Win-loss parameters for right-censored event data, with application to recurrent events.

The win ratio has become a popular method for comparing multiple event data between two groups in clinical cohort studies. The win ratio compares the event data in prioritized order, where the first prioritized event is death and a typical example for the second prioritized event is hospitalization. Literature is sparse on inference for win and loss parameters, including the win ratio, for censored event data. Inference for two prioritized censored event times has been developed for independent right-censoring. Many clinical studies include recurrent event data such as hospitalizations. In this article, we suggest inference for win-loss parameters for death and a recurrent event outcome under independent right-censoring. The small sample properties of the proposed method are studied in a simulation study showing that the variance formula is accurate even for small samples. The method is applied on a data set from a randomized clinical trial.

Comparing performance between clinics of an embryo evaluation algorithm based on time-lapse images and machine learning.

PURPOSE: This article aims to assess how differences in maternal age distributions between IVF clinics affect the performance of an artificial intelligence model for embryo viability prediction and proposes a method to account for such differences. METHODS: Using retrospectively collected data from 4805 fresh and frozen single blastocyst transfers of embryos incubated for 5 to 6 days, the discriminative performance was assessed based on fetal heartbeat outcomes. The data was collected from 4 clinics, and the discrimination was measured in terms of the area under ROC curves (AUC) for each clinic. To account for the different age distributions between clinics, a method for age-standardizing the AUCs was developed in which the clinic-specific AUCs were standardized using weights for each embryo according to the relative frequency of the maternal age in the relevant clinic compared to the age distribution in a common reference population. RESULTS: There was substantial variation in the clinic-specific AUCs with estimates ranging from 0.58 to 0.69 before standardization. The age-standardization of the AUCs reduced the between-clinic variance by 16%. Most notably, three of the clinics had quite similar AUCs after standardization, while the last clinic had a markedly lower AUC both with and without standardization. CONCLUSION: The method of using age-standardization of the AUCs that is proposed in this article mitigates some of the variability between clinics. This enables a comparison of clinic-specific AUCs where the difference in age distributions is accounted for.

Regression models for censored time-to-event data using infinitesimal jack-knife pseudo-observations, with applications to left-truncation.

Jack-knife pseudo-observations have in recent decades gained popularity in regression analysis for various aspects of time-to-event data. A limitation of the jack-knife pseudo-observations is that their computation is time consuming, as the base estimate needs to be recalculated when leaving out each observation. We show that jack-knife pseudo-observations can be closely approximated using the idea of the infinitesimal jack-knife residuals. The infinitesimal jack-knife pseudo-observations are much faster to compute than jack-knife pseudo-observations. A key assumption of the unbiasedness of the jack-knife pseudo-observation approach is on the influence function of the base estimate. We reiterate why the condition on the influence function is needed for unbiased inference and show that the condition is not satisfied for the Kaplan-Meier base estimate in a left-truncated cohort. We present a modification of the infinitesimal jack-knife pseudo-observations that provide unbiased estimates in a left-truncated cohort. The computational speed and medium and large sample properties of the jack-knife pseudo-observations and infinitesimal jack-knife pseudo-observation are compared and we present an application of the modified infinitesimal jack-knife pseudo-observations in a left-truncated cohort of Danish patients with diabetes.

Replacing Red Meat with Other Nonmeat Food Sources of Protein is Associated with a Reduced Risk of Type 2 Diabetes in a Danish Cohort of Middle-Aged Adults.

BACKGROUND: Few cohort studies have modelled replacements of red meat with other sources of protein on subsequent risk of type 2 diabetes using dietary changes. OBJECTIVES: To determine whether replacing red meat with other food sources of protein is associated with a lower risk of type 2 diabetes. METHODS: We used data from the Danish Diet, Cancer, and Health cohort (n = 39,437) of middle-aged (55-72 years old) men and women who underwent 2 dietary assessments roughly 5 years apart to investigate dietary changes. The pseudo-observation method was used to model the average exposure effect of decreasing the intake of red meat while increasing the intake of either poultry, fish, eggs, milk, yogurt, cheese, whole grains, or refined grains on the subsequent 10-year risk of developing type 2 diabetes, compared with no changes in the intakes of these foods. RESULTS: Replacing 1 serving/day (100 g/day) of red meat with 1 serving/day of eggs [risk difference (RD), -2.7%; 95% CI: -4.0 to -1.1%; serving size: 50 g/day], milk (RD, -1.2%; 95% CI: -2.1 to -0.4%; 200 g/day), yogurt (RD, -1.5%; 95% CI: -2.4 to -0.7%; 70 g/day), whole grains (RD, -1.7%; 95% CI: -2.5 to -0.9%; 30 g/day), or refined grains (RD, -1.2%; 95% CI: -2.0 to -0.3%; 30 g/day) was associated with a reduced risk of type 2 diabetes. Analyses of replacements with poultry or cheese, but not fish, also suggested a lower risk, but with wide CIs. After further adjustment for potential mediators (BMI, waist circumference, and history of hypertension or hypercholesterolemia), only the replacement with eggs was associated with a reduced risk (RD, -1.7%; 95% CI: -3.0 to -0.5%; 50 g/day). CONCLUSIONS: Replacing red meat with eggs in middle-aged adults may reduce the risk of type 2 diabetes. In models not adjusted for potential mediators, replacing red meat with milk, yogurt, whole grains, or refined grains was also associated with a reduced risk of type 2 diabetes.

Changes in intake of dairy product subgroups and risk of type 2 diabetes: modelling specified food substitutions in the Danish Diet, Cancer and Health cohort.

PURPOSE: We investigated the association between an increased intake of one dairy product subgroup at the expense of another within a 5-year period and the subsequent 10-year risk of type 2 diabetes. METHODS: The cohort included 39,393 adults with two measurements of diet assessed using food frequency questionnaires (FFQ) administered in 1993-1997 and 1999-2003. Dairy products were milk (skimmed, semi-skimmed, whole fat), buttermilk, low-fat yogurt, whole-fat yogurt, cheese and butter. Type 2 diabetes cases were ascertained from the Danish National Diabetes Register. The pseudo-observation method was used to calculate risk differences (RD) with 95% confidence intervals (CI). The data were analysed in age strata to fulfil the assumption of independent entry. RESULTS: Among participants aged 56-59 years at completion of the follow-up FFQ, increased intake of whole-fat yogurt in place of skimmed, semi-skimmed or whole-fat milk was associated with a reduced risk (RD% [95% CI]: - 0.8% [- 1.3, - 0.2]; - 0.6% [- 1,1, - 0.1]; - 0.7 [- 1.2, - 0.1]; per 50 g/d, respectively). Among participants aged 60-64 and 65-72, substitution of skimmed milk for semi-skimmed milk was associated with an increased risk of type 2 diabetes (0.5% [0.2, 0.7]; 0.4% [0.1, 0.7]; per 50 g/d, respectively). Similar patterns of associations were found after adjustment for potential mediators. CONCLUSION: Our results suggest that substitution of whole-fat yogurt for milk among those aged 56-59 decreases risk of type 2 diabetes and substitution of skimmed milk for semi-skimmed milk may increase the risk among those aged 60-64 and 65-72.

Neonatal jaundice and autism spectrum disorder: a systematic review and meta-analysis.

BACKGROUND: Two meta-analyses concluded that jaundice was associated with an increased risk of autism. We hypothesize that these findings were due to methodological limitations of the studies included. Neonatal jaundice affects many infants and risks of later morbidity may prompt physicians towards more aggressive treatment. METHODS: To conduct a systematic literature review and a meta-analysis of the association between neonatal jaundice and autism with particular attention given to low risk of bias studies. Pubmed, Scopus, Embase, Cochrane, and Google Scholar were searched for publications until February 2019. Data was extracted by use of pre-piloted structured sheets. Low risk of bias studies were identified through predefined criteria. RESULTS: A total of 32 studies met the inclusion criteria. The meta-analysis of six low risk of bias studies showed no association between neonatal jaundice and autism; cohort studies risk ratio 1.09, 95% CI, 0.99-1.20, case-control studies odds ratio 1.29 95% CI 0.95, 1.76. Funnel plot of all studies suggested a high risk of publication bias. CONCLUSIONS: We found a high risk of publication bias, selection bias, and potential confounding in all studies. Based on the low risk of bias studies there was no convincing evidence to support an association between neonatal jaundice and autism. IMPACT: Meta-analysis of data from six low risk of bias studies indicated no association between neonatal jaundice and autism spectrum disorder. Previous studies show inconsistent results, which may be explained by unadjusted confounding and selection bias. Funnel plot suggested high risk of publication bias when including all studies. There is no evidence to suggest jaundice should be treated more aggressively to prevent autism.

Food substitution models for nutritional epidemiology.

The advantage of using specified substitution analysis in nutritional epidemiology has been clearly demonstrated in studies of macronutrient intake and disease risk. However, the method has not been widely applied in studies of food intake. The aim of this article is to describe and compare the interpretation and application of different food substitution models in epidemiologic studies on diet and disease development. Both theoretically and in the context of a specific example, we discuss methodologic issues to be considered, including modeling of food substitutions using diet at a single time point or at multiple time points (focusing on dietary changes), choice of substitution unit, adjustment for total energy intake, and adjustment for confounding. We argue that specified food substitution analyses can be used to identify optimal food composition of the diet and that these analyses are thus highly relevant to inform public health policy decision makers.

Repeat pulmonary vein isolation in patients with atrial fibrillation: low ablation index is associated with increased risk of recurrent arrhythmia.

OBJECTIVES: We aimed to investigate the predictors of recurrent arrhythmia after repeated pulmonary vein isolation (PVI) performed in the era of contact force without additional substrate ablation. One of the predictors studied, ablation index (AI), incorporates power, contact force, and time in a weighted formula and is reported to predict lesion size in animals. Design. Consecutive patients (n = 108) undergoing repeat PVI without additional substrate modification using a contact force sensing catheter were included retrospectively at a tertiary center. All ablation points were analyzed offline. A new variable, normalized AI (AI corrected for the location of the lesion-anterior vs. posterior) was calculated. The patients were systematically followed with clinical visit and 12-lead ECG as well as review of the regional electronic patient files at 3 and 12 months after the procedure with 5-day Holter at 12 months. Results. Electrical reconnection to at least one pulmonary vein (PV) was seen in 97% of the patients. The recurrence rate was 35%. There was no recurrence in patients with nAI above 1.15 (n = 26). Patients with electrical reconnection of up to two PVs had a higher risk of recurrence compared with patients having electrical reconnection of three or four PVs (p = .003), and this risk was especially high in patients with persistent atrial fibrillation (69 [39-91]%). Conclusions. The risk of recurrence is higher in patients with ablations performed with low levels of AI and in patients with reconnection to up to two PVs. Our data may indicate the need for higher target levels of AI during repeat PVI than normally used during de-novo PVI.

Cumulative risk regression in case-cohort studies using pseudo-observations.

Case-cohort studies are useful when information on certain risk factors is difficult or costly to ascertain. Particularly, a case-cohort study may be well suited in situations where several case series are of interest, e.g. in studies with competing risks, because the same sub-cohort may serve as a comparison group for all case series. Previous analyses of this kind of sampled cohort data most often involved estimation of rate ratios based on a Cox regression model. However, with competing risks this method will not provide parameters that directly describe the association between covariates and cumulative risks. In this paper, we study regression analysis of cause-specific cumulative risks in case-cohort studies using pseudo-observations. We focus mainly on the situation with competing risks. However, as a by-product, we also develop a method by which absolute mortality risks may be analyzed directly from case-cohort survival data. We adjust for the case-cohort sampling by inverse sampling probabilities applied to a generalized estimation equation. The large-sample properties of the proposed estimator are developed and small-sample properties are evaluated in a simulation study. We apply the methodology to study the effect of a specific diet component and a specific gene on the absolute risk of atrial fibrillation.

Depression and Uptake of Oral Anticoagulation Therapy in Patients With Atrial Fibrillation: A Danish Nationwide Cohort Study.

BACKGROUND: Oral anticoagulation therapy (OAT) in patients with atrial fibrillation (AF) is a highly important preventive intervention, perhaps especially in those with comorbid depression, who have a worse prognosis. However, OAT may pose particular challenges in depressed patients. OBJECTIVES: To assess whether AF patients with depression have lower OAT uptake. METHODS: This nationwide register-based 2005-2016 cohort study of all Danes with AF and OAT indication (CHA2DS2VASc stroke risk score ≥2) assessed OAT initiation within 90 days in those with incident AF (N=147,162) and OAT prevalence in those with prevalent AF (N=192,656). The associations of depression with both outcomes were estimated in regression analyses with successive adjustment for socioeconomic characteristics and somatic and psychiatric comorbidity. RESULTS: Comorbid depression was significantly associated with lower frequency of OAT initiation in incident AF patients {adjusted proportion differences (aPDs): -6.6% [95% confidence interval (CI), -7.4 to -5.9]} and lower prevalence of OAT [aPD: -4.2% (95% CI, -4.7 to -3.8)] in prevalent AF patients. Yet, the OAT uptake increased substantially during the period, particularly in depressed patients [aPD for OAT prevalence in 2016: -0.8% (95% CI, -1.6 to -0.0)]. CONCLUSIONS: Comorbid depression was associated with a significantly lower OAT uptake in patients with AF, which questions whether depressed patients receive sufficient support to manage this consequential cardiac condition. However, a substantial increase in the overall OAT uptake and a decrease of the depression-associated deficit in OAT were seen over the period during which OAT was developed through the introduction of new oral anticoagulation therapy.

Pubertal development after unintended intrauterine exposure to oral contraceptives: a nationwide cohort study.

OBJECTIVE: To study the associations between exposure to oral contraceptives before conception and early in pregnancy and pubertal timing in boys and girls. DESIGN: Population-based cohort study. SETTING: Not applicable. PATIENT(S): Overall, 15,800 children (70%) born during 2000-2003 into the Danish National Birth Cohort were categorized according to maternal use of combined oral contraceptive pills or progestin-only pills reported around gestational week 17: no exposure (reference), exposure 4 months before conception, and exposure in early pregnancy. Children self-assessed pubertal status using Web-based questionnaires from 11 years and biannually throughout puberty. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Adjusted mean age differences (months) for attaining individual pubertal milestones and overall pubertal timing. Proportion mediated by prepubertal body mass index. RESULT(S): In boys, intrauterine exposure to oral contraceptives showed a tendency toward slightly earlier mean age for voice break (months, -3.8; 95% confidence interval [CI] -6.5, -1.0) and first ejaculation (months, -2.9; 95% CI -5.9, 0.1) and a mean difference of -1.4 months (95% CI -3.3, 0.4) for overall pubertal timing. Girls with intrauterine exposure tended to have slightly earlier age at menarche (months, -1.9; 95% CI -4.0, 0.3) and Tanner breast stages and had a mean difference of -0.9 months (95% CI -2.7, 1.0) for overall pubertal timing. Exposure before conception was not associated with pubertal timing. Prepubertal body mass index did not play a mediating role. CONCLUSION(S): This study shows some evidence that intrauterine exposure to oral contraceptives might slightly affect pubertal timing.

Association of Genetic and Environmental Factors With Autism in a 5-Country Cohort.

Importance: The origins and development of autism spectrum disorder (ASD) remain unresolved. No individual-level study has provided estimates of additive genetic, maternal, and environmental effects in ASD across several countries. Objective: To estimate the additive genetic, maternal, and environmental effects in ASD. Design, Setting, and Participants: Population-based, multinational cohort study including full birth cohorts of children from Denmark, Finland, Sweden, Israel, and Western Australia born between January 1, 1998, and December 31, 2011, and followed up to age 16 years. Data were analyzed from September 23, 2016 through February 4, 2018. Main Outcomes and Measures: Across 5 countries, models were fitted to estimate variance components describing the total variance in risk for ASD occurrence owing to additive genetics, maternal, and shared and nonshared environmental effects. Results: The analytic sample included 2 001 631 individuals, of whom 1 027 546 (51.3%) were male. Among the entire sample, 22 156 were diagnosed with ASD. The median (95% CI) ASD heritability was 80.8% (73.2%-85.5%) for country-specific point estimates, ranging from 50.9% (25.1%-75.6%) (Finland) to 86.8% (69.8%-100.0%) (Israel). For the Nordic countries combined, heritability estimates ranged from 81.2% (73.9%-85.3%) to 82.7% (79.1%-86.0%). Maternal effect was estimated to range from 0.4% to 1.6%. Estimates of genetic, maternal, and environmental effects for autistic disorder were similar with ASD. Conclusions and Relevance: Based on population data from 5 countries, the heritability of ASD was estimated to be approximately 80%, indicating that the variation in ASD occurrence in the population is mostly owing to inherited genetic influences, with no support for contribution from maternal effects. The results suggest possible modest differences in the sources of ASD risk between countries.

Recurrence Risk of Autism in Siblings and Cousins: A Multinational, Population-Based Study.

OBJECTIVE: Familial recurrence risk is an important population-level measure of the combined genetic and shared familial liability of autism spectrum disorder (ASD). Objectives were to estimate ASD recurrence risk among siblings and cousins by varying degree of relatedness and by sex. METHOD: This is a population-based cohort study of livebirths from 1998 to 2007 in California, Denmark, Finland, Israel, Sweden and Western Australia followed through 2011 to 2015. Subjects were monitored for an ASD diagnosis in their older siblings or cousins (exposure) and for their ASD diagnosis (outcome). The relative recurrence risk was estimated for different sibling and cousin pairs, for each site separately and combined, and by sex. RESULTS: During follow-up, 29,998 cases of ASD were observed among the 2,551,918 births used to estimate recurrence in ASD and 33,769 cases of childhood autism (CA) were observed among the 6,110,942 births used to estimate CA recurrence. Compared with the risk in unaffected families, there was an 8.4-fold increase in the risk of ASD following an older sibling with ASD and a 17.4-fold increase in the risk of CA following an older sibling with CA. A 2-fold increase in the risk for cousin recurrence was observed for the 2 disorders. There also was a significant difference in sibling ASD recurrence risk by sex. CONCLUSION: The present estimates of relative recurrence risks for ASD and CA will assist clinicians and families in understanding autism risk in the context of other families in their population. The observed variation by sex underlines the need to deepen the understanding of factors influencing ASD familial risk.

Birth seasonality and risk of autism spectrum disorder.

Season of birth has been hypothesized to be a risk factor for autism spectrum disorder (ASD). However, the evidence has been mixed and limited due to methodological challenges. We examine ASD birth trends for 5,464,628 births across 5 countries. ASD birth prevalence data were obtained from the International Collaboration for Autism Registry Epidemiology database, including children born in Denmark, Finland, Norway, Sweden, and Western Australia. Empirical mode decomposition and cosinor modeling were used to assess seasonality. We show seasonal variation in ASD births for the countries of Finland and Sweden. There was a modest increase in risk for children born in the fall and a modest decrease in risk for children born in the spring. Solar radiation levels around conception and the postnatal period were inversely correlated with seasonal trends in ASD risk. In the first multinational study of birth seasonality of ASD, there was evidence supporting the presence of seasonal trends in Finland and Sweden. The observations that risk was highest for fall births (i.e., conceived in the winter) and lowest for spring births (i.e., conceived in the summer), and sunlight levels during critical neurodevelopmental periods explained much of the seasonal trends, are consistent with the hypothesis that a seasonally fluctuating risk factor may influence risk of ASD.

Parental Age and Differential Estimates of Risk for Neuropsychiatric Disorders: Findings From the Danish Birth Cohort.

OBJECTIVE: Parental age at birth has been shown to affect the rates of a range of neurodevelopmental disorders, but the understanding of the mechanisms through which it mediates different outcomes is still lacking. A population-based cohort was used to assess differential effects of parental age on estimates of risk across pediatric-onset neuropsychiatric disorders: autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), and Tourette's disorder/chronic tic disorder (TD/CT). METHOD: The study cohort included all singleton births in Denmark from 1980 through 2007 with full information on parental ages (N = 1,490,745) and was followed through December 31, 2013. Cases of ASD, ADHD, OCD, and TD/CT were identified in the Danish Psychiatric Central Register and the National Patient Register. Associations with parental age were modeled using a stratified Cox regression, allowing for changes in baseline diagnostic rates across time. RESULTS: Younger parental age was significantly associated with increased estimates of risk for ADHD and TD/CT, whereas older parental age was associated with ASD and OCD. Except for OCD, no evidence for differential effects of parental ages on male versus female offspring was observed. CONCLUSION: This study provides novel evidence for the association between age at parenthood and TD/CT and OCD and for the first time shows in a population-based sample that parental age confers differential risk rates for pediatric-onset psychiatric disorders. These results are consistent with a model of shared and unshared risk architecture for pediatric-onset neuropsychiatric conditions, highlighting unique contributions of maternal and paternal ages.

Maternal Smoking During Pregnancy and Timing of Puberty in Sons and Daughters: A Population-Based Cohort Study.

Because early puberty has been linked to diseases later in life, identification of modifiable causes of early puberty is of interest. We explored the possible associations between maternal smoking during pregnancy and pubertal development in sons and daughters. Between 2012 and 2017, 15,819 children from the Danish National Birth Cohort, born during 2000-2003, provided half-yearly information on puberty from the age of 11 years. We estimated adjusted age differences (in months) at attaining various pubertal milestones, including Tanner stages, per 10 daily cigarettes smoked in the first trimester of gestation. In sons, exposure to smoking in utero was associated with earlier genital development (Tanner 2, -1.3 months, 95% confidence interval (CI): -2.5, 0.0; Tanner 5, -3.7 months, 95% CI: -5.3, -2.0), pubic hair development (Tanner 2, -1.8 months, 95% CI: -2.9, -0.6; Tanner 5, -2.9 months, 95% CI: -4.2, -1.7), and voice break (-2.4 months, 95% CI: -3.6, -1.3). In daughters, maternal smoking was associated with earlier breast development (Tanner 2, -3.4 months, 95% CI: -5.3, -1.5; Tanner 5, -4.7 months, 95% CI: -6.5, -2.9), pubic hair development stages 3-5 (Tanner 5, -2.5 months, 95% CI: -4.1, -1.0), and menarche (-3.1 months, 95% CI: -4.0, -2.3). Fetal exposure to tobacco smoke might advance timing of puberty in boys and girls.

Acetaminophen (Paracetamol) Exposure During Pregnancy and Pubertal Development in Boys and Girls From a Nationwide Puberty Cohort.

This study explored the association between exposure to acetaminophen during pregnancy and pubertal development using data from 15,822 boys and girls in the longitudinal Puberty Cohort, nested within the Danish National Birth Cohort. Use of acetaminophen was reported 3 times during pregnancy and 6 months postpartum. In total, 54% of mothers indicated use at least once during pregnancy. Between 2012 and 2017, sons and daughters provided information on a wide range of pubertal milestones-including Tanner stages, axillary hair growth, and age at menarche or voice break and first ejaculation-every 6 months from 11 years of age until full sexual maturation. Data were analyzed using a regression model for interval-censored data, providing adjusted mean monthly differences in age at attaining the pubertal milestones according to intrauterine cumulative (weeks) and trimester-specific acetaminophen exposure. Our results suggested a tendency towards slightly earlier attainment of almost all studied markers of female pubertal development with increasing number of weeks of exposure (i.e., about 1.5-3 months earlier age at pubic hair, axillary hair, and acne development comparing unexposed with those prenatally exposed for more than 12 weeks). Male pubertal development had no strong association with acetaminophen exposure.

Depression, antidepressants, and the risk of non-valvular atrial fibrillation: A nationwide Danish matched cohort study.

BACKGROUND: Depression is associated with an increased risk of a series of cardiovascular diseases and with increased symptom burden in patients with atrial fibrillation. The aim of this study was to determine the association between depression as well as antidepressant treatment and the risk of incident atrial fibrillation. DESIGN: A nationwide register-based study comparing the atrial fibrillation risk in all Danes initiating antidepressant treatment from 2000 to 2013 ( N = 785,254) with that in a 1:5-matched sample from the general population. METHODS: Cox regression was used to estimate adjusted hazard ratios (aHRs) and associated 95% confidence intervals (95% CIs), both after initiation of treatment and in the month before when patients were assumed to have medically untreated depression. RESULTS: Antidepressant treatment was associated with a three-fold higher risk of atrial fibrillation during the first month (aHR = 3.18 (95% CI: 2.98-3.39)). This association gradually attenuated over the following year (aHR = 1.37 (95% CI: 1.31-1.44) 2-6 months after antidepressant therapy initiation, and aHR = 1.11 (95% CI: 1.06-1.16) 6-12 months after). However, the associated atrial fibrillation risk was even higher in the month before starting antidepressant treatment (aHR = 7.65 (95% CI: 7.05-8.30) from 30 to 15 days before, and aHR = 4.29 (95% CI: 3.94-4.67) the last 15 days before). Overall, 0.4% of patients were diagnosed with atrial fibrillation from 30 days before to 30 days after antidepressant treatment. CONCLUSIONS: Antidepressant users had a substantially increased atrial fibrillation risk, particularly before treatment initiation. Whether this mirrors a causal relation between depression and atrial fibrillation may have large consequences for public health and should be discussed.

Apgar score and risk of autism.

Low Apgar score has been associated with higher risk for several neurological and psychiatric disorders, including cerebral palsy and intellectual disability. Studies of the association between Apgar score and autism spectrum disorder (ASD) have been inconsistent. We aimed to investigate (1) the association between low Apgar score at 5 min and risk for ASD, and (2) the modifying effects of gestational age and sex on this association in the largest multinational database of ASD. We included prospective data from 5.5 million individuals and over 33,000 cases of ASD from Norway, Sweden, Denmark and Western Australia who were born between 1984 and 2007. We calculated crude and adjusted risk ratios (RR) with 95% confidence intervals (95% CIs) for the associations between low Apgar score and ASD. All analyses for ASD were repeated for autistic disorder (AD). We used interaction terms and stratified analysis to investigate the effects of sex, gestational age, and birth weight on the association. In fully adjusted models, low Apgar scores (1-3) (RR, 1.42; 95% CI, 1.16-1.74), and intermediate Apgar scores (4-6) (RR, 1.50; 95% CI, 1.36-1.65) were associated with a higher RR of ASD than optimal Apgar score (7-10). The point estimates for low (RR, 1.88; 95% CI, 1.41-2.51) and intermediate Apgar score (RR, 1.54; 95% CI, 1.32-1.81) were larger for AD than for ASD. This study suggests that low Apgar score is associated with higher risk of ASD, and in particular AD. We did not observe any major modifying effects of gestational age and sex, although there seems to be substantial confounding by gestational age and birth weight on the observed association.