Reversing accidents involving pedestrians: an epidemiological investigation and cluster analysis using a novel database derived from Swedish National Register data.

OBJECTIVES: In contemporary urban environments, the intersection between Vulnerable Road Users, specifically unprotected pedestrians, and motor vehicles poses a persistent challenge to road safety. Reversing accidents, characterized by vehicles moving backward, often result in severe consequences for pedestrians due to limited visibility and inherent blind spots for the driver. This paper aims to provide a thorough examination of reversing accidents involving pedestrians in Sweden between 2000-2021; shedding light on the magnitude of the problem, contributing factors, consequences, and potential mitigation strategies. METHOD: Using a national database, reversing accidents were compiled by classifying free text descriptions of traffic accidents reported to the Swedish Traffic Accident Data Acquisition. The database was then used to describe reversing accidents and their consequences for struck pedestrians using descriptive epidemiology and cluster analysis. RESULTS: The results show that reversing accidents accounted for 12% of all pedestrians injured in a collision with a motor vehicle in Sweden during the studied period. In terms of personal characteristics, the struck pedestrians were more often female and of old or young age, whilst the drivers of the reversing vehicles were more often between 18-54 years and men. Most accidents were non-fatal, with only roughly 2% resulting in fatalities. Through a cluster analysis, four distinct accident types were identified. Two of these were identified as particularly important to prioritize in future preventative work: accidents that are characterized by occur during daylight hours in the urban environment (often low speeds) and often result in fatality or serious injury. CONCLUSIONS: Due to the low speeds, reversing accidents are rarely fatal. However, they account for a large proportion of accidents with pedestrians and can be grouped into clearly distinguishable accident types that can function as templates in road safety development in Sweden.

Sociodemographic differences in the response to changes in COVID-19 testing guidelines.

During the coronavirus disease 2019 (COVID-19) pandemic, Sweden emphasized voluntary guidelines over mandates. We exploited a rapid change and reversal of the Public Health Agency of Sweden's COVID-19 testing guidelines for vaccinated and recently infected individuals as a quasi-experiment to examine sociodemographic differences in the response to changes in pandemic guidelines. We analyzed daily polymerase chain reaction tests from 1 October 2021 to 15 December 2021, for vaccinated or recently infected adults (≥20 years; n = 1 596 321) from three Swedish regions (Stockholm, Örebro, and Dalarna). Using interrupted time series analysis, we estimated abrupt changes in testing rates at the two dates when the guidelines were changed (1 November and 22 November). Stratified analysis and meta-regression were employed to explore sociodemographic differences in the strength of the response to the guideline changes. Testing rates declined substantially when guideline against testing of vaccinated and recently infected individuals came into effect on 1 November [testing rate ratio: 0.50 (95% confidence interval, CI 0.41, 0.61)], and increased again from these lowered levels by a similar amount upon its reversal on 22 November [testing rate ratio: 2.19 (95% CI: 1.69, 2.85)]. Being Sweden-born, having higher household income, or higher education, were all associated with a stronger adherent response to the guideline changes. Adjusting for stratum-specific baseline testing rates and test-positivity did not influence the results. Our findings suggest that the population was responsive to the rapid changes in testing guidelines, but with clear sociodemographic differences in the strength of the response.

Self-Report Tool for Identification of Individuals With Coronary Atherosclerosis: The Swedish CardioPulmonary BioImage Study.

BACKGROUND: Coronary atherosclerosis detected by imaging is a marker of elevated cardiovascular risk. However, imaging involves large resources and exposure to radiation. The aim was, therefore, to test whether nonimaging data, specifically data that can be self-reported, could be used to identify individuals with moderate to severe coronary atherosclerosis. METHODS AND RESULTS: We used data from the population-based SCAPIS (Swedish CardioPulmonary BioImage Study) in individuals with coronary computed tomography angiography (n=25 182) and coronary artery calcification score (n=28 701), aged 50 to 64 years without previous ischemic heart disease. We developed a risk prediction tool using variables that could be assessed from home (self-report tool). For comparison, we also developed a tool using variables from laboratory tests, physical examinations, and self-report (clinical tool) and evaluated both models using receiver operating characteristic curve analysis, external validation, and benchmarked against factors in the pooled cohort equation. The self-report tool (n=14 variables) and the clinical tool (n=23 variables) showed high-to-excellent discriminative ability to identify a segment involvement score ≥4 (area under the curve 0.79 and 0.80, respectively) and significantly better than the pooled cohort equation (area under the curve 0.76, P<0.001). The tools showed a larger net benefit in clinical decision-making at relevant threshold probabilities. The self-report tool identified 65% of all individuals with a segment involvement score ≥4 in the top 30% of the highest-risk individuals. Tools developed for coronary artery calcification score ≥100 performed similarly. CONCLUSIONS: We have developed a self-report tool that effectively identifies individuals with moderate to severe coronary atherosclerosis. The self-report tool may serve as prescreening tool toward a cost-effective computed tomography-based screening program for high-risk individuals.

Colorectal cancer screening with fecal immunochemical testing or primary colonoscopy: inequities in diagnostic yield.

BACKGROUND: Socioeconomic inequalities in the uptake of colorectal cancer screening are well documented, but the implications on inequities in health gain remain unclear. METHODS: Sixty-year-olds were randomly recruited from the Swedish population between March 2014 and March 2020 and invited to undergo either 2 rounds of fecal immunochemical testing (FIT) 2 years apart (n = 60 137) or primary colonoscopy just once (n = 30 400). By linkage to Statistics Sweden's registries, we obtained socioeconomic data. In each defined socioeconomic group, we estimated the cumulative yield of advanced neoplasia in each screening arm (intention-to-screen analysis). In the biennial FIT arm, we predicted the probability of exceeding the yield in the primary colonoscopy arm by linear extrapolation of the cumulative yield to (hypothetical) additional rounds of FIT. RESULTS: In the lowest income group, the yield of advanced neoplasia was 1.63% (95% confidence interval [CI] = 1.35% to 1.93%) after 2 rounds of FIT vs 1.93% (95% CI = 1.49% to 2.40%) in the primary colonoscopy arm. Extrapolation to a third round of FIT implied a 86% probability of exceeding the yield in the primary colonoscopy arm. In the highest income group, we found a more pronounced yield gap between the 2 screening strategies-2.32% (95% CI = 2.15% to 2.49%) vs 3.71% (95% CI = 3.41% to 4.02%)- implying a low (2%) predicted probability of exceeding yield after a third round of FIT. CONCLUSIONS: Yield of advanced neoplasia from 2 rounds of FIT 2 years apart was poorer as compared with primary colonoscopy, but the difference was less in lower socioeconomic groups. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT02078804.

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.

Previous SARS-CoV-2 infections and their impact on the protection from reinfection during the Omicron BA.5 wave - a nested case-control study among vaccinated adults in Sweden.

Objectives: We evaluated the protection afforded by SARS-CoV-2 infection-induced immunity against reinfection among working-age vaccinated individuals during a calendar period from June to December 2022 when Omicron BA.5 was the dominating subvariant in Scania County, Sweden. Methods: The study cohort (n = 71,592) mainly consisted of health care workers. We analyzed 4144 infected cases during the Omicron BA.5 dominance and 41,440 sex- and age-matched controls with conditional logistic regression. Results: The average protection against reinfection was marginal (16%, 95% confidence interval [CI] 7-23%) during the study period but substantially higher for recent infections. Recent infection (3-6 months) with Omicron BA.2 and BA.5 offered strong protection (86%, 95% CI 68-94% and 78%, 95% CI 69-84%), whereas more distant infection (6-12 months) with Omicron BA.1, BA.2, and the variants before Omicron offered marginal or no protection. Conclusions: These findings suggest that infection-induced immunity contributes to short-term population protection against infection with the subvariant BA.5 among working-age vaccinated individuals but wanes considerably with time, independent of the virus variant.

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.

Adherence to a handheld device-based atrial fibrillation screening protocol is associated with clinical outcomes.

OBJECTIVE: To evaluate adherence and adherence consistency to the handheld ECG device-based screening protocol and their association with adverse cerebral and cardiovascular outcomes in two systematic atrial fibrillation (AF) screening programmes. METHODS: In 2012 (Systematic ECG Screening for Atrial Fibrillation Among 75-Year Old Subjects in the Region of Stockholm and Halland, Sweden (STROKESTOP) study) and 2016 (Stepwise mass screening for atrial fibrillation using N-terminal pro b-type natriuretic peptide (STROKESTOP II) study), half of all 75- and 76-year-old inhabitants of up to two Swedish regions were invited to participate in a systematic AF screening programme. Participants were instructed to perform 30-second measurements twice daily in STROKESTOP and four times daily in STROKESTOP II for 2 weeks. Adherence was defined as the number of measurements performed divided by the number of measurements asked, whereas adherence consistency was defined as the number of days with complete registrations. RESULTS: In total, 6436 participants (55.7% female) from STROKESTOP and 3712 (59.8% female) from STROKESTOP II were included. Median adherence and adherence consistency were 100 (92-100)% and 12 (11-13) days in STROKESTOP and 90 (75-98)% and 8 (3-11) days in STROKESTOP II. Female sex and lower education were factors associated with both optimal adherence and adherence consistency in both studies. In STROKESTOP, low adherence and adherence consistency were associated with higher risk of adverse cerebral and cardiovascular outcomes (HR for composite primary endpoint 1.30 (1.11 to 1.51), p=0.001), including stroke (HR 1.68 (1.22 to 2.32), p=0.001) and dementia (1.67 (1.27 to 2.19), p<0.001). CONCLUSIONS: Adherence to twice daily handheld ECG measurements in STROKESTOP was higher than to four times daily measurements in STROKESTOP II. Female sex and lower educational attainment were associated with ≥100% adherence and adherence consistency. Low adherence and adherence consistency were associated with a higher risk of adverse outcomes.

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.

The impact of stroke on spousal and family income: a difference-in-difference study from Swedish national registries.

AIM: To investigates the financial consequences in the overall population spouses of persons with stroke in Sweden as well as for subgroups based on spouses age, sex and modified Rankin Scale (mRS) of the person with stroke. METHODS: The study population consists of spouses aged ≤ 60 during the year of their partner's stroke event. Each spouse was matched to four reference individuals. This longitudinal registry data covers spouses and a reference population between 2005 and 2016. We use difference-in-differences to estimate the impact on individual income from paid work, disposable individual income, and disposable family income. RESULTS: The primary analysis shows a small and statistically insignificant decrease on spouses' individual income from paid work and disposable individual income. In the subgroup analysis based on mRS, the largest effect is seen in mRS 4-5, where spouses' individual income from paid work and disposable individual income increases after their partner's stroke. Further, younger female spouses' individual income from paid work decreases by 1 614 EUR (p = 0.008) on average. CONCLUSION: The financial consequences are small in the overall population of spouses. However, for some subgroups, younger women, and spouses of persons with stroke and mRS 4-5, the financial consequences are more prominent.

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.

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.

Examining the continuum of resistance model in two population-based screening studies in Sweden.

In studies recruited on a voluntary basis, lack of representativity may impair the ability to generalize findings to the target population. Previous studies, primarily based on surveys, have suggested that generalizability may be improved by exploiting data on individuals who agreed to participate only after receiving one or several reminders, as such individuals may be more similar to non-participants than what early participants are. Assessing this idea in the context of screenings, we compared sociodemographic characteristics and health across early, late, and non-participants in two large population-based screening studies in Sweden: STROKESTOP II (screening for atrial fibrillation; 6,867 participants) and SCREESCO (screening for colorectal cancer; 39,363 participants). We also explored the opportunities to reproduce the distributions of characteristics in the full invited populations, either by assuming that the non-participants were similar to the late participants, or by applying a linear extrapolation model based on both early and late participants. Findings showed that early and late participants exhibited similar characteristics along most dimensions, including civil status, education, income, and health examination results. Both these types of participants in turn differed from the non-participants, with fewer married, lower educational attainments, and lower incomes. Compared to early participants, late participants were more likely to be born outside of Sweden and to have comorbidities, with non-participants similar or even more so. The two empirical models improved representativity in some cases, but not always. Overall, we found mixed support that data on late participation may be useful for improving representativeness of screening studies.

Cancer Drugs Reimbursed with Limited Evidence on Overall Survival and Quality of Life: Do Follow-Up Studies Confirm Patient Benefits?

BACKGROUND AND OBJECTIVE: Cancer drug costs have increased considerably within healthcare systems, but many drugs lack quality-of-life (QoL) and overall survival (OS) data at the time of reimbursement approval. This study aimed to review the extent of subsequent literature documenting improvements in OS and QoL for cancer drug indications where no such evidence existed at the time of reimbursement approval. METHODS: Drug indications with claims of added therapeutical value but a lack of evidence on OS and QoL that were reimbursed between 2010 and 2020 in Sweden were included for review. Searches were conducted in PubMed and ClinicalTrial.gov for randomized controlled trials examining OS and QoL. RESULTS: Of the 22 included drug indications, seven were found to have at least one trial with conclusive evidence of improvements in OS or QoL after a mean follow-up of 6.6 years. The remaining 15 drug indications either lacked subsequent randomized controlled trial data on OS or QoL (n = 6) or showed no statistically significant improvements (n = 9). Only one drug demonstrated evidence of improvement in both OS and QoL for its indication. CONCLUSIONS: A considerable share of reimbursed cancer drug indications continue to lack evidence of improvement in both OS and QoL. With limited healthcare resources and an increasing cancer burden, third-party payers have strong incentives to require additional post-reimbursement data to confirm any improvements in OS and QoL.

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.

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.

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.

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.

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.