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BackgroundMost medical educational programs emphasize clinical observation or clinical skill acquisition, fewer focus upon research. The Danish-American Research Exchange (DARE) program, sponsored by the Lundbeck Foundation, is unique in that the medical student initiates biomedical research collaboration between Danish and US medical institutions. To achieve this, Danish medical students (DARE students) conduct binational mentored research projects while based in the United States for 10 months. In addition, DARE students are introduced to interdisciplinary thinking about how to develop ultra-low-cost healthcare interventions through the '$10 Challenge'.MethodsWe conducted a cross-sectional study of DARE alumni over five consecutive years (2015-2020, n = 24). Research metrics included completion of a research project, primary authorship, and co-authorship of publications. The number of publications, prior to and after the DARE program were enumerated. For the first four cohorts, graduation from medical school and acceptance or intention to enter a joint MD-PhD program also were assessed. Two focus groups were conducted using constructivist grounded theory. Discussions were transcribed, redacted, and coded using Dedoose software.ResultsDARE Medical students were 31.2 years (range 24-35), the majority were women (67%;16/24). The majority (17/24;71%) completed a first author publication in a peer-reviewed journal with a median of 3.9 per DARE alumnus. DARE alumnus reported increased proficiency in biostatistics, epidemiology, coding and public speaking as well as stronger research qualities in creativity, critical thinking, comfort in approaching scientist in both the US and Denmark (p

ObjectiveTo evaluate associations between gestational diabetes mellitus (GDM) and various incident cardiovascular disease (CVD) end points, considering the effects of the mediating role of type 2 diabetes and shared environmental/familial factors.Research design and methodsThis population-based cohort study included 10,02,486 parous women in Denmark during 1978-2016. We used Cox regression to 1) examine the associations of GDM with overall and type-specific CVDs using full-cohort and sibling-matched analysis, 2) quantify the impact of type 2 diabetes after GDM using mediation analysis, and 3) assess whether these associations were modified by prepregnancy obesity or maternal history of CVD.ResultsWomen with a history of GDM had a 40% increased overall CVD risk (hazard ratio [HR] 1.40, 95% CI 1.35-1.45). Sibling-matched analyses yielded similar results (HR 1.44, 95% CI 1.28-1.62). The proportion of association between GDM and overall CVD explained by subsequent type 2 diabetes was 23.3% (15.4-32.8%). We observed increased risks of specific CVDs, including 65% increased stroke risk and more than twofold risks for myocardial infarction, heart failure, and peripheral artery disease. The elevated overall risks were more pronounced among women with GDM and prepregnancy obesity or maternal history of CVD.ConclusionsA history of GDM was associated with increased risks of overall and specific CVDs. Increased risks were partly explained by subsequent type 2 diabetes, and the need to identify other pathways remains important. Continuous monitoring of women with a history of GDM, especially those with prepregnancy obesity or maternal history of CVD, may provide better opportunities to reduce their cardiovascular risk.

Author(s): Cecilia Hvitfeldt Fuglsang, Lars Pedersen, Morten Schmidt, Jan P. Vandenbroucke, Hans Erik Bøtker, Henrik Toft Sørensen The first author's name is indexed incorrectly. The correct citation is: Fuglsang CH, [...]

BackgroundPosttraumatic stress disorder is a well-documented risk factor for cardiovascular disease. Whether non-specific stress-related psychopathology also increases risk is less well known.MethodsIn a cohort of adult Danish-born residents of Denmark with an incident diagnosis of unspecified reaction to severe stress ("unspecified stress reaction") between 1995 and 2011 (N = 24,534), we assessed incidence of seven arterial and venous cardiovascular events/conditions between 1996 and 2013. We calculated standardized incidence ratios (SIRs) comparing incidence of each outcome among the cohort to expected incidence based on sex-, age-, and calendar-time-specific national rates. We conducted stratified analyses by demographic characteristics, comorbidities, and length of follow-up time.ResultsIncidence over the study period ranged from 1.1% for provoked VTE to 5.7% for stroke, adjusting for competing risk of death. Unspecified stress reaction was associated with all outcomes (SIRs ranging from 1.3, 95% confidence interval (CI): 1.1-1.4 for atrial fibrillation/flutter to 1.9, 95% CI: 1.7-2.2 for unprovoked VTE and 1.9, 95% CI: 1.6-2.3 for provoked VTE). Associations persisted, but were attenuated, when restricting to persons without alcohol use disorder and to persons without physical health comorbidities.LimitationsUnspecified stress reaction has less precise criteria than other stress-related diagnoses, and we could not adjust for some potential confounders.ConclusionsOur results augment literature on stress disorders and cardiovascular disease by highlighting the additional importance of unspecified stress disorders. Further research on this diagnostic category, which may represent subsyndromal psychopathology, is warranted. These findings support considering persons with non-specific stress-related psychopathology in treatment and tertiary prevention activities.

ObjectiveThis population-based, matched cohort study aimed to evaluate utilization of health care services by mothers of children with major congenital anomalies (MCAs), compared to mothers of children without MCAs over a 20-year post-birth time horizon in Denmark.MethodsOur analytic sample included mothers who gave birth to an infant with a MCA (n = 23,927) and a cohort of mothers matched to them by maternal age, parity and infant's year of birth (n = 239,076). Primary outcomes were period prevalence and mothers' quantity of health care utilization (primary, inpatient, outpatient, surgical, and psychiatric services) stratified by their child's age (i.e., ages 0-6 = before school, ages 7-13 = pre-school + primary education, and ages 14-18 = secondary education or higher). The secondary outcome measure was length of hospital stays. Outcome measures were adjusted for maternal age at delivery, parity, marital status, income quartile, level of education in the year prior to the index birth, previous spontaneous abortions, maternal pregnancy complications, maternal diabetes, hypertension, alcohol-related diseases, and maternal smoking.ResultsIn both cohorts the majority of mothers were between 26 and 35 years of age, married, and employed, and 47% were primiparous. Mothers of infants with anomalies had greater utilization of outpatient, inpatient, surgical, and psychiatric services, compared with mothers in the matched cohort. Inpatient service utilization was greater in the exposed cohort up to 13 years after a child's birth, with the highest risk in the first six years after birth [adjusted risk ratio, 1.13; 95% confidence interval (CI), 1.12-1.14], with a decrease over time. Regarding the quantity of health care utilization, the greatest difference between the two groups was in inpatient service utilization, with a 39% increased rate in the exposed cohort during the first six years after birth (adjusted rate ratio, 1.39; 95% CI, 1.37-1.42). During the first 6 years after birth, mothers of children with anomalies stayed a median of 6 days (interquartile range [IQR], 3-13) in hospital overall, while the comparison cohort stayed a median of 4 days (IQR, 2-7) in hospital overall. Rates of utilization of outpatient clinics (adjusted rate ratio, 1.36; 95% CI, 1.29-1.42), as well as inpatient (adjusted rate ratio, 1.77; 95% CI, 1.68-1.87), and surgical services (adjusted rate ratio, 1.33; 95% CI, 1.26-1.41) was higher in mothers of children with multiple-organ MCAs during 0 to 6 years after birth. Among mothers at the lowest income levels, utilization of psychiatric clinic services increased to 59% and when their child was 7 to 13 years of age (adjusted rate ratio, 1.59; 95% CI, 1.24-2.03).ConclusionMothers of infants with a major congenital anomaly had greater health care utilization across services. Health care utilization decreased over time or remained stable for outpatient, inpatient, and surgical care services, whereas psychiatric utilization increased for up to 13 years after an affected child's birth. Healthcare utilization was significantly elevated among mothers of children with multiple MCAs and among those at the lowest income levels.

Background The association between assisted reproductive technologies (ARTs) and the body mass index (BMI) of children remains controversial. Confounding by morbidity and other factors associated with parental infertility may have biased studies comparing children born after ART with children born after no treatment. We investigated the associations between different fertility treatments and BMI in children at age 5 to 8 years, adjusting for and stratifying by causes of parental infertility. Methods and findings This Danish cohort study included 327,301 children born between 2007 and 2012 (51% males, median age at follow-up 7 years). Of these, 13,675 were born after ART, 7,728 were born after ovulation induction with or without intrauterine insemination [OI/IUI], and 305,898 were born after no fertility treatments. Using the International Obesity Task Force (IOTF) standards, we defined overweight (BMI [greater than or equal to] IOTF-25) and obesity (BMI [greater than or equal to] IOTF-30). We compared children born after ART versus OI/IUI; intracytoplasmic sperm injection (ICSI) versus conventional in vitro fertilization (IVF); and frozen-thawed versus fresh embryo transfer and estimated crude and adjusted prevalences of children with overweight or obesity at age 5 to 8 years, prevalence odds ratios (PORs), and differences in mean BMI z-scores. Adjustment was performed using stabilized inverse probability of treatment weights, including parity, year of conception, parental causes of infertility, age, educational level, comorbidities, maternal country of origin, BMI, and smoking as covariates. The crude prevalence of obesity was 1.9% in children born after ART, 2.0% in those born after OI/IUI, and 2.7% in those born after no fertility treatment. After adjustment, children born after ART and OI/IUI had the same prevalence of being overweight (11%; POR 1.00, 95% confidence interval [CI] 0.91 to 1.11; p = 0.95) or obese (1.9%; POR 1.01, 95% CI 0.79 to 1.29; p = 0.94). Comparison of ICSI with conventional IVF yielded similar pattern (POR 0.95, 95% CI 0.83 to 1.07; p = 0.39 for overweight and POR 1.16, 95% CI 0.84 to 1.61; p = 0.36 for obesity). Obesity was more prevalent after frozen-thawed (2.7%) than fresh embryo transfer (1.8%) (POR 1.54, 95% CI 1.09 to 2.17; p = 0.01). The associations between fertility treatments and BMI were only modestly different in subgroups defined by the cause of infertility. Study limitations include potential residual confounding, restriction to live births, and lack of detailed technical information about the IVF procedures. Conclusions We found no association with BMI at age 5 to 8 years when comparing ART versus OI/IUI or when comparing ICSI versus conventional IVF. However, use of frozen-thawed embryo transfer was associated with a 1.5-fold increased risk of obesity compared to fresh embryo transfer. Despite an elevated relative risk, the absolute risk difference was low., Author(s): Kristina Laugesen 1,*, Katalin Veres 1, Sonia Hernandez-Diaz 2, Yu-Han Chiu 2,3, Anna Sara Oberg 2,4, John Hsu 5,6,7, Paolo Rinaudo 8, Mandy Spaan 9, Flora van Leeuwen 9, [...]

OBJECTIVE:There is some evidence that posttraumatic stress disorder (PTSD) is associated with increased risk of infections, and it is unknown whether adjustment disorder is as well. We assessed the association between adjustment disorder and subsequent infections, and assessed additive interaction with sex. METHODS:The study population included a nationwide cohort of all Danish-born residents of Denmark diagnosed with adjustment disorder between 1995 and 2011, and an age- and sex-matched general population comparison cohort. We compared rates of infections requiring inpatient or outpatient hospitalization in the two cohorts. We fit Cox proportional hazards models to compute adjusted hazard ratios (aHR) for the associations between adjustment disorder and 32 types of infections, and calculated interaction contrasts to assess interaction between adjustment disorder and sex. RESULTS:Adjustment disorder was associated with increased rates of infections overall (n = 19,838 infections, aHR = 1.8, 95% confidence interval = 1.8. 1.9), and increased rates of each individual infection type (aHRs for 30 infections ranged from 1.5 to 2.3), adjusting for baseline psychiatric and somatic comorbidities and marital status. For many infection types (e.g., skin infections, pneumonia), interaction contrasts indicated rate differences were greater among men than women, while for two (urinary tract infections and sexually transmitted infections), rate differences were greater for women. CONCLUSIONS:These findings are consistent with studies examining the relationship between psychological stress and infections, and between PTSD and infections. They may be explained by a combination of the triggering of unhealthy behaviors as well as immune responses to stress.

OBJECTIVE:To evaluate the associations between maternal diabetes diagnosed before or during pregnancy and early onset cardiovascular disease (CVD) in offspring during their first four decades of life. DESIGN:Population based cohort study. SETTING:Danish national health registries. PARTICIPANTS:All 2 432 000 liveborn children without congenital heart disease in Denmark during 1977-2016. Follow-up began at birth and continued until first time diagnosis of CVD, death, emigration, or 31 December 2016, whichever came first. EXPOSURES FOR OBSERVATIONAL STUDIES:Pregestational diabetes, including type 1 diabetes (n=22 055) and type 2 diabetes (n=6537), and gestational diabetes (n=26 272). MAIN OUTCOME MEASURES:The primary outcome was early onset CVD (excluding congenital heart diseases) defined by hospital diagnosis. Associations between maternal diabetes and risks of early onset CVD in offspring were studied. Cox regression was used to assess whether a maternal history of CVD or maternal diabetic complications affected these associations. Adjustments were made for calendar year, sex, singleton status, maternal factors (parity, age, smoking, education, cohabitation, residence at childbirth, history of CVD before childbirth), and paternal history of CVD before childbirth. The cumulative incidence was averaged across all individuals, and factors were adjusted while treating deaths from causes other than CVD as competing events. RESULTS:During up to 40 years of follow-up, 1153 offspring of mothers with diabetes and 91 311 offspring of mothers who did not have diabetes were diagnosed with CVD. Offspring of mothers with diabetes had a 29% increased overall rate of early onset CVD (hazard ratio 1.29 (95% confidence interval 1.21 to 1.37); cumulative incidence among offspring unexposed to maternal diabetes at 40 years of age 13.07% (12.92% to 13.21%), difference in cumulative incidence between exposed and unexposed offspring 4.72% (2.37% to 7.06%)). The sibship design yielded results similar to those of the unpaired design based on the whole cohort. Both pregestational diabetes (1.34 (1.25 to 1.43)) and gestational diabetes (1.19 (1.07 to 1.32)) were associated with increased rates of CVD in offspring. We also observed varied increased rates of specific early onset CVDs, particularly heart failure (1.45 (0.89 to 2.35)), hypertensive disease (1.78 (1.50 to 2.11)), deep vein thrombosis (1.82 (1.38 to 2.41)), and pulmonary embolism (1.91 (1.31 to 2.80)). Increased rates of CVD were seen in different age groups from childhood to early adulthood until age 40 years. The increased rates were more pronounced among offspring of mothers with diabetic complications (1.60 (1.25 to 2.05)). A higher incidence of early onset CVD in offspring of mothers with diabetes and comorbid CVD (1.73 (1.36 to 2.20)) was associated with the added influence of comorbid CVD but not due to the interaction between diabetes and CVD on the multiplicative scale (P value for interaction 0.94). CONCLUSIONS:Children of mothers with diabetes, especially those mothers with a history of CVD or diabetic complications, have increased rates of early onset CVD from childhood to early adulthood. If maternal diabetes does have a causal association with increased CVD rate in offspring, the prevention, screening, and treatment of diabetes in women of childbearing age could help to reduce the risk of CVD in the next generation.

Purpose: Breast cancer has an average 10-year relative survival reaching 84%. This favorable survival is due, in part, to the introduction of biomarker-guided therapies. We estimated the population-level effect of the introduction of two adjuvant therapies--tamoxifen and trastuzumab--on recurrence using the trend-in-trend pharmacoepidemiologic study design. Methods: We ascertained data on women diagnosed with nonmetastatic breast cancer who were registered in the Danish Breast Cancer Group clinical database. We used the trend-in-trend design to estimate the population-level effect of the introduction of (1) tamoxifen for postmenopausal women with estrogen receptor (ER)-positive breast cancer in 1982, (2) tamoxifen for premenopausal women diagnosed with ER-positive breast cancer in 1999, and (3) trastuzumab for women <60 years diagnosed with human epidermal growth factor receptor 2-positive breast cancer in 2007. Results: For the population-level effect of the introduction of tamoxifen among premenopausal women diagnosed with ER-positive breast cancer in 1999, the risk of recurrence decreased by nearly one-half (OR = 0.52), consistent with evidence from clinical trials; however, the estimate was imprecise (95% confidence interval [CI] = 0.25, 1.85). We observed an imprecise association between tamoxifen use and recurrence from the time it was introduced in 1982 (OR = 1.24 95% CI = 0.46, 5.11), inconsistent with prior knowledge from clinical trials. For the introduction of trastuzumab in 2007, the estimate was also consistent with trial evidence, though imprecise (OR = 0.51; 95% CI = 0.21, 22.4). Conclusions: We demonstrated how novel pharmacoepidemiologic analytic designs can be used to evaluate the routine clinical care and effectiveness of therapeutic advancements in a population-based setting while considering some limitations of the approach. [ABSTRACT FROM AUTHOR]

Background: Observational studies of SARS-CoV-2 vaccine effectiveness are prone to confounding, which can be illustrated using negative control methods. Methods: Nationwide population-based cohort study including two cohorts of Danish residents 60– 90 years of age matched 1:1 on age and sex: A vaccinated and a non-vaccinated cohort, including 61052 SARS-CoV-2 vaccinated individuals between 1 March and 1 July 2021 and 61052 individuals not vaccinated preceding 1 July 2021. From these two cohorts, we constructed negative control cohorts of individuals diagnosed with SARS-CoV-2 infection or acute myocardial infarction, stroke, cancer, low energy fracture, or head-trauma. Outcomes were SARS-CoV-2 infection, negative control outcomes (eg, mammography, prostate biopsy, operation for cataract, malignant melanoma, examination of eye and ear), and death. We used Cox regression to calculate adjusted incidence and mortality rate ratios (aIRR and aMRR). Results: Risks of SARS-CoV2 infection and all negative control outcomes were elevated in the vaccinated population, ranging from an aIRR of 1.15 (95% CI: 1.09– 1.21) for eye examinations to 3.05 (95% CI: 2.24– 4.14) for malignant melanoma. Conversely, the risk of death in the SARS-CoV-2 infected cohort and in all negative control cohorts was lower in vaccinated individuals, ranging from an aMRR of 0.23 (95% CI: 0.19– 0.26) after SARS-CoV-2 infection to 0.50 (95% CI: 0.37– 0.67) after stroke. Conclusion: Our findings indicate that observational studies of SARS-CoV-2 vaccine effectiveness may be subject to substantial confounding. Therefore, randomized trials are essential to establish vaccine efficacy after the emergence of new SARS-CoV-2 variants and the rollout of multiple booster vaccines. Plain Language Summary: Why was this study done : After the emergence of new SARS-CoV-2 variants and the rollout of multiple booster SARS-CoV-2 vaccines, the impact of vaccination on risk of SARS-CoV-2 infection and death after the infection has mainly been explored in observational studies. We used negative control methods to investigate whether confounding affects the results of observational SARS-CoV-2 vaccine effectiveness studies. Findings : We used Danish registry data obtained during the SARS-CoV-2 vaccine roll-out to conduct a nationwide, matched population-based cohort study of Danish residents 60– 90 years in which we compared vaccinated individuals with non-vaccinated individuals. Compared with unvaccinated individuals, vaccinated individuals had increased risks of SARS-CoV2 infection but also had increased risks of all negative control outcomes (mammography, prostate biopsy, operation for cataract, malignant melanoma, examination of eye and ear). The risk of death after SARS-CoV2 infection was lower in the vaccinated cohort, as was the risk of death after acute myocardial infarction, stroke, cancer, low energy fracture, and head-trauma. Meaning : The negative control methods indicate that observational studies of SARS-CoV-2 vaccine effectiveness may be prone to substantial confounding which may impact the observed associations. This bias may both lead to underestimation of vaccine effectiveness (increased risk of SARS-CoV2 infection among vaccinated individuals) and overestimation of the vaccine effectiveness (decreased risk of death after of SARS-CoV2 infection among vaccinated individuals). Our results highlight the need for randomized vaccine efficacy studies after the emergence of new SARS-CoV-2 variants and the rollout of multiple booster vaccines. [ABSTRACT FROM AUTHOR]

Background Migraine carries risk of myocardial infarction (MI) and stroke. The risk of premature MI (i.e., among young adults) and stroke differs between men and women; previous studies indicate that migraine is mainly associated with an increased risk of stroke among young women. The aim of this study was to examine impact of migraine on the risk of premature (age [less than or equal to]60 years) MI and ischemic/hemorrhagic stroke among men and women. Methods and findings Using Danish medical registries, we conducted a nationwide population-based cohort study (1996 to 2018). Redeemed prescriptions for migraine-specific medication were used to identify women with migraine (n = 179,680) and men with migraine (n = 40,757). These individuals were matched on sex, index year, and birth year 1:5 with a random sample of the general population who did not use migraine-specific medication. All individuals were required to be between 18 and 60 years old. Median age was 41.5 years for women and 40.3 years for men. The main outcome measures to assess impact of migraine were absolute risk differences (RDs) and hazard ratios (HRs) with 95% confidence intervals (CIs) of premature MI, ischemic, and hemorrhagic stroke, comparing individuals with migraine to migraine-free individuals of the same sex. HRs were adjusted for age, index year, and comorbidities. The RD of premature MI for those with migraine versus no migraine was 0.3% (95% CI [0.2%, 0.4%]; p < 0.001) for women and 0.3% (95% CI [-0.1%, 0.6%]; p = 0.061) for men. The adjusted HR was 1.22 (95% CI [1.14, 1.31]; p < 0.001) for women and 1.07 (95% CI [0.97, 1.17]; p = 0.164) for men. The RD of premature ischemic stroke for migraine versus no migraine was 0.3% (95% CI [0.2%, 0.4%]; p < 0.001) for women and 0.5% (95% CI [0.1%, 0.8%]; p < 0.001) for men. The adjusted HR was 1.21 (95% CI [1.13, 1.30]; p < 0.001) for women and 1.23 (95% CI [1.10, 1.38]; p < 0.001) for men. The RD of premature hemorrhagic stroke for migraine versus no migraine was 0.1% (95% CI [0.0%, 0.2%]; p = 0.011) for women and -0.1% (95% CI [-0.3%, 0.0%]; p = 0.176) for men. The adjusted HR was 1.13 (95% CI [1.02, 1.24]; p = 0.014) for women and 0.85 (95% CI [0.69, 1.05]; p = 0.131) for men. The main limitation of this study was the risk of misclassification of migraine, which could lead to underestimation of the impact of migraine on each outcome. Conclusions In this study, we observed that migraine was associated with similarly increased risk of premature ischemic stroke among men and women. For premature MI and hemorrhagic stroke, there may be an increased risk associated with migraine only among women., Author(s): Cecilia Hvitfeldt Fuglsang 1,*, Lars Pedersen 1, Morten Schmidt 1,2, Jan P. Vandenbroucke 1,3,4, Hans Erik Bøtker 2,5, Henrik Toft Sørensen 1 Introduction Migraine is a common headache disorder [...]

Social isolation is associated with increased mortality. Meta-analytic results, however, indicate heterogeneity in effect sizes. We aimed to provide new evidence to the association between social isolation and mortality by conducting a population-based cohort study. We reconstructed the Berkman and Syme's social network index (SNI), which combines four components of social networks (partnership, interaction with family/friends, religious activities, and membership in organizations/clubs) into an index, ranging from 0/1 (most socially isolated) to 4 (least socially isolated). We estimated cumulative mortality and adjusted mortality rate ratios (MRR) associated with SNI. We adjusted for potential important confounders, including psychiatric and somatic status, lifestyle, and socioeconomic status. Cumulative 7-year mortality in men was 11% for SNI 0/1 and 5.4% for SNI 4 and in women 9.6% for SNI 0/1 and 3.9% for SNI 4. Adjusted MRRs comparing SNI 0/1 with SNI 4 were 1.7 (95% CI: 1.1-2.6) among men and 1.6 (95% CI: 0.83-2.9) among women. Having no partner was associated with an adjusted MRR of 1.5 (95% CI: 1.2-2.1) for men and 1.7 (95% CI: 1.2-2.4) for women. In conclusion, social isolation was associated with 60-70% increased mortality. Having no partner was associated with highest MRR.

Rebecca Troisi, Ingrid Glimelius, Tom Grotmol, Mika Gissler, Cari M. Kitahara, Anne Gulbech Ording, Solbjørg Makalani Myrtveit Sæther, Camilla Sköld, Henrik Toft Sørensen, Britton Trabert and Tone Bjørge: The role of pregnancy in maternal cancer risk: Epidemiologic evidence from the Nordic Countries Linked Birth and Cancer Registries Cohort Project