The authors got right to the point. Most people think fibromyalgia (FM) is a central nervous system condition characterized by a hypersensitive pain response and a balky pain inhibition system – and, indeed, all that is happening.

Wound up, Overheated and Tweaked: A Look at the Fibromyalgia Brain and Nervous System.

There’s a lot more going on, though. What about all those pesky autonomic nervous system findings? The low heart rate variability findings, the puny baroreflex response, the chronotropic incompetence, the strange tilt table results? What role might they play in the pain and other symptoms present in FM?

The authors of this study focused on a key player in the cardiovascular system – the baroreflex response. The baroreflex (baro=pressure) system is composed of a series of receptors in the heart which respond to changes in blood pressure. When blood pressure becomes elevated, the baroreceptors tell the heart rate to decrease. Low blood pressure, on the other hand, reduces baroreceptor activity – causing the heart rate to increase.

When we stand, and blood pressure in the upper body momentarily drops, the baroreflex system tells the heart rate to increase. The system responds quickly – in the fractions of a second – and is constantly adjusting itself. It plays a key role in our ability to remain upright and deal with stress – but that’s just the beginning.

Interconnected Systems

It’s not just about blood pressure. The baroreceptors interact with and influence an amazing number of systems – most of which appear to be involved in fibromyalgia and ME/CFS.

Baroreceptor activation inhibits the activity of the fight or flight, or sympathetic nervous system (SNS). (Low blood pressure on the other hand increases SNS activity).

Plus, the baroreceptors also regulate blood vessel functioning. When blood pressure rises, the baroceptors transmit a signal to open them up (dilate them).

Baroreceptor activation also tamps down brain activity. This occurs when signals sent to the brainstem are transmitted to the amygdala, insula, anterior cingulate and cingulum. Baroreceptor activation also appears to inhibit pain levels and reduces emotional volatility. Studies suggest that having more sensitive cardiac baroreflex responses may result in increased pain inhibition; i.e. have less pain.

The signals the baroreceptors emit also end up in a very interesting place for FM, ME/CFS and possibly long COVID – the  the brainstem. From there, the signals activate motor neurons associated with the vagal nerve (another possible factor), and inhibit sympathetic nervous system neurons in the spinal cord.

Long COVID and ME/CFS – the Brainstem / Dysautonomia Connection

From heart rate and blood pressure to the fight or flight response, to the blood vessels, to brain activity and pain levels, the baroreceptors do far more than just adjust adjust our blood pressure.

The Study

The cardiac, vasomotor, and myocardial branches of the baroreflex in fibromyalgia: Associations with pain, affective impairments, sleep problems, and fatigue – Reyes del Paso – – Psychophysiology – Wiley Online Library

The Gist

  • The baroreflex response consists of receptors in the arteries surrounding the heart which respond to changes in blood pressure.
  • Studies suggest, though, that the baroreflex response also helps regulate sympathetic nervous system activation, heart rate variability, blood vessel functioning and brain activity.
  • They also suggest that altered baroreflex activity would contribute to increased pain, fatigue and sleep issues.
  • This was the first fibromyalgia study to assess all three branches of the baroreflex system. Pain and mental stress tests were used to determine how well the baroreflex system was doing.
  • Every symptom they measured – pain, fatigue, sleep and mood – was worsened when the baroreceptors failed to activate normally in the people with FM.
  • They asserted that the study confirmed that “deficient autonomic cardiovascular regulation’ was present in FM.
  • The authors proposed that balky baroreceptor activation may be implicated in the pain, fatigue, sleep and mood problems in FM.
  • Since baroreceptor activation also significantly affects heart rate variability (HRV) – which tends to be low in both FM and ME/CFS – baroreflex problems have be contributing to the low HRV in FM.
  • Since deficient baroreflex responses have also been found in ME/CFS and POTS, this finding links together FM, POTS and ME/CFS.
  • These diseases also share autonomic nervous system issues, female predominance, small fiber neuropathy, exercise issues, and cognitive, sensory and pain problems.

Three branches of baroreflex response exist: the cardiac branch, which regulates heart rate; the vascular branch, which regulates blood vessel diameter; and the myocardial branch, which controls the contraction of the heart and this study – the first to do so –  examined all pf them in FM.

After doing baseline tests, the Spanish research group put 40 people with fibromyalgia and healthy controls into a state of stress with pain (cold water hand plunge) and mental tasks while assessing their baroreflex responses and their symptoms (pain, fatigue, etc.).

The goal was to see how the three parts of the baroreflex response responded. If the responses of the FM patients were blunted relative to the healthy controls, that could help explain why people with FM experienced more pain (reduced pain inhibition) and fatigue, experienced more emotional ups and downs, and had more difficulty sleeping and relaxing (increased SNS activation).


“Taken together, results confirm the notion of deficient autonomic cardiovascular regulation in FMS and implicate aberrant baroreflex function in its symptoms.” The authors

The study found that all three branches of the baroreflex response were inhibited – both at rest and when stressed in the FM patients. The authors’ conclusion – the autonomic nervous system in the FM patients’ cardiovascular systems was not working correctly (i.e. they had “dysfunctional autonomic cardiovascular regulation”).

Every symptom they measured – pain, fatigue, sleep and mood – was worsened when the baroreceptors failed to activate normally. Interestingly, the mental stressor – an arithmetic test – produced more impaired baroreceptor activation than the pain (cold pressor) test. The arithmetic test resulted in impaired heart rate, altered heart muscle contraction and blood vessel regulation in the FM patients. It suggested that mental stress, in particular, dramatically affected the functioning of the autonomic nervous systems in people with FM.

The results jived with a 2017 study which found that a reduced baroreflex response was associated with reduced quality of life in FM. It suggested that impaired baroreflex activity may even be inhibiting FM patients from carrying out their daily activities (e.g. anything that involves standing).

An Overlooked Issue in Fibromyalgia? Study Highlights Orthostatic Intolerance – Problems Standing

The effect the baroreceptors have on heart rate variability (HRV) stands out. HRV measures the gaps between our heartbeats and is used to assess the functioning of the stress response. Higher HRV indicates that a supple and responsive autonomic nervous system is present. Lower HRV suggests an impaired ANS. Lower HRV is associated increased risk of mortality over time. Reduced HRV is one of the most consistent findings in both fibromyalgia and chronic fatigue syndrome (ME/CFS).

Are the baroreceptors sending the wrong signal to the brainstem? Or is it getting messed up in the brainstem? Or is something else going wrong?

Note, again, how closely tied in the baroreceptors are to the stress response. They’re constantly monitoring our blood pressure. When it goes up – a sign that some sort of stress is happening – they reduce the heart rate, dilate our blood vessels, and increase our heart rate variability. While they are doing that they’re also reducing the excitability of the brain and telling it and the pain response to calm down. The baroreceptors appear to be designed to improve the resilience of our systems when they are put under stress.

Many issues potentially could be linked with a balky baroreceptor response. A good part of the pain in FM, for instance, could be associated with the reduced pain inhibition – which is impaired when baroreflex sensitivity is reduced -as was found in this study. Increased heart rates during standing or at baseline, blood vessel flows, the activation of the fight of the fight or flight system. the ability to get a deep sleep  — all could be affected.

The baroreceptors interact, then, with several potentially important aspects of ME/CFS and FM – the autonomic nervous system, blood vessels, heart, brainstem, limbic system, and the vagus nerve. .

Do autonomic nervous system issues link all these diseases together?

These findings also potentially link FM, ME/CFS, POTS and, potentially, long COVID together. Reduced baroreflex responses have been found in adolescents and adults with ME/CFS and/or postural orthostatic tachycardia syndrome (POTS), and autonomic nervous system issues are cropping big time up in long COVID. Female predominance, small fiber neuropathy, exercise issues, cognitive, sensory and pain problems all pervade these disorders. Someone recently suggested that fibromyalgia the more pain dominant side of all these conditions.

Of course, autonomic nervous system problems are rife in these disorders. While it’s hardly been noticed, evidence of orthostatic intolerance (increased symptoms while standing) have been building in fibromyalgia – long perceived as simply a pain disorder – for years.

Tilt table tests have found problems with blood pressure regulation, dysautonomia, low blood volume, sympathetic nervous system hyperactivity, chronotropic incompetence, even fluid pooling in the lower extremities (a classic finding in POTS).

Taking a Stand: Fibromyalgia, Orthostatic Intolerance and the Autonomic Nervous System

Despite the fact that medications and other treatments can help with these symptoms, remarkably little of this has seeped down to doctors. A Health Rising 2018 survey of over 330 people with FM found that 84% of FM patients reported their doctor had not suggested a tilt table test.


Check out an easy home test to assess whether you might have orthostatic intolerance.

NASA Lean Test: An Easy Way to Diagnose Orthostatic Intolerance in ME/CFS, Fibromyalgia and POTS



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