Long-term neurological outcome after COVID-19 using all SARS-CoV-2 test results and hospitalisations in Denmark with 22-month follow-up

SARS-CoV-2 Infection and Risk of Postacute Psychiatric and Neurologic Diagnoses: A Nationwide Danish Cohort Study

BACKGROUND AND OBJECTIVES

The extent and burden of postacute psychiatric and neurologic manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are not yet fully understood. To evaluate the association between SARS-CoV-2 infection and postacute manifestations of psychiatric and neurologic disorders, we conducted a nationwide cohort study including the entire Danish population aged 12 years or older on March 1, 2020.

METHODS

Individuals were followed up for SARS-CoV-2 infection and diagnosis of subsequent psychiatric and neurologic disorders from March 1, 2020, to January 31, 2023, using the Danish nationwide coronavirus disease 2019 (COVID-19) test surveillance database and the Danish National Patient Registry. The main period of interest was 1-12 months after infection. Incidence rate ratios (IRRs) of new onset of 11 psychiatric and 30 neurologic disorders were calculated by comparing incidence rates of disorders between SARS-CoV-2-positive individuals and individuals without a positive test (nonpositive individuals). Stratified analyses were conducted according to COVID-19 vaccination status, variant period, age, sex, and severity of infection.

RESULTS

Overall, 1,775,639 individuals in the study cohort (n = 3,239,008) were tested SARS-CoV-2 positive during follow-up. SARS-CoV-2-positive individuals compared with nonpositive individuals were at 24% reduced risk of any psychiatric disease (IRR 0.76, 95% CI 0.74-0.78) in the postacute period. The risk of any neurologic disorder was slightly higher among SARS-CoV-2-positive individuals than among those without a positive test (IRR 1.05, 95% CI 1.04-1.07). IRRs for specific disorders varied considerably from a 3.9-fold increased risk of change in sense of smell or taste (IRR 3.91, 95% CI 2.77-5.53) to a 29% reduced risk of dementia (IRR 0.71, 95% CI 0.65-0.78). The severity of infection and vaccination status, more so than age, sex, and variant, were found to significantly influence the stratified IRRs. Compared with nonpositive individuals, hospitalized patients with COVID-19 were at a 2.1-fold (IRR 2.05, 95% CI 1.78-2.37) increased risk of psychiatric disorders and at a 2.4-fold increased risk of neurologic disorders (IRR 2.44, 95% CI 2.29-2.60).

DISCUSSION

Our study does not support previous findings of substantial postacute neurologic and psychiatric morbidities among the general population of SARS-CoV-2-infected individuals, but does corroborate an elevated risk among the most severe cases with COVID-19.

Possible temporal relationship between SARS-CoV-2 infection and anti-NMDA receptor encephalitis: a meta-analysis

The global impact of SARS-CoV-2 infection has raised concerns about secondary diseases beyond acute illness. This review explores the significance and potential underlying mechanisms of how SARS-CoV-2 infection might elicit an immune response targeting N-methyl-D-aspartate (NMDA) receptors, and its implications for autoimmune-driven neuropsychiatric manifestations. We identified 19 published case reports of NMDA receptor encephalitis associated with SARS-CoV-2 infection or vaccination by a systematic literature search. The significance of these reports was limited since it is not clear if a coincidental or causal relationship exists between SARS-CoV-2 infection or vaccination and manifestation of NMDA receptor encephalitis. The included studies were hampered by difficulties in establishing if these patients had pre-existing NMDA receptor antibodies which entered the brain by infection- or vaccination-associated transient blood-brain barrier leakage. In addition, four cases had comorbid ovarian teratoma, which is a known trigger for development of NMDA receptor encephalitis. Considering that billions of people have contracted COVID-19 or have been vaccinated against this virus, the publication of only 19 case reports with a possible link to NMDA receptor encephalitis, indicates that it is rare. In conclusion, these findings do not support the case that SARS-CoV-2 infection or vaccination led to an increase of existing or de novo encephalitis mediated by an autoimmune response targeting NMDA receptor function. Nevertheless, this work underscores the importance of ongoing vigilance in monitoring viral outbreaks and their potential impact on the central nervous system through basic, epidemiological and translational research.

The burden of persistent symptoms after COVID-19 (long COVID): a meta-analysis of controlled studies in children and adults

BACKGROUND

Previous meta-analyses estimating the prevalence of the post-COVID-19 condition (PCC) were confounded by the lack of negative control groups. This may result in an overestimation of the prevalence of those experiencing PCC, as these symptoms are non-specific and common in the general population. In this study, we aimed to compare the burden of persistent symptoms among COVID-19 survivors relative to COVID-19-negative controls.

METHODS

A systematic literature search was conducted using the following databases (PubMed, Web of Science, and Scopus) until July 2023 for comparative studies that examined the prevalence of persistent symptoms in COVID-19 survivors. Given that many of the symptoms among COVID-19 survivors overlap with post-hospitalization syndrome and post-intensive care syndrome, we included studies that compare the prevalence of persistent symptoms in hospitalized COVID-19 patients relative to non-COVID-19 hospitalized patients and in non-hospitalized COVID-19 patients relative to healthy controls that reported outcomes after at least 3 months since infection. The results of the meta-analysis were reported as odds ratios with a 95% confidence interval based on the random effects model.

RESULTS

Twenty articles were included in this study. Our analysis of symptomatology in non-hospitalized COVID-19 patients compared to negative controls revealed that the majority of symptoms examined were not related to COVID-19 infection and appeared equally prevalent in both cohorts. However, non-COVID-19 hospitalized patients had higher odds of occurrence of certain symptoms like anosmia, ageusia, fatigue, dyspnea, and brain fog (P < 0.05). Particularly, anosmia and ageusia showed substantially elevated odds relative to the negative control group at 11.27 and 9.76, respectively, P < 0.05. In contrast, analysis of hospitalized COVID-19 patients compared to those hospitalized for other indications did not demonstrate significantly higher odds for the tested symptoms.

CONCLUSIONS

The persistent symptoms in COVID-19 survivors may result from hospitalization for causes unrelated to COVID-19 and are commonly reported among the general population. Although certain symptoms exhibited higher odds in non-hospitalized COVID-19 patients relative to controls, these symptoms are common post-viral illnesses. Therefore, the persistent symptoms after COVID-19 may not be unique to SARS-CoV-2. Future studies including well-matched control groups when investigating persistent symptoms in COVID-19 survivors are warranted to draw a firm conclusion.

Vaccination prevents IL-1β-mediated cognitive deficits after COVID-19

Up to 25% of SARS-CoV-2 patients exhibit post-acute cognitive sequelae. Although millions of cases of COVID-19-mediated memory dysfunction are accumulating worldwide, the underlying mechanisms and how vaccination lowers risk are unknown. Interleukin-1, a key component of innate immune defense against SARS-CoV-2 infection, is elevated in the hippocampi of COVID-19 patients. Here we show that intranasal infection of C57BL/6J mice with SARS-CoV-2 beta variant, leads to CNS infiltration of Ly6Chi monocytes and microglial activation. Accordingly, SARS-CoV-2, but not H1N1 influenza virus, increases levels of brain IL-1β and induces persistent IL-1R1-mediated loss of hippocampal neurogenesis, which promotes post-acute cognitive deficits. Breakthrough infection after vaccination with a low dose of adenoviral vectored Spike protein prevents hippocampal production of IL-1β during breakthrough SARS-CoV-2 infection, loss of neurogenesis, and subsequent memory deficits. Our study identifies IL-1β as one potential mechanism driving SARS-CoV-2-induced cognitive impairment in a new murine model that is prevented by vaccination.