Negative Affectivity, Depression, and Resting Heart Rate Variability (HRV) as Possible Moderators of Endogenous Pain Modulation in Functional Somatic Syndromes.

Maaike Van Den Houte,Jozef De Bie,Ilse Van Diest,Lukas Van Oudenhove,Omer Van Den Bergh,Katleen Bogaerts,Philippe Persoons

doi:10.3389/fpsyg.2018.00275

Maaike Van Den Houte, Jozef De Bie + Show 5 more

Open Access

https://doi.org/10.3389/fpsyg.2018.00275

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Abstract

Background: Several studies have shown that patients with functional somatic syndromes (FSS) have, on average, deficient endogenous pain modulation (EPM), as well as elevated levels of negative affectivity (NA) and high comorbidity with depression and reduced resting heart rate variability (HRV) compared to healthy controls (HC). The goals of this study were (1) to replicate these findings and (2) to investigate the moderating role of NA, depression, and resting HRV in EPM efficiency within a patient group with fibromyalgia and/or chronic fatigue syndrome (CFS). Resting HRV was quantified as the root mean square of successive differences between inter-beat intervals (RMSSD) in rest, a vagally mediated time domain measure of HRV.Methods: Seventy-eight patients with fibromyalgia and/or CFS and 33 HC completed a counter-irritation paradigm as a measure of EPM efficiency. Participants rated the painfulness of electrocutaneous stimuli (of individually calibrated intensity) on the ankle before (baseline phase), during (counter-irritation phase) and after (recovery phase) the application of a cold pain stimulus on the forearm. A larger reduction in pain in the counter-irritation phase compared to the baseline phase reflects a more efficient EPM.Results: In contrast to our expectations, there was no difference between pain ratings in the baseline compared to counter-irritation phase for both patients and HC. Therefore, reliable conclusions on the moderating effect of NA, depression, and RMSSD could not be made. Surprisingly, patients reported more pain in the recovery compared to the counter-irritation and baseline phase, while HC did not. This latter effect was more pronounced in patients with comorbid depression, patients who rated the painfulness of the counter-irritation stimulus as high and patients who rated the painfulness of the electrocutaneous stimuli as low. We did not manage to successfully replicate the counter-irritation effect in HC or FSS patients. Therefore, no valid conclusions on the association between RMSSD, depression, NA and EPM efficiency can be drawn from this study. Possible reasons for the lack of the counter-irritation effect are discussed.

Highlights

Endogenous pain modulation refers to the internal modification of pain signals in order to accommodate the body’s current and future needs (Bourne et al, 2014)
Data of the counter-irritation paradigm could not be used for 7 healthy controls (HC) and 2 patients due to technical malfunctions
The final sample consisted of 78 patients and 33 HC

Summary

Introduction

Endogenous pain modulation refers to the internal modification of pain signals in order to accommodate the body’s current and future needs (Bourne et al, 2014). One example of EPM is DNIC, where neural responding to noxious stimulation in one area of the body is reduced by the application of noxious stimulation in another area of the body (“pain inhibits pain”; Le Bars et al, 1979) In humans, this mechanism is tested and quantified with counter-irritation paradigms, referred to as conditioned pain modulation paradigms. EPM efficiency is defined as the difference in the physiological or subjective pain response to the test stimulus before versus during the application of the counter-irritation stimulus, with a larger reduction in painfulness of the test stimulus during counterirritation reflecting more efficient EPM Studies using these paradigms have established that on average EPM is less efficient in patients with chronic pain conditions (Lewis et al, 2012; Staud, 2012; Yarnitsky, 2015), and in patients with FSS, like irritable bowel syndrome (Wilder-Smith, 2011), fibromyalgia (Julien et al, 2005; Jensen et al, 2009), and CFS (Meeus et al, 2008). Resting HRV was quantified as the root mean square of successive differences between inter-beat intervals (RMSSD) in rest, a vagally mediated time domain measure of HRV

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