Effects of a single session of transcranial direct current stimulation (tDCS) on cognitive function in patients with COVID-19: a randomized clinical trial

Abstract

Introduction: Individuals affected by COVID-19 may present with neurological symptoms and cognitive changes, but the physiological mechanisms of such impairments, as well as therapeutic intervention, are not yet well established. Therefore, the development and evaluation of methods for managing the disease are necessary. In recent years, Transcranial Direct Current Stimulation (tDCS) has been widely used to improve cognitive performance in different pathologies, demonstrating beneficial effects in various cognitive domains such as working memory, attention, and executive function. Objective: This study aimed to assess the effects and safety of a single session of tDCS on the left dorsolateral prefrontal cortex (CPFDL) on the cognitive performance of patients infected with SARS-CoV-2. Methods: A randomized controlled clinical trial was carried out in which 40 individuals with confirmed COVID-19 infection admitted to a semi-intensive unit were included in the study and divided into two groups, sham-tDCS and real-tDCS. The intervention protocol consisted of a single tDCS session. The current intensity was 2mA, and the stimulation duration was 30 minutes in the left CPFDL area. The cognitive tests, Trail Test and Digit Span, were applied before and after the tDCS session, and their durations and scores were converted into Z-scores. At the end of the experimental protocol, a standardized questionnaire was applied to analyze the occurrence of adverse effects of tDCS on patients. In addition, were also analyzed: vital signs before and after stimulation, presence of severe skin lesions at the current application site, fall events, and occurrence of clinical worsening, including transfer to ICU, orotracheal intubation, and death within one hour after the intervention. Results: The main results showed no significant differences between sham and real-tDCS groups for execution time in both TMT A and B, and for Digit Span score. Regarding safety, there was no significant difference between the groups in the frequency and intensity of adverse effects after stimulation. The analysis of vital signs indicated a trend (p=0.057) of increased peripheral oxygen saturation for the tDCS-real group at the post-intervention moment. There were no episodes of falls, transfers to the ICU, orotracheal intubation, or deaths after stimulation. Conclusion: The present study revealed that a tDCS session on the CPFDL of hospitalized patients with Covid-19 proved to be a safe and tolerable technique. However, no alterations were observed in the patients' executive function and working memory. More research is needed to assess the effectiveness of tDCS on the cognition of patients affected by Covid-19. Future studies with repeated sessions evaluated through a greater number of neuropsychological tests may provide more robust results