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IntroductionCoronavirus disease 2019 (COVID-19) has caused >3.5 million deaths worldwide and affected >160 million people. At least twice as many have been infected but remained asymptomatic or minimally symptomatic. COVID-19 includes central nervous system manifestations mediated by inflammation and cerebrovascular, anoxic, and/or viral neurotoxicity mechanisms. More than one third of patients with COVID-19 develop neurologic problems during the acute phase of the illness, including loss of sense of smell or taste, seizures, and stroke. Damage or functional changes to the brain may result in chronic sequelae. The risk of incident cognitive and neuropsychiatric complications appears independent from the severity of the original pulmonary illness. It behooves the scientific and medical community to attempt to understand the molecular and/or systemic factors linking COVID-19 to neurologic illness, both short and long term.MethodsThis article describes what is known so far in terms of links among COVID-19, the brain, neurological symptoms, and Alzheimer's disease (AD) and related dementias. We focus on risk factors and possible molecular, inflammatory, and viral mechanisms underlying neurological injury. We also provide a comprehensive description of the Alzheimer's Association Consortium on Chronic Neuropsychiatric Sequelae of SARS-CoV-2 infection (CNS SC2) harmonized methodology to address these questions using a worldwide network of researchers and institutions.ResultsSuccessful harmonization of designs and methods was achieved through a consensus process initially fragmented by specific interest groups (epidemiology, clinical assessments, cognitive evaluation, biomarkers, and neuroimaging). Conclusions from subcommittees were presented to the whole group and discussed extensively. Presently data collection is ongoing at 19 sites in 12 countries representing Asia, Africa, the Americas, and Europe.DiscussionThe Alzheimer's Association Global Consortium harmonized methodology is proposed as a model to study long-term neurocognitive sequelae of SARS-CoV-2 infection.Key pointsThe following review describes what is known so far in terms of molecular and epidemiological links among COVID-19, the brain, neurological symptoms, and AD and related dementias (ADRD)The primary objective of this large-scale collaboration is to clarify the pathogenesis of ADRD and to advance our understanding of the impact of a neurotropic virus on the long-term risk of cognitive decline and other CNS sequelae. No available evidence supports the notion that cognitive impairment after SARS-CoV-2 infection is a form of dementia (ADRD or otherwise). The longitudinal methodologies espoused by the consortium are intended to provide data to answer this question as clearly as possible controlling for possible confounders. Our specific hypothesis is that SARS-CoV-2 triggers ADRD-like pathology following the extended olfactory cortical network (EOCN) in older individuals with specific genetic susceptibility.The proposed harmonization strategies and flexible study designs offer the possibility to include large samples of under-represented racial and ethnic groups, creating a rich set of harmonized cohorts for future studies of the pathophysiology, determinants, long-term consequences, and trends in cognitive aging, ADRD, and vascular disease.We provide a framework for current and future studies to be carried out within the Consortium. and offers a "green paper" to the research community with a very broad, global base of support, on tools suitable for low- and middle-income countries aimed to compare and combine future longitudinal data on the topic.The Consortium proposes a combination of design and statistical methods as a means of approaching causal inference of the COVID-19 neuropsychiatric sequelae. We expect that deep phenotyping of neuropsychiatric sequelae may provide a series of candidate syndromes with phenomenological and biological characterization that can be further explored. By generating high-quality harmonized data across sites we aim to capture both descriptive and, where possible, causal associations.

Background: COVID‐19 has affected more than 380 million people. Infections may result in long term sequelae, including neuropsychiatric symptoms. In older adults COVID‐19 sequelae resemble early Alzheimer's disease, and may share risk factors and blood biomarkers with it. The Alzheimer's Association Consortium on Chronic Neuropsychiatric Sequelae of SARS‐CoV‐2 infection (CNS SC2) established harmonized definitions, ascertainment and assessment methodologies to evaluate and longitudinally follow up cohorts of older adults with exposure to COVID‐19. We present one year data in a prospective cohort from Argentina. Method: Participants (n = 766) are older adults (≥60 years) recruited from the provincial health registry containing all SARS‐CoV‐2 testing data. We randomly invite older adults stratified by PCR COVID‐19 testing status regardless of symptom severity, between 3 and 6 months after recovery. Assessment includes interview with the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) and Clinical Dementia Rating scale (CDR); neurocognitive assessment; emotional reactivity scale; and neurological assessment including semiquantitative olfactory function test, motor function, coordination and gait. Result: We assessed 88.4% infected participants and 11.6 % controls. Education is 10.36 ± 5.6 years and age is 66.9 ± 6.14 years. Level of care during COVID‐19 is described in Figure 1. Normalized cognitive Z‐scores categorize the cohort in 3 groups with decreased performance compared to normal cognition: memory only impairment (Single‐domain,11.7%); impairment in attention+executive function without memory impairment (Two‐domain, 8.3%); and multiple domain impairment (Multiple domain,11.6%). Logistic regression showed that severity of anosmia, but not clinical status, significantly predicts cognitive impairment. No controls had olfactory dysfunction. Cognitive impairment is defined as Z‐scores below (‐ 2) (Table 1). Clinical assessment with SCAN revealed functional memory impairment in two thirds of infected patients (CDR ≥ 1), which was severe in half of them. Phone‐based follow up at 1 year revealed high adherence (4 participants declined). Five were deceased at follow up. Rates of re‐infection (between 10 and 23%) were not affected by the vaccination schedule (Table 2). Conclusion: The longitudinal cohort had very high adherence. Persistent cognitive and functional impairment after SARS‐CoV‐2 infection is predicted by persistent anosmia but not by the severity of the initial COVID‐19 disease. [ABSTRACT FROM AUTHOR]

Background: The long term sequelae of COVID‐19 in older adults are only beginning to be clarified, and its predictors and underlying molecular mechanisms may shed light on the relationship between viral infections and Alzheimer's disease and related dementia. Method: A prospective cohort of 874 older adult Amerindians from Argentina with COVID‐19 illness confirmed by PCR of nasal swabs as well as controls, was established during the first year of the COVID‐19 pandemic. We obtained data on the severity of the acute illness, as well as extensive neuropsychiatric and cognitive assessments, neurological exams (including quantitative hyposmia/anosmia), plasma for biomarkers and preliminary brain MRI images using the ADNI‐3 protoco (n = 300)l,and whole genome sequencing (n = 300). Isolates from SARS‐CoV‐2 were obtained by the provincial Direction of Epidemiology and sequenced by the national Ministry of Health. Variants of interest/concern were allocated to each case on the basis of the prevalent community isolate at the time of confirmed positive PCR. A deep learning strategy was used to identify predictive factors of cognitive and clinical outcomes. Result: Four distinctive cognitive profiles were identified. Greater cognitive impairment was associated with older age (p = E−9), worse acute COVID‐19 illness (p = 0.008), unvaccinated status (p = E−7), and severity of anosmia (p = E−5). SARS‐CoV‐2 variant was associated with severity of acute illness ((p = E−6) but notably not with cognitive impairment. Preliminary analysis of genomic and brain imaging data will be presented. Conclusion: Our data strongly suggest that all SARS‐CoV‐2 variants of interest up to the omicron wave seem equally likely to result in cognitive impairment in older adults, modulated by the severity of the acute illness. [ABSTRACT FROM AUTHOR]

Introduction: Coronavirus disease 2019 (COVID-19) has caused >3.5 million deaths worldwide and affected >160 million people. At least twice as many have been infected but remained asymptomatic or minimally symptomatic. COVID-19 includes central nervous system manifestations mediated by inflammation and cerebrovascular, anoxic, and/or viral neurotoxicity mechanisms. More than one third of patients with COVID-19 develop neurologic problems during the acute phase of the illness, including loss of sense of smell or taste, seizures, and stroke. Damage or functional changes to the brain may result in chronic sequelae. The risk of incident cognitive and neuropsychiatric complications appears independent from the severity of the original pulmonary illness. It behooves the scientific and medical community to attempt to understand the molecular and/or systemic factors linking COVID-19 to neurologic illness, both short and long term., Methods: This article describes what is known so far in terms of links among COVID-19, the brain, neurological symptoms, and Alzheimer's disease (AD) and related dementias. We focus on risk factors and possible molecular, inflammatory, and viral mechanisms underlying neurological injury. We also provide a comprehensive description of the Alzheimer's Association Consortium on Chronic Neuropsychiatric Sequelae of SARS-CoV-2 infection (CNS SC2) harmonized methodology to address these questions using a worldwide network of researchers and institutions., Results: Successful harmonization of designs and methods was achieved through a consensus process initially fragmented by specific interest groups (epidemiology, clinical assessments, cognitive evaluation, biomarkers, and neuroimaging). Conclusions from subcommittees were presented to the whole group and discussed extensively. Presently data collection is ongoing at 19 sites in 12 countries representing Asia, Africa, the Americas, and Europe., Discussion: The Alzheimer's Association Global Consortium harmonized methodology is proposed as a model to study long-term neurocognitive sequelae of SARS-CoV-2 infection., Key Points: The following review describes what is known so far in terms of molecular and epidemiological links among COVID-19, the brain, neurological symptoms, and AD and related dementias (ADRD)The primary objective of this large-scale collaboration is to clarify the pathogenesis of ADRD and to advance our understanding of the impact of a neurotropic virus on the long-term risk of cognitive decline and other CNS sequelae. No available evidence supports the notion that cognitive impairment after SARS-CoV-2 infection is a form of dementia (ADRD or otherwise). The longitudinal methodologies espoused by the consortium are intended to provide data to answer this question as clearly as possible controlling for possible confounders. Our specific hypothesis is that SARS-CoV-2 triggers ADRD-like pathology following the extended olfactory cortical network (EOCN) in older individuals with specific genetic susceptibility.The proposed harmonization strategies and flexible study designs offer the possibility to include large samples of under-represented racial and ethnic groups, creating a rich set of harmonized cohorts for future studies of the pathophysiology, determinants, long-term consequences, and trends in cognitive aging, ADRD, and vascular disease.We provide a framework for current and future studies to be carried out within the Consortium. and offers a "green paper" to the research community with a very broad, global base of support, on tools suitable for low- and middle-income countries aimed to compare and combine future longitudinal data on the topic.The Consortium proposes a combination of design and statistical methods as a means of approaching causal inference of the COVID-19 neuropsychiatric sequelae. We expect that deep phenotyping of neuropsychiatric sequelae may provide a series of candidate syndromes with phenomenological and biological characterization that can be further explored. By generating high-quality harmonized data across sites we aim to capture both descriptive and, where possible, causal associations., Competing Interests: All authors state that they have no relationships/activities/interests to disclose related to the content of this submission. Author disclosures are available in the supporting information., (© 2022 The Authors. Alzheimer's & Dementia: Translational Research & Clinical Interventions published by Wiley Periodicals LLC on behalf of Alzheimer's Association.)