The imbalance behind Long Covid has a name: autonomic dysfunction.
Fatigue, “brain fog,” a racing heart on standing, poor sleep — for a large share of people with Long Covid, these complaints trace back to a measurable disorder of the autonomic nervous system. We explain what the science shows — with sources.
Do you recognise these complaints in yourself or in a patient?
The official definition requires symptoms persisting for 3 months or more after SARS-CoV-2 infection.
A committee of the National Academies of Sciences, Engineering and Medicine (commissioned by U.S. health authorities) defines Long Covid as “an infection-associated chronic condition following SARS-CoV-2, persisting ≥3 months, with one or multiple symptoms, continuous, relapsing, or progressive.”
Self-assessment, not self-diagnosis. Diagnosis and severity assessment require a physician.
The autonomic nervous system is affected in the majority of patients studied.
of those examined at specialised clinics
show moderate to severe autonomic dysfunction on the COMPASS-31 scale (studies 2022–2025). The samples come from specialised centres — the real share in the general population is lower.
meet the criteria for POTS
(postural orthostatic tachycardia syndrome) in multicentre follow-up of highly symptomatic patients (Circulation: Arrhythmia and Electrophysiology; JACC: Advances, 2025).
reduced heart rate variability
— a systematic review and multiple cohort studies (2023–2025) consistently find lowered parasympathetic and raised sympathetic tone.
Sources: Eldokla et al., Ann Clin Transl Neurol 2022 · Frontiers in Neurology, global study n=2314, 2022 · Circulation: Arrhythmia and Electrophysiology 2025 · JACC: Advances (LISTEN Study) 2025 · Scientific Reports 2023 (PMC10733257) · systematic review PMC10137929, 2023.
Non-invasive modulation of exactly this system.
NESA XSIGNAL® works with controlled microcurrents through the limbs, aimed at the balance between the sympathetic and parasympathetic nervous system. This is the same system that the studies above document as disrupted in Long Covid — the thematic link is real.
When NESA helps the autonomic nervous system regain its balance, it is precisely this restored function of the nervous system itself — not the device — that may contribute to easing related complaints: fatigue, a racing heart, disrupted sleep.
There is a randomised pilot study of NESA in Long Covid — with encouraging results.
A triple-blind, randomised pilot study (n=16: 9 with NESA, 7 with a placebo device) in women with autonomic dysfunction after Long Covid measured heart rate variability, pain threshold, fatigue, sleep and quality of life. Both groups showed improvement in fatigue, sleep and quality of life. Heart rate variability (SDNN) and local pain threshold improved significantly more in the NESA group (p<0.05). Given the small sample, the authors — with the caution standard in scientific publications — recommend larger studies to confirm the effect: standard scientific caution, not a negative result (Melián-Ortíz et al., Brain Sciences 15(5):510, 2025).
Measurable effects on exactly these systems — in other patient groups.
Above we saw that heart rate variability, sleep quality and mental clarity are systematically affected in Long Covid. NESA XSIGNAL® has published results precisely in these areas — measured in other study populations, on the same physiological systems.
Heart rate variability (SDNN / vagal tone RMSSD)
In athletes: SDNN from 16 to 51 ms, vagal tone (RMSSD) from 27 to 61 ms — the same markers documented above as systematically reduced in Long Covid (Medina-Ramírez, ULPGC, 2025).
Sleep quality, less daytime sleepiness (−58%)
In dementia patients (Teruel-Hernández et al., Int J Environ Res Public Health, 2023); less night-time waking (−22%) and lower night-time heart rate (−11%) in professional basketball players (García et al., Frontiers in Physiology, 2022).
REM sleep phase and cognitive function
REM sleep in elite athletes (Medina-Ramírez et al., Stresses, 2024); cognitive function in dementia patients (Teruel-Hernández et al., 2023).
The results above come from the official, regularly updated database of published NESA results (nesascience.com, peer-reviewed publications in Frontiers, MDPI/IJERPH, BMC, Can J Urol and others) — measured in other study populations (athletes, dementia patients), on the same physiological systems. Full results map: the “Evidence” section of NESA.html.
Supporting the autonomic nervous system is an evolving direction in Long Covid care.
Scientific interest in the role of the autonomic nervous system in Long Covid is growing — in parallel with a better understanding of why so many patients experience fatigue, a racing heart and exercise intolerance. This is an active, evolving field, not a closed chapter.
Therapists consider NESA as an addition to established care — always at the treating physician's discretion and adapted to the patient's individual condition.
Today's clinical guidelines (NICE, CDC, WHO, AWMF) point to pacing — careful energy management to avoid post-exertional malaise (PEM) — as the primary, well-established recommendation for Long Covid.
Sources: NICE NG188 · CDC Long COVID Clinical Guidance · WHO position on Post-Exertional Malaise, 2024 · AWMF S1 guideline “Long/Post-COVID,” registry no. 020-027.
The spike protein does not always disappear completely — and this is now measurable, not a secret.
In parallel with the research on the autonomic nervous system, another line of science is tracking whether parts of the virus — specifically the spike protein — remain in the body longer than expected after the acute infection.
circulating spike protein in blood plasma
measured with an ultrasensitive immunoassay (Simoa) in patients with Long Covid symptoms — but not in those who recovered without complaints (Swank et al., Clinical Infectious Diseases, 2023).
S1 protein detected in immune cells
— in non-classical CD16+ monocytes of PASC/Long Covid patients, up to 15 months after infection (Patterson et al., Frontiers in Immunology, 2022).
spike protein “trapped” in fibrin microstructures
along with inflammatory molecules resistant to normal breakdown — a proposed mechanism for fatigue and impaired oxygen delivery (Pretorius, Kell et al., Cardiovascular Diabetology, 2021–2022).
Not all researchers accept that these findings prove an active viral reservoir — a critical commentary in the same journal (Clinical Infectious Diseases, 2022) describes the persistent-SARS-CoV-2 hypothesis as “incompatible with the available data.” And the most direct test of this hypothesis to date — an extended course of antiviral treatment (Paxlovid) in the large RECOVER-VITAL trial (The Lancet Infectious Diseases, August 2026, n=959) — showed no improvement in Long Covid symptoms versus placebo at month 6.
It is also important to note the following: the mechanism of NESA XSIGNAL® (controlled microcurrents, balancing the autonomic nervous system) targets nervous system regulation, not the breakdown or “clearance” of spike protein from the body — these are different biological processes. NESA's focus is where it has documented results — autonomic regulation.
Sources: Swank et al., Clinical Infectious Diseases 76(3):e487, 2023 · Patterson et al., Frontiers in Immunology 12:746021, 2022 · Pretorius, Kell et al., Cardiovascular Diabetology 2021–2022 · critical commentary, Clinical Infectious Diseases, doi:10.1093/cid/ciac895, 2022 · RECOVER-VITAL, The Lancet Infectious Diseases, August 2026 (NCT05595369).
NESA supports autonomic balance in Long Covid — alongside medical follow-up.
The support is directed at the autonomic nervous system — the system in which the pilot study measured a significant improvement in HRV and pain threshold with NESA.
In patients with pronounced Post-Exertional Malaise (PEM), any new intervention requires explicit attention to pacing and consultation with the treating physician — including non-pharmacological methods.
Absolute contraindications (pacemaker, pregnancy, active electrical implants) follow the device's IFU.
Discuss your specific case with us.
For therapists and doctors: we explain the NESA mechanism, the available protocols, and how to assess whether it is a suitable tool within the patient's overall plan.
Where can I get a NESA session?
The authorised centres in Bulgaria — Sofia, Plovdiv and Pleven — with address, phone and contact person.
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