ReviewA systematic review on heart rate variability in Bulimia Nervosa
Introduction
Bulimia Nervosa (BN) is a serious mental illness with a lifetime prevalence of about 1% in the general population (Hudson et al., 2007). It is more commonly seen in females than in males (Hudson et al., 2007, Smink et al., 2012). Based on DSM-5 criteria, the lifetime prevalence for BN in females is estimated to be as high as 2.6% (Stice et al., 2013). Those affected engage in recurrent episodes of binge-eating and subsequent compensating behaviors, such as self-induced vomiting, abuse of laxatives, diuretics, or enemas, excessive exercising, and fasting (caloric restriction) (American Psychiatric Association, APA, 2013). Individuals with BN are characterized by an intense preoccupation with their body weight (APA, 2013).
Alterations in autonomic nervous system (ANS) function have previously been described in eating disorders (ED) (Faris et al., 2008). A convenient way to measure ANS function is the widely used recording of heart rate variability (HRV, Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology, 1996). Chronotropic control of the heart is achieved via the complex interplay of the sympathetic (SNS) and the parasympathetic (PNS) branches of the ANS. Heart rate (HR) is under tonic inhibitory control (PNS dominance over SNS influences) (Jose and Collison, 1970). While PNS modulation of the heart rate is fast (timescale in the order of milliseconds), SNS effects are much slower (Levy, 1997). Therefore, measures of HRV reflecting these fast changes provide a readily available, surrogate measure of cardiac vagal activity. The recording and analysis of the sequence of time intervals between adjacent heartbeats allows teasing out the relative contribution of the SNS and PNS, and thus represents a readily available measure of ANS function.
Recently, Mazurak et al. (2011) reviewed the association of ANS function indexed by HRV and Anorexia Nervosa (AN). They found the existing evidence to be inconclusive with the majority of studies reporting increased vagally-mediated HRV indicating PNS dominance, whilst others noted a dominance of the SNS (i.e., decreased vagally-mediated HRV), or no differences comparing HRV in AN patients to controls. To our knowledge the literature on HRV and BN has not been previously reviewed. While AN and BN share some commonalities, they both present distinct clinical entities, particularly in terms of patient personality. Both eating disorders tend to be characterized by obsessive-compulsiveness and perfectionism. However, AN display high restraint whereas BN is associated with marked impulsivity and borderline personality-characteristics such as emotional instability (Cassin and von Ranson, 2005). Furthermore, there are marked differences between AN and BN regarding their respective clinical presentation. AN is primarily characterized by self-imposed starvation (APA, 2013), which leads to physiological changes that are different from those associated with binge-purge behavior in BN, for instance with respect to resulting malnutrition and hormonal changes (Gualandi, 2013, Mitchell and Crow, 2006).
Both personality- and physiology-related differences may differentially affect ANS function. We, therefore, aimed to systematically review the current evidence on HRV in BN.
Section snippets
Systematic literature research and inclusion of studies
A systematic search of the literature in line with the ‘Preferred Reporting Items for Systematic Reviews and Meta-Analyses’ (PRISMA) statement (Moher et al., 2009) was performed in January 2015. Four databases (PubMed, World of Science, Scopus, and PsycInfo) were included and systematically searched for the terms ((heart rate variability) OR (respiratory sinus arrhythmia) OR (HRV)) AND eating disorder. The term ‘eating disorder’ was chosen instead of ‘bulimia’ to cover potential reporting of BN
Study selection
The initial literature research yielded 212 results across all four databases. After removing duplicates, abstracts of 133 articles were screened. At first, 15 studies were selected for inclusion based on the pre-defined criteria. Screening the reference lists of included papers revealed another 3 articles potentially eligible for inclusion, of which one – a review on the general psychophysiology of food craving and BN – was excluded, leaving a total of 17 full-texts published between 1989 and
Summary of findings
The present review aimed to summarize the current evidence on ANS dysfunction in patients with BN reflected by measures of HRV. The review revealed three major findings regarding (i) baseline differences on HRV comparing individuals with BN or symptoms characteristic for BN and controls, (ii) altered stress reactivity indexed by changes in HRV in those with BN, and (iii) the effects of treatment for BN reflected by changes in HRV.
First, a total of 14 studies investigated baseline differences in
Conflicts of interest
None.
Funding
This work was supported by a scholarship from the Studienstiftung des Deutschen Volkes (German National Scholarship Foundation) granted to SP for studies at the Department of Psychology, The Ohio State University.
Acknowledgements
JK and MK acknowledge the support of a travel grant by the Boehringer Ingelheim Fonds. JK is supported by a Physician-Scientist-Fellowship provided by the Medical School, University of Heidelberg, Germany.
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