Scientific Rationale for the Treatment of Cognitive Deficits from Long COVID

Current concepts in long COVID-19 brain fog and postural orthostatic tachycardia syndrome

Neurologic complications of long COVID-19 syndrome are one of the leading causes of global disability. In particular, post-COVID-19 cognitive dysfunction and dysautonomia in the form of postural orthostatic tachycardia syndrome (POTS) markedly affect patient quality of life and ability to return to work. The underlying pathophysiology of post-COVID-19 neurologic complications is unknown but is likely multifactorial with immune dysregulation and microvascular dysfunction playing central roles. Specific pathogenic factors with supportive evidence to date include cytokine-mediated inflammation, autoantibodies, immune exhaustion, disruption of the renin-angiotensin system, reduced serotonin levels, and microglial activation. The prevalence of post-COVID-19 cognitive dysfunction ranges from 10% to 88% and is affected by viral variant and hospitalization status among other factors, whereas that of long COVID-19 POTS is unknown due to referral bias and varying definitions. Treatment is largely supportive and often incorporates combined modalities. Marginal benefits with cognitive behavioral therapy, hyperbaric oxygen therapy, and supplements have been found for post-COVID-19 brain fog, whereas established POTS therapies aimed at improving venous return and reducing heart rate may reduce symptoms of long COVID-19 POTS. Although significant recovery has been noted for many cases of post-COVID-19 brain fog and POTS, prospective studies have revealed evidence of persistent symptoms and neurologic deficits a year after infection in some patients. Further studies that provide insight into the underlying pathophysiology of long COVID-19 are needed for development of target directed therapy.

SARS-CoV-2 variants mediated tissue-specific metabolic reprogramming determines the disease pathophysiology in a hamster model

Despite significant effort, a clear understanding of host tissue-specific responses and their implications for immunopathogenicity against the severe acute respiratory syndrome coronavirus2 (SARS-CoV-2) variant infection has remained poorly defined. To shed light on the interaction between tissues and SARS-CoV-2 variants, we sought to characterize the complex relationship among acute multisystem manifestations, dysbiosis of the gut microbiota, and the resulting implications for SARS-CoV-2 variant-specific immunopathogenesis in the Golden Syrian Hamster (GSH) model using multi-omics approaches. Our investigation revealed the presence of increased SARS-CoV-2 genomic RNA in diverse tissues of delta-infected GSH compared to the omicron variant. Multi-omics analyses uncovered distinctive metabolic responses between the delta and omicron variants, with the former demonstrating dysregulation in synaptic transmission proteins associated with neurocognitive disorders. Additionally, delta-infected GSH exhibited an altered fecal microbiota composition, marked by increased inflammation-associated taxa and reduced commensal bacteria compared to the omicron variant. These findings underscore the SARS-CoV-2-mediated tissue insult, characterized by modified host metabolites, neurological protein dysregulation, and gut dysbiosis, highlighting the compromised gut-lung-brain axis during acute infection.

A digital intervention for cognitive deficits following COVID-19: a randomized clinical trial

Post-COVID-19 cognitive deficits are common, persistent, and disabling. Evidence on effective treatments is limited. The goal of this study was to investigate the efficacy of a digital intervention to reduce cognitive and functional deficits in adults with persistent post-COVID-19 cognitive dysfunction. We used the remotely-delivered intervention in a randomized clinical trial conducted from July 13, 2021 to April 26, 2023. We hypothesized that participants in the intervention group would improve in measures of cognition and daily functioning. Participants were adults with cognitive deficits persisting >4 weeks following acute COVID-19 illness. Of 183 participants screened, 110 were enrolled; 98 participants (78.6% female; mean age = 48.1) completed at least one study visit. Participants were randomized 1:1 to the intervention (AKL-T01) or waitlist control. AKL-T01 is a digital therapeutic using a videogame interface to target attention and executive control. The intervention was delivered remotely for 6 weeks. The primary outcome was change in performance on a sustained attention measure (Digit Symbol Matching Task). The difference in the primary outcome between the intervention (n = 49) and controls (n = 49) was not statistically significant (F [3,261] = 0.12, p = 0.95). Secondary cognitive outcomes of task-switching (F[3,262] = 2.78, p = 0.04) and processing speed (F[3,267] = 4.57, p = 0.004) improved in the intervention relative to control. Secondary measures of functioning also improved in the intervention relative to control, including disability (F[1,82] = 4.02, p = 0.05) and quality of life (F[3,271] = 2.66, p = 0.05). Exploratory analyses showed a greater reduction in total fatigue (F[1,85] = 4.51, p = 0.04), cognitive fatigue (F[1,85] = 7.20, p = 0.009), and anxiety (F[1,87] = 7.42, p = 0.008) in the intervention relative to control. Despite the lack of improvement in sustained attention, select post-COVID-19 cognitive deficits may be ameliorated by targeted cognitive training with AKL-T01, with associated improvements in quality of life and fatigue. If replicated, the scalable nature of this digital intervention may help address substantial need for accessible, effective treatments among individuals with long COVID.

How Mild Is the Mild Long COVID? A Comprehensive Neuropsychological Assessment of Patients with Cognitive Complaints

The global impact of the Coronavirus Disease (COVID-19) pandemic has extended beyond physical health, leading to widespread mental health issues. Beyond respiratory symptoms, there is a growing concern about long-term cognitive effects, particularly in individuals who experienced mild cases of the infection. We aimed to investigate the neuropsychological aspects of long-term COVID-19 in non-hospitalized adults compared with a control group. This cross-sectional study included 42 participants, 22 individuals with a history of mild COVID, and 20 healthy controls. The participants were recruited from the community and underwent a comprehensive neuropsychological assessment. Participants from the mild COVID group reported cognitive symptoms persisting for an average of 203.86 days and presented a higher frequency of psychological treatment history (81.8%) compared with the control group (25.0%). History of anxiety disorders was more prevalent in the mild COVID group (63.6%) than in the control group (20.0%). Significant reductions in verbal working memory were observed in the mild COVID group. Levels of anxiety were found to have a significant impact on difficulties with visual recognition memory. This study reveals important neuropsychological alterations in individuals following mild COVID-19, emphasizing executive functions deficits. Our findings underscore the persistence of these deficits even in non-hospitalized cases, suggesting potential inflammatory mechanisms in the central nervous system. The study highlights the need for comprehensive assessments and targeted interventions to address the diverse cognitive impacts on individuals recovering from COVID-19.

Stress and Inflammation Target Dorsolateral Prefrontal Cortex Function: Neural Mechanisms Underlying Weakened Cognitive Control

Most mental disorders involve dysfunction of the dorsolateral prefrontal cortex (dlPFC), a recently evolved brain region that subserves working memory, abstraction, and the thoughtful regulation of attention, action, and emotion. For example, schizophrenia, depression, long COVID, and Alzheimer's disease are all associated with dlPFC dysfunction, with neuropathology often being focused in layer III. The dlPFC has extensive top-down projections, e.g., to the posterior association cortices to regulate attention and to the subgenual cingulate cortex via the rostral and medial PFC to regulate emotional responses. However, the dlPFC is particularly dependent on arousal state and is very vulnerable to stress and inflammation, which are etiological and/or exacerbating factors for most mental disorders. The cellular mechanisms by which stress and inflammation impact the dlPFC are a topic of current research and are summarized in this review. For example, the layer III dlPFC circuits that generate working memory-related neuronal firing have unusual neurotransmission, depending on NMDA receptor and nicotinic α7 receptor actions that are blocked under inflammatory conditions by kynurenic acid. These circuits also have unusual neuromodulation, with the molecular machinery to magnify calcium signaling in spines needed to support persistent firing, which must be tightly regulated to prevent toxic calcium actions. Stress rapidly weakens layer III connectivity by driving feedforward calcium-cAMP (cyclic adenosine monophosphate) opening of potassium channels on spines. This is regulated by postsynaptic noradrenergic α2A adrenergic receptor and mGluR3 (metabotropic glutamate receptor 3) signaling but dysregulated by inflammation and/or chronic stress exposure, which contribute to spine loss. Treatments that strengthen the dlPFC via pharmacological (the α2A adrenergic receptor agonist, guanfacine) or repetitive transcranial magnetic stimulation manipulation provide a rational basis for therapy.

The association between memory, COVID-19 testing, and COVID-19 incidence in middle-aged and older adults: a prospective analysis of the CLSA

We investigated the association between pre-COVID-19 memory function and (a) receipt of a COVID-19 test and (b) incidence of COVID-19 using the COVID-19 Questionnaire Study (CQS) of the Canadian Longitudinal Study on Aging (CLSA). The CQS included 28,565 middle-aged and older adults. We regressed receipt of a COVID-19 test on participants' immediate and delayed recall memory scores and re-ran the regression models with COVID-19 incidence as the outcome. All regression models were adjusted for sociodemographic, lifestyle, and health covariates. In the analytical sample (n = 21,930), higher delayed recall memory (better memory) was significantly associated with lower COVID-19 incidence. However, this association was not significant for immediate recall memory. Immediate and delayed recall memory were not associated with receipt of a COVID-19 test. Health policymakers and practitioners may viewmemory status as a potential risk for COVID-19. Memory status may not be a barrier to COVID-19 testing.

Cardiopulmonary rehabilitation's influence on cognitive functions, psychological state, and sleep quality in long COVID-19 patients: A randomized controlled trial

CLINICALTRIALS.GOV

NCT05035628.Trial registration: ClinicalTrials.gov identifier: NCT05035628..

Combined Use of Guanfacine and N-Acetylcysteine for the Treatment of Cognitive Deficits After Traumatic Brain Injury

Traumatic Brain Injury (TBI) is a significant contributor to disability across the world. TBIs vary in severity, and most cases are designated mild TBI (mTBI), involving only brief loss of consciousness and no intracranial findings on imaging. Despite this categorization, many persons continue to report persistent cognitive changes in the months to years after injury, with particular impairment in the cognitive and executive functions of the pre-frontal cortex. For these persons, there are no currently approved medications, and treatment is limited to symptom management and cognitive or behavioral therapy. The current case studies explored the use of the alpha-2A adrenoreceptor agonist, guanfacine, combined with the antioxidant, N-acetylcysteine (NAC), in the treatment of post-TBI cognitive symptoms, based on guanfacine's ability to strengthen pre-frontal cortical function, and the open-label use of NAC in treating TBI. Two persons from our TBI clinic were treated with this combined regimen, with neuropsychological testing performed pre- and post-treatment. Guanfacine + NAC improved attention, processing speed, memory, and executive functioning with minimal side effects in both persons. These results encourage future placebo-controlled trials to more firmly establish the efficacy of guanfacine and NAC for the treatment of cognitive deficits caused by TBI.

Unraveling Links between Chronic Inflammation and Long COVID: Workshop Report

As COVID-19 continues, an increasing number of patients develop long COVID symptoms varying in severity that last for weeks, months, or longer. Symptoms commonly include lingering loss of smell and taste, hearing loss, extreme fatigue, and "brain fog." Still, persistent cardiovascular and respiratory problems, muscle weakness, and neurologic issues have also been documented. A major problem is the lack of clear guidelines for diagnosing long COVID. Although some studies suggest that long COVID is due to prolonged inflammation after SARS-CoV-2 infection, the underlying mechanisms remain unclear. The broad range of COVID-19's bodily effects and responses after initial viral infection are also poorly understood. This workshop brought together multidisciplinary experts to showcase and discuss the latest research on long COVID and chronic inflammation that might be associated with the persistent sequelae following COVID-19 infection.

Greater executive dysfunction in patients post-COVID-19 compared to those not infected

BACKGROUND

A number of patients post-coronavirus disease-19 (COVID-19) report cognitive impairment (CI), even months after acute infection. We aimed to assess if COVID-19 is associated with increased incidence of CI in comparison to controls.

METHODS

We analyzed data from the Mount Sinai Health System Post-COVID-19 Registry in New York City, a prospective cohort of patients post-COVID-19 ≥18 years of age and non-infected controls. CI was defined by scores ≥ 1.0 standard deviation below population norms, and was assessed using well-validated measures of attention, working memory, processing speed, executive functioning/cognitive flexibility, language, learning, and memory. Logistic regression models assessed odds for CI in each domain in patients post-COVID-19 vs. controls after adjusting for potential confounders. In exploratory analyses, we assessed odds for CI by site of acute COVID-19 care as a proxy for disease severity.

FINDINGS

417 patients post-COVID-19 and 151 controls (mean age 49 years, 63% female, 21% Black, 17% Latinx) were included. In adjusted analyses, patients were significantly more likely than controls to have CI in executive functioning (odds ratio [OR]: 2.19; 95% confidence interval [CI]: 1.03 to 4.67), particularly those treated in outpatient (OR: 2.22; 95% CI: 1.02 to 4.82) and inpatient hospital (OR: 3.59; 95% CI: 1.27 to 10.16) settings. There were no significant associations between CI in other domains and history of COVID-19 or site of acute care.

INTERPRETATION

Patients post-COVID-19 have greater odds of executive dysfunction, suggesting that focused cognitive screening may be prudent, even in those with mild to moderate disease. Studies should explore the pathophysiology and potential treatments for CI in this population.

FUNDING

This work was funded by the Icahn School of Medicine at Mount Sinai.