Cognitive decline following acute viral infections: literature review and projections for post-COVID-19

Respiratory syncytial virus pulmonary infections in adults - disease burden and prevention

PURPOSE OF REVIEW

We highlight the evolving understanding of the burden of respiratory syncytial virus (RSV) in older adults and recent data on the three new vaccines.

RECENT FINDINGS

As well as a greater recognition of the amount of RSV infection in adults, and especially over 60 years of age, there has been a significant amount of study detailing the postacute burden including excess cardiovascular disease and loss of physical and cognitive functioning. Three new RSV vaccines now have published data for two seasons, and while direct comparison is not possible due to differences in the timing, methodology and populations studies, all show good efficacy with no serious side effects of concern.

SUMMARY

RSV causes a substantial amount of morbidity and mortality in older adults with both acute and longer term impacts. With effective vaccines now available clinicians should be advocating with their patients to prevent RSV infection.

Identification of circulating risk biomarkers for cognitive decline in a large community-based population in Chongqing China

INTRODUCTION

This study aims to investigate the relationship between blood-based pathologies and established risk factors for cognitive decline in the community-based population of Chongqing, a region with significant aging.

METHODS

A total of 26,554 residents aged 50 years and older were recruited. Multinomial logistic regression models were applied to assess the risk factors of cognition levels. Propensity score matching and linear mixed effects models were used to evaluate the relationship between key risk factors and the circulating biomarkers.

RESULTS

Shared and distinct risk factors for MCI and dementia were identified. Age, lower education, medical history of stroke, hypertension, and epilepsy influenced mild cognitive impairment (MCI) progression to dementia. Correlations between key risk factors and circulating neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), amyloid β protein (Aβ)40, and Aβ42/Aβ40 ratio suggest underlying mechanisms contributing to cognitive impairment.

DISCUSSION

The common and distinct risk factors across cognitive decline stages emphasize the need for tailored interventions. The correlations with blood biomarkers provide insights into potential management targets.

HIGHLIGHTS

From a large community-based cohort study on the residents in Chongqing, we have identified that mild cognitive impairment (MCI) and dementia share several common risk factors, including age, female gender, rural living, lower education levels, and a medical history of stroke. However, each condition also has its own unique risk factors. Several factors contribute to the progression of MCI into dementia including age, education levels, occupation, and a medical history of hypertension and epilepsy. We discover the correlations between the risk factors for dementia and blood biomarkers that indicate the presence of axonal damage, glial activation, and Aβ pathology.

Association between COVID-19 infection and new-onset dementia in older adults: a systematic review and meta-analysis

BACKGROUND

The relationship between COVID-19 infection and a possible increased likelihood of older adults developing new-onset dementia (NOD) remains elusive.

METHODS

A thorough search was performed across several databases including MEDLINE/PubMed, PsycINFO, Scopus, medRxiv, and PQDT Global for studies published in English from January 2020 to December 2023. Only original investigations exploring the link between COVID-19 infection and NOD were selected for inclusion. We assessed the risk of developing NOD, using Risk Ratio (RR) for measurement. Control groups were categorized as: (i) a non-COVID cohort with other respiratory infections [control group (C1)]; and (ii) a non-COVID cohort with otherwise unspecified health status [control group (C2)]. Follow-up periods were divided into intervals of 3, 6, 12, and 24 months post-COVID.

RESULTS

11 studies (involving 939,824 post-COVID-19 survivors and 6,765,117 controls) were included in the review. Across a median observation period of 12 months post-COVID, the overall incidence of NOD was about 1.82% in the COVID-infected group, compared to 0.35% in the non-COVID-infected group. The overall pooled meta-analysis showed a significantly increased NOD risk among COVID-19 older adult survivors compared to non-COVID-19 controls (RR = 1.58, 95% CI 1.21-2.08). Similar increased NOD risks were observed in subgroup analyses restricted to an observational period of 12 months (RR = 1.56, 95% CI 1.21-2.01), as well as in five studies that employed propensity score matching to sufficiently and effectively control for multiple confounding covariates (RR = 1.46, 95% CI 1.10-1.94). COVID-19 group and C1 group shared a comparably increased risk of developing NOD (overall RR = 1.13, 95% CI 0.92-1.38).

DISCUSSION

Under normal circumstances, we believe that COVID-19 infection is likely to be a risk factor for developing NOD in older adults over time. While the increased NOD risk due to COVID-19 infection appears to be similar to that associated with other respiratory infections, it warrants and necessitates investigation with longer observations.

A Two-Year cohort study examining the impact of cytokines and chemokines on cognitive and psychiatric outcomes in Long-COVID-19 patients

This study investigates the relationship between clinical, sociodemographic, and neuropsychological symptoms and serum cytokine concentrations with long-term cognitive and psychiatric outcomes in long-COVID-19 patients. We reassessed 108 adults who survived moderate to severe COVID-19 at two intervals post-discharge (T1, mean 6.9 months; T2, mean 23.5 months). Baseline sociodemographic and clinical data were collected from hospital records, while cognitive and mental health assessments included psychometric tests such as the Hospital Anxiety and Depression Scale (HADS) and Immediate and Delayed Recall Tests from the CERAD Battery. Serum cytokine levels were measured at T1. Generalized Additive Models (GAMs), Elastic Net Regression (NET), and Psychological Network Analysis (PNA) were used to analyze the data. The GAM analysis revealed significant associations between acute COVID-19 severity and Epworth Sleepiness Score with persistent anxiety symptoms at T2. For depression, both WHO severity class and Eotaxin levels were significant predictors. The Anti-inflammatory Index showed a marginally significant relationship with immediate recall, while age was marginally associated with delayed recall performance. In NET, only anxiety was significantly associated with Epworth Sleepiness Score, WHO severity class, and Proinflammatory Index. PNA did not reveal direct connections between cytokines and neuropsychological outcomes in the graphical model. However, centrality measures indicated that the Proinflammatory Index and VEGF were more central within the network, suggesting they might be important components of the overall system. This study provides insights into the complex role of cytokines and inflammation in long-COVID-19 outcomes, potentially aiding in the identification of biomarkers for diagnosis and prognosis.

Six-month follow-up of multidomain cognitive impairment in non-hospitalized individuals with post-COVID-19 syndrome

Some people infected with SARS-CoV-2 report persisting symptoms following acute infection. If these persist for over three months, they are classified as post-COVID-19 syndrome (PCS). Although PCS is frequently reported, detailed longitudinal neuropsychological characterization remains scarce. We aimed to describe the trajectory of cognitive and neuropsychiatric PCS symptoms. 42 individuals with persisting cognitive deficits after asymptomatic to mild/moderate acute COVID-19 at study inclusion received neuropsychological assessment at baseline (BL) and follow-up (FU; six months after BL). Assessments included comprehensive testing of five neurocognitive domains, two cognitive screening tests, and questionnaires on depression, anxiety, sleep, fatigue, and health-related quality of life. Results showed high rates of subjective cognitive complaints at BL and FU (95.2% versus 88.1%) without significant change over time. However, objectively measured neurocognitive disorder (NCD) decreased (61.9% versus 42.9%). All cognitive domains were affected, yet most deficits were found in learning and memory, followed by executive functions, complex attention, language, and perceptual motor functions. In individuals with NCD, the first three domains mentioned improved significantly over time, while the last two domains remained unchanged. Cognitive screening tests did not prove valuable in detecting impairment. Neuropsychiatric symptoms remained constant except for quality of life, which improved. This study emphasizes the importance of comprehensive neuropsychological assessment in longitudinal research and provides valuable insights into the trajectory of long-term neuropsychological impairments in PCS. While cognitive performance significantly improved in many domains, neuropsychiatric symptoms remained unchanged.

The population based cognitive testing in subjects with SARS-CoV-2 (POPCOV2) study: longitudinal investigation of remote cognitive and fatigue screening in PCR-positive cases and negative controls

Background

The majority of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) only show mild respiratory symptoms. However, some patients with SARS-CoV-2 display neurological symptoms. Data on the exact prevalence and course of cognitive symptoms are often limited to patient reported outcomes or studies recruited at specialized centers.

Methods

For this prospective, non-interventional population based POPCOV2 study, 156 subjects who performed SARS-CoV-2 testing in the Düsseldorf metropolitan area at public test centers between December 2020 and February 2022 were recruited by handouts. SARS-CoV-2-positive and negatively tested subjects were included within the first seven days after the PCR test results. Cognitive testing was performed at baseline during home quarantine and after 4-6 as well as 12-14 weeks of follow-up. Individuals were examined remotely by videocalls using the Symbol Digit Modalities Test (SDMT) and the Montreal Cognitive Assessment (MoCA) in addition to the Brief Fatigue Inventory (BFI) and the Beck Depression Inventory-Fast Screen (BDI-FS).

Results

At baseline, the SARS-CoV-2-positive group presented with higher levels of fatigue in the BFI. In both the SARS-CoV-2-positive and SARS-CoV-2-negative groups, some subjects presented attention and memory deficits, defined as a z-score < -1,65 on the SDMT or < 26 points on the MoCA (SDMT: 22.9% in the positive and 8.8% in the negative group, p = 0.024; MoCA: 35.6% in the positive and 27.3% in the negative group, p = 0.313). MoCA and SDMT improved over time in both groups. For MoCA scores, a significant difference between the two groups was only seen at the first follow-up. SDMT z-scores did not differ at any time between the groups.

Conclusion

These results support previous evidence that mild SARS-CoV-2 infections are associated with increased fatigue. However, we found relevant rates of cognitive impairment not only in the infected but also in the control group. This underlines the importance of including a control group in such investigations.

Hypertension and Cognitive Dysfunction in a Pregnant Rat Model of PE; a Role for CD4+ T Cells

OBJECTIVE

Preeclampsia (PE) is associated with hypertension (HTN) during pregnancy and activated CD4+ T cells, inflammatory cytokines, and autoantibodies to the angiotensin II type I receptor (AT1-AA). Having had COVID-19 (CV) during pregnancy is associated with an increased incidence of a PE-like phenotype. Both PE and CV have long-lasting neurological implications and studies show that nonpregnant COVID patients produce AT1-AA. We have shown that CD4+ T cells from PE women cause a PE phenotype in nude athymic rats. In this study, we sought to examine the role of CD4+ T cells from PE with a CV History (Hx) to contribute to a PE phenotype and to determine the importance of CD4+ T cells in cognitive dysfunction during pregnancy.

METHODS

At delivery, blood and placentas were collected, and one million placental CD4+ T cells from each PE and each normotensive patient, with (NT) or without (NP) a CV (Hx) during pregnancy, were isolated, purified, and injected i.p. into a gestational day (GD) 12 pregnant nude athymic rat (one patient/rat). At GD19, blood pressure (MAP) and circulating factors were assessed in recipient rats. Cognitive function and memory were assessed using Novel Object Recognition and Barnes Maze tests, respectively. Placental ACE-2 activity and AT1-AA were measured from COVID Hx patients. A one- or two-way ANOVA with Bonferroni's multiple comparisons test was used for statistical analysis.

RESULTS

Blood pressure was increased in patients with PE, with or without COVID, compared to NT patients. There were no significant changes in placental ACE activity in patients with COVID Hx with or without PE. AT1-AA was elevated in PE patients and in both PE and NT COVID Hx compared to control NP. In pregnant recipient rats, MAP increased in CV Hx PE (113 ± 2, n = 8) compared to CV Hx NT (101 ± 5, n = 6). PE and PE CV Hx CD4+ T Cell recipient rats exhibited impaired memory and cognitive dysfunction (p < 0.05), compared to control groups. Recipient rats of PE CV Hx CD4+ T cells had elevated AT1-AA compared to NT CV Hx recipients. Both COVID Hx groups and recipients of PE CD4+ T cells had elevated TNF alpha compared to NP.

CONCLUSION

Our findings indicate that pregnant patients with a Hx of COVID during pregnancy produce AT1-AA, with or without PE. Recipients of CD4+ T cells from PE with or without a CV Hx during pregnancy cause HTN and elevated AT1-AA. TNF-α is elevated in PE and in CV Hx NT and PE recipients. Interestingly, recipients of T cells from PE patients with or without a Hx of CV had worse cognitive function during pregnancy, compared to recipient rats of NP CD4+ T cells. These data demonstrate the importance of CD4+ T cells in HTN and impaired neurological function during PE in the presence or absence of a prior COVID-19 infection during pregnancy.

Impact of dengue fever on depression, anxiety, and stress symptoms in Esmeraldas Province, Ecuador: a prospective cohort study

BACKGROUND

Physical symptoms of dengue have been documented extensively, but knowledge gaps on dengue-associated mental health hazards remain. We investigated the frequency of psychiatric symptoms (depression, anxiety, and stress) and neurocognitive performance during the first year after a dengue episode.

METHODS

Using DASS-21 scores at 3, 6, and 12 months, we assessed depression, anxiety, and stress in anti-dengue IgM-positive adults and matched controls during the 2021 dengue season in Esmeraldas Province, Ecuador. Patients with DASS-21 scores ≤ 4 were considered normal; those with scores of 5-7, 8-10, and ≥ 11 indicated mild, moderate, and severe depression, respectively; cutoff scores for anxiety and stress were ≥ 5 and ≥ 9, respectively. We also assessed 'delayed matching to sample' (DMS) and 'spatial working memory' (SWM) using the Cambridge Neuropsychological Test Automated Battery.

RESULTS

We enrolled 102 cases and 78 controls. At 3 months, 90 cases and 70 controls were available for follow-up, among these 40/90 (44.4%) cases and 12/70 (17.1%) controls had DASS-21 scores ≥ 5 (RR 2.7, 95% CI [1.5-4.7]). Dengue remained a predictor for depression after adjusting for age, sex, and COVID-19 status. We observed no difference in anxiety between the groups, but stress scores increased at month 3 (RR 1.87, 95% CI [1.01-3.4]). DASS-21 scores normalized during follow-up. DMS and SWM did not differ between groups at 3 and 6 months. At month 12, cases had lower SWM than controls did (p value < 0.001).

CONCLUSIONS

Care providers should be aware of dengue-associated mood disorders and facilitate timely referral to mental health services. Future longitudinal studies are warranted to validate our observations regarding the impact of dengue on mental health and neurocognitive status in affected patients.

Viral infections in etiology of mental disorders: a broad analysis of cytokine profile similarities - a narrative review

The recent pandemic caused by the SARS-CoV-2 virus and the associated mental health complications have renewed scholarly interest in the relationship between viral infections and the development of mental illnesses, a topic that was extensively discussed in the previous century in the context of other viruses, such as influenza. The most probable and analyzable mechanism through which viruses influence the onset of mental illnesses is the inflammation they provoke. Both infections and mental illnesses share a common characteristic: an imbalance in inflammatory factors. In this study, we sought to analyze and compare cytokine profiles in individuals infected with viruses and those suffering from mental illnesses. The objective was to determine whether specific viral diseases can increase the risk of specific mental disorders and whether this risk can be predicted based on the cytokine profile of the viral disease. To this end, we reviewed existing literature, constructed cytokine profiles for various mental and viral diseases, and conducted comparative analyses. The collected data indicate that the risk of developing a specific mental illness cannot be determined solely based on cytokine profiles. However, it was observed that the combination of IL-8 and IL-10 is frequently associated with psychotic symptoms. Therefore, to assess the risk of mental disorders in infected patients, it is imperative to consider the type of virus, the mental complications commonly associated with it, the predominant cytokines to evaluate the risk of psychotic symptoms, and additional patient-specific risk factors.

Herpes zoster and long-term risk of subjective cognitive decline

BACKGROUND

Herpes zoster (HZ), commonly known as "shingles," may contribute to cognitive decline through mechanisms such as neuroinflammation or direct neuronal injury. However, evidence on the longitudinal association between HZ and cognitive decline is conflicting and whether the risk differs by APOE ε4-carrier status has not been studied; prospective cohort studies on the association between HZ vaccination and cognitive decline are also lacking.

METHODS

We included 149,327 participants from three large cohorts-the Nurses' Health Study (NHS), NHSII, and Health Professionals Follow-Up Study (HPFS)-to prospectively examine the association between HZ and subsequent subjective cognitive decline (SCD). Poisson regression was used to estimate the multivariable-adjusted relative risk (MVRR) of a 3-unit increment in SCD score according to years since HZ compared with participants with no history of HZ.

RESULTS

Compared with individuals with no history of HZ, the MVRR (95% CI) of a 3-unit increment in SCD score was significantly and independently higher among individuals with a history of HZ, but the duration of time since HZ when the elevated risk of SCD was statistically significant differed among the cohorts. In NHS, HZ was associated with higher long-term risk of SCD; compared with individuals with no history of HZ, the MVRR (95% CI) of a 3-unit increment in SCD score was 1.14 (1.01, 1.32) for ≥ 13 years since HZ. In NHS II, HZ was associated with higher risk of SCD in both the short-term [MVRR 1.34 (1.18, 1.53) for 1-4 years] and long-term [MVRR 1.20 (1.08, 1.34) for ≥ 13 years since HZ]. In HPFS, an elevated risk of SCD was suggested across all time points. Among the subset of participants with information on APOE ε4, there was a suggestion that the association differed by APOE ε4 carrier status, but the results were not consistent between women and men. Among the subset of women with information on HZ vaccination, there was a suggestion that the long-term risk of SCD may be greater among women who were not vaccinated against HZ.

CONCLUSIONS

Data from three large independent cohorts of women and men showed that HZ was associated with higher long-term risk of SCD, and the risk may differ by APOE ε4-carrier status.

Systemic immune challenge exacerbates neurodegeneration in a model of neurological lysosomal disease

Mucopolysaccharidosis type IIIA (MPS IIIA) is a rare paediatric lysosomal storage disorder, caused by the progressive accumulation of heparan sulphate, resulting in neurocognitive decline and behavioural abnormalities. Anecdotal reports from paediatricians indicate a more severe neurodegeneration in MPS IIIA patients, following infection, suggesting inflammation as a potential driver of neuropathology. To test this hypothesis, we performed acute studies in which WT and MPS IIIA mice were challenged with the TLR3-dependent viral mimetic poly(I:C). The challenge with an acute high poly(I:C) dose exacerbated systemic and brain cytokine expression, especially IL-1β in the hippocampus. This was accompanied by an increase in caspase-1 activity within the brain of MPS IIIA mice with concomitant loss of hippocampal GFAP and NeuN expression. Similar levels of cell damage, together with exacerbation of gliosis, were also observed in MPS IIIA mice following low chronic poly(I:C) dosing. While further investigation is warranted to fully understand the extent of IL-1β involvement in MPS IIIA exacerbated neurodegeneration, our data robustly reinforces our previous findings, indicating IL-1β as a pivotal catalyst for neuropathological processes in MPS IIIA.

An Integrative Approach to the Study of Cognitive Abilities in a Non-Human Primate Model in a Virology Laboratory Environment

Non-human primates, due to their similarities in immune response to humans, are the preferred model for studying infectious processes and any associated cognitive impairments. Behavioral tests are indispensable for investigating pathogenesis in neuroinfections, especially those that do not manifest with noticeable clinical symptoms, as well as in the transition to a chronic form of the disease. Modeling viral infection requires specialized experimental conditions. Our work describes techniques for investigating mnemonic functions, tiredness, attentional focus, quick-wittedness, and basic behavioral responses in primates under the assumed conditions for infections with viruses that do not have an airborne route of transmission. It also outlines approaches to the training and selection of primates for virological research, as well as analyzing gender differences in learning abilities, the impact of housing conditions on the results, and the correlation between training success and behavioral test scores. These methods will allow a more detailed study of non-human primates as a model for researching cognitive and behavioral impairments under infectious and immune stress, as well as the design of less energy-intensive experiments for evaluating the efficacy and safety of therapeutic and prophylactic strategies at early stages of infection.

Understanding the olfactory role in post-COVID cognitive and neuropsychiatric manifestations

Introduction

Olfactory dysfunction (OD) is frequent after SARS-CoV-2 infection. The aim of this study was to examine if long-term OD is common in post-COVID condition, and the relationship between olfaction, cognition, neuropsychiatric symptoms, and disease duration in these patients.

Methods

This study included 121 participants with post-COVID condition and 51 healthy controls (HC). A comprehensive neuropsychological and neuropsychiatric assessment was conducted, encompassing various domains, including general cognition, processing speed, verbal fluency, attention, verbal memory, visual memory, visuoconstructive ability, visuospatial ability, abstraction, executive functions, anxious-depressive symptoms, general health perception, fatigue level, sleep quality, and olfaction. Statistical analyses were carried out to understand the relationship of OD with cognition, and its role as moderator variable.

Results

In total, 25% of the post-covid patients had a reduced smell capacity, while only 9.3% of HC presented OD. Post-COVID patients had statistically significantly worse cognitive performance and clinical status than HC. Verbal fluency (AUC = 0.85, p < 0.001), and attention (AUC = 0.82, p < 0.001) were the variables that best discriminate between groups. OD seemed to be a moderator between fatigue and cognition, and between disease duration and attention (β = -0.04; p = 0.014).

Discussion

The study highlights marked cognitive and neuropsychiatric sequelae in individuals post-COVID relative to HC. Olfactory impairment exhibits correlations with both cognitive performance and general health. Olfaction emerges as a potential prognostic marker owing to its moderating influence on disease severity indicators.

Associations between olfactory dysfunction and cognition: a scoping review

INTRODUCTION

Strong evidence suggests that olfactory dysfunction (OD) can predict additional neurocognitive decline in neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. However, research exploring olfaction and cognition in younger populations is limited. The aim of this review is to evaluate cognitive changes among non-elderly adults with non-COVID-19-related OD.

METHODS

We performed a structured comprehensive literature search of PubMed, Ovid Embase, Web of Science, and Cochrane Library in developing this scoping review. The primary outcome of interest was the association between OD and cognitive functioning in adults less than 60 years of age.

RESULTS

We identified 2878 studies for title and abstract review, with 167 undergoing full text review, and 54 selected for data extraction. Of these, 34 studies reported on populations of individuals restricted to the ages of 18-60, whereas the remaining 20 studies included a more heterogeneous population with the majority of individuals in this target age range in addition to some above the age of 60. The etiologies for smell loss among the included studies were neuropsychiatric disorders (37%), idiopathic cause (25%), type 2 diabetes (7%), trauma (5%), infection (4%), intellectual disability (4%), and other (18%). Some studies reported numerous associations and at times mixed, resulting in a total number of associations greater than the included number of 54 studies. Overall, 21/54 studies demonstrated a positive association between olfaction and cognition, 7/54 demonstrated no association, 25/54 reported mixed results, and only 1/54 demonstrated a negative association.

CONCLUSION

Most studies demonstrate a positive correlation between OD and cognition, but the data are mixed with associations less robust in this young adult population compared to elderly adults. Despite the heterogeneity in study populations and outcomes, this scoping review serves as a starting point for further investigation on this topic. Notably, as many studies in this review involved disorders that may have confounding effects on both olfaction and cognition, future research should control for these confounders and incorporate non-elderly individuals with non-psychiatric causes of smell loss.

Antigen non-specific CD8+ T cells accelerate cognitive decline in aged mice following respiratory coronavirus infection

Primarily a respiratory infection, numerous patients infected with SARS-CoV-2 present with neurologic symptoms, some continuing long after viral clearance as a persistent symptomatic phase termed "long COVID". Advanced age increases the risk of severe disease, as well as incidence of long COVID. We hypothesized that perturbations in the aged immune response predispose elderly individuals to severe coronavirus infection and post-infectious sequelae. Using a murine model of respiratory coronavirus, mouse hepatitis virus strain A59 (MHV-A59), we found that aging increased clinical illness and lethality to MHV infection, with aged animals harboring increased virus in the brain during acute infection. This was coupled with an unexpected increase in activated CD8+ T cells within the brains of aged animals but reduced antigen specificity of those CD8+ T cells. Aged animals demonstrated spatial learning impairment following MHV infection, which correlated with increased neuronal cell death and reduced neuronal regeneration in aged hippocampus. Using primary cell culture, we demonstrated that activated CD8+ T cells induce neuronal death, independent of antigen-specificity. Specifically, higher levels of CD8+ T cell-derived IFN-γ correlated with neuronal death. These results support the evidence that CD8+ T cells in the brain directly contribute to cognitive dysfunction following coronavirus infection in aged individuals.

Exploring the relationship of cognitive function with and without COVID-19 recovered schizophrenic patients

Background

The Coronavirus disease 2019 (COVID-19) is linked to the deterioration of cognitive function among individuals suffering from schizophrenia. The purpose of this study was to compare the cognitive performance of schizophrenic patients before and after COVID-19.

Methods

A longitudinal cohort study involving a sample of 219 individuals diagnosed with schizophrenia was enrolled between June 2022 and May 2023. The participants were split into two groups infected with COVID-19 (n = 165) and not infected with COVID-19 (n = 54). The data were gathered via a questionnaire on demographic characteristics, the Brief Assessment of Cognition in Schizophrenia (BACS), the Positive and Negative Syndrome Scale (PANSS), the Calgary Depression Scale for Schizophrenia (CDSS), the Activities of Daily Living (ADL) scale, and the Insomnia Severity Index (ISI).

Results

The repeated-measures ANOVA showed that Among patients diagnosed with COVID-19, there was a deterioration in global cognitive function (before COVID-19 = -2.45 vs. after COVID-19 = -3.02, p = 0.007), working memory (before COVID-19 = -2.76 vs. after COVID-19 = -3.34, p < 0.00 1), motor speed (before COVID-19 = -1.64 vs. after COVID-19 = -2.12, p < 0.001), attention and speed of information processing (before COVID-19 = -1.93 vs. after COVID-19 = -1.16, p = 0.008). multi-variable analysis showed that several factors as having a secondary grade of education (β = 0.434), experiencing insomnia (β = 0.411)and the interaction between COVID-19 diagnosis and cognition at baseline (β = 0.796) were significantly associated with cognitive deficits. At the same time, no significant associations were found between global cognition and clinical symptoms, autonomy, or depression (p > 0.05).

Conclusion

The COVID-19 pandemic has significantly impacted various cognitive functions, such as verbal memory, working memory, and global cognition. Insomnia has been identified as the predominant determinant of cognitive impairment, alongside the confirmation of a COVID-19 diagnosis. Additional research is imperative to elucidate the diversification of cognitive functionality observed in individuals diagnosed with schizophrenia who have acquired COVID-19.

Astrocytes as Drivers and Disruptors of Behavior: New Advances in Basic Mechanisms and Therapeutic Targeting

Astrocytes are emerging as key regulators of cognitive function and behavior. This review highlights some of the latest advances in the understanding of astrocyte roles in different behavioral domains across lifespan and in disease. We address specific molecular and circuit mechanisms by which astrocytes modulate behavior, discuss their functional diversity and versatility, and highlight emerging astrocyte-targeted treatment strategies that might alleviate behavioral and cognitive dysfunction in pathologic conditions. Converging evidence across different model systems and manipulations is revealing that astrocytes regulate behavioral processes in a precise and context-dependent manner. Improved understanding of these astrocytic functions may generate new therapeutic strategies for various conditions with cognitive and behavioral impairments.

Prevalence of active cytomegalovirus infection at diagnosis of ovarian cancer and during chemotherapy and subsequent changes in cognitive functioning

PURPOSE

One of the most frequently reported effects of cancer and its treatments is cancer-related cognitive impairment (CRCI). Viral infections may affect inflammation and immune function and therefore may influence patient symptoms, including CRCI. The goal of this study was to describe the prevalence of cytomegalovirus (CMV) infections at diagnosis, during, and after chemotherapy in individuals with ovarian cancer and explore CMV infection at diagnosis with cancer-related cognitive impairment (CRCI) following chemotherapy.

METHODS

We recruited adults newly diagnosed with ovarian, primary peritoneal or fallopian tube cancer at a single academic cancer center into two prospective studies. In Study 1 (N = 71), participants provided blood samples at diagnosis. In Study 2 (N = 18), participants provided blood samples and completed symptom surveys before, during and after front-line adjuvant chemotherapy. Serum CMV DNA levels were assessed using digital PCR; >100 copies/mL of serum was considered positive for active CMV infection (CMV+). CRCI was measured using the Functional Assessment of Cancer Therapy - Cognitive Function (FACT-Cog) questionnaire. Changes in FACT-Cog scores were compared by CMV status at diagnosis using t-tests at each time point.

RESULTS

At diagnosis, 29.2% were CMV+ (28.2% in Study 1, 33.3% in Study 2). Following three cycles of chemotherapy (Study 2), CMV positivity rose to 60.0% and then back down to 31.3% after chemotherapy. We observed significant differences in CRCI following chemotherapy by CMV status at diagnosis.

CONCLUSION

Our data suggest that active CMV infection is common among patients undergoing treatment for ovarian cancer and may contribute to symptoms of CRCI.

Arketamine for cognitive impairment in psychiatric disorders

Cognitive impairment has been observed in patients with various psychiatric disorders, including schizophrenia, major depressive disorder (MDD), and bipolar disorder (BD). Although modern therapeutic drugs can improve certain symptoms (i.e., psychosis, depression) in these patients, these drugs have not been found to improve cognitive impairment. The N-methyl-D-aspartate receptor antagonist (R,S)-ketamine has attracted attention as a rapidly acting antidepressant. In addition to its robust antidepressant effects, (R,S)-ketamine has been suggested to improve cognitive impairment in patients with MDD and BD, despite causing cognitive impairment in healthy control subjects. (R,S)-ketamine is a racemic mixture of equal amounts of (R)-ketamine (or arketamine) and (S)-ketamine (or esketamine). Arketamine has been found to have more potent antidepressant-like actions than esketamine in rodents. Interestingly, arketamine, but not esketamine, has been suggested to improve phencyclidine-induced cognitive deficits in mice. Furthermore, arketamine has been suggested to ameliorate cognitive deficits in rodent offspring after maternal immune activation. In the current article, it is proposed that arketamine has therapeutic potential for treating cognitive impairment in patients with psychiatric disorders. Additionally, the potential role of the gut-microbiome-brain axis in cognitive impairment in psychiatric disorders is discussed.

T cell exhaustion is associated with cognitive status and amyloid accumulation in Alzheimer's disease

Studies over the last 100 years have suggested a link between inflammation, infectious disease, and Alzheimer's Disease (AD). Understanding how the immune system changes during the development of AD may facilitate new treatments. Here, we studied an aging cohort who had been assessed for AD pathology with amyloid positron emission tomography and cognitive testing, and conducted high dimensional flow cytometry on peripheral blood mononuclear and cerebrospinal fluid cells. Participants were assigned a classification of being amyloid negative cognitively normal, amyloid positive cognitively normal (APCN), or amyloid positive mild cognitive impairment (APMCI), an early stage of AD. We observed major alterations in the peripheral innate immune system including increased myeloid and plasmacytoid dendritic cells in the blood of APMCI participants. When the adaptive immune system was examined, amyloid positive participants, regardless of cognitive status, had increased CD3+ T cells. Further analyses of CD4+ and CD8+ T cells revealed that APMCI participants had an increase in more differentiated phenotype T cells, such as effector memory and effector memory CD45RA expressing (TEMRA), compared to those with normal cognition. When T cell function was measured, we observed that T cells from APCN participants had increased IFNγ+GzB- producing cells compared to the other participants. In contrast, we demonstrate that APMCI participants had a major increase in T cells that lacked cytokine production following restimulation and expressed increased levels of PD-1 and Tox, suggesting these are exhausted cells. Rejuvenation of these cells may provide a potential treatment for AD.

Neurological manifestations of SARS-CoV-2: complexity, mechanism and associated disorders

BACKGROUND

Coronaviruses such as Severe Acute Respiratory Syndrome coronavirus (SARS), Middle Eastern Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) are associated with critical illnesses, including severe respiratory disorders. SARS-CoV-2 is the causative agent of the deadly COVID-19 illness, which has spread globally as a pandemic. SARS-CoV-2 may enter the human body through olfactory lobes and interact with the angiotensin-converting enzyme2 (ACE2) receptor, further facilitating cell binding and entry into the cells. Reports have shown that the virus can pass through the blood-brain barrier (BBB) and enter the central nervous system (CNS), resulting in various disorders. Cell entry by SARS-CoV-2 largely relies on TMPRSS2 and cathepsin L, which activate S protein. TMPRSS2 is found on the cell surface of respiratory, gastrointestinal and urogenital epithelium, while cathepsin-L is a part of endosomes.

AIM

The current review aims to provide information on how SARS-CoV-2 infection affects brain function.. Furthermore, CNS disorders associated with SARS-CoV-2 infection, including ischemic stroke, cerebral venous thrombosis, Guillain-Barré syndrome, multiple sclerosis, meningitis, and encephalitis, are discussed. The many probable mechanisms and paths involved in developing cerebrovascular problems in COVID patients are thoroughly detailed.

MAIN BODY

There have been reports that the SARS-CoV-2 virus can cross the blood-brain barrier (BBB) and enter the central nervous system (CNS), where it could cause a various illnesses. Patients suffering from COVID-19 experience a range of neurological complications, including sleep disorders, viral encephalitis, headaches, dysgeusia, and cognitive impairment. The presence of SARS-CoV-2 in the cerebrospinal fluid (CSF) of COVID-19 patients has been reported. Health experts also reported its presence in cortical neurons and human brain organoids. The possible mechanism of virus infiltration into the brain can be neurotropic, direct infiltration and cytokine storm-based pathways. The olfactory lobes could also be the primary pathway for the entrance of SARS-CoV-2 into the brain.

CONCLUSIONS

SARS-CoV-2 can lead to neurological complications, such as cerebrovascular manifestations, motor movement complications, and cognitive decline. COVID-19 infection can result in cerebrovascular symptoms and diseases, such as strokes and thrombosis. The virus can affect the neural system, disrupt cognitive function and cause neurological disorders. To combat the epidemic, it is crucial to repurpose drugs currently in use quickly and develop novel therapeutics.

Antigen-specific and cross-reactive T cells in protection and disease

Human T cells have a diverse T-cell receptor (TCR) repertoire that endows them with the ability to identify and defend against a broad spectrum of antigens. The universe of possible antigens that T cells may encounter, however, is even larger. To effectively surveil such a vast universe, the T-cell repertoire must adopt a high degree of cross-reactivity. Likewise, antigen-specific and cross-reactive T-cell responses play pivotal roles in both protective and pathological immune responses in numerous diseases. In this review, we explore the implications of these antigen-driven T-cell responses, with a particular focus on CD8+ T cells, using infection, neurodegeneration, and cancer as examples. We also summarize recent technological advances that facilitate high-throughput profiling of antigen-specific and cross-reactive T-cell responses experimentally, as well as computational biology approaches that predict these interactions.

Viruses - a major cause of amyloid deposition in the brain

INTRODUCTION

Clinically, Alzheimer's disease (AD) is a syndrome with a spectrum of various cognitive disorders. There is a complete dissociation between the pathology and the clinical presentation. Therefore, we need a disruptive new approach to be able to prevent and treat AD.

AREAS COVERED

In this review, the authors extensively discuss the evidence why the amyloid beta is not the pathological cause of AD which makes therefore the amyloid hypothesis not sustainable anymore. They review the experimental evidence underlying the role of microbes, especially that of viruses, as a trigger/cause for the production of amyloid beta leading to the establishment of a chronic neuroinflammation as the mediator manifesting decades later by AD as a clinical spectrum. In this context, the emergence and consequences of the infection/antimicrobial protection hypothesis are described. The epidemiological and clinical data supporting this hypothesis are also analyzed.

EXPERT OPINION

For decades, we have known that viruses are involved in the pathogenesis of AD. This discovery was ignored and discarded for a long time. Now we should accept this fact, which is not a hypothesis anymore, and stimulate the research community to come up with new ideas, new treatments, and new concepts.

Untreated if unrecognized: A cognitive profile of sustained subjective executive dysfunctions in COVID-19

& STATEMENT OF IMPACTSARS-COV-2 infection can result in acute and long-lasting cognitive complaints, causing ongoing impairments in daily life which poses a challenge to society. Consequently, the evaluation and characterization of cognitive complaints, specifically in the domain of executive functions (EFs) affecting daily life, is imperative in formulating an effective neuropsychological response.In total 442 participants aged 18-65+ years from the Netherlands, Germany, Mexico, and Spain were included in an online questionnaire. Among others, the questionnaire consisted of demographics, the Behavior Rating Inventory of Executive Functioning for Adults (BRIEF-A), measures of subjective disease progression severity and experienced subjective impairment in daily activities. To assess whether daily life activities are affected by EF impairments, the main BRIEF-A composite score (GEC) was analyzed. To determine whether disease-related COVID-19 factors predict EFs complaints in daily life, a stepwise regression analysis was performed with i) experienced disease severity, ii) time since disease, and iii) health risk factor as predictors.The study revealed noteworthy differences in the occurrence of EFs problems in daily life between both groups, as indicated by the GEC, which exhibited a medium effect size even 6 months post-COVID-19 diagnosis even in mild disease progression. The scores of the BRIEF-A subscales follow a domain-specific profile, and includes clinically relevant impairments in: Working memory, Plan/Organize, Task Monitor, Shift, which are affected by the experienced severity of the disease. This cognitive profile has important implications for targeted cognitive training in rehabilitation and has the potential for an applicability to other viruses as well.

Signalling cognition: the gut microbiota and hypothalamic-pituitary-adrenal axis

Cognitive function in humans depends on the complex and interplay between multiple body systems, including the hypothalamic-pituitary-adrenal (HPA) axis. The gut microbiota, which vastly outnumbers human cells and has a genetic potential that exceeds that of the human genome, plays a crucial role in this interplay. The microbiota-gut-brain (MGB) axis is a bidirectional signalling pathway that operates through neural, endocrine, immune, and metabolic pathways. One of the major neuroendocrine systems responding to stress is the HPA axis which produces glucocorticoids such as cortisol in humans and corticosterone in rodents. Appropriate concentrations of cortisol are essential for normal neurodevelopment and function, as well as cognitive processes such as learning and memory, and studies have shown that microbes modulate the HPA axis throughout life. Stress can significantly impact the MGB axis via the HPA axis and other pathways. Animal research has advanced our understanding of these mechanisms and pathways, leading to a paradigm shift in conceptual thinking about the influence of the microbiota on human health and disease. Preclinical and human trials are currently underway to determine how these animal models translate to humans. In this review article, we summarize the current knowledge of the relationship between the gut microbiota, HPA axis, and cognition, and provide an overview of the main findings and conclusions in this broad field.

Microglia at the scene of the crime: what their transcriptomics reveal about brain health

PURPOSE OF REVIEW

Microglia, which arise from primitive myeloid precursors that enter the central nervous system (CNS) during early development, are the first responders to any perturbance of homeostasis. Although their activation has become synonymous with neurologic disease, it remains unclear whether microglial responses are the cause of or response to neuropathology. Here, we review new insights in the roles of microglia during CNS health and disease, including preclinical studies that transcriptionally profile microglia to define their functional states.

RECENT FINDINGS

Converging evidence suggests that innate immune activation of microglia is associated with overlapping alterations in their gene expression profiles regardless of the trigger. Thus, recent studies examining neuroprotective microglial responses during infections and aging mirror those observed during chronic neurologic diseases, including neurodegeneration and stroke. Many of these insights derive from studies of microglial transcriptomes and function in preclinical models, some of which have been validated in human samples. During immune activation, microglia dismantle their homeostatic functions and transition into subsets capable of antigen presentation, phagocytosis of debris, and management of lipid homeostasis. These subsets can be identified during both normal and aberrant microglial responses, the latter of which may persist long-term. The loss of neuroprotective microglia, which maintain a variety of essential CNS functions, may therefore, in part, underlie the development of neurodegenerative diseases.

SUMMARY

Microglia exhibit a high level of plasticity, transforming into numerous subsets as they respond to innate immune triggers. Chronic loss of microglial homeostatic functions may underlie the development of diseases with pathological forgetting.

Cognitive impairment in long-COVID and its association with persistent dysregulation in inflammatory markers

Objective

To analyze the potential impact of sociodemographic, clinical and biological factors on the long-term cognitive outcome of patients who survived moderate and severe forms of COVID-19.

Methods

We assessed 710 adult participants (Mean age = 55 ± 14; 48.3% were female) 6 to 11 months after hospital discharge with a complete cognitive battery, as well as a psychiatric, clinical and laboratory evaluation. A large set of inferential statistical methods was used to predict potential variables associated with any long-term cognitive impairment, with a focus on a panel of 28 cytokines and other blood inflammatory and disease severity markers.

Results

Concerning the subjective assessment of cognitive performance, 36.1% reported a slightly poorer overall cognitive performance, and 14.6% reported being severely impacted, compared to their pre-COVID-19 status. Multivariate analysis found sex, age, ethnicity, education, comorbidity, frailty and physical activity associated with general cognition. A bivariate analysis found that G-CSF, IFN-alfa2, IL13, IL15, IL1.RA, EL1.alfa, IL45, IL5, IL6, IL7, TNF-Beta, VEGF, Follow-up C-Reactive Protein, and Follow-up D-Dimer were significantly (p<.05) associated with general cognition. However, a LASSO regression that included all follow-up variables, inflammatory markers and cytokines did not support these findings.

Conclusion

Though we identified several sociodemographic characteristics that might protect against cognitive impairment following SARS-CoV-2 infection, our data do not support a prominent role for clinical status (both during acute and long-stage of COVID-19) or inflammatory background (also during acute and long-stage of COVID-19) to explain the cognitive deficits that can follow COVID-19 infection.

Targeting the microbiota-mitochondria crosstalk in neurodegeneration with senotherapeutics

Neurodegenerative diseases are a group of age-related disorders characterized by a chronic and progressive loss of function and/or structure of synapses, neurons, and glial cells. The etiopathogenesis of neurodegenerative diseases is characterized by a complex network of intricately intertwined pathophysiological processes that are still not fully understood. Safe and effective disease-modifying treatments are urgently needed, but still not available. Accumulating evidence suggests that gastrointestinal dyshomeostasis and microbial dysbiosis might play an important role in neurodegeneration by acting as either primary or secondary pathophysiological factors. The research on the role of microbiota in neurodegeneration is in its early phase; however, accumulating evidence suggests that dysbiosis might promote neurodegenerative diseases by disrupting mitochondrial function and inducing mitochondrial dysfunction-associated senescence (MiDAS), possibly due to bidirectional crosstalk based on the common evolutionary origin of mitochondria and bacteria. Cellular senescence is an onco-supressive homeostatic mechanism that results in an irreversible cell cycle arrest upon exposure to noxious stimuli. Senescent cells resist apoptosis via senescent cell anti-apoptotic pathways (SCAPs) and transition into a state known as senescence-associated secretory phenotype (SASP) that generates a cytotoxic proinflammatory microenvironment. Cellular senescence results in the adoption of a detrimental vicious cycle driven by dysbiosis, mitochondrial dysfunction, inflammation, and oxidative stress - a pathophysiological positive feedback loop that results in neuroinflammation and neurodegeneration. Detrimental effects of MiDAS might be prevented and abolished by mitochondria-targeted senotherapeutics, a group of drugs specifically designed to alleviate senescence by inhibiting SCAPs (senolytics), or inhibiting SASP (senomorphics).

Cognitive function in recovered COVID-19 Lebanese patients with schizophrenia

INTRODUCTION

It remains unclear whether COVID-19 which is an infectious disease caused by the SARS-CoV-2 virus is associated with the deterioration of cognitive function among patients with schizophrenia. This study aimed to evaluate changes in cognitive function before and after COVID-19 and associated factors among patients with schizophrenia at the Psychiatric Hospital of the Cross (HPC).

METHODS

A prospective cohort study was conducted among 95 patients with schizophrenia followed from mid-2019 until June 2021 at the Psychiatric Hospital of the Cross (HPC). This cohort was divided into a group diagnosed with COVID-19 (n = 71) and another not diagnosed with COVID-19 (n = 24). The questionnaire included the Brief Assessment of Cognition in Schizophrenia (BACS), Positive and Negative Syndrome Scale (PANSS), Calgary Depression Scale for Schizophrenia (CDSS), and Activities of Daily Living (ADL).

RESULTS

The repeated-measures ANOVA showed no significant effect of time and the interaction between time and being diagnosed or not with COVID-19 on cognition. However, being diagnosed or not with COVID-19 had a significant effect on global cognitive function (p = 0.046), verbal memory (p = 0.046), and working memory (p = 0.047). The interaction between being diagnosed with COVID-19 and cognitive impairment at baseline was significantly associated with a higher cognitive deficit (Beta = 0.81; p = 0.005). Clinical symptoms, autonomy, and depression were not associated with the cognition (p > 0.05 for all).

CONCLUSION

COVID-19 disease affected global cognition and memory: patients diagnosed with COVID-19 had more deficits in these domains than those without COVID-19. Further studies are necessary to clarify the variation of cognitive function among schizophrenic patients with COVID-19.

COVID-19 Patients with Early Gastrointestinal Symptoms Show Persistent Deficits in Specific Attention Subdomains

Previous studies have shown that COVID-19 inpatients exhibited significant attentional deficits on the day of discharge. However, the presence of gastrointestinal symptoms (GIS) has not been evaluated. Here, we aimed to verify: (1) whether COVID-19 patients with GIS exhibited specific attention deficits; (2) which attention subdomain deficits discriminated patients with GIS and without gastrointestinal symptoms (NGIS) from healthy controls. On admission, the presence of GIS was recorded. Seventy-four physically functional COVID-19 inpatients at discharge and sixty-eight controls underwent a Go/No-go computerized visual attentional test (CVAT). A Multivariate Analysis of Covariance (MANCOVA) was performed to examine group differences in attentional performance. To discriminate which attention subdomain deficits discriminated GIS and NGIS COVID-19 patients from healthy controls, a discriminant analysis was applied using the CVAT variables. The MANCOVA showed a significant overall effect of COVID-19 with GIS on attention performance. The discriminant analysis indicated that the GIS group could be differentiated from the controls by variability of reaction time and omissions errors. The NGIS group could be differentiated from controls by reaction time. Late attention deficits in COVID-19 patients with GIS may reflect a primary problem in the sustained and focused attention subsystems, whereas in NGIS patients the attention problems are related to the intrinsic-alertness subsystem.

COVID-19 and Alzheimer's Disease: What Is the Connection?

Wang et al. found that elderly COVID-19 patients were at risk of AD. The following facts suggest a possible explanation: reactivation of herpes simplex virus type 1 (HSV1) and other herpesviruses can occur in SARS-CoV-2 patients; in cell cultures, HSV1 infection causes occurrence of many AD-like features, as does reactivation of latent HSV1 after addition of certain infectious agents; recurrent experimental reactivation of HSV1-infected mice leads to formation of the main features of AD brains, and to cognitive decline. These suggest that COVID-19 results in repeated reactivation of HSV1 in brain, with subsequent accumulation of damage and eventual development of AD.

Subjective and Objective Cognitive Impairments in Non-Hospitalized Persons 9 Months after SARS-CoV-2 Infection

Studies on cognitive problems of persons with mild COVID-19 courses are still lacking. This study aimed to determine the frequency and associated factors of subjective and objective cognitive problems after COVID-19 in non-hospitalized persons. Study participants were examined at the University Hospital of Augsburg from 04/11/2020 to 26/05/2021. The Wechsler Adult Intelligence Scale (WAIS) IV digit span, Stroop Color and Word Test (SCWT), Regensburger verbal fluency test (RWT) and, subjective ratings of memory and concentration were applied. Of the 372 participants (mean age 46.8 ± 15.2 years, 54.3% women, median time after infection 9.1 months), 24.9% reported concentration and 21.9% memory problems. Overall, 55.6% of the participants had at least a mild negative alteration in any cognitive test. The strongest impairments were found regarding memory functions (41.1% mild alterations, 6.2% distinct impairments) and verbal fluency (12.4% mild alterations, 5.4% distinct impairments). SCWT showed negative alterations in no more than 3.0% of the participants. Level of school education, age, and depressiveness emerged as significantly related to the cognitive tests. The number of complaints and depressiveness were significantly associated with subjective memory and concentration problems. It is important to identify mild cognitive impairment in non-hospitalized COVID-19 patients early to offer them effective interventions.

Infections, Vaccinations, and Risk of Alzheimer's Disease (AD)/Dementia: Probable Involvement of Reactivated Herpes Simplex Virus Type 1

Infections are associated with cognitive decline and increased risk of AD/dementia (Sochocka M, Zwolinska K, Leszek J. Curr Neuropharmacol 15:996-1009, 2017; Ou YN, Zhu JX, Hou XH, Shen XN, Xu W, Dong Q, et al. J Alzheimers Dis 75:299-309, 2020; Sipilä PN, Heikkilä N, Lindbohm JV, Hakulinen C, Vahtera J, Elovainio M, et al. Lancet Infect Dis 21:1557-1567, 2021; Damiano RF, Guedes BF, de Rocca CC, de Padua Serafim A, Castro LHM, Munhoz CD, et al. Eur Arch Psychiatry Clin Neurosci 272:139-154, 2022), and some studies have shown that vaccinations, such as BCG, against a variety of infections decrease the risk. Several reports have described an association of varicella zoster virus (VZV) with AD, and in an epidemiological study, we found that shingles, a disease caused by VZV, conferred a small increased AD/dementia risk, while vaccination against the disease led to a greatly decreased risk - subsequently confirmed by others (Lophatananon A, Mekli K, Cant R, Burns A, Dobson C, Itzhaki R, Muir K, BMJ Open 11:e045871, 2021a; Lehrer S, Rheinstein PH. In Vivo 35:3271-3275, 2021; Scherrer JF, Salas J, Wiemken TL, Hoft DF, Jacobs C, Morley JE. PLoS One 16:e0257405, 2021).

A Network Perspective on Neuropsychiatric and Cognitive Symptoms of the Post-COVID Syndrome

Many patients that were infected with SARS-CoV-2 experience cognitive and affective symptoms weeks and months after their acute COVID-19 disease, even when acute symptoms were mild to moderate. For these patients, purely neurological explanations are struggling to explain the development and maintenance of the great variety of neuropsychiatric and cognitive symptoms occurring after COVID-19. We provide a psychological perspective based on the network theory of mental disorders as an added explanation that does not displace neurological mechanism but rather complements them. We suggest viewing the SARS-CoV-2 infection as a trigger that first activates nodes in a causally connected network of neuropsychiatric and cognitive symptoms. In the following, activation will spread throughout the network that will get in a self-sustaining stable and dysfunctional state manifesting in ongoing symptoms known as post-COVID-19 syndrome. The network perspective allows to generalize explanations for persistent neuropsychiatric and cognitive symptoms to patients that experienced mild or moderate acute courses of COVID-19, but also to similar phenomena following other viral infections. In addition, it could explain why some symptoms did not occur during acute COVID-19, but develop weeks or months after it. This network perspective shifts the focus from viewing persistent symptoms as a continuation of COVID-19 to acknowledging it as a complex syndrome that indeed originates from the disease but fully unfolds after it (post-COVID). To test the presented network perspective, we will need extensive cross-sectional as well as longitudinal data on cognitive and neuropsychiatric symptoms in post-COVID patients.

Potential Involvement of Varicella Zoster Virus in Alzheimer's Disease via Reactivation of Quiescent Herpes Simplex Virus Type 1

BACKGROUND

Varicella zoster virus (VZV) has been implicated in Alzheimer's disease (AD), and vaccination against shingles, caused by VZV, has been found to decrease the risk of AD/dementia. VZV might reside latently in brain, and on reactivation might cause direct damage leading to AD, as proposed for herpes simplex virus type 1 (HSV-1), a virus strongly implicated in AD. Alternatively, shingles could induce neuroinflammation and thence, reactivation of HSV-1 in brain.

OBJECTIVE

To investigate these possibilities by comparing the effects of VZV and HSV-1 infection of cultured cells, and the action of VZV infection on cells quiescently infected with HSV-1.

METHODS

We infected human-induced neural stem cell (hiNSC) cultures with HSV-1 and/or VZV and sought the presence of AD-related phenotypes such as amyloid-β (Aβ) and P-tau accumulation, gliosis, and neuroinflammation.

RESULTS

Cells infected with VZV did not show the main AD characteristics, Aβ and P-tau accumulation, which HSV-1 does cause, but did show gliosis and increased levels of pro-inflammatory cytokines, suggesting that VZV's action relating to AD/dementia is indirect. Strikingly, we found that VZV infection of cells quiescently infected with HSV-1 causes reactivation of HSV-1 and consequent AD-like changes, including Aβ and P-tau accumulation.

CONCLUSION

Our results are consistent with the suggestion that shingles causes reactivation of HSV1 in brain and with the protective effects against AD of various vaccines, as well as the decrease in herpes labialis reported after certain types of vaccination. They support an indirect role for VZV in AD/dementia via reactivation of HSV-1 in brain.

Mild Cognitive Disorder in Post-COVID-19 Syndrome: A Retrospective Cohort Study of 67,000 Primary Care Post-COVID Patients

Background:

Little is known about the impact of COVID-19 on mild cognitive disorder.

Objective:

The aim of this retrospective cohort study was to investigate whether COVID-19 diagnosis is associated with subsequent mild cognitive disorder (MCD) compared to acute upper respiratory infections (AURI).

Methods:

This retrospective cohort study used data from the Disease Analyzer database (IQVIA) and included 67,046 patients with first-time symptomatic or asymptomatic COVID-19 diagnoses in 1,172 general practices in Germany between March 2020 and September 2021. Diagnoses were based on ICD-10 codes. Patients diagnosed with AURI were matched to 67,046 patients with COVID-19 using propensity scores based on sex, age, index month, and comorbidities. The index date was the diagnosis date for either COVID-19 or AURI. Associations between the COVID-19 and MCD were studied using conditional Poisson regression models.

Results:

The incidence of MCD was 7.6 cases per 1,000 person-years in the COVID-19 group and 5.1 cases per 1,000 person-years in the AURI group (IRR = 1.49, 95% CI = 1.22–1.82). The incidence rate ratio decreased strongly with increasing age from 10.08 (95% CI = 4.00–24.42) in the age group≤50 to 1.03 (95% CI = 0.81–1.31) in the age group > 70. In addition, the association between COVID-19 and MCD was significant in women (IRR: 1.70, 95% CI: 1.34–2.16) but not in men (IRR: 1.08, 95% CI: 0.75–1.56).

Conclusion

The incidence of MCD was low but significantly higher in COVID-19 than in AURI patients, especially among younger patients. If a cognitive disorder is suspected, referral to a specialist is recommended.

NeuroCOVID-19: a critical review

BACKGROUND

The COVID-19 pandemic has challenged neurologists since its early days. Neurology consultation services were then overloaded by emergency department and intensive-care patients with acute neurological syndromes. These complications are better explained today, but the growing number of patients with reported longstanding neurological symptoms constitute an emerging, complex, and still poorly understood phenomenon.

OBJECTIVE

This review summarizes data on relevant neurological manifestations of acute SARS-CoV-2 infection and lasting post-infectious disease, also known as Long COVID. The complex history of Long COVID is examined to illustrate the upsides and challenges imposed by the active participation of patient communities in the production of medical knowledge.

METHODS

Narrative review.

RESULTS

Infection with the severe acute respiratory syndrome coronavirus 2 is associated with encephalopathy/delirium, cerebrovascular disease, headache, and peripheral nervous system involvement. Long COVID is a living concept jointly defined by patient communities, physicians and scientists, including neurologists.

CONCLUSION

Co-production of Long COVID knowledge between scientists and patients has initiated an era of patient-led research and evidence-based activism that acts as a two-edged sword - putting patient's suffering in the spotlight, but with a tradeoff in methodological consistency.

Update of the Potential Treatments for Psychiatric and Neuropsychiatric Symptoms in the Context of the Post-COVID-19 Condition: Still a Lot of Suffering and Many More Things to Learn

Background: The World Health Organization (WHO) has defined a post-COVID-19 condition. Some of these symptoms can be categorized as psychiatric long COVID-19 if they appeared in the aftermath of COVID-19, including depression, anxiety, post-traumatic stress disorder, somatic symptoms disorders such as hyperventilation syndrome, fatigue, cognitive and sleep disorders. Psychiatric and neuropsychiatric post-COVID-19 present mental health specialists with difficult challenges because of its complexity and the multiple ways in which it integrates into a singular somatic context. Methods: We conducted a systematic research paradigm from SARS-CoV-2 using LitCOVID and Web of Science to search management strategies and potential treatments for psychiatric post-COVID-19 symptoms. Results: Management strategies must be based on a multidisciplinary approach to promote the global evaluation of psychiatric and physical symptoms, systematic detection and prevention. Selective serotonin reuptake inhibitors appear to be the best choice to treat post-COVID-19 depression and anxiety disorders, and tofisopam could be helpful for anxiety. Cognitive behavioral therapy techniques adjusted to post-COVID-19 fatigue, functional remediation, extracorporeal apheresis, transcutaneous auricular vagus nerve stimulation, monoclonal antibodies, flavonoids, oxytocin or L-carnitine all represent hypothetical therapeutic avenues that remain to be evaluated in clinical trials. Conclusions: Psychiatric and neuropsychiatric post-COVID-19 symptoms occur frequently and are debilitating. Attention should be paid to this condition and studies undertaken to specify the effective treatments.

Cognitive Trajectories Following Acute Infection in Older Patients With and Without Cognitive Impairment: An 1-Year Follow-Up Study

Introduction: Dementia is a known risk factor for both delirium and acute systemic infections which may also play a significant role in promoting or accelerating neurodegenerative disease. Infections are both the main causes of hospitalization of dementia patients and can be a major precipitant of delirium but currently it is not possible to predict the risk of cognitive decline in older patients exposed to acute infection. Objectives: We aimed to determine the level of cognitive change at 1-year follow up in individuals with different patterns of cognitive function (dementia, delirium, delirium superimposed on dementia) at the time of their hospitalization due to a systemic infection and to correlate these cognitive patterns with clinical status variables. Methods: We recruited 53 hospitalized geriatric patients with a systemic infection, and we collected 12-months follow up data for 34 patients. These patients were classified in four groups: no cognitive impairment (controls-C), delirium only (D), dementia only (Dem), and delirium superimposed to dementia (DD). Cognitive performance was measured by change in score on the Montreal Cognitive Assessment (MoCA) and delirium was identified using Confusion Assessment Measure (CAM). We examined performance on the MoCA in the first year after hospitalization, controlling for demographic characteristics, coexisting medical conditions, and type of infection. Results: For the 34 patients to whom follow-up data was available, delirium presence in individuals with prior dementia (DD group) was associated with a negative mean change score of 3-point (p < 0.02) at 1 year follow up, whereas dementia patients without delirium had a mean change score of 1.5-point lower at 12-months (p = 0.04), when comparing follow-up and baseline MoCA scores. Cognitively healthy patients did not significantly decrease their MoCA score at follow-up (p = 0.15). MoCA and NPI scores during hospitalization were significantly correlated with the level of cognitive decline in the four groups (r = 0.658, p < 0.01 and r = 0.439, p = 0.02, respectively). Conclusions: Premorbid dementia and delirium superimposed on dementia during hospitalization in older patients with acute infections predict cognitive decline at 1 year following admission. Taken together, our findings suggest a pathophysiological interaction between neurodegenerative changes, acute infection, and delirium.

Dynamic Changes in Central and Peripheral Neuro-Injury vs. Neuroprotective Serum Markers in COVID-19 Are Modulated by Different Types of Anti-Viral Treatments but Do Not Affect the Incidence of Late and Early Strokes

The balance between neurodegeneration, neuroinflammation, neuroprotection, and COVID-19-directed therapy may underly the heterogeneity of SARS-CoV-2's neurological outcomes. A total of 105 patients hospitalized with a diagnosis of COVID-19 had serum collected over a 6 month period to assess neuroinflammatory (MIF, CCL23, MCP-1), neuro-injury (NFL, NCAM-1), neurodegenerative (KLK6, τ, phospho τ, amyloids, TDP43, YKL40), and neuroprotective (clusterin, fetuin, TREM-2) proteins. These were compared to markers of nonspecific inflammatory responses (IL-6, D-dimer, CRP) and of the overall viral burden (spike protein). Data regarding treatment (steroids, convalescent plasma, remdasavir), pre-existing conditions, and incidences of strokes were collected. Amyloid β42, TDP43, NF-L, and KLK6 serum levels declined 2-3 days post-admission, yet recovered to admission baseline levels by 7 days. YKL-40 and NCAM-1 levels remained elevated over time, with clusters of differential responses identified among TREM-2, TDP43, and YKL40. Fetuin was elevated after the onset of COVID-19 while TREM-2 initially declined before significantly increasing over time. MIF serum level was increased 3-7 days after admission. Ferritin correlated with TDP-43 and KLK6. No treatment with remdesivir coincided with elevations in Amyloid-β40. A lack of convalescent plasma resulted in increased NCAM-1 and total tau, and steroidal treatments did not significantly affect any markers. A total of 11 incidences of stroke were registered up to six months after initial admission for COVID-19. Elevated D-dimer, platelet counts, IL-6, and leukopenia were observed. Variable MIF serum levels differentiated patients with CVA from those who did not have a stroke during the acute phase of COVID-19. This study demonstrated concomitant and opposite changes in neurodegenerative and neuroprotective markers persisting well into recovery.

ADAR Editing in Viruses: An Evolutionary Force to Reckon with

Adenosine Deaminases that Act on RNA (ADARs) are RNA editing enzymes that play a dynamic and nuanced role in regulating transcriptome and proteome diversity. This editing can be highly selective, affecting a specific site within a transcript, or nonselective, resulting in hyperediting. ADAR editing is important for regulating neural functions and autoimmunity, and has a key role in the innate immune response to viral infections, where editing can have a range of pro- or antiviral effects and can contribute to viral evolution. Here we examine the role of ADAR editing across a broad range of viral groups. We propose that the effect of ADAR editing on viral replication, whether pro- or antiviral, is better viewed as an axis rather than a binary, and that the specific position of a given virus on this axis is highly dependent on virus- and host-specific factors, and can change over the course of infection. However, more research needs to be devoted to understanding these dynamic factors and how they affect virus-ADAR interactions and viral evolution. Another area that warrants significant attention is the effect of virus-ADAR interactions on host-ADAR interactions, particularly in light of the crucial role of ADAR in regulating neural functions. Answering these questions will be essential to developing our understanding of the relationship between ADAR editing and viral infection. In turn, this will further our understanding of the effects of viruses such as SARS-CoV-2, as well as many others, and thereby influence our approach to treating these deadly diseases.