Cognitive Dysfunction, Fatigue, Long COVID, Post-COVID Conditions
Conditions
Keywords
Transcranial direct current stimulation, tDCS, Brain fog, Long COVID, Chronic Fatigue, Quality of life, Cognitive impairment, Heart rate variability, PET-CT, Neuromodulation
Brief summary
Long COVID can cause persistent symptoms such as fatigue, cognitive difficulties commonly described as brain fog, reduced exercise tolerance, and impaired quality of life. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that may help modulate brain activity in regions involved in cognition, fatigue, and executive function. The NEUROSTIM-LC study will evaluate the feasibility and potential effects of repeated tDCS sessions in adults with long COVID presenting fatigue and/or brain fog. Participants will receive 30 sessions of tDCS applied over the left dorsolateral prefrontal cortex. Assessments will be performed before and after the intervention to evaluate changes in quality of life, fatigue, cognitive function, brain metabolism, physical performance, autonomic function, sleep quality, psychological symptoms, respiratory function, and blood biomarkers.
Detailed description
The NEUROSTIM-LC study is a prospective, single-arm, interventional before-and-after study designed to evaluate the feasibility, tolerability, and preliminary effects of transcranial direct current stimulation (tDCS) in patients with long COVID. The study will recruit adults aged 18 to 70 years diagnosed with long COVID according to World Health Organization criteria and presenting persistent fatigue and/or cognitive impairment commonly described as brain fog. Participants will receive 30 sessions of tDCS delivered over consecutive weeks in a controlled clinical setting. Stimulation will be applied over the left dorsolateral prefrontal cortex, with the anode positioned at F3 according to the international 10-20 EEG system and the cathode over the contralateral supraorbital region. Each session will be delivered at 2 mA for 20 minutes. Sessions will be performed on weekdays under the supervision of trained healthcare professionals, and adherence, tolerability, and adverse effects will be monitored throughout the intervention period. Assessments will be conducted at baseline and after completion of the intervention. Clinical outcomes will include health-related quality of life, fatigue, cognitive performance, sleep quality, anxiety and depression symptoms, and perceived symptom evolution. Neurobiological and physiological outcomes will include brain metabolism assessed by PET-CT, autonomic nervous system activity assessed by heart rate variability, exercise capacity assessed using the Ekblom-Bak submaximal cycle ergometer test, upper-limb muscle strength assessed by handgrip dynamometry, lower-limb neuromuscular performance assessed by countermovement jump testing, respiratory function, oxygen saturation, and routine blood biomarkers. Blood samples may also be stored for future analysis of inflammatory and oxidative stress markers. The study aims to provide preliminary information on whether repeated tDCS may be associated with measurable improvements in fatigue, brain fog, quality of life, and physiological function in patients with long COVID. The findings will help inform the design of future controlled trials evaluating non-invasive neuromodulation strategies for persistent neurological and fatigue-related symptoms after COVID-19.
Interventions
DEVICETranscranial Direct Current Stimulation
Transcranial direct current stimulation will be delivered using a constant-current stimulator through surface electrodes placed over the scalp. The anode will be positioned over the left dorsolateral prefrontal cortex, corresponding to F3 according to the international 10-20 EEG system, and the cathode will be placed over the contralateral supraorbital region. Each session will be delivered at 2 mA for 20 minutes. Participants will complete 30 sessions.
Sponsors
University of Las Palmas de Gran Canaria
Fundación Canaria Instituto de Investigación Sanitaria de Canarias
Canary Islands Health Service
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE
Masking description
No masking will be used. This is a single-arm open-label study without a sham or control group.
Intervention model description
Prospective single-arm before-and-after interventional study. All participants will receive transcranial direct current stimulation and will be assessed before and after the intervention.
Eligibility
Sex/Gender
ALL
Age
18 Years to 70 Years
Healthy volunteers
No
Inclusion criteria
* Adults aged between 18 and 70 years. * Diagnosis of long COVID according to World Health Organization criteria, defined as symptoms persisting for at least three months after acute SARS-CoV-2 infection and lasting for a minimum of two months without an alternative explanation. * Presence of persistent fatigue and/or cognitive impairment, commonly described as brain fog, attributed to long COVID and confirmed at screening. * Stable clinical condition allowing participation in the intervention and assessment procedures. * Ability to understand the study procedures and provide written informed consent.
Exclusion criteria
* Contraindications to transcranial direct current stimulation, including the presence of implanted electronic devices such as pacemakers or neurostimulators, intracranial metallic implants, or history of epilepsy or seizures. * History of neurological disorders that may affect cognitive function, including stroke, Parkinson's disease, or neurodegenerative disorders. * Pre-existing conditions associated with chronic fatigue or cognitive impairment prior to SARS-CoV-2 infection, such as fibromyalgia, chronic fatigue syndrome, or multiple sclerosis. * Severe psychiatric disorders, including psychosis or severe depression. * Substance abuse, including alcohol or drugs. * Current oncological treatment with chemotherapy or radiotherapy. * Pregnancy. * Any medical condition that, in the opinion of the investigators, may interfere with participation or with the interpretation of the results.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in EuroQol 5-Dimension 5-Level Questionnaire Score | Baseline and 3 days after completion of the 30-session tDCS intervention | Health-related quality of life will be assessed using the EuroQol 5-Dimension 5-Level questionnaire (EQ-5D-5L). The EQ-5D-5L assesses five health dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression, each rated across five levels of severity. Higher scores or index values reflect better health status, depending on the scoring method used. Changes from baseline to post-intervention will be evaluated. |
| Change in Modified Fatigue Impact Scale Score | Baseline and 3 days after completion of the 30-session tDCS intervention | Fatigue will be assessed using the Modified Fatigue Impact Scale (MFIS). The MFIS assesses the impact of fatigue on physical, cognitive, and psychosocial functioning. The total score ranges from 0 to 84, with higher scores indicating greater fatigue impact. Changes from baseline to post-intervention will be evaluated. |
| Change in Montreal Cognitive Assessment Score | Baseline and 3 days after completion of the 30-session tDCS intervention | Global cognitive function will be assessed using the Montreal Cognitive Assessment (MoCA). The MoCA evaluates cognitive domains including attention, memory, language, visuospatial abilities, executive function, abstraction, calculation, and orientation. The total score ranges from 0 to 30, with higher scores indicating better cognitive performance. Changes from baseline to post-intervention will be evaluated. |
| Change in Short Form-36 Health Survey Score | Baseline and 3 days after completion of the 30-session tDCS intervention | Health-related quality of life will be assessed using the Short Form-36 Health Survey (SF-36). The SF-36 evaluates eight domains of health-related quality of life: physical functioning, role limitations due to physical health, role limitations due to emotional problems, energy/fatigue, emotional well-being, social functioning, pain, and general health. Scores are transformed to a 0-100 scale, with higher scores indicating better health-related quality of life. Changes from baseline to post-intervention will be evaluated. |
| Change in Verbal Fluency Task Performance | Baseline and 3 days after completion of the 30-session tDCS intervention | Verbal fluency will be assessed using verbal fluency tasks. Performance will be evaluated based on the number of correct words generated within the specified time period. Higher scores indicate better verbal fluency performance. Changes from baseline to post-intervention will be evaluated. |
| Change in Stroop Test Performance | Baseline and 3 days after completion of the 30-session tDCS intervention | Executive function, inhibitory control, and cognitive flexibility will be assessed using the Stroop test. Performance will be evaluated using test-specific measures such as response accuracy and/or completion time. Better performance is reflected by higher accuracy and/or shorter completion time, depending on the scoring method used. Changes from baseline to post-intervention will be evaluated. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Change in Brain Metabolism | Baseline and 3 days after completion of the 30-session tDCS intervention | Brain metabolism will be assessed using positron emission tomography-computed tomography (PET-CT). Changes from baseline to post-intervention will be evaluated. |
| Change in Heart Rate Variability | Baseline and 3 days after completion of the 30-session tDCS intervention | Autonomic nervous system activity will be assessed using heart rate variability (HRV) recorded under resting conditions. Time-domain, frequency-domain, and non-linear HRV indices will be evaluated to characterize changes in autonomic regulation. |
| Change in Endurance Capacity | Baseline and 3 days after completion of the 30-session tDCS intervention | Endurance capacity will be assessed using the Ekblom-Bak submaximal cycle ergometer test. Heart rate responses, perceived exertion, estimated maximal oxygen uptake, and internal load will be evaluated under standardized conditions. |
| Change in Handgrip Strength | Baseline and 3 days after completion of the 30-session tDCS intervention | Upper-limb muscle strength will be assessed using handgrip dynamometry. Participants will perform three maximal attempts, and the highest value will be used for analysis. |
| Change in Lower-Limb Neuromuscular Performance | Baseline and 3 days after completion of the 30-session tDCS intervention | Lower-limb neuromuscular performance will be assessed using the countermovement jump test performed on a force platform. Variables related to force and power production will be evaluated. |
| Tolerability of the tDCS Intervention | During each tDCS session throughout the 30-session intervention period | Tolerability of the tDCS intervention will be assessed during each stimulation session using session monitoring records and participant reports. Tolerability will be evaluated based on the number of completed tDCS sessions out of the 30 scheduled sessions and the participant's ability to complete each session without clinically relevant discomfort. A higher number of completed sessions indicates greater intervention tolerability |
| Adverse Effects Related to tDCS | During each tDCS session throughout the 30-session intervention period | Adverse effects related to tDCS will be monitored and recorded at each stimulation session. Potential adverse effects include tingling, itching, headache, discomfort, burning sensation, dizziness, or transient erythema at the electrode site. The presence, type, and severity of adverse effects will be documented. Severity will be classified as mild, moderate, or severe. |
Contacts
CONTACTJuan Francisco Vigueras, MD
CONTACTDavid Morales Álamo, PhD
PRINCIPAL_INVESTIGATORJuan Francisco Vigueras, MD
Canary Islands Health Service
Outcome results
None listed