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Preeclampsia and cardiovascular disease (CVD) might share heritable underlying mechanisms. We investigated whether preeclampsia in daughters is associated with CVD in parents. In a register-based cohort study, we used Cox regression to compare rates of CVD (ischemic heart disease, ischemic stroke, myocardial infarction) in parents with ≥ 1 daughters who had preeclampsia and parents whose daughters did not have preeclampsia in Denmark, 1978–2018. Our cohort included 1,299,310 parents, of whom 87,251 had ≥ 1 daughters with preeclampsia and 272,936 developed CVD during 20,252,351 years of follow-up (incidence rate 135/10,000 person-years). Parents with one daughter who had preeclampsia were 1.19 times as likely as parents of daughters without preeclampsia to develop CVD at age Preeclampsia and cardiovascular disease (CVD) might share heritable underlying mechanisms. We investigated whether preeclampsia in daughters is associated with CVD in parents. In a register-based cohort study, we used Cox regression to compare rates of CVD (ischemic heart disease, ischemic stroke, myocardial infarction) in parents with >= 1 daughters who had preeclampsia and parents whose daughters did not have preeclampsia in Denmark, 1978-2018. Our cohort included 1,299,310 parents, of whom 87,251 had >= 1 daughters with preeclampsia and 272,936 developed CVD during 20,252,351 years of follow-up (incidence rate 135/10,000 person-years). Parents with one daughter who had preeclampsia were 1.19 times as likely as parents of daughters without preeclampsia to develop CVD at age < 55 years (hazard ratio [HR] 1.19, 95% confidence interval [CI] 1.13-1.25). Having >= 2 daughters who had preeclampsia yielded an HR of 1.88 (95% CI 1.39-2.53). The corresponding HRs for CVD at >= 55 years of age were 1.13 (95% CI 1.12-1.15) and 1.27 (95% CI 1.16-1.38). Patterns of association were similar for all CVD subtypes. Effect magnitudes did not differ for mothers and fathers (p = 0.52). Analyses by timing of preeclampsia onset in daughters suggested a tendency toward stronger associations with earlier preeclampsia onset, particularly in parents < 55 years. Preeclampsia in daughters was associated with increased risks of CVD in parents. Increasing strength of association with increasing number of affected daughters, equally strong associations for mothers and fathers, and stronger associations for CVD occurring before age 55 years suggest that preeclampsia and CVD share common heritable mechanisms.

Background: Hypertensive disorders of pregnancy (HDP) remain a leading cause of maternal morbidity and mortality worldwide, with implications for maternal and neonatal well-being in the short term and for long-term maternal cardiovascular health. Although the mechanisms behind HDP remain incompletely understood, evidence suggests that preeclampsia in particular is a syndrome with more than one distinct subtype. Objectives: The PEACH (PreEclampsia, Angiogenesis, Cardiac dysfunction, Hypertension) Study was established to identify new HDP subtyping systems reflecting aetiology and prognosis and to find markers of later cardiovascular disease risk associated with preeclampsia. Population: The PEACH Study recruited pregnant women referred to two Copenhagen-area hospitals with suspected preeclampsia (mean gestational age at enrolment: 36.7 weeks) and a group of frequency-matched pregnant women planning delivery at the same hospitals and healthy when enrolled mid-pregnancy. Design: Prospective, longitudinal pregnancy cohort. Methods: Participants underwent repeated third-trimester blood sample collection, longitudinal cardiac function assessments using the USCOM-1A during the third trimester and at 1 year postpartum and collection of placental samples immediately after delivery. Medical information was abstracted from medical records and hospital databases. Preliminary results: During 2016–2018, we recruited 1149 pregnant women, of whom 1101 were followed to delivery. Among 691 women enrolled with suspected preeclampsia, 310 and 172 developed preeclampsia and gestational hypertension respectively. Among 410 women with healthy pregnancies when enrolled mid-pregnancy, 37 later developed hypertensive disorders of pregnancy. Of 1089 women still in the cohort 1 year postpartum, 578 (53.1%) participated in the follow-up assessment. Conclusions: The PEACH Study's rich data from women with and without HDP will enable us to identify new, clinically useful HDP subtypes to aid in decision-making regarding monitoring and treatment. Continued postpartum follow-up will help us develop algorithms to identify women at risk of persistent postpartum cardiac dysfunction and later cardiovascular disease after pregnancies complicated by HDP.

Objective: Many psychiatric diseases have a strong familial aggregation, but it is unknown whether postpartum depression (PPD) without prior psychiatric history aggregates in families. Methods: Based on Danish national registers, we constructed a cohort with information on 848,544 singleton deliveries (1996–2017). Women with an episode of PPD were defined as having used antidepressant medication and/or had a hospital contact for depression within 6 months after delivery. Those with psychiatric history prior to the delivery were excluded. We estimated relative risk (RR) of PPD, comparing women with female relatives with and without PPD history, respectively. Results: Overall, women with a PPD history in female blood relatives had themselves a higher risk of PPD (RR = 1.64, 95% CI 1.16–2.34). Having the first-degree female relative with PPD history was associated with a more than 2.5 times (RR = 2.65, 95% CI 1.79–3.91) increased risk of PPD. However, having the second/third-degree female relative and/or a female non-blood relative with PPD history did not increase the woman's own risk of PPD (RR = 0.58, 95% CI 0.26–1.28, RR = 1.09, 95% CI 0.83–1.44). Conclusion: Postpartum depression aggregates in families with no other psychiatric history, but the findings do not support a strong genetic trait as a major cause. Other possible mechanisms are shared environment and/or health-seeking behavior in close relationships.

A woman's reproductive history is strongly associated with her risk of ovarian cancer. However, it is unclear how pregnancies of different duration impact a woman's ovarian cancer risk, and therefore, what part of a pregnancy explains the protective effect. Using a cohort of all Danish women followed from 1968 to 2018, with prospectively registered information on reproductive history (eg, gestational duration of pregnancies, tubal ligation and resection and hormonal pharmaceutical use), we investigated the effect of pregnancy duration on ovarian cancer risk. We adjusted for potential confounders, such as age at pregnancy and time since pregnancy, using log-linear Poisson regression to isolate the effect of pregnancy duration on ovarian cancer risk. Among 2.5 million Danish women with 4.4 million pregnancies, a pregnancy was associated with a reduction of ovarian cancer risk of 21% (95% CI, 14%-28%), 26% (95% CI, 21%-31%), 12% (95% CI, 7%-17%) and 3% (95% CI, −5% to 11%) compared to one less, for the first, second, third and fourth pregnancy, respectively (P

Background: Estimates of the severity of the SARS-CoV-2 omicron variant (B.1.1.529) are crucial to assess the public health impact associated with its rapid global dissemination. We estimated the risk of SARS-CoV-2-related hospitalisations after infection with omicron compared with the delta variant (B.1.617.2) in Denmark, a country with high mRNA vaccination coverage and extensive free-of-charge PCR testing capacity. Methods: In this observational cohort study, we included all RT-PCR-confirmed cases of SARS-CoV-2 infection in Denmark, with samples taken between Nov 21 (date of first omicron-positive sample) and Dec 19, 2021. Individuals were identified in the national COVID-19 surveillance system database, which included results of a variant-specific RT-PCR that detected omicron cases, and data on SARS-CoV-2-related hospitalisations (primary outcome of the study). We calculated the risk ratio (RR) of hospitalisation after infection with omicron compared with delta, overall and stratified by vaccination status, in a Poisson regression model with robust SEs, adjusted a priori for reinfection status, sex, age, region, comorbidities, and time period. Findings: Between Nov 21 and Dec 19, 2021, among the 188 980 individuals with SARS-CoV-2 infection, 38 669 (20·5%) had the omicron variant. SARS-CoV-2-related hospitalisations and omicron cases increased during the study period. Overall, 124 313 (65·8%) of 188 980 individuals were vaccinated, and vaccination was associated with a lower risk of hospitalisation (adjusted RR 0·24, 95% CI 0·22–0·26) compared with cases with no doses or only one dose of vaccine. Compared with delta infection, omicron infection was associated with an adjusted RR of hospitalisation of 0·64 (95% CI 0·56–0·75; 222 [0·6%] of 38 669 omicron cases admitted to hospital vs 2213 [1·5%] of 150 311 delta cases). For a similar comparison by vaccination status, the RR of hospitalisation was 0·57 (0·44–0·75) among cases with no or only one dose of vaccine, 0·71 (0·60–0·86) among those who received two doses, and 0·50 (0·32–0·76) among those who received three doses. Interpretation: We found a significantly lower risk of hospitalisation with omicron infection compared with delta infection among both vaccinated and unvaccinated individuals, suggesting an inherent reduced severity of omicron. Our results could guide modelling of the effect of the ongoing global omicron wave and thus health-care system preparedness. Funding: None.

Structured AbstractObjectiveIt has been hypothesized that SARS-CoV-2 infection in children can increase risk of developing type 1 diabetes.Research Design and MethodsWe undertook a prospective analysis based on all children in Denmark where we investigated the association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes, using information from several different national Danish registers. Denmark had one of the highest test-rates per capita in the world during the pandemic.ResultsWe did not observe a higher risk of a first time diagnosis of type 1 diabetes in children 30 days or more after a positive SARS-CoV-2 test, compared to children with a history of only negative SARS-CoV-2 tests (Hazard ratio 0.85, 95% CI 0.70, 1.04).ConclusionsOur data do not support that SARS-CoV-2 infection is associated with type 1 diabetes, or that type 1 diabetes should be a special focus after a SARS-CoV-2 infection in children.Article HighlightsWhy did we undertake this study?Studies have shown an association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes, supporting the possibility of a viral etiology in type 1 diabetes and adding to concerns regarding adverse health consequences of COVID-19.What is the specific question(s) we wanted to answer?Is the risk of new onset type 1 diabetes increased among children in the period after SARS-CoV-2 infection?What did we find?We estimated the relative risk of being diagnosed with type 1 diabetes after a positive compared to a negative SARS-CoV-2 test, to 0.85 (95% CI 0.70, 1.04).What are the implications of our findings?Our data do not support an association between SARS-CoV-2 infection and subsequent risk of type 1 diabetes among children.Twitter SummaryA study based on all children in Denmark does not show any association between #SarsCoV2 infection and subsequent risk of #Type1Diabetes among persons < 18 years. #Type1Diabetes should not be a special focus after a #SarsCoV2 infection in children.

BackgroundPrevious research has suggested that some women are at increased risk of postpartum depression (PPD) because of an extra sensitivity to fluctuating hormones before and after parturition. This may particularly apply to women with endocrine disease, characterised by a less than optimal capability to self-regulate the hormonal feedback system.AimsTo investigate if women with endocrine disease history are at increased risk of developing PPD.MethodBased on information from Danish national registers, this nationwide cohort study included 888 989 deliveries (1995–2018). Endocrine disease history was defined as thyroid disease, pre-pregnancy diabetes, polycystic ovary syndrome and/or previous gestational diabetes within 10 years before pregnancy start. PPD was defined as use of antidepressants and/or hospital contact for depression within 6 months after childbirth.ResultsAmong 888 989 deliveries, 4.1% had a history of endocrine disease and 0.5% had a PPD episode. Overall, women with an endocrine disease history had a 42% (risk ratio 1.42, 95% CI 1.24–1.62) higher risk of PPD when compared with women with no endocrine disease. However, we also found the reverse association, whereby women with a PPD history had a 50% (hazard ratio 1.5, 95% CI 1.4–1.6) higher risk of endocrine disease when compared with women with no PPD history.ConclusionsWomen with endocrine disease history had a 40% higher risk of PPD compared with women with no endocrine disease. More attention should be given to pregnant women with endocrine disease history to increase awareness of early signs of PPD. The bi-directionality of the association points to a common underlying factor.

Risk of colorectal cancer (CRC) increases in relatives of patients with CRC. The extent to which this is attributable to genetic predisposition or shared environment is unclear. We explored this question using nationwide cohorts from Denmark, Finland and Sweden. From 1977 to 2013, we identified 359 879 individuals with a CRC diagnosis and 2 258 870 of their relatives who we followed for CRC incidence. We calculated standardized incidence ratios (SIR) and 95% confidence intervals (CI) for CRC in individuals with an affected relative. We used nationwide household and pedigree data along with national SIR estimates to calculate risk ratios (RR) for the contribution of shared household environment, childhood environment and genetic relationship to CRC risk in those with an affected relative. SIR of CRC was increased for individuals with an affected relative, across all countries and ages. For those with an affected parent, the SIR was 1.65 (95% CI: 1.61-1.69), 1.98 (95% CI: 1.87-2.09), for those with an affected sibling and 2.14 (95% CI: 1.84-2.49) for those with an affected halfsibling. In those

IntroductionIndividuals with a prior severe acute respiratory corona virus 2 (SARS-CoV-2) infection have a moderate to high degree of protection against reinfection, though seemingly less so when the Omicron variant of SARS-CoV-2 started to circulate. The aim of this study was to evaluate the vaccine effectiveness (VE) against SARS-CoV-2 reinfection, that is, in individuals with prior SARS-CoV-2 infection, during periods with different dominant SARS-CoV-2 variants.MethodsA nationwide cohort study design including all individuals with a confirmed SARS-CoV-2 infection, who were alive and residing in Denmark between 1 January 2020 and 31 January 2022 were used. Using Danish nationwide registries, we obtained information on SARS-CoV-2 infections, Coronavirus Disease 2019 (COVID-19) vaccination, age, sex, comorbidity, staying at hospital and region of affiliation. The study population included were individuals with prior SARS-CoV-2 infection. Crude and adjusted estimates of VE against SARS-CoV-2 reinfection with 95% confidence intervals (CIs) were calculated using Poisson and Cox regression models, respectively. The VE estimates were calculated separately for three periods with different dominant SARS-CoV-2 variants (Alpha (B.1.1.7), Delta (B.1.617.2), or Omicron (B.1.1.529)) and by time since vaccination using unvaccinated as the reference.FindingsThe study population comprised of 209,814 individuals infected before or during the Alpha period, 292,978 before or during the Delta period and 245,530 before or during the Omicron period. Of these, 40,281 individuals had completed their primary vaccination series during the Alpha period (19.2%), 190,026 during the Delta period (64.9%) and 158,563 during the Omicron period (64.6%). VE against reinfection following any COVID-19 vaccine type administered in Denmark, peaked at 85% (95% CI: 37% to 97%) at 104 days or more after vaccination during the Alpha period, 88% (95% CI: 81% to 92%) 14-43 days after vaccination during the Delta period and 60% (95% CI: 58% to 62%) 14-43 days after vaccination during the Omicron period. Waning immunity was observed, and was most pronounced during the Omicron period.InterpretationThis study shows that, in previously infected individuals, completing a primary vaccination series was associated with a significant protection against SARS-CoV-2 reinfection compared with no vaccination for all three variant periods. Even though vaccination seems to protect to a lesser degree against reinfection with the Omicron variant, these findings are of public health relevance as they show that previously infected individuals still benefit from COVID-19 vaccination in all three variant periods.

Objective To investigate the association between gestational age at birth and cognitive outcomes in adolescence. Design Nationwide population based full sibling cohort study. Setting Denmark. Participants 1.2 million children born between 1 January 1986 and 31 December 2003, of whom 792 724 had one or more full siblings born in the same period. Main outcome measures Scores in written language (Danish) and mathematics examinations as graded by masked assessors at the end of compulsory schooling (ninth grade, ages 15-16 years), in addition to intelligence test score at military conscription (predominantly at age 18 years) for a nested sub-cohort of male adolescents. School grades were standardised as z scores according to year of examination, and intelligence test scores were standardised as z scores according to year of birth. Results Among 792 724 full siblings in the cohort, 44 322 (5.6%) were born before 37+0 weeks of gestation. After adjusting for multiple confounders (sex, birth weight, malformations, parental age at birth, parental educational level, and number of older siblings) and shared family factors between siblings, only children born at Conclusions Cognitive outcomes in adolescence did not differ between those born at 34-39 gestational weeks and those born at 40 gestational weeks, whereas those with a gestational age of

Following emergence of the SARS-CoV-2 variant Omicron in November 2021, the dominant BA.1 sub-lineage was replaced by the BA.2 sub-lineage in Denmark. We analysed the first 2,623 BA.2 cases from 29 November 2021 to 2 January 2022. No epidemiological or clinical differences were found between individuals infected with BA.1 versus BA.2. Phylogenetic analyses showed a geographic east-to-west transmission of BA.2 from the Capital Region with clusters expanding after the Christmas holidays. Mutational analysis shows distinct differences between BA.1 and BA.2.

Background: Smaller studies have reported a higher offspring risk of congenital heart defects (CHDs) for mothers with CHDs than for fathers with CHDs. In a large population-based study, we investigated whether offspring risk of CHD differed for mothers and fathers with CHDs. Methods: All people born in Denmark, 1977 to 2011, with at least 1 registered parent, were included in our cohort (n=2 341 061). Parent-child recurrence of CHDs was evaluated using risk ratios (RRs) comparing risks of CHDs in individuals with and without a parent with a CHD, estimated using log-linear binomial regression. Results: The RRs for any CHD in offspring were 5.39 (95% CI, 4.88–5.96) for mothers and 3.04 (95% CI, 2.59–3.57) for fathers affected with any CHD; the ratio of RRs for mothers versus fathers was 1.82 ( P Conclusions: Recurrence risks of CHDs were significantly greater in the offspring of affected women than in the offspring of affected men. The excess maternal recurrence risks could not be explained by the slightly higher birth rates in women with CHDs.

Background Studies investigating the prevalence and risk factors for postpartum depression (PPD) have used different definitions. Some studies have used a high score on the Edinburgh Postnatal Depression Scale (EPDS) to define PPD, whereas others have used information on antidepressant medication use and/or diagnostic information on treatment for depression at a psychiatric hospital. We wanted to compare results using these two approaches to evaluate to what degree results can be compared. Moreover we wanted to evaluate, whether use of EPDS or PPAT (defined below) leads to identification of different risk factor profiles. Methods We identified women who delivered a child between 1 January 2014 and 31 December 2016 in Copenhagen or in one of the municipalities that were part of the Danish Health Visitors’ Child Health Database. The potential risk factors were demographic factors and pregnancy- and obstetrical events. Outcomes of interest were an EPDS score ≥ 13, use of antidepressants (ATC: N06A) and/or a diagnosis of depression (F32) within six months after birth. Use of antidepressants and/or diagnosis of depression will be referred to as postpartum antidepressant treatment (PPAT). Agreement between EPDS ≥ 13 and PPAT was evaluated by the kappa coefficient. Associations between risk factors and the two outcomes (EPDS ≥ 13 and PPAT) were estimated by risk ratios (RR) using log-linear binomial regression. Presence of a systematic difference between RRs based on EPDS ≥ 13 (RREPDS≥13) and PPAT (RRPPAT) was evaluated in a meta-regression approach weighted by inverse-variance and with logarithm of the RRs as outcome. Results The estimated PPD prevalence using EPDS ≥ 13 was 3.2% and of PPAT 0.4%. The agreement between the two measures was small (Kappa = 0.08), but their risk factor profile was very similar with no systematic difference between them. Conclusions Using the two different methods of case identification produced different prevalence estimates, but a similar risk factor profile. The differences in estimated prevalence and low agreement suggest that the two measures identify different potential PPD cases and using only one of the methods in defining PPD would underestimate PPD prevalence. The similar risk factor profile suggests that the considered risk factors are involved in the general development of PPD.

Importance: Reports of myocarditis after SARS-CoV-2 messenger RNA (mRNA) vaccination have emerged. Objective: To evaluate the risks of myocarditis and pericarditis following SARS-CoV-2 vaccination by vaccine product, vaccination dose number, sex, and age. Design, Setting, and Participants: Four cohort studies were conducted according to a common protocol, and the results were combined using meta-analysis. Participants were 23122522 residents aged 12 years or older. They were followed up from December 27, 2020, until incident myocarditis or pericarditis, censoring, or study end (October 5, 2021). Data on SARS-CoV-2 vaccinations, hospital diagnoses of myocarditis or pericarditis, and covariates for the participants were obtained from linked nationwide health registers in Denmark, Finland, Norway, and Sweden. Exposures: The 28-day risk periods after administration date of the first and second doses of a SARS-CoV-2 vaccine, including BNT162b2, mRNA-1273, and AZD1222 or combinations thereof. A homologous schedule was defined as receiving the same vaccine type for doses 1 and 2. Main Outcomes and Measures: Incident outcome events were defined as the date of first inpatient hospital admission based on primary or secondary discharge diagnosis for myocarditis or pericarditis from December 27, 2020, onward. Secondary outcome was myocarditis or pericarditis combined from either inpatient or outpatient hospital care. Poisson regression yielded adjusted incidence rate ratios (IRRs) and excess rates with 95% CIs, comparing rates of myocarditis or pericarditis in the 28-day period following vaccination with rates among unvaccinated individuals. Results: Among 23122522 Nordic residents (81% vaccinated by study end; 50.2% female), 1077 incident myocarditis events and 1149 incident pericarditis events were identified. Within the 28-day period, for males and females 12 years or older combined who received a homologous schedule, the second dose was associated with higher risk of myocarditis, with adjusted IRRs of 1.75 (95% CI, 1.43-2.14) for BNT162b2 and 6.57 (95% CI, 4.64-9.28) for mRNA-1273. Among males 16 to 24 years of age, adjusted IRRs were 5.31 (95% CI, 3.68-7.68) for a second dose of BNT162b2 and 13.83 (95% CI, 8.08-23.68) for a second dose of mRNA-1273, and numbers of excess events were 5.55 (95% CI, 3.70-7.39) events per 100000 vaccinees after the second dose of BNT162b2 and 18.39 (9.05-27.72) events per 100000 vaccinees after the second dose of mRNA-1273. Estimates for pericarditis were similar. Conclusions and Relevance: Results of this large cohort study indicated that both first and second doses of mRNA vaccines were associated with increased risk of myocarditis and pericarditis. For individuals receiving 2 doses of the same vaccine, risk of myocarditis was highest among young males (aged 16-24 years) after the second dose. These findings are compatible with between 4 and 7 excess events in 28 days per 100000 vaccinees after BNT162b2, and between 9 and 28 excess events per 100000 vaccinees after mRNA-1273. This risk should be balanced against the benefits of protecting against severe COVID-19 disease.

The aim of the present study was to describe histopathologic characteristics of synchronous bilateral breast cancer (SBBC), and by comparing SBBC to unilateral breast cancer (UBC), identify possible etiological mechanisms of SBBC. Patients with primary SBBC (diagnosed within 4 months) and UBC diagnosed in Denmark between 1999 and 2015 were included. Detailed data on histopathology were retrieved from the Danish Breast Cancer Group database and the Danish Pathology Register. Associations between bilateral disease and the different histopathologic characteristics were evaluated by odds ratios and estimated by multinomial regression models. 1214 patients with SBBC and 59,221 with UBC were included. Patients with SBBC more often had invasive lobular carcinomas (OR 1.29; 95% CI 1.13–1.47), a clinically distinct subtype of breast cancer, than UBC patients. Further, they were older than UBC patients, more often had multifocal cancer (OR 1.13; 95% CI 1.01–1.26), and a less aggressive subtype than UBC patients. Invasive lobular carcinoma was associated with having multiple tumors in breast tissue—both in the form of bilateral disease and multifocal disease, and this association was independent of laterality. No similar pattern was observed for other tumor characteristics. We identified two etiological mechanisms that could explain some of the occurrence of SBBC. The high proportion of less aggressive carcinomas and higher age of SBBC compared to UBC patients suggests that many are diagnosed at a subclinical stage as slow-growing tumors have a higher probability of simultaneous diagnosis. The high proportion of invasive lobular carcinoma observed in bilateral and multifocal disease, being independent of laterality, suggests that these patients have an increased propensity to malignant tumor formation in breast tissue.

Background Pre-pregnancy diabetes is a strong risk factor for congenital heart defects (CHDs), suggesting a role for glucose in the causal pathway. Oral corticosteroids may cause hyperglycemia and maternal use could affect embryonic heart development. The objective of this study was to determine the association between maternal intake of oral corticosteroids 0–8 weeks after conception and CHDs in offspring. Methods A register-based nationwide prevalence study including all live singleton births in Denmark, 1996–2016, was conducted. In total, 1 194 687 individuals and their mothers were identified and linked with information on offspring CHDs and the mothers’ use of oral corticosteroids in early pregnancy. Corticosteroid use was defined as a filled prescription for maternal use of oral corticosteroid 0–8 weeks after conception. CHDs were identified through International Classification of Diseases codes. The association was estimated by prevalence (odds) ratios using logistic regression and propensity score-matched analyses. Results Among 1 194 687 live births, 2032 had a mother who had used oral corticosteroids 0–8 weeks from conception. Of these offspring, 32 had a heart defect. Among the offspring of never-users of oral corticosteroids, 10 534 had a heart defect. The adjusted prevalence ratio was 1.29 (95% confidence interval, 0.90–1.84) comparing offspring prevalence of heart defects in oral corticosteroid users with that in oral corticosteroid never-users. Propensity score-matched analysis yielded similar results (prevalence ratio 1.38; 95% confidence interval, 0.95–2.02). Conclusions This study supports that there is no association between maternal use of oral corticosteroids in the first 8 weeks after conception and CHDs.

Background: The more infectious SARS-CoV-2 lineage B.1.1.7 rapidly spread in Europe after December, 2020, and a concern that B.1.1.7 could cause more severe disease has been raised. Taking advantage of Denmark's high RT-PCR testing and whole genome sequencing capacities, we used national health register data to assess the risk of COVID-19 hospitalisation in individuals infected with B.1.1.7 compared with those with other SARS-CoV-2 lineages. Methods: We did an observational cohort study of all SARS-CoV-2-positive cases confirmed by RT-PCR in Denmark, sampled between Jan 1 and March 24, 2021, with 14 days of follow-up for COVID-19 hospitalisation. Cases were identified in the national COVID-19 surveillance system database, which includes data from the Danish Microbiology Database (RT-PCR test results), the Danish COVID-19 Genome Consortium, the National Patient Registry, the Civil Registration System, as well as other nationwide registers. Among all cases, COVID-19 hospitalisation was defined as first admission lasting longer than 12 h within 14 days of a sample with a positive RT-PCR result. The study population and main analysis were restricted to the proportion of cases with viral genome data. We calculated the risk ratio (RR) of admission according to infection with B.1.1.7 versus other co-existing lineages with a Poisson regression model with robust SEs, adjusted a priori for sex, age, calendar time, region, and comorbidities. The contribution of each covariate to confounding of the crude RR was evaluated afterwards by a stepwise forward inclusion. Findings: Between Jan 1 and March 24, 2021, 50 958 individuals with a positive SARS-CoV-2 test and at least 14 days of follow-up for hospitalisation were identified; 30 572 (60·0%) had genome data, of whom 10 544 (34·5%) were infected with B.1.1.7. 1944 (6·4%) individuals had a COVID-19 hospitalisation and of these, 571 (29·4%) had a B.1.1.7 infection and 1373 (70·6%) had an infection with other SARS-CoV-2 lineages. Although the overall number of hospitalisations decreased during the study period, the proportion of individuals infected with B.1.1.7 increased from 3·5% to 92·1% per week. B.1.1.7 was associated with a crude RR of hospital admission of 0·79 (95% CI 0·72–0·87; p

Introduction Pregnancy losses may be associated with increased risks of dementia. Methods We conducted a register-based cohort study in 1,243,957 women with ≥1 pregnancy in Denmark in the period 1977–2015. Using Cox regression, we estimated hazard ratios (HRs) comparing risks of dementia in women with and without pregnancy losses. Results During 21,672,433 person-years of follow-up, 261,279 women experienced a pregnancy loss, and 2188 women were diagnosed with dementia. Stillbirth was associated with an 86% increased risk of dementia overall (HR 1.86, 95% confidence interval [CI] 1.28–2.71). By contrast, miscarriage was not associated with later risk of dementia overall (single miscarriage, HR 0.99, 95% CI 0.87–1.12; recurrent miscarriages, HR 1.06, 95% CI 0.84–1.35). Adjustment for cardiovascular disease, hypertension, and diabetes did not meaningfully alter the association magnitudes. Discussion Stillbirth and dementia may share underlying mechanisms, suggesting that a history of stillbirth should be considered when assessing dementia risk in women.

Linnea Boegeskov Schmidt,1 Giulia Corn,1 Jan Wohlfahrt,1 Mads Melbye,1–3 Tina Noergaard Munch1,4 1Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark; 2Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; 3Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA; 4Department of Neurosurgery, Copenhagen University Hospital, Copenhagen, Denmark Purpose: Little is known about the prognosis for school performance among children with all-cause infantile hydrocephalus (IHC). Using detailed educational data, we investigated the school performance for IHC patients compared to other children in Denmark. Patients and methods: We conducted a population-based cohort study of all live-born children in Denmark (1977–2015) based on data from the Danish national health registers and the Danish educational register. The cumulative chance of completing school at age 18 years was estimated using the Aalen–Johansen estimator. The relative risks presented as ORs for not completing school, obtaining grades, or obtaining a grade point average below the national mean value were estimated using a logistic regression model. Results: The cohort included 2,381,413 children, and of these, 2,573 were diagnosed with IHC. A total of 86% of IHC children completed compulsory school compared to 96% among other children; only 62% of IHC children who completed school received marks vs 96% among other children. Mediation analyses indicated that one-third of these poorer performances in IHC children could be attributable to their higher prevalence of epilepsy, spasticity, visual disturbances, autism, and attention-deficit hyperactivity disorder. Completion rates were similar for isolated and non-isolated hydrocephalus, and did not vary by age at diagnosis or number of surgeries. Of the children with isolated IHC, 73% obtained grades vs 58% of the children with non-isolated IHC. Poorer school performance in IHC children was also observed when considering age at school start, grade point average, and completion of further education. Conclusion: The poorer school performance among IHC children is particularly reflected by the larger proportion not obtaining grades compared to other children. However, the performance of the IHC children obtaining grades is comparable to that of other children. Keywords: pediatric hydrocephalus, long-term outcome, prognosis, school performance

Background: The more infectious SARS-CoV-2 virus lineage B.1.1.7, rapidly spread in Europe after December 2020, and a concern of B.1.1.7 causing more severe disease has been raised. Denmark has one of Europe´s highest capacities per capita of SARS-CoV-2 reverse transcription polymerase chain reaction (RT PCR) test and whole genome sequencing (WGS). We used national health register-data to explore whether B.1.1.7 increases the risk of COVID-19 hospitalisation. Methods and Findings: In an observational cohort study we included all SARS-CoV-2 RT PCR test-positive individuals in Denmark sampled between the 1st January and until the 9th February, 2021, identified in the national COVID-19 surveillance system. The surveillance system includes national individual RT PCR test results and viral WGS analyses and data from national health registers including COVID-19 related hospital admissions defined as first admission within 14 days of the test-positive swab. The odds ratio (OR) of admission according to infection with B.1.1.7, vs other co-existing lineages, was calculated in a logistic regression model adjusted for sex, age, period, follow-up time less than 14 days, region, and comorbidities. A total of 35,887 test-positive individuals were identified, 23,057 (64%) had WGS performed, of whom 18,499 (80%) resulted in a viral genome and a total of 2,155 of these were lineage B.1.1.7. The proportion of individuals with B.1.1.7 increased from 4% in early January to 45% in early February. Among the individuals with viral genome data, B.1.1.7 was associated with a crude OR of admission of 0.87 (95%CI, 0.72-1.05) and an adjusted OR of 1.64 (95%CI, 1.32-2.04) based on 128 admissions after B.1.1.7 infection and 1,107 admissions after infection with other lineages. The adjusted OR was increased in all strata of age and calendar time - the two most important confounders of the crude OR. Conclusions: Infection with lineage B.1.1.7 was associated with an increased risk of hospitalisation compared with other lineages. This finding may have serious public health impact in countries with spread of B.1.1.7 and can support hospital preparedness and modelling of projected impact of the epidemic. Funding Statement: The authors received no specific funding for this work. Declaration of Interests: The authors declare that they have no competing interest. Ethics Approval Statement: This study was conducted on administrative register data. According to Danish law, ethics approval is not needed for such research.

BackgroundInfantile hypertrophic pyloric stenosis (IHPS) is caused by hypertrophy of the pyloric sphincter smooth muscle. Building on a previously reported association between IHPS and lipid metabolism, we aimed to (1) investigate associations between IHPS and a wide array of lipid-centric targeted metabolites in newborns, and (2) address causality of the associations by integrating genetic data.MethodsDried blood spots were taken from 267 pairs of IHPS cases and controls matched by sex and day of birth. A mixed effects linear regression model was used to evaluate associations between Biocrates p400 Kit selected 148 metabolites and IHPS in a matched case-control design.ResultsSeven metabolites showed significantly lower levels in IHPS cases. Levels of the top associated metabolite, phosphatidylcholine PC(38:4), were significantly correlated with levels of the remaining six metabolites (P−12). Associations were driven by case-control pairs with older age at sampling. IHPS cases had more diagnoses for neonatal difficulty in feeding at breast (P = 6.15 ⨯ 10−3). Genetic variants explaining a large proportion of variance in the levels of PC(38:4) did not associate with IHPS.ConclusionsWe detected lower levels of certain metabolites in IHPS, possibly reflecting different feeding patterns in the first days of life.Key points–Our previous GWAS of IHPS identified genetic associations between lipid metabolism and IHPS.–Building on that finding, this study investigated associations between a wide array of lipid-centric metabolites in newborns and IHPS.–Newborns who later developed IHPS had lower levels of certain metabolites. The associations were driven by individuals born at a later age at sampling, suggesting different feeding patterns after birth.

ObjectiveTo investigate the association between SARS-CoV-2 vaccination and myocarditis or myopericarditis.DesignPopulation based cohort study.SettingDenmark.Participants4 931 775 individuals aged 12 years or older, followed from 1 October 2020 to 5 October 2021.Main outcome measuresThe primary outcome, myocarditis or myopericarditis, was defined as a combination of a hospital diagnosis of myocarditis or pericarditis, increased troponin levels, and a hospital stay lasting more than 24 hours. Follow-up time before vaccination was compared with follow-up time 0-28 days from the day of vaccination for both first and second doses, using Cox proportional hazards regression with age as an underlying timescale to estimate hazard ratios adjusted for sex, comorbidities, and other potential confounders.ResultsDuring follow-up, 269 participants developed myocarditis or myopericarditis, of whom 108 (40%) were 12-39 years old and 196 (73%) were male. Of 3 482 295 individuals vaccinated with BNT162b2 (Pfizer-BioNTech), 48 developed myocarditis or myopericarditis within 28 days from the vaccination date compared with unvaccinated individuals (adjusted hazard ratio 1.34 (95% confidence interval 0.90 to 2.00); absolute rate 1.4 per 100 000 vaccinated individuals within 28 days of vaccination (95% confidence interval 1.0 to 1.8)). Adjusted hazard ratios among female participants only and male participants only were 3.73 (1.82 to 7.65) and 0.82 (0.50 to 1.34), respectively, with corresponding absolute rates of 1.3 (0.8 to 1.9) and 1.5 (1.0 to 2.2) per 100 000 vaccinated individuals within 28 days of vaccination, respectively. The adjusted hazard ratio among 12-39 year olds was 1.48 (0.74 to 2.98) and the absolute rate was 1.6 (1.0 to 2.6) per 100 000 vaccinated individuals within 28 days of vaccination. Among 498 814 individuals vaccinated with mRNA-1273 (Moderna), 21 developed myocarditis or myopericarditis within 28 days from vaccination date (adjusted hazard ratio 3.92 (2.30 to 6.68); absolute rate 4.2 per 100 000 vaccinated individuals within 28 days of vaccination (2.6 to 6.4)). Adjusted hazard ratios among women only and men only were 6.33 (2.11 to 18.96) and 3.22 (1.75 to 5.93), respectively, with corresponding absolute rates of 2.0 (0.7 to 4.8) and 6.3 (3.6 to 10.2) per 100 000 vaccinated individuals within 28 days of vaccination, respectively. The adjusted hazard ratio among 12-39 year olds was 5.24 (2.47 to 11.12) and the absolute rate was 5.7 (3.3 to 9.3) per 100 000 vaccinated individuals within 28 days of vaccination.ConclusionsVaccination with mRNA-1273 was associated with a significantly increased risk of myocarditis or myopericarditis in the Danish population, primarily driven by an increased risk among individuals aged 12-39 years, while BNT162b2 vaccination was only associated with a significantly increased risk among women. However, the absolute rate of myocarditis or myopericarditis after SARS-CoV-2 mRNA vaccination was low, even in younger age groups. The benefits of SARS-CoV-2 mRNA vaccination should be taken into account when interpreting these findings. Larger multinational studies are needed to further investigate the risks of myocarditis or myopericarditis after vaccination within smaller subgroups.

Background Extremely strong associations between male hormone-interfering drugs and meningiomas have been reported in two previous studies, but these findings are limited by small size of the study populations and possibly by surveillance- and selection bias. Thus, such possible and indeed very interesting association must be investigated in a large, unselected cohort. Accordingly, the aim of this study was to determine whether patients exposed to male hormone-interfering drugs had a higher risk of meningioma development in a nationwide cohort study. Methods A retrospective Danish nationwide cohort study with follow-up from January 1, 1996 to December 31, 2016. Exposure was use of male hormone-interfering drugs (5-α-reductase-inhibitors, luteinizing hormone-releasing hormone agonist, steroidal antiandrogen, and nonsteroidal antiandrogen). Hazard ratio of first-time diagnosis of meningioma according to drug use was estimated using Cox proportional hazards model with adjustment for age and birth year. Results The cohort included 244,696 men of which 64,047 had used male hormone-interfering drugs. Overall 444 meningiomas occurred during follow-up. No significant association was observed between use of male hormone-interfering drugs and the occurrence of meningioma (hazard ratio 1.02, 95% confidence interval 0.82–1.27). Similar results were observed 0–1, 2–4, and 5+ years after first use. In explorative analyses, no elevated risk association was observed for specific drugs (5-α-reductase-inhibitors, luteinizing hormone-releasing hormone agonist, steroidal antiandrogen, and nonsteroidal antiandrogen). Conclusion As opposed to previous studies, we found no evidence of an increased risk of meningioma in men treated with male hormone-interfering drugs.

STUDY QUESTION Is maternal polycystic ovary syndrome (PCOS) associated with increased offspring risk of congenital heart defects? SUMMARY ANSWER This study does not support a strong association between PCOS and an increased risk of congenital heart defects. WHAT IS KNOWN ALREADY In addition to affecting reproductive health, PCOS may involve insulin resistance. Maternal pregestational diabetes is associated with an increased risk of congenital heart defects and therefore PCOS may increase the risk of congenital heart defects in the offspring. STUDY DESIGN, SIZE, DURATION In this nationwide cohort study, we used data from Danish health registers collected from 1995 to 2018. The study included 1 302 648 offspring and their mothers. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were live singleton offspring born during the study period. Information on maternal PCOS and offspring congenital heart defects was obtained from the National Patient Register. Logistic regression analysis was used to compute prevalence (odds) ratio (PR) of the association between PCOS and offspring congenital heart defects. MAIN RESULTS AND THE ROLE OF CHANCE Among 1 302 648 live-born singletons, 11 804 had a mother with PCOS. Of these, 143 offspring had a congenital heart defect (prevalence 121 per 10 000) as compared with 12 832 among mothers without PCOS (prevalence 99 per 10 000). The adjusted PR was 1.22, 95% CI 1.03–1.44 comparing prevalence of congenital heart defects in offspring of women with PCOS with offspring of women without. After adjusting for the potentially mediating effect of pregestational diabetes, the PR was 1.16, 95% CI 0.98–1.37. LIMITATIONS, REASONS FOR CAUTION PCOS may be underdetected in the National Patient Register. However, we expect that the mothers that we identified with PCOS truly had PCOS, thus, the estimated associations are not likely to be affected by this misclassification. The study does not provide evidence to rule out a moderate or weak association. WIDER IMPLICATIONS OF THE FINDINGS These findings provide reassurance to clinicians counselling pregnant women with PCOS that the disease does not pose a markedly increased risk of offspring congenital heart defects. STUDY FUNDING/COMPETING INTEREST(S) The study was funded by the Novo Nordisk Foundation. M.L. reports personal fees from Dansk Lægemiddel Information A/S outside the submitted work. The remaining authors have no conflicts of interest TRIAL REGISTRATION NUMBER N/A