Anders B. Nygaard

Background: Cognitive dysfunction ("brain fog") is a commonly reported post-COVID-19 symptom. Leveraging data from five general population cohorts across four European countries (Estonia, Iceland, Norway, and Sweden), we assessed long-term prevalence of impaired subjective cognitive function among individuals diagnosed with COVID-19 by acute illness severity. Methods: The included cohorts consisted of adult participants recruited from March 2020 and followed with self-report measures of cognitive function and past COVID-19 infection (except one cohort with consisting of clinically confirmed COVID-19 cases) through February 2023. In a cross-sectional analysis we contrasted the prevalence of impaired cognitive function among individuals with and without a COVID-19 diagnosis, overall and by illness severity up to 32 months post-diagnosis. We adjusted for age, gender, education, relationship status, binge drinking, body-mass index, previous psychiatric diagnosis, number of chronic medical conditions, and response period. In a longitudinal analysis, we assessed potential changes in cognitive function scores before and after COVID-19 diagnosis. Results: The study population consisted of 153 841 participants (71% women), with 31 359 (20.4%) reporting a positive COVID-19 test. Overall, a COVID-19 diagnosis was not statistically significantly associated with increased prevalence ratio (PR) of impaired cognitive function (PR 1.30 [95% CI: 0.98–1.71]). Individuals bedridden due to COVID-19 for 1–6 days (PR 1.38 [95% CI 0.96–1.99]) or ≥7 days (2.59 [1.55–4.33]) had higher prevalence of impaired cognitive function compared to those never diagnosed, while individuals never bedridden had a lower prevalence to those never diagnosed with COVID-19 (0.89 [0.80–1.00]). These findings were corroborated in the longitudinal analysis where a pre- to post diagnosis decline in cognitive function was observed among individuals bedridden due to COVID-19 (p\textless0.0001). Conclusions: The data indicates that a severe COVID-19 acute illness course is associated with impaired cognitive function up to 18-32 months after COVID-19 diagnosis.

Aims: The Norwegian Institute of Public Health calculated excess mortality for Norway in 2024 using a reference period that included 2023—a year with significant excess mortality—and concluded there was no excess mortality in 2024. This study estimates excess mortality in 2024 using only pre-pandemic years as the reference, providing a basis for identifying excess COVID-19 related mortality. Methods: We estimated excess mortality in 2024 using a negative binomial model trained on 2010–2019 data. Deaths were modelled by age (0, 1–19, 20–39, 40–64, 65–79, 80–89 and 90+ years) and sex, with population offsets. Expected mortality was projected using both a conservative approach where the prediction for 2023 was carried forward to 2024 and a non-conservative linear extrapolation to 2024. Results: The conservative approach estimated 2898 excess deaths (7.0%; 95% prediction interval (PI), 4.9–9.1%) in 2024. Significant excess mortality was observed in age groups 1–19 (45 deaths; 36.6% excess), 20–39 (107 deaths; 17.6% excess), 40–64 (439 deaths; 10.6% excess) and 65–79 (1631 deaths; 13.7% excess). Ages 1–39 and 40–64 accounted for approximately 5% and 15% of total excess mortality, respectively. Conclusions: Persistent excess mortality from 2022 to 2024 suggests a new elevated mortality baseline and a reduction or reversal of Norway’s pre-pandemic mortality decline. Although multiple factors may contribute, given sustained excess mortality since 2022, our findings suggest that the unmitigated spread of SARS-CoV-2 in Norway since 2022 can be associated with increased mortality, particularly for those under 65.

Objectives: There is a lack of large studies on long-COVID symptoms with symptoms measurements before the onset of COVID-19. Therefore, long-COVID is still poorly defined. Methods: The Norwegian COVID-19 Cohort Study is a population-based, open cohort of adult participants (aged 18-96 years) from Norway. From March 27, 2020, participants were recruited through social media, invitations, and nationwide media coverage. Fourteen somatic and cognitive symptoms were assessed at baseline and four follow-ups for up to 22 months. SARS-CoV-2 test status was obtained from a mandatory national registry or from self-report. Results: After follow-up, 15 737 participants had a SARS-CoV-2-positive test, 67 305 had a negative test, and 37 563 were still untested. Persistent symptoms reported more frequently by positive compared with negative participants one month after infection, were memory problems (3-6 months: adjusted odds ratio (aOR) = 6.8, CI = 5.7-8.1; >18 months: aOR = 9.4, CI = 4.1-22), and concentration problems (3-6 months: aOR = 4.1, CI = 3.5-4.7; >18 months: aOR = 4.4, CI = 2.0-9.7) as well fatigue, dyspnea, anosmia and dysgeusia. Conclusions: COVID-19 was associated with cognitive symptoms, anosmia, dysgeusia, dyspnea, and fatigue as well as worsening of overall health up to 22 months after a SARS-CoV-2 test, even when correcting for symptoms before the onset of COVID-19.

Importance: Despite the major implications of executive deficits in day-to-day functioning, few studies have investigated this in post-acute sequelae of SARS-CoV-2 infection using standardized measures that differentiate between aspects of executive function. Objective: Examine whether SARS-CoV-2 infection is associated with deficits in executive functions and if so, investigate the duration of this association. Design, Setting, and Participants: The present research has a cross-sectional design and uses data from the Norwegian Covid-19 Cohort study. The current cohort (n = 8102) completed the Behavior Rating Inventory of Executive Function- Adult Version (BRIEF-A) electronically between April 2021 and September 2021. During the assessment, 4183 of the included participants had a prior positive polymerase chain reaction test (PCR) for SARS-CoV-2 and 3919 were untested or had a confirmed negative PCR test. Exposure: Laboratory-confirmed SARS-CoV-2 infection. Main outcomes and measures: Executive functions were measured using the BRIEF-A, a self-report questionnaire comprising 75 items within nine theoretically and empirically distinct clinical scales. All participants self-reported on demographical variables and comorbidity. Information on sex and age was derived from the personal identification number, and vaccination status was obtained from the Norwegian Immunization Registry (SYSVAK). Results: Participants with a positive SARS-CoV-2 status reported executive deficits in everyday life above the clinical threshold (T-score ≥65) more often than non-infected controls (383 vs. 225). Specifically, the SARS-CoV-2 positive status group indicated significantly more deficits related to metacognition, with the greatest difference demonstrated for working memory. This difference remained when adjusting for various demographic factors and comorbidities, with significantly greater odds of reporting above the clinical threshold following SARS-CoV-2 infection, as observed on the global executive composite score 6–12 months after infection (OR 1.97; 95% CI 1.51 to 2.55). Conclusions: Our study confirms more perceived executive deficits following SARS-CoV-2 infection compared to non-infected controls, with metacognitive aspects being the most affected. These findings shed light on the potential functional difficulties that individuals may encounter during the post-acute phase of SARS-CoV-2 infection and may guide further development of targeted interventions addressing metacognitive domains of executive functioning.

Objective: We aimed to describe post-acute sequelae of SARS-CoV-2 infection (PASC) related symptoms 3-15 months after a positive test in SARS-CoV-2 unvaccinated and vaccinated participants with a breakthrough infection. Methods: Participants of the Norwegian COVID-19 cohort, without a positive SARS-CoV-2 test, completed a questionnaire about PASC-related symptoms between November 2020 and January 2021. About a year later, a second questionnaire (which also included the Everyday Memory Questionnaire [EMQ]-13) was completed by the same participants, most still without a positive SARS-CoV-2 test, but also by unvaccinated and vaccinated participants with a positive test 3-15 months before the questionnaire. Laboratory-confirmed SARS-CoV-2 status (positive or negative swab test determined by reverse transcriptase quantitative polymerase chain reaction) at the time of completing the questionnaire was ascertained from the Mandatory Norwegian Surveillance System for Communicable Diseases. Results: No differences were found in the self-reported PASC symptoms, dyspnea, fatigue, smell/taste changes, concentration problems, or the EMQ-13 score between unvaccinated and vaccinated participants 3-15 months after the positive test. Fewer memory problems were reported among vaccinated than unvaccinated participants. Conclusion: SARS-CoV-2 vaccines offer minor protection against PASC symptoms, although fewer memory problems were reported among the vaccinated than the unvaccinated participants.

Objective: To determine if daily supplementation with cod liver oil, a low dose vitamin D supplement, in winter, prevents SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections in adults in Norway. Design: Quadruple blinded, randomised placebo controlled trial. Setting: Norway, 10 November 2020 to 2 June 2021. Participants: 34 601 adults (aged 18-75 years), not taking daily vitamin D supplements. Intervention: 5 mL/day of cod liver oil (10 µg of vitamin D, n=17 278) or placebo (n=17 323) for up to six months. Main outcome measures: Four co-primary endpoints were predefined: the first was a positive SARS-CoV-2 test result determined by reverse transcriptase-quantitative polymerase chain reaction and the second was serious covid-19, defined as self-reported dyspnoea, admission to hospital, or death. Other acute respiratory infections were indicated by the third and fourth co-primary endpoints: a negative SARS-CoV-2 test result and self-reported symptoms. Side effects related to the supplementation were self-reported. The fallback method was used to handle multiple comparisons. Results: Supplementation with cod liver oil was not associated with a reduced risk of any of the co-primary endpoints. Participants took the supplement (cod liver oil or placebo) for a median of 164 days, and 227 (1.31%) participants in the cod liver oil group and 228 (1.32%) participants in the placebo group had a positive SARS-CoV-2 test result (relative risk 1.00, multiple comparison adjusted confidence interval 0.82 to 1.22). Serious covid-19 was identified in 121 (0.70%) participants in the cod liver oil group and in 101 (0.58%) participants in the placebo group (1.20, 0.87 to 1.65). 8546 (49.46%) and 8565 (49.44%) participants in the cod liver oil and placebo groups, respectively, had ≥1 negative SARS-CoV-2 test results (1.00, 0.97 to 1.04). 3964 (22.94%) and 3834 (22.13%) participants in the cod liver oil and placebo groups, respectively, reported ≥1 acute respiratory infections (1.04, 0.97 to 1.11). Only low grade side effects were reported in the cod liver oil and placebo groups. Conclusion: Supplementation with cod liver oil in the winter did not reduce the incidence of SARS-CoV-2 infection, serious covid-19, or other acute respiratory infections compared with placebo. Trial registration: ClinicalTrials.gov NCT04609423.

Abstract There is a growing awareness of the importance of indoor microbiomes for human health. Given their complexity, these microbiomes can only be adequately surveyed using high throughput sequencing techniques. Oxford Nanopore’s MinION is the newest third generation sequencing technology on the market. With its many advantages such as portability, user friendliness, simplicity, speed of sequencing and long read length, the technology is now an actual contender to established sequencing platforms. MinION’s main disadvantage is a relatively low read accuracy compared to several other platforms, although this is constantly improving. The present study, which appears to be the first of its kind, provides the results of a preliminary analysis of the microbial communities in indoor environments based on 16S rRNA gene amplicon sequencing, using both the Oxford Nanopore Technologies (ONT) MinIOn and the Illumina MiSeq DNA sequencers. At the level of family and above, there was no significant difference between the microbial compositions as revealed by the two platforms. However, at the genus, and particularly at the species level, the ONT MinION reported greater taxonomic resolution than Illumina MiSeq.

In Norway, 91% of children aged 1–5 attend kindergarten where they are exposed to indoor microbiomes which can have relevance for development and health. In order to gain a better understanding of the composition of the indoor microbiome and how it is affected by occupancy over time, floor dust samples from a newly opened kindergarten were investigated. Samples were collected during an 11-month period. Samples were analyzed for bacterial composition using 16S rRNA gene sequencing. Samples were also screened for four clinically relevant antibiotic resistance genes. In addition, Petrifilm analyses were used to evaluate surface hygiene.