A hybrid register and questionnaire study of Covid-19 and post-acute sick leave in Denmark

Demographic and socioeconomic characteristics of the women invited to the COVIDPregDK cohort: a non-response analysis

Aim: This study aimed to examine the demographic characteristics associated with participation in the COVIDPregDK cohort, aiming to identify potential sources of selection bias. Methods: In this nationwide register-based cohort study, data were used from the COVIDPregDK study, which encompasses a cohort of pregnant women from 2020 and linked them to data from the Danish registries. A comparison between women responding and those who did not respond to the questionnaire was conducted to assess their demographic and socioeconomic characteristics. The associations between respondents and various characteristics were analysed using logistic regression models. Results: The questionnaire garnered a response rate of 60%, with participation from 17,047 pregnant women and non-participation from 11,577. Respondent women were most often 30-34 years of age, of Danish origin, highly educated, and had the highest family income than non-respondents. Additionally, women above 35 years represented the most decisive risk factor of responding (35-39: odds ratio (OR) 1.17 (95% confidence interval (CI) 1.08-1.27); 40+: OR 1.27 95% CI 1.10-1.48)). Characteristics of non-respondents: families with three or more children (OR 0.55 (95% CI 0.47-0.64)); immigrants (OR 0.38 (95% CI 0.35-0.40)) and descendants (OR 0.39 (95% CI 0.34-0.45)); low educated (OR 0.40 (95% CI 0.36-0.44)) and low income (OR 0.67 (95% CI 0.61-0.72)). Conclusions: This study found significant demographic and socioeconomic disparities between respondent and non-respondent pregnant women in the COVIDPregDK study, indicating higher participation from women with higher socioeconomic status. Despite the societal lockdown during COVID-19, the lockdown did not mitigate the pre-existing factors hindering women with low socioeconomic status from engaging in research.

Health-related adverse work outcomes associated with post COVID-19 condition: a cross-sectional study

Introduction

Symptoms from post COVID-19 condition (PCC) can impair functioning in working-age adults. However, there is uncertainty about the relationship between PCC and work outcomes. This study aimed to assess health-related adverse work outcomes in individuals with a PCC history compared with others who had COVID-19.

Methods

This was a cross-sectional study in which participants in British Columbia (BC) completed an online questionnaire. Participants comprised adults who tested positive for SARS-CoV-2 by PCR at least 2 years before questionnaire completion and were working age (18-64) at the time of infection. PCC status was determined by self-report. The health-related adverse work outcomes evaluated included change in occupation or employer, reduced workload, increased sick days compared with before COVID-19, early retirement and indefinite sick leave. Analyses were weighted to reflect the characteristics of individuals who had COVID-19 in BC. Propensity score overlap weighting was used to adjust for relevant sociodemographic and clinical covariates.

Results

Among 1106 participants, 966 (87.3%) were employed when they contracted SARS-CoV-2 and included in analyses. Of these participants, 47.8% were female, the median age was 37 and 46.9% had a PCC history. Compared with other individuals who had COVID-19, those with a PCC history were more likely to have had a health-related adverse work outcome (46.5% vs 24.9%; adjusted OR (aOR) 2.6 (95% CI 1.7 to 4.0)) and reported a greater number of sick days in the first 2 years since contracting SARS-CoV-2 (adjusted mean difference 43 days (95% CI 20 to 65)). The risk of a health-related adverse work outcome was especially high in those with post-COVID-19 fatigue (aOR 4.6 (95% CI 2.7 to 7.9)), fever (aOR 4.0 (95% CI 1.7 to 9.6)), weakness (aOR 3.8 (95% CI 2.2 to 6.3)), palpitations (aOR 3.3 (95% CI 2.0 to 5.0)) and brain fog (aOR 3.2 (95% CI 2.0 to 5.0)).

Conclusions

PCC is associated with health-related adverse work outcomes. This is an important consideration for clinicians, employers and health system leaders.

Post-COVID-19 Condition Fatigue Outcomes Among Danish Residents

Importance

Fatigue remains one of the most common and debilitating symptoms of post-COVID-19 condition; however, existing studies are limited to select populations and often lack noninfected controls. It also remains unclear to what extent severity of infection and psychiatric conditions, which are often linked to chronic fatigue, modify the risk of post-COVID-19 condition fatigue symptoms.

Objective

To evaluate the impact of SARS-CoV-2 infection on self-reported fatigue and postexertional malaise over time and to explore possible risk factors, such as the impact of acute SARS-CoV-2 hospitalization and preexisting psychiatric conditions on postacute fatigue.

Design, Setting, and Participants

In this cohort study, Danish residents aged 15 years and older were invited to participate in the EFTER-COVID survey, which used repeated, self-reported online questionnaires that collected information on fatigue (Fatigue Assessment Scale) and postexertional malaise scores (DePaul Symptom Questionnaire) after individuals' index SARS-CoV-2 polymerase chain reaction test. Participants were included if they completed a baseline and at least 1 follow-up questionnaire 2 to 18 months after testing for SARS-CoV-2.

Exposure

Testing for SARS-CoV-2 infection.

Main Outcomes and Measures

The primary outcomes were fatigue and postexertional malaise 2 to 18 months after testing. Mixed-effects models were used to compare scores between SARS-CoV-2 test-positive and test-negative individuals (testing period April 2021 to February 2023).

Results

Of a total of 50 115 participants (median [IQR] age at test date, 57 [46-67] years; 29 774 female [59.4%]), 25 249 were test positive and 24 866 were test negative. Most participants were vaccinated with at least 2 doses (21 164 test-negative participants [85.1%] and 22 120 test-positive participants [87.6%]) before their SARS-CoV-2 index test and fatigue reporting. In the period 2 to 18 months after testing, SARS-CoV-2 infection was associated with a small but significant 3% increase in self-reported fatigue scores (score ratio [SR], 1.03; 95% CI, 1.03-1.04) and higher odds of self-reported postexertional malaise (odds ratio, 2.04; 95% CI, 1.81-2.30), compared with test-negative participants. In the same period, hospitalization with SARS-CoV-2 increased fatigue scores by 23% (SR, 1.23; 95% CI, 1.20-1.26) compared with test-negative participants. Preexisting psychiatric conditions did not significantly modify postacute fatigue scores.

Conclusions and Relevance

In this cohort study, SARS-CoV-2 infection was associated with a subtle increase in self-reported fatigue and postexertional malaise symptoms 2 to 18 months after mild infection. In contrast, individuals hospitalized with acute SARS-CoV-2 experienced a more substantial increase in postacute symptoms. Preexisting psychiatric conditions did not significantly modify the risk of postacute fatigue symptoms. The findings largely captured symptoms following first-time infections in a population where most had been vaccinated. Persons who experienced severe acute infection may benefit from clinical follow-up for fatigue.

Changes in Working Situations of Employed Long COVID Patients: Retrospective Study in Japanese Outpatient Clinic

Purpose: The present study aimed to uncover the impact of long COVID on the working situations of Japanese patients. Methods: Changes in the working situations of the patients who visited our long COVID clinic were evaluated from medical records for the aspects of physical status, quality of life (QOL), and mental conditions. Results: Of 846 long COVID patients who visited our clinic from February 2021 to December 2023, 545 employed patients aged between 18 and 65 years were included in this study. A total of 295 patients (54.1%) with long COVID (median age: 43 years, female: 55.6%) experienced changes in their working status. Those patients included 220 patients (40.4%) who took a leave of absence, 53 patients (9.7%) who retired, and 22 patients (4%) with reduced working hours. Most of the patients (93.2%) with changes in working conditions had mild disease severity in the acute phase of COVID-19. The majority of those patients with mild disease severity (58.8%) were infected in the Omicron-variant phase and included 65.3% of the female patients. The major symptoms in long COVID patients who had changes in their working situations were fatigue, insomnia, headache, and dyspnea. Scores indicating fatigue and QOL were worsened in long COVID patients who had changes in their working situations. In addition, 63.7% of the long COVID patients with changes in their working situations had decreases in their incomes. Conclusions: Changes in the working situation of long COVID patients who were employed had a negative impact on the maintenance of their QOL.

Exploring the dynamics of COVID-19 in a Greenlandic cohort: Mild acute illness and moderate risk of long COVID

Objectives

This study aimed to explore how the Greenlandic population experienced the course of both acute and long-term COVID-19. It was motivated by the unique epidemiologic situation in Greenland, with delayed community transmission of SARS-CoV-2 relative to the rest of the world.

Methods

In a survey among 310 Greenlandic adults, we assessed the association between previous SARS-CoV-2 infection and overall health outcomes by administering three repeated questionnaires over 12 months after infection, with a response rate of 41% at the 12-month follow-up. The study included 128 individuals with confirmed SARS-CoV-2 infection from January/February 2022 and 182 test-negative controls. Participants were recruited through personal approaches, phone calls, and social media platforms.

Results

A total of 53.7% of 162 participants who were test-positive recovered within 4 weeks and 2.5% were hospitalized due to SARS-CoV-2. The most common symptoms were fatigue and signs of mild upper respiratory tract infection. Less than 5% reported sick leave above 2 weeks after infection. Compared with participants who were test-negative, there was an increased risk of reporting fatigue (risk differences 25.4%, 95% confidence interval 8.8-44.0) and mental exhaustion (risk differences 23.4%, 95% confidence interval 4.8-42.2) up to 12 months after a positive test.

Conclusions

Our results indicate that during a period dominated by the Omicron variant, Greenlanders experienced a mild acute course of COVID-19, with quick recovery, minimizing the impact on sick leave. Long COVID may be present in Greenlanders, with symptoms persisting up to 12 months after infection. However, it is important to consider the small sample size and modest response rate as limitations when interpreting the results.

Cohort profile: EFTER-COVID - a Danish nationwide cohort for assessing the long-term health effects of the COVID-19 pandemic

PURPOSE

To follow SARS-CoV-2-infected persons up to 18 months after a positive test in order to assess the burden and nature of post acute symptoms and health problems.

PARTICIPANTS

Persons in Denmark above 15 years of age, who were tested positive for SARS-CoV-2 during 1 September 2020 to 21 February 2023 using a RT-PCR test. As a reference group, three test-negative individuals were selected for every two test-positive individuals by matching on test date.

FINDINGS TO DATE

In total, 2 427 913 invitations to baseline questionnaires have been sent out and 839 528 baseline questionnaires (34.5%) have been completed. Females, the age group 50-69 years, Danish-born and persons, who had received at least one SARS-CoV-2 vaccination booster dose were more likely to participate. Follow-up questionnaires were sent at 2, 4, 6, 9, 12 and 18 months after the test, with response rates at 42%-54%.

FUTURE PLANS

New participants have been recruited on a daily basis from 1 August 2021 to 23 March 2023. Data collection will continue until the last follow-up questionnaires (at 18 months after test) have been distributed in August 2024.

Machine learning identifies risk factors associated with long-term sick leave following COVID-19 in Danish population

BACKGROUND

Post COVID-19 condition (PCC) can lead to considerable morbidity, including prolonged sick-leave. Identifying risk groups is important for informing interventions. We investigated heterogeneity in the effect of SARS-CoV-2 infection on long-term sick-leave and identified subgroups at higher risk.

METHODS

We conducted a hybrid survey and register-based retrospective cohort study of Danish residents who tested positive for SARS-CoV-2 between November 2020 and February 2021 and a control group who tested negative, with no known history of SARS-CoV-2. We estimated the causal risk difference (RD) of long-term sick-leave due to PCC and used the causal forest method to identify individual-level heterogeneity in the effect of infection on sick-leave. Sick-leave was defined as >4 weeks of full-time sick-leave from 4 weeks to 9 months after the test.

RESULTS

Here, in a cohort of 88,818 individuals, including 37,482 with a confirmed SARS-CoV-2 infection, the RD of long-term sick-leave is 3.3% (95% CI 3.1% to 3.6%). We observe a high degree of effect heterogeneity, with conditional RDs ranging from -3.4% to 13.7%. Age, high BMI, depression, and sex are the most important variables explaining heterogeneity. Among three-way interactions considered, females with high BMI and depression and persons aged 36-45 years with high BMI and depression have an absolute increase in risk of long-term sick-leave above 10%.

CONCLUSIONS

Our study supports significant individual-level heterogeneity in the effect of SARS-CoV-2 infection on long-term sick-leave, with age, sex, high BMI, and depression identified as key factors. Efforts to curb the PCC burden should consider multimorbidity and individual-level risk.