: "suicide OR suicidal" AND "electrodermal OR heart rate variability OR pupillometry OR pupillography." The search produced 119 items, 21 of which provided original data regarding ANS methods and suicide. These 21 studies included 6 for electrodermal activity, 14 for heart rate variability, and 1 for the pupillary light reflex. The 21 papers showed associations between ANS assays and suicide risk in a direction suggesting underlying hyperarousal in patients at risk for suicide. ANS assays show promise for future development as POC tests to supplement clinical decision making in estimating risk for suicide.

A Potential Interface between the Kynurenine Pathway and Autonomic Imbalance in Schizophrenia

Schizophrenia is a neuropsychiatric disorder characterized by various symptoms including autonomic imbalance. These disturbances involve almost all autonomic functions and might contribute to poor medication compliance, worsened quality of life and increased mortality. Therefore, it has a great importance to find a potential therapeutic solution to improve the autonomic disturbances. The altered level of kynurenines (e.g., kynurenic acid), as tryptophan metabolites, is almost the most consistently found biochemical abnormality in schizophrenia. Kynurenic acid influences different types of receptors, most of them involved in the pathophysiology of schizophrenia. Only few data suggest that kynurenines might have effects on multiple autonomic functions. Publications so far have discussed the implication of kynurenines and the alteration of the autonomic nervous system in schizophrenia independently from each other. Thus, the coupling between them has not yet been addressed in schizophrenia, although their direct common points, potential interfaces indicate the consideration of their interaction. The present review gathers autonomic disturbances, the impaired kynurenine pathway in schizophrenia, and the effects of kynurenine pathway on autonomic functions. In the last part of the review, the potential interaction between the two systems in schizophrenia, and the possible therapeutic options are discussed.

The pupillary light reflex (PLR) as a marker for the ability to work or drive - a feasibility study

Background

The PLR (pupillary light reflex) can be a marker for pathological medical conditions, such as neurodegenerative or mental health disorders and diseases as well as marker for physiological alterations, such as age, sex or iris color. PLR alterations have been described in people after alcohol consumption, as well. However, the effect of sleep deprivation on PLR parameters is still under debate.

Methods

The aim of this study was to investigate the feasibility of PLR measurements in sleep-deprived and alcohol-exposed participants. In addition, we wanted to identify PLR parameters that were altered by sleep deprivation and alcohol exposure.

Results

Altogether n = 50 participants have been included in this study. Differences in the PLR parameters initial diameter (d_init), latency (∆t_lat), acceleration (∆t_a), contraction velocity (ϑ_con), quarter dilatation velocity (ϑ_1/4dil), half dilatation time (∆t_1/2), and the line integral (L(0.3500)) have been evaluated between baseline, sleep deprivation, as well as alcohol exposure. In a generalized linear mixed models design, we could observe statistically significant associations between the type of exposure and the PLR parameters half dilatation time and half dilatation time after the first light pulse (all p < 0.05). The participants’ latency showed a significant association in dependence of the type of exposure after the second light pulse (p < 0.05).

Conclusion

Our study delivers first promising results to further develop devices that may identify conditions that impair the ability to work or drive.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12995-021-00330-2.

Autonomic dysfunction detection by an automatic pupillometer as a non-invasive test in patients recovered from COVID-19

Purpose

To recognize dysfunctions in the autonomic nervous system (ANS) with changes in dynamic and static pupillary responses in patients who recovered from coronavirus disease-2019 (COVID-19)

Methods

One month after recovery from COVID-19, patients were subjected to eye examinations. Pupillary responses were measured using a pupillometry system. Dynamic pupil parameters (i.e., pupil contraction amplitude, pupil dilatation latency, pupil contraction latency, pupil dilatation duration, pupil dilatation velocity, pupil contraction duration, pupil contraction velocity, resting pupil diameter [PD]) and static pupil parameters (i.e., mesopic PD, scotopic PD, high photopic PD, and low photopic PD) were registered.

Results

Although high photopic and scotopic PDs were significantly higher in patients recovering from COVID-19 than in healthy controls (P = 0.04 and P = 0.002), no statistically significant difference was found in mesopic and low photopic PD (P = 0.19 and P = 0.41). Regarding dynamic pupillometry parameters, resting PD and pupil contraction velocity (P = 0.04 and P = 0.02, respectively) were significantly higher in patients recovering from COVID-19 than in healthy controls (P < 0.001 and P < 0.001, respectively), whereas pupil dilatation latency and pupil contraction duration were lower in these patients than in healthy controls (P = 0.01 and P = 0.008, respectively). No significant differences in pupil contraction amplitude, pupil dilatation duration, pupil contraction latency, and pupil dilatation velocity were found between the study groups (P = 0.93, P = 0.91, P = 0.42, and P = 0.48, respectively).

Conclusion

Pupil responses, which are controlled by the ANS, were impaired in patients recovering from COVID-19. Pupillometry shows promise as a non-invasive, easy-to-apply diagnostic technology for detecting autonomic dysfunction in patients recovering from COVID-19.

Clinical trial registration

Not applicable.

Electrocardiographic signs of autonomic imbalance in medicated patients with first-episode schizophrenia spectrum disorders – relations to first treatment discontinuation and five-year remission status

Purpose

To explore measures in electrocardiograms (ECG) influenced by autonomic balance in early schizophrenia spectrum disorders and to examine their relation to subsequent first antipsychotic pharmacotherapy discontinuation and five-year remission status.

Subjects and methods

Twelve-lead ECGs were recorded at baseline in 58 patients with first-episode schizophrenia spectrum disorders and in 47 healthy controls of similar age. Selected ECG variables included heart rate and measures of repolarization. Pharmacotherapy data were extracted from medical records. At a five-year follow-up the patients were interviewed and assessed with the Positive and Negative Syndrome Scale.

Results

Patients had higher heart rate and a different ST-T pattern than the controls. High T-wave amplitudes in the leads aVF and V5 and ST-elevations in V5 were associated both with higher risk of an earlier discontinuation of first antipsychotic pharmacotherapy and with non-remission five years later.

Discussion and conclusion

In this longitudinal cohort study, simple ECG measures influenced by autonomic balance in the early phase of schizophrenia spectrum disorders contained prognostic information. As this is the first report of this association and is based on a relatively small sample, the results should be interpreted with caution.

Sympathetic and Parasympathetic Modulation of Pupillary Unrest

Pupillary unrest is an established indicator of drowsiness or sleepiness. How sympathetic and parasympathetic activity contribute to pupillary unrest is not entirely unclear. In this study, we investigated 83 young healthy volunteers to assess the relationship of pupillary unrest to other markers of the autonomic nervous system. Sample entropy (SE) and the established pupillary unrest index (PUI) were calculated to characterize pupil size variability. Autonomic indices were derived from heart rate, blood pressure, respiration, and skin conductance. Additionally, we assessed individual levels of calmness, vigilance, and mood. In an independent sample of 26 healthy participants, we stimulated the cardiovagal system by a deep breathing test. PUI was related to parasympathetic cardiac indices and sleepiness. A linear combination of vagal heart rate variability [root mean square of heart beat interval differences (RMSSD)] and skin conductance fluctuations (SCFs) was suited best to explain interindividual variance of PUI. Complexity of pupil diameter (PD) variations correlated to indices of sympathetic skin conductance. Furthermore, we found that spontaneous fluctuations of skin conductance are accompanied by increases of pupil size. In an independent sample, we were able to corroborate the relation of PUI with RMSSD and skin conductance. A slow breathing test enhanced RMSSD and PUI proportionally to each other, while complexity of PD dynamics decreased. Our data suggest that the slow PD oscillations (f < 0.15 Hz) quantified by PUI are related to the parasympathetic modulation. Sympathetic arousal as detected by SCFs is associated to transient pupil size increases that increase non-linear pupillary dynamics.

Effective combination of pupil light reflex and heart rate variability to assess foot bath effects on autonomic function in healthy adults

OBJECTIVES

To evaluate the effects of a foot bath on autonomic nervous system (ANS) activities as measured by pupil light reflex (PLR) and heart rate variability (HRV) in healthy adults.

METHODS

PLR and HRV were assessed before and during a foot bath in healthy subjects (n = 110). The subjects dipped their feet in 40 °C water at a level below their knees for 15 min The light reflex in PLR was elicited at four ascending stimulus intensities. Linear-mixed effect models were fit with PLR parameters, and a Wilcoxon signed-rank test with HRV parameters. In PLR analysis, an interaction term between the foot bath intervention and the stimulus intensity was included as a fixed effect.

RESULTS

The PLR analysis showed significant interactions in five out of seven parameters. The altered patterns indicated enhanced activity of the parasympathetic nervous system (PNS) due to the intervention. In contrast, the HRV analysis showed few alterations of PNS activities due to the intervention.

CONCLUSIONS

The study results demonstrated differences in altered PNS activity during a foot bath, when assessed by PLR and HRV. In PLR, the stimulus intensity was a crucial factor for the evaluation of foot bath effects. Taken together, the combination of PLR and HRV effectively evaluates ANS activities during a foot bath.

Early Signs of Schizophrenia and Autonomic Nervous System Dysregulation: A Literature Review

OBJECTIVE

Recent research suggests that early signs of schizophrenia can be detected several years before its onset. Evidence suggests that the identification of at-risk individuals before the psychotic onset can significantly improve the course of the disorder. However, instruments employed for the detection of prodromal symptoms are far from being accurate in the prediction of a future transition to psychosis. The aim of the present review is to summarize literature on the early signs of schizophrenia and to identify physiological markers that may aid the identification of the disorder before psychotic transition.

METHOD

This critical review includes studies published between 1979 and 2018 that were indexed in major databases with the following keywords: schizophrenia, prodromal phase, basic symptoms, autonomic nervous system, heart rate variability.

RESULTS

The examination of the relevant literature showed that, despite recent progress in the identification of at-risk states, the currently employed instruments do not allow an effective prediction of a future psychotic onset. Also, evidence suggests a significant association between alterations in the autonomic nervous system (ANS) functioning and psychotic disorders. However, literature on the association between ANS functioning and at-risk states for psychosis is still scarce. The addition of physiological risk indicators may represent a step forward in the detection of at-risk individuals.

CONCLUSIONS

Overall, the present literature review highlights that a future schizophrenic onset cannot be strongly predicted with current available measures. Given the established correlation between schizophrenia and autonomic dysregulation, an investigation of the ANS functioning in individuals who are at increased risk of developing schizophrenia may be particularly useful to improve the quality of the assessment, to identify at an early stage the dysregulated physiological patterns that have been linked with schizophrenia, and therefore to develop tailored interventions. Accordingly, it is crucial that future research investigates the presence of autonomic deficits in individuals at risk for psychosis.

[Electrocardiographic and hemodynamic profile of patients with psychotic disorder]

INTRODUCTION

Cardiac mortality among patients diagnosed with mental disorders is higher compared to the general population. Some authors suggest that cardiovascular risk is related to intrinsic factors specific to psychiatric disease. Nevertheless, the interpretation of these results is limited by the concomitant prescription of antipsychotics which have a cardiovascular effect. Studies evaluating the hemodynamic and electrocardiographic profile of drug naïve or drug-free patients suffering from mental disorders remain few.

AIMS

The aims of this work were to study the electrocardiographic and hemodynamic profile of drug naïve or drug-free patients with mental disorders and to determine clinical and biological factors associated with any electrocardiographic abnormalities.

SUBJECTS AND METHODS

It was a descriptive and evaluative cross-sectional study. We enrolled drug naïve or drug-free patients for at least two months. All subjects were inpatients and had at admission clinical, biological and electrocardiographic evaluation.

RESULTS

Forty-four percent of the sample had asymptomatic electrocardiographic abnormalities. These subjects had lower serum thyroid hormone levels compared to healthy group (P=0.066). Hemodynamic profile showed that 12% of the population had orthostatic hypotension.

CONCLUSION

Electrocardiographic and hemodynamic abnormalities are common among drug-free or drug naïve patients diagnosed with psychotic disorders. The association of electrocardiographic abnormalities with low levels of thyroxin requires more investigation.

Reduced heart rate variability in a treatment-seeking early psychosis sample

Reduced cardiac autonomic function is associated with increased risk of cardiovascular disease (CVD), with heart rate variability (HRV) providing an accessible index of cardiac autonomic function. HRV may provide a candidate physiological mechanism linking reduced cardiac autonomic function to increased risk for CVD in schizophrenia illness. This study examines whether HRV is also reduced in a community sample of treatment-seeking participants experiencing early psychosis (n = 48) compared to healthy volunteers (n = 48) and social anxiety control groups (n = 48) matched by gender and age. HRV was assessed during a five-minute interbeat interval recording at rest. Participants also completed self-report psychiatric symptom measures. Early psychosis participants showed significant reductions in HRV compared to social anxiety and healthy control groups. Reductions in HRV were also observed in early psychosis participants taking anticholinergic medications compared to both control groups taking cardio-benign medications or who were non-medicated. Lastly, whether or not early psychosis participants were taking anticholinergic medications was not associated with reductions in HRV. Findings provide preliminary evidence that early psychosis is associated with reduced HRV. This study supports further research with larger sample sizes to precisely determine the influence of anticholinergic drugs on HRV in early psychosis populations.

Eyeing up the Future of the Pupillary Light Reflex in Neurodiagnostics

The pupillary light reflex (PLR) describes the constriction and subsequent dilation of the pupil in response to light as a result of the antagonistic actions of the iris sphincter and dilator muscles. Since these muscles are innervated by the parasympathetic and sympathetic nervous systems, respectively, different parameters of the PLR can be used as indicators for either sympathetic or parasympathetic modulation. Thus, the PLR provides an important metric of autonomic nervous system function that has been exploited for a wide range of clinical applications. Measurement of the PLR using dynamic pupillometry is now an established quantitative, non-invasive tool in assessment of traumatic head injuries. This review examines the more recent application of dynamic pupillometry as a diagnostic tool for a wide range of clinical conditions, varying from neurodegenerative disease to exposure to toxic chemicals, as well as its potential in the non-invasive diagnosis of infectious disease.

Parasympathetic Nervous System Dysfunction, as Identified by Pupil Light Reflex, and Its Possible Connection to Hearing Impairment

CONTEXT

Although the pupil light reflex has been widely used as a clinical diagnostic tool for autonomic nervous system dysfunction, there is no systematic review available to summarize the evidence that the pupil light reflex is a sensitive method to detect parasympathetic dysfunction. Meanwhile, the relationship between parasympathetic functioning and hearing impairment is relatively unknown.

OBJECTIVES

To 1) review the evidence for the pupil light reflex being a sensitive method to evaluate parasympathetic dysfunction, 2) review the evidence relating hearing impairment and parasympathetic activity and 3) seek evidence of possible connections between hearing impairment and the pupil light reflex.

METHODS

Literature searches were performed in five electronic databases. All selected articles were categorized into three sections: pupil light reflex and parasympathetic dysfunction, hearing impairment and parasympathetic activity, pupil light reflex and hearing impairment.

RESULTS

Thirty-eight articles were included in this review. Among them, 36 articles addressed the pupil light reflex and parasympathetic dysfunction. We summarized the information in these data according to different types of parasympathetic-related diseases. Most of the studies showed a difference on at least one pupil light reflex parameter between patients and healthy controls. Two articles discussed the relationship between hearing impairment and parasympathetic activity. Both studies reported a reduced parasympathetic activity in the hearing impaired groups. The searches identified no results for pupil light reflex and hearing impairment.

DISCUSSION AND CONCLUSIONS

As the first systematic review of the evidence, our findings suggest that the pupil light reflex is a sensitive tool to assess the presence of parasympathetic dysfunction. Maximum constriction velocity and relative constriction amplitude appear to be the most sensitive parameters. There are only two studies investigating the relationship between parasympathetic activity and hearing impairment, hence further research is needed. The pupil light reflex could be a candidate measurement tool to achieve this goal.

A Role for the Transcription Factor Nk2 Homeobox 1 in Schizophrenia: Convergent Evidence from Animal and Human Studies

Schizophrenia is a highly heritable disorder with diverse mental and somatic symptoms. The molecular mechanisms leading from genes to disease pathology in schizophrenia remain largely unknown. Genome-wide association studies (GWASs) have shown that common single-nucleotide polymorphisms associated with specific diseases are enriched in the recognition sequences of transcription factors that regulate physiological processes relevant to the disease. We have used a “bottom-up” approach and tracked a developmental trajectory from embryology to physiological processes and behavior and recognized that the transcription factor NK2 homeobox 1 (NKX2-1) possesses properties of particular interest for schizophrenia. NKX2-1 is selectively expressed from prenatal development to adulthood in the brain, thyroid gland, parathyroid gland, lungs, skin, and enteric ganglia, and has key functions at the interface of the brain, the endocrine-, and the immune system. In the developing brain, NKX2-1-expressing progenitor cells differentiate into distinct subclasses of forebrain GABAergic and cholinergic neurons, astrocytes, and oligodendrocytes. The transcription factor is highly expressed in mature limbic circuits related to context-dependent goal-directed patterns of behavior, social interaction and reproduction, fear responses, responses to light, and other homeostatic processes. It is essential for development and mature function of the thyroid gland and the respiratory system, and is involved in calcium metabolism and immune responses. NKX2-1 interacts with a number of genes identified as susceptibility genes for schizophrenia. We suggest that NKX2-1 may lie at the core of several dose dependent pathways that are dysregulated in schizophrenia. We correlate the symptoms seen in schizophrenia with the temporal and spatial activities of NKX2-1 in order to highlight promising future research areas.

Autonomic nervous system dysfunction in psychiatric disorders and the impact of psychotropic medications: a systematic review and meta-analysis

BACKGROUND

Autonomic nervous system (ANS) dysfunction is a putative underlying mechanism for increased cardiovascular disease risk in individuals with psychiatric disorders. Previous studies suggest that this risk may be related to psychotropic medication use. In the present study we systematically reviewed and analyzed published studies of heart rate variability (HRV), measuring ANS output, to determine the effect of psychiatric illness and medication use.

METHODS

We searched for studies comparing HRV in physically healthy adults with a diagnosed psychiatric disorder to controls and comparing HRV pre- and post-treatment with a psychotropic medication.

RESULTS

In total, 140 case-control (mood, anxiety, psychosis, dependent disorders, k = 151) and 30 treatment (antidepressants, antipsychotics; k = 43) studies were included. We found that HRV was reduced in all patient groups compared to controls (Hedges g = -0.583) with a large effect for psychotic disorders (Hedges g = -0.948). Effect sizes remained highly significant for medication-free patients compared to controls across all disorders. Smaller and significant reductions in HRV were observed for specific antidepressants and antipsychotics.

LIMITATIONS

Study quality significantly moderated effect sizes in case-control analyses, underscoring the importance of assessing methodological quality when interpreting HRV findings.

CONCLUSION

Combined findings confirm substantial reductions in HRV across psychiatric disorders, and these effects remained significant even in medication-free individuals. Reductions in HRV may therefore represent a significant mechanism contributing to elevated cardiovascular risk in individuals with psychiatric disorders. The negative impact of specific medications on HRV suggest increased risk for cardiovascular disease in these groups, highlighting a need for treatment providers to consider modifiable cardiovascular risk factors to attenuate this risk.

Diverse autonomic regulation of pupillary function and the cardiovascular system during alcohol withdrawal

BACKGROUND

Previous research indicated the complexity of autonomic dysfunction during acute alcohol withdrawal. This study aimed to investigate the pupillary light reflex as an indicator of midbrain and brainstem regulatory systems in relation to cardiovascular autonomic function.

METHODS

Thirty male patients were included in the study. They were investigated during acute alcohol withdrawal syndrome and 24h later during clomethiazole treatment and compared to healthy controls. Parameters of pupillary light reflex of both eyes as well as heart rate variability, blood pressure variability and baroreflex sensitivity (BRS) were studied.

RESULTS

We observed significantly reduced sympathetic (small diameter, e.g., left eye: 5.00 in patients vs. 5.91 mm in controls) and vagal modulation (e.g., prolonged latencies, left eye: 0.28 vs. 0.26 ms) regarding both pupils during acute alcohol withdrawal syndrome. Cardiovascular parameters showed reduced vagal modulation (e.g., b-slope of BRS: 7. 57 vs. 13.59 ms/mm Hg) and mixed results for sympathetic influence. After 24h, autonomic dysfunction improved significantly, both for the pupils (e.g., left diameter: 5.38 mm) and the heart (e.g., b-slope of BRS: 9.34 ms/mm Hg). While parameters obtained from the pupil correlated with cardiac autonomic function (e.g, BRS and left diameter: r=0.564) in healthy controls, no such pattern was observed in patients.

CONCLUSION

Results obtained from the pupil during acute alcohol withdrawal do not simply mirror autonomic dysfunction regarding the heart. Pupillary and cardiovascular changes after 24h indicate state dependencies of the results. The findings are discussed with respect to autonomic mechanisms and potentially involved brain regions.

Heart rate variability and vagal tone in schizophrenia: A review

Recent heart rate variability (HRV) research has identified diminished levels of parasympathetic activity among schizophrenia patients. Over two dozen empirically-based studies have been published on this topic; primarily over the last decade. However, no theoretical review appears to have been published on this work. Further, only one empirical study has evaluated HRV research findings in the context of documented hypothalamic-pituitary-adrenal axis hyperactivity in schizophrenia. HRV research indicates that no abnormalities exist in the initial sympathetic stress response of schizophrenia patients. However, evidence has consistently demonstrated that patients exhibit a diminished capacity to recover from a stress response as a result of deficits in parasympathetic activity. Moreover, this diminished parasympathetic nervous system (PNS) response, also known as decreased vagal tone, has been found to relate to increased symptom severity. Although these findings may cause speculation that the observed vagal tone disruption merely results from anxiety produced by the presence of positive symptomology, additional studies have identified similar parasympathetic dysfunction among nonpsychotic relatives of individuals with schizophrenia. We posit that the resulting sympathovagal imbalance leads to an overall sympathetic dominance despite the fact that sympathetic nervous system activity is not abnormally elevated among patients. Implications are discussed within the context of the diathesis-stress/vulnerability-stress model, including the potential for identifying a mechanism of action by which environmental stressors may contribute to triggering first-episode psychosis.

Cardiac Autonomic Dysfunction in Patients with Schizophrenia and Their Healthy Relatives - A Small Review

The majority of excess mortality among people with schizophrenia seems to be caused by cardiovascular complications, and in particular, coronary heart disease. In addition, the prevalence of heart failure and arrhythmias is increased in this population. Reduced efferent vagal activity, which has been consistently described in these patients and their healthy first-degree relatives, might be one important mechanism contributing to their increased cardiac mortality. A decrease in heart rate variability and complexity was often shown in unmedicated patients when compared to healthy controls. In addition, faster breathing rates, accompanied by shallow breathing, seem to influence autonomic cardiac functioning in acute unmedicated patients substantially. Moreover, low-physical fitness is a further and independent cardiac risk factor present in this patient population. Interestingly, new studies describe chronotropic incompetence during physical exercise as an important additional risk factor in patients with schizophrenia. Some studies report a correlation of the autonomic imbalance with the degree of positive symptoms (i.e., delusions) and some with the duration of disease. The main body of psychiatric research is focused on mental aspects of the disease, thereby neglecting obvious physical health needs of these patients. Here, a joint effort is needed to design interventional strategies in everyday clinical settings to improve physical health and quality of life.

Prolonged reaction to mental arithmetic stress in first-degree relatives of schizophrenia patients

OBJECTIVE

Several studies have reported abnormal heart rate variability (HRV) in schizophrenia patients, suggesting a pathophysiological link between central autonomic dysfunction and symptoms of schizophrenia and that these could be heritable. This study aimed at evaluating cardiac autonomic response to mental arithmetic stress in first-degree relatives of schizophrenia patients (FDRS) employing HRV analysis.

METHODS

HRV measures were computed for 25 healthy FDRS and 25 age- and gender-matched controls during rest, mental arithmetic stress task and recovery period. Subtracting serial sevens from 700 for five minutes formed the stress task. Recovery period lasted five minutes starting from the termination of the stress task.

RESULTS

Both groups showed similar alterations during the stress task. After stress termination, recovery to the basal values was observed in controls but not in patients' relatives, maintaining a pattern similar to that during the stress task.

CONCLUSIONS

Poor recovery from cardiac autonomic functions (CAF) alterations induced by arithmetic stress may be a heritable trait marker of schizophrenia. Our report supports endophenotypic potential of HRV in schizophrenia research.

Evaluation of autonomic nervous system by salivary alpha-amylase level and heart rate variability in patients with schizophrenia

Several researches indicate that autonomic nervous system (ANS) dysfunction in patients with schizophrenia. Recently, salivary alpha-amylase (sAA) has been employed as a useful marker for ANS function. We investigated the extent of ANS dysfunction by measuring sAA and heart rate variability (HRV) of 25 patients with schizophrenia compared with controls. Schizophrenia group demonstrated a significant increase in sAA and markedly lower parasympathetic nervous system (PNS) activity in the HRV. However, there were no significant differences between two groups in sympathetic nervous system (SNS) activity. We concluded that PNS might be suppressed and the SNS shows relatively high activity in schizophrenia.

Atypical pupillary light reflex and heart rate variability in children with autism spectrum disorder

We investigated pupillary light reflex (PLR) in 152 children with ASD, 116 typically developing (TD) children, and 36 children with non-ASD neurodevelopmental disorders (NDDs). Heart rate variability (HRV) was measured simultaneously to study potential impairments in the autonomic nervous system (ANS) associated with ASD. The results showed that the ASD group had significantly longer PLR latency, reduced relative constriction amplitude, and shorter constriction/redilation time than those of the TD group. Similar atypical PLR parameters were observed in the NDD group. A significant age effect on PLR latency was observed in children younger than 9 years in the TD group, but not in the ASD and NDD groups. Atypical HRV parameters were observed in the ASD and NDD groups. A significant negative correlation existed between the PLR constriction amplitude and average heart rate in children with an ASD, but not in children with typical development.

Exercise reveals the interrelation of physical fitness, inflammatory response, psychopathology, and autonomic function in patients with schizophrenia

Maintaining and improving fitness are associated with a lower risk of premature death from cardiovascular disease. Patients with schizophrenia are known to exercise less and have poorer health behaviors than average. Physical fitness and physiological regulation during exercise tasks have not been investigated to date among patients with schizophrenia. We studied autonomic modulation in a stepwise exhaustion protocol in 23 patients with schizophrenia and in matched controls, using spirometry and lactate diagnostics. Parameters of physical capacity were determined at the aerobic, anaerobic, and vagal thresholds (VT), as well as for peak output. VT was correlated with psychopathology, as assessed by the Positive and Negative Syndrome Scale, with the inflammatory markers IL-1β, IL-6, and TNF-α and with peak output. The MANOVA for heart and breathing rates, as well as for vagal modulation and complexity behavior of heart rate, indicated a profound lack of vagal modulation at all intensity levels, even after the covariate carbon monoxide concentration was introduced as a measure of smoking behavior. Significantly decreased physical capacity was demonstrated at the aerobic, anaerobic, and VT in patients. After the exercise task, reduced vagal modulation in patients correlated negatively with positive symptoms and with levels of IL-6 and TNF-α. This study shows decreased physical capacity in patients with schizophrenia. Upcoming intervention studies need to take into account the autonomic imbalance, which might predispose patients to arrhythmias during exercise. Results of inflammatory parameters are suggestive of a reduced activity of the anti-inflammatory cholinergic pathway in patients, leading to a pro-inflammatory state.

Cardiac autonomic dysregulation in acute schizophrenia

OBJECTIVE

Altered cardiac autonomic function has been proposed in schizophrenia, but the results are mixed. Therefore, analyses with larger sample sizes and better methodology are needed.

METHODS

To examine whether acute schizophrenia is associated with cardiac autonomic dysfunction, 314 unmedicated patients with acute schizophrenia and 409 healthy volunteers, aged 18-65 years, were recruited for a case-control analysis. The severity of schizophrenia symptoms was assessed with the Positive and Negative Syndrome Scale. Cardiac autonomic function was evaluated by measuring heart rate variability (HRV) parameters during the supine-standing-supine test. Frequency-domain indices of HRV were obtained.

RESULTS

Unmedicated patients with acute schizophrenia consistently exhibited reduced mean RR interval and HRV levels in a supine rest and standing position compared with healthy volunteers. The severity of psychopathology, in particular positive symptoms, was negatively correlated with cardiac vagal control.

CONCLUSION

These data suggest that acute schizophrenia is accompanied by cardiac autonomic dysregulation. In view of the higher risk for cardiac complications in these patients, one might also consider the antipsychotic treatment in favour of improving cardiac autonomic modulation. Further studies using larger patient groups and controlled therapeutics may better understand the influence of antipsychotic treatment on cardiac autonomic regulation in schizophrenia.

Enhanced spectral analysis of blood flow during post-occlusive reactive hyperaemia test in different tissue depths

The objective of this study was to investigate the impairment of microcirculation in schizophrenic patients by means of spectral analysis of blood flow signals and to determine if microcirculation is unequally altered in different tissue depths. Furthermore, the impact of gender and age on the spectral parameters of the Laser Doppler Flowmetry (LDF) signal in healthy and diseased microcirculation are to be analysed. The segmented spectral analysis (SSA) algorithm was applied to LDF signals of a provoked post-ischemic stage and compared to the traditional total spectral analysis, hypothesizing that SSA reveals more detailed information on the dynamic behaviour of the blood flow. 15 healthy subjects (CON, mean age 32.4 years) and 15 patients (PAT, mean age 33.0 years) were enrolled. Spectral analysis was performed on two LDF signals at a depth of 2mm and 6-8mm. Features in five frequency subintervals were determined. Our results indicate that microcirculation is strongly impaired in patients. SSA of blood flow revealed differences between CON and PAT in all three frequency intervals referring to local vasomotion (endothelial p=0.03; sympathetic p=0.02, myogenic p=0.03) as well as the respiratory (p=0.02) and cardiac (p=0.006) bands in the deeper tissue. In contrast, in the near-surface tissue only the endothelial (p=0.006) and cardiac (p=0.006) components were altered. Furthermore, SSA determined a gender- and age dependency regarding blood flow. In conclusion, we could demonstrate that microcirculation in schizophrenic patients is significantly impaired, depending on its location in the near-surface skin or in the superficial muscle tissue. These alterations of microcirculation are more pronounced in the deeper tissue depth of about 6-8mm and are influenced by gender and age.

Impact of antipsychotics and anticholinergics on autonomic modulation in patients with schizophrenia

Antipsychotics are associated with cardiovascular risk, but the relationship between their anticholinergic properties and cardiac function is not clear. We hypothesize that antipsychotics with a high muscarinic affinity (HMA) may reduce parasympathetic modulation, which should be observable by means of heart rate variability (HRV) measurement. We also assume that anticholinergics, which are commonly used in patients with schizophrenia to treat drug-induced parkinsonism, interact with antipsychotics, and this may also affect HRV. Fifty-five patients with schizophrenia were recruited into this study. Twenty-eight subjects used antipsychotics with an HMA and 27 subjects used antipsychotics with a low muscarinic affinity (LMA). Heart rate variability values between the patients on antipsychotics with HMA and those on antipsychotics with LMA were compared. Correlation and regression analysis were then performed to clarify the relationship between HMA, LMA, and HRV. The influence of anticholinergics was also assessed by correlation analysis. The HMA group showed significantly reduced low-frequency (LF) power, high-frequency (HF) power, total power (TP), and normalized LF (LF%) than the LMA group. Regression analysis supported the hypothesis that muscarinic affinity was related to LF (β = -0.447; P < 0.001), HF (β = -0.390; P = 0.002), and TP (β = -0.399; P = 0.001). The interaction between LMA and anticholinergic use also influenced LF% (β = 0.326; P = 0.006). In the LMA group, the use of anticholinergics was positively correlated with LF% and LF/HF. In the HMA group, after exclusion of the patients using anticholinergics, the equivalent dose of antipsychotics showed a negative correlation with HF. Our results suggest that the muscarinic affinity of antipsychotics affects both sympathetic and parasympathetic modulation and that anticholinergics interact with antipsychotics to influence HRV.

Assessing spontaneous baroreflex in aged with pulse-pulse intervals and pulse amplitudes

Cardiac autonomic dysfunction is a serious condition in the elder subjects. Baroreflex sensitivity (BRS) by measuring pulse intervals and blood pressure has been proven as an effective indicator. This paper proposes a novel index by substitution blood pressure with amplitudes of pressure pulse. We recruited 61 subjects divided into two groups: healthy young subjects (Group1, n=33), healthy elders (Group2, n=28). The wrist pulse pressures of each subject were measured for 5 minutes to obtain pulse-pulse intervals and amplitudes then applied within the spontaneous sequence technique to calculate the pulse-pulse interval and amplitude ratio (PAR). We verified the reproducibility of PAR and agreement with spectral analysis of heart rate variability in group1 participants. We discovered significant differences between different groups in PAR (Group1 vs. Group2: 0.90 ± 0.42 vs. 0.62 ± 0.27, P=0.010). In contrast with measurements of BRS, this study proposes a simple approach without the necessity of blood pressure calibration or professional expertise to conduct measurements, thereby providing a convenient method for assessing autonomic function at home.

May salivary alpha-amylase level be a useful tool for assessment of the severity of schizophrenia and evaluation of therapy? A case report

Background. Previous studies suggested dysfunction of the autonomic nervous system (ANS) in schizophrenia patients, but the mechanism remains unclear. Recently, the measurement of salivary alpha-amylase (sAA) has been considered a useful tool for evaluating ANS, especially the sympathoadrenal medullary system. Furthermore, there was a report that patients with schizophrenia showed much higher sAA level than normal controls. Methods. We present the case of a 51-year-old female with catatonic schizophrenia. She needed the treatment of electroconvulsive therapy (ECT). We evaluated her sAA level and her psychiatric symptoms during the treatment. Results. Before ECT treatment, she showed high sAA level. Her sAA level decreased during the course of ECT, and this attenuation was accompanied by improvement of schizophrenic symptoms. Conclusion. We consider that measurement of the sAA level may be one of the useful biological markers for assessment of psychotic state and efficacy of treatment in patients with schizophrenia.

Dysregulation of the autonomous nervous system in patients with temporomandibular disorder: a pupillometric study

The role of the autonomic nervous system (ANS) was recently investigated in Temporomandibular disorders (TMD). Several authors argue that in subjects with TMD there is a dysregulation of ANS. Recent literature support that Pupillometry is a simple non-invasive tool to study ANS. The aim of this study was to investigate the relationship between TMD and ANS activity using pupillometry recording in Infrared light at rest Mandible Position (RP); Infrared light at Forced Habitual Occlusion (FHO); Yellow-green light at RP; Yellow-green light at FHO. Forty female subjects were enrolled: 20 case patients showed TMD based on the Research Diagnostic Criteria for TMD, and 20 control patients, aged matched, had no signs or symptoms of TMD. Statistical analysis was performed on average pupil size. Ratio between pupil size in FHO and RP (FHO/RP ratio) and yellow-green and infrared (light/darkness ratio) lighting were carried out. Within group differences of pupil size and of “ratio” were analyzed using a paired t test, while differences of pupil size between groups were tested using an unpaired t test. Statistical comparisons between groups showed no significant differences of absolute values of pupil dimension in RP and FHO, both in yellow-green and in infrared lighting. In addition, there were no significant differences within groups comparing RP and FHO in yellow-green light. In within group comparison of pupil size, differences between RP and FHO were significant in infrared conditions. Control subjects increased, whereas TMD patients decreased pupil size at FHO in infrared lightening. FHO/RP ratio in darkness and light/darkness ratio in RP were significantly different between groups. Taken together, these data suggest that TMD subjects have an impairment of the sympathetic-adrenergic component of the ANS to be activated under stress. The present study provides preliminary pupillometric data confirming that adrenergic function is dysregulated in patients with TMD.

Simultaneously measured pupillary light reflex and heart rate variability in healthy children

We investigated the potential inter-relationship between two measures of autonomic nervous system: pupillary light reflex (PLR) and heart rate variability (HRV), in healthy children of 8-16 years old. PLR was measured at both dark- and light-adapted conditions with various stimulation intensities. Simultaneously measured HRV was obtained in five different PLR testing phases: before PLR test, light-adapted PLR test, dark adaptation, dark-adapted PLR test and after PLR test. The frequency domain HRV parameters measured during the PLR test were significantly different from those measured during rest. Both the regression analysis and factor analysis indicated that PLR and HRV parameters were not correlated, which suggests that they may provide complementary assessment of different aspects of the overall autonomic nervous system.

The phrenic component of acute schizophrenia--a name and its physiological reality

Decreased heart rate variability (HRV) was shown for unmedicated patients with schizophrenia and their first-degree relatives, implying genetic associations. This is known to be an important risk factor for increased cardiac mortality in other diseases. The interaction of cardio-respiratory function and respiratory physiology has never been investigated in the disease although it might be closely related to the pattern of autonomic dysfunction. We hypothesized that increased breathing rates and reduced cardio-respiratory coupling in patients with acute schizophrenia would be associated with low vagal function. We assessed variability of breathing rates and depth, HRV and cardio-respiratory coupling in patients, their first-degree relatives and controls at rest. Control subjects were investigated a second time by means of a stress task to identify stress-related changes of cardio-respiratory function. A total of 73 subjects were investigated, consisting of 23 unmedicated patients, 20 healthy, first-degree relatives and 30 control subjects matched for age, gender, smoking and physical fitness. The LifeShirt®, a multi-function ambulatory device, was used for data recording (30 minutes). Patients breathe significantly faster (p<.001) and shallower (p<.001) than controls most pronouncedly during exhalation. Patients' breathing is characterized by a significantly increased amount of middle- (p<.001), high- (p<.001), and very high frequency fluctuations (p<.001). These measures correlated positively with positive symptoms as assessed by the PANSS scale (e.g., middle frequency: r = 521; p<.01). Cardio-respiratory coupling was reduced in patients only, while HRV was decreased in patients and healthy relatives in comparison to controls. Respiratory alterations might reflect arousal in acutely ill patients, which is supported by comparable physiological changes in healthy subjects during stress. Future research needs to further investigate these findings with respect to their physiological consequences for patients. These results are invaluable for researchers studying changes of biological signals prone to the influence of breathing rate and rhythm (e.g., functional imaging).

Autonomic modulation and health-related quality of life among schizophrenic patients treated with non-intensive case management

BACKGROUND

Schizophrenia is associated with autonomic dysfunction and this may increase cardiovascular mortality. Past studies on autonomic modulation of schizophrenic patients focused on inpatients rather than individuals in a community setting, especially those receiving non-intensive case management (non-ICM). Besides, autonomic modulation and its association with health-related quality of life (HRQoL) in this population remain unexplored.

METHODS

A total of 25 schizophrenic patients treated by non-ICM and 40 healthy volunteers were matched by age, gender and body mass index; smokers were excluded. Between the two groups, we compared the individuals' 5 min resting assessments of heart rate variability and their HRQoL, which was measured using EuroQoL-5D (EQ-5D). Patients with schizophrenia were assessed for psychopathology using the Positive and Negative Syndrome Scale for Schizophrenia (PANSS). We examined the relationship between heart rate variability measurements, HRQoL scores, PANSS scores, and other clinical variables among the schizophrenic patients treated by non-ICM.

RESULTS

Compared to the controls, patients with schizophrenia showed a significant impairment of autonomic modulation and a worse HRQoL. Cardiovagal dysfunction among the schizophrenic patients could be predicted independently based on lower educational level and more negative symptoms. Sympathetic predominance was directly associated with anticholinergics use and EQ-5D using a visual analogue scale (EQ-VAS).

CONCLUSION

Patients with schizophrenia treated by non-ICM show a significant impairment of their autonomic function and HRQoL compared to the controls. Since the sympathovagal dysfunction is associated with more negative symptoms or higher VAS score, the treatment of the negative symptoms as well as the monitoring of HRQoL might help to manage cardiovascular risk among these individuals. In addition, EQ-VAS scores must be interpreted more cautiously in such a population.

The Deceleration Capacity - a New Measure of Heart Rate Variability Evaluated in Patients With Schizophrenia and Antipsychotic Treatment

Background

Schizophrenia is associated with increased cardiac mortality. A disturbed autonomic modulation of heart rate (HR) has been described in patients with schizophrenia in whom antipsychotic medication may represent an additional cardiac risk. The novel measure deceleration capacity (DC) of heart rate predicts cardiac mortality in patients with cardiovascular illnesses. The aim of the present paper was to calculate DC in patients with schizophrenia and to compare this measure with established parameters of heart rate variability (HRV).

Methods

HRV and DC were calculated in 24-hour electrocardiogram (ECG) recordings of 20 unmedicated, 40 medicated patients with schizophrenia and 40 controls. As activity has a major influence on HRV, 4-hour periods of “sleep-” and “wake-” ECG were evaluated as additional parameters. Actigraphy was used to ensure comparable levels of activity in patients and controls.

Results

The DC as well as the other established HRV measures were not significantly different comparing unmedicated patients with schizophrenia to healthy controls. However, medicated patients showed a significant reduction of DC calculated from ECG recordings during 4 hour over night periods.

Conclusion

Calculation of DC might contribute to a better monitoring and identification of an increased risk of cardiac mortality in patients with schizophrenia undergoing antipsychotic treatment.

Peripheral endothelial dysfunction in patients suffering from acute schizophrenia: a potential marker for cardiovascular morbidity?

Patients suffering from schizophrenia have an increased standardized ratio for cardiovascular mortality compared to the general population. Endothelial function was identified as a prominent parameter for cardiac risk stratification in patients with heart disease. Here, we aimed to analyze the reactivity of the microcirculation applying the post-occlusive reactive hyperemia (PORH) test and spectral analysis of skin vasomotion as markers of endothelial function. We investigated 21 unmedicated patients suffering from paranoid schizophrenia as well as 21 matched controls. The capillary blood flow was assessed on the right forearm after compression of the brachial artery. Parameters of PORH such as time to peak (TP) or PORH index were calculated. In addition, spectral analysis of skin vasomotion was performed and five frequency bands (endothelial, sympathetic, vascular myogenic, respiratory and heart beat activity) were studied. Psychotic symptoms were quantified using the Positive and Negative Syndrome Scale (PANSS) and correlated to the parameters obtained. We report a blunted hyperemic response in patients after occlusion of the brachial artery indicated by significantly increased TP and decreased PORH indices. In contrast, vasomotion as investigated by spectral analysis of skin flow was rather sparsely altered showing differences at rest for the sympathetic and cardiac components only. Our results are suggestive of peripheral endothelial dysfunction in unmedicated patients suffering from schizophrenia. Future, prospective studies should address the relation of endothelial dysfunction to cardiac morbidity in patients with schizophrenia.

Dynamic microvascular blood flow analysis during post-occlusive reactive hyperemia test in patients with schizophrenia

Patients suffering from schizophrenia have an increased mortality risk due to cardiovascular events. Recently the analysis of peripheral circulation has revealed interesting results in the study of vascular pathological conditions assuming that the state of microcirculation of the skin is at least partly representative for the constitution of other vascular beds including those of the cardiac muscle and arteries. The objective of this study was to investigate the microcirculation in patients with acute schizophrenia (PAT, n = 15, mean age 33.0 years, 7 male, 8 female) to identify whether spectral features from blood flow signals derived through laser Doppler spectrometry are significantly altered compared to healthy subjects (CON, n = 15, mean age 32.4 years, 7 male, 8 female) by means of the post-occlusive reactive hyperemia test. It was also explored if a segmentation of the post-ischemic stage can disclose more detailed and additional information about the dynamic behavior of the blood flow during hyperemic response. For this reason, time-frequency analyses were performed to observe the course of the blood flow frequency components over time. Our results indicate significant differences in the patients group, already detectable under baseline conditions but also in the hyperemic phase. The main modifications affect the respiratory (p = 0.006) as well as the cardiac (p = 0.001) activity. It was further shown that the application of a segmented analysis of the post-ischemic state considerably improves the differentiation between both groups. Only with the introduced segmentation algorithm using a window length of 2048 samples and a shift of 128 and 256 samples we could demonstrate influences of the disease on the endothelial (p = 0.029), the sympathetic (p = 0.019) and the myogenic (p = 0.029) mechanisms. These information provide further insights into the appearance of schizophrenia and could lead to an improvement of the patients' treatment to avoid the occurrence of cardiovascular events.

Gastric dysmotility in healthy first-degree relatives of patients with schizophrenia

Gastric dysmotility has been reported in patients suffering from major depression or schizophrenia. An increased sympathetic activity modulating the gastric pacemaker located in the antrum of the stomach has been suggested as the underlying pathology. Similar to patients suffering from schizophrenia, their first-degree relatives showed alterations in cardiac autonomic modulation. Here we aimed to investigate gastric myoelectrical activity in healthy relatives of patients suffering from paranoid schizophrenia. Electrogastrography (EGG) was performed before and after test meal ingestion in 20 patients with paranoid schizophrenia, 20 of their first-degree relatives and 20 healthy matched controls. Autonomic and abdominal symptoms were assessed by the autonomic symptom score as previously reported. Autonomic parameters were correlated with the positive and negative syndrome scale (PANSS). Only minimal differences were observed before test meal ingestion between relatives and controls. In contrast, after test meal ingestion we observed a significantly increased tachygastria within the signal of the gastric pacemaker in relatives compared to controls, whereas normogastria was reduced. Significant difference between relatives and controls were also found for postprandial ICDF (instability coefficient of dominant frequency) and slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in relatives. Between relatives and patients just a difference for ICDP (instability coefficient of dominant power) was observed. After stimulation of the enteric nervous system we have observed an increased sympathetic modulation in first-degree relatives of patients suffering from schizophrenia. This result adds evidence to an ongoing debate on the genetic influence of autonomic dysfunction in the disease.

Autonomic dysfunction in unaffected first-degree relatives of patients suffering from schizophrenia

Recent studies revealed cardiac autonomic dysfunction in patients with acute schizophrenia, which appears to be mainly related to reduced vagal and increased sympathetic modulation. To understand the significance of cardiac autonomic function in patients with schizophrenia, we extended these studies to relatives of patients. In this study, we assessed cardiac autonomic modulation in healthy first-degree relatives of patients with schizophrenia (n = 36) to investigate a putative genetic influence. Data were compared with control subjects matched for age, gender, and physical activity as well as to patients suffering from schizophrenia. First-degree relatives showed an attenuated, yet identical pattern in autonomic dysfunction as patients with decreased vagal modulation of heart rate, decreased baroreflex sensitivity, but no difference in blood pressure variability could be detected. The patients' relatives also showed a similar pattern in regards to QT variability. In addition, the subgroup comparison of offspring vs. siblings showed a significant difference in heart rate variability suggesting a higher degree of heritability in offspring. In conclusion, the pattern of autonomic dysfunction seen in patients and relatives might indicate underlying disease-inherent genetic vulnerability, especially because autonomic parameters are heritable. In addition, these findings may be of value to identify the high-risk group of patients' relatives in regards to serious cardiovascular events so that early preventive measures can be taken.

Changes in heart rate dynamics of patients with schizophrenia treated with risperidone

Neurocardiac dysregulation has been reported in schizophrenia. Indices of heart rate variability (HRV) are useful in assessing the status of cardiac autonomic regulation. We explored within-subject changes in HRV indices in acutely ill patients with schizophrenia treated with risperidone. Sixteen medication-naïve or medication-free patients with DSM-IV schizophrenia completed electrocardiogram (ECG) assessments at baseline and after six weeks of treatment with risperidone. Indices of HRV were extracted from 5-min resting ECG recordings and compared to those obtained from control subjects matched for age and gender. Psychiatric and drug-induced extrapyramidal symptoms were assessed by the Positive and Negative Syndrome Scale (PANSS) and the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS). In comparison with matched controls, patients with acute schizophrenia showed lower values of time-domain measures, lower high-frequency power (HF) and a higher ratio of low to high frequency (LF/HF). In the within-subject analyses, a significant decrease in LF/HF was associated with risperidone treatment. In addition, LF/HF, which initially co-clustered with clinical variables, congregated with other HRV measures after the six-week risperidone treatment. These results indicate that, in the therapeutic process, risperidone treatment may exert a beneficial influence on the sympathovagal imbalance in acute schizophrenia.

High salivary alpha-amylase levels in patients with schizophrenia: A pilot study

Previous studies have demonstrated the autonomic dysregulation in patients with schizophrenia using electrophysiological methods, such as electrodermal measures and heart rate analysis. Several theories have been proposed to explain the underlying mechanisms of schizophrenia and its autonomic function. Recently, the measurement of salivary alpha-amylase has been considered to be a useful tool for evaluating the sympathetic-adrenal-medullary (SAM) system. Psychosocial stress increases the release of salivary alpha-amylase. Although some studies have evaluated salivary alpha-amylase under psychosocial stress, no studies have demonstrated the change in the salivary alpha-amylase (sAA) activity level in schizophrenic patients. We examined the relationship between sAA level and psychiatric state in patients with schizophrenia (n=54) using a portable and rapid hand-held monitor to investigate sAA. The sAA activity in the patients was significantly higher than that in the control subjects (n=55) (p<0.01). The correlation between amylase level and psychiatric symptoms was highly significant (r=0.37, p<0.01). These findings indicate that higher increases in sAA may indicate severe psychiatric symptoms. These results indicate a predominant role of the sympathetic nervous system in the secretion of sAA, together with parasympathetic withdrawal, under psychosocial stress.

Reduced cardio-respiratory coupling indicates suppression of vagal activity in healthy relatives of patients with schizophrenia

Previous studies have observed reduced vagal modulation in patients with acute schizophrenia and their first-degree relatives, thus suggesting a genetic predisposition. To investigate vagal modulation, we analyzed the coupling between heart rate and breathing as a putative measure of central autonomic function in 19 patients, 19 of their relatives and 19 matched control subjects. The interaction of heart rate and breathing was investigated in all groups applying the non-linear parameter cross-ApEn, indicating the asynchrony between both time series. In addition, measures of the time and frequency domain of heart rate variability (HRV) were obtained. The main finding of our study is a significantly increased cross-ApEn value, indicating reduced central vagal modulation both in relatives and patients suffering from schizophrenia. Non-linear measures of HRV proved to more sensitively differentiate relatives from control subjects. Furthermore, we observed a correlation between psychopathology and breathing, indicating that positive symptoms are associated with a higher degree of regularity in the breathing pattern. Our results suggest that autonomic dysfunction previously described for patients suffering from schizophrenia is also present in first-degree relatives. This might relate to changes of brainstem activity in patients and relatives, and a common genetic background in patients and their family members can be assumed.