Episodic long-term memory in post-infectious SARS-CoV-2 patients

Dissociable effects of mild COVID-19 on short- and long-term memories

Recent studies have highlighted the presence of cognitive deficits following COVID-19 that persist beyond acute infection, regardless of the initial disease severity. Impairments in short- and long-term memory are among the core deficits reported by patients and observed in objective tests of memory performance. We aimed to extend previous studies by examining performance in a task that allows us to directly compare and contrast memories at different timescales. More specifically, we assessed both short- and long-term memories for contextual-spatial associations encoded during a common session and probed at different durations using an equivalent task in non-hospitalized individuals recovering from mild COVID-19 compared to healthy controls. The approach equated all aspects of memory materials and response demands, isolating performance changes resulting only from memory timescales and thus allowing us to quantify the impact of COVID-19 on cognition. In addition to providing measures of accuracy and response times, the task also provided a sensitive continuous readout of the precision of memory representations, specifically by examining the resolution with which spatial locations were retained in memory. The results demonstrated selective impairment of long-term memory performance in individuals recovering from mild COVID-19 infection. Short-term memory performance remained comparable to healthy controls. Specifically, poor precision of long-term memory representations was demonstrated, which improved with days since diagnosis. No such relationship was observed for short-term memory performance. Our findings reveal a specific impairment to the precision of spatial-contextual long-term memory representations in individuals recovering from mild COVID-19 and demonstrate evidence of recovery in long-term memory over time. Further, the experimental design provides a carefully controlled and sensitive framework to assess memory across different durations with the potential to provide more detailed phenotyping of memory deficits associated with COVID-19 in general.

Cognitive domains affected post-COVID-19; a systematic review and meta-analysis

BACKGROUND AND PURPOSE

This review aims to characterize the pattern of post-COVID-19 cognitive impairment, allowing better prediction of impact on daily function to inform clinical management and rehabilitation.

METHODS

A systematic review and meta-analysis of neurocognitive sequelae following COVID-19 was conducted, following PRISMA-S guidelines. Studies were included if they reported domain-specific cognitive assessment in patients with COVID-19 at >4 weeks post-infection. Studies were deemed high-quality if they had >40 participants, utilized healthy controls, had low attrition rates and mitigated for confounders.

RESULTS

Five of the seven primary Diagnostic and Statistical Manual of Mental Disorders (DSM-5) cognitive domains were assessed by enough high-quality studies to facilitate meta-analysis. Medium effect sizes indicating impairment in patients post-COVID-19 versus controls were seen across executive function (standardised mean difference (SMD) -0.45), learning and memory (SMD -0.55), complex attention (SMD -0.54) and language (SMD -0.54), with perceptual motor function appearing to be impacted to a greater degree (SMD -0.70). A narrative synthesis of the 56 low-quality studies also suggested no obvious pattern of impairment.

CONCLUSIONS

This review found moderate impairments across multiple domains of cognition in patients post-COVID-19, with no specific pattern. The reported literature was significantly heterogeneous, with a wide variety of cognitive tasks, small sample sizes and disparate initial disease severities limiting interpretability. The finding of consistent impairment across a range of cognitive tasks suggests broad, as opposed to domain-specific, brain dysfunction. Future studies should utilize a harmonized test battery to facilitate inter-study comparisons, whilst also accounting for the interactions between COVID-19, neurological sequelae and mental health, the interplay between which might explain cognitive impairment.

Assessment of Cognitive and Mood Changes in Older Survivors of COVID-19: A Year's Follow-up

ABSTRACT

The long-term effects of coronavirus disease 2019 (COVID-19) infection are not fully known. In this study, we aimed to evaluate cognitive function and mood changes with 1-year follow-up in the elderly after COVID-19 disease. Ninety COVID-19 survivors and 90 healthy controls were included in the study between April 2022 and 2023. The patients were evaluated at the 1st, 6th, and 12th months for cognition, depression, and sleep quality. Cognitive function is assessed by the Montreal Cognitive Assessment (MoCA), sleep quality by the Pittsburgh Sleep Quality Index, and depression by the Yesavage Geriatric Depression Scale. COVID-19 survivors secured lower scores in certain domains of the MoCA in comparison with the controls at the first and sixth months. However, at the 12th month, no difference was observed in total MoCA ( p = 0.100), Yesavage Geriatric Depression Scale ( p = 0.503), and Pittsburgh Sleep Quality Index ( p = 0.907) between survivors and controls. Older patients who recovered from COVID-19 have lower cognitive function compared with controls up to 12 months. However, cognitive function scores were similar at the end of the first year except for memory scores.

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.

Anosmia predicts memory impairment in post-COVID-19 syndrome: results of a neuropsychological cohort study

Recovered COVID-19 patients frequently suffer of cognitive disorders. Several etiopathogenetic mechanisms have been considered for the brain complications in COVID-19 but results are uncertain. Amongst them, an olfactory route to SARS-CoV-2 brain infection might explain cognitive and memory disturbances in post-COVID-19 patients, given the cooccurrence of anosmia and possible underlying limbic involvement. The aims of the study are to investigate cognition of patients with post-COVID-19 syndrome, and to find clinical factors predicting cognitive and memory impairments. 18 patients with post-COVID-19 syndrome underwent neuropsychological assessment and evaluation of clinical parameters. Stepwise regression analysis was used between clinical parameters as factors and cognitive global scores as dependent variables. Since only anosmia predicted memory performances, repeated measures ANOVA of memory scores was conducted between anosmic and non-anosmic patients. We found lack of association between clinical parameters and cognitive performances. Only anosmia was a good predictor for memory performances, with anosmic subjects showing a temporo-mesial amnesic profile. Our study shows novel findings of causal association between transient anosmia during COVID-19 and memory disorders with temporo-mesial dysfunction, probably sharing a common pathophysiological mechanism, and suggesting a possible SARS-CoV 2 infection of the limbic brain via the olfactory route. In contrast to previous studies, cognitive dysfunctions were not associated with respiratory distress, comorbidity, and depression.

Relationship between Reaction Times and Post-COVID-19 Symptoms Assessed by a Web-Based Visual Detection Task

Long-COVID is a clinical condition in which patients affected by SARS-CoV-2 usually report a wide range of physical and cognitive symptoms from 3 to 6 months after the infection recovery. The aim of the current study was to assess the link between self-reported long-COVID symptoms and reaction times (RTs) in a self-administered Visual Detection Task (VDT) in order to identify the predictor symptoms of the slowing in reaction times to determine attention impairment. In total, 362 participants (age (mean ± S.D.: 38.56 ± 13.14); sex (female-male: 73.76-26.24%)) responded to a web-based self-report questionnaire consisting of four sections: demographics, disease-related characteristics, and medical history questions. The final section consisted of a 23 item 5-point Likert-scale questionnaire related to long-term COVID-19 symptoms. After completing the questionnaire, subjects performed a VDT on a tablet screen to assess reaction times (RTs). An exploratory factorial analysis (EFA) was performed on the 23 long-COVID symptom questions, identifying 4 factors (cognition, behavior, physical condition, presence of anosmia and/or ageusia). The most important predictors of RTs were cognition and physical factors. By dissecting the cognitive and physical factors, learning, visual impairment, and headache were the top predictors of subjects' performance in the VDT. Long-COVID subjects showed higher RTs in the VDT after a considerable time post-disease, suggesting the presence of an attention deficit disorder. Attention impairment due to COVID-19 can be due to the presence of headaches, visual impairments, and the presence of cognitive problems related to the difficulty in learning new activities. The link between the slowing of reaction times and physical and cognitive symptoms post-COVID-19 suggests that attention deficit disorder is caused by a complex interaction between physical and cognitive symptoms. In addition, the study provides evidence that RTs in a VDT represent a reliable measure to detect the presence of long-COVID neurological sequelae.

The association between objective cognitive measures and ecological-functional outcomes in COVID-19

Background

Cognitive dysfunctions, both subjective and detectable at psychometric testing, may follow SARS-CoV-2 infection. However, the ecological-functional relevance of such objective deficits is currently under-investigated. This study thus aimed at investigating the association between objective cognitive measures and both physical and cognitive, ecological-functional outcomes in post-COVID-19.

Methods

Forty-two COVID-19-recovered individuals were administered the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The Functional Independence Measure (FIM) was adopted to assess functional-ecological, motor/physical (FIM-Motor) and cognitive (FIM-Cognitive) outcomes at admission (T0) and discharge (T1).

Results

When predicting both T0/T1 FIM-total and-Motor scores based on MMSE/MoCA scores, premorbid risk for cognitive decline (RCD) and disease-related features, no model yielded a significant fit. However, the MoCA - but not the MMSE significantly predicted T0/T1 FIM-Cognitive scores. The MoCA was significantly related only to T0/T1 FIM-Cognitive Memory items.

Discussion

Cognitive measures are not associated with physical/motor everyday-life outcomes in post-COVID-19 patients. The MoCA may provide an ecological estimate of cognitive functioning in this population.

Psychiatric symptoms subsequent to COVID-19 and their association with clinical features: A retrospective investigation

This study explores the association between psychiatric symptoms following COVID-19 and demographic, disease-related and premorbid clinical confounders. Global cognition, depression, anxiety and PTSD features were assessed in 152 post-COVID-19 patients, subdivided into being at risk for brain disorders or not. In both groups, clinically meaningful depression, anxiety and PTSD symptoms were mildly-to-moderately frequent (4-45%). No demographic or clinical variables predicted psychiatric measures (except for lower age predicting higher anxiety levels). Depression, anxiety and PTSD measures were associated among each other. Hence, depression-, anxiety- and PTSD-spectrum disturbances in COVID-19 survivors are likely to be unassociated with disease-related and premorbid features.

Cognitive phenotyping of post-infectious SARS-CoV-2 patients

Background

SARS-CoV-2 infection entails neuroinvasive, neuroinflammatory, and treatment-related features accounting for cognitive deficits in COVID-19-recovered patients. Although screening for such dysfunctions in this population is considered clinically relevant, contributions to cognitive phenotyping including premorbid and disease-related confounders are scarcely represented. This study thus aimed at describing the cognitive outcome at the function-/domain-level of post-infectious SARS-CoV-2 patients being already at risk (RCD +) or not (RCD −) for cognitive decline.

Methods

Fifty-four COVID-19-recovered individuals were classified as either RCD + or RCD − according to medical records. The Mini-Mental State Examination (MMSE), Addebrooke Cognitive Examination-Revised (ACE-R), Frontal Assessment Battery (FAB), and Attentive Matrices (AM) were administered (N = 54, 34, 28, and 28 patients, respectively).

Results

Prevalence of defective (cutoff = 24.89) MMSE scores was 24.3% in RCD + patients and 5.9% in the RCD − group. ACE-R-total below cutoff scores were less frequent (RCD + : 5.4%; RCD − : 5.9%). Abnormal performances at the FAB an AM were respectively detected in 18.9% and 8.1% of RCD + patients and 0% and 11.8% of the RCD − group. Within the ACE-R subtests, those assessing orientation, attention, and fluency were the most frequently impaired in both groups. Disease-related variables were mostly unassociated with cognitive measures.

Discussion

Both RCD + and RCD − COVID-19-recovered individuals might show cognitive deficits within the dysexecutive-inattentive and amnesic spectrum. Non-instrumental, executive/attentive dysfunctions are predominant in this population and can be detected by both screening and domain-specific psychometric tests—although the latter might be more sensitive in RCD − patients.

Cognitive impairment in people with previous COVID-19 infection: A scoping review

Severe acute respiratory syndrome coronavirus 2 is a worldwide public health issue. Almost 2 years into the pandemic, the persistence of symptoms after the acute phase is a well-recognized phenomenon. We conducted a scoping review to map cognitive domain impairments, their frequency, and associated psycho-affective disorders in people with a previous COVID-19 infection. We searched PubMed/MEDLINE, Scopus, and PsycInfo to identify relevant reports published between December 1, 2019 and February 21, 2022. We followed the PRISMA (Preferred-Reporting-Items-for-Systematic-Reviews-and-Meta-Analyses) extension for scoping review guidelines. Three independent reviewers selected and charted 25 records out of 922. Memory, attention, and executive functions appeared to be the most affected domains. Delayed recall and learning were the most impaired domains of memory. Among the executive functions, abstraction, inhibition, set shifting, and sustained and selective attention were most commonly impaired. Language and visuo-spatial abilities were rarely affected, although this finding might be biased by the scarcity of reports. Neurological and respiratory conditions were often reported in association with cognitive deficits. Results on psycho-affective conditions were inconclusive due to the low frequency of reported data. Admission to an intensive care unit is not related to cognitive deficits. This review highlighted a potential effect of a previous post-COVID-19 infection on a pattern of memory, attention, and executive functions impairments. These findings need to be confirmed on larger cohorts with comprehensive neuropsychological batteries and correlated to neurophysiological and neurobiological substrates.