Resilience of Alzheimer's Disease to COVID-19

Relation between Apolipoprotein E in Alzheimer's Disease and SARS-CoV-2 and their Treatment Strategy: A Review

COVID-19, which primarily affects the pulmonary system, turned out to be a global pandemic, whereas the effects on other systems are still unknown. SARS-CoV-2, binds to angiotensinconverting enzyme 2 (ACE2) receptors in the lungs, causing pneumonia-like symptoms. The same ACE receptors are also present in organs other than the lungs. Therefore, there is a need to study the impact of coronavirus on other human body organs. Recently, UK Biobank reports on the genetic risk factor of the virus attack. A double mutation in the apolipoprotein E (APOE4) allele has shown a significant role in COVID-19. The same APOE4 mutation has already been proven to hold a key role in developing early-onset Alzheimer's disease (EOAD). Despite this data, Alzheimer's disease is believed to be a comorbidity of COVID-19. Previous virus attacks on the same viral family, Coronaviridae, produced neurological effects like neurodegeneration, neuronal inflammation, and other central nervous system-related dysfunctions. Since the long-term implications of COVID-19 are unknown, more research into the impact of the virus on the central nervous system is needed. Both COVID-19 and AD share a common genetic factor, so that AD patients may have a greater risk of SARS-CoV-2. Here, in this review, we have briefly discussed the role of APOE4 in the pathogenesis of AD and SARS-CoV-2, along with their treatment strategy, current scenario, and possible future directions.

SARS-CoV-2 susceptibility and COVID-19 illness course and outcome in people with pre-existing neurodegenerative disorders: systematic review with frequentist and Bayesian meta-analyses

BACKGROUND

People with neurodegenerative disease and mild cognitive impairment (MCI) may have an elevated risk of acquiring severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and may be disproportionally affected by coronavirus disease 2019 (COVID-19) once infected.

AIMS

To review all eligible studies and quantify the strength of associations between various pre-existing neurodegenerative disorders and both SARS-CoV-2 susceptibility and COVID-19 illness course and outcome.

METHOD

Pre-registered systematic review with frequentist and Bayesian meta-analyses. Systematic searches were executed in PubMed, Web of Science and preprint servers. The final search date was 9 January 2023. Odds ratios (ORs) were used as measures of effect.

RESULTS

In total, 136 primary studies (total sample size n = 97 643 494), reporting on 268 effect-size estimates, met the inclusion criteria. The odds for a positive SARS-CoV-2 test result were increased for people with pre-existing dementia (OR = 1.83, 95% CI 1.16-2.87), Alzheimer's disease (OR = 2.86, 95% CI 1.44-5.66) and Parkinson's disease (OR = 1.65, 95% CI 1.34-2.04). People with pre-existing dementia were more likely to experience a relatively severe COVID-19 course, once infected (OR = 1.43, 95% CI 1.00-2.03). People with pre-existing dementia or Alzheimer's disease were at increased risk for COVID-19-related hospital admission (pooled OR range: 1.60-3.72). Intensive care unit admission rates were relatively low for people with dementia (OR = 0.54, 95% CI 0.40-0.74). All neurodegenerative disorders, including MCI, were at higher risk for COVID-19-related mortality (pooled OR range: 1.56-2.27).

CONCLUSIONS

Our findings confirm that, in general, people with neurodegenerative disease and MCI are at a disproportionally high risk of contracting COVID-19 and have a poor outcome once infected.

COVID-19 Outcomes in Hospitalized Patients With Neurodegenerative Disease: A Retrospective Cohort Study

Background and Objectives

COVID-19 outcomes in patients with neurodegenerative disorders (NDs) are not well understood, and we hypothesize that there may be increased morbidity and mortality in this group.

Methods

This was a retrospective cohort study performed at 3 hospitals in the Chicagoland area. All patients hospitalized with COVID-19 infection with ND during a 3-month period (March 15, 2020-June 15, 2020) were included and compared with age-matched controls (CL) at 1:1 ratio. Primary outcomes were death, intensive care unit (ICU) admission, and invasive ventilation. Secondary outcomes included presenting COVID-19 symptoms, development of encephalopathy, supplementary oxygen use, discharge disposition, and risk factors for mortality.

Results

The study included 132 patients with neurodegenerative disorders and 132 age-matched CL. Ninety-day mortality (ND 19.7% vs CL 23.5%, p = 0.45) and ICU admission (ND 31.5% vs CL 35.9%, p = 0.43) rates were not significantly different between the 2 groups. Patients with ND had a lower rate of invasive ventilation (ND 11.4% vs CL 23.2%, p = 0.0075) and supplementary oxygen use (ND 83.2% vs CL 95.1%, p = 0.0012). Patients with ND were also more likely to have altered mental status or confusion as their presenting COVID-19 symptom and less likely to present with respiratory symptoms. Patients with ND were discharged to nursing home or hospice at higher rates compared with CL.

Discussion

We found that there was no difference in short-term mortality of patients with ND hospitalized for COVID-19 compared with CL, but they may have higher rates of neurologic complications and disability. Future studies should address long-term outcomes.

COVID-19 related outcomes among individuals with neurodegenerative diseases: a cohort analysis in the UK biobank

Background

An increased susceptibility to COVID-19 has been suggested for individuals with neurodegenerative diseases, but data are scarce from longitudinal studies.

Methods

In this community-based cohort study, we included 96,275 participants of the UK Biobank who had available SARS-CoV-2 test results in Public Health England. Of these, 2617 had a clinical diagnosis of neurodegenerative diseases in the UK Biobank inpatient hospital data before the outbreak of COVID-19 (defined as January 31st, 2020), while the remaining participants constituted the reference group. We then followed both groups from January 31st, 2020 to June 14th, 2021 for ascertainment of COVID-19 outcomes, including any COVID-19, inpatient care for COVID-19, and COVID-19 related death. Logistic regression was applied to estimate the association between neurogenerative disease and risks of COVID-19 outcomes, adjusted for multiple confounders and somatic comorbidities.

Results

We observed an elevated risk of COVID-19 outcomes among individuals with a neurodegenerative disease compared with the reference group, corresponding to a fully adjusted odds ratio of 2.47 (95%CI 2.25–2.71) for any COVID-19, 2.18 (95%CI 1.94–2.45) for inpatient COVID-19, and 3.67 (95%CI 3.11–4.34) for COVID-19 related death. Among individuals with a positive test result for SARS-CoV-2, individuals with neurodegenerative diseases had also a higher risk of COVID-19 related death than others (fully adjusted odds ratio 2.08; 95%CI 1.71–2.53).

Conclusion

Among UK Biobank participants who received at least one test for SARS-CoV-2, a pre-existing diagnosis of neurodegenerative disease was associated with a subsequently increased risk of COVID-19, especially COVID-19 related death.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02536-7.

Dementia wellbeing and COVID-19: Review and expert consensus on current research and knowledge gaps

OBJECTIVES

In response to a commissioned research update on dementia during the COVID-19 pandemic, a UK-based working group, comprising dementia researchers from a range of fields and disciplines, aimed to describe the impact of the pandemic on dementia wellbeing and identify priorities for future research.

METHODS

We supplemented a rapid literature search (including unpublished, non-peer reviewed and ongoing studies/reports) on dementia wellbeing in the context of COVID-19 with expert group members' consensus about future research needs. From this we generated potential research questions the group judged to be relevant that were not covered by the existing literature.

RESULTS

Themes emerged from 141 studies within the six domains of the NHS England COVID-19 Dementia Wellbeing Pathway: Preventing Well, Diagnosing Well, Treating Well, Supporting Well, Living Well and Dying Well. We describe current research findings and knowledge gaps relating to the impact on people affected by dementia (individuals with a diagnosis, their carers and social contacts, health and social care practitioners and volunteers), services, research activities and organisations. Broad themes included the potential benefits and risks of new models of working including remote healthcare, the need for population-representative longitudinal studies to monitor longer-term impacts, and the importance of reporting dementia-related findings within broader health and care studies.

CONCLUSIONS

The COVID-19 pandemic has had a disproportionately negative impact on people affected by dementia. Researchers and funding organisations have responded rapidly to try to understand the impacts. Future research should highlight and resolve outstanding questions to develop evidence-based measures to improve the quality of life of people affected by dementia.

COVID-19 Case Fatality and Alzheimer's Disease

Previous studies have identified dementia as a risk factor for death from coronavirus disease 2019 (COVID-19). However, it is unclear whether Alzheimer's disease (AD) is an independent risk factor for COVID-19 case fatality rate. In a retrospective cohort study, we identified 387,841 COVID-19 patients through TriNetX. After adjusting for demographics and comorbidities, we found that AD patients had higher odds of dying from COVID-19 compared to patients without AD (Odds Ratio: 1.20, 95%confidence interval: 1.09-1.32, p < 0.001). Interestingly, we did not observe increased mortality from COVID-19 among patients with vascular dementia. These data are relevant to the evolving COVID-19 pandemic.

Mental and neurological disorders and risk of COVID-19 susceptibility, illness severity and mortality: A systematic review, meta-analysis and call for action

BACKGROUND

Coronavirus disease 2019 (COVID-19) has evolved into a worldwide pandemic, and has been found to be closely associated with mental and neurological disorders. We aimed to comprehensively quantify the association between mental and neurological disorders, both pre-existing and subsequent, and the risk of susceptibility, severity and mortality of COVID-19.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Web of Science, Embase, PsycINFO, and Cochrane library databases for studies published from the inception up to January 16, 2021 and updated at July 7, 2021. Observational studies including cohort and case-control, cross-sectional studies and case series that reported risk estimates of the association between mental or neurological disorders and COVID-19 susceptibility, illness severity and mortality were included. Two researchers independently extracted data and conducted the quality assessment. Based on I2 heterogeneity, we used a random effects model to calculate pooled odds ratios (OR) and 95% confidence intervals (95% CI). Subgroup analyses and meta-regression analysis were also performed. This study was registered on PROSPERO (registration number: CRD 42021230832).

FINDING

A total of 149 studies (227,351,954 participants, 89,235,737 COVID-19 patients) were included in this analysis, in which 27 reported morbidity (132,727,798), 56 reported illness severity (83,097,968) and 115 reported mortality (88,878,662). Overall, mental and neurological disorders were associated with a significant high risk of infection (pre-existing mental: OR 1·67, 95% CI 1·12-2·49; and pre-existing neurological: 2·05, 1·58-2·67), illness severity (mental: pre-existing, 1·40, 1·25-1·57; sequelae, 4·85, 2·53-9·32; neurological: pre-existing, 1·43, 1·09-1·88; sequelae, 2·17, 1·45-3·24), and mortality (mental: pre-existing, 1·47, 1·26-1·72; neurological: pre-existing, 2·08, 1·61-2·69; sequelae, 2·03, 1·66-2·49) from COVID-19. Subgroup analysis revealed that association with illness severity was stronger among younger COVID-19 patients, and those with subsequent mental disorders, living in low- and middle-income regions. Younger patients with mental and neurological disorders were associated with higher mortality than elders. For type-specific mental disorders, susceptibility to contracting COVID-19 was associated with pre-existing mood disorders, anxiety, and attention-deficit hyperactivity disorder (ADHD); illness severity was associated with both pre-existing and subsequent mood disorders as well as sleep disturbance; and mortality was associated with pre-existing schizophrenia. For neurological disorders, susceptibility was associated with pre-existing dementia; both severity and mortality were associated with subsequent delirium and altered mental status; besides, mortality was associated with pre-existing and subsequent dementia and multiple specific neurological diseases. Heterogeneities were substantial across studies in most analysis.

INTERPRETATION

The findings show an important role of mental and neurological disorders in the context of COVID-19 and provide clues and directions for identifying and protecting vulnerable populations in the pandemic. Early detection and intervention for neurological and mental disorders are urgently needed to control morbidity and mortality induced by the COVID-19 pandemic. However, there was substantial heterogeneity among the included studies, and the results should be interpreted with caution. More studies are needed to explore long-term mental and neurological sequela, as well as the underlying brain mechanisms for the sake of elucidating the causal pathways for these associations.

FUNDING

This study is supported by grants from the National Key Research and Development Program of China, the National Natural Science Foundation of China, Special Research Fund of PKUHSC for Prevention and Control of COVID-19, and the Fundamental Research Funds for the Central Universities.

Dementia and COVID-19, a Bidirectional Liaison: Risk Factors, Biomarkers, and Optimal Health Care

Cognitive impairment following SARS-CoV-2 infection is being increasingly recognized as an acute and possibly also long-term sequela of the disease. Direct viral entry as well as systemic mechanisms such as cytokine storm are thought to contribute to neuroinflammation in these patients. Biomarkers of COVID-19-induced cognitive impairment are currently lacking, but there is some limited evidence that SARS-CoV-2 could preferentially target the frontal lobes, as suggested by behavioral and dysexecutive symptoms, fronto-temporal hypoperfusion on MRI, EEG slowing in frontal regions, and frontal hypometabolism on 18F-FDG-PET. Possible confounders include cognitive impairment due to hypoxia and mechanical ventilation and post-traumatic stress disorder. Conversely, patients already suffering from dementia, as well as their caregivers, have been greatly impacted by the disruption of their care caused by COVID-19. Patients with dementia have experienced worsening of cognitive, behavioral, and psychological symptoms, and the rate of COVID-19-related deaths is disproportionately high among cognitively impaired people. Multiple factors, such as difficulties in remembering and executing safeguarding procedures, age, comorbidities, residing in care homes, and poorer access to hospital standard of care play a role in the increased morbidity and mortality. Non-pharmacological interventions and new technologies have shown a potential for the management of patients with dementia, and for the support of their caregivers.

Can Control Infections Slow Down the Progression of Alzheimer's Disease? Talking About the Role of Infections in Alzheimer's Disease

Alzheimer’s disease as the most common age-related dementia affects more than 40 million people in the world, representing a global public health priority. However, the pathogenesis of Alzheimer’s disease (AD) is complex, and it remains unclear. Over the past decades, all efforts made in the treatments of AD, with targeting the pathogenic amyloid β (Aβ), neurofibrillary tangles, and misfolded tau protein, were failed. Recently, many studies have hinted that infection, and chronic inflammation that caused by infection are crucial risk factors for AD development and progress. In the review, we analyzed the role of infections caused by bacteria, viruses, and other pathogens in the pathogenesis of AD and its animal models, and explored the therapeutic possibility with anti-infections for AD. However, based on the published data, it is still difficult to determine their causal relationship between infection and AD due to contradictory results. We think that the role of infection in the pathogenesis of AD should not be ignored, even though infection does not necessarily cause AD, it may act as an accelerator in AD at least. It is essential to conduct the longitudinal studies and randomized controlled trials in humans, which can determine the role of infection in AD and clarify the links between infection and the pathological features of AD. Finding targeting infection drugs and identifying the time window for applying antibacterial or antiviral intervention may be more promising for future clinical therapeutic strategies in AD.

Emerging COVID-19 Neurological Manifestations: Present Outlook and Potential Neurological Challenges in COVID-19 Pandemic

The unremitting coronavirus disease 2019 (COVID-19) pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) marked a year-long phase of public health adversaries and has severely compromised healthcare globally. Early evidence of COVID-19 noted its impact on the pulmonary and cardiovascular functions, while multiple studies in recent time shed light on its substantial neurological complications, though a comprehensive understanding of the cause(s), the mechanism(s), and their neuropathological outcomes is scarce. In the present review, we conferred evidence of neurological complications in COVID-19 patients and shed light on the SARS-CoV-2 infection routes including the hematogenous, direct/neuronal, lymphatic tissue or cerebrospinal fluid, or infiltration through infected immune cells, while the underlying mechanism of SARS-CoV-2 invasion to the central nervous system (CNS) was also discussed. In an up-to-date manner, we further reviewed the impact of COVID-19 in developing diverse neurologic manifestations associated with CNS, peripheral nervous system (PNS), skeletal muscle, and also pre-existing neurological diseases, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, and myasthenia gravis. Furthermore, we discussed the involvement of key factors including age, sex, comorbidity, and disease severity in exacerbating the neurologic manifestations in COVID-19 patients. An outlook of present therapeutic strategies and state of existing challenges in COVID-19 management was also accessed. Conclusively, the present report provides a comprehensive review of COVID-19-related neurological complications and emphasizes the need for their early clinical management in the ongoing COVID-19 pandemic.

The key role of the level of ACE2 gene expression in SARS-CoV-2 infection

SARS-CoV-2 more readily affects the elderly, especially as they present co-morbidities. In the COVID-19 pathogeny, ACE2 appears to be the key cell receptor for SARS-CoV-2 to infect humans. The level of ACE2 gene expression influences the susceptibility of contracting SARS-CoV-2. In circumstances in which the ACE2 level is low, the incidence of Covid-19 seems to be fewer. Two clinical patterns illustrate this observation, i. e., in infants and in Alzheimer's disease (AD). Very young children and AD patients get little COVID-19, in part probably due to decreased expression of ACE2. The determination of the nasal level of ACE2 gene expression could provide a useful scale to predict the susceptibility to contract the SARS-CoV-2 infection.