Fibromyalgia and Dysautonomia: The POTS, HRV and Small Fiber Connection

Fibromyalgia is not only a pain condition

Fibromyalgia is usually introduced in one sentence: chronic widespread pain. That sentence is true, and it leaves out half the experience. Ask a room of people with fibromyalgia what else they live with and the list comes fast: crushing fatigue, sleep that never refreshes, brain fog, and then a second group of symptoms that have nothing obvious to do with pain at all. Lightheadedness when standing. A heart that races for no reason. Hands and feet that run cold, then a wave of heat. Bloating, nausea, a gut that will not settle.

That second group is the autonomic nervous system, the part that runs heart rate, blood pressure, temperature and digestion without you thinking about it. When it struggles to keep its balance, the name for that is dysautonomia. Fibromyalgia is not classified as a form of dysautonomia, but the two overlap so often that researchers have spent two decades describing fibromyalgia as a disorder of the body’s stress response system as much as a disorder of pain (Martínez-Lavín, 2007).

It is also common. Roughly 2 to 3 percent of adults worldwide live with fibromyalgia, and it is diagnosed far more often in women (Queiroz, 2013).

How fibromyalgia is diagnosed

There is no blood test or scan for fibromyalgia. The current criteria, revised in 2016, are built from two scores: how widespread your pain is, and how severe your other symptoms are (Wolfe et al., 2016).

One detail in the 2016 revision matters a great deal for this audience: a fibromyalgia diagnosis is valid regardless of other diagnoses. Having POTS, long COVID or ME/CFS does not rule it out, and having fibromyalgia does not explain those away. They can, and often do, sit side by side.

Where the autonomic nervous system comes in

Three lines of evidence connect fibromyalgia to the autonomic nervous system, and each one points to something you can watch.

Lower heart rate variability. Heart rate variability (HRV) is the small variation in time between heartbeats, a window onto the “rest and digest” side of the nervous system. A large meta-analysis in the journal Pain found that HRV is reduced across chronic pain conditions, fibromyalgia among them, which points to weaker parasympathetic activity (Tracy et al., 2016). In plain terms, the nervous system spends more of its time leaning toward “fight or flight,” which fits the poor sleep, the wired-but-tired feeling and the sensitivity to everything.

POTS on standing. When people with fibromyalgia are tested on a tilt table, one of the most common findings is postural orthostatic tachycardia, a heart rate that climbs sharply and stays high on standing (Staud, 2008). That is the same pattern that defines POTS: a sustained rise of 30 beats per minute or more within ten minutes of standing (40 for teenagers). It goes a long way toward explaining the dizziness, palpitations and fatigue that so many people with fibromyalgia describe and that the word “pain” never covered.

Small fiber damage. The smallest nerve fibers carry pain, temperature and autonomic signals. Skin biopsies show reduced small fiber density in many people with fibromyalgia (Üçeyler et al., 2013), and a meta-analysis pooling those studies put the share at 49 percent (Grayston et al., 2019). Those are the same fibers whose damage drives some cases of POTS, which our small fiber neuropathy guide covers in depth.

Fibromyalgia, ME/CFS and long COVID

Fibromyalgia shares a great deal with ME/CFS and long COVID: fatigue, unrefreshing sleep, brain fog, sensitivity to effort, and autonomic symptoms. Many people meet the criteria for more than one, and the line between them is often drawn by which symptom leads.

Long COVID sharpened the question. In a web survey of 616 people about six months after COVID-19, 30.7 percent met the survey criteria for fibromyalgia (Ursini et al., 2021). It was a survey, not a clinical exam, so the true figure may differ, but it fits a broader pattern: viral illness can leave behind a pain-and-fatigue picture that looks a lot like fibromyalgia.

The exercise row is the one to read twice. Exercise is the best-supported treatment for fibromyalgia, and for some people with ME/CFS-style crashes the wrong amount makes things worse. If you have features of both, the answer is usually not “exercise” or “rest” but pacing: finding the level you can absorb without a crash, and building from there.

What actually helps

The European League Against Rheumatism (EULAR) reviewed 107 systematic reviews and meta-analyses for its fibromyalgia guidelines. Exercise was the only therapy that earned a “strong for” recommendation (Macfarlane et al., 2017). Education and non-drug approaches come first, with psychological therapies, specific medications and other options tailored to the person when those are not enough.

For people with autonomic symptoms, two caveats make that advice workable:

• Start lower than feels useful. If standing makes you dizzy, begin with recumbent options like a rowing machine, a recumbent bike or floor exercises, the same approach used in exercise for POTS.
• Pace, and build. A review of 41 chronic pain studies found that both extremes go badly: avoiding activity, and pushing through to the point of severe pain, were each linked with worse outcomes. Pacing on its own was a mixed picture, and the authors suggest it works best when it is used to raise activity gradually rather than only to hold it down (Andrews et al., 2012). Pacing 101 walks through how to find your envelope and grow it.

Two other levers are worth knowing about:

• Slow breathing. In a pilot of 12 women with fibromyalgia, ten weekly sessions of HRV biofeedback, breathing at each person’s resonant rate of about six breaths a minute, were followed by clinically meaningful drops in depression and pain (Hassett et al., 2007). It was small and uncontrolled, so treat it as promising rather than proven. Our resonant breathing guide explains the technique.
• The POTS basics, if you have POTS features. Salt and fluids, compression and avoiding hot showers target the standing symptoms directly, and they are a conversation to have with your clinician.

What to track, and why it helps

You cannot measure fibromyalgia pain with a sensor. What you can measure is the nervous system around it, and that is often where the useful patterns hide.

• A morning HRV reading, taken the same way each day, so a drop after a bad night or a busy day shows up against your own baseline instead of a chart built for athletes. The baseline guide explains why your own normal matters more than any population range.
• A stand test, if you get dizzy on standing. A home stand test puts a number on the rise and gives your clinician something concrete.
• Sleep, because unrefreshing sleep is part of the diagnosis and often the first domino. See sleep and autonomic recovery.
• Daily effort, so you can see whether a flare followed a busy day, and how many days later.
• Symptoms and triggers as they happen: pain level, fog, fatigue, weather, stress, food. The symptom journal guide shows how to keep it light.

The bottom line

Fibromyalgia is a pain condition with an autonomic shadow. Lower heart rate variability, POTS on standing and small fiber damage are each found in a large share of people with it, which is why dizziness, palpitations, temperature swings and gut trouble come along so often. It overlaps with ME/CFS and long COVID, and a fibromyalgia diagnosis does not cancel out any of those. Exercise is the best-supported treatment, pacing is what lets you build it without a crash, and a record of your HRV, standing heart rate, sleep, effort and symptoms is what turns “some days are just bad” into patterns you and your clinician can act on.

Sources and further reading

• Martínez-Lavín M. Biology and therapy of fibromyalgia. Stress, the stress response system, and fibromyalgia. Arthritis Research & Therapy, 2007.
• Queiroz LP. Worldwide epidemiology of fibromyalgia. Current Pain and Headache Reports, 2013.
• Wolfe F, Clauw DJ, Fitzcharles MA, et al. 2016 revisions to the 2010/2011 fibromyalgia diagnostic criteria. Seminars in Arthritis and Rheumatism, 2016.
• Tracy LM, Ioannou L, Baker KS, et al. Meta-analytic evidence for decreased heart rate variability in chronic pain implicating parasympathetic nervous system dysregulation. Pain, 2016.
• Staud R. Autonomic dysfunction in fibromyalgia syndrome: postural orthostatic tachycardia. Current Rheumatology Reports, 2008.
• Üçeyler N, Zeller D, Kahn AK, et al. Small fibre pathology in patients with fibromyalgia syndrome. Brain, 2013.
• Grayston R, Czanner G, Elhadd K, et al. A systematic review and meta-analysis of the prevalence of small fiber pathology in fibromyalgia. Seminars in Arthritis and Rheumatism, 2019.
• Ursini F, Ciaffi J, Mancarella L, et al. Fibromyalgia: a new facet of the post-COVID-19 syndrome spectrum? Results from a web-based survey. RMD Open, 2021.
• Macfarlane GJ, Kronisch C, Dean LE, et al. EULAR revised recommendations for the management of fibromyalgia. Annals of the Rheumatic Diseases, 2017.
• Andrews NE, Strong J, Meredith PJ. Activity pacing, avoidance, endurance, and associations with patient functioning in chronic pain. Archives of Physical Medicine and Rehabilitation, 2012.
• Hassett AL, Radvanski DC, Vaschillo EG, et al. A pilot study of the efficacy of heart rate variability (HRV) biofeedback in patients with fibromyalgia. Applied Psychophysiology and Biofeedback, 2007.