Heart rate variability in patients with fibromyalgia and patients with chronic fatigue syndrome: a systematic review

Abstract:

OBJECTIVE: The goal of this systematic literature review is to determine whether there are differences and similarities in heart rate variability (HRV) between adult patients with fibromyalgia

(FM), chronic fatigue syndrome (CFS), and healthy pain-free control subjects.

METHODS: To obtain relevant articles, PubMed and Web of Knowledge were searched for case-control studies. Selection of the literature was based on selection criteria ascertaining studies with adult human patient groups comparing HRV. Risk of bias and levels of evidence were determined.

RESULTS: Sixteen case-control studies were included, 10 comparing FM patients to controls and 6 comparing CFS patients to controls. Methodological quality was moderate to good. Both time domain and frequency domain measurements were used. The majority of the researchers observed lower HRV in FM patients compared to healthy control persons, as well as increased sympathetic activity and a blunted autonomic response to stressors. Resistance training improved HRV in FM patients. In CFS patients HRV was only reduced during sleep.

CONCLUSION: FM patients show more HRV aberrances and indices of increased sympathetic activity. Increased sympathetic activity is only present in CFS patients at night. Since direct comparisons are lacking and some confounders have to be taken into account, further research is warranted. The role of pain and causality can be subject of further research, as well as therapy studies directed to reduced HRV.

© 2013 Elsevier Inc. All rights reserved.

Comment in

Source: Meeus M, Goubert D, De Backer F, Struyf F, Hermans L, Coppieters I, De Wandele I, Da Silva H, Calders P. Heart rate variability in patients with fibromyalgia and patients with chronic fatigue syndrome: a systematic review. Semin Arthritis Rheum. 2013 Oct;43(2):279-87. doi: 10.1016/j.semarthrit.2013.03.004. Epub 2013 Jul 6. https://www.ncbi.nlm.nih.gov/pubmed/23838093

 

The role of mitochondrial dysfunctions due to oxidative and nitrosative stress in the chronic pain or chronic fatigue syndromes and fibromyalgia patients: peripheral and central mechanisms as therapeutic targets?

Abstract:

INTRODUCTION: Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are characterized by persistent pain and fatigue. It is hypothesized that reactive oxygen species (ROS), caused by oxidative and nitrosative stress, by inhibiting mitochondrial function can be involved in muscle pain and central sensitization as typically seen in these patients.

AREAS COVERED: The current evidence regarding oxidative and nitrosative stress and mitochondrial dysfunction in CFS and FM is presented in relation to chronic widespread pain. Mitochondrial dysfunction has been shown in leukocytes of CFS patients and in muscle cells of FM patients, which could explain the muscle pain. Additionally, if mitochondrial dysfunction is also present in central neural cells, this could result in lowered ATP pools in neural cells, leading to generalized hypersensitivity and chronic widespread pain.

EXPERT OPINION: Increased ROS in CFS and FM, resulting in impaired mitochondrial function and reduced ATP in muscle and neural cells, might lead to chronic widespread pain in these patients. Therefore, targeting increased ROS by antioxidants and targeting the mitochondrial biogenesis could offer a solution for the chronic pain in these patients. The role of exercise therapy in restoring mitochondrial dysfunction remains to be explored, and provides important avenues for future research in this area.

 

Source: Meeus M, Nijs J, Hermans L, Goubert D, Calders P. The role of mitochondrial dysfunctions due to oxidative and nitrosative stress in the chronic pain or chronic fatigue syndromes and fibromyalgia patients: peripheral and central mechanisms as therapeutic targets? Expert Opin Ther Targets. 2013 Sep;17(9):1081-9. doi: 10.1517/14728222.2013.818657. Epub 2013 Jul 9. https://www.ncbi.nlm.nih.gov/pubmed/23834645

 

Discriminative validity of metabolic and workload measurements for identifying people with chronic fatigue syndrome

Abstract:

BACKGROUND: Reduced functional capacity and postexertion fatigue after physical activity are hallmark symptoms of chronic fatigue syndrome (CFS) and may even qualify for biomarker status. That these symptoms are often delayed may explain the equivocal results for clinical cardiopulmonary exercise testing in people with CFS. Test reproducibility in people who are healthy is well documented. Test reproducibility may not be achievable in people with CFS because of delayed symptoms.

OBJECTIVE: The objective of this study was to determine the discriminative validity of objective measurements obtained during cardiopulmonary exercise testing to distinguish participants with CFS from participants who did not have a disability but were sedentary.

DESIGN: A prospective cohort study was conducted.

METHODS: Gas exchange data, workloads, and related physiological parameters were compared in 51 participants with CFS and 10 control participants, all women, for 2 maximal exercise tests separated by 24 hours.

RESULTS: Multivariate analysis showed no significant differences between control participants and participants with CFS for test 1. However, for test 2, participants with CFS achieved significantly lower values for oxygen consumption and workload at peak exercise and at the ventilatory or anaerobic threshold. Follow-up classification analysis differentiated between groups with an overall accuracy of 95.1%.

LIMITATIONS: Only individuals with CFS who were able to undergo exercise testing were included in this study. Individuals who were unable to meet the criteria for maximal effort during both tests, were unable to complete the 2-day protocol, or displayed overt cardiovascular abnormalities were excluded from the analysis.

CONCLUSIONS: The lack of any significant differences between groups for the first exercise test would appear to support a deconditioning hypothesis for CFS symptoms. However, the results from the second test indicated the presence of CFS-related postexertion fatigue. It might be concluded that a single exercise test is insufficient to reliably demonstrate functional impairment in people with CFS. A second test might be necessary to document the atypical recovery response and protracted fatigue possibly unique to CFS, which can severely limit productivity in the home and workplace.

 

Source: Snell CR, Stevens SR, Davenport TE, Van Ness JM.Discriminative validity of metabolic and workload measurements for identifying people with chronic fatigue syndrome. Phys Ther. 2013 Nov;93(11):1484-92. doi: 10.2522/ptj.20110368. Epub 2013 Jun 27. https://academic.oup.com/ptj/article/93/11/1484/2735315/Discriminative-Validity-of-Metabolic-and-Workload?searchresult=1 (Full article)

 

Functional improvement is accompanied by reduced pain in adolescent chronic fatigue syndrome

Dear Editor:

Chronic fatigue syndrome (CFS) in adolescents is a complex, disabling condition characterized by severe and unexplained fatigue lasting more than 6 months, and often accompanied by pain symptoms. CFS in adolescents has substantial long-term consequences for educational and social development ⇓.

Chronic pain symptoms in CFS are disabling and affect physical and social functioning ⇓. Adult patients with CFS show lower pain thresholds than healthy subjects ⇓.

In a recently published review about pain in patients with CFS, Nijs et al. stated that pain appears to be one out of many symptoms related to central sensitization in adult CFS ⇓. They concluded that pain-catastrophizing thoughts and depression partly account for these pain symptoms. They suggested that it is important to understand the symptoms of pain in CFS better in order to assess whether it requires a specific treatment approach other than the main treatment focused on fatigue ⇓. Previous research has suggested to view the pathophysiological state of pain in CFS as an increase in the excitability and synaptic efficacy of neurons in central nociceptive pathways ⇓. We present original data on pain symptoms in adolescent CFS and their relation to treatment focused on fatigue.

We hypothesized that adolescent CFS patients have a lowered pain threshold at the time of diagnosis and that both pain experience and pain threshold improve when CFS is successfully treated.

You can read the rest of this article here: http://painmedicine.oxfordjournals.org/content/14/9/1435.long

 

Source: Nijhof SL, Priesterbach LP, Bleijenberg G, Engelbert RH, van de Putte EM. Functional improvement is accompanied by reduced pain in adolescent chronic fatigue syndrome. Pain Med. 2013 Sep;14(9):1435-8. doi: 10.1111/pme.12181. Epub 2013 Jun 26. http://painmedicine.oxfordjournals.org/content/14/9/1435.long (Full article)

 

A comparison of sex-specific immune signatures in Gulf War illness and chronic fatigue syndrome

Abstract:

BACKGROUND: Though potentially linked to the basic physiology of stress response we still have no clear understanding of Gulf War Illness (GWI), a debilitating condition presenting complex immune, endocrine and neurological symptoms. Here we compared male (n = 20) and female (n = 10) veterans with GWI separately against their healthy counterparts (n = 21 male, n = 9 female) as well as subjects with chronic fatigue syndrome/ myalgic encephalomyelitis (CFS/ME) (n = 12 male, n = 10 female).

METHODS: Subjects were assessed using a Graded eXercise Test (GXT) with blood drawn prior to exercise, at peak effort (VO2 max) and 4-hours post exercise. Using chemiluminescent imaging we measured the concentrations of IL-1a, 1b, 2, 4, 5, 6, 8, 10, 12 (p70), 13, 15, 17 and 23, IFNγ, TNFα and TNFβ in plasma samples from each phase of exercise. Linear classification models were constructed using stepwise variable selection to identify cytokine co-expression patterns characteristic of each subject group.

RESULTS: Classification accuracies in excess of 80% were obtained using between 2 and 5 cytokine markers. Common to both GWI and CFS, IL-10 and IL-23 expression contributed in an illness and time-dependent manner, accompanied in male subjects by NK and Th1 markers IL-12, IL-15, IL-2 and IFNγ. In female GWI and CFS subjects IL-10 was again identified as a delineator but this time in the context of IL-17 and Th2 markers IL-4 and IL-5. Exercise response also differed between sexes: male GWI subjects presented characteristic cytokine signatures at rest but not at peak effort whereas the opposite was true for female subjects.

CONCLUSIONS: Though individual markers varied, results collectively supported involvement of the IL-23/Th17/IL-17 axis in the delineation of GWI and CFS in a sex-specific way.

 

Source: Smylie AL, Broderick G, Fernandes H, Razdan S, Barnes Z, Collado F, Sol C, Fletcher MA, Klimas N. A comparison of sex-specific immune signatures in Gulf War illness and chronic fatigue syndrome. BMC Immunol. 2013 Jun 25;14:29. doi: 10.1186/1471-2172-14-29. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3698072/ (Full article)

 

Examining the impact of obesity on individuals with chronic fatigue syndrome

Abstract:

Chronic fatigue syndrome (CFS) is a complex disorder affecting multiple body systems. The most commonly used definition of CFS is 6 or more months of fatigue and the presence of at least four of eight minor symptoms. In addition, many health and psychological conditions, including severe obesity-body mass index (BMI) of 40 kg/m(2) or greater-exclude individuals from a diagnosis of CFS. Obesity has been correlated with fatigue, sleep problems, and less satisfaction with general health, functioning, and vitality.

The current study investigated weight trends over time in a community-based sample of individuals with CFS and healthy controls. The study further investigated the impact of comorbid weight issues on several health and disability outcomes in a subset of overweight individuals.

Overweight and obese individuals with CFS demonstrated poorer functioning than controls who were similarly weighted. One participant was excluded because she had gained weight at a monitoring visit and her BMI was greater than 40 kg/m(2). The implications of these findings for health care workers are discussed.

Copyright 2013, SLACK Incorporated.

 

Source: Flores S, Brown A, Adeoye S, Jason LA, Evans M. Examining the impact of obesity on individuals with chronic fatigue syndrome.Workplace Health Saf. 2013 Jul;61(7):299-307. doi: 10.3928/21650799-20130617-12. Epub 2013 Jun 24. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3899694/ (Full article)

 

Mediators of the effects on fatigue of pragmatic rehabilitation for chronic fatigue syndrome

Abstract:

OBJECTIVE: To examine potential mediators of the effect of pragmatic rehabilitation on improvements in fatigue following a randomized controlled trial for patients with chronic fatigue syndrome (CFS/ME) in primary care (IRCTN 74156610).

METHOD: Patients fulfilled the Oxford criteria for CFS. Ninety-five patients were randomized to pragmatic rehabilitation and 100 to general practitioner (GP) treatment as usual. The outcome was the Chalder fatigue scale score (0123 scoring) at end of treatment (20 weeks) and 1-year follow up (70 weeks). First, the effect of treatment on potential mediators was assessed. Then fatigue was regressed on significant mediators, treatment allocation, and baseline measures of fatigue and significant mediators.

RESULTS: Reduction in limiting activities at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -2.64, SE = 0.81, p = .001, proportion of effect mediated = 82.0%). Reduction in catastrophizing at 20 weeks mediated the positive effect of pragmatic rehabilitation on fatigue at 70 weeks (mediated effect size = -1.39, SE = 0.61, p = .023, proportion of effect mediated = 43.2%). Reductions in 70-week measures of fear avoidance, embarrassment avoidance, limiting activities, and all-or-nothing behavior all mediated improvement in fatigue at 70 weeks, although the causal direction of these cross-sectional effects cannot be determined. There were no between-group differences on measures of exercise capacity (a timed step test).

CONCLUSIONS: Improvements in fatigue following pragmatic rehabilitation are related to changes in behavioral responses to and beliefs about fatigue.

 

Source: Wearden AJ, Emsley R. Mediators of the effects on fatigue of pragmatic rehabilitation for chronic fatigue syndrome. J Consult Clin Psychol. 2013 Oct;81(5):831-8. doi: 10.1037/a0033561. Epub 2013 Jun 24. https://www.ncbi.nlm.nih.gov/pubmed/23796316

 

Are there sleep-specific phenotypes in patients with chronic fatigue syndrome? A cross-sectional polysomnography analysis

Abstract:

OBJECTIVES: Despite sleep disturbances being a central complaint in patients with chronic fatigue syndrome (CFS), evidence of objective sleep abnormalities from over 30 studies is inconsistent. The present study aimed to identify whether sleep-specific phenotypes exist in CFS and explore objective characteristics that could differentiate phenotypes, while also being relevant to routine clinical practice.

DESIGN: A cross-sectional, single-site study.

SETTING: A fatigue clinic in the Netherlands.

PARTICIPANTS: A consecutive series of 343 patients meeting the criteria for CFS, according to the Fukuda definition.

MEASURES: Patients underwent a single night of polysomnography (all-night recording of EEG, electromyography, electrooculography, ECG and respiration) that was hand-scored by a researcher blind to diagnosis and patient history.

RESULTS: Of the 343 patients, 104 (30.3%) were identified with a Primary Sleep Disorder explaining their diagnosis. A hierarchical cluster analysis on the remaining 239 patients resulted in four sleep phenotypes being identified at saturation. Of the 239 patients, 89.1% met quantitative criteria for at least one objective sleep problem. A one-way analysis of variance confirmed distinct sleep profiles for each sleep phenotype. Relatively longer sleep onset latencies, longer Rapid Eye Movement (REM) latencies and smaller percentages of both stage 2 and REM characterised the first phenotype. The second phenotype was characterised by more frequent arousals per hour. The third phenotype was characterised by a longer Total Sleep Time, shorter REM Latencies, and a higher percentage of REM and lower percentage of wake time. The final phenotype had the shortest Total Sleep Time and the highest percentage of wake time and wake after sleep onset.

CONCLUSIONS: The results highlight the need to routinely screen for Primary Sleep Disorders in clinical practice and tailor sleep interventions, based on phenotype, to patients presenting with CFS. The results are discussed in terms of matching patients’ self-reported sleep to these phenotypes in clinical practice.

 

Source: Gotts ZM, Deary V, Newton J, Van der Dussen D, De Roy P, Ellis JG. Are there sleep-specific phenotypes in patients with chronic fatigue syndrome? A cross-sectional polysomnography analysis. BMJ Open. 2013 Jun 20;3(6). pii: e002999. doi: 10.1136/bmjopen-2013-002999. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3669720/ (Full article)

 

High-throughput 16S rRNA gene sequencing reveals alterations of intestinal microbiota in myalgic encephalomyelitis/chronic fatigue syndrome patients

Abstract:

Human intestinal microbiota plays an important role in the maintenance of host health by providing energy, nutrients, and immunological protection. Intestinal dysfunction is a frequent complaint in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients, and previous reports suggest that dysbiosis, i.e. the overgrowth of abnormal populations of bacteria in the gut, is linked to the pathogenesis of the disease.

We used high-throughput 16S rRNA gene sequencing to investigate the presence of specific alterations in the gut microbiota of ME/CFS patients from Belgium and Norway. 43 ME/CFS patients and 36 healthy controls were included in the study. Bacterial DNA was extracted from stool samples, PCR amplification was performed on 16S rRNA gene regions, and PCR amplicons were sequenced using Roche FLX 454 sequencer.

The composition of the gut microbiota was found to differ between Belgian controls and Norwegian controls: Norwegians showed higher percentages of specific Firmicutes populations (Roseburia, Holdemania) and lower proportions of most Bacteroidetes genera. A highly significant separation could be achieved between Norwegian controls and Norwegian patients: patients presented increased proportions of Lactonifactor and Alistipes, as well as a decrease in several Firmicutes populations.

In Belgian subjects the patient/control separation was less pronounced, however some abnormalities observed in Norwegian patients were also found in Belgian patients. These results show that intestinal microbiota is altered in ME/CFS. High-throughput sequencing is a useful tool to diagnose dysbiosis in patients and could help designing treatments based on gut microbiota modulation (antibiotics, pre and probiotics supplementation).

Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

 

Source: Frémont M, Coomans D, Massart S, De Meirleir K. High-throughput 16S rRNA gene sequencing reveals alterations of intestinal microbiota in myalgic encephalomyelitis/chronic fatigue syndrome patients. Anaerobe. 2013 Aug;22:50-6. doi: 10.1016/j.anaerobe.2013.06.002. Epub 2013 Jun 19. https://www.ncbi.nlm.nih.gov/pubmed/23791918

 

Chronic fatigue syndrome from vagus nerve infection: a psychoneuroimmunological hypothesis

Abstract:

Chronic fatigue syndrome (CFS) is an often-debilitating condition of unknown origin. There is a general consensus among CFS researchers that the symptoms seem to reflect an ongoing immune response, perhaps due to viral infection. Thus, most CFS research has focused upon trying to uncover that putative immune system dysfunction or specific pathogenic agent. However, no single causative agent has been found.

In this speculative article, I describe a new hypothesis for the etiology of CFS: infection of the vagus nerve. When immune cells of otherwise healthy individuals detect any peripheral infection, they release proinflammatory cytokines. Chemoreceptors of the sensory vagus nerve detect these localized proinflammatory cytokines, and send a signal to the brain to initiate sickness behavior. Sickness behavior is an involuntary response that includes fatigue, fever, myalgia, depression, and other symptoms that overlap with CFS.

The vagus nerve infection hypothesis of CFS contends that CFS symptoms are a pathologically exaggerated version of normal sickness behavior that can occur when sensory vagal ganglia or paraganglia are themselves infected with any virus or bacteria. Drawing upon relevant findings from the neuropathic pain literature, I explain how pathogen-activated glial cells can bombard the sensory vagus nerve with proinflammatory cytokines and other neuroexcitatory substances, initiating an exaggerated and intractable sickness behavior signal. According to this hypothesis, any pathogenic infection of the vagus nerve can cause CFS, which resolves the ongoing controversy about finding a single pathogen. The vagus nerve infection hypothesis offers testable hypotheses for researchers, animal models, and specific treatment strategies.

Copyright © 2013 Elsevier Ltd. All rights reserved.

 

Source: VanElzakker MB. Chronic fatigue syndrome from vagus nerve infection: a psychoneuroimmunological hypothesis. Med Hypotheses. 2013 Sep;81(3):414-23. doi: 10.1016/j.mehy.2013.05.034. Epub 2013 Jun 19. https://www.ncbi.nlm.nih.gov/pubmed/23790471