Unintended Perinatal Health Consequences Associated With a Swedish Family Policy.

Importance: The 1980 and 1986 Swedish so-called speed premium policies aimed at protecting parents' income-based parental leave benefits for birth intervals shorter than 24 and 30 months, respectively, but indirectly encouraged shorter birth spacing and childbearing at older ages, both risk factors for several perinatal health outcomes. Whether those policy changes are associated with perinatal health remains unknown. Objective: To evaluate the association between the 1980 and 1986 speed premium policies and perinatal health outcomes. Design, Setting, and Participants: This cross-sectional study investigated data from 1 762 784 singleton births in the Swedish Medical Birth Register from January 1, 1974, through December 31, 1991. Data were analyzed from October 11, 2022, to December 12, 2023. Interventions: Speed premium policy introduction (January 1, 1980) and extension (January 1, 1986). Main Outcomes and Measures: Total population register data were used in an interrupted time series analysis with segmented logistic regression to calculate the odds of preterm birth, low birth weight, small for gestational age (SGA) at preterm, and stillbirth measured before and after the speed premium policy reforms. Subgroup analyses by maternal origin were conducted to evaluate changes by different policy responses. Results: Among 1 762 784 births analyzed, 4.8% were preterm (of which 12.0% were SGA), 3.2% had low birth weight, and 0.3% were stillbirths. The 1980 speed premium policy was associated with a 0.3% monthly increase in the odds of preterm birth compared with the period before the reform (odds ratio [OR], 1.0029 [95% CI, 1.002-1.004]), equivalent to a 26.4% increase from January 1, 1980, to December 31, 1985. After the 1986 relaxation of the policy, preterm birth odds decreased 0.5% per month (OR, 0.9951 [95% CI, 0.994-0.996]), equivalent to an 11.1% decrease across the next 6 years. Low birth weight displayed a similar pattern for both reform periods, that is, increased 0.2% (OR, 1.0021; 95% CI, 1.001-1.003) per month in 1980 through 1985 compared with baseline, and decreased 0.3% (OR, 0.9975; 95% CI, 0.996-0.998) per month in the following period, but was attenuated when considering low birth weight at term. Odds of SGA at preterm were decreased after 1980 (OR, 0.9965; 95% CI, 0.994-0.999) but not in 1986 (OR, 1.0009; 95% CI, 0.998-1.003), whereas stillbirths did not change following either reform (1980: OR, 1.0020 [95% CI, 0.999-1.005]; 1986: OR, 1.0002 [95% CI, 0.997-1.003]). Subgroup analyses suggested that perinatal health changes were restricted to births to Swedish- and Nordic-born mothers, the primary groups to adjust their fertility behaviors to the reforms. Conclusions and Relevance: Despite its economic advantages for couples, especially for mothers, the introduction of the speed premium policy was associated with adverse perinatal health consequences, particularly for preterm births. Family policies should be carefully designed with a "Health in All Policies" lens to avoid possible unintended repercussions for fertility behaviors and, in turn, perinatal health.

COVID-19 mortality among immigrants by duration of residence in Sweden: a population-based cohort study.

BACKGROUND: Explanations for the disproportional COVID-19 burden among immigrants relative to host-country natives include differential exposure to the virus and susceptibility due to poor health conditions. Prior to the pandemic, immigrants displayed deteriorating health with duration of residence that may be associated with increased susceptibility over time. The aim of this study was to compare immigrant-native COVID-19 mortality by immigrants' duration of residence to examine the role of differential susceptibility. METHODS: A population-based cohort study was conducted with individuals between 18 and 100 years old registered in Sweden between 1 January 2015 and 15 June 2022. Cox regression models were run to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: Inequalities in COVID-19 mortality between immigrants and the Swedish-born population in the working-age group were concentrated among those of non-Western origins and from Finland with more than 15 years in Sweden, while for those of retirement age, these groups showed higher COVID-19 mortality HRs regardless of duration of residence. Both age groups of immigrants from Africa and the Middle East showed consistently higher COVID-19 mortality HRs. For the working-age population: Africa: HR<15: 2.46, 95%CI: 1.78, 3.38; HR≥15: 1.49, 95%CI: 1.01, 2.19; and from the Middle East: HR<15: 1.20, 95%CI: 0.90, 1.60; HR≥15: 1.65, 95%CI: 1.32, 2.05. For the retirement-age population: Africa: HR<15: 3.94, 95%CI: 2.85, 5.44; HR≥15: 1.66, 95%CI: 1.32, 2.09; Middle East: HR<15: 3.27, 95%CI: 2.70, 3.97; HR≥15: 2.12, 95%CI: 1.91, 2.34. CONCLUSIONS: Differential exposure, as opposed to differential susceptibility, likely accounted for the higher COVID-19 mortality observed among those origins who were disproportionately affected by the pandemic in Sweden.

Inequalities in COVID-19 severe morbidity and mortality by country of birth in Sweden.

Migrants have been more affected by the COVID-19 pandemic. Whether this has varied over the course of the pandemic remains unknown. We examined how inequalities in intensive care unit (ICU) admission and death related to COVID-19 by country of birth have evolved over the course of the pandemic, while considering the contribution of social conditions and vaccination uptake. A population-based cohort study was conducted including adults living in Sweden between March 1, 2020 and June 1, 2022 (n = 7,870,441). Poisson regressions found that migrants from Africa, Middle East, Asia and European countries without EU28/EEA, UK and Switzerland had higher risk of COVID-19 mortality and ICU admission than Swedish-born. High risks of COVID-19 ICU admission was also found in migrants from South America. Inequalities were generally reduced through subsequent waves of the pandemic. In many migrant groups socioeconomic status and living conditions contributed to the disparities while vaccination campaigns were decisive when such became available.

Parent-Child Nativity, Race, Ethnicity, and Common Mental Health Conditions Among United States Children and Adolescents.

OBJECTIVE: To examine associations between race, ethnicity, and parent-child nativity, and common mental health conditions among U.S. children and adolescents. METHODS: Data were from 2016 to 2019 National Survey of Children's Health, a US population-based, serial cross-sectional survey, and restricted to children who had access to health care. We used weighted multivariable logistic regression to examine the associations between race and ethnicity (Asian, Black, Hispanic, White, Other-race); mental health outcomes (depression, anxiety, and behavior/conduct problems) stratified by household generation; and between household generation and outcomes stratified by race and ethnicity, adjusting for demographics (age, sex, family income to poverty ratio, parental education), and an adverse childhood experience (ACE) score. RESULTS: When stratifying by household generation, racial and ethnic minority children generally had similar to lower odds of outcomes compared with White children, with the exception of higher odds of behavior/conduct problems among third + -generation Black children. When stratifying by race and ethnicity, third + generation children had increased odds of depression compared to their first-generation counterparts. Third + generation, racial and ethnic minority children had increased odds of anxiety and behavior/conduct problems compared with their first-generation counterparts. The associations generally remained significant after adjusting for the ACE score. CONCLUSIONS: Lower odds of common mental health conditions in racial and ethnic minority children could be due to factors such as differential reporting, and higher estimates, including those in third + generation children, could be due to factors including discrimination; systemic racism; and other factors that vary by generation and need further investigation to advance health equity.

Explaining COVID-19 mortality among immigrants in Sweden from a social determinants of health perspective (COVIS): protocol for a national register-based observational study.

INTRODUCTION: Adopting a social determinants of health perspective, this project aims to study how disproportionate COVID-19 mortality among immigrants in Sweden is associated with social factors operating through differential exposure to the virus (eg, by being more likely to work in high-exposure occupations) and differential effects of infection arising from socially patterned, pre-existing health conditions, differential healthcare seeking and inequitable healthcare provision. METHODS AND ANALYSIS: This observational study will use health (eg, hospitalisations, deaths) and sociodemographic information (eg, occupation, income, social benefits) from Swedish national registers linked using unique identity numbers. The study population includes all adults registered in Sweden in the year before the start of the pandemic (2019), as well as individuals who immigrated to Sweden or turned 18 years of age after the start of the pandemic (2020). Our analyses will primarily cover the period from 31 January 2020 to 31 December 2022, with updates depending on the progression of the pandemic. We will evaluate COVID-19 mortality differences between foreign-born and Swedish-born individuals by examining each mechanism (differential exposure and effects) separately, while considering potential effect modification by country of birth and socioeconomic factors. Planned statistical modelling techniques include mediation analyses, multilevel models, Poisson regression and event history analyses. ETHICS AND DISSEMINATION: This project has been granted all necessary ethical permissions from the Swedish Ethical Review Authority (Dnr 2022-0048-01) for accessing and analysing deidentified data. The final outputs will primarily be disseminated as scientific articles published in open-access peer-reviewed international journals, as well as press releases and policy briefs.

Is it Better to Intermarry? Immigration Background of Married Couples and Suicide Risk Among Native-Born and Migrant Persons in Sweden.

Marriage is protective against suicide across most populations, including for persons of different ethnicities and immigrant backgrounds. However, the well-being benefits of marriage are contingent upon marital characteristics-such as conflict and quality-that may vary across spousal dyads with different immigration backgrounds. Leveraging Swedish register data, we compare suicide mortality among married persons on the basis of their and their spouse's immigration backgrounds. We find that relative to those in a native Swede-Swede union, Swedish men married to female immigrants and immigrant women married to native men are at higher risk of death by suicide, while immigrants of both genders who are married to someone from their birth country have a lower risk of suicide mortality. The findings support hypotheses about the strains that may be encountered by those who intermarry, as well as the potential selection of individuals into inter- and intra-ethnic marriages.

Differences in hospitalizations associated with severe COVID-19 disease among foreign- and Swedish-born.

BACKGROUND: Differences in pre-existing health conditions are hypothesized to explain immigrants' excess COVID-19 mortality compared to natives. In this study, we evaluate whether immigrants residing in Sweden before the outbreak were more likely to be hospitalized for conditions associated with severe COVID-19 disease. METHODS: A cohort study using population-register data was conducted with follow-up between 1 January 1997 and 31 December 2017. Poisson regression was fitted to estimate incidence rate ratio (RR) and 95% confident intervals (95% CI) for 10 causes of hospitalization. RESULTS: Compared to Swedish-born individuals, most immigrant groups showed a decreased risk of hospitalization for respiratory chronic conditions, CVD, cancer, chronic liver conditions and neurological problems. All immigrant groups had increased risk of hospitalization for tuberculosis [RR between 88.49 (95% CI 77.21; 101.40) for the Horn of Africa and 1.69 (95% CI 1.11; 2.58) for North America], HIV [RR between 33.23 (95% CI 25.17; 43.88) for the rest of Africa and 1.31 (95% CI 0.93; 1.83) for the Middle East] and, with a few exceptions, also for chronic kidney conditions, diabetes and thalassemia. CONCLUSIONS: Foreign-born individuals-including origins with excess COVID-19 mortality in Sweden-did not show increased risk of hospitalizations for most causes associated with severe COVID-19 disease. However, all groups showed increased risks of hospitalization for tuberculosis and HIV and, with exceptions, for chronic kidney conditions, diabetes and thalassemia. Although studies should determine whether these health conditions explain the observed excess COVID-19 mortality, our study alerts to an increased risk of hospitalization that can be avoidable via treatment or preventive measures.

Maternal age and the risk of low birthweight and pre-term delivery: a pan-Nordic comparison.

BACKGROUND: Advanced maternal age at birth is considered a risk factor for adverse birth outcomes. A recent study applying a sibling design has shown, however, that the association might be confounded by unobserved maternal characteristics. METHODS: Using total population register data on all live singleton births during the period 1999-2012 in Denmark (N = 580 133; 90% population coverage), Norway (N = 540 890) and Sweden (N = 941 403) and from 2001-2014 in Finland (N = 568 026), we test whether advanced maternal age at birth independently increases the risk of low birthweight (LBW) (<2500 g) and pre-term birth (<37 weeks gestation). We estimated within-family models to reduce confounding by unobserved maternal characteristics shared by siblings using three model specifications: Model 0 examines the bivariate association; Model 1 adjusts for parity and sex; Model 2 for parity, sex and birth year. RESULTS: The main results (Model 1) show an increased risk in LBW and pre-term delivery with increasing maternal ages. For example, compared with maternal ages of 26-27 years, maternal ages of 38-39 years display a 2.2, 0.9, 2.1 and 2.4 percentage point increase in the risk of LBW in Denmark, Finland, Norway and Sweden, respectively. The same patterns hold for pre-term delivery. CONCLUSIONS: Advanced maternal age is independently associated with higher risk of poor perinatal health outcomes even after adjusting for all observed and unobserved factors shared between siblings.

Immigrant ancestry and birthweight across two generations born in Sweden: an intergenerational cohort study.

INTRODUCTION: Differences in birthweight are often seen between migrants and natives. However, whether migrant-native birthweight inequalities widen, narrow or remain persistent across generations when comparing the descendants of immigrants and natives remains understudied. We examined inequalities in birthweight of mothers (G2) and daughters (G3) of foreign-born grandmothers (G1) compared with those of Swedish-born grandmothers. METHODS: We used population registers with multigenerational linkages to identify 314 415 daughters born in Sweden during the period 1989-2012 (G3), linked to 246 642 mothers (G2) born in Sweden during 1973-1996, and to their grandmothers (G1) who were Swedish or foreign-born. We classified migrants into non-western, Eastern European, the rest of Nordic and Western. We used multivariable methods to examine mean birthweight and low birthweight (<2500 g; LBW). RESULTS: Birthweight between individuals with Swedish background (G1) and non-western groups increased from -80 g to -147 g between G2 (mothers) and G3 (daughters), respectively. Furthermore, the odds of LBW increased among the G3 non-western immigrants compared with those with Swedish grandmothers (OR: 1.38, 95% CI 1.12 to 1.69). Birthweight increased in both descendants of Swedes and non-western immigrants, but less so in the latter (83 g vs 16 g). CONCLUSION: We observed an increase in birthweight inequalities across generations between descendants of non-western immigrants and descendants of Swedes. This finding is puzzling considering Sweden has been lauded for its humanitarian approach to migration, for being one of the most egalitarian countries in the world and providing universal access to healthcare and education.

COVID-19 mortality across occupations and secondary risks for elderly individuals in the household: A population register-based study.

OBJECTIVES: This is the first population-level study to examine inequalities in COVID-19 mortality according to working-age individuals' occupations and the indirect occupational effects on COVID-19 mortality of older individuals who live with them. METHODS: We used early-release data for the entire population of Sweden of all recorded COVID-19 deaths from 12 March 2020 to 23 February 2021, which we linked to administrative registers and occupational measures. Cox proportional hazard models assessed relative risks of COVID-19 mortality for the working-aged population registered in an occupation in December 2018 and the older population who lived with them. RESULTS: Among working aged-adults, taxi/bus drivers had the highest relative risk of COVID-19 mortality: over four times that of skilled workers in IT, economics, or administration when adjusted only for basic demographic characteristics. After adjusting for socioeconomic factors (education, income and country of birth), there are no occupational groups with clearly elevated (statistically significant) COVID-19 mortality. Neither a measure of exposure within occupations nor the share that generally can work from home were related to working-aged adults' risk of COVID-19 mortality. Instead of occupational factors, traditional socioeconomic risk factors best explained variation in COVID-19 mortality. Elderly individuals, however, faced higher COVID-19 mortality risk both when living with a delivery or postal worker or worker(s) in occupations that generally work from home less, even when their socioeconomic factors are taken into account. CONCLUSIONS: Inequalities in COVID-19 mortality of working-aged adults were mostly based on traditional risk factors and not on occupational divisions or characteristics in Sweden. However, older individuals living with those who likely cannot work from home or work in delivery or postal services were a vulnerable group.

The cognitive development from childhood to adolescence of low birthweight children born after medically assisted reproduction-a UK longitudinal cohort study.

BACKGROUND: Previous research has documented that children conceived through medically assisted reproduction (MAR) are at increased risk of poor birth outcomes, such as low birthweight (LBW), which are risk factors for stunted longer-term cognitive development. However, parents who undergo MAR to conceive have, on average, advantaged socioeconomic backgrounds which could compensate for the negative effects of being born LBW. Previous studies have not analysed whether the negative effects of LBW are attenuated among MAR conceived children. METHODS: We draw on the UK Millennium Cohort Study (sweeps 1-6) which contains a sub-sample of (N = 396) MAR-conceived children. The dependent variable measures cognitive ability at around ages 3, 5, 7, 11 and 14. We examine the cognitive development of four groups of children: MAR-conceived low birthweight (MAR LBW); MAR-conceived non-low birthweight (MAR NLBW); naturally conceived low birthweight (NC LBW); naturally conceived non-low birthweight (NC NLBW). We estimate the two following linear regression models for each sweep: (i) a baseline model to examine the unadjusted association between cognitive development and low birthweight by mode of conception; and (ii) a model adjusted by socio-demographic family characteristics. RESULTS: In baseline models, MAR LBW children [age 3: ß = 0.021, 95% confidence interval (CI): -0.198, 0.241; age 5: ß = 0.21, 95% CI: 0.009, 0.418; age 7: ß = 0.163, 95% CI: -0.148, 0.474; age 11: ß = 0.003, 95% CI: -0.318, 0.325; age 14: ß = 0.156, 95% CI: -0.205, 0.517], on average perform similarly in cognitive ability relative to NC NLBW at all ages, and display higher cognitive scores than NC LBW children until age 7. When we account for family characteristics, differences are largely attenuated and become close to zero at age 14. CONCLUSIONS: Despite the higher incidence of LBW among MAR compared with NC children, they do not seem to experience any disadvantage in their cognitive development compared with naturally conceived children. This finding is likely explained by the fact that, on average, MAR children are born to socioeconomically advantaged parents.

Intermarriage and COVID-19 mortality among immigrants. A population-based cohort study from Sweden.

OBJECTIVES: To evaluate the role of language proficiency and institutional awareness in explaining excess COVID-19 mortality among immigrants. DESIGN: Cohort study with follow-up between 12 March 2020 and 23 February 2021. SETTING: Swedish register-based study on all residents in Sweden. PARTICIPANTS: 3 963 356 Swedish residents in co-residential unions who were 30 years of age or older and alive on 12 March 2020 and living in Sweden in December 2019. OUTCOME MEASURES: Cox regression models were conducted to assess the association between different constellations of immigrant-native couples (proxy for language proficiency and institutional awareness) and COVID-19 mortality and all other causes of deaths (2019 and 2020). Models were adjusted for relevant confounders. RESULTS: Compared with Swedish-Swedish couples (1.18 deaths per thousand person-years), both immigrants partnered with another immigrant and a native showed excess mortality for COVID-19 (HR 1.43; 95% CI 1.29 to 1.58 and HR 1.24; 95% CI 1.10 to 1.40, respectively), which translates to 1.37 and 1.28 deaths per thousand person-years. Moreover, similar results are found for natives partnered with an immigrant (HR 1.15; 95% CI 1.02 to 1.29), which translates to 1.29 deaths per thousand person-years. Further analysis shows that immigrants from both high-income and low-income and middle-income countries (LMIC) experience excess mortality also when partnered with a Swede. However, having a Swedish-born partner is only partially protective against COVID-19 mortality among immigrants from LMIC origins. CONCLUSIONS: Language barriers and/or poor institutional awareness are not major drivers for the excess mortality from COVID-19 among immigrants. Rather, our study provides suggestive evidence that excess mortality among immigrants is explained by differential exposure to the virus.

The cognitive development from childhood to adolescence of low birthweight children born after medically assisted reproduction-a UK longitudinal cohort study.

BACKGROUND: Previous research has documented that children conceived through medically assisted reproduction (MAR) are at increased risk of poor birth outcomes, such as low birthweight (LBW), which are risk factors for stunted longer-term cognitive development. However, parents who undergo MAR to conceive have, on average, advantaged socioeconomic backgrounds which could compensate for the negative effects of being born LBW. Previous studies have not analysed whether the negative effects of LBW are attenuated among MAR conceived children. METHODS: We draw on the UK Millennium Cohort Study (sweeps 1-6) which contains a sub-sample of (N = 396) MAR-conceived children. The dependent variable measures cognitive ability at around ages 3, 5, 7, 11 and 14. We examine the cognitive development of four groups of children: MAR-conceived low birthweight (MAR LBW); MAR-conceived non-low birthweight (MAR NLBW); naturally conceived low birthweight (NC LBW); naturally conceived non-low birthweight (NC NLBW). We estimate the two following linear regression models for each sweep: (i) a baseline model to examine the unadjusted association between cognitive development and low birthweight by mode of conception; and (ii) a model adjusted by socio-demographic family characteristics. RESULTS: In baseline models, MAR LBW children [age 3: ß = 0.021, 95% confidence interval (CI): -0.198, 0.241; age 5: ß = 0.21, 95% CI: 0.009, 0.418; age 7: ß = 0.163, 95% CI: -0.148, 0.474; age 11: ß = 0.003, 95% CI: -0.318, 0.325; age 14: ß = 0.156, 95% CI: -0.205, 0.517], on average perform similarly in cognitive ability relative to NC NLBW at all ages, and display higher cognitive scores than NC LBW children until age 7. When we account for family characteristics, differences are largely attenuated and become close to zero at age 14. CONCLUSIONS: Despite the higher incidence of LBW among MAR compared with NC children, they do not seem to experience any disadvantage in their cognitive development compared with naturally conceived children. This finding is likely explained by the fact that, on average, MAR children are born to socioeconomically advantaged parents.

How Assad changed population growth in Sweden and Norway: Syrian refugees' impact on Nordic national and municipal demography.

In an increasingly interconnected world, the demographic effects of wars are not confined only to war zones and neighbouring areas; wars and conflicts may also change populations far away. Without the war in Syria under President Assad and the associated mass exodus of Syrian refugees, the population trends in distant countries like Sweden and Norway over the last few years would have been different. We create hypothetical scenarios of the population developments in Sweden and Norway without a war in Syria from 2011 onwards, where excess immigration due to the war and associated excess births are removed. The results indicate that population growth in 2016 would have been roughly 36% lower in Sweden and 26% lower in Norway without the Syrian war. The number of births in 2017 would have been about 3% lower in Sweden and 1% lower in Norway. One in ten municipalities would have had a population decline in 2016 instead of a population increase, and the largest immigrant group in Sweden by January 2019 would still be of Finnish origin.

A population-based cohort study of socio-demographic risk factors for COVID-19 deaths in Sweden.

As global deaths from COVID-19 continue to rise, the world's governments, institutions, and agencies are still working toward an understanding of who is most at risk of death. In this study, data on all recorded COVID-19 deaths in Sweden up to May 7, 2020 are linked to high-quality and accurate individual-level background data from administrative registers of the total population. By means of individual-level survival analysis we demonstrate that being male, having less individual income, lower education, not being married all independently predict a higher risk of death from COVID-19 and from all other causes of death. Being an immigrant from a low- or middle-income country predicts higher risk of death from COVID-19 but not for all other causes of death. The main message of this work is that the interaction of the virus causing COVID-19 and its social environment exerts an unequal burden on the most disadvantaged members of society.

Residential context and COVID-19 mortality among adults aged 70 years and older in Stockholm: a population-based, observational study using individual-level data.

BACKGROUND: Housing characteristics and neighbourhood context are considered risk factors for COVID-19 mortality among older adults. The aim of this study was to investigate how individual-level housing and neighbourhood characteristics are associated with COVID-19 mortality in older adults. METHODS: For this population-based, observational study, we used data from the cause-of-death register held by the Swedish National Board of Health and Welfare to identify recorded COVID-19 mortality and mortality from other causes among individuals (aged ≥70 years) in Stockholm county, Sweden, between March 12 and May 8, 2020. This information was linked to population-register data from December, 2019, including socioeconomic, demographic, and residential characteristics. We ran Cox proportional hazards regressions for the risk of dying from COVID-19 and from all other causes. The independent variables were area (m2) per individual in the household, the age structure of the household, type of housing, confirmed cases of COVID-19 in the borough, and neighbourhood population density. All models were adjusted for individual age, sex, country of birth, income, and education. FINDINGS: Of 279 961 individuals identified to be aged 70 years or older on March 12, 2020, and residing in Stockholm in December, 2019, 274 712 met the eligibility criteria and were included in the study population. Between March 12 and May 8, 2020, 3386 deaths occurred, of which 1301 were reported as COVID-19 deaths. In fully adjusted models, household and neighbourhood characteristics were independently associated with COVID-19 mortality among older adults. Compared with living in a household with individuals aged 66 years or older, living with someone of working age (<66 years) was associated with increased COVID-19 mortality (hazard ratio 1·6; 95% CI 1·3-2·0). Living in a care home was associated with an increased risk of COVID-19 mortality (4·1; 3·5-4·9) compared with living in independent housing. Living in neighbourhoods with the highest population density (≥5000 individuals per km2) was associated with higher COVID-19 mortality (1·7; 1·1-2·4) compared with living in the least densely populated neighbourhoods (0 to <150 individuals per km2). INTERPRETATION: Close exposure to working-age household members and neighbours is associated with increased COVID-19 mortality among older adults. Similarly, living in a care home is associated with increased mortality, potentially through exposure to visitors and care workers, but also due to poor underlying health among care-home residents. These factors should be considered when developing strategies to protect this group. FUNDING: Swedish Research Council for Health, Working Life and Welfare (FORTE), Swedish Foundation for Humanities and Social Sciences.

Repeat immigration: A previously unobserved source of heterogeneity?

AIMS: Register data allow for nuanced analyses of heterogeneities between sub-groups which are not observable in other data sources. One heterogeneity for which register data is particularly useful is in identifying unique migration histories of immigrant populations, a group of interest across disciplines. Years since migration is a commonly used measure of integration in studies seeking to understand the outcomes of immigrants. This study constructs detailed migration histories to test whether misclassified migrations may mask important heterogeneities. In doing so, we identify a previously understudied group of migrants called repeat immigrants, and show that they differ systematically from permanent immigrants. In addition, we quantify the degree to which migration information is misreported in the registers. METHOD: The analysis is carried out in two steps. First, we estimate income trajectories for repeat immigrants and permanent immigrants to understand the degree to which they differ. Second, we test data validity by cross-referencing migration information with changes in income to determine whether there are inconsistencies indicating misreporting. RESULTS: From the first part of the analysis, the results indicate that repeat immigrants systematically differ from permanent immigrants in terms of income trajectories. Furthermore, income trajectories differ based on the way in which years since migration is calculated. The second part of the analysis suggests that misreported migration events, while present, are negligible. CONCLUSIONS: Repeat immigrants differ in terms of income trajectories, and may differ in terms of other outcomes as well. Furthermore, this study underlines that Swedish registers provide a reliable data source to analyze groups which are unidentifiable in other data sources.