Heart rate variability in patients with somatic symptom disorders and functional somatic syndromes: a systematic review and meta-analysis, 2020, Cheng

Dolphin

Dolphin

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Chronic fatigue syndrome is mentioned as one of the keywords so I thought I would post it in this forum

https://www.sciencedirect.com/science/article/abs/pii/S0149763419309868

Neuroscience & Biobehavioral Reviews
Available online 14 February 2020


Review article
Heart rate variability in patients with somatic symptom disorders and functional somatic syndromes: a systematic review and meta-analysis
Author links open overlay panelYing-ChihChengabcYu-ChenHuangcdeWei-LiehHuangfghi
https://doi.org/10.1016/j.neubiorev.2020.02.007Get rights and content

Highlights


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The whole FSSs/SSDs patients showed significantly lower baseline HRV than healthy subjects

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After separating CFS, FM, IBS, and SSDs, the significant inter-group differences of baseline HRV persisted.

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FSSs/SSDs patients had significantly lower HRV reactivity than healthy controls.

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FSSs/SSDs patients had significantly lower total variability, parasympathetic specific indices, and higher LF/HF than healthy population.



Abstract
This research is aimed to systematically review heart rate variability (HRV) findings of functional somatic syndrome (FSSs) and somatic symptom disorders (SSDs), and to compare the HRV values between FSSs/SSDs patients and healthy individuals. We included clinical studies assessing HRV (including baseline HRV and HRV reactivity) in FSSs/SSDs and healthy participants. We searched PubMed, Embase, PsycINFO, MEDLINE, and Web of Science databases from the earliest available date to June 2019. Eighty-five studies comprising 3242 FSSs/SSDs patients and 2321 controls were included in the main meta-analysis; the baseline HRV value was significantly lower compared to healthy individuals (Hedges’g, -0.43; 95% CI, -0.54 to -0.30; p < .001), with the largest effect size in fibromyalgia patients. A significant lower HRV was also found for total variability (Hedges’g, -0.56; 95% CI, -0.77 to -0.36) and specific parasympathetic indices (Hedges’g, -0.41, 95% CI; -0.54 to -0.30). HRV reactivity was significantly lower in FSSs/SSDs patients (Hedges’g, -0.42; 95% CI, -0.64 to -0.20). Our results support the notion that FSSs/SSDs patients have significantly lower HRV than healthy individuals.

Keywords
Heart rate variability
somatic symptom disorder
chronic fatigue syndrome
fibromyalgia
irritable bowel syndrome

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This is a systematic review of studies on HRV in 4 different patient populations: CFS, fibromyalgia, IBS, functional somatic syndromes & somatic symptom disorders. Here's the list of studies they looked at for the CFS group.

medherb1.png
Figure caption said:
Forest plot for the comparison of baseline HRV between FSSs/SSDs patients and healthy individuals. The differences between FSSs/SSDs patients as a whole and their healthy counterparts, CFS patients and their healthy counterparts, FM patients and their healthy counterparts, IBS patients and their healthy counterparts, SSDs patients and their healthy counterparts are all significant.
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Anyway, per the authors' paragraph about the limitations of the underlying studies (pp. 12-13), this review is pretty much useless. Props to them for being honest about it. Bolding and spacing mine in the quote below.
Several limitations of our analysis should be mentioned.
First, the heterogeneity of subjects and study design is the most important issue. In the diagnostic aspect, FM, CFS, IBS, and SSDs all cross several different diagnostic systems.This causes the homogeneity of the studied population to reduce. Furthermore, not all of the HRV measurements of the studies were based on the same protocol. The most obvious heterogeneity lies with the HRV reactivity; the methods of performing biological and psychological challenges are quite different. Therefore, the results of HRV reactivity should be interpreted cautiously.
Second, some analyses revealed that publication bias cannot be ruled out, or did not pass sensitivity analysis. This means the data reporting and some outliers may have influenced the results.
Third, some variables which may have influenced HRV cannot be incorporated, such as the level of depression and anxiety in subjects. Other meta-analyses have disclosed that negative emotionsimpact HRV values(Alvares et al., 2016), and that comorbid anxiety/depression is quite common in FSSs/SSDs patients(Huang et al., 2016b; Leiknes et al., 2010). The chronicity of FSSs/SSDs is associated with comorbid anxiety/depression; but most of the included studies did not report the duration of illness, causing this factor unable to be analyzed in meta-regression (Luo et al., 2014). Besides, most included studies did not have active control designs (e.g., a group with anxiety/depression but without FSSs/SSDs). These problems may cause the influence of anxiety/depression on HRV to be underestimated. Many physical comorbidities (such as cardiovascular diseases and diabetes mellitus) may affect HRV, but they could not be corrected in our analysis because lacking of detailed data.
Fourth, FSSs/SSDs lack clearly defined biomarkers and hence have relatively low diagnostic reliability (Goldenberg, 2014). The vague nature of FSSs/SSDs diagnoses is a potential confound for this kind of studies. However, this issue also implies that finding a suitable biomarker (such as HRV in the present analysis) is clinically important for the diagnosis of FSSs/SSDs.
Finally, publication bias in some analyses was noted. The possibility that non-significant HRV differences in FSSs/SSDs and healthy subjects were underreported cannot be excluded.
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just publishing for the sake of it the academic industry is totally unfit for any purpose . I loathe so called meta analysis because you cannot trust the data from a lot of papers it actually takes real time and effort to weed out the vast amount of tripe that has been published
 
My understanding is the low HRV is associated with a number of phsyiological ailments.

To say they are cherry picking to acquire some pseudo bio legitimacy appears to be an understatement.
 
The problem in general is HRV is a very non-specific marker. One of the primary associations of HRV is with fitness, so it is not surprising that chronically ill individuals would have slightly lower HRV, even if there are zero other reasons for association with such illnesses.
 
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