A Randomized Controlled Biofeedback Intervention Study On Heart Rate Variability In Unemployed Subjects

Background: Unemployment is a chronic stressor which is associated with higher levels of impaired physical and mental wellbeing, e.g. reduced heart rate variability (HRV) and decline in self-esteem and self-efficacy. The present study investigated the effectivity of a HRV-biofeedback-training in increasing HRV and general selfefficacy. Method: A total of n = 22 unemployed individuals with adjustment disorder participated in this study [14 females, mean ages 42.53 ± 8.88 years]. All participants performed randomized the “stress tests” for heart rate (HR) and HRV assessment: timed breathing, d2-attention-stress-test and math-test drawn from the Trier Social Stress Test (TSST). Four sessions HRV-biofeedback à 20 min within 2 weeks were administered. HR and HRV were assessed before and after biofeedback training. ECG preprocessing and analysis were performed with the Stressball software program (BioSign GmbH, Ottenhofen, Germany). The RMSSD time domain measure was calculated as HRV index. Clinical outcome measures were the ADNM total score and the general self-efficacy scale (GSE). Results: Participants were well matched in terms of demographic and clinical characteristics. ANOVA didn’t demonstrate significant time x group interaction effects neither for HRV parameters (HR, RMSSD) nor for psychological parameters (ADNM, GSE). Conclusion: Our findings do not indicate that HRV-biofeedback can increase HRV nor general self-efficacy in unemployed subjects with adjustment disorder. Implications for future studies are discussed. DOI : 10.14302/issn.2476-1710.JDT-16-1332 Corresponding Author : Katja Petrowski, Department of Psychotherapy and Psychosomatic Medicine, Dresden, Germany University Hospital Carl Gustav Carus Dresden, Technische Universitaet Dresden, Fetscherstr. 74, 01307 Dresden, Germany. Phone: 0049 351 4583634, Fax: 0049 351 2636268, Email: katja.petrowski@tu-dresden.d

The aim of the present study is to evaluate the effectivity of HRV-biofeedback in normalizing HRV (increased RMSSD, decreased mean HR) and increasing ratings on self-efficacy in a sample of unemployed subjects.

Study Participants
The audio disc and an instruction paper to facilitate at-home practicing as well as a protocol to minute all exercises.
Both the biofeedback and waiting control group were tested again for HRV assessment with the stress-tests after cessation of the biofeedback training.

Clinical Assessments
The individual's ability to adjust to job loss was evaluated by assessing the manifestation of an adjustment disorder using the 29-item-self-report questionnaire adjustment disorder new module (ADNM) which consists of two parts [57]. In part one, the respondent is asked to report stressful life events out of seven categories (severe illness, family conflicts, divorce/separation, conflicts with colleagues/at work, illness of relative, financial problems, leaving working life) and to decide which one was the most distressing.
The second part involves the diagnostic criteria for an adjustment disorder belonging to the core symptoms of intrusion, avoidance and failure to adapt and the subtype criteria (anxiety, depressed mood, impulse disturbance). Part two is rated on a 4-point Likert-scale.
Two out of three of the core anxiety or depressive symptoms have to be present for subtype manifestation.
To differentiate psychological and physical impairment the Complaint List (BL) [58] was used which consists of 24 items with a four-point rating scale (range 0-72). Severity of depressive symptoms was selfevaluated using the Beck-Depression-Inventory II (BDI-II) [59,60]. The respondent is asked to choose the most appropriate alternative out of 21 items matching the DSM-IV major depression criteria that best describes the way he or she felt during the past two weeks (range 0-63). Subjects' sense of personal competence to deal effectively with stressful situations was evaluated with the general self-efficacy scale (GSE) [61]. This self-report instrument contains 10 items which are rated on a four-point Likert scale (range 10-40).

Heart Rate Variability
The were able to show that the RMSSD reliably represented the HRV even in short (1 min) and ultra-short (10 sec) recordings [63].

Statistical Analysis
Group differences in sociodemographic and clinical characteristics were tested using univariate

Results
The group's characteristics are described in report on the reliability of the RMSSD for HRV assessment from recording of 1 minute and even of 10 seconds [63]. Hence the present recording duration appears to be sufficiently reliable.
There are some limitations that should be noted. This may be too short to detect adaptation in the autonomous nervous system. Future studies should extend the intervention interval.
In conclusion, we found no significant effect of a 2-week HRV-biofeedback-training. Thus, we didn't find evidence to support HRV-biofeedback-training in the present form to be an efficacious intervention to increase HRV and self-efficacy. Future studies should include a control group and extend the intervention interval.

Acknowledgements
The present work was part of a graduate thesis.

Conflict of Interest
All authors declare that they have no conflicts of interest.

Ethical Approval
All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsiniki declaration and its later amendments or comparable ethical standards. Note. Pre = before the biofeedback training; Post = after the biofeedback training; HR = heart rate; RMSSD = square root of successive R-R interval differences. RMSSD was log10 transformed.

Informed Consent
Informed consent was obtained from all individual participants included in the study.   Characteristics of resonance in heart rate variability stimulated by biofeedback.