Sleep quality and duration are critical to cognitive, emotional and physical well-being, and poor sleep quality has been associated with an increased risk of cognitive, psychological and cardiometabolic disorders. Several important physiological activities occur during sleep including a reduction in heart rate and blood pressure. In addition, sleep exerts important modulatory effects on hormone release. Previous studies have shown that lack of sleep can generate exaggerated cortisol responses or psychological and physiological stressors. Cortisol has widespread effects throughout the body and brain, affecting mood, arousal, energy, metabolic processes, and immune and inflammatory system functioning. Therefore, disruptions in cortisol secretion during the night can influence a wide variety of processes in our body that may contribute to the perception of poorer sleep quality. In addition, the salivary enzyme α-amylase is considered a biomarker of cognitive, psychosocial, emotional or physical stress. It is important to note that the autonomic nervous system (ANS) regulates several physiological processes, including heart rate, blood pressure, respiration, and digestion. The ANS consists primarily of the sympathetic system and the parasympathetic system. Increased parasympathetic activity is considered to promote health, whereas a dominant or overactive sympathetic branch is considered to be detrimental to health.

A recent study found that both sleep quality and quantity of sleep were associated with resting ANS functioning. They found that poorer sleep quality was associated with greater sympathetic dominance. Research on the sympathetic and parasympathetic branches of the ANS has shown that autonomic imbalances are precursors to disease formation and other health-related risks. Coronavirus disease 2019 (COVID-19), has in many cases involved the presence of long-lasting symptoms several weeks or months after surviving acute infection with the virus, leading to a new disease called long COVID-19 or post-COVID-19 syndrome (PCS). A recent study showed that sleep quality influences the relationship between symptoms associated with sensitization and mood disorders with health-related quality of life in people suffering from long COVID.

Non-invasive neuromodulation directed to ANS may be an option to treat the sleep disorders observed in patients with long COVID.

OBJETIVES:

Therefore, the primary objective of this study is to evaluate the efficacy of a treatment protocol on the ANS by means of non-invasive neuromodulation in aspects related to sleep in long COVID patients compared to placebo. As secondary objectives, we propose to evaluate the efficacy of a treatment protocol on the ANS by non-invasive neuromodulation in aspects related to ANS functioning, psychological variables, fatigue, pain perception and quality of life in patients with long COVID.

Inclusion Criteria:

• Subjects with long COVID or post- acute COVID syndrome
• With a evolution of at least 6 months after acute SARS-cov-2 infection
• Whit symptoms present at baseline.

Exclusion Criteria:

• Pregnancy.
• Pacemakers
• Ulcerations or wounds in the area of electrode application.
• Decompensated heart disease.
• Epilepsy and/or choreic syndromes.
• Frequent medication with corticosteroids, hypnotics or supplements such as melatonin, Ashwagandha or phosphatidylserine.
• Hypersensitivity on hands and feet that influence the use of the gloves and socks from the neuromodulation system.

Assignment to each group will be done by randomization software performed blindly by an external investigator who will not perform the interventions with the patients.

Assessment will be performed by two persons of the team, not involved in the treatment.

Participants will be blinded as they do not feel anything during the stimulation (whether within the active or placebo group), just the care provider will know if the cable is attached or not.