Sibling comparison designs: bias from non-shared confounders and measurement error

Adolescent Cardiorespiratory Fitness and Risk of Cancer in Late Adulthood: Nationwide Sibling-Controlled Cohort Study

Objective

To investigate whether the higher risks of certain cancers associated with high cardiorespiratory fitness can be explained by increased detection and unobserved confounders.

Design

Nationwide sibling-controlled cohort study of adolescents.

Setting

Sweden.

Participants

1 124 049 men of which 477 453 were full siblings, who underwent mandatory military conscription examinations between 1972 and 1995 at a mean age of 18.3 years.

Main outcome measures

Hazard ratios (HR) and 95% confidence intervals (CI) of overall cancer diagnosis and cancer mortality, and 14 site-specific cancers (diagnosis or death), as recorded in the Swedish National Patient Register or Cause of Death Register until 31 December 2023, modelled using flexible parametric regressions.

Results

Participants were followed until a median (maximum) age of 55.9 (73.5) years, during which 98 410 were diagnosed with cancer and 16 789 had a cancer-related death (41 293 and 6908 among full siblings respectively). The most common cancers were non-melanoma skin (27 105 diagnoses & 227 deaths) and prostate cancer (24 211 diagnoses & 869 deaths). In cohort analysis, those in the highest quartile of cardiorespiratory fitness had a higher risk of prostate (adjusted HR 1.10; 95% CI: 1.05 to 1.16) and skin cancer (e.g., non-melanoma HR 1.44; 1.37 to 1.50) compared to those in the lowest quartile, which led to a higher risk of any type of cancer diagnosis (HR 1.08; 1.06 to 1.11). However, those in the highest quartile had a lower risk of cancer mortality (HR 0.71; 0.67 to 0.76). When comparing full siblings, and thereby controlling for all behavioural, environmental, and genetic factors they share, the excess risk of prostate (HR 1.01; 0.90 to 1.13) and skin cancer (e.g., non-melanoma HR 1.09; 0.99 to 1.20) attenuated to the null. In contrast, the lower risk of overall cancer mortality was still statistically significant after control for such shared confounders (HR 0.78; 0.68 to 0.89). For other site-specific cancers, the influence of such confounding tended to vary, but none showed the same excess risk as prostate and non-melanoma skin cancer.

Conclusions

The association between high levels of adolescent cardiorespiratory fitness and excess risk of some cancers, such as prostate and non-melanoma skin cancer, appears to be fully explained by unobserved confounders shared between full siblings. However, the protective association with cancer mortality persists even after control for such confounding.

Neighborhood mobility and racial disparities in preterm birth: A sibling study in California

Recent work finds that upward neighborhood mobility-defined as reductions in neighborhood socioeconomic disadvantage due to moving-may improve birth outcomes. Less work, however, explores whether changes in socioeconomic context differentially impact birth outcomes by maternal race and ethnicity. In the US, mothers of minoritized racial and ethnic identity often experience worse neighborhood conditions and pregnancy outcomes than White mothers. Using a sibling-linked dataset, we examined whether neighborhood mobility corresponds with changes in preterm birth risk among Asian (N = 130,079), Black (N = 50,149), Hispanic (N = 429,938), and White (N = 233,428) mothers who delivered multiple live births in California between 2005 and 2015. We linked residential addresses at each birth to census-derived indices of neighborhood disadvantage and defined levels of neighborhood mobility as moving-induced changes in disadvantage between pregnancies. We mapped neighborhood mobility patterns and fit conditional logistic regression models estimating the odds of preterm birth in the sibling delivered after moving, controlling for the risk of preterm birth in the sibling delivered before moving, by maternal race and ethnicity. Dot density maps highlight racialized patterns of neighborhood mobility and segregation between Black and White mothers. Regression results show that Black and, in some cases, Asian and Hispanic mothers who experienced upward mobility (moves away from neighborhood disadvantage) exhibited reduced odds of preterm birth in the second delivery. Upward mobility did not reduce the odds of preterm birth among White mothers. Findings suggest that policies and programs that enable opportunities for neighborhood mobility may reduce persistent racial and ethnic disparities in adverse birth outcomes.

Familial confounding or measurement error? How to interpret findings from sibling and co-twin control studies

Epidemiological researchers often examine associations between risk factors and health outcomes in non-experimental designs. Observed associations may be causal or confounded by unmeasured factors. Sibling and co-twin control studies account for familial confounding by comparing exposure levels among siblings (or twins). If the exposure-outcome association is causal, the siblings should also differ regarding the outcome. However, such studies may sometimes introduce more bias than they alleviate. Measurement error in the exposure may bias results and lead to erroneous conclusions that truly causal exposure-outcome associations are confounded by familial factors. The current study used Monte Carlo simulations to examine bias due to measurement error in sibling control models when the observed exposure-outcome association is truly causal. The results showed that decreasing exposure reliability and increasing sibling-correlations in the exposure led to deflated exposure-outcome associations and inflated associations between the family mean of the exposure and the outcome. The risk of falsely concluding that causal associations were confounded was high in many situations. For example, when exposure reliability was 0.7 and the observed sibling-correlation was r = 0.4, about 30-90% of the samples (n = 2,000) provided results supporting a false conclusion of confounding, depending on how p-values were interpreted as evidence for a family effect on the outcome. The current results have practical importance for epidemiological researchers conducting or reviewing sibling and co-twin control studies and may improve our understanding of observed associations between risk factors and health outcomes. We have developed an app (SibSim) providing simulations of many situations not presented in this paper.

Substance use-related problems in mild intellectual disability: A Swedish nationwide population-based cohort study with sibling comparison

Background

Evidence for substance use-related problems in individuals with mild intellectual disability is sparse and mainly limited to selected psychiatric populations. We evaluated the risk of substance use-related problems in individuals with mild intellectual disability compared to the general population. Additionally, we have performed secondary sibling comparison analyses to account for familial confounding.

Methods

We conducted a population-based cohort study of individuals born in Sweden between 1973 and 2003. A total of 18,307 individuals with mild intellectual disability were compared to 915,350 reference individuals from the general population and 18,996 full siblings of individuals with mild intellectual disability. Information on mild intellectual disability and substance use-related problems was obtained from several Swedish national and regional school and healthcare registers. Substance use-related problems were measured via corresponding diagnostic and legal codes and included alcohol use disorder, drug use disorder, alcohol-related somatic disease, conviction for a substance-related crime, and substance-related death.

Results

Individuals with mild intellectual disability had a higher risk of any substance use-related problem compared to the general population (HR, 1.81; 95% CI, 1.72-1.91), both in males (HR, 1.76; 95% CI, 1.65-1.89) and females (HR, 1.89; 95% CI, 1.74-2.05). The risks of substance use-related problems were particularly elevated among individuals with mild intellectual disability and psychiatric comorbidities (HR, 2.21-8.24). The associations were attenuated in the sibling comparison models.

Conclusions

Individuals with mild intellectual disability, especially those with psychiatric comorbidity, are at an elevated risk of substance use-related problems. Familial factors shared by full siblings contribute considerably to the association between mild intellectual disability and substance use-related problems.

Maternal early pregnancy body mass index and bipolar disorder in the offspring

OBJECTIVES

To investigate the association between maternal early pregnancy body mass index (BMI) and offspring bipolar disorder (BPD).

METHODS

We conducted a nationwide cohort study among 1,507,056 non-malformed singleton live-births in Sweden born 1983-2004. Using national registries with prospectively recorded information, we followed participants for a BPD diagnosis from ages 13 to up to 35 years. We compared BPD risks by early pregnancy BMI using hazard ratios (HR) with 95% confidence intervals (CI) from adjusted Cox models. We also conducted sibling-controlled analyses among 874,047 full siblings.

RESULTS

There were 9970 BPD diagnoses. Risk of BPD was 0.72% through 25 years of age. Maternal early pregnancy BMI was positively associated with offspring BPD risk. Compared with normal BMI (18.5-24.9), adjusted HR (95% CI) for overweight (BMI 25-29.9), obesity grade 1 (BMI 30-34.9), and obesity grades 2-3 (BMI ≥35) were 1.08 (1.02, 1.15), 1.26 (1.14, 1.40), and 1.31 (1.07, 1.60), respectively. Adjusted HR per unit BMI was 1.015 (95% CI 1.009, 1.021). A similar trend was observed among siblings. Pregnancy and neonatal complications did not substantially mediate the association between maternal obesity (BMI ≥30) and offspring BPD.

CONCLUSIONS

Maternal BMI ≥25 is associated with offspring BPD risk in a dose-response manner.

The role of familial factors and neuroticism in the association between exposure to offensive behaviors at work and long-term sickness absence due to common mental disorders - a prospective twin study

OBJECTIVES

The aim of this study was to investigate associations between exposure to work-related violence/threats and harassment, and future sickness absence (SA) due to common mental disorders (CMDs), taking familial factors (shared genetics and early-life environment) and neuroticism into account.

METHODS

The study sample included 8795 twin individuals from the Swedish Twin Project of Disability Pension and Sickness Absence (STODS), including survey data from the Study of Twin Adults: Genes and Environment (STAGE). Self-reported work-related violence and/or threats as well as work-related harassment (including bullying) and national register data on SA due to CMDs were analyzed using standard logistic regression, and conditional logistic regression among complete twin pairs discordant on exposures. Individuals were followed for a maximum of 13 years. Interactions between neuroticism and exposures were assessed using both multiplicative and additive interaction analyses.

RESULTS

Exposure to work-related violence/threats was associated with higher odds of SA due to CMDs when adjusting for age, sex, marital status, children, education, type of living area, work characteristics, and symptoms of depression and burnout (OR 2.11, 95% CI 1.52-2.95). Higher odds of SA due to CMDs were also found for exposure to harassment (OR 1.52, 95% CI 1.10-2.11) and a combined indicator of exposure to violence/threats and/or harassment (OR 1.98, 95% CI 1.52-2.59), compared with the unexposed. Analyses of twins discordant on exposure, using the unexposed co-twin as reference, showed reduced ORs. These ORs were still elevated but no longer statistically significant, potentially due to a lack of statistical power. No multiplicative interaction was found between neuroticism and exposure to work-related violence/threats, or harassment. However, a statistically significant additive interaction was found between neuroticism and exposure to violence/threats, indicating higher odds of SA due to CMDs in the group scoring lower on neuroticism.

CONCLUSIONS

Exposure to work-related offensive behaviors was associated with SA due to CMDs. However, the results indicated that these associations may be partly confounded by familial factors. In addition, an interaction between exposure and neuroticism was suggested. Thus, when possible, future studies investigating associations and causality between offensive behaviors at work and mental health-related outcomes, should consider familial factors and neuroticism.

Association between maternal antidepressant use during pregnancy and the risk of autism spectrum disorder and attention deficit hyperactivity disorder in offspring

Prenatal antidepressant exposure has been reported to be associated with adverse neurodevelopmental outcomes, yet studies considering confounding factors in Asian populations are lacking. This study utilized a nationwide data base in Taiwan, enrolling all liveborn children registered in the National Health Insurance system between 2004 and 2016. Subjects were divided into two groups: antidepressant-exposed (n = 55,707)) and antidepressant-unexposed group (n = 2,245,689). The effect of antidepressant exposure during different trimesters on autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) was examined. Sibling controls and parallel comparisons by paternal exposure status were treated as negative controls. Additional sensitivity analyses were conducted to examine the effects of antidepressant exposure before and after pregnancy. Prenatal antidepressant exposure was associated with increased risks of ASD and ADHD in population-wide and adjusted analysis. However when comparing antidepressant-exposed children with their unexposed siblings, no differences were found for ASD (Hazard ratio [HR]: 1.04, 95% confidence interval [CI] 0.76-1.42 in first trimester; HR: 0.96, 95% CI 0.62-1.50 in second trimester; HR: 0.69, 95% CI 0.32-1.48 in third trimester) and ADHD (HR: 0.98, 95%CI 0.84-1.15 in first trimester; HR: 0.91, 95% CI 0.73-1.14 in second trimester; HR: 0.79, 95% CI 0.54-1.16 in third trimester). Increased risks for ASD and ADHD were also noted in paternal control, before and after pregnancy analyses. These results imply that the association between prenatal antidepressant exposure and ASD and ADHD is not contributed to by an intrauterine medication effect but more likely to be accounted for by maternal depression, genetic, and potential environmental factors.

Mental Disorders Among Adolescents and Young Adults With Cancer: A Canadian Population-Based and Sibling Cohort Study

PURPOSE

To compare the cumulative incidence of mental disorders among adolescents and young adults (AYAs) diagnosed with cancer with the general population and their unaffected siblings.

METHODS

A retrospective, population-based, matched cohort design was used to investigate the impact of cancer diagnosis on mental disorders among individuals age 15-39 diagnosed between 1989 and 2019. Two cancer-free cohorts were identified: matched population-based and sibling cohorts. Outcomes included incidence of mood and anxiety disorders, substance use disorders, suicide outcomes, psychotic disorders, and any of the preceding four categories within 5 years of cancer diagnosis. Competing risk regression was used to estimate adjusted subhazard ratios (aSHR) and 95% CIs.

RESULTS

Among 3,818 AYAs with cancer matched to the population-based cancer-free cohort, individuals with cancer were more likely to be diagnosed with incident mental disorders than those without cancer; the risk was highest immediately after a cancer diagnosis and decreased over time with aSHR [95% CI] for mood and anxiety disorders at 0-6 months (11.27 [95% CI, 6.69 to 18.97]), 6-12 months (2.35 [95% CI, 1.54 to 3.58]), and 12-24 months (2.06 [95% CI, 1.55 to 2.75]); for substance use disorders at 0-6 months (2.73 [95% CI, 1.90 to 3.92]); for psychotic disorders at 0-6 months (4.69 [95% CI, 2.07 to 10.65]); and for any mental disorder at 0-6 months (4.46 [95% CI, 3.41 to 5.85]), 6-12 months (1.56 [95% CI, 1.14 to 2.14]), and 12-24 months (1.7 [95% CI, 1.36 to 2.13]) postcancer diagnosis. In sibling comparison, cancer diagnosis was associated with a higher incidence of mood and anxiety and any mental disorder during first 6 months of cancer diagnosis.

CONCLUSION

AYAs with cancer experience a greater incidence of mental disorders after cancer diagnosis relative to population-based and sibling cohorts without cancer, primarily within first 2 years, underscoring the need to address mental health concerns during this period.

Evaluating the causal relationship between educational attainment and mental health

We investigate the causal relationship between educational attainment (EA) and mental health using two research designs. First, we compare the relationship between EA and 18 psychiatric diagnoses within sibship in Dutch national registry data (N=1.7 million), thereby controlling for unmeasured familial factors. Second, we apply two-sample Mendelian Randomization, which uses genetic variants related to EA or psychiatric diagnosis as instrumental variables, to test whether there is a causal relation in either direction. Our results suggest that lower levels of EA causally increase the risk of MDD, ADHD, alcohol dependence, GAD and PTSD diagnoses. We also find evidence of a causal effect of ADHD on EA. For schizophrenia, anorexia nervosa, OCD, and bipolar disorder, results were inconsistent across the different approaches, highlighting the importance of using multiple research designs to understand complex relationships such as between EA and mental health.

Combining Mendelian randomization with the sibling comparison design

Mendelian randomization (MR) is a popular epidemiologic study design that uses genetic variants as instrumental variables (IVs) to estimate causal effects, while accounting for unmeasured confounding. The validity of the MR design hinges on certain IV assumptions, which may sometimes be violated due to dynastic effects, population stratification, or assortative mating. Since these mechanisms act through parental factors it was recently suggested that the bias resulting from violations of the IV assumptions can be reduced by combing the MR design with the sibling comparison design, which implicitly controls for all factors that are constant within families. In this article, we provide a formal discussion of this combined MR-sibling design. We derive conditions under which the MR-sibling design is unbiased, and we relate these to the corresponding conditions for the standard MR and sibling comparison designs. We proceed by considering scenarios where all three designs are biased to some extent, and discuss under which conditions the MR-sibling design can be expected to have less bias than the other two designs. We finally illustrate the theoretical results and conclusions with an application to real data, in a study of low-density lipoprotein and diastolic blood pressure using data from the Swedish Twin Registry.

Understanding the impact of non-shared unmeasured confounding on the sibling comparison analysis

BACKGROUND

The sibling comparison analysis is used to deal with unmeasured confounding. It has previously been shown that in the presence of non-shared unmeasured confounding, the sibling comparison analysis may introduce substantial bias depending on the sharedness of the unmeasured confounder and the sharedness of the exposure. We aimed to improve the awareness of this challenge of the sibling comparison analysis.

METHODS

First, we simulated sibling pairs with an exposure, a confounder and an outcome. We simulated sibling pairs with no effect of the exposure on the outcome and with positive confounding. For varying degrees of sharedness of the confounder and the exposure and for varying prevalence of the exposure, we calculated the sibling comparison odds ratio (OR). Second, we provided measures for sharedness of selected treatments based on Danish health data.

RESULTS

The confounded sibling comparison OR was visualized for varying degrees of sharedness of the confounder and the exposure and for varying prevalence of the exposure. The confounded sibling comparison OR was seen to increase with increasing sharedness of the exposure and the confounded sibling comparison OR decreased with an increasing prevalence of exposure. Measures for sharedness of treatments based on Danish health data showed that treatments of chronic diseases have the highest sharedness and treatments of non-chronic diseases have the lowest sharedness.

CONCLUSIONS

Researchers should be aware of the challenge regarding non-shared unmeasured confounding in the sibling comparison analysis, before applying the analysis in non-randomized studies. Otherwise, the sibling comparison analysis may lead to substantial bias.

Reconsidering the failure model: Using a genetically controlled design to assess the spread of problems from reactive aggression to internalizing symptoms through peer rejection across the primary school years

According to the failure model (Patterson & Capaldi, 1990), peer rejection is the intermediary link between problem behaviors and internalizing symptoms. The present study tested the model with 464 monozygotic and same-sex dizygotic twin pairs (234 female, 230 male dyads). Teacher-reported reactive aggression and internalizing symptoms, and peer-reported peer rejection were collected at ages 6, 7, and 10 (from 2001 to 2008). Support for the failure model emerged in conventional non-genetically controlled analyses, but not twin-difference score analyses (which remove shared environmental and genetic contributions). Univariate biometric models attributed minimal variance in failure model variables to shared environmental factors, suggesting that genetic factors play an important unacknowledged role in developmental pathways historically ascribed to nonshared experiences in the failure model.

Risk factors for mood disorders among offspring of parents with bipolar disorder: Findings from a discordant-sibling study

The purpose of this naturalistic, prospective study was to identify risk factors for mood disorders in offspring of parents with bipolar disorder (BPD) using the discordant-sibling design by comparing premorbid psychopathology or symptoms, temperament, personality traits and coping style as well as the perception of family-related characteristics among affected and unaffected siblings within the same family. This approach controls for confounding by unmeasured genetic and environmental factors shared within families. Our sample comprised 24 families of a parent with BPD with at least one child that developed BPD or major depressive disorder (n = 31), and at least one child who did not. Offspring were followed for a mean duration of 16.2 (s.d: 4.6) years. Information was collected from the offspring themselves. Generalized linear mixed models only revealed differences in three dimensions of the Dimension of Temperament Survey-Revised (DOTS-R) version: Offspring with mood disorders scored higher on "Approach-withdrawal", "Rhythmicity for daily habits", and "Task orientation" than their unaffected siblings. The higher scores, and not lower scores as expected, on these temperament dimensions observed in offspring that subsequently developed mood disorders may reflect increased vulnerability, but they could also mirror premorbid mood swings or strategies to cope with them.

Exploring the differentiation of behavioural and emotional problems across childhood: A prospective longitudinal cohort study

Background

An individual's overall burden of behavioural and emotional problems across childhood is associated with increased likelihood of later mental health conditions. However, the relative extent of behavioural versus emotional problems - that is, the extent to which the domains are differentiated from one another - may provide additional information about who is at risk of developing a mental health condition. Here, we seek to validate differentiation as an independent predictor of later mental health conditions, and to explore its aetiology.

Methods

We analysed data from ~79,000 children in the population-based Norwegian Mother, Father, and Child Cohort Study, and linked health-care registries. In preregistered analyses, we modelled the extent and rate of differentiation of behavioural and emotional problems between ages 1.5-5 years, and estimated associations with later symptoms (age 8) and diagnoses (after age 8). We also explored the aetiology of differentiation by estimating associations with early life exposures and, in a subset of 23,945 full siblings, assessing the impact of accounting for unobserved familial confounding.

Results

Differentiation of behavioural and emotional problems was associated with later symptoms and diagnoses of mental health conditions, independent of total problems. Maternal at-risk drinking (β = 0.04 [0.02, 0.06]) and parental relationship problems (β = 0.04 [0.02, 0.05]) were associated with higher behavioural relative to emotional problems at age 5. Maternal prenatal distress (|β| = 0.04 [0.03, 0.06]), concurrent distress (|β| = 0.04 [0.02, 0.06]) and parental education (|β| = 0.05 [0.04, 0.07]) predicted higher emotional relative to behavioural problems at age 5. Estimates for maternal prenatal distress and at-risk drinking were consistent across both unadjusted and adjusted analyses accounting for unobserved familial risk.

Conclusions

Differentiation of behavioural and emotional problems in early childhood represents a valid source of inter-individual variability linked to the later emergence of psychopathology and may be relevant for early detection and prevention strategies for mental health.

Long-term adverse influence of smoking during pregnancy on height and body size of offspring at ten years old in the UK Biobank cohort

Background

To explore the long-term relationship between maternal smoking during pregnancy and early childhood growth in the UK Biobank cohort.

Methods

To estimate the effect of maternal smoking during pregnancy on offspring height and body size at ten years old, we performed binary logistic analyses and reported odds ratios (OR) as well as 95% confidence intervals (95%CIs). We also implemented the cross-contextual comparison study to examine whether such influence could be repeatedly observed among three different ethnicities in the UK Biobank cohort (n = 22,140 for White, n = 7094 for South Asian, and n = 5000 for Black). In particular, we conducted the sibling cohort study in White sibling cohort (n = 9953 for height and n = 7239 for body size) to control for unmeasured familial confounders.

Results

We discovered that children whose mothers smoked during pregnancy had greater risk of being shorter or plumper at age ten in the full UK Biobank White cohort, with 15.3% (95% CIs: 13.0%∼17.7%) higher risk for height and 32.4% (95%CIs: 29.5%∼35.4%) larger risk for body size. Similar associations were identified in the South Asian and Black ethnicities. These associations were robust and remained significant in the White sibling cohort (12.6% [95%CIs: 5.0%∼20.3%] for height and 36.1% [95%CIs: 26.3%∼45.9%] for body size) after controlling for family factors.

Conclusion

This study robustly confirms that maternal smoking during pregnancy can promote height deficit and obesity for offspring at ten years old. Our findings strongly encourage mothers to quit smoking during pregnancy for improving growth and development of offspring.

Educational attainment, health outcomes and mortality: a within-sibship Mendelian randomization study

BACKGROUND

Previous Mendelian randomization (MR) studies using population samples (population MR) have provided evidence for beneficial effects of educational attainment on health outcomes in adulthood. However, estimates from these studies may have been susceptible to bias from population stratification, assortative mating and indirect genetic effects due to unadjusted parental genotypes. MR using genetic association estimates derived from within-sibship models (within-sibship MR) can avoid these potential biases because genetic differences between siblings are due to random segregation at meiosis.

METHODS

Applying both population and within-sibship MR, we estimated the effects of genetic liability to educational attainment on body mass index (BMI), cigarette smoking, systolic blood pressure (SBP) and all-cause mortality. MR analyses used individual-level data on 72 932 siblings from UK Biobank and the Norwegian HUNT study, and summary-level data from a within-sibship Genome-wide Association Study including >140 000 individuals.

RESULTS

Both population and within-sibship MR estimates provided evidence that educational attainment decreased BMI, cigarette smoking and SBP. Genetic variant-outcome associations attenuated in the within-sibship model, but genetic variant-educational attainment associations also attenuated to a similar extent. Thus, within-sibship and population MR estimates were largely consistent. The within-sibship MR estimate of education on mortality was imprecise but consistent with a putative effect.

CONCLUSIONS

These results provide evidence of beneficial individual-level effects of education (or liability to education) on adulthood health, independently of potential demographic and family-level confounders.

Maternal pre-pregnancy BMI and offspring hyperactivity-inattention trajectories from 3 to 8 years in the EDEN birth cohort study

Evidence suggests obesity during pregnancy is associated with offspring attention-deficit hyperactivity disorder. However, studies have been limited to evaluating the association at a single age with inadequate data on important maternal lifestyle confounders and unmeasured familial confounding. The objective of this study was to examine the association between maternal pre-pregnancy body mass index (BMI) and child hyperactivity-inattention symptoms (HIS) at 3, 5 and 8 years. Data came from the EDEN mother-child cohort. Maternal pre-pregnancy BMI status (kg/m2) was calculated using pre-pregnancy weight and height (self-reported by mothers or measured by midwives). HIS were assessed by parental-report on the Strengths and Difficulties Questionnaire at 3, 5 and 8 years of age and used to derive developmental trajectories of HIS (n = 1428). Multivariate models were adjusted for confounders including socioeconomic status, maternal lifestyle behaviours (exercise, diet, smoking, alcohol), childcare and a stimulating home environment. Paternal BMI was used as a negative control. Compared to a normal pre-pregnancy BMI, pre-pregnancy maternal obesity was positively associated with increased odds of a high HIS trajectory between 3 and 8 years old in both unadjusted and adjusted logistic regression (adjusted odds ratio [aOR] 1.87 [95% CI 1.12, 3.12]). Pre-pregnancy overweight was not significantly associated after adjustment for confounders (aOR 1.32 [0.87, 2.01]). Maternal pre-pregnancy obesity, but not overweight, was associated with increased likelihood of a high HIS trajectory in children from 3 to 8 years old. This association persisted despite controlling for many important maternal lifestyle factors and paternal BMI. Further research is warranted to identify possible mediators involved.

Long-term risk of arrhythmias in patients with inflammatory bowel disease: A population-based, sibling-controlled cohort study

BACKGROUND

Although previous evidence has suggested an increased risk of cardiovascular disease (CVD) in patients with inflammatory bowel disease (IBD), its association with arrhythmias is inconclusive. In this study, we aimed to explore the long-term risk of arrhythmias in patients with IBD.

METHODS AND FINDINGS

Through a nationwide histopathology cohort, we identified patients with biopsy-confirmed IBD in Sweden during 1969 to 2017, including Crohn's disease (CD: n = 24,954; median age at diagnosis: 38.4 years; female: 52.2%), ulcerative colitis (UC: n = 46,856; 42.1 years; 46.3%), and IBD-unclassified (IBD-U: n = 12,067; 43.8 years; 49.6%), as well as their matched reference individuals and IBD-free full siblings. Outcomes included overall and specific arrhythmias (e.g., atrial fibrillation/flutter, bradyarrhythmias, other supraventricular arrhythmias, and ventricular arrhythmias/cardiac arrest). Flexible parametric survival models estimated hazard ratios (aHR) with 95% confidence intervals (95% CIs), after adjustment for birth year, sex, county of residence, calendar year, country of birth, educational attainment, number of healthcare visits, and cardiovascular-related comorbidities. Over a median of approximately 10 years of follow-up, 1,904 (7.6%) patients with CD, 4,154 (8.9%) patients with UC, and 990 (8.2%) patients with IBD-U developed arrhythmias, compared with 6.7%, 7.5%, and 6.0% in reference individuals, respectively. Compared with reference individuals, overall arrhythmias were increased in patients with CD [54.6 versus 46.1 per 10,000 person-years; aHR = 1.15 (95% CI [1.09, 1.21], P < 0.001)], patients with UC [64.7 versus 53.3 per 10,000 person-years; aHR = 1.14 (95% CI [1.10, 1.18], P < 0.001)], and patients with IBD-U [78.1 versus 53.5 per 10,000 person-years; aHR = 1.30 (95% CI [1.20, 1.41], P < 0.001)]. The increased risk persisted 25 years after diagnosis, corresponding to 1 extra arrhythmia case per 80 CD, 58 UC, and 29 IBD-U cases over the same period. Patients with IBD also had a significantly increased risk of specific arrhythmias, except for bradyarrhythmias. Sibling comparison analyses confirmed the main findings. Study limitations include lack of clinical data to define IBD activity, not considering the potential role of IBD medications and disease activity, and the potential residual confounding from unmeasured factors for arrhythmias.

CONCLUSIONS

In this study, we observed that patients with IBD were at an increased risk of developing arrhythmias. The excess risk persisted even 25 years after IBD diagnosis. Our findings indicate a need for awareness of this excess risk among healthcare professionals.

Changes in Residential Greenspace and Birth Outcomes among Siblings: Differences by Maternal Race

Growing research investigates the perinatal health benefits of greenspace in a mother's prenatal environment. However, evidence of associations between residential greenspace and birth outcomes remains mixed, limiting the relevance this work holds for urban policy and greening interventions. Past research relies predominantly on cross-sectional designs that are vulnerable to residential selection bias, and rarely tests effect modification by maternal race/ethnicity, which may contribute to heterogeneous findings. This study uses a rigorous, longitudinal sibling comparison design and maternal fixed effect analyses to test whether increases in maternal exposure to residential greenspace between pregnancies precede improved birth outcomes among non-Hispanic (NH) white (n = 247,285) and Black (n = 54,995) mothers (mean age = 28 years) who had at least two consecutive live births in California between 2005 and 2015. Results show that increases in residential greenspace correspond with higher birthweight (coef. = 75.49, 95% CI: 23.48, 127.50) among Black, but not white (coef. = -0.51, 95% CI: -22.90, 21.90), infants. Additional analyses suggest that prior evidence of perinatal benefits associated with residential greenspace among white mothers may arise from residential selection; no such bias is observed for Black mothers. Taken together, these findings support urban greening initiatives in historically under-resourced neighborhoods. Efforts to evenly distribute residential greenspace may reduce persistent racial disparities in birth outcomes, an important step towards promoting health equity across the life course.

Association of caesarean delivery with offspring health outcomes in full-cohort versus sibling-comparison studies: a comparative meta-analysis and simulation study

BACKGROUND

Full-cohort and sibling-comparison designs have yielded inconsistent results about the impacts of caesarean delivery on offspring health outcomes, with the effect estimates from the latter being more likely directed towards the null value. We hypothesized that the seemingly conservative results obtained from the sibling-comparison design might be attributed to inadequate adjustment for non-shared confounders between siblings, particularly maternal age at delivery.

METHODS

A systematic review and meta-analysis was first conducted. PubMed, Embase, and the Web of Science were searched from database inception to April 6, 2022. Included studies (1) examined the association of caesarean delivery, whether elective or emergency, with offspring health outcomes; (2) simultaneously conducted full-cohort and sibling-comparison analyses; and (3) reported adjusted effect estimates with 95% confidence intervals (95% CIs). No language restrictions were applied. Data were extracted by 2 reviewers independently. Three-level meta-analytic models were used to calculate the pooled odds ratios (ORs) and 95% CIs for caesarean versus vaginal delivery on multiple offspring health outcomes separately for full-cohort and sibling-comparison designs. Subgroup analyses were performed based on the method of adjustment for maternal age at delivery. A simulation study was then conducted. The simulated datasets were generated with some key parameters derived from the meta-analysis.

RESULTS

Eighteen studies involving 21,854,828 individuals were included. The outcomes assessed included mental and behavioral disorders; endocrine, nutritional and metabolic diseases; asthma; cardiorespiratory fitness; and multiple sclerosis. The overall pooled OR for estimates from the full-cohort design was 1.14 (95% CI: 1.11 to 1.17), higher than that for estimates from the sibling-comparison design (OR = 1.08; 95% CI: 1.02 to 1.14). Stratified analyses showed that estimates from the sibling-comparison design varied considerably across studies using different methods to adjust for maternal age at delivery in multivariate analyses, while those from the full-cohort design were rather stable: in studies that did not adjust maternal age at delivery, the pooled OR of full-cohort vs. sibling-comparison design was 1.10 (95% CI: 0.99 to 1.22) vs. 1.06 (95% CI: 0.85 to 1.31), in studies adjusting it as a categorical variable, 1.15 (95% CI: 1.11 to 1.19) vs. 1.07 (95% CI: 1.00 to 1.15), and in studies adjusting it as a continuous variable, 1.12 (95% CI: 1.05 to 1.19) vs. 1.12 (95% CI: 0.98 to 1.29). The severe underestimation bias related to the inadequate adjustment of maternal age at delivery in sibling-comparison analyses was fully replicated in the simulation study.

CONCLUSIONS

Sibling-comparison analyses may underestimate the association of caesarean delivery with multiple offspring health outcomes due to inadequate adjustment of non-shared confounders, such as maternal age at delivery. Thus, we should be cautious when interpreting the seemingly conservative results of sibling-comparison analyses in delivery-related studies.

Anxiety and depression in expectant parents: ART versus spontaneous conception

STUDY QUESTION

Do expectant parents experience increased anxiety and depression during pregnancies conceived through ART compared to spontaneous conception?

SUMMARY ANSWER

Among all expectant parents in the sample, those who conceived through ART reported overall lower levels of anxiety and depression in pregnancy compared to expectant parents who conceived spontaneously, while in the subsample of parents who conceived both through ART and spontaneous conception, expectant mothers experienced increased anxiety and depression in early pregnancy following ART compared to spontaneous conception.

WHAT IS KNOWN ALREADY

Previous research on expectant parents' psychosocial adjustment in response to ART has found mixed results, with some studies suggesting ART is associated with increased anxiety and depression, and other studies suggesting improved mental health or no relationship. Mixed findings may relate to the use of cross-sectional designs that do not account for confounding differences between groups, or variability in the timing of assessment.

STUDY DESIGN, SIZE, DURATION

This prospective cohort study used data from the Norwegian Mother, Father and Child Cohort Study (MoBa), which includes 2960 pregnant women who underwent ART and 108 183 women who conceived spontaneously. Of these, a subsample of expectant parents had two consecutive pregnancies with one pregnancy resulting from ART and one conceived spontaneously (n = 286 women, n = 211 partners). Women self-reported their composite symptoms of anxiety and depression at two timepoints during each pregnancy (gestational weeks 17 and 30). Their partners self-reported composite symptoms of anxiety and depression at 17 weeks gestation during each pregnancy. Couples reported their relationship satisfaction at 17 weeks gestation.

MAIN RESULTS AND THE ROLE OF CHANGE

Using a conventional full-cohort analysis we found that ART was associated with less total anxiety and depression and greater relationship satisfaction, compared to spontaneous conception among both women and men. However, in the subsample of parents who experienced both ART and spontaneous pregnancies, ART was associated with increased levels of maternal anxiety and depression at gestational age 17 weeks (M = 1.19), compared to spontaneous pregnancies (M = 1.15), 95% CI of the mean difference 0.006, 0.074. At 30 weeks gestation, anxiety and depression were similar across both types of pregnancies. Expectant fathers reported similar levels of anxiety and depression at 17 weeks gestation during both pregnancies. Among women relationship satisfaction was higher following ART conception than spontaneous conception.

LIMITATIONS, REASONS FOR CAUTION

There is potential for selection effects in the sample, as women who have conceived through both ART and spontaneous conception in their first two pregnancies are rare. In addition, several factors that may be important predictors of mental health in this context, such as previous miscarriages and long-term infertility, were not assessed in the current study.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that previous discrepancies in the literature may be related to inherent differences between the groups of parents receiving reproductive treatment and those who do not. This study addresses that limitation by prospectively comparing different types of pregnancies within the same expectant parents. Earlier inconsistencies may also relate to variations in gestational age when anxiety and depression were assessed. By examining symptoms at two timepoints in each pregnancy, we were able to examine the relation between gestational age and symptoms of anxiety and depression.

STUDY FUNDING/COMPETING INTEREST(S)

The MoBa is supported by the Norwegian Ministry of Health and the Norwegian Research Council/FUGE (grant number 151918/S10). This work was also supported by the Research Council of Norway grant number 288083 and 301004. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Antidepressants in pregnancy: applying causal epidemiological methods to understand service-use outcomes in women and long-term neurodevelopmental outcomes in exposed children

Background

Antidepressants are commonly prescribed during pregnancy, despite a lack of evidence from randomised trials on the benefits or risks. Some studies have reported associations of antidepressants during pregnancy with adverse offspring neurodevelopment, but whether or not such associations are causal is unclear.

Objectives

To study the associations of antidepressants for depression in pregnancy with outcomes using multiple methods to strengthen causal inference.

Design

This was an observational cohort design using multiple methods to strengthen causal inference, including multivariable regression, propensity score matching, instrumental variable analysis, negative control exposures, comparison across indications and exposure discordant pregnancies analysis.

Setting

This took place in UK general practice.

Participants

Participants were pregnant women with depression.

Interventions

The interventions were initiation of antidepressants in pregnancy compared with no initiation, and continuation of antidepressants in pregnancy compared with discontinuation.

Main outcome measures

The maternal outcome measures were the use of primary care and secondary mental health services during pregnancy, and during four 6-month follow-up periods up to 24 months after pregnancy, and antidepressant prescription status 24 months following pregnancy. The child outcome measures were diagnosis of autism, diagnosis of attention deficit hyperactivity disorder and intellectual disability.

Data sources

UK Clinical Practice Research Datalink.

Results

Data on 80,103 pregnancies were used to study maternal primary care outcomes and were linked to 34,274 children with at least 4-year follow-up for neurodevelopmental outcomes. Women who initiated or continued antidepressants during pregnancy were more likely to have contact with primary and secondary health-care services during and after pregnancy and more likely to be prescribed an antidepressant 2 years following the end of pregnancy than women who did not initiate or continue antidepressants during pregnancy (odds ratioinitiation 2.16, 95% confidence interval 1.95 to 2.39; odds ratiocontinuation 2.40, 95% confidence interval 2.27 to 2.53). There was little evidence for any substantial association with autism (odds ratiomultivariableregression 1.10, 95% confidence interval 0.90 to 1.35; odds ratiopropensityscore 1.06, 95% confidence interval 0.84 to 1.32), attention deficit hyperactivity disorder (odds ratiomultivariableregression 1.02, 95% confidence interval 0.80 to 1.29; odds ratiopropensityscore 0.97, 95% confidence interval 0.75 to 1.25) or intellectual disability (odds ratiomultivariableregression 0.81, 95% confidence interval 0.55 to 1.19; odds ratiopropensityscore 0.89, 95% confidence interval 0.61 to 1.31) in children of women who continued antidepressants compared with those who discontinued antidepressants. There was inconsistent evidence of an association between initiation of antidepressants in pregnancy and diagnosis of autism in offspring (odds ratiomultivariableregression 1.23, 95% confidence interval 0.85 to 1.78; odds ratiopropensityscore 1.64, 95% confidence interval 1.01 to 2.66) but not attention deficit hyperactivity disorder or intellectual disability; however, but results were imprecise owing to smaller numbers.

Limitations

Several causal-inference analyses lacked precision owing to limited numbers. In addition, adherence to the prescribed treatment was not measured.

Conclusions

Women prescribed antidepressants during pregnancy had greater service use during and after pregnancy than those not prescribed antidepressants. The evidence against any substantial association with autism, attention deficit hyperactivity disorder or intellectual disability in the children of women who continued compared with those who discontinued antidepressants in pregnancy is reassuring. Potential association of initiation of antidepressants during pregnancy with offspring autism needs further investigation.

Future work

Further research on larger samples could increase the robustness and precision of these findings. These methods applied could be a template for future pharmaco-epidemiological investigation of other pregnancy-related prescribing safety concerns.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (15/80/19) and will be published in full in Health Technology Assessment; Vol. 27, No. 15. See the NIHR Journals Library website for further project information.

Association of childhood infections and perinatal factors with ankylosing spondylitis: a Swedish nationwide case-control and sibling study

OBJECTIVES

To identify perinatal and early-life risk factors for ankylosing spondylitis (AS), controlling for family-shared confounding with a sibling comparison design.

METHODS

In this nationwide, register-based case-control study, we identified 5612 AS cases from the Swedish National Patient Register, and matched them with 22 042 individuals without inflammatory arthritis from the general population. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) of AS in relation to childhood infections and a broad range of perinatal factors including fetal growth. Significant associations were further tested in a sibling comparison analysis, including 3965 patients with AS and their 6070 siblings without a diagnosis of spondyloarthritis.

RESULTS

We found no statistically significant associations between any studied fetal growth-related factor or other perinatal factors and the risk of developing AS. In contrast, having older siblings (adjusted OR 1.12; 95% CI 1.04 to 1.22 for one vs no older sibling) and history of a childhood tonsillectomy (adjusted OR 1.30; 95% CI 1.13 to 1.49) were associated with AS in the case-control analysis, results that also held in the sibling comparison. Serious childhood infection and multiple birth were significantly associated with AS in the case-control sample, but estimates were attenuated in the sibling comparison.

CONCLUSIONS

Having older siblings and a history of tonsillectomy in childhood were independently associated with development of AS, even after adjustment for family-shared factors in a sibling comparison analysis. This strengthens the hypothesis that childhood infections play a role in the aetiology of AS.

Maternal cardiovascular disorders before and during pregnancy and offspring cardiovascular risk across the life course

Obesity, hypertension, type 2 diabetes mellitus and dyslipidaemia are highly prevalent among women of reproductive age and contribute to complications in >30% of pregnancies in Western countries. An accumulating body of evidence suggests that these cardiovascular disorders in women, occurring before and during their pregnancy, can affect the development of the structure, physiology and function of cardiovascular organ systems at different stages during embryonic and fetal development. These developmental adaptations might, in addition to genetics and sociodemographic and lifestyle factors, increase the susceptibility of the offspring to cardiovascular disease throughout the life course. In this Review, we discuss current knowledge of the influence of maternal cardiovascular disorders, occurring before and during pregnancy, on offspring cardiovascular development, dysfunction and disease from embryonic life until adulthood. We discuss findings from contemporary, large-scale, observational studies that provide insights into specific critical periods, evidence for causality and potential underlying mechanisms. Furthermore, we focus on priorities for future research, including defining optimal cardiovascular and reproductive health in women and men before their pregnancy and identifying specific embryonic, placental and fetal molecular developmental adaptations from early pregnancy onwards. Together, these approaches will help stop the intergenerational cycle of cardiovascular disease.

The Co-Twin Control Design: Implementation and Methodological Considerations

Establishing causal relationships in observational studies is an important step in research and policy decision making. The association between an exposure and an outcome can be confounded by multiple factors, often making it hard to draw causal conclusions. The co-twin control design (CTCD) is a powerful approach that allows for the investigation of causal effects while controlling for genetic and shared environmental confounding factors. This article introduces the CTCD and offers an overview of analysis methods for binary and continuous outcome and exposure variables. Tools for data simulation are provided, along with practical guidance and accompanying scripts for implementing the CTCD in R, SPSS, and Stata. While the CTCD offers valuable insights into causal inference, it depends on several assumptions that are important when interpreting CTCD results. By presenting a broad overview of the CTCD, this article aims to equip researchers with actionable recommendations and a comprehensive understanding of the design's strengths and limitations.

Parental background and daughters' and sons' educational outcomes - application of the Trivers-Willard hypothesis

This study uses Trivers-Willard hypothesis to explain the differences in daughters' and sons' educational outcomes by parental background. According to the Trivers-Willard hypothesis (TWH), parental support and investments for sons and daughters display an asymmetrical relationship according to parental status because of the different reproductive advantage of the sexes. It predicts that high-status parents support sons more than daughters, and low-status parents support daughters more than sons. In modern societies, where education is the most important mediator of status, the TW hypothesis predicts that sons from high-status families will achieve higher educational outcomes than daughters. Using cohorts born between 1987 and 1997 from the reliable full population Finnish register data that contain the data of over 600.000 individuals, children's educational outcomes were measured using data on school dropout rate, academic grade point average (GPA), and general secondary enrollment in their adolescence. OLS and sibling fixed-effect regression that permitted an examination of opposite-sex siblings' educational outcomes within the same family were applied. Sons with high family income and parental education, compared to daughters of the same family, have lower probability of dropping out of school and are more likely to enroll into academic secondary school track. In families with low parental education or income daughters have lower probability for school dropout and enroll more likely to academic school track related to sons of the same family. The effect of family background by sex can be interpreted to support TWH in dropout and academic school track enrollment but not in GPA.

Cardiovascular Risk Factor Disparities in Adult Survivors of Childhood Cancer Compared With the General Population

Background

It is unknown whether a history of childhood cancer modifies the established disparities in cardiovascular risk factors (CVRFs) observed in the general population.

Objectives

We sought to determine if disparities in CVRFs by race/ethnicity are similar among childhood cancer survivors compared with the general population.

Methods

The Childhood Cancer Survivor Study (CCSS) is a retrospective cohort with a longitudinal follow-up of 24,084 5-year survivors diagnosed between 1970 and 1999. Multivariable piecewise exponential regression estimated incidence rate ratios (IRRs) for hypertension, hyperlipidemia, diabetes, obesity, and ≥2 CVRFs by race/ethnicity. The CCSS sibling cohort and the National Health and Nutrition Examination Survey cohort were used to compare the sociodemographic-adjusted IRRs for same-race/same-ethnicity disparities.

Results

Non-Hispanic Black (NHB) (n = 1,092) and Hispanic (n = 1,405) survivors compared with non-Hispanic White (NHW) (n = 13,960) survivors reported a higher cumulative incidence of diabetes (8.4%, 9.7%, and 5.1%, respectively); obesity (47.2%, 48.9%, and 30.2%, respectively); multiple CVRFs (17.7%, 16.6%, and 12.3%, respectively); and, for NHB survivors, hypertension (19.5%, 13.6%, and 14.3%, respectively) by 40 years of age (P < 0.001). Controlling for sociodemographic and treatment factors compared with NHW survivors, IRRs for NHB were increased for hypertension (IRR: 1.4; 95% CI: 1.1-1.8), obesity (IRR: 1.7; 95% CI: 1.4-2.1), and multiple CVRFs (IRR: 1.6; 95% CI: 1.2-2.1). IRRs for Hispanic survivors were increased for diabetes (IRR: 1.8; 95% CI: 1.2-2.6) and obesity (IRR: 1.4; 95% CI: 1.2-1.7). The pattern of IRRs for CVRF differences was similar among CCSS sibling and National Health and Nutrition Examination Survey cohorts.

Conclusions

The higher burden of CVRFs among NHB and Hispanic survivors compared with NHW survivors was similar to the general population. The promotion of cardiovascular health equity is critical in this high-risk population.

Stressful life events increase the risk of major depressive episodes: A population-based twin study

BACKGROUND

Previous studies have found that stressful life events (SLEs) are associated with an increased risk of adult depression. However, many studies are observational in nature and limited by methodological issues, such as potential confounding by genetic factors. Genetically informative research, such as the co-twin control design, can strengthen causal inference in observational studies. Discrete-time survival analysis has several benefits and multilevel survival analysis can incorporate frailty terms (random effects) to estimate the components of the biometric model. In the current study, we investigated associations between SLEs and depression risk in a population-based twin sample (N = 2299).

METHODS

A co-twin control design was used to investigate the influence of the occurrence of SLEs on depression risk. The co-twin control design involves comparing patterns of associations in the full sample and within dizygotic (DZ) and monozygotic twins (MZ). Associations were modelled using discrete-time survival analysis with biometric frailty terms. Data from two time points were used in the analyses. Mean age at Wave 1 was 28 years and mean age at Wave 2 was 38 years.

RESULTS

SLE occurrence was associated with increased depression risk. Co-twin control analyses indicated that this association was at least in part due to the causal influence of SLE exposure on depression risk for event occurrence across all SLEs and for violent SLEs. A minor proportion of the total genetic risk of depression reflected genetic effects related to SLEs.

CONCLUSIONS

The results support previous research in implicating SLEs as important risk factors with probable causal influence on depression risk.

Associations of pregnancy complications and neonatal characteristics with bipolar disorder in the offspring: Nationwide cohort and sibling-controlled studies

OBJECTIVES

To investigate associations of neonatal characteristics and pregnancy complications with bipolar disorder (BPD) in offspring.

METHODS

We conducted a nationwide cohort study among 2,059,578 non-malformed singleton live-births in Sweden born 1983-2004. Using national registries with prospectively recorded information, we followed participants for a BPD diagnosis from 13 up to 34 years of age. We compared BPD risks between exposure categories using hazard ratios (HR) with 95% confidence intervals (CI) from adjusted Cox models. We also conducted sibling-controlled analyses among 1,467,819 full siblings.

RESULTS

There were 14,998 BPD diagnoses. Risk of BPD was 0.74% through 25 years of age. Very/extremely preterm birth (22 to 31 weeks) was related to increased BPD HRs in sibling-controlled analyses; compared with a gestational age of 37 weeks, adjusted HR (95% CI) for 31, 28, and 22 weeks were, respectively, 1.31 (0.99, 1.74), 2.09 (1.15, 3.79), and 5.74 (1.15, 28.63). Spontaneous but not medically indicated very/extremely preterm birth was associated with increased risk. Compared with vaginal birth, caesarean section birth was associated with 1.20 (1.08, 1.33) and 1.58 (1.06, 2.36) times higher BPD risk in general and sibling cohorts, respectively. Small-for-gestational age (SGA) birth was related to increased BPD HRs in general cohort and sibling analyses (HRs [95% CI] were 1.22 [1.06, 1.39] and 1.68 [1.13, 2.50], respectively); only term SGA was associated with increased risk. Head circumference-for-gestational age, gestational diabetes, preeclampsia, and placental abruption were not associated with BPD.

CONCLUSIONS

Very/extremely preterm birth, caesarean birth, and SGA are related to BPD incidence.

Associations Between General and Specific Psychopathology Factors and 10-Year Clinically Relevant Outcomes in Adult Swedish Twins and Siblings

Importance

General and specific factors of psychopathology are associated with future adverse outcomes, indicating that they might be useful for identifying individuals at greatest risk. However, it remains unknown if these associations are attributable to confounders that may influence both the psychopathology factors and later outcomes.

Objective

To analyze associations between psychopathology factors and clinically relevant outcomes within family pairs, adjusting for unmeasured confounds by applying co-twin control and sibling comparison designs.

Design, Setting, and Participants

This longitudinal cohort study with a follow-up range of 9 to 13 years included all Swedish twins born from 1959 to 1985 who participated in the Study of Twin Adults: Genes and Environment (60% response rate) and the oldest pair of all Swedish siblings born from 1959 to 1985 per the Multi-Generation Register. Twins were evaluated based on responses to a hierarchical factor model derived using multivariate statistics. Sibling pairs were evaluated based on psychiatric diagnoses per the Swedish National Patient Register. Information on outcome events and prescriptions were derived from the National Patient Register, Prescribed Drug Register, and Crime Register. Baseline assessment was in August 2005, and data were analyzed from January 2022 to February 2023.

Exposures

Hierarchical factor model consisting of 1 general and 4 specific factors fit to 48 psychiatric symptoms on which twin participants self-reported in 2005 and 1 general and 3 specific factors fit to 9 register-based psychiatric diagnoses assigned to sibling participants prior to 2005.

Main Outcomes and Measures

Outcomes consisted of 7 register-based events occurring after 2005, including suicidal behavior, substance overdoses, and criminal suspicion or convictions (data available until the end of 2013), and prescription of antidepressants, antialcohol or antiopioid medication, antipsychotics, and stimulants (data available until the end of 2017).

Results

The study included 32 328 twins (mean [SD] age, 34 [8] years; 16 076 [49.73%] male) and 1 942 106 siblings (mean [SD] age, 34 [7] years; 991 500 [51.05%] male). General psychopathology was significantly associated with all 7 outcomes within sibling pairs (mean within-pair odds ratio [OR], 2.28; 95% CI, 2.19-2.37) and dizygotic twin pairs (within-pairs OR, 1.65; 95% CI, 1.38-1.98) and with 3 outcomes within monozygotic twin pairs (mean within-pairs OR, 1.77; 95% CI, 1.35-2.36). Within sibling pairs, the specific internalizing factor was associated with antidepressant prescriptions (within-pairs OR, 1.65; 95% CI, 1.59-1.71), the specific substance misuse factor was associated prescription of antialcohol and antiopioid medication (within-pairs OR, 2.36; 95% CI, 2.20-2.54), and the specific psychotic factor was associated with antipsychotic medications (within-pairs OR, 1.61; 95% CI, 1.51-1.72). Similar results emerged within twin pairs.

Conclusion and Relevance

In this cohort study, general psychopathology was significantly associated with all 7 outcomes within sibling and dizygotic twin pairs and 3 outcomes within monozygotic twin pairs at 10 years. Within twin and sibling pairs, the specific factors were primarily associated with related outcomes. Several of the associations in this cohort study could not be attributed to unmeasured confounds shared by family members, suggesting that interventions toward broad psychopathology dimensions might help reduce the risk of future clinically relevant events.

Preterm Birth, Small for Gestational Age, and Large for Gestational Age and the Risk of Atrial Fibrillation Up to Middle Age

Importance

Adverse birth outcomes, including preterm birth, small for gestational age (SGA), and large for gestational age (LGA) are associated with increased risks of hypertension, ischemic heart disease, stroke, and heart failure, but knowledge regarding their associations with atrial fibrillation (AF) is limited and inconsistent.

Objective

To investigate whether preterm birth, SGA, or LGA are associated with increased risks of AF later in life.

Design, Setting, and Participants

This multinational cohort study included Danish, Swedish, and Finnish national health registries. Live singleton births in Denmark from 1978 through 2016, in Sweden from 1973 through 2014, and in Finland from 1987 through 2014, who were followed up until December 31, 2016, in Denmark, December 31, 2021, in Sweden, and December 31, 2014, in Finland were included. Data analyses were performed between January 2021 and August 2022.

Exposures

Preterm birth (less than 37 gestational weeks), SGA (less than 10th percentile birth weight for gestational age), and LGA (more than 90th percentile birth weight for gestational age) identified from medical birth registers.

Main Outcomes and Measures

Diagnosis of AF obtained from nationwide inpatient and outpatient registers. The study team ran multivariable Cox proportional hazard models and flexible parametric survival models to estimate hazard ratios (HRs) and 95% CIs for AF according to preterm birth, SGA, and LGA. Sibling analyses were conducted to control for unmeasured familial factors.

Results

The cohort included 8 012 433 study participants (maximum age, 49 years; median age, 21 years; male, 51.3%). In 174.4 million person-years of follow-up, 11 464 participants had a diagnosis of AF (0.14%; median age, 29.3 years). Preterm birth and LGA were associated with increased AF risk in both the full population cohort and in the sibling analyses; the multivariate HRs from the cohort analyses were 1.30 (95% CI, 1.18-1.42) and 1.55 (95% CI, 1.46-1.63), respectively. Preterm birth was more strongly associated with AF in childhood than in adulthood. Children born SGA had an increased risk of AF in the first 18 years of life but not afterwards.

Conclusions and Relevance

Preterm births and LGA births were associated with increased risks of AF up to middle age independently of familial confounding factors. Individuals born SGA had an increased AF risk only during childhood.

The challenges of selective fertility and carryover effects in within-sibship analyses: the effect of assisted reproductive technology on perinatal mortality as an example

BACKGROUND

Within-sibship analyses show lower perinatal mortality after assisted reproductive technology (ART) compared with natural conception (NC), a finding that appears biologically unlikely. We investigated whether this may be attributed to bias from selective fertility and carryover effects.

METHODS

Using data from national registries in Denmark (1994-2014), Finland (1990-2014) and Norway and Sweden (1988-2015), we studied 5 722 826 singleton pregnancies, including 119 900 ART-conceived and 37 590 exposure-discordant sibships. Perinatal mortality at the population level and within sibships was compared using multilevel logistic regression with random and fixed intercepts, respectively. We estimated selective fertility as the proportion of primiparous women with and without perinatal loss who had a second delivery, and carryover effects through bidirectional and crosswise associations.

RESULTS

Population analysis showed higher perinatal mortality among ART conception compared with NC (odds ratio 1.21, 95% CI 1.13 to 1.30), whereas within-sibship analysis showed the opposite (OR 0.36, 95% CI 0.31 to 0.43). Primiparous women with perinatal loss were more likely to give birth again (selective fertility) and to use ART in this subsequent pregnancy (carryover effects), resulting in strong selection of double-discordant sibships with death of the naturally conceived and survival of the ART-conceived sibling. After controlling for conception method and outcome in the first pregnancy, ART was not consistently associated with perinatal mortality in the second pregnancy.

CONCLUSIONS

Whereas population estimates may be biased by residual confounding, within-sibship estimates were biased by selective fertility and carryover effects. It remains unclear whether ART conception contributes to perinatal mortality.

Rheumatoid arthritis and the risk of postpartum psychiatric disorders: a Nordic population-based cohort study

BACKGROUND

Postpartum psychiatric disorders (PPD) are common complications of childbirth. A common explanation for their development is that the psychological, hormonal, and immune changes associated with pregnancy and parturition may trigger psychiatric symptoms postpartum. Rheumatoid arthritis (RA) is characterized by abnormalities in the activity of the hypothalamic-pituitary-adrenal axis and of the immune system, but its association with PPD is unknown. We analyzed whether women with RA before childbirth have an increased risk of PPD.

METHODS

We conducted a large population-based cohort study including mothers of singleton births in the Danish (1995-2015), Finnish (1997-2013), and Swedish Medical Birth Registers (2001-2013) (N = 3,516,849). We linked data from the Medical Birth Registers with data from several national socioeconomic and health registers. Exposure was defined as having a diagnosis of RA before childbirth, while the main outcome was a clinical diagnosis of psychiatric disorders 90 days postpartum. We analyzed the association between RA and PPD using Cox proportional hazard models, stratified by a personal history of psychiatric disorders.

RESULTS

Among women without a history of psychiatric disorders, the PPD incidence rate was 32.2 in the exposed and 19.5 per 1000 person-years in the unexposed group; women with RA had a higher risk of overall PPD than their unexposed counterparts [adjusted hazard ratio (HR) = 1.52, 95% confidence intervals (CI) 1.17 to 1.98]. Similar associations were also observed for postpartum depression (HR = 1.65, 95% CI 1.09 to 2.48) and other PPD (HR = 1.59, 95% CI 1.13 to 2.24). Among women with a history of psychiatric disorders, the incidence rate of overall PPD was 339.6 in the exposed and 346.6 per 1000 person-years in the unexposed group; RA was not associated with PPD. We observed similar associations between preclinical RA (RA diagnosed after childbirth) and PPD to those corresponding to clinical RA.

CONCLUSIONS

Rheumatoid arthritis was associated with an increased PPD risk in women without, but not in those with a psychiatric history. If our findings are confirmed in future studies, new mothers with RA may benefit from increased surveillance for new-onset psychiatric disorders postpartum.

Maternal depression or anxiety during pregnancy and offspring type 1 diabetes: a population-based family-design cohort study

INTRODUCTION

To investigate the association between maternal depression/anxiety during pregnancy and offspring type 1 diabetes, to assess the specific importance of exposure during pregnancy by comparing across different exposure periods before and/or after pregnancy, and to explore potential unmeasured familial confounding.

RESEARCH DESIGN AND METHODS

This was a population-based cohort including 1 807 809 offspring born in Sweden 2002-2019. From national registers, data were available on diagnosis or medication prescription for depression/anxiety in and around pregnancy, as well as incident cases of type 1 diabetes defined through diagnosis or insulin treatment. Associations were examined using flexible parametric and Cox regression models. Familial confounding was explored using paternal exposure as a negative control and by comparing offspring exposed to maternal depression/anxiety with their unexposed siblings.

RESULTS

For exposure during pregnancy, maternal depression/anxiety was associated with an increased risk of offspring type 1 diabetes onset after, but not before, 8 years of age (adjusted HR (aHR) 1.21 (95% CI 1.03 to 1.42]). Exposure occurring only during pregnancy was similarly associated to type 1 diabetes (aHR 1.24 (0.96 to 1.60)), whereas exposure occurring only before pregnancy was not (aHR 0.91 (0.64 to 1.30)). Associations were close to the null for paternal depression/anxiety (aHR 0.95 (0.72 to 1.25)), and point estimates were above 1 in sibling comparisons, although with wide CIs (aHR 1.36 (0.82 to 2.26)).

CONCLUSIONS

Maternal depression/anxiety specifically during pregnancy seems to be associated with offspring type 1 diabetes. Paternal negative control and sibling comparisons indicate that the results cannot entirely be explained by familial confounding.

Annual Research Review: Towards a deeper understanding of nature and nurture: combining family-based quasi-experimental methods with genomic data

Distinguishing between the effects of nature and nurture constitutes a major research goal for those interested in understanding human development. It is known, for example, that many parent traits predict mental health outcomes in children, but the causal processes underlying such associations are often unclear. Family-based quasi-experimental designs such as sibling comparison, adoption and extended family studies have been used for decades to distinguish the genetic transmission of risk from the environmental effects family members potentially have on one another. Recently, these designs have been combined with genomic data, and this combination is fuelling a range of exciting methodological advances. In this review we explore these advances - highlighting the ways in which they have been applied to date and considering what they are likely to teach us in the coming years about the aetiology and intergenerational transmission of psychopathology.

The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies

BACKGROUND

Body mass index (BMI) and obesity rates have increased sharply since the 1980s. While multiple epidemiologic studies have found that higher adolescent cognitive ability is associated with lower adult BMI, residual and unobserved confounding due to family background may explain these associations. We used a sibling design to test this association accounting for confounding factors shared within households.

METHODS AND FINDINGS

We used data from four United States general youth population cohort studies: the National Longitudinal Study of Youth 1979 (NLSY-79), the NLSY-79 Children and Young Adult, the NLSY 1997 (NLSY-97), and the Wisconsin Longitudinal Study (WLS); a total of 12,250 siblings from 5,602 households followed from adolescence up to age 62. We used random effects within-between (REWB) and residualized quantile regression (RQR) models to compare between- and within-family estimates of the association between adolescent cognitive ability and adult BMI (20 to 64 years). In REWB models, moving from the 25th to 75th percentile of adolescent cognitive ability was associated with -0.95 kg/m2 (95% CI = -1.21, -0.69) lower BMI between families. Adjusting for family socioeconomic position reduced the association to -0.61 kg/m2 (-0.90, -0.33). However, within families, the association was just -0.06 kg/m2 (-0.35, 0.23). This pattern of results was found across multiple specifications, including analyses conducted in separate cohorts, models examining age-differences in association, and in RQR models examining the association across the distribution of BMI. Limitations include the possibility that within-family estimates are biased due to measurement error of the exposure, confounding via non-shared factors, and carryover effects.

CONCLUSIONS

The association between high adolescent cognitive ability and low adult BMI was substantially smaller in within-family compared with between-family analysis. The well-replicated associations between cognitive ability and subsequent BMI may largely reflect confounding by family background factors.

Can frailty scores predict the incidence of cancer? Results from two large population-based studies

While chronological age is the single biggest risk factor for cancer, it is less clear whether frailty, an age-related state of physiological decline, may also predict cancer incidence. We assessed the associations of frailty index (FI) and frailty phenotype (FP) scores with the incidence of any cancer and five common cancers (breast, prostate, lung, colorectal, melanoma) in 453,144 UK Biobank (UKB) and 36,888 Screening Across the Lifespan Twin study (SALT) participants, who aged 38-73 years and had no cancer diagnosis at baseline. During a median follow-up of 10.9 and 10.7 years, 53,049 (11.7%) and 4,362 (11.8%) incident cancers were documented in UKB and SALT, respectively. Using multivariable-adjusted Cox models, we found a higher risk of any cancer in frail vs. non-frail UKB participants, when defined by both FI (hazard ratio [HR] = 1.22; 95% confidence interval [CI] = 1.17-1.28) and FP (HR = 1.16; 95% CI = 1.11-1.21). The FI in SALT similarly predicted risk of any cancer (HR = 1.31; 95% CI = 1.15-1.49). Moreover, frailty was predictive of lung cancer in UKB, although this association was not observed in SALT. Adding frailty scores to models including age, sex, and traditional cancer risk factors resulted in little improvement in C-statistics for most cancers. In a within-twin-pair analysis in SALT, the association between FI and any cancer was attenuated within monozygotic but not dizygotic twins, indicating that it may partly be explained by genetic factors. Our findings suggest that frailty scores are associated with the incidence of any cancer and lung cancer, although their clinical utility for predicting cancers may be limited.

Taking the problem of colliders seriously in the study of crime: A research note

Objectives

We provide a brief overview of collider bias and its implications for criminological research.

Methods

Owing to the nature of the topics studied, as well as the common data sources used to carry out much of this research, work in the field may often become vulnerable to a specific methodological problem known as collider bias. Collider bias occurs when exposure variables and outcomes independently cause a third variable, and this variable is included in statistical models. Colliders represent somewhat of a paradox in that there is scholarship discussing the issue, yet it has managed to remain a relatively cryptic threat compared to other sources of bias.

Results

We argue that, far from being an obscure concern, colliders almost certainly have pervasive impact in criminal justice and criminology.

Conclusion

We close by offering a general set of strategies for addressing the challenges posed by collider bias. While there is no panacea, there are better practices, many of which are underutilized in the disciplines that study crime and its attendant topics.

Type 1 diabetes and microscopic colitis: A nationwide matched case-control study in Sweden

BACKGROUND AND AIMS

Microscopic colitis (MC) is a colonic inflammatory condition associated with autoimmune dysfunction. Type 1 diabetes (T1D) is a chronic disease induced by autoimmune destruction of pancreatic β-cells. We aimed to examine the association between T1D and MC.

METHODS

A matched case-control study was conducted using the nationwide ESPRESSO cohort as study base. All biopsy-confirmed MC patients born after 1940 were identified and compared to biopsy-free individuals matched from the general population for T1D diagnosis using the Swedish National Patient Register. The T1D-MC association was estimated as odds ratios (ORs) and 95% confidence intervals (CIs) by conditional logistic models, considering differences by sex and MC subtype. Full sibling comparison and adjustment for MC-associated medications were also performed.

RESULTS

We identified 352 (3.7%) and 945 (2.0%) T1D diagnoses from 9,600 MC cases and 47,870 matched population controls, respectively, which corresponded to an overall OR of 1.79 (95% CI: 1.56-2.05). The association was stronger for collagenous colitis (OR, 2.15; 95% CI: 1.70-2.71) than lymphocytic colitis (OR, 1.62; 95% CI: 1.37-1.92) and remained statistically significant in full sibling comparison (OR, 1.46; 95%: 1.18-1.81). Medication adjustment attenuated the association to null among females (OR: 1.02; 95% CI: 0.82-1.27) but not among males (OR: 1.45; 95% CI: 1.11-1.90).

CONCLUSION

T1D diagnosis was almost 80% more prevalent in MC patients compared to general population. This positive association did not seem to be spurious due to residual confounding shared by full siblings but may relate to consumption of medications associated with MC onset.

Maternal Smoking During Pregnancy and Risk of Appendicitis in the Offspring

BACKGROUND

Existing evidence on the link between smoking and appendicitis is scarce and ambiguous. We therefore conducted a population-based cohort study in Denmark to investigate whether smoking during pregnancy is associated with an increased risk of appendicitis in offspring.

METHODS

We used the Danish Birth Registry to include all singletons born during 1991-2017 and to identify maternal smoking status during pregnancy. We followed the children from birth until date of appendicitis, emigration, death, or administrative end of study (31 December 2018), whichever came first. We calculated crude and adjusted hazard ratios (HRs) of appendicitis with 95% confidence intervals (CIs) comparing children of mothers who smoked during pregnancy to children of nonsmokers. Further, we conducted a bias analysis and sibling analysis.

RESULTS

We included 1,659,526 singletons of whom 19% were born to mothers who smoked during pregnancy. After maximum 28 years of follow-up, hazard rates for children of smokers were slightly higher than for children of nonsmokers [adjusted HR: 1.07 (95% CI = 1.04, 1.10)]. Stratification by sex revealed no association for males [adjusted HR: 1.02 (95% CI = 0.99, 1.06)], but a higher HR for females [adjusted HR: 1.13 (95% CI = 1.09, 1.18)]. This association increased with increasing length of follow-up, indicating that the association may be mediated by later-life exposures. The bias analysis indicated that misclassification of maternal smoking could attenuate a true association, while the sibling analysis showed no association.

CONCLUSIONS

Maternal smoking during pregnancy and appendicitis in the offspring may be associated.

Sibling Resemblance in Physical Activity Levels: The Peruvian Sibling Study on Growth and Health

Physical activity is associated with a host of positive health outcomes and is shaped by both genetic and environmental factors. We aim to: (1) estimate sibling resemblance in two physical activity phenotypes [total number of steps∙day^-1 and minutes for moderate steps per day (min∙day^-1)]; and (2) investigate the joint associations of individual characteristics and shared natural environment with intra-pair sibling similarities in each phenotype. We sampled 247 biological siblings from 110 nuclear families, aged 6-17 years, from three Peruvian regions. Physical activity was measured using pedometers and body mass index was calculated. In general, non-significant variations in the intraclass correlation coefficients were found after adjustment for individual characteristics and geographical area for both phenotypes. Further, no significant differences were found between the three sib-ship types. Sister-sister pairs tended to take fewer steps than brother-brother (β = -2908.75 ± 954.31). Older siblings tended to walk fewer steps (β = -81.26 ± 19.83), whereas body mass index was not associated with physical activity. Siblings living at high-altitude and in the Amazon region had higher steps/day (β = 2508.92 ± 737.94; β = 2213.11 ± 776.63, respectively) compared with their peers living at sea-level. In general, we found no influence of sib-types, body mass index, and/or environment on the two physical activity phenotypes.

Long-term risk of inflammatory bowel disease after endoscopic biopsy with normal mucosa: A population-based, sibling-controlled cohort study in Sweden

BACKGROUND

Although evidence suggests a persistently decreased risk of colorectal cancer for up to 10 years among individuals with a negative endoscopic biopsy result (i.e., normal mucosa), concerns have been raised about other long-term health outcomes among these individuals. In this study, we aimed to explore the long-term risk of inflammatory bowel disease (IBD) after an endoscopic biopsy with normal mucosa.

METHODS AND FINDINGS

In the present nationwide cohort study, we identified all individuals in Sweden with a lower or upper gastrointestinal (GI) biopsy of normal mucosa during 1965 to 2016 (exposed, n = 200,495 and 257,192 for lower and upper GI biopsy, respectively), their individually matched population references (n = 989,484 and 1,268,897), and unexposed full siblings (n = 221,179 and 274,529). Flexible parametric model estimated hazard ratio (HR) as an estimate of the association between a GI biopsy of normal mucosa and IBD as well as cumulative incidence of IBD, with 95% confidence interval (CI). The first 6 months after GI biopsy were excluded to avoid detection bias, surveillance bias, or reverse causation. During a median follow-up time of approximately 10 years, 4,853 individuals with a lower GI biopsy of normal mucosa developed IBD (2.4%) compared to 0.4% of the population references. This corresponded to an incidence rate (IR) of 20.39 and 3.39 per 10,000 person-years in the respective groups or 1 extra estimated IBD case among 37 exposed individuals during the 30 years after normal GI biopsy. The exposed individuals had a persistently higher risk of overall IBD (average HR = 5.56; 95% CI: 5.28 to 5.85), ulcerative colitis (UC, average HR = 5.20; 95% CI: 4.85 to 5.59) and Crohn's disease (CD, average HR = 6.99; 95% CI: 6.38 to 7.66) than their matched population references. In the sibling comparison, average HRs were 3.27 (3.05 to 3.51) for overall IBD, 3.27 (2.96 to 3.61) for UC, and 3.77 (3.34 to 4.26) for CD. For individuals with an upper GI biopsy of normal mucosa, the average HR of CD was 2.93 (2.68 to 3.21) and 2.39 (2.10 to 2.73), compared with population references and unexposed full siblings, respectively. The increased risk of IBD persisted at least 30 years after cohort entry. Study limitations include lack of data on indications for biopsy and potential residual confounding from unmeasured risk or protective factors for IBD.

CONCLUSIONS

Endoscopic biopsy with normal mucosa was associated with an elevated IBD incidence for at least 30 years. This may suggest a substantial symptomatic period of IBD and incomplete diagnostic examinations in patients with early IBD.

Gestational age at birth and cognitive outcomes in adolescence: population based full sibling cohort study

OBJECTIVE

To investigate the association between gestational age at birth and cognitive outcomes in adolescence.

DESIGN

Nationwide population based full sibling cohort study.

SETTING

Denmark.

PARTICIPANTS

1.2 million children born between 1 January 1986 and 31 December 2003, of whom 792 724 had one or more full siblings born in the same period.

MAIN OUTCOME MEASURES

Scores in written language (Danish) and mathematics examinations as graded by masked assessors at the end of compulsory schooling (ninth grade, ages 15-16 years), in addition to intelligence test score at military conscription (predominantly at age 18 years) for a nested sub-cohort of male adolescents. School grades were standardised as z scores according to year of examination, and intelligence test scores were standardised as z scores according to year of birth.

RESULTS

Among 792 724 full siblings in the cohort, 44 322 (5.6%) were born before 37+0 weeks of gestation. After adjusting for multiple confounders (sex, birth weight, malformations, parental age at birth, parental educational level, and number of older siblings) and shared family factors between siblings, only children born at <34 gestational weeks showed reduced mean grades in written language (z score difference -0.10 (95% confidence interval -0.20 to -0.01) for ≤27 gestational weeks) and mathematics (-0.05 (-0.08 to -0.01) for 32-33 gestational weeks, -0.13 (-0.17 to -0.09) for 28-31 gestational weeks, and -0.23 (-0.32 to -0.15) for ≤27 gestational weeks), compared with children born at 40 gestational weeks. In a nested sub-cohort of full brothers with intelligence test scores, those born at 32-33, 28-31, and ≤27 gestational weeks showed a reduction in IQ points of 2.4 (95% confidence interval 1.1 to 3.6), 3.8 (2.3 to 5.3), and 4.2 (0.8 to 7.5), respectively, whereas children born at 34-39 gestational weeks showed a reduction in intelligence of <1 IQ point, compared with children born at 40 gestational weeks.

CONCLUSIONS

Cognitive outcomes in adolescence did not differ between those born at 34-39 gestational weeks and those born at 40 gestational weeks, whereas those with a gestational age of <34 weeks showed substantial deficits in multiple cognitive domains.

Association Between Proton Pump Inhibitor Use During Early Pregnancy and Risk of Congenital Malformations

IMPORTANCE

Proton pump inhibitors (PPIs) are increasingly used during pregnancy; however, several observational studies have raised concerns about an increased risk of specific types of congenital malformations.

OBJECTIVE

To examine the association between PPI exposure during early pregnancy and the risk of congenital malformations.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study used data from the National Health Insurance Service-National Health Information Database of South Korea (2010-2020); sibling-controlled analyses were conducted to account for familial factors. A total of 2 696 216 pregnancies in women aged 19 to 44 years between June 1, 2011, and December 31, 2019, and their live-born infants were identified. Pregnant women who were exposed to known teratogens or who delivered infants with chromosomal abnormalities or genetic syndromes were excluded. Data on participant race and ethnicity were not collected because the National Health Information Database does not report this information.

EXPOSURES

Proton pump inhibitor use during the first trimester.

MAIN OUTCOMES AND MEASURES

Primary outcomes were major congenital malformations, congenital heart defects, cleft palate, hydrocephalus, and hypospadias. The subtypes of major congenital malformations and congenital heart defects were evaluated as exploratory outcomes. Propensity score fine stratification was used to control for potential confounders, and a weighted generalized linear model was used to estimate relative risks with 95% CIs.

RESULTS

Of 2 696 216 pregnancies (mean [SD] maternal age, 32.1 [4.2] years), 40 540 (1.5%; mean [SD] age, 32.4 [4.6] years) were exposed to PPIs during the first trimester. The absolute risk of major congenital malformations was 396.7 per 10 000 infants in PPI-exposed pregnancies and 323.4 per 10 000 infants in unexposed pregnancies. The propensity score-adjusted relative risks were 1.07 (95% CI, 1.02-1.13) for major congenital malformations, 1.09 (95% CI, 1.01-1.17) for congenital heart defects, 1.02 (95% CI, 0.72-1.43) for cleft palate, 0.94 (95% CI, 0.54-1.63) for hydrocephalus, and 0.77 (95% CI, 0.51-1.17) for hypospadias. In the sibling-controlled analyses, no associations were observed between PPI use and primary outcomes, including major congenital malformations (odds ratio, 1.05; 95% CI, 0.91-1.22) and congenital heart defects (odds ratio, 1.07; 95% CI, 0.88-1.30). A range of sensitivity analyses revealed results that were similar to the main findings.

CONCLUSIONS AND RELEVANCE

In this cohort study, the use of PPIs during early pregnancy was not associated with a substantial increase in the risk of congenital malformations, although small increased risks were observed for major congenital malformations and congenital heart defects; findings from sibling-controlled analyses revealed that PPIs were unlikely to be major teratogens. These findings may help guide clinicians and patients in decision-making about PPI use in the first trimester.

The Swedish medical birth register during five decades: documentation of the content and quality of the register

Pregnancy-related factors are important for short- and long-term health in mothers and offspring. The nationwide population-based Swedish Medical Birth Register (MBR) was established in 1973. The present study describes the content and quality of the MBR, using original MBR data, Swedish-language and international publications based on the MBR.The MBR includes around 98% of all births in Sweden. From 1982 onwards, the MBR is based on prospectively recorded information in standardized antenatal, obstetric, and neonatal records. When the mother and infant are discharged from hospital, this information is forwarded to the MBR, which is updated annually. Maternal data include information from first antenatal visit on self-reported obstetric history, infertility, diseases, medication use, cohabitation status, smoking and snuff use, self-reported height and measured weight, allowing calculation of body mass index. Birth and neonatal data include date and time of birth, mode of delivery, singleton or multiple birth, gestational age, stillbirth, birth weight, birth length, head circumference, infant sex, Apgar scores, and maternal and infant diagnoses/procedures, including neonatal care. The overall quality of the MBR is very high, owing to the semi-automated data extraction from the standardized regional electronic health records, Sweden's universal access to antenatal care, and the possibility to compare mothers and offspring to the Total Population Register in order to identify missing records. Through the unique personal identity numbers of mothers and live-born offspring, the MBR can be linked to other health registers. The Swedish MBR contains high-quality pregnancy-related information on more than 5 million births during five decades.

Maternal smoking during pregnancy, offspring smoking, adverse childhood events, and risk of major depression: a sibling design study

BACKGROUND

Evidence of a biologically plausible association between maternal smoking during pregnancy (MSP) and the risk of depression is discounted by null findings from two sibling studies. However, valid causal inference from sibling studies is subject to challenges inherent to human studies of MSP and biases particular to this design. We addressed these challenges in the first sibling study of MSP and depression conducted among adults past the peak age for the onset of depression, utilizing a prospectively collected and biologically validated measure of MSP and accounting for non-shared as well as mediating factors.

METHODS

We fit GEE binomial regression models to correct for dependence in the risk of depression across pregnancies of the same mother. We also fit marginal structural models (MSM) to estimate the controlled direct effect of MSP on depression that is not mediated by the offspring's smoking status. Both models allow the estimation of within- and between-sibling risk ratios.

RESULTS

The adjusted within-sibling risk ratios (RR_W) from both models (GEE: RR_W = 1.97, CI 1.16-3.32; MSM: RR_W = 2.08, CI 1.04-4.17) evinced an independent association between MSP and risk of depression. The overall effects from a standard model evinced lower associations (GEE: RR_T = 1.12, CI 0.98-1.28; MSM: RR_T = 1.18, CI 1.01-1.37).

CONCLUSIONS

Based on within-sibling information free of unmeasured shared confounders and accounting for a range of unshared factors, we found an effect of MSP on the offspring's risk of depression. Our findings, should they be replicated in future studies, highlight the importance of considering challenges inherent to human studies of MSP and affective disorders.