Heart rate variability may help to understand chronic fatigue syndrome (CFS)

Firestormm

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Plos One Research: Published 14 November 2012: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049518#abstract0

Background

Cognitive difficulties and autonomic dysfunction have been reported separately in patients with chronic fatigue syndrome (CFS). A role for heart rate variability (HRV) in cognitive flexibility has been demonstrated in healthy individuals, but this relationship has not as yet been examined in CFS. The objective of this study was to examine the relationship between HRV and cognitive performance in patients with CFS.

Methods

Participants were 30 patients with CFS and 40 healthy controls; the groups were matched for age, sex, education, body mass index, and hours of moderate exercise/week. Questionnaires were used to obtain relevant medical and demographic information, and assess current symptoms and functional impairment.

Electrocardiograms, perceived fatigue/effort and performance data were recorded during cognitive tasks. Between–group differences in autonomic reactivity and associations with cognitive performance were analysed.

Results

Patients with CFS showed no deficits in performance accuracy, but were significantly slower than healthy controls.

CFS was further characterized by low and unresponsive HRV; greater heart rate (HR) reactivity and prolonged HR-recovery after cognitive challenge.

Fatigue levels, perceived effort and distress did not affect cognitive performance. HRV was consistently associated with performance indices and significantly predicted variance in cognitive outcomes.

Conclusions

These findings reveal for the first time an association between reduced cardiac vagal tone and cognitive impairment in CFS and confirm previous reports of diminished vagal activity.
News Medical Report: http://www.news-medical.net/news/20121115/Heart-rate-variability-may-help-to-understand-chronic-fatigue-syndrome-(CFS).aspx

Researchers have discovered for the first time that reduced heart rate variability – or changes in heart beat timing – best predicts cognitive disturbances, such as concentration difficulties commonly reported by people with chronic fatigue syndrome (CFS). This adds to the growing body of evidence linking autonomic nervous system imbalance to symptoms of this poorly understood disorder.

The findings are reported in the journal PLOS ONE.

Chronic fatigue syndrome is characterised by medically unexplained, disabling fatigue and neuropsychiatric symptoms of at least six months’ duration. The disturbance underlying the symptoms in CFS is still poorly understood.

“We have studied autonomic function in CFS for some time and our findings clearly indicate a loss of integrity in stress-responsive neural and physiological systems in CFS. Patients with this condition are hyper-responsive to challenges arising both from within the body and from the environment,” says lead researcher, University of New South Wales Associate Professor Ute Vollmer-Conna.

“Even when they sleep, their stress-responsive neural systems are on high alert, signalling that it is not safe to relax. I think this condition may be understood by analogy to post-traumatic stress disorder, just that in CFS the original trauma is most likely a physiological, internal one, such as a severe infection.”

In a study of 30 patients with CFS and 40 healthy individuals, UNSW researchers recorded the heart beats of participants (via ECG) and analysed cardiac responses to cognitive challenges, and associations with mental performance outcomes.

The patients with CFS performed with similar accuracy, but they took significantly longer to complete the tests than people without the condition. They also had greater heart rate reactivity; low and unresponsive heart rate variability; and prolonged heart rate-recovery after the cognitive challenge.

Resting heart rate variability (an index of vagus nerve activity) was identified as the only significant predictor of cognitive outcomes, while current levels of fatigue and other symptoms did not relate to cognitive performance.

“This is the first demonstration of an association between reduced cardiac vagal tone and cognitive impairment in CFS. Our findings confirm previous reports of a significant loss of vagal modulation, which becomes particularly apparent when dealing with challenging tasks. The current results are consistent with the notion that CFS represents a ‘system under stress’,” Associate Professor Vollmer-Conna says.

The findings could lead to new ways to improve cognitive difficulties in people with CFS, including biofeedback assisted retraining of autonomic functioning, the researchers say.

The journal article can be viewed here: http://dx.plos.org/10.1371/journal.pone.0049518

The research was supported by funding from the Mason Foundation; ANZ Trustees: Medical and scientific research grants – Chronic Fatigue Syndrome, Australia.

Source: The University of Sydney
 

xchocoholic

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Correct me if I'm wrong but in't this just another way of saying that pwcs with orthostatic intolerance (oi)
will have cognitive problems ? If so, how do they expect biofeedback to correct oi ?

Also, they refer to our inability to sleep as meaning our bodies are stuck in fight or flight mode but I can't see how that relates to oi. I can always think more clearly when I'm supine.

I "think" they're drawing a conclusion which doesn't exist.

Tx .. X
 

Esther12

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For things like this and the HPA findings, I do wonder if they are secondary to patients suffering from health problems (of whatever cause), then facing the quackery that surrounds CFS, and this then leading to changes in stress responses, etc. Whenever there are widespread findings for CFS patients I tend to suspect that it's secondary... nice to see that they seem to have matched activity levels though, as that's one way people have claimed these sorts of results are secondary in the past. Julia Newton's done similar stuff in this area, but it's not something I've been keeping a close eye on.
 

Valentijn

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The impression I get is that the study found a correlation between two symptoms (heart rate variability and cognitive problems), then some of the researchers reached the usual stupid assumptions regarding the underlying cause, with absolutely no proof whatsoever.

It's probably an attempt to reconcile their physiological discoveries with all the bad psychological research regarding curing ME/CFS with CBT and GET. Four psychiatrists are listed as authors, and two people with backgrounds in real medicine.

I'm really sick of seeing this sort of compromise. It just makes both camps sound like idiots. Why can't they just say "HRV influences cognitive performance. We don't know why - further research is needed." Instead they write a complete work of fiction to get from point A (physiological signs) to point Z (psychological cure).
 
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Sean

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It's probably an attempt to reconcile their physiological discoveries with all the bad psychological research regarding curing ME/CFS with CBT and GET. Four psychiatrists are listed as authors, and two people with backgrounds in real medicine.

I'm really sick of seeing this sort of compromise. It just makes both camps sound like idiots. Why can't they just say "HRV influences cognitive performance. We don't why - further research is needed." Instead they write a complete work of fiction to get from point A (physiological signs) to point Z (psychological cure).
It's pathetic, isn't it. (And the reviewers are just as much to blame for letting it through.)

Pity, as it is otherwise a useful (though unsurprising) finding.
 

biophile

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Even when they sleep, their stress-responsive neural systems are on high alert, signalling that it is not safe to relax. I think this condition may be understood by analogy to post-traumatic stress disorder, just that in CFS the original trauma is most likely a physiological, internal one, such as a severe infection.
I initially misread the sentence and agreed with it until I realized my mistake:

"Even when they sleep, their stress-responsive neural systems are on high alert, signalling that it is not safe to relax. I think the abnormal response to stress in this condition may be understood by biological analogy to post-traumatic stress disorder, just that in CFS the ongoing trauma is most likely a physiological, internal one, such as multi-system disease."

Esther12 said:
For things like this and the HPA findings, I do wonder if they are secondary to patients suffering from health problems (of whatever cause), then facing the quackery that surrounds CFS, and this then leading to changes in stress responses, etc.
Ironic if a "psychosocial" aspect of BPS for CFS involves quackery involving the BPS model for CFS.
 

Esther12

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Ironic if a "psychosocial" aspect of BPS for CFS involves quackery involving the BPS model for CFS.
I'd be amazed if the BPS approach to CFS had not caused psychosocial harm to most patients. It's had such a profound affect by encouraging unreasonable social responses to patients.
 
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I wonder about the HRV of severely fatigued healthy people - eg those who have underwent severe fatigue during military training or perhaps as training/testing for the space programmes etc?

HRV seems to be low across the board in many illnesses, from anxiety to Rheumatoid arthritis. It seems to be a fairly nonspecific marker unfortunately.
 

WillowJ

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Simon

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Cort has now blogged about this study

Some comments from me, based on the full text

Heart Rate Variability a moderate predictor of cognitive performance in patients
  • Just as it is in controls in this study and in healthy people in other studies too. Maybe it would have been more surprising if it hadn't predicted cognitive performance. "As disease status was not an independent predictor, this suggests a broader role for low HRV in mental flexibility in general"
  • HRV only explains about 25% of the variance in results, so it's a significant but not huge predictor of performance
Mental fatigue, and perceived effort were not predictors of performance
  • In some ways very surprising, but in line with other studies, including this recent one from Susan Cockshell
  • Same applied to mental energy, both before and after tests and for other symptoms. In all cases there were large differences between patients and controls at the group level, but none of these measures predicted differences in cognitive performance for individuals.
Heart Rate of patients took MUCH longer to recover after mental exertion

This was probably the most striking robust finding of the study, and this first time this phenomena has been observed in CFS patients. Note the average time was TWICE as long to recovery:
[analysis] revealed a highly delayed average time-to-recovery of HR to baseline levels for patients with CFS [M = 74s, SD = 6.4 versus M = 36s, SD = 3.8; p=0.001. Compared to healthy participants, patients with CFS were 10.5 times less likely (95% CI 3.2– 34.4) to achieve resting HR within the first minute of the recovery period.
...
This is the first reported evidence of a difference in time-to-recovery to resting HR after exposure to a mental stressor in CFS
This slow recovery is probably the best evidence within the study for dysfunctional vagal activity.

Lots of speculation
  • There was a long discusiioin with much hypothesising: "postulated, speculative, consistent with..." etc. May be right, but the model presented and much of the speculation went well beyond the evidence presented.
  • As the authors point out, they would have to do a series of new and very different studies to validate the hypothesis, eg the proposed role for the PreFontal Cortex
  • Personally, I think the use of PTSD as an analogy was unfortunate as the model presented was rooted in physiological changes.
  • Weaknesses acknowledged in the paper:
This study found a significant association between reduced cardiac vagal activity and cognitive performance impairment in CFS. Nevertheless, exposition of the cause-effect relationship between these two variables, as well as of a critical role for inactivity of the PFC in the pathophysiology of CFS remains beyond the scope of this study
...
A better understanding of the specific role of changes in autonomic functioning in the development and maintenance of symptoms in CFS awaits assessment in longitudinal cohort studies.
Summary
  • The HRV link to cognitive performance found in CFS patients was the same as that found in controls, and isn't very surprising
  • The inability of symptoms inc mental fatigue/effort to predict performance is more surprising
  • The very slow recovery of Heart Rate to resting levels following exertion is a new finding and a very marked effect
One final point, patients exercised moderately (eg brisk walking) for an average of 3.5 hours a week (same as controls), which probably makes them pretty-high functioning patients. The patients were recruited from a clinical CBT/GET programme.
 

jeffrez

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I think it's a good study. Not only clearly shows both cognitive and autonomic dysfunction in CFS compared to controls, but also a possible physiological reason for cog dysfunction in the differences that also are found in HRV and autonomic function between CFSers and normals. They need to go further and find out the neurological or neurocognitive causes of the vagal/autonomic issues. Perhaps then EEG neurofeedback practitioners can zero in on the cause better and we can treat it more effectively.
 

taniaaust1

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[One final point, patients exercised moderately (eg brisk walking) for an average of 3.5 hours a week (same as controls), which probably makes them pretty-high functioning patients. The patients were recruited from a clinical CBT/GET programme.
:rolleyes: I wish they'd stop using patiences for ME/CFS studies who can clearly exercise okay on top of what they already do!! Using patients who are able to do CBT/GET doesnt apply to many of us.

If they truely want to see problems in the ME/CFS patients why dont they start actually using a lot more sicker patients in their studies!!!
 

taniaaust1

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They need to go further and find out the neurological or neurocognitive causes of the vagal/autonomic issues. Perhaps then EEG neurofeedback practitioners can zero in on the cause better and we can treat it more effectively.
It is well known that too much bed rest "can" cause autonomic dysfunction such as POTS. I wouldnt be surprised if the psych field peoples say its the time we spend laying which is causing our issues.
 

jeffrez

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It is well known that too much bed rest "can" cause autonomic dysfunction such as POTS. I wouldnt be surprised if the psych field peoples say its the time we spend laying which is causing our issues.

Haha! I was talking more about brainwaves, but I'm sure some would say that, like lying in a coma is what's causing the coma, lol.
 

Allyson

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Haha! I was talking more about brainwaves, but I'm sure some would say that, like lying in a coma is what's causing the coma, lol.
@Tania - was that a joke about the bedrest causing POTS?

If not why does everyone who lies in bed for two weeks not develop POTS

That is what a cardioligst said cause my "CFS" - lying in bed for 2 weeks

When i ksed then why did that not happen to evryone she then said "cfs is psychosomatic" and the treatment is o get up everydy for 3 weeks, have a HOT SHOWER an stay up all day.

I did not go back.

A
 

xchocoholic

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I've found that resting on the couch for 3 days in a row makes me get winded easier for about
a day afterwards but that's it. Once I get moving again, my body adjusts back to my pre-couch
strength.

I've also found out numerous times that I can gain muscle strength via exercise. The problem is that
eventually I get pem or I crash so I can't exercise anymore. I gave up spending my valuable time exercising
after I learned this.

I wish they'd come up with some genius protocal for treating oi. I have several possible physical
reasons (lbbb, lung scaring, brain damage, neck damage, hyperinsulinemia and mast cell disorder)
that can explain my oi but I have no idea who could figure out what I should do. Btw, I think all my physical
reasons have all been shown as possible causes of oi via research. I need a genius to unravel this tho.

Tc ... X
 

Research 1st

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It is well known that too much bed rest "can" cause autonomic dysfunction such as POTS. I wouldn't be surprised if the psych field peoples say its the time we spend laying which is causing our issues.
This is a very good point you raise and although an old thread, I wanted to reply if I may.

Until there is a blood test for POTS (potentially looking at antibodies), it's possible for bedridden highly disabled patients with disease based POTS admitted onto a hospital ward (via ER) to meet dangerous doctors in hospitals. Doctors who presumes the patient only has deconditioning POTS due to be allegedly 'depressed'. They then only offer psychiatric treatment to 'get them out of bed'. (CBT GET) rather than go down the beta blocker/midodrine route.

Although deconditioning phenomena of tachycardia and low blood pressure on standing (not real POTS, but is oddly called deconditioning POTS - a misnomer as it's not a 'syndrome' really), is a rare diagnosis, it remains a real risk to the bedridden ME CFS patient, or the disease based POTS patient.

You can probably guess how I learnt this to my cost, myself and others too.