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.

Comorbidities in women with polycystic ovary syndrome: a sibling study

BACKGROUND

Polycystic ovary syndrome (PCOS) has previously been associated with several comorbidities that may have shared genetic, epigenetic, developmental or environmental origins. PCOS may be influenced by prenatal androgen excess, poor intrauterine or childhood environmental factors, childhood obesity and learned health risk behaviors. We analyzed the association between PCOS and several relevant comorbidities while adjusting for early-life biological and socioeconomic conditions, also investigating the extent to which the association is affected by familial risk factors.

METHODS

This total-population register-based cohort study included 333,999 full sisters, born between 1962 and 1980. PCOS and comorbidity diagnoses were measured at age 17-45 years through national hospital register data from 1997 to 2011, and complemented with information on the study subjects´ early-life and social characteristics. In the main analysis, sister fixed effects (FE) models were used to control for all time-invariant factors that are shared among sisters, thereby testing whether the association between PCOS and examined comorbidities is influenced by unobserved familial environmental, social or genetic factors.

RESULTS

Three thousand five hundred seventy women in the Sister sample were diagnosed with PCOS, of whom 14% had obesity, 8% had depression, 7% had anxiety and 4% experienced sleeping, sexual and eating disorders (SSE). Having PCOS increased the odds of obesity nearly 6-fold (adjusted OR (aOR): 5.9 [95% CI:5.4-6.5]). This association was attenuated in models accounting for unobserved characteristics shared between full sisters, but remained considerable in size (Sister FE: aOR: 4.5 [95% CI: 3.6-5.6]). For depression (Sister FE: aOR: 1.4 [95% CI: 1.2-1.8]) and anxiety (Sister FE: aOR: 1.5 [95% CI: 1.2-1.8), there was a small decrease in the aORs when controlling for factors shared between sisters. Being diagnosed with SSE disorders yielded a 2.4 aOR (95% CI:2.0-2.6) when controlling for a comprehensive set of individual-level confounders, which only decreased slightly when controlling for factors at the family level such as shared genes or parenting style. Accounting for differences between sisters in observed early-life circumstances influenced the estimated associations marginally.

CONCLUSION

Having been diagnosed with PCOS is associated with a markedly increased risk of obesity and sleeping, sexual and eating disorders, also after accounting for factors shared between sisters and early-life conditions.

Risk of long COVID and associated symptoms after acute SARS-COV-2 infection in ethnic minorities: A nationwide register-linked cohort study in Denmark

BACKGROUND

Ethnic minorities living in high-income countries have been disproportionately affected by Coronavirus Disease 2019 (COVID-19) in terms of infection rates, hospitalisations, and deaths; however, less is known about long COVID in these populations. Our aim was to examine the risk of long COVID and associated symptoms among ethnic minorities.

METHODS AND FINDINGS

We used nationwide register-based cohort data on individuals diagnosed with COVID-19 aged ≥18 years (n = 2,287,175) between January 2020 and August 2022 in Denmark. We calculated the risk of long COVID diagnosis and long COVID symptoms among ethnic minorities compared with native Danes using multivariable Cox proportional hazard regression and logistic regression, respectively. Among individuals who were first time diagnosed with COVID-19 during the study period, 39,876 (1.7%) were hospitalised and 2,247,299 (98.3%) were nonhospitalised individuals. Of the diagnosed COVID-19 cases, 1,952,021 (85.3%) were native Danes and 335,154 (14.7%) were ethnic minorities. After adjustment for age, sex, civil status, education, family income, and Charlson comorbidity index, ethnic minorities from North Africa (adjusted hazard ratio [aHR] 1.41, 95% confidence interval [CI] [1.12,1.79], p = 0.003), Middle East (aHR 1.38, 95% CI [1.24,1.55], p < 0.001), Eastern Europe (aHR 1.35, 95% CI [1.22,1.49], p < 0.001), and Asia (aHR 1.23, 95% CI [1.09,1.40], p = 0.001) had significantly greater risk of long COVID diagnosis than native Danes. In the analysis by largest countries of origin, the greater risks of long COVID diagnosis were found in people of Iraqi origin (aHR 1.56, 95% CI [1.30,1.88], p < 0.001), people of Turkish origin (aHR 1.42, 95% CI [1.24,1.63], p < 0.001), and people of Somali origin (aHR 1.42, 95% CI [1.07,1.91], p = 0.016). A significant factor associated with an increased risk of long COVID diagnosis was COVID-19 hospitalisation. The risk of long COVID diagnosis among ethnic minorities was more pronounced between January 2020 and June 2021. Furthermore, the odds of reporting cardiopulmonary symptoms (including dyspnoea, cough, and chest pain) and any long COVID symptoms were higher among people of North African, Middle Eastern, Eastern European, and Asian origins than among native Danes in both unadjusted and adjusted models. Despite including the nationwide sample of individuals diagnosed with COVID-19, the precision of our estimates on long COVID was limited to the sample of patients with symptoms who had contacted the hospital.

CONCLUSIONS

Belonging to an ethnic minority group was significantly associated with an increased risk of long COVID, indicating the need to better understand long COVID drivers and address care and treatment strategies in these populations.

Early Life Factors and Polycystic Ovary Syndrome in a Swedish Birth Cohort

Polycystic ovary syndrome (PCOS) is a medical condition with important consequences for women's well-being and reproductive outcomes. Although the etiology of PCOS is not fully understood, there is increasing evidence of both genetic and environmental determinants, including development in early life. We studied a population of 977,637 singleton women born in in Sweden between 1973 and 1995, followed sometime between the age 15 and 40. The incidence of PCOS was measured using hospital register data during 2001-2012, complemented with information about the women's, parents' and sisters' health and social characteristics from population and health care registers. Cox regression was used to study how PCOS is associated with intergenerational factors, and a range of early life characteristics. 11,594 women in the study sample were diagnosed with PCOS during the follow-up period. The hazard rate for PCOS was increased 3-fold (HR 2.98, 95% CI 2.43-3.64) if the index woman's mother had been diagnosed with PCOS, and with 1.5-fold (HR 1.51, 95% CI 1.39-1.63) if their mother had diabetes mellitus. We found associations of PCOS with lower (<7) one-minute Apgar score (HR 1.19, 95% CI 1.09-1.29) and with post-term birth (HR 1.19, 95% CI 1.13-1.26). Furthermore, heavy (10+ cigarettes/day) maternal smoking (HR 1.30, 95% CI 1.18-1.44) and maternal obesity (HR 1.90, 95% CI 1.62-2.36) were strongly associated with PCOS. This study finds support for the heritability and fetal origins of PCOS. Risk of PCOS could be reduced by further emphasizing the importance of maternal and early life health.

Migrant mortality by duration of residence and co-ethnic density - A register-based study on Finnish migrants in Sweden with matched controls in the origin and the destination

Migrant health depends on factors both at the origin and at the destination. Health-related behaviors established before migration may change at the destination. We compare the mortality rates from alcohol- and smoking-related causes and cardiovascular diseases (CVD) of Finnish migrants in Sweden to matched controls in both Sweden and Finland with similar sociodemographic characteristics. Migrant mortality rates from behavioral risk factors lie in-between the rates of non-migrants in the origin and destination. A longer duration of residence is associated with lower mortality and with mortality patterns more similar to Swedes for men. For women, a longer duration of residence is associated with higher mortality, in particular smoking-related mortality, with no tendency of a gradual convergence. The density of Finnish migrants in the local area is modestly associated with mortality. However, CVD mortality tends to be higher and more similar to the level in Finland for migrants in areas with a higher density of Finnish migrants. The results suggest that behavioral changes can reduce mortality differences between migrants and natives and that this can be either beneficial or detrimental to migrant health.

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.

Waves of inequality: income differences in intensive care due to Covid-19 in Sweden

BACKGROUND

Socioeconomically vulnerable groups were overall more likely to develop severe Covid-19, but specific conditions in terms of preparedness, knowledge and the properties of the virus itself changed during the course of the pandemic. Inequalities in Covid-19 may therefore shift over time. This study examines the relationship between income and intensive care (ICU) episodes due to Covid-19 in Sweden during three distinct waves.

METHODS

This study uses Swedish register data on the total adult population and estimates the relative risk (RR) of ICU episodes due to Covid-19 by income quartile for each month between March 2020 and May 2022, and for each wave, using Poisson regression analyses.

RESULTS

The first wave had modest income-related inequalities, while the second wave had a clear income gradient, with the lowest income quartile having an increased risk compared to the high-income group [RR: 1.55 (1.36-1.77)]. In the third wave, the overall need for ICU decreased, but RRs increased, particularly in the lowest income quartile [RR: 3.72 (3.50-3.96)]. Inequalities in the third wave were partly explained by differential vaccination coverage by income quartile, although substantial inequalities remained after adjustment for vaccination status [RR: 2.39 (2.20-2.59)].

CONCLUSIONS

The study highlights the importance of considering the changing mechanisms that connect income and health during a novel pandemic. The finding that health inequalities increased as the aetiology of Covid-19 became better understood could be interpreted through the lens of adapted fundamental cause theory.

Birth Outcomes Following Assisted Reproductive Technology Conception Among Same-Sex Lesbian Couples vs Natural Conception and Assisted Reproductive Technology Conception Among Heterosexual Couples

This study uses registry data to compare birth outcomes, including birth weight, gestational age, low birth weight, and preterm delivery, in assisted reproductive technology (ART) pregnancies among same-sex lesbian couples vs natural conceptions and ART pregnancies among heterosexual couples.

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.

Investigating the salmon bias effect among international immigrants in Sweden: a register-based open cohort study

Background

Studies of migration and health have hypothesized that immigrants may emigrate when they develop poor health (salmon bias effect), which may partially explain the mortality advantage observed among immigrants in high-income countries. We evaluated the salmon bias effect by comparing the health of immigrants in Sweden who emigrated with those who remained, while also exploring potential variation by macro-economic conditions, duration of residence and region of origin.

Methods

A longitudinal, open cohort study design was used to assess risk of emigration between 1992 and 2016 among all adult (18+ years) foreign-born persons who immigrated to Sweden between 1965 and 2012 (n = 1 765 459). The Charlson Comorbidity Index was used to measure health status, using information on hospitalizations from the Swedish National Patient Register. Poisson regression models were used to estimate incidence rate ratios (RRs) with 95% confidence intervals (CIs) for emigrating from Sweden.

Results

Immigrants with low (RR = 0.83; 95% CI: 0.76–0.90) moderate (RR = 0.70; 95% CI: 0.62–0.80) and high (RR = 0.62; 95% CI: 0.48–0.82) levels of comorbidities had decreased risk of emigration relative to those with no comorbidities. There was no evidence of variation by health status in emigration during periods of economic recession or by duration of residence. Individuals with low to moderate levels of comorbidities from some regions of origin had an increased risk of emigration relative to those with no comorbidities.

Conclusions

The study results do not support the existence of a salmon bias effect as a universal phenomenon among international immigrants in Sweden.

Disparities in Coronavirus Disease 2019 Mortality by Country of Birth in Stockholm, Sweden: A Total-Population-Based Cohort Study

Preliminary evidence points to higher morbidity and mortality from coronavirus disease 2019 (COVID-19) in certain racial and ethnic groups, but population-based studies using microlevel data are lacking so far. We used register-based cohort data including all adults living in Stockholm, Sweden, between January 31, 2020 (the date of the first confirmed case of COVID-19) and May 4, 2020 (n = 1,778,670) to conduct Poisson regression analyses with region/country of birth as the exposure and underlying cause of COVID-19 death as the outcome, estimating relative risks and 95% confidence intervals. Migrants from Middle Eastern countries (relative risk (RR) = 3.2, 95% confidence interval (CI): 2.6, 3.8), Africa (RR = 3.0, 95% CI: 2.2, 4.3), and non-Sweden Nordic countries (RR = 1.5, 95% CI: 1.2, 1.8) had higher mortality from COVID-19 than persons born in Sweden. Especially high mortality risks from COVID-19 were found among persons born in Somalia, Lebanon, Syria, Turkey, Iran, and Iraq. Socioeconomic status, number of working-age household members, and neighborhood population density attenuated up to half of the increased COVID-19 mortality risks among the foreign-born. Disadvantaged socioeconomic and living conditions may increase infection rates in migrants and contribute to their higher risk of COVID-19 mortality.

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.

Young people's labour market patterns and later mental health: A sequence analysis exploring the role of region of origin for young people's labour market trajectories and mental health

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Experiencing early employment disadvantage could lead to long-term labour market instability and labour market exclusion.

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Migrants showed more turbulent transitions between labour market states than natives.

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Belonging to a turbulent labour market trajectory is association with poor mental ill health in mid-life.

Rural life and suicide: Does the effect of the community context vary by country of birth? A Swedish registry-based multilevel cohort study

Contextual factors varying by residence in rural or urban areas may have different effects on the suicide of residents by nativity, but evidence on the urban-rural gap in suicide according to nativity is lacking. This study aims to evaluate the effect of cross-level interaction between nativity and rurality of residence on suicide risk, at two levels of aggregation (municipalities/neighborhoods). Study design was nationwide register-based cohort study in Sweden, 2011-2016. Participants were all residents 20 years or older. We calculated Incidence Rate Ratios comparing suicide incidence by nativity using three-level (individuals, neighborhoods, and municipalities) Poisson regression, stratified by gender. Among men, suicide incidences were the highest among those born in other Nordic countries, followed by those born in Sweden, other European countries, Middle Eastern countries, and the rest of the world. Residing in rural areas was associated with high IRR of suicide regardless of nativity, compared to residing in urban areas. When evaluating rurality at municipality level, we observed an increased suicide risk from living in rural areas in men born in other European (rural-urban ratio of nativity-specific IRRs: 1.39) and other Nordic (1.37) countries, followed by native Swedes (1.22). When evaluating rurality at neighborhood level, rurality was associated with increased suicide risk in men for all nativities, with the foreign-born showing higher risk than the Swedish-born. Individual sociodemographic characteristics explained the excess suicide risk in rural municipalities, but not the excess risk in rural neighborhoods. Among women, urban residents showed higher suicide incidence than rural residents. We found no consistent patterning of interaction with nativities among women. Foreign-born individuals residing in rural municipalities may have less access to economic resources and employment opportunities. Furthermore, ethnic discrimination, stigma, and exclusion from social networks and community may be more common in rural neighborhood contexts, leading to an increased risk of suicide.

Age at Immigration, Generational Status, and Death Among Children of Immigrant Mothers: A Longitudinal Analysis of Siblings

Studies have documented that age at immigration and generational status are important predictors of socioeconomic outcomes among children of immigrants. Whether these characteristics are related to long-term risk of death is unknown. Leveraging variation within sibships, we evaluated the association of age at immigration and generational status (i.e., first or second generation) with death among children of immigrant mothers to Sweden. Data included 272,429 individuals (126,701 sibships) aged 15 or more years from the total Swedish population followed between 1990 and 2009. Population-average and sibling fixed-effect regressions were estimated, with the latter controlling for unobserved factors shared by siblings. The foreign-born children of immigrants experienced a 17% higher risk of death than the Swedish-born children of immigrants. This excess risk was evident for external and nonexternal causes of death. In general, a graded association was not detected between age at immigration and death among the foreign-born individuals; however, those arriving during primary school ages appeared especially vulnerable. This study provides robust evidence that among children of immigrants, being foreign born was associated with a long-term death penalty compared with being born in the host country.

Birth order and mortality in two ethno-linguistic groups: Register-based evidence from Finland

Previous research has documented an association between birth order and suicide, although no study has examined whether it depends on the cultural context. Our aim was to study the association between birth order and cause-specific mortality in Finland, and whether it varies by ethno-linguistic affiliation. We used data from the Finnish population register, representing a 5% random sample of all Finnish speakers and a 20% random sample of Swedish speakers, who lived in Finland in any year 1987-2011. For each person, there was a link to all children who were alive in 1987. In total, there were 254,059 siblings in 96,387 sibling groups, and 9797 deaths. We used Cox regressions stratified by each siblings group and estimated all-cause and cause-specific mortality risks during the period 1987-2011. In line with previous research from Sweden, deaths from suicide were significantly associated with birth order. As compared to first-born, second-born had a suicide risk of 1.27, third-born of 1.35, and fourth- or higher-born of 1.72, while other causes of death did not display an evident and consistent birth-order pattern. Results for the Finnish-speaking siblings groups were almost identical to those based on both ethno-linguistic groups. In the Swedish-speaking siblings groups, there was no increase in the suicide risk by birth order, but a statistically not significant tendency towards an association with other external causes of death and deaths from cardiovascular diseases. Our findings provided evidence for an association between birth order and suicide among Finnish speakers in Finland, while no such association was found for Swedish speakers, suggesting that the birth order effect might depend on the cultural context.

A nationwide cohort study of mortality risk and long-term prognosis in infective endocarditis in Sweden

OBJECTIVES

Infective endocarditis (IE) remains a serious disease with substantial mortality. In this study we investigated the incidence of IE, as well as its associated short and long term mortality rates.

METHODS

The IE cases were identified in the Swedish national inpatient register using ICD-10 codes, and then linked to the population register in order to identify deaths in the cohort. Crude mortality rates among IE patients were obtained for different time intervals. These rates were directly standardized using sex- and age-matched mortality in the general population.

RESULTS

The cohort consisted of 7603 individuals and 7817 episodes of IE during 1997-2007. The 30 days all-cause crude mortality rate was 10.4% and the standardized mortality ratio (SMR) was 33.7 (95% confidence interval [CI]: 31.0-36.6). Excluding the first year of follow-up, the long term mortality (1-5 years) showed an increased SMR of 2.2 (95% CI: 2.0-2.3) compared to the general population. Significantly higher SMR was found for cases of IE younger than 65 years of age with a 1-5 year SMR of 6.3, and intravenous drug-users with a SMR of 19.1. Native valve IE cases, in which surgery was performed had lower crude mortality rates and Mantel-Haenzel odds ratios of less than one compared to those with medical therapy alone during 30-day and 5-years follow-up.

CONCLUSIONS

The 30-days crude mortality rate for IE was 10.4% and long-term relative mortality risk remains increased even up to 5 years of follow-up, therefore a close monitoring of these patients would be of value.