A Capture-Recapture-based Ascertainment Probability Weighting Method for Effect Estimation With Under-ascertained Outcomes.

Outcome under-ascertainment, characterized by the incomplete identification or reporting of cases, poses a substantial challenge in epidemiologic research. While capture-recapture methods can estimate unknown case numbers, their role in estimating exposure effects in observational studies is not well established. This paper presents an ascertainment probability weighting framework that integrates capture-recapture and propensity score weighting. We propose a nonparametric estimator of effects on binary outcomes that combines exposure propensity scores with data from two conditionally independent outcome measurements to simultaneously adjust for confounding and under-ascertainment. Demonstrating its practical application, we apply the method to estimate the relationship between health care work and coronavirus disease 2019 testing in a Swedish region. We find that ascertainment probability weighting greatly influences the estimated association compared to conventional inverse probability weighting, underscoring the importance of accounting for under-ascertainment in studies with limited outcome data coverage. We conclude with practical guidelines for the method's implementation, discussing its strengths, limitations, and suitable scenarios for application.

Analyses of quality of life in cancer drug trials - a review of measurements and analytical choices in post-reimbursement studies.

OBJECTIVES: For drugs reimbursed with limited evidence of patient benefits, confirmatory evidence of overall survival (OS) and quality of life (QoL) benefits is important. For QoL data to serve as valuable input to patients and decision-makers, it must be measured and analyzed using appropriate methods. We aimed to assess the measurement and analyses of post-reimbursement QoL data for cancer drugs introduced in Swedish healthcare with limited evidence at the time of reimbursement. METHODS: We reviewed any published post-reimbursement trial data on QoL for cancer drugs reimbursed in Sweden between 2010 and 2020 with limited evidence of improvement in QoL and OS benefits at the time of reimbursement. We extracted information on the instruments used, frequency of measurement, extent of missing data, statistical approaches, and the use of pre-registration and study protocols. RESULTS: Out of 22 drugs satisfying our inclusion criteria, we identified published QoL data for 12 drugs in 22 studies covering multiple cancer types. The most frequently used QoL instruments were EORTC QLQ-C30 and EQ-5D-3/5L. We identified three areas needing improvement in QoL measurement and analysis: (i) motivation for the frequency of measurements, (ii) handling of the substantial missing data problem, and (iii) inclusion and adherence to QoL analyses in clinical trial pre-registration and study protocols. CONCLUSIONS: Our review shows that the measurements and analysis of QoL data in our sample of cancer trials covering drugs initially reimbursed without any confirmed QoL or OS evidence have significant room for improvement. The increasing use of QoL assessments must be accompanied by a stricter adherence to best-practice guidelines to provide valuable input to patients and decision-makers.

Impact of organised colorectal cancer screening on age-specific population incidences: evidence from a quasi-experimental study in Sweden.

Colorectal cancer (CRC) incurs a significant disease burden globally. Organised CRC screening programmes have been widely implemented for early detection and prevention. To understand the public health impact of these programmes, quantitative evidence of changes in overall and age-specific population incidences is fundamental. We aimed to provide such evidence by exploiting a time lag in the implementation of organised screening in Sweden: two out of 21 regions (these two regions comprise nearly 20% of the total Swedish population) have offered organised screening since 2008; the other regions have offered CRC screening since 2021. Using registry data on diagnosed CRC cases and socio-demographics for all regions in Sweden over the period 1970-2019, Bayesian structural time series modelling and difference-in-differences were applied to analyse the impact of screening on age-specific population incidences over time (CRC cases per 100.000 persons/year). After inviting birth-year cohorts aged 60-69 years for stool-based testing, the incidence rate in the 70-74-year age group decreased significantly over time, with an average reduction of - 44·40 (95% CI - 58·15 to - 31·31) from 2011 to 2019 in the intervention regions. In the overall population aged 60-74 years, there was a net incidence decrease of - 7·99 (95% CI - 13·85 to - 2·39) since the initiation of organised screening in the intervention regions (2008-2019). Organised CRC screening for 60-69-year-olds generated a change in age-specific incidence patterns with a long-lasting incidence decrease in the 70-74-year-old population, implying reductions in the excess mortality and burden of the disease.

Proxy Variables and the Generalizability of Study Results.

When individuals self-select (or are selected) into a study based on factors that influence the outcome, conclusions may not generalize to the full population. To compensate for this, results may be adjusted, for example, by standardization on the set of common causes of participation and outcome. Although such standardization is useful in some contexts, the common causes of participation and outcome may in practice not be fully observed. Instead, the researcher may have access to one or several variables related to the common causes, that is, to proxies for the common causes. This article defines and examines different types of proxy variables and shows how these can be used to obtain generalizable study results. First of all, the researcher may exploit proxies that influence only participation or outcome but which still allow for perfect generalizability by rendering participation and outcome conditionally independent. Further, generalizability can be achieved by leveraging 2 proxies, one of which is allowed to influence participation and one of which is allowed to influence the outcome, even if participation and outcome do not become independent conditional on these. Finally, approximate generalizability may be obtained by exploiting a single proxy that does not itself influence participation or outcome.

Can non-participants in a follow-up be used to draw conclusions about incidences and prevalences in the full population invited at baseline? An investigation based on the Swedish MDC cohort.

BACKGROUND: Participants in epidemiological cohorts may not be representative of the full invited population, limiting the generalizability of prevalence and incidence estimates. We propose that this problem can be remedied by exploiting data on baseline participants who refused to participate in a re-examination, as such participants may be more similar to baseline non-participants than what baseline participants who agree to participate in the re-examination are. METHODS: We compared background characteristics, mortality, and disease incidences across the full population invited to the Malmö Diet and Cancer (MDC) study, the baseline participants, the baseline non-participants, the baseline participants who participated in a re-examination, and the baseline participants who did not participate in the re-examination. We then considered two models for estimating characteristics and outcomes in the full population: one ("the substitution model") assuming that the baseline non-participants were similar to the baseline participants who refused to participate in the re-examination, and one ("the extrapolation model") assuming that differences between the full group of baseline participants and the baseline participants who participated in the re-examination could be extended to infer results in the full population. Finally, we compared prevalences of baseline risk factors including smoking, risky drinking, overweight, and obesity across baseline participants, baseline participants who participated in the re-examination, and baseline participants who did not participate in the re-examination, and used the above models to estimate the prevalences of these factors in the full invited population. RESULTS: Compared to baseline non-participants, baseline participants were less likely to be immigrants, had higher socioeconomic status, and lower mortality and disease incidences. Baseline participants not participating in the re-examination generally resembled the full population. The extrapolation model often generated characteristics and incidences even more similar to the full population. The prevalences of risk factors, particularly smoking, were estimated to be substantially higher in the full population than among the baseline participants. CONCLUSIONS: Participants in epidemiological cohorts such as the MDC study are unlikely to be representative of the full invited population. Exploiting data on baseline participants who did not participate in a re-examination can be a simple and useful way to improve the generalizability of prevalence and incidence estimates.

Compliant sports floors and fall-related injuries: evidence from a residential care setting and updated meta-analysis for all patient care settings.

BACKGROUND: Compliant flooring may prevent fall injuries in residential care, but evidence is inconclusive. We investigate compliant sports floors and fall-related injuries in a residential care setting and update a meta-analysis from a recent systematic review on compliant flooring. METHODS: A non-randomised study comparing outcomes in a residential care unit that installed sports flooring in bedrooms with four units with regular flooring in a Norwegian municipality (n=193). Data on falls were collected for a period of 46 months (323 falls on sports flooring; 414 on regular flooring). Outcomes were injurious falls per person bed-day, falls per person bed-day and injury risks per fall. Confounding was adjusted for using Andersen-Gill proportional hazards and log-binomial regression models. Random-effects inverse variance models were used to pool estimates. RESULTS: Injurious fall rates were 13% lower in the unit with sports flooring (adjusted HR (aHR): 0.87 (95% CI: 0.55 to 1.37)). There was limited evidence of adverse effects on fall rates (aHR: 0.93 (95% CI: 0.63 to 1.38)) and the injury risk per fall was lower in fall events that occurred on sports floors (adjusted relative risk (RR): 0.75 (95% CI: 0.53 to 1.08)). Pooling these estimates with previous research added precision, but the overall pattern was the same (pooled RR for injurious falls: 0.66 (95% CI: 0.39 to 1.12); fall rates: 0.87 (95% CI: 0.68 to 1.12); injury risks per fall: 0.71 (95% CI: 0.52 to 0.97)). CONCLUSION: Sports floors may be an alternative to novel shock-absorbing floors in care settings; however, more research is needed to improve precision.

Quasi-experimental evaluation of municipal ice cleat distribution programmes for older adults in Sweden.

INTRODUCTION: Fall injuries caused by icy road conditions are a prevalent public health problem during winters in Sweden, especially in older populations. To combat this problem, many Swedish municipalities have distributed ice cleats to older adults. While previous research has shown promising results, there is a lack of comprehensive empirical data on the effectiveness of ice cleat distribution. We address this gap by investigating the impact of these distribution programmes on ice-related fall injuries among older adults. METHODS: We combined survey data on ice cleat distribution in Swedish municipalities with injury data from the Swedish National Patient Register (NPR). The survey was used to identify municipalities that have distributed ice cleats to older adults at some point between 2001 and 2019. Data from NPR were used to identify municipality-level data on patients who have been treated for injuries related to snow and ice. We used a triple differences design-a generalisation of difference in differences-that compared ice-related fall injury rates before and after intervention in 73 treatment and 200 control municipalities, with unexposed age groups serving as within-municipality controls. RESULTS: We estimate that the average ice cleat distribution programmes reduced ice-related fall injury rates by -0.24 (95% CI -0.49 to 0.02) per 1000 person-winters. The impact estimate was larger in municipalities that distributed more ice cleats (-0.38 (95% CI -0.76 to -0.09)). No similar patterns were found for fall injuries unrelated to snow and ice. CONCLUSION: Our results suggest that ice cleat distribution can decrease the incidence of ice-related injuries among older adults.

A comparison of small-area deprivation indicators for public-health surveillance in Sweden.

AIMS: The aims of this study were to construct a small-area index of multiple deprivation (IMD) from single deprivation indicators (SDIs) and to compare the explanatory power of the IMD and SDIs with regard to mortality. We considered a small-area division of Sweden consisting of 5985 DeSO (Demografiska statistikområden), each with a population size between 653 and 4243 at the end of 2018. METHODS: Four SDIs were provided by open-source data: (a) the proportion of inhabitants with a low economic standard; (b) the proportion of inhabitants aged 25-64 years with ⩽12 years of schooling; (c) the proportion of inhabitants aged 16-64 years who were not in paid employment; and (d) the proportion of inhabitants who lived in a rented apartment/house. A four-indicator IMD was constructed using factor analysis. As a validation, the IMD and SDIs were compared by exploring their DeSO-level associations with spatially smoothed death rates, with robustness checks of associations across different small-area contexts defined by degree of urbanisation and distribution of immigrants from non-Western countries. RESULTS: The constructed IMD and SDI1 performed essentially equally and outperformed SDI2, SDI3 and SDI4. Associations between IMD/SDI1 and the spatially smoothed death rates were most pronounced within the age range 60-79 years, showing 5-8% lowered rates among those categorised in the least deprived quintiles of IMD and SDI1, respectively, and 7-9% elevated rates among those categorised in the most deprived quintiles. These associations were consistent within each small-area context. CONCLUSIONS: We suggest prioritisation of SDI1, that is, a DeSO-level deprivation indicator based on open-access data on economic standard, for public-health surveillance in Sweden.

Occupational role and COVID-19 among foreign-born healthcare workers in Sweden: a registry-based study.

BACKGROUND: Many studies report that foreign-born healthcare workers (HCWs) in high-income countries have an elevated risk of COVID-19. However, research has not yet specifically evaluated the distribution of COVID-19 among foreign-born workers in different healthcare work groups. We examined the risk of COVID-19 infection and hospitalization among foreign-born HCWs in different occupational roles in Sweden. METHODS: We linked occupational data (2019) of 783 950 employed foreign-born workers (20-65 years) to COVID-19 data registered between 1 January 2020 and 30 September 2021. We used Cox proportional hazards regression to estimate the hazard ratio (HR) with 95% confidence intervals (95% CIs) of COVID-19 infection and hospitalization in eight healthcare occupational groups vs. non-HCWs and assessed whether region of birth modified the association between healthcare occupations and COVID-19. RESULTS: All HCWs had a higher risk of COVID-19 outcomes than non-HCWs, but the risk differed by occupational role. Hospital-based assistant nurses had the highest risk (infection: HR 1.78; 95% CI 1.72-1.85; hospitalization: HR 1.79; 95% CI 1.52-2.11); allied HCWs had the lowest risk (infection: HR 1.22; 95% CI 1.10-1.35; hospitalization: HR 0.98; 95% CI 0.59-1.63). The relative hazard of the outcomes varied across foreign-born workers from different regions. For example, the relative risk of COVID-19 infection associated with being a physician compared to a non-HCW was 31% higher for African-born than European-born workers. CONCLUSIONS: The risk of COVID-19 among foreign-born HCWs differed by occupational role and immigrant background. Public health efforts that target occupational exposures as well as incorporate culturally responsive measures may help reduce COVID-19 risk among foreign-born HCWs.

Community factors and excess mortality in the COVID-19 pandemic in England, Italy and Sweden.

BACKGROUND: Analyses of coronavirus disease 19 suggest specific risk factors make communities more or less vulnerable to pandemic-related deaths within countries. What is unclear is whether the characteristics affecting vulnerability of small communities within countries produce similar patterns of excess mortality across countries with different demographics and public health responses to the pandemic. Our aim is to quantify community-level variations in excess mortality within England, Italy and Sweden and identify how such spatial variability was driven by community-level characteristics. METHODS: We applied a two-stage Bayesian model to quantify inequalities in excess mortality in people aged 40 years and older at the community level in England, Italy and Sweden during the first year of the pandemic (March 2020-February 2021). We used community characteristics measuring deprivation, air pollution, living conditions, population density and movement of people as covariates to quantify their associations with excess mortality. RESULTS: We found just under half of communities in England (48.1%) and Italy (45.8%) had an excess mortality of over 300 per 100 000 males over the age of 40, while for Sweden that covered 23.1% of communities. We showed that deprivation is a strong predictor of excess mortality across the three countries, and communities with high levels of overcrowding were associated with higher excess mortality in England and Sweden. CONCLUSION: These results highlight some international similarities in factors affecting mortality that will help policy makers target public health measures to increase resilience to the mortality impacts of this and future pandemics.

Long-term effects on healthcare utilisation among spouses of persons with stroke.

BACKGROUND: Stroke is a common and costly disease affecting the person with stroke and their relatives. If the negative effect on the health of informal caregivers to a person with stroke translates into an increased healthcare consumption has not yet been studied. Further, the importance of including costs and health consequences of informal caregiving in health economic evaluation supporting decision-making is an ongoing discussion. Therefore, this study aims to estimate the long-term effect on healthcare utilisation among spouses of persons with a first-ever stroke. METHOD: The study population consists of spouses of persons with first-ever stroke events in 2010-2011 and a reference population matched on age, sex and municipality of residence. We have access to information on healthcare utilisation five years before and five years after the stroke event for the whole study population. Using a difference-in-difference approach, the main analysis estimates the effects on primary and specialist outpatient care visits and days with inpatient care per year. Further, we analyse the healthcare utilisation among spouses depending on the modified Rankin Scale (mRS) of the person with stroke. RESULTS: Our main analysis indicates that spouses have slightly more days with inpatient care five years after the stroke event than the reference population (p = 0.03). In contrast, spouses have fewer primary and specialist outpatient care visits than the reference population following the stroke event. In the analysis where spouses' healthcare utilisation is analysed according to the mRS status of the person with stroke, we identify the most notable change in the number of visits to specialist outpatient and days with inpatient care among spouses of persons with mRS 3 (dependency in daily activities). CONCLUSION: Our study suggests that being the spouse of a person with stroke has minor effects on healthcare utilisation. Further, healthcare utilisation is most affected among the spouses of persons with stroke and dependency in daily activities (mRS 3). According to our results, it does not seem vital to include spouses of persons with stroke healthcare utilisation in health economic evaluations.

Cost-effectiveness analysis of left atrial appendage occlusion in patients with atrial fibrillation and contraindication to oral anticoagulation.

AIMS: This study aims to estimate the cost-effectiveness of percutaneous left atrial appendage occlusion (LAAO) compared to standard stroke prevention care for patients with atrial fibrillation (AF) and contraindication to oral anticoagulation (OAC) in a Swedish healthcare and public sector perspective. METHODS AND RESULTS: We used a combined decision tree and cohort Markov model to estimate costs and quality-adjusted life-years (QALYs) over a lifetime horizon with LAAO compared to standard of care where the treatment effect is based on a recent meta-analysis. According to our analysis, LAAO gives more QALYs than standard of care (7.11 vs. 6.12). Furthermore, LAAO treatment is related to the first-year cost of 14 984 Euro (EUR) and higher average healthcare costs over the lifetime by about 4010 EUR, which gives an incremental cost-effectiveness ratio of LAAO vs. standard of care at 4047 EUR per gained QALY. From a public sector perspective, LAAO reduces average costs due to substantial reductions in long-term care and, thus, implies that LAAO is dominant from a public sector perspective (lower average costs and better health outcomes). CONCLUSION: From both Swedish healthcare and public sector perspectives, LAAO can be considered cost-effective compared to standard of care for individuals with AF and contraindication to OAC. However, these results must be confirmed in health economic evaluations alongside the ongoing randomized clinical trials. KEY QUESTION: Is left atrial appendage occlusion (LAAO) cost-effective for patients with atrial fibrillation (AF) and contraindication to oral anticoagulation (OAC) compared to the standard of care from a Swedish healthcare and public sector perspective? KEY FINDING: LAAO is associated with lower cost than the standard of care from a public sector perspective and an incremental cost of 4010 Euro from a healthcare perspective. Furthermore, LAAO is related to better health outcomes than the standard of care. TAKE HOME MESSAGE: Treatment with LAAO among individuals with AF and contraindication to OAC can be considered as cost-effective compared to the standard of care from a Swedish healthcare and public sector perspective.

Prevalence of Subclinical Coronary Artery Atherosclerosis in the General Population.

BACKGROUND: Early detection of coronary atherosclerosis using coronary computed tomography angiography (CCTA), in addition to coronary artery calcification (CAC) scoring, may help inform prevention strategies. We used CCTA to determine the prevalence, severity, and characteristics of coronary atherosclerosis and its association with CAC scores in a general population. METHODS: We recruited 30 154 randomly invited individuals age 50 to 64 years to SCAPIS (the Swedish Cardiopulmonary Bioimage Study). The study includes individuals without known coronary heart disease (ie, no previous myocardial infarctions or cardiac procedures) and with high-quality results from CCTA and CAC imaging performed using dedicated dual-source CT scanners. Noncontrast images were scored for CAC. CCTA images were visually read and scored for coronary atherosclerosis per segment (defined as no atherosclerosis, 1% to 49% stenosis, or ≥50% stenosis). External validity of prevalence estimates was evaluated using inverse probability for participation weighting and Swedish register data. RESULTS: In total, 25 182 individuals without known coronary heart disease were included (50.6% women). Any CCTA-detected atherosclerosis was found in 42.1%; any significant stenosis (≥50%) in 5.2%; left main, proximal left anterior descending artery, or 3-vessel disease in 1.9%; and any noncalcified plaques in 8.3% of this population. Onset of atherosclerosis was delayed on average by 10 years in women. Atherosclerosis was more prevalent in older individuals and predominantly found in the proximal left anterior descending artery. Prevalence of CCTA-detected atherosclerosis increased with increasing CAC scores. Among those with a CAC score >400, all had atherosclerosis and 45.7% had significant stenosis. In those with 0 CAC, 5.5% had atherosclerosis and 0.4% had significant stenosis. In participants with 0 CAC and intermediate 10-year risk of atherosclerotic cardiovascular disease according to the pooled cohort equation, 9.2% had CCTA-verified atherosclerosis. Prevalence estimates had excellent external validity and changed marginally when adjusted to the age-matched Swedish background population. CONCLUSIONS: Using CCTA in a large, random sample of the general population without established disease, we showed that silent coronary atherosclerosis is common in this population. High CAC scores convey a significant probability of substantial stenosis, and 0 CAC does not exclude atherosclerosis, particularly in those at higher baseline risk.

Factors predicting participation and potential yield of screening-detected disease among non-participants in a Swedish population-based atrial fibrillation screening study.

BACKGROUND: The success of any screening program is dependent on participation. The characteristics of participants vs. non-participants have been studied and non-participants usually have a higher risk of disease. The potential yield of screening-detected disease in non-participants could be of interest to several screening programs. AIMS: This is a sub-study to STROKESTOP II, a Swedish atrial fibrillation screening study. The aim was to study factors predicting participation and to estimate the potential yield of screening-detected disease in non-participants. METHODS: Individual, anonymized data for participants and non-participants with respect to socioeconomic factors, medical history and drugs dispensed were obtained from Swedish registries. A random forest model was trained to predict propensity scores for participation. The propensity scores were used to estimate potential screening-detected disease among non-participants. RESULTS: Non-participants (n = 7086) had lower income, were more likely to have been hospitalized and had higher CHA2DS2-VASc scores compared to participants (n = 6868). The strongest factor predicting non-attendance was low income. The weighted estimates suggested that the yield of new atrial fibrillation was 2.4% in non-participants compared to 2.3% in the participants, which was not significant. CONCLUSIONS: Non-participants had higher CHA2DS2-VASc scores, indicating a higher stroke-risk and presumable benefit from attending screening, although estimated new atrial fibrillation detected was not significantly more common when compared to participants. Low income was the strongest factor for predicting non-attendance and should be a focus area when planning future screening scenarios.

Model-based economic evaluation of ice cleat distribution programmes for the prevention of outdoor falls among adults from a Swedish societal perspective.

BACKGROUND: Slipping on snow or ice poses a significant health risk among older adults in Sweden. To combat this problem, about 80 Swedish municipalities have distributed ice cleats to older citizens (65+ years old) over the last decade. This paper details a cost-benefit analysis of such programmes. MATERIALS AND METHODS: We developed a decision-analytical model to estimate the costs and benefits of ice cleat programmes in Swedish municipalities compared with a business-as-usual scenario. The modelled benefits of the programme were based on effect estimates from previous research, data from population and healthcare registers and a survey of attitudes to and actual ice cleat use. The modelled costs of the programme were based on resource use data collected from 34 municipalities with existing ice cleat programmes. We assessed heterogeneity in the potential impact and benefit-to-cost ratios across all Swedish municipalities as a function of the average number of days with snow cover per year. Uncertainty in the cost-benefit results was assessed using deterministic and probabilistic sensitivity analyses. RESULTS: The average benefit-to-cost ratio was 87, ranging from about 40 in low-risk municipalities to 140 in high-risk municipalities, implying that the potential benefits of ice cleat programmes greatly outweigh their costs. Probabilistic and deterministic sensitivity analyses support the robustness of this conclusion to parameter uncertainty and large changes in assumptions about the magnitude of the impact on ice cleat use and injuries. CONCLUSION: The benefits of distributing ice cleats to older adults appear to outweigh the costs from a Swedish societal perspective.

Ice cleat distribution programmes and ice cleat use among older adults: repeated cross-sectional evidence from 63 municipal interventions in Sweden.

INTRODUCTION: Ice cleats may help prevent ice-related falls in places with icy roads, but there is limited evidence about the association between ice cleat distribution and ice cleat use. Our study examined the association between Swedish municipal distribution programmes and ice cleat use among older adults (65+ years). METHODS: We combined data on municipal ice cleat distribution programmes (n=63) with repeated cross-sectional self-reports of ice cleat use in Sweden from 2007, 2010, 2014 and 2018. Respondents (n=63 234) were classified as exposed if they lived in a municipality with a programme, belonged to an eligible age group and responded after distribution (n=2507). Dose-response was assessed using distributed ice cleat pairs per capita (mean: 0.38). Linear probability models were used to estimate probability differences in ice cleat use between exposed and unexposed respondents, adjusting for age, sex, country of birth, education, survey wave and municipality. Ineligible age groups living in programme municipalities, who should be unaffected by ice cleat distribution, were used for bias assessment. RESULTS: Exposure to ice cleat distribution programmes was associated with 7.5 percentage points (95% CI 4.2 to 10.9) higher self-reported ice cleat use after confounding adjustment. The association was larger in municipalities that distributed one pair of ice cleats per capita (17.3 percentage points (95% CI 11.2 to 23.4)). No association was found among the ineligible age groups (-2.3 (95% CI -5.5 to 1.0)). CONCLUSION: Distributing ice cleats to older adults may help increase their use of ice cleats in settings with icy road conditions.

A regression discontinuity analysis of the social distancing recommendations for older adults in Sweden during COVID-19.

BACKGROUND: This article investigates the impact of a non-mandatory and age-specific social distancing recommendation on isolation behaviours and disease outcomes in Sweden during the first wave of the coronavirus disease 2019 (COVID-19) pandemic (March to July 2020). The policy stated that people aged 70 years or older should avoid crowded places and contact with people outside the household. METHODS: We used a regression discontinuity design-in combination with self-reported isolation data from COVID Symptom Study Sweden (n = 96 053; age range: 39-79 years) and national register data (age range: 39-100+ years) on severe COVID-19 disease (hospitalization or death, n = 21 804) and confirmed cases (n = 48 984)-to estimate the effects of the policy. RESULTS: Our primary analyses showed a sharp drop in the weekly number of visits to crowded places (-13%) and severe COVID-19 cases (-16%) at the 70-year threshold. These results imply that the age-specific recommendations prevented approximately 1800-2700 severe COVID-19 cases, depending on model specification. CONCLUSIONS: It seems that the non-mandatory, age-specific recommendations helped control COVID-19 disease during the first wave of the pandemic in Sweden, as opposed to not implementing a social distancing policy aimed at older adults. Our study provides empirical data on how populations may react to non-mandatory, age-specific social distancing policies in the face of a novel virus.

COVID-19 vaccine effectiveness against severe disease from SARS-CoV-2 Omicron BA.1 and BA.2 subvariants - surveillance results from southern Sweden, December 2021 to March 2022.

We compared vaccine effectiveness against severe COVID-19 between December 2021 and March 2022 when Omicron BA.1 and BA.2 were the dominating SARS-CoV-2 variants in Scania county, Sweden. Effectiveness remained above 80% after the transition from BA.1 to BA.2 among people with at least three vaccine doses but the point estimate decreased markedly to 54% among those with only two doses. Protection from prior infection was also lower after the transition to BA.2. Booster vaccination seems necessary to maintain sufficient protection.

Risk of severe COVID-19 from the Delta and Omicron variants in relation to vaccination status, sex, age and comorbidities - surveillance results from southern Sweden, July 2021 to January 2022.

We compared the risk of severe COVID-19 during two periods 2021 and 2022 when Delta and Omicron, respectively, were the dominating virus variants in Scania county, Sweden. We adjusted for differences in sex, age, comorbidities, prior infection and vaccination. Risk of severe disease from Omicron was markedly lower among vaccinated cases. It was also lower among the unvaccinated but remained high (> 5%) for older people and middle-aged men with two or more comorbidities. Efforts to increase vaccination uptake should continue.

Synthetic Control Methods for the Evaluation of Single-Unit Interventions in Epidemiology: A Tutorial.

Evaluating the impacts of population-level interventions (e.g., changes to state legislation) can be challenging as conducting randomized experiments is often impractical and inappropriate, especially in settings where the intervention is implemented in a single, aggregate unit (e.g., a country or state). A common nonrandomized alternative is to compare outcomes in the treated unit(s) with unexposed controls both before and after the intervention. However, the validity of these designs depends on the use of controls that closely resemble the treated unit on before-intervention characteristics and trends on the outcome, and suitable controls may be difficult to find because the number of potential control regions is typically limited. The synthetic control method provides a potential solution to these problems by using a data-driven algorithm to identify an optimal weighted control unit-a "synthetic control"-based on data from before the intervention from available control units. While popular in the social sciences, the method has not garnered as much attention in health research, perhaps due to a lack of accessible texts aimed at health researchers. We address this gap by providing a comprehensive, nontechnical tutorial on the synthetic control method, using a worked example evaluating Florida's "stand your ground" law to illustrate methodological and practical considerations.