Associations between pregnancy-related factors and birth characteristics with risk of rare uterine cancer subtypes: a Nordic population-based case-control study

PURPOSE

Uterine sarcomas are a rare group of uterine malignancies. Due to the low incidence and changes in uterine sarcoma classification, risk factors are not well characterized. Our objective was to evaluate risk factors for uterine sarcoma and compare risk factors between uterine sarcoma, malignant mixed Mullerian tumors (MMMTs), and type I endometrial carcinomas.

METHODS

This nested case-control study utilized linked data from population-based medical birth and cancer registries in Denmark, Finland, Norway, and Sweden. Up to 10 controls were matched on country and birth year for each uterine cancer case. Using multivariable adjusted multinomial logistic regression, estimates of the associations between pregnancy-related factors and risk of uterine sarcoma, MMMTs, and type I endometrial carcinomas were determined.

RESULTS

Having a very-low-birth-weight infant (< 1500 vs. 2500-3999 g: OR [95% CI] 2.83 [1.61-4.96]) was associated with an increased risk of uterine sarcoma. Whereas, having a more recent pregnancy was associated with reduced risks of MMMT (< 10 vs. ≥ 30 years: 0.66 [0.20-2.23]) and type 1 endometrial carcinomas (0.35 [0.30-0.41]) but not uterine sarcomas (1.33 [0.90-1.98], p-heterogeneity < 0.01).

CONCLUSION

Our study provides evidence that risk factors for uterine sarcoma and MMMT, previously grouped with uterine sarcomas, vary substantially. Additionally, MMMT and type I endometrial carcinomas are more similar than uterine sarcoma in that pregnancy complications like gestational hypertension and preeclampsia were associated with reduced risks of both but not uterine sarcoma, suggesting different etiologies.

Incidence trends of adult glioma in Norway and its association with occupation and education: A registry-based cohort study

BACKGROUND

Gliomas constitute 75 % of all malignant primary adult brain tumors. Being the most frequent histologic subtype, glioblastomas (GBMs) cause substantial morbidity and mortality worldwide and the Nordic countries have some of the highest incidence rates in the world. Therefore, we investigated the incidence of gliomas in Norway including time trends and associations with education and occupation.

METHODS

We retrieved individual-level data from databases at Statistics Norway containing information on education and occupation and linked them to data on adult glioma patients diagnosed during 2004-21 from the Cancer Registry of Norway. Age-standardized incidence rates (ASIRs) (World Standard Population) were calculated and analyzed with regards to sex and morphology. Poisson regression was used to test for time-trends, and to analyze the associations between education, occupation and glioma incidence, adjusted for age, sex, and calendar year. Estimates were reported as incidence rate ratios (IRRs) with 95 % confidence intervals (CIs).

RESULTS

The overall ASIR of gliomas (per 100,000 person-years) was 7.1 (95 % CI 6.9-7.3), with no specific time trend during the study period. The incidence increased with age. Compared to the other subtypes, GBMs were diagnosed at older ages. The risks of developing glioma overall and GBM were associated with occupation but not with educational level. The relative risk of glioma and GBM were respectively 1.17 (95 % CI 1.05-1.31) and 1.17 (95 % CI 1.02-1.35) among high-skilled white-collar workers compared to blue-collar workers.

CONCLUSIONS

The overall and sex-specific ASIRs of gliomas and GBMs did not show any noticeable time trends. The higher risk of developing glioma overall and GBM in high-skilled white-collar workers compared to blue-collar workers calls for further investigations.

Body mass index, triglyceride-glucose index, and prostate cancer death: a mediation analysis in eight European cohorts

BACKGROUND

Insulin resistance is a hypothesised biological mechanism linking obesity with prostate cancer (PCa) death. Data in support of this hypothesis is limited.

METHODS

We included 259,884 men from eight European cohorts, with 11,760 incident PCa's and 1784 PCa deaths during follow-up. We used the triglyceride-glucose (TyG) index as indicator of insulin resistance. We analysed PCa cases with follow-up from PCa diagnosis, and the full cohort with follow-up from the baseline cancer-free state, thus incorporating both PCa incidence and death. We calculated hazard ratios (HR) and the proportion of the total effect of body mass index (BMI) on PCa death mediated through TyG index.

RESULTS

In the PCa-case-only analysis, baseline TyG index was positively associated with PCa death (HR per 1-standard deviation: 1.11, 95% confidence interval (CI); 1.01-1.22), and mediated a substantial proportion of the baseline BMI effect on PCa death (HRtotal effect per 5-kg/m2 BMI: 1.24; 1.14-1.35, of which 28%; 4%-52%, mediated). In contrast, in the full cohort, the TyG index was not associated with PCa death (HR: 1.03; 0.94-1.13), hence did not substantially mediate the effect of BMI on PCa death.

CONCLUSIONS

Insulin resistance could be an important pathway through which obesity accelerates PCa progression to death.

ADHD medication discontinuation and persistence across the lifespan: a retrospective observational study using population-based databases

BACKGROUND

Although often intended for long-term treatment, discontinuation of medication for ADHD is common. However, cross-national estimates of discontinuation are missing due to the absence of standardised measures. The aim of this study was to determine the rate of ADHD treatment discontinuation across the lifespan and to describe similarities and differences across countries to guide clinical practice.

METHODS

We did a retrospective, observational study using population-based databases from eight countries and one Special Administrative Region (Australia, Denmark, Hong Kong, Iceland, the Netherlands, Norway, Sweden, the UK, and the USA). We used a common analytical protocol approach and extracted prescription data to identify new users of ADHD medication. Eligible individuals were aged 3 years or older who had initiated ADHD medication between 2010 and 2020. We estimated treatment discontinuation and persistence in the 5 years after treatment initiation, stratified by age at initiation (children [age 4-11 years], adolescents [age 12-17 years], young adults [age 18-24 years], and adults [age ≥25 years]) and sex. Ethnicity data were not available.

FINDINGS

1 229 972 individuals (735 503 [60%] males, 494 469 females [40%]; median age 8-21 years) were included in the study. Across countries, treatment discontinuation 1-5 years after initiation was lowest in children, and highest in young adults and adolescents. Within 1 year of initiation, 65% (95% CI 60-70) of children, 47% (43-51) of adolescents, 39% (36-42) of young adults, and 48% (44-52) of adults remained on treatment. The proportion of patients discontinuing was highest between age 18 and 19 years. Treatment persistence for up to 5 years was higher across countries when accounting for reinitiation of medication; at 5 years of follow-up, 50-60% of children and 30-40% of adolescents and adults were covered by treatment in most countries. Patterns were similar across sex.

INTERPRETATION

Early medication discontinuation is prevalent in ADHD treatment, particularly among young adults. Although reinitiation of medication is common, treatment persistence in adolescents and young adults is lower than expected based on previous estimates of ADHD symptom persistence in these age groups. This study highlights the scope of medication treatment discontinuation and persistence in ADHD across the lifespan and provides new knowledge about long-term ADHD medication use.

FUNDING

European Union Horizon 2020 Research and Innovation Programme.

Cancer risk in the siblings of individuals with major birth defects: a large Nordic population-based case-control study

BACKGROUND

Individuals with major birth defects are at increased risk of developing cancer, indicating a common aetiology. However, whether the siblings of individuals with birth defects are also at an increased risk of cancer is unclear.

METHODS

We used nationwide health registries in four Nordic countries and conducted a nested case-control study. We included 40 538 cancer cases (aged 0-46 years) and 481 945 population controls (matched by birth year and country), born between 1967 and 2014. The relative risk of cancer among individuals whose siblings had birth defects was computed with odds ratios (OR) and 95% confidence intervals (CIs), using logistic regression models.

RESULTS

In the total study population (aged 0-46 years), we observed no overall difference in cancer risk between individuals whose siblings had birth defects and those who had unaffected siblings (OR 1.02; 95% CI 0.97-1.08); however, the risk of lymphoid and haematopoietic malignancies was elevated (1.16; 1.05-1.28). The overall risk of childhood cancer (0-19 years) was increased for siblings of individuals who had birth defects (1.09; 1.00-1.19), which was mainly driven by lymphoma (1.35; 1.09-1.66), neuroblastoma (1.51; 1.11-2.05) and renal carcinoma (5.03; 1.73-14.6). The risk of cancer also increased with the number of siblings with birth defects (Ptrend = 0.008).

CONCLUSION

Overall risk of cancer among individuals (aged 0-46 years) whose siblings had birth defects was not elevated, but the risk of childhood cancer (ages 0-19 years) was increased. Our novel findings are consistent with the common aetiologies of birth defects and cancer, such as shared genetic predisposition and environmental factors.

Fetal Exposure to Preeclampsia and Later Risk of Cardiometabolic Disorders: A Population-Based Cohort Study

BACKGROUND

Fetal preeclampsia exposure has been associated with later cardiometabolic disease. However, this association has been investigated in few large population-wide studies, and it is unknown whether the association represents a causal relationship or is the result of shared etiological factors.

METHODS

To further investigate the relationship between preeclampsia exposure and later cardiometabolic disease, we identified 1 692 944 singleton infants born in Norway during 1967 to 1997, where 44 299 were exposed to preeclampsia in utero. The individuals were followed for hypertension, diabetes, and dyslipidemia as defined by dispensed medication. We used Cox regression models to calculate the association between preeclampsia exposure and cardiometabolic outcomes adjusting for measured confounders. We also used full sibling comparisons and stratified Cox regression to control for unmeasured familial confounders.

RESULTS

On the population level, exposed individuals had increased risk of hypertension (adjusted hazard ratio [aHR] 1.51 [95% CI, 1.41-1.63]), diabetes (aHR 1.33 [95% CI, 1.24-1.43], and dyslipidemia (aHR 1.28 [95% CI, 1.13-1.45]) compared with unexposed individuals. In sibling data, individuals not exposed to preeclampsia, but with an exposed sibling, had higher risk of hypertension and diabetes than individuals where no siblings were exposed to preeclampsia. Moreover, when comparing siblings discordant on preeclampsia exposure, there were no associations between preeclampsia and hypertension (aHR 1.05 [95% CI, 0.88-1.26]), diabetes (aHR 0.96 [95% CI, 0.80-1.14]), and dyslipidemia (aHR 0.86 [95% CI, 0.62-1.20]).

CONCLUSIONS

Fetal preeclampsia exposure was associated with adult life hypertension, diabetes, and dyslipidemia, but these associations were likely due to shared etiological factors, rather than exposure to the preeclamptic condition itself.

Metformin Versus Insulin and Risk of Major Congenital Malformations in Pregnancies With Type 2 Diabetes: A Nordic Register-Based Cohort Study

OBJECTIVE

To assess the risk of major congenital malformations with metformin versus insulin in pregnancies with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This cohort study used four Nordic countries' nationwide registers of live and stillborn infants exposed to metformin or insulin during first trimester organogenesis. Main exclusion criteria were type 1 diabetes, polycystic ovary syndrome, fertility treatment, and exposure to other diabetes drugs. Adjusted risk ratios (RRs) and 95% CIs were estimated for any and cardiac malformations.

RESULTS

Of 3,734,125 infants in the source population, 25,956 were exposed to metformin or insulin in the first trimester, and 4,023 singleton infants were included. A malformation was diagnosed in 147 (4.7%) of 3,145 infants with exposure to any metformin (alone or in addition to insulin) and 50 (5.7%) of 878 infants with exposure to insulin alone (RR 0.84, 95% CI 0.46-1.54). Among 2,852 infants exposed to metformin alone and 293 infants exposed to metformin in addition to insulin 127 (4.4%) and 20 (6.8%), respectively, had a malformation. The adjusted risk was not increased for either metformin alone (0.83, 0.44-1.58) or both metformin and insulin (0.98, 0.56-1.69) versus insulin alone. Corresponding RRs for cardiac malformations were 1.01 (0.55-1.84) for any metformin, 0.92 (0.47-1.81) for metformin alone, and 1.72 (0.76-3.91) for both metformin and insulin.

CONCLUSIONS

No evidence of an increased malformation risk with metformin versus insulin in the first trimester was found. Results should be interpreted with caution since information on glycemic control was missing.

Comparative Safety of Antiseizure Medication Monotherapy for Major Malformations

OBJECTIVE

This study was undertaken to examine the comparative safety of antiseizure medication (ASM) monotherapy in pregnancy with respect to risk of major congenital malformations (MCMs), overall and by MCM subtype.

METHODS

We conducted a population-based cohort study using national health register data from Denmark, Finland, Iceland, Norway, and Sweden (1996-2020). We compared pregnancies with first trimester exposure to lamotrigine monotherapy to ASM-unexposed, carbamazepine, valproate, oxcarbazepine, levetiracetam, and topiramate to lamotrigine monotherapy, and stratified monotherapy groups by dose. The outcome was nongenetic MCM and specific subtypes. We estimated adjusted risk ratios (aRRs) and 95% confidence intervals (CIs) with log-binomial regression and propensity score weights.

RESULTS

There was a higher crude risk of any MCM in pregnancies exposed to lamotrigine monotherapy (n = 8,339) compared to ASM-unexposed pregnancies (n = 4,866,362), but not after confounder adjustment (aRR = 0.97, 95% CI = 0.87-1.08). Compared to lamotrigine, there was an increased risk of malformations associated with valproate (n = 2,031, aRR = 2.05, 95% CI = 1.70-2.46) and topiramate (n = 509, aRR = 1.81, 95% CI = 1.26-2.60), which increased in a dose-dependent manner. We found no differences in malformation risk for carbamazepine (n = 2,674, aRR = 0.91, 95% CI = 0.72-1.15), oxcarbazepine (n = 1,313, aRR = 1.09, 95% CI = 0.83-1.44), or levetiracetam (n = 1,040, aRR = 0.78, 95% CI = 0.53-1.13). Valproate was associated with several malformation subtypes, including nervous system, cardiac, oral clefts, clubfoot, and hypospadias, whereas lamotrigine and carbamazepine were not.

INTERPRETATION

Topiramate is associated with an increased risk of MCM similar to that associated with valproate, but lower doses may mitigate the risks for both drugs. Conversely, we found no increased risks for lamotrigine, carbamazepine, oxcarbazepine, or levetiracetam, which is reassuring. ANN NEUROL 2023;93:551-562.

Labor epidural analgesia and subsequent risk of offspring autism spectrum disorder and attention-deficit/hyperactivity disorder: a cross-national cohort study of 4.5 million individuals and their siblings

BACKGROUND

A recent study has suggested that labor epidural analgesia may be associated with increased rates of offspring autism spectrum disorder. Subsequent replication attempts have lacked sufficient power to confidently exclude the possibility of a small effect, and the causal nature of this association remains unknown.

OBJECTIVE

This study aimed to investigate the extent to which exposure to labor epidural analgesia is associated with offspring autism spectrum disorder and attention-deficit/hyperactivity disorder following adjustments for unmeasured familial confounding.

STUDY DESIGN

We identified 4,498,462 singletons and their parents using the Medical Birth Registers in Finland (cohorts born from 1987-2005), Norway (1999-2015), and Sweden (1987-2011) linked with population and patient registries. These cohorts were followed from birth until they either had the outcomes of interest, emigrated, died, or reached the end of the follow-up (at mean ages 13.6-16.8 years), whichever occurred first. Cox regression models were used to estimate country-specific associations between labor epidural analgesia recorded at birth and outcomes (eg, at least 1 secondary care diagnosis of autism spectrum disorder and attention-deficit/hyperactivity disorder or at least 1 dispensed prescription of medication used for the treatment of attention-deficit/hyperactivity disorder). The models were adjusted for sex, birth year, birth order, and unmeasured familial confounders via sibling comparisons. Pooled estimates across all the 3 countries were estimated using inverse variance weighted fixed-effects meta-analysis models.

RESULTS

A total of 4,498,462 individuals (48.7% female) were included, 1,091,846 (24.3%) of which were exposed to labor epidural analgesia. Of these, 1.2% were diagnosed with autism spectrum disorder and 4.0% with attention-deficit/hyperactivity disorder. On the population level, pooled estimates showed that labor epidural analgesia was associated with increased risk of offspring autism spectrum disorder (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.14, absolute risks, 1.20% vs 1.07%) and attention-deficit/hyperactivity disorder (adjusted hazard ratio, 1.20; 95% confidence interval, 1.19-1.21; absolute risks, 3.95% vs 3.32%). However, when comparing full siblings who were differentially exposed to labor epidural analgesia, the associations were fully attenuated for both conditions with narrow confidence intervals (adjusted hazard ratio [autism spectrum disorder], 0.98; 95% confidence interval, 0.93-1.03; adjusted hazard ratio attention-deficit/hyperactivity disorder, 0.99; 95% confidence interval, 0.96-1.02).

CONCLUSION

In this large cross-national study, we found no support for the hypothesis that exposure to labor epidural analgesia causes either offspring autism spectrum disorder or attention-deficit/hyperactivity disorder.

Incidence and prevalence of drugs used for chronic diseases in survivors of adult-onset gynaecological cancer - A nationwide cohort study

OBJECTIVES

To evaluate both incidence and prevalence of drugs used for chronic diseases in survivors of adult-onset gynaecological cancer.

DESIGN

A prospective study.

SETTING

Population-based registries.

POPULATION

1.76 million women, including 17 500 women with gynaecological cancers.

METHODS

Data from the Cancer Registry of Norway was linked to the Norwegian Prescription Database and other national databases.

MAIN OUTCOME MEASURES

Prevalence ratios (PRs) and hazard ratios (HRs), with 95% confidence intervals (CIs), of dispensed drugs in gynaecological cancer patients (up to 15 years after diagnosis) were estimated by log-binomial and Cox regression, respectively, with cancer-free women as reference.

RESULTS

For gynaecological cancer patients, the incidence of drugs used for pain control was higher than in cancer-free women, especially the first 5 years after diagnosis, and the prevalence was high at least 10 years after. The prevalence of sex hormones was high in women with gynaecological cancer at least 10 years after diagnosis (cervical and ovarian cancer PR = 23, 95% CI 18-30 and PR = 29, 95% CI 15-38, respectively), but low in cancer-free women (0.3%). Patients with uterine corpus cancer had a higher prevalence of antidiabetics before and at least 10 years after diagnosis, most pronounced in women diagnosed before age 50 (PR = 10, 95% CI 5.0-21). The prevalence of antidepressants was moderately elevated in women with gynaecological cancers.

CONCLUSIONS

Gynaecological cancer survivors, particularly cervical and ovarian cancer survivors, had an increased long-term use of drugs for pain control and sex hormones. Survivors of uterine corpus cancer used antidiabetics more often, both before and after diagnosis.

Metabolically (un)healthy obesity and risk of obesity-related cancers: a pooled study

BACKGROUND

Studies of obesity with or without metabolic aberrations, commonly termed metabolically unhealthy or healthy obesity, in relation to cancer risk are scarce.

METHODS

We investigated body mass index (BMI, normal weight/overweight/obesity) jointly and in interaction with metabolic health status in relation to obesity-related cancer risk (n = 23,630) among 797,193 European individuals. A metabolic score comprising mid-blood pressure, plasma glucose and triglycerides was used to define metabolically healthy and unhealthy status. Hazard ratios (HRs) and multiplicative interactions were assessed using Cox regression, and additive interactions were assessed using the relative excess risk for interaction. All statistical tests were two-sided.

RESULTS

Metabolically unhealthy obesity, with a baseline prevalence of 7%, was, compared to metabolically healthy normal weight, associated with an increased relative risk of any obesity-related cancer and of colon, rectal, pancreas, endometrial, liver, gallbladder, and renal cell cancer (p < 0.05), with the highest risk estimates for endometrial, liver, and renal cell cancer (HRs, 2.55 to 3.00). Metabolically healthy obesity showed a higher relative risk for any obesity-related cancer and colon (in men), endometrial, renal cell, liver, and gallbladder cancer, though the risk relationships were weaker. There were no multiplicative interactions, but there were additive, positive interactions between BMI and metabolic health status on obesity-related and rectal cancer among men, and on endometrial cancer (p < 0.05).

CONCLUSIONS

This study highlights that the type of metabolic obesity phenotype is important when assessing obesity-related cancer risk. In general, metabolic aberrations further increased the obesity-induced cancer risk, suggesting that both obesity and metabolic aberrations are useful targets for prevention.

Atomoxetine in Early Pregnancy and the Prevalence of Major Congenital Malformations: A Multinational Study

Objective: Most research on safety of attention-deficit/hyperactivity disorder (ADHD) medications during pregnancy concerns central nervous system stimulants, while little is known about the safety of atomoxetine, a primary treatment alternative. We assessed the prevalence of major congenital malformations overall, and cardiac malformations and limb malformations specifically, after first-trimester exposure. Methods: In this cohort study, we included all approximately 2.4 million pregnancies ending in live births recorded in the population-based nationwide health registers of Denmark, Iceland, Norway, and Sweden (2003-2017) and approximately 1.8 million publicly insured pregnancies ending in live births recorded in the US Medicaid Analytic eXtract (MAX, 2001-2013) health care claims database. We compared the prevalence of major congenital malformations in the newborn among pregnancies exposed and unexposed to atomoxetine. For each country, we calculated prevalence ratios (PRs), crude and stratified by propensity scores (PSs). We pooled the country-specific PS strata to obtain a PR adjusted for potential confounding factors. Results: We identified 368 pregnancies exposed to atomoxetine during the first trimester in the 4 Nordic countries and 622 in the US. The pooled crude PR for any major congenital malformation was 1.18 (95% CI, 0.88-1.60), and the adjusted PR was 0.99 (95% CI, 0.74-1.34). For cardiac malformations, the adjusted PR was 1.34 (95% CI, 0.86-2.09). For limb malformations, the adjusted PR was 0.90 (95% CI, 0.38-2.16). Conclusions: After atomoxetine exposure in early pregnancy, we observed no increase in major congenital malformations overall and, although with some uncertainty due to sample size, no statistically increased risk estimates for cardiac malformations and limb malformations.

Maternal Health, Pregnancy and Offspring Factors, and Maternal Thyroid Cancer Risk: A Nordic Population-Based Registry Study

Thyroid cancer incidence is higher in women than men, especially during the reproductive years, for reasons that remain poorly understood. Using population-based registry data from 4 Nordic countries through 2015, we examined associations of perinatal characteristics with risk of maternal thyroid cancer. Cases were women diagnosed with thyroid cancer ≥2 years after last birth (n = 7,425, 83% papillary). Cases were matched to controls (n = 67,903) by mother's birth year, country, and county of residence. Odds ratios (ORs) were estimated using conditional logistic regression models adjusting for parity. Older age at first pregnancy, postpartum hemorrhage (OR = 1.18, 95% (confidence interval) CI: 1.08, 1.29), and benign thyroid conditions (ORs ranging from 1.64 for hypothyroidism to 10.35 for thyroid neoplasms) were associated with increased thyroid cancer risk, as were higher offspring birth weight (per 1-kg increase, OR = 1.17, 95% CI: 1.12, 1.22) and higher likelihood of offspring being large for gestational age (OR = 1.26, 95% CI: 1.11, 1.43). Unmarried/noncohabiting status (OR = 0.91, 95% CI: 0.84, 0.98), maternal smoking (OR = 0.75, 95% CI: 0.67, 0.84), and preterm birth (OR = 0.90, 95% CI: 0.83, 0.98) were associated with reduced risk. Several factors (e.g., older age at first pregnancy, maternal smoking, goiter, benign neoplasms, postpartum hemorrhage, hyperemesis gravidarum, and neonatal jaundice) were associated with advanced thyroid cancer. These findings suggest that some perinatal exposures may influence maternal thyroid cancer risk.

The Cancer Registry of Norway – “a ground for scientific harvesting”

The Cancer Registry of Norway (CRN) has been important in registry-based research in Norway for decades. The use of CRN in combination with other population-based registries and health surveys have been the basis for numerous research projects, which has contributed to fill important knowledge gaps. Researchers at the Norwegian Institute of Public Health and CRN have a long tradition of using these data sources to address research questions of common interests such as e.g. the effect of life style and diet on cancer risk. CRN and the Medical Birth Registry of Norway have co-existed for a long period, making it possible to study cancer incidence and birth characteristics over generations. During the last decades, several new registries such as the Norwegian Prescription Database and the Norwegian Patient Registry have been established, providing opportunities for studying for example drug use and cancer risk and the influence of comorbidities on the development of cancer. In the future, the CRN will be an even more valuable data source when also other population-based registries and health surveys have existed for longer time periods.

Sex differences in childhood cancer risk among children with major birth defects: a Nordic population-based nested case-control study

BACKGROUND

Childhood cancer is more common among children with birth defects, suggesting a common aetiology. Whether this association differs by sex is unclear.

METHODS

We performed a population-based nested case-control study using nationwide health registries in four Nordic countries. We included 21 898 cancer cases (0-19 years) and 218 980 matched population controls, born 1967-2014. Associations between childhood cancer and major birth defects were calculated as odds ratios (ORs) with 95% confidence intervals (CIs) using logistic regression models. Effect modification was evaluated using a counterfactual framework to estimate confidence intervals and P-values for the natural indirect effects.

RESULTS

Birth defects were present for 5.1% (1117/21 898) of childhood cancer cases and 2.2% (4873/218 980) of controls; OR of cancer was higher for chromosomal (OR = 10, 95% CI = 8.6-12) than for non-chromosomal defects (OR = 1.9, 95% CI = 1.8-2.1), strongest between genetic syndromes/microdeletion and renal tumours, Down syndrome and leukaemia, and nervous system defects and central nervous system tumours. The association between birth defects and cancer was stronger among females (OR = 2.8, 95% CI = 2.6-3.1) than males (OR = 2.1, 95% CI = 1.9-2.2, Pinteraction <0.001). Male sex was an independent risk factor for childhood cancer, but very little of the overall association between sex and childhood cancer was mediated through birth defects (4.8%, PNIE <0.001), although more at younger ages (10% below years and 28% below 1 year).

CONCLUSIONS

The birth defect-cancer associations were generally stronger among females than males. Birth defects did not act as a strong mediator for the modest differences in childhood cancer risk by sex, suggesting that other biological pathways are involved.

Association between medical androgen deprivation therapy and long-term cardiovascular disease and all-cause mortality in non-metastatic prostate cancer

Studies have suggested that prostate cancer (PCa) patients receiving androgen deprivation therapy (ADT) are at increased risk of developing or exacerbating cardiovascular disease (CVD). We aimed to explore the association between ADT for PCa and subsequent CVD and all‐cause mortality in this nationwide, longitudinal study. We also evaluated the role of cardiovascular risk and ADT duration to determine effect modification. Norwegian registry data were used to identify patients with PCa from 2008‐18 and who received primary ADT in the first year after diagnosis. The associations between ADT and composite cardiovascular events, and the individual components of myocardial infarction, stroke and heart failure, in addition to atrial fibrillation and all‐cause mortality, were explored using time‐varying Cox regression models. We included 30 923 PCa patients, of whom 8449 (27%) received primary ADT. Mean follow‐up was 2.9 and 3.8 years for CVD events and mortality, respectively. We found an association between ADT and composite CVD (adjusted HR 1.13: 95% CI 1.05‐1.21), myocardial infarction (1.18: 1.05‐1.32), stroke (1.21: 1.06‐1.38), heart failure (1.23: 1.13‐1.35) and all‐cause mortality (1.49: 1.39‐1.61). These associations persisted in those with low and moderate CVD risk and ADT longer than 7 months. A relationship between ADT and composite CVD and all‐cause mortality was observed, especially in those with moderate CVD risk and longer treatment duration. Future studies with more detailed cancer data are needed to verify the clinical relevance of these results, especially when considering all‐cause mortality within the context of treatment guidelines and benefits of ADT.

Interaction of leisure-time physical activity with body mass index on the risk of obesity-related cancers: a pooled study

Physical activity (PA) has been associated with a lower risk of some obesity-related cancers, but the combined association and interaction of PA and body weight on obesity-related cancer risk is less clear. We examined the association of leisure-time PA (high/low) and its combination with body mass index (BMI, <25 [low]/≥25 [high] kg/m² ) on obesity-related cancer risk in 570 021 individuals, aged 43 years on average at baseline, in five Scandinavian cohorts. We used Cox regression to calculate hazard ratios of obesity-related cancers (n = 19 074) and assessed multiplicative and additive interactions between PA and BMI on risk. High leisure-time PA, recorded in 19% of the individuals, was associated with a 7% (95% confidence interval [CI] 4-10%) lower risk of any obesity-related cancer compared to low PA, with similar associations amongst individuals with a low and a high BMI (6% [1-11%] and 7% [2-11%]). High PA was also associated with decreased risks of renal cell (11% [9-31%]) and colon cancer (9% [2-16%]). When high PA and low BMI were combined, the relative risk reduction for all obesity-related cancers was 24% (95% CI 20-28%); endometrial cancer, 47% (35-57%); renal cell cancer, 39% (27-51%); colon cancer, 27% (19-35%); multiple myeloma, 23% (2-40%); and pancreatic cancer, 21% (4-35%), compared to low PA-high BMI. There were no additive or multiplicative interactions between PA and BMI on risk. The result of this study suggests a reduced risk of obesity-related cancer by leisure-time PA in both normal weight and overweight individuals, which further decreased for PA and normal weight combined.

Male to female ratios in autism spectrum disorders by age, intellectual disability and attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the gender distribution in ASD in adults compared with children and the impact of comorbid intellectual disability (ID) and attention-deficit/hyperactivity disorder (ADHD) on the male to female ratio (MFR).

METHODS

We estimated the MFR and the male prevalence ratio (PR) for ASD in adults and children using the Medical Birth Registry of Norway, including all individuals born during 1967-2011. We examined variation with age, comorbid ID and ADHD as defined by diagnoses in the Norwegian Patient Registry during 2008-2015 and/or a dispensed prescription for ADHD medication.

RESULTS

The sample included 1,701,206 adults and 804,146 children, including 8,995 (0.5%) adults and 8,056 (1.0%) children with ASD, 53,822 (3.2%) adults and 26,967 (3.4%) children with ADHD and 9,178 (0.5%) adults and 5,038 (0.6%) children with ID. The MFR for ASD was 3.67 in children and 2.57 in adults, corresponding to a male PR in ASD of 1.54 (95% CI 1.53-1.56) and 1.41 (1.39-1.24), respectively. Comorbid ID decreased the MFR and the male PR in both adults and children, whereas comorbid ADHD significantly increased the male PR in children. The MFR and the population prevalence of ASD, ADHD and ID decreased from children to younger adults and yet further to older adults.

CONCLUSION

We found a lower MFR and male PR in adults than in children. Findings suggest the strong male predominance seen in childhood/clinical studies of ASD diminishes in adult samples, possibly reflecting the influence of non-aetiological factors such as later diagnosis in females, diagnostic biases and diagnostic trends.

Use of sildenafil and other phosphodiesterase type 5 inhibitors among pregnant women in Scandinavia

INTRODUCTION

For phosphodiesterase type 5 (PDE5) inhibitors, such as sildenafil, the only approved indication in women is for pulmonary arterial hypertension. These drugs are increasingly being proposed and tested for treatment of female infertility and complications in pregnancy. However, the extent of use of PDE5 inhibitors in the general pregnant population over the last decades is unknown. Therefore, we conducted a descriptive cohort study using data from the population health registers in the Scandinavian countries.

MATERIAL AND METHODS

By linking the Medical Birth Registers and the Prescribed Drug Registers in Denmark (1997-2017), Norway (2004-2017), and Sweden (2006-2016), women with filled prescriptions of PDE5 inhibitors in outpatient settings in the 90 days before the date of last menstrual period and/or during pregnancies were identified. With additional linkage to the National Patient Registers, information on maternal, pregnancy, and infant characteristics, co-morbidities, and co-medication was collected and described.

RESULTS

Among over 3 million singleton pregnancies, only 77 were pregnancies in women who had at least one filled prescription of a PDE5 inhibitor within the 90 days before the start of pregnancy to delivery. Prescription fills most often occurred before the last menstrual period and in the first trimester, with very few occurring later in pregnancy. Sildenafil was the most used PDE5 inhibitor. Among pregnant women using PDE5 inhibitors, 44% were 35 years of age or older, eight had a cardiovascular diagnosis, and three specifically had a diagnosis of pulmonary arterial hypertension. Among the infants born to mothers using PDE5 inhibitors, nine were born preterm, six were small-for-gestational age, five had an Apgar score at 5 minutes below 8, 18 were admitted to the Neonatal Intensive Care Unit, and eight had respiratory and cardiovascular conditions.

CONCLUSIONS

Few women used PDE5 inhibitors in outpatient settings before or during pregnancy in the Scandinavian countries in the last decades. Only a small proportion had a diagnosis for pulmonary arterial hypertension, suggesting off-label use in the remaining users. Use was predominantly in mothers over age 35 years. The safety of fetal exposure to sildenafil and other PDE5 inhibitors in pregnancy has not been established. As maternal age continues to increase and additional uses of PDE5 inhibitors are investigated, the safety of these drugs in pregnancy should be thoroughly evaluated.

The Norwegian Society for Pharmacoepidemiology

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Sex differences in parent-offspring recurrence of attention-deficit/hyperactivity disorder

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder sharing genetic risk factors with other common psychiatric disorders. However, intergenerational recurrence patterns of ADHD from parents to sons and daughters are not known. We aimed to examine the risk of ADHD in offspring of parents with ADHD and parents with other psychiatric disorders by parental and offspring sex, using parents without the specific disorders as comparison.

METHODS

In a generation study linking data from several population-based registries, all Norwegians born 1967-2011 (n = 2,486,088; Medical Birth Registry of Norway) and their parents were followed to 2015. To estimate intergenerational recurrence risk, we calculated prevalence differences (PD) and the relative risk (RR) of ADHD in offspring by parental ADHD, bipolar disorder (BD), schizophrenia spectrum disorder (SCZ), major depression (MDD), all by parental and offspring sex.

RESULTS

The absolute prevalence of ADHD in offspring of parents with ADHD was very high, especially in sons of two affected parents (41.5% and 25.1% in sons and daughters, respectively), and far higher than in offspring of parents with BD, SCZ or MDD. Intergenerational recurrence risks were higher for maternal than paternal ADHD (RR_maternal 8.4, 95% confidence interval (CI) 8.2-8.6 vs. RR_paternal 6.2, 6.0-6.4) and this was also true on the absolute scale (PD_maternal 21.1% (20.5-21.7) vs. PD_paternal 14.8% (14.3-15.4)). RRs were higher in daughters, while PDs higher in sons. Parental SCZ, BD and MDD were associated with an approximately doubled risk of offspring ADHD compared to parents without the respective disorders, and estimates did not differ significantly between daughters and sons.

CONCLUSIONS

The intergenerational recurrence risks of ADHD were high and higher from mothers with ADHD than fathers with ADHD. Other parental psychiatric disorders also conferred increased risk of offspring ADHD, but far lower, indicating a sex- and diagnosis-specific intergenerational recurrence risk in parents with ADHD.

The Inverse Association of Body Mass Index with Lung Cancer: Exploring Residual Confounding, Metabolic Aberrations and Within-Person Variability in Smoking

BACKGROUND

The inverse observational association between body mass index (BMI) and lung cancer risk remains unclear. We assessed whether the association is explained by metabolic aberrations, residual confounding, and within-person variability in smoking, and compared against other smoking-related cancers.

METHODS

We investigated the association between BMI, and its combination with a metabolic score (MS) of mid-blood pressure, glucose, and triglycerides, with lung cancer and other smoking-related cancers in 778,828 individuals. We used Cox regression, adjusted and corrected for within-person variability in smoking (status/pack-years), calculated from 600,201 measurements in 221,958 participants.

RESULTS

Over a median follow-up of 20 years, 20,242 smoking-related cancers (6,735 lung cancers) were recorded. Despite adjustment and correction for substantial within-person variability in smoking, BMI remained inversely associated with lung cancer [HR per standard deviation increase, 0.87 (95% confidence interval 0.85-0.89)]. Individuals with BMI less than 25 kg/m² and high MS had the highest risk [HR 1.52 (1.44-1.60) vs. BMI ≥25 with low MS]. These associations were weaker and nonsignificant among nonsmokers. Similar associations were observed for head and neck cancers and esophageal squamous cell carcinoma, whereas for other smoking-related cancers, we generally observed positive associations with BMI.

CONCLUSIONS

The increased lung cancer risk with low BMI and high MS is unlikely due to residual confounding and within-person variability in smoking. However, similar results for other cancers strongly related to smoking suggest a remaining, unknown, effect of smoking.

IMPACT

Extensive smoking-adjustments may not capture all the effects of smoking on the relationship between obesity-related factors and risk of smoking-related cancers.

Prescribed drugs in 27 000 individuals after diagnosis of colorectal cancer: A population-based cohort study

BACKGROUND

The prevalence of prescribed drugs in survivors of colorectal cancer (CRC) was evaluated.

METHODS

Data from the Cancer Registry of Norway were linked to the Norwegian Prescription Database for a study population of 3.52 million individuals. Prevalence ratios (PRs) with 95% confidence intervals (CIs) of prescribed drugs in CRC-survivors compared to the cancer-free population, were estimated by log-binomial regression, adjusting for age and education.

RESULTS

Almost 27 000 individuals, aged 20 to 84, were diagnosed with CRC during 2005 to 2014. The first year after diagnosis, the prevalence of prescribed drugs was higher in CRC-survivors compared with the cancer-free population, especially drugs for anxiety and tension, and steroid-responsive conditions. PRs for several drugs, especially drugs used for mental and behavioural disorders, decreased with time since diagnosis. The prevalence of drugs used for anxiety and tension was elevated 10 years after diagnosis; PRs the first year after diagnosis were 20 (95% CI: 18-22) in males and 17 (16-18) in females. Ten years after diagnosis PRs were 5.0 (3.1-7.9) and 2.0 (1.0-3.8), respectively. In absolute numbers, the largest increase, compared to the cancer-free population, was in drugs used for gastric acid disorders and pain. The prevalence of neuromodulatory drugs was higher in CRC-survivors.

CONCLUSIONS

The prevalence of several drugs was higher in CRC-survivors than in the cancer-free population 10 years after diagnosis. The largest absolute excess in prevalence was for gastric acid disorder and pain medications, while the relative prevalence of drugs used for anxiety and tension was high in CRC-survivors. Long persisting neuropathia was indicated.

Metabolic factors and the risk of small intestine cancers: Pooled study of 800 000 individuals in the metabolic syndrome and cancer project

To explore the largely unknown etiology of small intestine cancer, we examined metabolic factors and risk of small intestine cancer overall and by subtypes. Among 404 220 women and 403 265 men in six European cohorts, we applied Cox regression with adjustment for smoking and body mass index (BMI), to calculate sex-specific hazard ratios (HRs) of small intestine cancer by levels of BMI, mean arterial pressure (MAP) and plasma total cholesterol, triglycerides and glucose. We also calculated HRs for these factors combined (metabolic score; MetS) and used Wald test statistics to investigate pairwise interactions between metabolic factors on risk. We also performed analyses separately per subtype (neuroendocrine tumors [NETs] and adenocarcinomas). During a median follow-up of 16.9 years, 144 women and 195 men were diagnosed with small intestine cancer, including 184 NETs and 99 adenocarcinomas. Among men, no main associations or interactions between metabolic factors were observed in relation to the risk of small intestine cancer. Among women, triglycerides were positively and linearly associated with risk (HR per standard deviation [SD]: 1.23, 95% confidence interval [CI]: 1.04-1.46), and a positive association was also observed for the MetS (HR per SD: 1.25, 95% CI: 1.02-1.52). Positive interactions were observed among women between triglycerides and cholesterol (P = .0005), and between MAP and glucose (P = .009), on risk. Glucose was positively associated with adenocarcinomas among women. This large, prospective study suggests that elevated triglycerides, and metabolic factors in interaction, confer an increased risk of small intestine cancer among women, but not among men.

Maternal health, in-utero, and perinatal exposures and risk of thyroid cancer in offspring: a Nordic population-based nested case-control study

BACKGROUND

Thyroid cancer tends to be diagnosed at a younger age (median age 51 years) compared with most other malignancies (such as breast cancer [62 years] or lung cancer [71 years]). The incidence of thyroid cancer is higher in women than men diagnosed from early adolescence. However, few in-utero and early life risk exposures associated with increased risk of thyroid cancer have been identified.

METHODS

In this population-based nested case-control study we used registry data from four Nordic countries to assess thyroid cancer risk in offspring in relation to maternal medical history, pregnancy complications, and birth characteristics. Patient with thyroid cancer (cases) were individuals born and subsequently diagnosed with first primary thyroid cancer from 1973 to 2013 in Denmark, 1987 to 2014 in Finland, 1967 to 2015 in Norway, or 1973 to 2014 in Sweden. Each case was matched with up to ten individuals without thyroid cancer (controls) based on birth year, sex, country, and county of birth. Cases and matched controls with a previous diagnosis of any cancer, other than non-melanoma skin cancer, at the time of thyroid cancer diagnosis were excluded. Cases and matched controls had to reside in the country of birth at the time of thyroid cancer diagnosis. Conditional logistic regression models were used to calculate odds ratios (ORs) with 95% CIs.

RESULTS

Of the 2437 cases, 1967 (81·4%) had papillary carcinomas, 1880 (77·1%) were women, and 1384 (56·7%) were diagnosed before age 30 years (range 0-48). Higher birth weight (OR per kg 1·14 [95% CI 1·05-1·23]) and congenital hypothyroidism (4·55 [1·58-13·08]); maternal diabetes before pregnancy (OR 1·69 [0·98-2·93]) and postpartum haemorrhage (OR 1·28 [1·06-1·55]); and (from registry data in Denmark) maternal hypothyroidism (18·12 [10·52-31·20]), hyperthyroidism (11·91 [6·77-20·94]), goiter (67·36 [39·89-113·76]), and benign thyroid neoplasms (22·50 [6·93-73·06]) were each associated with an increased risk of thyroid cancer in offspring.

INTERPRETATION

In-utero exposures, particularly those related to maternal thyroid disorders, might have a long-term influence on thyroid cancer risk in offspring.

FUNDING

Intramural Research Program of the National Cancer Institute (National Institutes of Health).

Cancer risk in individuals with major birth defects: large Nordic population based case-control study among children, adolescents, and adults

OBJECTIVE

To examine associations between birth defects and cancer from birth into adulthood.

DESIGN

Population based nested case-control study.

SETTING

Nationwide health registries in Denmark, Finland, Norway, and Sweden.

PARTICIPANTS

62 295 cancer cases (0-46 years) and 724 542 frequency matched controls (matched on country and birth year), born between 1967 and 2014.

MAIN OUTCOME MEASURES

Relative risk of cancer in relation to major birth defects, estimated as odds ratios with 99% confidence intervals from logistic regression models.

RESULTS

Altogether, 3.5% (2160/62 295) of cases and 2.2% (15 826/724 542) of controls were born with major birth defects. The odds ratio of cancer for people with major birth defects compared with those without was 1.74 (99% confidence interval 1.63 to 1.84). For individuals with non-chromosomal birth defects, the odds ratio of cancer was 1.54 (1.44 to 1.64); for those with chromosomal anomalies, the odds ratio was 5.53 (4.67 to 6.54). Many structural birth defects were associated with later cancer in the same organ system or anatomical location, such as defects of the eye, nervous system, and urinary organs. The odds ratio of cancer increased with number of defects and decreased with age, for both non-chromosomal and chromosomal anomalies. The odds ratio of cancer in people with any non-chromosomal birth defect was lower in adults (≥20 years: 1.21, 1.09 to 1.33) than in adolescents (15-19 years: 1.58, 1.31 to 1.90) and children (0-14 years: 2.03, 1.85 to 2.23). The relative overall cancer risk among adults with chromosomal anomalies was markedly reduced from 11.3 (9.35 to 13.8) in children to 1.50 (1.01 to 2.24). Among adults, skeletal dysplasia (odds ratio 3.54, 1.54 to 8.15), nervous system defects (1.76, 1.16 to 2.65), chromosomal anomalies (1.50, 1.01 to 2.24), genital organs defects (1.43, 1.14 to 1.78), and congenital heart defects (1.28, 1.02 to 1.59) were associated with overall cancer risk.

CONCLUSIONS

The increased risk of cancer in individuals with birth defects persisted into adulthood, both for non-chromosomal and chromosomal anomalies. Further studies on the molecular mechanisms involved are warranted.

Urinary incontinence associated with anxiety and depression: the impact of psychotropic drugs in a cross-sectional study from the Norwegian HUNT study

BACKGROUND

Anxiety and depression are in both cross-sectional and longitudinal studies associated with urinary incontinence (UI) in women, strongest for the urgency component of UI. The role of psychotropic drugs in this association, especially antidepressants, has been questioned, but not clarified. The present study aimed to explore the associations between UI and anxiety/depression and the possible impact of psychotropic drugs on these associations.

METHODS

We conducted a cross-sectional, population-based study with questionnaire data from 21,803 women ≥20 years in the Norwegian Nord-Trøndelag Health Study merged with the Norwegian Prescription Database, which contains information on all dispensed prescriptions. We used multivariate logistic regression to investigate the association between UI (any UI, and by type and severity) and anxiety/depression (by different score on Hospital anxiety and depression scale), and the influence of psychotropic drugs on this association (by different volume of drug use).

RESULTS

Compared with normal anxiety- and depression score, having moderate/severe anxiety or depression (HADS≥11) increased the prevalence of UI from 27.6 to 37.8% (OR 1.59 (1.40-1.81), p < 0.001) for anxiety and from 28.0 to 43.7% (OR 1.79 (1.46-2.21), p < 0.001) for depression. According to type of UI, mixed UI was most strongly associated with a high HADS-score with an odds ratio 1.84 (1.65-2.05) for anxiety and 1.85 (1.61-2.13) for depression. Compared to no UI, severe UI was associated with depression with odds ratios of 2.04 (1.74-2.40), compared with no UI. Psychotropic drug use did not influence the associations between UI and anxiety/depression. We found high prevalence of UI among users of various psychotropic drugs. After adjustments, only antidepressants were associated with UI, with OR 1.36 (1.08-1.71) for high defined daily dose of the drug. Anxiolytics were associated with less UI with OR 0.64 (0.45-0.91) after adjustments for anxiety.

CONCLUSION

This study showed that anxiety, depression and use of antidepressants are associated factors with UI, strongest for urgency and mixed type of UI, with increasing ORs by increasing severity of the conditions and increased daily dose of the medication. Use of antidepressants did not influence the associations between UI and anxiety/depression.

Incidence of Malformations After Early Pregnancy Exposure to Modafinil in Sweden and Norway

This pharmacoepidemiology study uses Scandinavian birth registry data to estimate the association between modafinil use during early pregnancy and major congenital malformations among infants born in Norway and Sweden between 2005-2006 and 2016-2017.

The triglyceride-glucose index as a measure of insulin resistance and risk of obesity-related cancers

BACKGROUND

The role of insulin resistance as a mediator in the association of body mass index (BMI) with site-specific cancer risk has, to our knowledge, never been systematically quantified.

METHODS

Altogether 510 471 individuals from six European cohorts, with a mean age of 43.1 years, were included. We used the triglyceride glucose product (TyG index) as a surrogate measure for insulin resistance. We fitted Cox models, adjusted for relevant confounders, to investigate associations of TyG index with 10 common obesity-related cancers, and quantified the proportion of the effect of BMI mediated through TyG index on the log-transformed hazard ratio (HR) scale.

RESULTS

During a median follow-up of 17.2 years, 16 052 individuals developed obesity-related cancers. TyG index was associated with the risk of cancers of the kidney HR per one standard deviation increase 1.13, 95% confidence interval: 1.07 to 1.20], liver (1.13, 1.04 to 1.23), pancreas (1.12, 1.06 to 1.19), colon (1.07, 1.03 to 1.10) and rectum (1.09, 1.04 to 1.14). Substantial proportions of the effect of BMI were mediated by TyG index for cancers of the pancreas (42%), rectum (34%) and colon (20%); smaller proportions for kidney (15%) and liver (11%). Little or no mediation was observed for breast (postmenopausal), endometrial and ovarian cancer. Results were similar for males and females, except for pancreatic cancer where the proportions mediated were 20% and 91%, respectively.

CONCLUSIONS

The TyG index was associated with increased risk of cancers of the digestive system and substantially mediated the effect of BMI, suggesting that insulin resistance plays a promoting role in the pathogenesis of gastrointestinal cancers.

Antipsychotic drug use in pregnancy: A multinational study from ten countries

AIM

To compare the prevalence and trends of antipsychotic drug use during pregnancy between countries across four continents.

METHODS

Individually linked health data in Denmark (2000-2012), Finland (2005-2014), Iceland (2004-2017), Norway (2005-2015), Sweden (2006-2015), Germany (2006-2015), Australia (New South Wales, 2004-2012), Hong Kong (2001-2015), UK (2006-2016), and the US (Medicaid, 2000-2013, and IBM MarketScan, 2012-2015) were used. Using a uniformed approach, we estimated the prevalence of antipsychotic use as the proportion of pregnancies where a woman filled at least one antipsychotic prescription within three months before pregnancy until birth. For the Nordic countries, data were meta-analyzed to investigate maternal characteristics associated with the use of antipsychotics.

RESULTS

We included 8,394,343 pregnancies. Typical antipsychotic use was highest in the UK (4.4%) whereas atypical antipsychotic use was highest in the US Medicaid (1.5%). Atypical antipsychotic use increased over time in most populations, reaching 2% in Australia (2012) and US Medicaid (2013). In most countries, prochlorperazine was the most commonly used typical antipsychotic and quetiapine the most commonly used atypical antipsychotic. Use of antipsychotics decreased across the trimesters of pregnancy in all populations except Finland. Antipsychotic use was elevated among smokers and those with parity ≥4 in the Nordic countries.

CONCLUSION

Antipsychotic use during pregnancy varied considerably between populations, partly explained by varying use of the typical antipsychotic prochlorperazine, which is often used for nausea and vomiting in early pregnancy. Increasing usage of atypical antipsychotics among pregnant women reflects the pattern that was previously reported for the general population.

Pregnancy-related risk factors for sex cord-stromal tumours and germ cell tumours in parous women: a registry-based study

BACKGROUND

Non-epithelial ovarian cancers are divided into sex cord-stromal tumours (SCSTs) and germ cell tumours (GCTs). Whereas parity and other pregnancy-related factors are protective for epithelial ovarian cancer, their associations with SCSTs and GCTs remains unclear.

METHODS

Using data from the medical birth registries from Denmark, Finland, Norway and Sweden, we compared all parous women with a diagnosis of SCSTs (n = 420) or GCTs (n = 345) 1970-2013 with up to 10 parous controls (SCSTs n = 4041; GCTs n = 2942) matched on the cases' birth year and country. We used conditional logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs) of associations between pregnancy-related factors and SCSTs and GCTs.

RESULTS

The risk of SCSTs, but not GCTs, decreased with higher age at last birth [≥40 versus <25 years: OR 0.48 (95% CI 0.23-0.98)]. The risk of SCSTs (but not GCTs) also decreased with shorter time since last birth. Number of births, preterm birth, preeclampsia, and offspring size were not associated with risk of SCSTs or GCTs.

CONCLUSIONS

We found a decreased risk of SCSTs with higher age at last birth and shorter time since last birth. The risk of SCSTs (but not GCTs) may be influenced by the woman's reproductive history.

Prenatal exposure to opioid maintenance treatment and neonatal outcomes: Nationwide registry studies from the Czech Republic and Norway

There is lack of knowledge about the safety of treatment with methadone and buprenorphine as part of opioid maintenance treatment (OMT) during pregnancy. The purpose of this study was to examine neonatal outcomes concerning the use of OMT during pregnancy. We used nationwide registry linkages from the Czech Republic (2000-2014) and Norway (2004-2013). We compared prenatally OMT-exposed newborns with (a) newborns of women hospitalized with opioid use disorder during pregnancy in the Czech sample and (b) newborns with neonatal abstinence syndrome (NAS) in Norway. We performed multivariate linear and binary logistic regression exploring the associations between OMT and neonatal outcomes (growth parameters, gestational age, fetal death, small for gestational age, Apgar score, and NAS). Regression coefficients (b) and odds ratios (ORs) were estimated. The cohorts consisted of 333 Czech, and 235 Norwegian OMT-exposed newborns, and 106 and 294 newborns in the comparison groups, respectively. In both countries, the neonatal growth parameters were similar in the OMT and the comparison groups. In Norway, OMT exposure prolonged gestational age (adjusted b = 0.96 weeks, 95% confidence interval [CI] =0.39-1.53) while the odds of preterm birth and Apgar score at 5 minutes were lower than in the comparison group (adjusted OR = 0.35, 0.16-0.75 and aOR = 0.21, 0.06-0.78, respectively). Newborns of women in OMT had similar growth parameters as newborns of women with opioid use disorders who were not in OMT during pregnancy. Overall, our findings do not suggest that OMT results in worse neonatal outcomes.

BMI and weight changes and risk of obesity-related cancers: a pooled European cohort study

Background

Obesity is an established risk factor for several cancers. Adult weight gain has been associated with increased cancer risk, but studies on timing and duration of adult weight gain are relatively scarce. We examined the impact of BMI (body mass index) and weight changes over time, as well as the timing and duration of excess weight, on obesity- and non-obesity-related cancers.

Methods

We pooled health data from six European cohorts and included 221 274 individuals with two or more height and weight measurements during 1972–2014. Several BMI and weight measures were constructed. Cancer cases were identified through linkage with national cancer registries. Hazard ratios (HRs) of cancer with 95% confidence intervals (CIs) were derived from time-dependent Cox-regression models.

Results

During follow-up, 27 881 cancer cases were diagnosed; 9761 were obesity-related. The HR of all obesity-related cancers increased with increasing BMI at first and last measurement, maximum BMI and longer duration of overweight (men only) and obesity. Participants who were overweight before age 40 years had an HR of obesity-related cancers of 1.16 (95% CI 1.02, 1.32) and 1.15 (95% CI 1.04, 1.27) in men and women, respectively, compared with those who were not overweight. The risk increase was particularly high for endometrial (70%), male renal-cell (58%) and male colon cancer (29%). No positive associations were seen for cancers not regarded as obesity-related.

Conclusions

Adult weight gain was associated with increased risk of several major cancers. The degree, timing and duration of overweight and obesity also seemed to be important. Preventing weight gain may reduce the cancer risk.

Associations of pregnancy-related factors and birth characteristics with risk of endometrial cancer: A Nordic population-based case-control study

Many pregnancy-related factors are associated with reduced endometrial cancer risk. However, it remains unclear whether pregnancy-related complications (e.g., hypertensive conditions) are associated with risk and whether these associations vary by endometrial cancer subtype. Thus, we evaluated the risk of endometrial cancer, overall and by subtype, in relation to pregnancy-related factors, pregnancy complications and birth characteristics. Utilizing population-based register data from four Nordic countries, we conducted a nested case-control analysis of endometrial cancer risk. We included 10,924 endometrial cancer cases and up to 10 matched controls per case. Odds ratios (ORs) with 95% confidence intervals (CIs) were derived from unconditional logistic regression models. We further evaluated associations by individual histology (i.e., endometrioid, serous, etc.) or, for rare exposures (e.g., pregnancy complications), by dualistic type (Type I [n = 10,343] and Type II [n = 581]). Preexisting and pregnancy-related hypertensive conditions were associated with increased endometrial cancer risk (OR [95% CI]: preexisting hypertension 1.88 [1.39-2.55]; gestational hypertension 1.47 [1.33-1.63]; preeclampsia 1.43 [1.30-1.58]), with consistent associations across dualistic type. Increasing number of pregnancies (≥4 vs. 1 birth: 0.64 [0.59-0.69]) and shorter time since last birth (<10 vs. ≥30 years: 0.34 [0.29-0.40]) were associated with reduced endometrial cancer risk, with consistent associations across most subtypes. Our findings support the role for both hormonal exposures and cell clearance as well as immunologic/inflammatory etiologies for endometrial cancer. This research supports studying endometrial hyperplasia, a precursor condition of endometrial cancer, in the context of pregnancy-related exposures, as this may provide insight into the mechanisms by which pregnancy affects subsequent cancer risk.

β-Blocker Use in Pregnancy and the Risk for Congenital Malformations: An International Cohort Study

BACKGROUND

β-Blockers are a class of antihypertensive medications that are commonly used in pregnancy.

OBJECTIVE

To estimate the risks for major congenital malformations associated with first-trimester exposure to β-blockers.

DESIGN

Cohort study.

SETTING

Health registries in the 5 Nordic countries and the U.S. Medicaid database.

PATIENTS

Pregnant women with a diagnosis of hypertension and their offspring.

MEASUREMENTS

First-trimester exposure to β-blockers was assessed. Outcomes were any major congenital malformation, cardiac malformations, cleft lip or palate, and central nervous system (CNS) malformations. Propensity score stratification was used to control for potential confounders.

RESULTS

Of 3577 women with hypertensive pregnancies in the Nordic cohort and 14 900 in the U.S. cohort, 682 (19.1%) and 1668 (11.2%), respectively, were exposed to β-blockers in the first trimester. The pooled adjusted relative risk (RR) and risk difference per 1000 persons exposed (RD1000) associated with β-blockers were 1.07 (95% CI, 0.89 to 1.30) and 3.0 (CI, -6.6 to 12.6), respectively, for any major malformation; 1.12 (CI, 0.83 to 1.51) and 2.1 (CI, -4.3 to 8.4) for any cardiac malformation; and 1.97 (CI, 0.74 to 5.25) and 1.0 (CI, -0.9 to 3.0) for cleft lip or palate. For CNS malformations, the adjusted RR was 1.37 (CI, 0.58 to 3.25) and the RD1000 was 1.0 (CI, -2.0 to 4.0) (based on U.S. cohort data only).

LIMITATION

Analysis was restricted to live births, exposure was based on dispensed medication, and cleft lip or palate and CNS malformations had few outcomes.

CONCLUSION

The results suggest that maternal use of β-blockers in the first trimester is not associated with a large increase in the risk for overall malformations or cardiac malformations, independent of measured confounders.

PRIMARY FUNDING SOURCE

The Eunice Kennedy Shriver National Institute of Child Health and Human Development and the Söderström König Foundation.

Pregnancy complications and subsequent breast cancer risk in the mother: a Nordic population-based case-control study

Certain features of pregnancy are important risk factors for breast cancer, such as protection afforded by young age at first birth. Preeclampsia, a pregnancy complication, is associated with reduced maternal breast cancer risk. However, questions remain regarding causality, biological mechanisms and the relation of other hypertensive conditions to risk. We conducted a population-based case-control study of breast cancer cases (n = 116,196) in parous women identified through linkage of birth and cancer registries in Denmark, Finland, Norway and Sweden (1967-2013), including up to 10 matched controls per case (n = 1,147,192) sampled from the birth registries (complete data were not available on all variables). Odds ratios (ORs) with 95% confidence intervals (CIs) were derived from unconditional logistic regression models including matching factors (country, maternal birth year) and parity. Hypertension diagnosed before pregnancy (OR 0.87; 95% CI 0.78-0.97), gestational hypertension (OR 0.90; 95% CI 0.86-0.93) and preeclampsia (OR 0.91; 95% CI 0.88-0.95) were associated with reduced breast cancer risk. Results remained similar after adjustment for smoking and maternal body mass index before first pregnancy, and were generally similar stratified by parity, age at breast cancer diagnosis, time since first and last birth, sex of the offspring and calendar time. Except for retained placenta (OR 1.14; 95% CI 0.98-1.32), no other pregnancy complication appeared associated with breast cancer risk. The mechanisms mediating the modest risk reductions for history of preeclampsia or hypertension preceding or arising during pregnancy, and possible increased risk with history of retained placenta are unknown and warrant further laboratory, clinical and epidemiological investigation.

Preterm delivery is associated with an increased risk of epithelial ovarian cancer among parous women

Epithelial ovarian cancer is a fatal disease of largely unknown etiology. Higher parity is associated with reduced risk of ovarian cancer. However, among parous women, the impact of pregnancy-related factors on risk is not well understood. This population-based case-control study included all parous women with epithelial ovarian cancer in Denmark, Finland, Norway and Sweden during 1967-2013 (n = 10,957) and up to 10 matched controls (n = 107,864). We used conditional logistic regression to estimate odds ratios (ORs) with 95% confidence intervals (CIs) for pregnancy-related factors and ovarian cancer risk by histological subtype. Preterm delivery was associated with an increased risk [pregnancy length (last pregnancy) ≤30 vs. 39-41 weeks, OR 1.33 (95% CI 1.06-1.67), adjusted for number of births]; the OR increased as pregnancy length decreased (p for trend < 0.001). Older age at first and last birth was associated with a decreased risk [first birth: 30-39 vs. <25 years: adjusted OR 0.76 (95% CI 0.70-0.83); last birth 30-39 vs. <25 years: adjusted OR 0.76 (95% CI 0.71-0.82)]. Increasing number of births was protective [≥4 births vs. 1; OR 0.63 (95% CI 0.59-0.68)] for all subtypes, most pronounced for clear-cell tumors [OR 0.30, (95% CI 0.21-0.44), p_{heterogeneity}  < 0.001]. No associations were observed for multiple pregnancies, preeclampsia or offspring size. In conclusion, in addition to high parity, full-term pregnancies and pregnancies at older ages were associated with decreased risk of ovarian cancer. Our findings favor the cell clearance hypothesis, i.e. a recent pregnancy provides protection by clearing of precancerous cells from the epithelium of the ovary/fallopian tubes, mediated by placental or ovarian hormones.

Neonatal outcomes after fetal exposure to methadone and buprenorphine: national registry studies from the Czech Republic and Norway

BACKGROUND AND AIMS

Opioid maintenance treatment (OMT) is recommended to opioid-dependent females during pregnancy. However, it is not clear which medication should be preferred. We aimed to compare neonatal outcomes after prenatal exposure to methadone (M) and buprenorphine (B) in two European countries.

DESIGN

Nation-wide register-based cohort study using personalized IDs assigned to all citizens for data linkage.

SETTING

The Czech Republic (2000-14) and Norway (2004-13). [Correction added after online publication on 26 April 2018: The Czech Republic (2000-04) corrected to (2000-14).] PARTICIPANTS: Opioid-dependent pregnant Czech (n = 333) and Norwegian (n = 235) women in OMT who received either B or M during pregnancy and their newborns.

MEASUREMENTS

We linked data from health registries to identify the neonatal outcomes: gestational age, preterm birth, birth weight, length and head circumference, small for gestational age, miscarriages and stillbirth, neonatal abstinence syndrome (NAS) and Apgar score. We performed multivariate linear regression and binary logistic regression to explore the associations between M and B exposure and outcomes. Regression coefficient (β) and odds ratio (OR) were computed.

FINDINGS

Most neonatal outcomes were more favourable after exposure to B compared with M, but none of the differences was statistically significant. For instance, in the multivariate analysis, birth weight was β = 111.6 g [95% confidence interval (CI) = -10.5 to 233.6 and β = 83.1 g, 95% CI = -100.8 to 267.0] higher after B exposure in the Czech Republic and Norway, respectively. Adjusted OR of NAS for B compared with M was 0.94 (95% CI = 0.46-1.92) in the Norwegian cohort.

CONCLUSIONS

Two national cohorts of women receiving opioid maintenance treatment during pregnancy showed small but not statistically significant differences in neonatal outcomes in favour of buprenorphine compared with methadone.

Trends in prescription drug use during pregnancy and postpartum in Norway, 2005 to 2015

PURPOSE

To explore trends in use of maternal medication 3 months prior to, during and 3 months after pregnancy.

METHODS

Data on births from the Medical Birth Registry of Norway were linked to the Norwegian Prescription Database, identifying women's use of medications around pregnancy. All women giving birth in Norway during 2005 to 2015 (638 532 singleton births to 414 567 women) were included. Proportions of pregnant women using different medications in association with pregnancy, and annual relative change in medication use during 2005 to 2015, were calculated.

RESULTS

In Norway, 60% of pregnant women used prescription medications during pregnancy (2005-15), increasing from 57% in 2005 to 62% in 2015. The annual relative increase was 0.9% (95% CI: 0.8-1.0). In the first trimester, approximately 17% of the women used medications regarded as potentially teratogenic during 2005 to 2015, increasing from 15% to 19%. Overall, this proportion was higher in the first than in the second (8.9%) and third (8.0%) trimesters, and higher than in the 3 months after pregnancy (14%). The annual relative increase of medications regarded as potentially teratogenic in the first trimester was 2.5% (95% CI: 2.3-2.7).

CONCLUSIONS

The proportion of women using potentially teratogenic medications in the first trimester of pregnancy have increased during the last decade. Clinicians need to be aware of the possibility of pregnancy when prescribing potentially teratogenic medication to women of fertile age and focus this in the consultations. The increasing trends call for the need of routine surveillance of adverse birth outcomes linked to medication use in pregnancy.

Oral Fluconazole in Pregnancy and Risk of Stillbirth and Neonatal Death

This pharmacoepidemiology study uses Swedish and Norwegian registry data to investigate associations between fluconazole use during pregnancy and subsequent stillbirth and neonatal death.

Associations between attention-deficit/hyperactivity disorder and autoimmune diseases are modified by sex: a population-based cross-sectional study

Several studies have demonstrated associations between neuropsychiatric disorders, such as attention-deficit/hyperactivity disorder (ADHD), and the immune system, including autoimmune diseases. Since ADHD and many autoimmune diseases show sex-specific properties, such associations may also differ by sex. Using Norwegian national registries, we performed a cross-sectional study based on a cohort of 2,500,118 individuals to investigate whether ADHD is associated with common autoimmune diseases. Associations between ADHD and autoimmune diseases in females and males were investigated with logistic regression and effect modification by sex was evaluated. Several subanalyses were performed. The strongest association was found between ADHD and psoriasis in females, adjusted odds ratio (adjOR) = 1.57 (95% confidence interval: 1.46-1.68) and males, adjOR = 1.31 (1.23-1.40); p value for interaction < 0.0001. Furthermore, among females, ADHD was associated with Crohn's disease, adjOR = 1.44 (1.16-1.79) and ulcerative colitis, adjOR = 1.28 (1.06-1.54). In contrast, males with ADHD had lower odds of Crohn's disease, adjOR = 0.71 (0.54-0.92), in addition to a trend for lower odds of ulcerative colitis, adjOR = 0.86 (0.71-1.03); p values for interaction < 0.0001 and 0.0023, respectively. In a group of females where information on smoking and body mass index was available, adjustment for these potential mediators did not substantially alter the associations. Our findings support previously reported associations between ADHD and diseases of the immune system. The associations differ by sex, suggesting that sex-specific immune-mediated neurodevelopmental processes may be involved in the etiology of ADHD.

Gender differences in psychiatric comorbidity: a population-based study of 40 000 adults with attention deficit hyperactivity disorder

OBJECTIVE

We aimed at determining whether gender modified associations between ADHD and psychiatric comorbidities in adults.

METHOD

We identified adults with ADHD by linking Norwegian national registries and compared them with the remaining adult population (born 1967-1997, ADHD and bipolar during 2004-2015, other psychiatric disorders 2008-2015). Prevalence differences (PDs) and prevalence ratios (PRs) of psychiatric disorders were determined by Poisson regression. Interaction by gender was evaluated on additive (PDs) and multiplicative (PRs) scales. Proportions of psychiatric disorders attributable to ADHD were calculated.

RESULTS

We identified 40 103 adults with ADHD (44% women) and 1 661 103 adults (49% women) in the remaining population. PDs associated with ADHD were significantly larger in women than in men for anxiety, depression, bipolar and personality disorders, for example depression in women: 24.4 (95% CI, 23.8-24.9) vs. in men: 13.1 (12.8-13.4). PDs were significantly larger in men for schizophrenia and substance use disorder (SUD), for example SUD in men: 23.0 (22.5-23.5) vs. in women: 13.7 (13.3-14.0). Between 5.6 and 16.5% of psychiatric disorders in the population were attributable to ADHD.

CONCLUSION

The association between ADHD and psychiatric comorbidities differed significantly among men and women. Clinicians treating adults with ADHD should be aware of these frequent and gender-specific comorbidities, such that early treatment can be offered.

β2-Adrenoreceptor is a regulator of the α-synuclein gene driving risk of Parkinson's disease

Copy number mutations implicate excess production of α-synuclein as a possibly causative factor in Parkinson's disease (PD). Using an unbiased screen targeting endogenous gene expression, we discovered that the β2-adrenoreceptor (β2AR) is a regulator of the α-synuclein gene (SNCA). β2AR ligands modulate SNCA transcription through histone 3 lysine 27 acetylation of its promoter and enhancers. Over 11 years of follow-up in 4 million Norwegians, the β2AR agonist salbutamol, a brain-penetrant asthma medication, was associated with reduced risk of developing PD (rate ratio, 0.66; 95% confidence interval, 0.58 to 0.76). Conversely, a β2AR antagonist correlated with increased risk. β2AR activation protected model mice and patient-derived cells. Thus, β2AR is linked to transcription of α-synuclein and risk of PD in a ligand-specific fashion and constitutes a potential target for therapies.

Association Between Methylphenidate and Amphetamine Use in Pregnancy and Risk of Congenital Malformations: A Cohort Study From the International Pregnancy Safety Study Consortium

IMPORTANCE

Given the rapidly increasing use of stimulant medications during pregnancy and among women of reproductive age who may become pregnant inadvertently, there is a need to better understand their safety.

OBJECTIVE

To examine the risk of congenital malformations associated with intrauterine exposure to stimulants.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study of the Medicaid-insured population in the United States nested in the 2000-2013 US Medicaid Analytic eXtract, with follow-up of safety signals detected in the Medicaid Analytic eXtract data using the Nordic Health registries (2003-2013) (Denmark, Finland, Iceland, Norway, and Sweden). A total of 1 813 894 publicly insured pregnancies in the United States and 2 560 069 singleton pregnancies in the 5 Nordic countries ending in live births were included. Relative risks were estimated accounting for underlying psychiatric disorders and other potential confounders. Relative risk estimates for the US and Nordic data were pooled using a fixed-effects meta-analytic approach. The study was conducted from July 1, 2015, to March 31, 2017.

EXPOSURES

Methylphenidate and amphetamines dispensed during the first trimester.

MAIN OUTCOMES AND MEASURES

Major congenital malformations and subgroup of cardiac malformations.

RESULTS

In the US data, of the 1 813 894 pregnancies evaluated, 35.0 per 1000 infants not exposed to stimulants were diagnosed as having congenital malformations, compared with 45.9 per 1000 infants for methylphenidate and 45.4 for amphetamines. For cardiac malformations, the risks were 12.7 (95% CI, 12.6-12.9), 18.8 (95% CI, 13.8-25.6), and 15.4 (95% CI, 12.5-19.0) per 1000 infants, respectively. The adjusted relative risks for methylphenidate were 1.11 (95% CI, 0.91-1.35) for any malformation and 1.28 (95% CI, 0.94-1.74) for cardiac malformations. No increased risks were observed for amphetamines: 1.05 (95% CI, 0.93-1.19) for any malformations and 0.96 (95% CI, 0.78-1.19) for cardiac malformations. Findings were confirmed in sensitivity analyses accounting for proxies of unmeasured confounders and increasing the specificity of the exposure and outcome definitions. Replication of the analyses for methylphenidate using the Nordic data including 2 560 069 pregnancies yielded a relative risk of 1.28 (95% CI, 0.83-1.97) for cardiac malformations, resulting in a pooled estimate of 1.28 (95% CI, 1.00-1.64).

CONCLUSIONS AND RELEVANCE

These findings suggest a small increase in the risk of cardiac malformations associated with intrauterine exposure to methylphenidate but not to amphetamines. This information is important when weighing the risks and benefits of alternative treatment strategies for attention-deficit/hyperactivity disorder in women of reproductive age and during early pregnancy.

Correction to: Associations between attention-deficit/hyperactivity disorder and autoimmune diseases are modified by sex: a population-based cross-sectional study

The article "Associations between attention-deficit/hyperactivity disorder and autoimmune diseases are modified by sex: a population-based cross-sectional study", written by Tor-Arne Hegvik, Johanne Telnes Instanes, Jan Haavik, Kari Klungsøyr and Anders Engeland, was originally published electronically on the publisher's internet portal (currently SpringerLink) on October 5, 2017 without open access due to an error by the Springer editorial office in the processing of this article. The authors had originally opted for open access.

Diabetes is associated with decreased migraine risk: A nationwide cohort study

Background Results from studies on diabetes and migraine risk are conflicting, which may be due to methodological limitations. Prospective studies with long follow-up could increase our understanding of the relationship between the two diseases. Method We performed a cohort study including the whole Norwegian population alive on 01.01.2004, using prescriptions registered in the Norwegian prescription database to identify individuals developing type 1 diabetes, type 2 diabetes and migraine during follow-up (10 years). We used Cox proportional hazards regression to estimate rate ratios with corresponding 95% confidence intervals for the effect of diabetes on migraine risk, adjusting for age, sex, and educational level. Result We identified 7,883 type 1 diabetes patients and 93,600 type 2 patients during the study period. Type 1 diabetes was significantly associated with a subsequent decreased migraine risk during follow-up in the age- and sex-adjusted analyses (0.74; 0.61-0.89). Type 2 diabetes was also associated with a significantly lower migraine risk (0.89; 0.83-0.95). Further adjustment for educational level yielded similar results for both diabetes. Conclusion Both type 1 and type 2 diabetes were significantly associated with a decreased risk of migraine. This suggests that diabetes or diabetes treatment may have a protective effect on the development of migraine.

Attention-Deficit/Hyperactivity Disorder in Offspring of Mothers With Inflammatory and Immune System Diseases

BACKGROUND

Prenatal inflammatory mechanisms may play a role in the pathogenesis of psychiatric disorders and could be relevant for attention-deficit/hyperactivity disorder (ADHD). We investigated maternal chronic somatic diseases with immune components as possible risk factors for ADHD in offspring.

METHODS

We performed a population-based nested case-control study by linking data from longitudinal Norwegian registers. We included all individuals born during the period 1967-2008 and alive at record linkage (2012). Individuals receiving ADHD medication during the years 2004-2012 were defined as patients with ADHD (N = 47,944), and all remaining individuals (N = 2,274,713) were defined as control subjects. The associations between maternal diseases and ADHD in offspring were analyzed using logistic regression models.

RESULTS

The following chronic diseases with immune components were related to ADHD in offspring: multiple sclerosis (adjusted odds ratio [OR] = 1.8; 95% confidence interval [CI] = 1.2-2.5), rheumatoid arthritis (adjusted OR = 1.7; 95% CI = 1.5-1.9), type 1 diabetes (adjusted OR = 1.6; 95% CI = 1.3-2.0), asthma (adjusted OR = 1.5; 95% CI = 1.4-1.6), and hypothyroidism (adjusted OR = 1.2; 95% CI = 1.1-1.4). In contrast, chronic hypertension and type 2 diabetes showed no significant associations. Estimates were almost unchanged with additional adjustment for parental ADHD, infant birth weight, and gestational age. Although point estimates for male and female offspring were different for some diseases (e.g., maternal asthma [adjusted OR = 1.7; 95% CI = 1.5-1.8 for female offspring and adjusted OR = 1.5; 95% CI = 1.4-1.6 for male offspring]), none of the associations differed significantly by offspring sex.

CONCLUSIONS

Several maternal somatic diseases with immune components were found to increase the risk of ADHD in offspring. The associations could involve several causal pathways, including common genetic predisposition and environmental factors, and increased insight into the mechanisms behind these relationships could enhance our understanding of the etiology of ADHD.