Type 2 diabetes risk after gestational diabetes according to country/region of origin. A nationwide register-based study

CONTEXT

The risk of gestational diabetes mellitus (GDM) differs between the Danish population and several migrant groups. However, it is unclear if the incidence and timing of type 2 diabetes mellitus (T2DM) following GDM vary similarly.

OBJECTIVE

To investigate the incidence of T2DM according to migration background based on country/region of origin among women with a previous GDM diagnosis and explore the role of time since GDM diagnosis on the association.

METHOD

Using nationwide registry data, we followed women diagnosed with GDM in Denmark during 2004-2018 to Dec 31, 2020. Poisson regression models were used to estimate incidence rates (IRs) of T2DM according to country/region of origin, adjusted for age, education, and body mass index.

RESULTS

The study included 20,873 women with a GDM diagnosis, of whom 22.3% were of migrant background and 77.7% were Danish. The mean follow-up time was 7.3 years, and 10.9% were registered with T2DM during the study period. Generally, migrant women had higher IRs of T2DM compared to Danish women, with substantial variations in risk between migrant groups. Women from Pakistan and Sri Lanka had three-four times higher IRs compared to Danish women. The timing of T2DM onset also varied, with women from Sri Lanka and Pakistan having an earlier onset of T2DM compared to other migrant and Danish women.

CONCLUSION

This study demonstrated that country/region of origin is an important risk factor for T2DM in women with GDM. These findings underscore the importance of prevention programs targeting women with GDM and a high-risk origin.

Body Mass Index Trajectories in Children Exposed to Gestational Diabetes in Utero: A Nationwide Register-based Study

CONTEXT

Children exposed to gestational diabetes mellitus (GDM) in utero are at high risk of developing overweight and obesity, but their postnatal growth trajectories and risk profiles remain unclear.

OBJECTIVE

We aimed to identify distinct body mass index (BMI) trajectories from birth to 10 years of age in children exposed to GDM and to explore their associations with infant and maternal characteristics.

METHODS

This nationwide cohort study linked data from Danish registries on 15 509 children exposed to GDM in utero, born in Denmark from January 2008 to October 2019. We applied latent class trajectory modeling to identify distinct BMI trajectories. Associations of BMI trajectories with infant and maternal characteristics were analyzed using multiple linear regression.

RESULTS

We identified 3 distinct BMI trajectories characterized by a "normal" (60%), a "late accelerating" (28%) and an "early accelerating" (12%) BMI trajectory, the 2 latter at risk of overweight and obesity, respectively, at age 10 years, relative to World Health Organization child growth standards. Children in the "late accelerating" BMI trajectory were more often born large for gestational age (P < .001). More children in the "early accelerating" BMI trajectory were boys, born small for gestational age, and had mothers with a higher pre-pregnancy BMI compared to the other groups (P < .001).

CONCLUSION

Children exposed to GDM in utero differ widely in their BMI trajectory. The detection of risk profiles based on early BMI growth and infant and maternal characteristics provides an opportunity for future targeted care and prevention.

The Danish National Child Health Register

Aim of the Database

The aim of the National Child Health Registry is to provide comprehensive insight into children's health and growth on a national scale by continuously monitoring the health status of Danish children. Through this effort, the registry assists the health authorities in prioritizing preventive efforts to promote better child health outcomes.

Study Population

The registry includes all Danish children, however, incomplete coverage persists.

Main Variables

The National Child Health Registry contains information on exposure to secondhand smoking, breastfeeding duration, and anthropometric measurements through childhood. The information in the registry is divided into three datasets: Smoking, Breastfeeding, and Measurements. Beside specific information on the three topics, all datasets include information on CPR-number, date of birth, sex, municipality, and region of residence.

Database Status

The National Child Health Registry was established in 2009 and contains health information on children from all Danish municipalities, collected through routinely performed health examinations conducted by general practitioners and health nurses.

Conclusion

The National Child Health Register is an asset to epidemiological and health research with nationwide information on children's health and growth in Denmark. Due to the unique Danish Civil Registration System, it is possible to link data from the National Child Health Register to information from several other national health and social registers which enables longitudinal unambiguous follow-up.

Preterm birth and educational disadvantage: Heterogeneous effects

Although preterm birth is the leading cause of perinatal morbidity and mortality in advanced economies, evidence about the consequences of prematurity in later life is limited. Using Swedish registers for cohorts born 1982-94 (N  =  1,087,750), we examine the effects of preterm birth on school grades at age 16 using sibling fixed effects models. We further examine how school grades are affected by degree of prematurity and the compensating roles of family socio-economic resources and characteristics of school districts. Our results show that the negative effects of preterm birth are observed mostly among children born extremely preterm (<28 weeks); children born moderately preterm (32-<37 weeks) suffer no ill effects. We do not find any evidence for a moderating effect of parental socio-economic resources. Children born extremely preterm and in the top decile of school districts achieve as good grades as children born at full term in an average school district.Supplementary material for this article is available at: http://dx.doi.org/10.1080/00324728.2022.2080247.

Agreement between survey- and register-based measures of depression in Denmark

BACKGROUND

Register-based studies of major depressive disorder (MDD) do not capture all prevalent cases, as untreated cases and diagnoses made by general practitioners are not recorded in the registers. We examined the prevalence and agreement of survey- and register-based measures of depression, and explored sociodemographic and health-related factors that may have influenced this agreement.

METHODS

All 32,407 participants in the 2017 Central Denmark Region How are you? survey were linked to hospital and prescription records. A checklist for depressive symptoms within the last 14 days (Major Depression Inventory; MDI) from the survey was compared with register-based assessment of hospital-diagnosed MDD and/or prescriptions for antidepressants. We estimated agreement between survey-based and register-based measures for depression and used logistic regression models to explore selected associated factors.

RESULTS

In total, 5.9% of How are you? survey participants screened positive for current depression on the MDI. Of these, 51.3% (95% confidence interval (CI): 49.0-53.6) filled a prescription for an antidepressant medication during the 10 years prior or 2 years following the administration of the survey, and 14.5% (95% CI: 12.9-16.2) were treated for MDD in a psychiatric hospital-based setting. When using a higher threshold of the MDI indicating more severe current depression, 22.8% (95% CI: 19.6-26.1) of those who screened positive also received an MDD diagnosis and 63.4% (95% CI: 59.7-67.2) were prescribed antidepressants during this 12-year period. Among those with current depression, female sex, older age, chronic diseases, hospital-treated self-harm, and being permanently outside the workforce were associated with having a register-based MDD diagnosis or antidepressant prescription. Among those with a register-based depression record, female sex, younger age, hospital-treated self-harm, stress, and severe loneliness were associated with current depression.

CONCLUSION

We found that as few as 15% of individuals with current depression in the general Danish population were captured by the psychiatric hospital register, while 51% of these individuals were identifiable in the prescription register. These findings demonstrate that register-based measures significantly underestimate the true prevalence of depression by identifying only the cases that are most severe.

CRCBaSe: a Swedish register-based resource for colorectal adenocarcinoma research

OBJECTIVES

To facilitate high-quality register-based research on colorectal cancer (CRC) in Sweden by constructing a database consisting of CRC patients, matched comparators, and relatives.

MATERIAL AND METHODS

Patients with adenocarcinoma in the colon and/or rectum were identified in the Swedish Colorectal Cancer Register, a nationwide quality-of-care register. For each patient, six comparators from the general population were matched on birth year, sex, year of CRC diagnosis, and county. Comparators were free from CRC at the time of matching, but could later become cases. For both patients and comparators, first-degree relatives (parents, siblings, and children) were identified. Information from nationwide population-based registers was retrieved and linked to each individual in the database using the personal identification number unique to all Swedish residents.

RESULTS

A total of 76,831 CRC patients diagnosed between 1995 and 2016 were identified (51% colon, 49% rectal; before 2007 only rectal cancer patients were included). Among all patients, 37% were stage I-II, 22% stage III, and 22% stage IV. The median follow-up time was 11.9 years (inter-quartile range, IQR: 8.6-15.3). Together with comparators and relatives, the database contains 2,413,139 individuals with information on demographics, dates and causes of death, in- and outpatient healthcare records, cancer diagnoses, prescribed and dispensed drugs, childbirths (among women), and social security information (such as sick leave and early retirement).

CONCLUSION

The Colorectal Cancer Database Sweden (CRCBaSe) is a large and unique register-based data research platform, which opens up for clinically important, large epidemiological studies with innovative design in the field of colorectal adenocarcinoma.

Positive Predictive Value of Non-Traumatic Bleeding Diagnoses in the Danish National Patient Register

Purpose

The majority of bleeding diagnoses in the Danish National Patient Registry have not been validated despite extensive use in epidemiological research. Therefore, we examined the positive predictive value (PPV) of non-traumatic bleeding diagnoses in the Danish National Patient Registry.

Study Design

Population-based validation study.

Patients and Methods

Based on a manual review of electronic medical records, we estimated the PPV of diagnostic coding (International Classification of Diseases, Tenth Revision (ICD-10)) for non-traumatic bleeding for all patients ≥65 years of age with any hospital contact in the North Denmark Region during March-December 2019 as registered in the Danish National Patient Registry. We calculated PPVs and associated 95% confidence intervals (CI) for non-traumatic bleeding diagnoses overall and stratified according to primary or secondary diagnosis, and according to major anatomical sites.

Results

A total of 907 electronic medical records were available for review. The population mean age was 79.33 years (standard deviation (SD)=7.73) and 57.6% were males. Primary bleeding diagnoses accounted for 766 of the records and 141 were secondary bleeding diagnoses. The overall PPV for bleeding diagnoses was 94.0% (95% CI: 92.3-95.4). The PPV was 98.7% (95% CI: 97.6-99.3) for the primary diagnoses and 68.8% (95% CI: 60.7-75.9) for the secondary diagnoses. When stratified according to subgroups of major anatomical sites, the PPVs ranged between 94.1% and 100% for the primary diagnoses, and between 53.8% and 100% for secondary diagnoses.

Conclusion

The overall validity of non-traumatic bleeding diagnoses in the Danish National Patient Registry is high and considered acceptable for epidemiological research. However, PPVs were substantially higher for primary than for secondary diagnosis.

Cohort Profile: The Socioeconomic Consequences in Adult Life After Childhood Cancer in Scandinavia (SALiCCS) Research Programme

INTRODUCTION

The growing number of survivors of childhood cancer, with many years of life ahead, demonstrates the increasing clinical and public health relevance of investigating the risks of social and socioeconomic impairment after a childhood cancer diagnosis and the life-saving treatment. To enrich understanding of the mental, social and socioeconomic difficulties that childhood cancer survivors may face during their life-course, identify particularly vulnerable survivors and overcome the limitations of previous research, we initiated the Socioeconomic Consequences in Adult Life after Childhood Cancer in Scandinavia (SALiCCS) research programme.

METHODS

This Nordic cross-border research programme is a collaboration between the Danish Cancer Society, the Finnish Cancer Registry and Karolinska Institutet to investigate a broad range of mental, social and socioeconomic conditions in long-term childhood cancer survivors in Denmark, Finland and Sweden. SALiCCS is based on a registry-based matched cohort design, comprising five-year survivors of cancer diagnosed at ages 0-19 years (1971-2008 in Denmark, 1971-2009 in Finland, 1971-2011 in Sweden), age-, sex- and country-matched population comparisons and sibling comparisons who were followed over time. Outcomes of interest included mental disorders, educational achievements, employment and profession, family life and the need of social security benefits. Individual-level data linkage among various national registries provided the data for the research programme.

RESULTS

The SALiCCS core population comprises 21,292 five-year survivors, 103,303 population comparisons and 29,644 siblings as a second comparison group. The most common diagnoses in survivors were central nervous system tumours, leukaemias and lymphomas.

DISCUSSION

SALiCCS is the largest, most comprehensive population-based research initiative in this field, based on high-quality registry data with minimal risk of bias. The findings will be informative for evidence-based survivorship care targeting not only somatic late effects but also psychosocial impairments.

Migration, Gestational Diabetes, and Adverse Pregnancy Outcomes: A Nationwide Study of Singleton Deliveries in Denmark

CONTEXT

It remains unclear if migrants have different odds for adverse outcomes associated with gestational diabetes mellitus (GDM).

OBJECTIVE

We investigated if the associations between GDM and adverse pregnancy outcomes are modified by country of origin and examined the odds of these outcomes according to GDM status and country of origin.

METHODS

Data were extracted from a nationwide register-based study of singleton deliveries in Denmark, 2004-2015. We used logistic regression models and tested for interaction.

RESULTS

Among the 710 413 singleton deliveries, 2.6% had GDM and 14.4% were immigrants. Country of origin modified the association between GDM and pre-eclampsia, large for gestational age (LGA), and small for gestational age (SGA) but not between GDM and planned or emergency cesarean section and preterm delivery. GDM increased the risk of pre-eclampsia among women from Denmark (OR 1.28; 95% CI, 1.18-1.39), Lebanon (OR 3.34; 95% CI, 1.35-8.26), and Morocco (OR 2.28; 95% CI, 1.16-6.88). GDM was associated with increased odds of LGA among women from most countries, particularly women from Sri Lanka (OR 4.20; 95% CI, 2.67-6.61), and was associated with reduced odds of SGA in some countries. Compared with Danish-born women with GDM, the odds of LGA were significantly lower and the odds of SGA higher among women with GDM from India, Lebanon, Pakistan, Iraq, and Somalia.

CONCLUSIONS

Our study documents that different immigrant groups have higher odds of different GDM-associated adverse pregnancy outcomes and also among countries of origin often grouped together. This highlights the importance of increased awareness to both immigrant background and GDM status in the clinical assessment.

Use of antidepressants and risk of repeat self-harm in older adults 75+ with nonfatal self-harm: A 1-year prospective national study

PURPOSE

To assess exposure to antidepressants (AD) before and after nonfatal self-harm (SH) in older adults and to examine 1-year rates and risk factors for subsequent SH.

METHODS

Longitudinal national register-based retrospective cohort study of Swedish residents aged 75+ (N = 2775) with treatment at hospital or specialist outpatient clinic in connection with SH between January 1, 2006, and December 31, 2013. The cohort was followed for 1 year after the index episode. Exposure to AD was assessed at index and at subsequent SH. Cox regression analysis was used to assess factors associated with 1-year repeat SH.

RESULTS

At the index episode, 51% were prevalent AD users; 23% started AD during the following year. Overall 12% of prevalent AD users, 8% of AD nonusers, and 6% of AD new users repeated SH or died by suicide. About two-thirds of these subsequent behaviors occurred within 3 months after the index episode. Men had increased risk of subsequent SH (Hazard ratio [HR] 1.38, 95% CI: 1.09-1.74); older age (>85 years) was associated with a lower risk (HR 0.72, CI 95% 0.55-0.93). Users of AD did not have an increased risk of repeat SH.

CONCLUSIONS

Half of older adults who self-harmed were prevalent AD users and a further one fourth started an AD within 1 year after the index SH. Antidepressant use was not associated with increased risk of subsequent SH in this high-risk cohort of older adults.

Validity of Simple Algorithms to Identify Recurrence of Intracerebral Hemorrhage in Two Danish Nationwide Registries

Purpose

Danish registries could be an attractive resource for studies of recurrent intracerebral hemorrhage (re-ICH). We developed and validated algorithms to identify re-ICH in the Danish Stroke Registry (DSR) and the Danish National Patient Registry (DNPR).

Patients and Methods

Using multiple sources, we followed-up an inception cohort with verified first-ever spontaneous ICH (n = 2528) for their first re-ICH in 2009-2018 (study period). We used verified cases of re-ICH (n = 124) as the gold standard to assess the performance of register-based algorithms for identifying re-ICH. For each cohort member, we traced events of re-ICH (ICD-10-code I61) in the study period according to DSR and DNPR, respectively. For each registry, we tested algorithms with a blanking period (BP) - ie, a period immediately following the index ICH during which outcome events were ignored - of varying length (7 days-360 days). The algorithm with the shortest BP that returned a positive predictive value (PPV) of ≥80% was considered optimal. We also calculated negative predictive value (NPV), sensitivity, and specificity of each algorithm and [95% confidence intervals] for all proportions.

Results

The optimal algorithm for DSR (BP 30 days) had a PPV of 89.5% [82.2-94.0], NPV 98.8% [98.2-99.1], sensitivity 75.8% [67.6-82.5], and specificity 99.5% [99.2-99.7]. The optimal algorithm for DNPR (BP 120 days) had a PPV of 80.6% [71.7-87.2], NPV 98.1% [97.5-98.6], sensitivity 63.7% [55.0-71.6], and specificity 99.2% [98.8-99.5].

Conclusion

Simple algorithms accurately identified re-ICH in DSR and DNPR. Compared with DNPR, DSR achieved higher PPV and sensitivity with a shorter BP. The proposed algorithms could facilitate valid use of DSR and DNPR for studies of re-ICH.

Conduct Disorder in Immigrant Children and Adolescents: A Nationwide Cohort Study in Sweden

INTRODUCTION

Conduct disorder is a psychiatric diagnosis characterized by repetitive and persistent norm-breaking behavior. This study aimed to compare the risk of conduct disorder between first- and second-generation immigrant children and adolescents and their native controls.

METHODS

In this nationwide, open-cohort study from Sweden, participants were born 1987-2010, aged 4-16 years at baseline, and were living in the country for at least one year during the follow-up period between 2001 and 2015. The sample included 1,902,526 and 805,450 children-adolescents with native and immigrant backgrounds, respectively. Data on the conduct disorder diagnoses were retrieved through the National Patient Register. We estimated the incidence of conduct disorder and calculated adjusted Hazard Ratios.

RESULTS

Overall, the adjusted risk of conduct disorder was lower among first-generation immigrants and most second-generation immigrant groups compared with natives (both males and females). However, second-generation immigrants with a Swedish-born mother and a foreign-born father had a higher risk of conduct disorder than natives. Similar results were found for sub-diagnoses of conduct disorder.

CONCLUSIONS

The higher risk of conduct disorder among second-generation immigrants with a Swedish-born mother and the lower risk among most of the other immigrant groups warrants special attention and an investigation of potential underlying mechanisms.

Glycemic Control in Pregnancies Complicated by Pre-Existing Diabetes Mellitus and Congenital Malformations: A Danish Population-Based Study

Purpose

To study the occurrence of major congenital abnormalities in children of women with type 1 and type 2 diabetes and investigate the association between glycated haemoglobin (HbA1c) and major congenital malformations according to type 1 diabetes and type 2 diabetes separately.

Patients and methods

In this register-based study, all singletons born alive from January 1, 2000 to December 31, 2015 in the North Denmark and Central Denmark regions of Denmark and their mothers were included. We used data from Danish health registers and the LABKA database. Logistic regression models were used to compute crude and adjusted prevalence odds ratios (cORs and aORs) with 95% confidence intervals (CIs) for major congenital malformations overall and for subtypes, by type of maternal pre-existing diabetes and HbA1c levels.

Results

Among 314,245 infants included, 2020 (0.64%) had mothers with type 1 diabetes and 498 (0.16%) had mothers with type 2 diabetes. We found an aOR of 2.9 (95% CI: 2.5, 3.5) and 1.9 (95% CI: 1.3; 2.8) for major malformations for type 1 and type 2 diabetes, respectively. The highest occurrence was seen for major congenital heart diseases, but we also observed higher occurrence of several other non-cardiac malformations. For both type 1 and type 2 diabetes, the prevalence of major congenital malformations increased with higher levels of maternal HbA1c with no safe threshold level. Mothers with type 1 diabetes had higher risks than those without diabetes irrespective of HbA1c, and women with HbA1c levels ≥9.5% had 8 times the odds of major congenital malformations [aOR 8.7 (95% CI: 5.4; 14.5)].

Conclusions

The prevalence of major congenital malformations progressively increased with poorer glycemic control during pregnancy, with no obvious safe threshold level, for both type 1 and type 2 diabetes.

Comorbidity between types of eating disorder and general medical conditions

BACKGROUND

Comorbidity with general medical conditions is common in individuals with eating disorders. Many previous studies do not evaluate types of eating disorder.

AIMS

To provide relative and absolute risks of bidirectional associations between (a) anorexia nervosa, bulimia nervosa and eating disorders not otherwise specified and (b) 12 general medical conditions.

METHOD

We included all people born in Denmark between 1977 and 2010. We collected information on eating disorders and considered the risk of subsequent medical conditions, using Cox proportional hazards regression. Absolute risks were calculated using competing risks survival analyses. We also considered risks for prior medical conditions and subsequent eating disorders.

RESULTS

An increased risk was seen for almost all disorder pairs (69 of 70). Hazard ratios for those with a prior eating disorder receiving a subsequent diagnosis of a medical condition ranged from 0.94 (95% CI 0.57-1.55) to 2.05 (95% CI 1.86-2.27). For those with a prior medical condition, hazard ratios for later eating disorders ranged from 1.35 (95% CI 1.26-1.45) to 1.98 (95% CI 1.71-2.28). Absolute risks for most later disorders were increased for persons with prior disorders, compared with reference groups.

CONCLUSIONS

This is the largest and most detailed examination of eating disorder-medical condition comorbidity. The findings indicate that medical condition comorbidity is increased among those with eating disorders and vice versa. Although there was some variation in comorbidity observed across eating disorder types, magnitudes of relative risks did not differ greatly.

Maternal migraine and the risk of psychiatric disorders in offspring: a population-based cohort study

AIMS

Maternal migraine may contribute to mental heath problems in offspring but empirical evidence has been available only for bipolar disorders. Our objective was to examine the association between maternal migraine and the risk of any and specific psychiatric disorders in offspring.

METHODS

This population-based cohort study used individual-level linked Danish national health registers. Participants were all live-born singletons in Denmark during 1978-2012 (n = 2 069 785). Follow-up began at birth and continued until the onset of a psychiatric disorder, death, emigration or 31 December 2016, whichever came first. Cox proportional hazards model was employed to calculate the hazard ratios (HRs) of psychiatric disorders.

RESULTS

Maternal migraine was associated with a 26% increased risk of any psychiatric disorders in offspring [HR, 1.26; 95% confidence interval (CI), 1.22-1.30]. Increased rates of psychiatric disorders were seen in all age groups from childhood to early adulthood. Increased rates were also observed for most of the specific psychiatric disorders, in particular, mood disorders (HR, 1.53; 95% CI, 1.39-1.67), neurotic, stress-related and somatoform disorders (HR, 1.44; 95% CI, 1.37-1.52) and specific personality disorders (HR, 1.47; 95% CI, 1.27-1.70), but not for intellectual disability (HR, 0.84; 95% CI, 0.71-1.00) or eating disorders (HR, 1.10; 95% CI, 0.93-1.29). The highest risk was seen in the offspring of mothers with migraine and comorbid psychiatric disorders (HR, 2.13; 95% CI, 1.99-2.28).

CONCLUSIONS

Maternal migraine was associated with increased risks of a broad spectrum of psychiatric disorders in offspring. Given the high prevalence of migraine, our findings highlight the importance of better management of maternal migraine at childbearing ages for early prevention of psychiatric disorders in offspring.

Feeding and Eating Disorder and Risk of Subsequent Neurodevelopmental Disorders: A Population-Based Cohort Study

Background: There are limited data concerning the long-term mental health of children with feeding and eating disorder (FED). We aimed to investigate whether children with FED are at greater risks of developing emotional/behavioral disorders with onset usually during childhood, attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID). Methods: We conducted a population-based cohort study, including all singleton births in Denmark from January 1, 1995, to December 31, 2015. For each child diagnosed with FED, 10 age- and sex-matched controls who did not meet the criteria for FED were randomly selected from the general population. Associations were estimated with Cox regression modes adjusting for other perinatal and maternal factors, and sibling analyses were performed for controlling potential confounding by shared familial (genetic or environmental) factors. Results: Of the 1,256,989 individuals in the cohort, there were 1967 (53.4% girls) children diagnosed with FED. Children with FED had higher risks for clinically diagnosed emotional/behavioral disorders with onset usually in childhood (hazard ratio [HR], 2.78; 95% CI, 2.34-3.31), ADHD (HR, 1.74; 95% CI, 1.33-2.26), ASD (HR, 3.05; 95% CI, 2.36-3.94), and ID (HR, 6.38; 95% CI, 4.48-9.11), compared with matched controls. Girls with FED are at greater risks for emotional/behavioral disorders and ID, but not ADHD and ASD. Alike, in sibling analysis, increased rates are also observed for other neurodevelopmental disorders, but not for ADHD. Conclusion: Children with FED are associated with substantially increased risks of emotional/behavioral disorders, ADHD, ASD, and ID. This study highlights the importance of carefully monitoring neurodevelopmental disorders in children with FED.

The Validity of Intracerebral Hemorrhage Diagnoses in the Danish Patient Registry and the Danish Stroke Registry

Purpose

To establish the validity of intracerebral hemorrhage (ICH) diagnoses in the Danish Stroke Registry (DSR) and the Danish National Patient Registry (DNPR).

Patients and Methods

Based on discharge summaries and brain imaging reports, we estimated the positive predictive value (PPV) of a first-ever diagnosis code for ICH (ICD-10, code I61) for all patients in the Region of Southern Denmark (1.2 million) during 2009-2017 according to either DNPR or DSR. We estimated PPVs for any non-traumatic ICH (a-ICH) and spontaneous ICH (s-ICH) alone (ie, without underlying structural cause). We also calculated the sensitivity of these diagnoses in each of the registers. Finally, we classified the location of verified s-ICH.

Results

A total of 3,956 patients with ICH diagnosis codes were studied (DSR only: 87; DNPR only: 1,513; both registries: 2,356). In the DSR, the PPVs were 86.5% (95% CI=85.1-87.8) for a-ICH and 81.8% (95% CI=80.2-83.3) for s-ICH. The PPVs in DNPR (discharge code, primary diagnostic position) were 76.2% (95% CI=74.7-77.6) for a-ICH and 70.2% (95% CI=68.6-71.8) for s-ICH. Sensitivity for a-ICH and s-ICH was 76.4% (95% CI=74.8-78.0) and 78.7% (95% CI=77.1-80.2) in DSR, and 87.3% (95% CI=86.0-88.5) and 87.7% (95% CI=86.3-88.9) in DNPR. The location of verified s-ICH was lobar (39%), deep (33.6%), infratentorial (13.2%), large unclassifiable (11%), isolated intraventricular (1.9%), or unclassifiable due to insufficient information (1.3%).

Conclusion

The validity of a-ICH diagnoses is high in both registries. For s-ICH, PPV was higher in DSR, while sensitivity was higher in DNPR. The location of s-ICH was similar to distributions seen in other populations.

Depression among men in ART treatment: a register-based national cohort study

STUDY QUESTION

Are male factor infertility or remaining childless risk factors for unipolar depression among men in assisted reproductive technology (ART) treatment?

SUMMARY ANSWER

Male factor infertility was not associated with a significantly increased risk of unipolar depression and men remaining childless did not have a significantly increased risk of developing unipolar depression compared to men in ART treatment who became fathers.

WHAT IS KNOWN ALREADY

Men in medically assisted reproduction due to male factor infertility are more distressed and have more negative emotions such as feelings of loss, stigma and low self-esteem compared to men in fertility treatment due to other infertility diagnosis. Stress is in general a risk factor for depression. However, previous studies show conflicting results whether male factor infertility is a risk factor for depression.

STUDY DESIGN, SIZE, DURATION

This national, register-based cohort study consisted of 37 913 cohabitant male partners of women in ART treatment recorded in the Danish IVF register (1994–2009). Via a national register, the men’s personal identification number data were linked to the Danish Psychiatric Central Research Register (PCRR) (1969–2009) which records psychiatric diagnoses including unipolar depression, based on the ICD-8 and ICD-10 classification system.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The full cohort of male partners (n = 37 913) was included in the initial analysis on prevalence of unipolar depression before or after ART treatment initiation. The association between male factor infertility and unipolar depression diagnosis after initiating ART treatment was analysed with Cox regression analysis in a sub-study population of men with the exclusion of men having a depression prior to ART treatment or not having full data on educational level and infertility diagnosis (n = 34 817).

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, 1.2% (n = 446) of the men were diagnosed with unipolar depression either before initiating ART treatment (n = 146) or during follow-up (n = 300). In all, 76.0% of men with depression prior to or after ART treatment achieved fatherhood compared to 82.3% of men without depression (P < 0.001). In the sub-study population (n = 34 817, which included 266 men with a unipolar depression diagnosis), male factor infertility was not associated a significantly increased risk of depression (adjusted hazard ratio (aHR) = 1.04, 95% CI: 0.79–1.36, P = 0.804), and ART-treated men who remained childless did not have a significantly increased risk of developing depression compared to ART treated men who became fathers (aHR = 1.13, 95% CI: 0.87–1.48, P = 0.355).

LIMITATIONS, REASONS FOR CAUTIONS

Only severe cases of depression are recorded and included in this national register-based study given that only men with clinically diagnosed unipolar depression recorded in a psychiatric hospital (in-patient and out-patient) are included in the Danish PCRR. It is difficult to completely rule out an association between the exposures and depression as this outcome is so rare, and therefore the results are still statistically uncertain despite a large cohort. Furthermore, only men in ART treatment were included in this study, and caution should be taken in generalising findings to the total population of men in all areas of medically assisted reproduction or infertile men who have not sought treatment.

WIDER IMPLICATIONS OT THE FINDINGS

This large national cohort study suggests that despite evidence showing that male factor infertility is a potential severe stressor for men, which can increase psychological distress and negative emotions, infertile men in ART treatment and men remaining childless after ART are not at a significantly increased risk of developing clinically diagnosed unipolar depression.

STUDY FUNDING/COMPETING INTERESTS

C.S.S. was funded by unrestricted research grants received by Lone Schmidt from The Danish Health Insurance Foundation (J.nr. 2008B105) and Merck Sharp & Dohme (MSD). The sponsors had no influence on how data were retrieved and analysed or on the conclusions of the study. C.S.S. and L.S. have declared conflicts of interests; the remaining co-authors have no conflicts of interests to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

The rise and fall of an opt-out system

Introduction: In Denmark, citizens participate in register-based research without the possibility of opting out. However, in 1995 it was made possible for Danish citizens to register an opt-out called 'researcher protection' [forskerbeskyttelse], which implied that researchers could not contact people to invite them to participate in research projects, such as clinical trials or questionnaries, based on their registrations in national registers. Data already registered could still be used for research. In 2014, this possibility of opt-out was revoked by law. Aims: The aims of this paper are to understand how the Danish researcher protection system came about, why it was terminated and what we can we learn from this example. Methods: We conducted a descriptive analysis of a copy of the former researcher protection register along with policies and media debate surrounding the rise and revocation of the researcher protection system. Results: Our results show how both the inception and the abolishment of researcher protection appear to be ad hoc and without specified criteria of success. An examination of the recorded entries in the researcher protection registry could have led to changes in its administration as an alternative to its total abolition. Conclusions: In future opt-out systems, there should be focus on monitoring register practices and the purpose and criteria for evaluation must be defined prior to implementation.

Gestational Diabetes Risk in Migrants. A Nationwide, Register-Based Study of all Births in Denmark 2004 to 2015

BACKGROUND

Much remains to be understood about socioeconomic position and body mass index (BMI) in the pathways linking ethnicity, migration, and gestational diabetes mellitus (GDM). We investigated differences in GDM prevalence according to maternal country of origin and the role played by socioeconomic position and BMI on this relationship. Finally, we examined how length of residency was associated with GDM.

METHODS

A register-based cohort study of the 725 482 pregnancies that resulted in a birth in Denmark, 2004 to 2015. Of these, 14.4% were by women who had migrated to Denmark. A GDM diagnosis was registered in 19 386 (2.7%) pregnancies, of which 4464 (23.0%) were in immigrant women. The crude risk of GDM according to maternal country of origin compared to Danish-born women ranged from an odds ratio (OR) of 0.50 (95% CI 0.34-0.71) for women from Sweden to an OR of 5.11 (95% CI 4.28-6.11) for women from Sri Lanka. Adjustment for socioeconomic position slightly attenuated the risks. Adjusting for BMI resulted in increased ORs for women, especially from Asian countries. The separate and joint effects of migration and overweight on GDM risk differed substantially between the countries of origin (P value interaction term < .001). Immigrants with 10 or more years of residency had a 56% increased risk of GDM (OR 1.56, 95% CI 1.44-1.68) compared to immigrants with less than 5 years in Denmark. This risk was somewhat diluted when adjusting for age and BMI.

CONCLUSIONS

This study demonstrates substantial variation in the risk of GDM according to country of origin. The risk associations are only slightly affected by socioeconomic position and BMI.

The Danish Twin Registry: An Updated Overview

The Danish Twin Registry (DTR) was established in the 1950s, when twins born from 1870 to 1910 were ascertained, and has since been extended to include twins from birth cohorts until 2009. The DTR currently comprises of more than 175,000 twins from the 140 birth cohorts. This makes the DTR the oldest nationwide twin register and among the largest in the world. The combination of data from several surveys, including biological samples and repeated measurements on the same individuals, and data from Danish national registers provides a unique resource for a wide range of twin studies. This article provides an updated overview of the data in the DTR: First, we provide a summary of the establishment of the register, the different ascertainment methods and the twins included; then follows an overview of major surveys conducted in the DTR since 1994 and a description of the DTR biobank, including a description of the molecular data created so far; finally, a short description is given of the linkage to Danish national registers at Statistics Denmark and some recent examples of studies using the various data resources in the DTR are highlighted.

Cohort profile: the Swedish Prescribed Drugs and Health Cohort (SPREDH)

PURPOSE

The Swedish Prescribed Drugs and Health Cohort (SPREDH) is a Swedish population-based cohort based on data from four nationwide health data registers, created with the aim of investigating how the use of selected medications influences cancer risk and other outcomes.

PARTICIPANTS

The cohort includes 8 421 115 users of selected common medications who have been followed-up for a total of 82 281 720 person-years from 1 July 2005 to 31 December 2015.

FINDING TO DATE

The data in SPREDH were prospectively collected from the following national health data registers in Sweden: Prescribed Drug Register, Patient Register, Cancer Register and Causes of Death Register. Data on basic patient characteristics, use of the selected common medications, healthcare utilisation, diagnoses (including detailed information on cancers), and dates and causes of death are available for all cohort participants. The cohort currently includes 801 766 incident cancer cases.

FUTURE PLANS

The data in SPREDH can be used for various types of epidemiological research, particularly for examining how the use of the selected medications influences disease risk and other outcomes. We are initially planning cohort studies and nested case-control studies on selected medications in relation to the risk and prognosis of oesophageal and gastric cancers.

Mental and behavioural disorders in the children of mothers diagnosed with cancer: A Danish population-based register study

OBJECTIVE

Maternal cancer may be associated with offspring mental and behavioural disorders through various biological pathways. When postnatally diagnosed, it may cause stress and changes in care, potentially influencing mental health. Prenatally diagnosed cancer could lead to maternal stress and treatment, or influence foetal neural development. This study investigates associations between prenatally or postnatally diagnosed maternal cancers and mental and behavioural disorders in children.

METHODS

The study composed of 2 158 430 children born in Denmark (1978-2012). Children were exposed if their mother received a cancer diagnosis prenatally (2 years prepartum, until birth) or postnatally (birth, until 18 years postpartum). Further analyses considered cancer types and diagnostic delays. Children were followed until 18 years of age or the first of the following: diagnosis of a mental or behavioural disorder, emigration, death, end of follow-up.

RESULTS

During follow-up 79 682 (3.7%) children were diagnosed with mental or behavioural disorders. There was an increased risk among offspring exposed to postnatally diagnosed cancers (HR 1.05; 95% CI, 1.00-1.11); for prenatally diagnosed cancers HR was 1.07 (0.87-1.31). The strongest associations for disorder types were for prenatal diagnoses with mood/affective disorders (HR 2.45; 1.02-5.89) and postnatal diagnoses with mood/affective disorders (HR 1.43; 1.14-1.79).

CONCLUSIONS

The results indicate a link between maternal cancer occurrence during pregnancy or early postnatal life, and mental and behavioural disorders in offspring. This association could be driven by common factors in the two periods, such as psychological stress or genetic factors. No specific foetal programming was identified.

Intracerebral hemorrhage: positive predictive value of diagnosis codes in two nationwide Danish registries

Purpose

The purpose of this study is to establish the validity of intracerebral hemorrhage (ICH) diagnoses in the Danish Stroke Registry (DSR) and the Danish National Patient Registry (DNPR).

Patients and methods

We estimated the positive predictive value (PPV) of ICH diagnoses for a sample of 500 patients from the DSR (patients recorded under ICH diagnosis) and DNPR (International Classification of Diseases, version 10, code I61) during 2010–2015, using discharge summaries and brain imaging reports (minimal data). We estimated PPVs for any ICH (a-ICH) and spontaneous ICH (s-ICH) alone. Furthermore, we assessed PPVs according to whether patients were recorded in both or only one of the registries. Finally, in a subsample with ICH diagnoses with access to full medical records and original imaging studies (extensive data, n=100), we compared s-ICH diagnosis and hemorrhage location after use of extensive vs minimal data.

Results

In the DSR, the PPVs were 94% (95% CI, 91%–96%) for a-ICH and 85% (95% CI, 81%–88%) for s-ICH. In the DNPR, the PPVs were 88% (95% CI, 84%–91%) for a-ICH and 75% (95% CI, 70%–79%) for s-ICH. PPVs for s-ICH for patients recorded in both registries, DSR only, and DNPR only were 86% (95% CI, 82–99), 80% (95%CI, 71–87), and 49% (95%CI, 39–59), respectively. Evaluation of extensive vs minimal data verified s-ICH diagnosis in 98% and hemorrhage location in 94%.

Conclusion

The validity of a-ICH diagnoses in DSR and DNPR is sufficiently high to support their use in epidemiologic studies. For s-ICH, validity was high in DSR. In DNPR, s-ICH validity was lower, markedly so for the small subgroup of patients only recorded in this registry. Minimal data including discharge summaries and brain imaging reports were feasible and valid for identifying ICH location.

The validity of register data to identify children with atopic dermatitis, asthma or allergic rhinoconjunctivitis

BACKGROUND

The incidence of atopic dermatitis, wheezing, asthma and allergic rhinoconjunctivitis has been increasing. Register-based studies are essential for research in subpopulations with specific diseases and facilitate epidemiological studies to identify causes and evaluate interventions. Algorithms have been developed to identify children with atopic dermatitis, asthma or allergic rhinoconjunctivitis using register information on disease-specific dispensed prescribed medication and hospital contacts, but the validity of the algorithms has not been evaluated. This study validated the algorithms vs gold standard deep telephone interviews with the caretaker about physician-diagnosed atopic dermatitis, wheezing, asthma or allergic rhinoconjunctivitis in the child.

METHODS

The algorithms defined each of the three atopic diseases using register-based information on disease-specific hospital contacts and/or filled prescriptions of disease-specific medication. Confirmative answers to questions about physician-diagnosed atopic disease were used as the gold standard for the comparison with the algorithms, resulting in sensitivities and specificities and 95% confidence intervals. The interviews with the caretaker of the included 454 Danish children born 1997-2003 were carried out May-September 2015; the mean age of the children at the time of the interview being 15.2 years (standard deviation 1.3 years).

RESULTS

For the algorithm capturing children with atopic dermatitis, the sensitivity was 74.1% (95% confidence interval: 66.9%-80.2%) and the specificity 73.0% (67.3%-78.0%). For the algorithm capturing children with asthma, both the sensitivity of 84.1% (78.0%-88.8%) and the specificity of 81.6% (76.5%-85.8%) were high compared with physician-diagnosed asthmatic bronchitis (recurrent wheezing). The sensitivity remained high when capturing physician-diagnosed asthma: 83.3% (74.3%-89.6%); however, the specificity declined to 66.0% (60.9%-70.8%). For allergic rhinoconjunctivitis, the sensitivity was 84.4% (78.0-89.2) and the specificity 81.6% (75.0-84.4).

CONCLUSION

The algorithms are valid and valuable tools to identify children with atopic dermatitis, wheezing, asthma or allergic rhinoconjunctivitis on a population level using register data.

Cognitive ability and risk for substance misuse in men: genetic and environmental correlations in a longitudinal nation-wide family study

AIMS

To investigate the association in males between cognitive ability in late adolescence and subsequent substance misuse-related events, and to study the underlying genetic and environmental correlations.

DESIGN

A population-based longitudinal study with three different family-based designs. Cox proportional hazards models were conducted to investigate the association at the individual level. Bivariate quantitative genetic modelling in (1) full brothers and maternal half-brothers, (2) full brothers reared together and apart and (3) monozygotic and dizygotic twin brothers was used to estimate genetic and environmental correlations.

SETTING

Register-based study in Sweden.

PARTICIPANTS

The full sample included 1 402 333 Swedish men born 1958-91 and conscripted at mean age 18.2 [standard deviation (SD) = 0.5] years. A total of 1 361 066 men who had no substance misuse events before cognitive assessment at mandatory military conscription were included in the Cox regression models, with a follow-up time of up to 35.6 years.

MEASURES

Cognitive ability was assessed at conscription with the Swedish Enlistment Battery. Substance misuse events included alcohol- and drug-related court convictions, medical treatments and deaths, available from governmental registries.

FINDINGS

Lower cognitive ability in late adolescence predicted an increased risk for substance misuse events [hazard ratio (HR) for a 1-stanine unit decrease in cognitive ability: 1.29, 95% confidence interval (CI) = 1.29-1.30]. The association was somewhat attenuated within clusters of full brothers (HR = 1.21, 95% CI = 1.20-1.23). Quantitative genetic analyses indicated that the association was due primarily to genetic influences; the genetic correlations ranged between -0.39 (95% CI = -0.45, -0.34) and -0.52 (95% CI -0.55, -0.48) in the three different designs.

CONCLUSIONS

Shared genetic influences appear to underlie the association between low cognitive ability and subsequent risk for substance misuse events among Swedish men.

Parental history of psychiatric diagnoses and unipolar depression: a Danish National Register-based cohort study

BACKGROUND

Depression is known to run in families, but the effects of parental history of other psychiatric diagnoses on depression rates are less well studied. Few studies have examined the impact of parental psychopathology on depression rates in older age groups.

METHOD

We established a population-based cohort including all individuals born in Denmark after 1954 and alive on their 10th birthday (N = 29 76 264). Exposure variables were maternal and paternal history of schizophrenia, bipolar disorder, depression, anxiety or 'other' psychiatric diagnoses. Incidence rate ratios (IRRs) were estimated using Poisson regressions.

RESULTS

Parental history of any psychiatric diagnosis increased incidence rates of outpatient (maternal: IRR 1.88, p < 0.0001; paternal: IRR 1.68, p < 0.0001) and inpatient (maternal: IRR 1.99, p < 0.0001; paternal: IRR 1.83, p < 0.0001) depression relative to no parental history. IRRs for parental history of non-affective disorders remained relatively stable across age groups, while IRRs for parental affective disorders (unipolar or bipolar) decreased with age from 2.29-3.96 in the youngest age group to 1.53-1.90 in the oldest group. IRR estimates for all parental diagnoses were similar among individuals aged ⩾41 years (IRR range 1.51-1.90).

CONCLUSIONS

Parental history of any psychiatric diagnosis is associated with increased incidence rates of unipolar depression. In younger age groups, parental history of affective diagnoses is more strongly associated with rates of unipolar depression than non-affective diagnoses; however, this distinction disappears after age 40, suggesting that parental psychopathology in general, rather than any one disorder, confers risk for depression in middle life.

Undertreatment of osteoporosis in the oldest old? A nationwide study of over 700,000 older people

SUMMARY: We analysed data from elderly people registered in the Swedish Prescribed Drug Register to investigate whether age is associated with use of osteoporosis drugs in a nationwide population. Our results indicate an undertreatment of osteoporosis, particularly with bisphosphonates, in the oldest old in Sweden. INTRODUCTION: The aim of this study was to investigate whether age is associated with use of osteoporosis drugs in a large population of older people. METHODS: We analysed data on age, sex, type of residential area (urban/rural) and dispensed drugs for people aged >/=75 years registered in the Swedish Prescribed Drug Register from October to December 2005 (n = 731,105). Multivariate logistic regression was used to analyse whether age was associated with use of osteoporosis drugs, after adjustment for type of residential area and number of other drugs (a proxy for comorbidity). RESULTS: Osteoporosis drugs were used by 16.1% of the women and 3.4% of the men. The probability of use of bisphosphonates declined with increasing age [ORwomen = 0.36 (95% CI 0.34-0.38) and ORmen = 0.46 (95% CI 0.37-0.56) for age >/=90 years vs. 75-79 years]. Raloxifene was also negatively associated with age. Calcium + vitamin D supplements, however, showed a divergent pattern regarding age. In women, the lowest likelihood of use of calcium + vitamin D supplements occurred in the oldest old (>/=90 years). CONCLUSIONS: Our results indicate an undertreatment of osteoporosis, particularly with bisphosphonates, in the oldest old in Sweden. Future research is needed for understanding the mechanisms behind this age effect.