Prospective associations of psychosocial adversity in childhood with risk factors for cardiovascular disease in adulthood: the MRC National Survey of Health and Development

BACKGROUND

Studies assessing associations of childhood psychosocial adversity (e.g. sexual abuse, physical neglect, parental death), as opposed to socioeconomic adversity, with cardiovascular disease (CVD) risk factors in adulthood are scarce. We aimed to assess associations of various forms of psychosocial adversity and cumulative adversity in childhood, with multiple CVD risk factors in mid-life.

METHODS

Participants were from the MRC National Survey of Health and Development. Childhood psychosocial risk factors were reported prospectively by parents from 1950-1957, and retrospectively by participants at mean age 43 years in 1989. CVD risk factors were assessed at mean age 60-64 years in 2006-2011. Associations of a summary score of total psychosocial adversity and CVD risk in adulthood were assessed.

RESULTS

There was no consistent evidence that cumulative psychosocial adversity, nor any specific form of psychosocial adversity in childhood, was associated with CVD risk factors in late adulthood. There was some evidence that parental death in the first 15 years was associated with higher SBP (Beta: 0.23, 95% confidence interval: 0.06 to 0.40, P=0.01) and DBP (Beta: 0.15, 95% confidence interval: -0.01 to 0.32, P=0.07).

CONCLUSIONS

We found no evidence that exposure to greater psychosocial adversity, or specific forms of psychosocial adversity during childhood is associated with adult CVD risk factors. Further large population studies are needed to clarify whether parental death is associated with higher systolic and diastolic blood pressure.

Ethnic differences in the clustering and outcomes of health behaviours during pregnancy: results from the Born in Bradford cohort

Background

Pregnancy is a time of optimal motivation for many women to make positive behavioural changes. We aim to describe pregnant women with similar patterns of self-reported health behaviours and examine associations with birth outcomes.

Methods

We examined the clustering of multiple health behaviours during pregnancy in the Born in Bradford cohort, including smoking physical inactivity, vitamin d supplementation and exposure to second-hand smoke. Latent class analysis was used to identify groups of individuals with similar patterns of health behaviours separately for White British (WB) and Pakistani mothers. Multinomial regression was then used to examine the association between group membership and birth outcomes, which included preterm birth and mean birthweight.

Results

For WB mothers, offspring of those in the 'Unhealthiest' group had lower mean birthweight than those in the 'Mostly healthy but inactive' class, although no association was observed for preterm birth. For Pakistani mothers, group membership was not associated with birthweight differences, although the odds of preterm birth was higher in 'Inactive smokers' compared to the 'Mostly healthy but inactive' group.

Conclusions

The use of latent class methods provides important information about the clustering of health behaviours which can be used to target population segments requiring behaviour change interventions considering multiple risk factors. Given the dominant negative association of smoking with the birth outcomes investigated, latent class groupings of other health behaviours may not confer additional risk information for these outcomes.

Adversity in childhood and measures of aging in midlife: Findings from a cohort of british women

Very few studies have assessed whether socioeconomic and psychosocial adversity during childhood are associated with objective measures of aging later in life. We assessed associations of socioeconomic position (SEP) and total psychosocial adversity during childhood, with objectively measured cognitive and physical capability in women during midlife. Adverse childhood experiences were retrospectively reported at mean ages 28-30 years in women from the Avon Longitudinal Study of Parents And Children (N = 2,221). We investigated associations of childhood SEP and total psychosocial adversity, with composite measures of cognitive and physical capability at mean age 51 years. There was evidence that, compared with participants whose fathers had professional occupations, participants whose fathers had managerial/technical, skilled nonmanual, skilled manual, and partly or unskilled manual occupations had, on average, lower physical and cognitive capability. There was a clear trend for increasing magnitudes of association with lowering childhood SEP. There was also evidence that greater total psychosocial adversity in childhood was associated with lower physical capability. Total psychosocial adversity in childhood was not associated with cognitive capability. Lower SEP in childhood is detrimental to cognitive and physical capability in midlife, at least in part, independently of subsequent SEP in adulthood. Greater psychosocial adversity in childhood is associated with poorer physical capability, independently of social disadvantage in childhood. Our findings highlight the need for interventions to both identify and support children experiencing socioeconomic or psychosocial of adversity as early as possible. (PsycINFO Database Record

Different strategies for diagnosing gestational diabetes to improve maternal and infant health

BACKGROUND

Gestational diabetes mellitus (GDM) is carbohydrate intolerance resulting in hyperglycaemia with onset or first recognition during pregnancy. If untreated, perinatal morbidity and mortality may be increased. Accurate diagnosis allows appropriate treatment. Use of different tests and different criteria will influence which women are diagnosed with GDM. This is an update of a review published in 2011 and 2015.

OBJECTIVES

To evaluate and compare different testing strategies for diagnosis of gestational diabetes mellitus to improve maternal and infant health while assessing their impact on healthcare service costs.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, WHO International Clinical Trials Registry Platform (ICTRP) (9 January 2017) and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised trials if they evaluated tests carried out to diagnose GDM. We excluded studies that used a quasi-random model, cluster-randomised or cross-over trials.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included a total of seven small trials, with 1420 women. One trial including 726 women was identified by this update and examined the two step versus one step approach. These trials were assessed as having varying risk of bias, with few outcomes reported. We prespecified six outcomes to be assessed for quality using the GRADE approach for one comparison: 75 g oral glucose tolerance test (OGTT) versus 100 g OGTT; data for only one outcome (diagnosis of gestational diabetes) were available for assessment. One trial compared three different methods of delivering glucose: a candy bar (39 women), a 50 g glucose polymer drink (40 women) and a 50 g glucose monomer drink (43 women). We have included the results reported by this trial as separate comparisons. No trial reported on measures of costs of health services.We examined six main comparisons. 75 g OGTT versus 100 g OGTT (1 trial, 248 women): women who received 75 g OGTT had a higher relative risk of being diagnosed with GDM (risk ratio (RR) 2.55, 95% confidence interval (CI) 0.96 to 6.75; very-low quality evidence). No data were reported for the following additional outcomes prespecified for GRADE assessment: caesarean section, macrosomia > 4.5 kg or however defined in the trial, long-term type 2 diabetes maternal, long-term type 2 diabetes infant and economic costs. Candy bar versus 50 g glucose monomer drink (1 trial, 60 women): more women receiving the candy bar, rather than glucose monomer, preferred the taste of the candy bar (RR 0.60, 95% CI 0.42 to 0.86) and 1-hour glucose was less with the candy bar. There were no differences in the other outcomes reported (maternal side effects). No infant outcomes were reported or any review primary outcomes. 50 g glucose polymer drink versus 50 g glucose monomer drink (3 trials, 239 women): mean difference (MD) in gestation at birth was -0.80 weeks (1 trial, 100 women; 95% CI -1.69 to 0.09). Total side effects were less common with the glucose polymer drink (1 trial, 63 women; RR 0.21, 95% CI 0.07 to 0.59), and no clear difference in taste acceptability was reported (1 trial, 63 women; RR 0.99, 95% CI 0.76 to 1.29). Fewer women reported nausea following the 50 g glucose polymer drink compared with the 50 g glucose monomer drink (1 trial, 66 women; RR 0.29, 95% CI 0.11 to 0.78). No other measures of maternal morbidity or outcomes for the infant were reported. 50 g glucose food versus 50 g glucose drink (1 trial, 30 women): women receiving glucose in their food, rather than as a drink, reported fewer side effects (RR 0.08, 95% CI 0.01 to 0.56). No clear difference was noted in the number of women requiring further testing (RR 0.14, 95% CI 0.01 to 2.55). No other measures of maternal morbidity or outcome were reported for the infant or review primary outcomes. 75 g OGTT World Health Organization (WHO) criteria versus 75 g OGTT American Diabetes Association (ADA) criteria (1 trial, 116 women): no clear differences in included outcomes were observed between women who received the 75 g OGTT and were diagnosed using criteria based on WHO (1999) recommendations and women who received the 75 g OGTT and were diagnosed using criteria recommended by the ADA (1979). Outcomes measured included diagnosis of gestational diabetes (RR 1.47, 95% CI 0.66 to 3.25), caesarean section (RR 1.07, 95% CI 0.85 to 1.35), macrosomia defined as > 90th percentile by ultrasound or birthweight equal to or exceeding 4000 g (RR 0.73, 95% CI 0.19 to 2.79), stillbirth (RR 0.49, 95% CI 0.02 to 11.68) and instrumental birth (RR 0.21, 95% CI 0.01 to 3.94). No other secondary outcomes were reported. Two-step approach (50 g oral glucose challenge test followed by selective 100 g OGTT Carpenter and Coustan criteria) versus one-step approach (universal 75 g OGTT ADA criteria) (1 trial, 726 women): women allocated the two-step approach had a lower risk of being diagnosed with GDM at 11 to 14 weeks' gestation compared to women allocated the one-step approach (RR 0.51, 95% CI 0.28 to 0.95). No other primary or secondary outcomes were reported.

AUTHORS' CONCLUSIONS

There is insufficient evidence to suggest which strategy is best for diagnosing GDM. Large randomised trials are required to establish the best strategy for correctly identifying women with GDM.

Association of pre-pregnancy body mass index with offspring metabolic profile: Analyses of 3 European prospective birth cohorts

BACKGROUND

A high proportion of women start pregnancy overweight or obese. According to the developmental overnutrition hypothesis, this could lead offspring to have metabolic disruption throughout their lives and thus perpetuate the obesity epidemic across generations. Concerns about this hypothesis are influencing antenatal care. However, it is unknown whether maternal pregnancy adiposity is associated with long-term risk of adverse metabolic profiles in offspring, and if so, whether this association is causal, via intrauterine mechanisms, or explained by shared familial (genetic, lifestyle, socioeconomic) characteristics. We aimed to determine if associations between maternal body mass index (BMI) and offspring systemic cardio-metabolic profile are causal, via intrauterine mechanisms, or due to shared familial factors.

METHODS AND FINDINGS

We used 1- and 2-stage individual participant data (IPD) meta-analysis, and a negative-control (paternal BMI) to examine the association between maternal pre-pregnancy BMI and offspring serum metabolome from 3 European birth cohorts (offspring age at blood collection: 16, 17, and 31 years). Circulating metabolic traits were quantified by high-throughput nuclear magnetic resonance metabolomics. Results from 1-stage IPD meta-analysis (N = 5327 to 5377 mother-father-offspring trios) showed that increasing maternal and paternal BMI was associated with an adverse cardio-metabolic profile in offspring. We observed strong positive associations with very-low-density lipoprotein (VLDL)-lipoproteins, VLDL-cholesterol (C), VLDL-triglycerides, VLDL-diameter, branched/aromatic amino acids, glycoprotein acetyls, and triglycerides, and strong negative associations with high-density lipoprotein (HDL), HDL-diameter, HDL-C, HDL2-C, and HDL3-C (all P < 0.003). Slightly stronger magnitudes of associations were present for maternal compared with paternal BMI across these associations; however, there was no strong statistical evidence for heterogeneity between them (all bootstrap P > 0.003, equivalent to P > 0.05 after accounting for multiple testing). Results were similar in each individual cohort, and in the 2-stage analysis. Offspring BMI showed similar patterns of cross-sectional association with metabolic profile as for parental pre-pregnancy BMI associations but with greater magnitudes. Adjustment of parental BMI-offspring metabolic traits associations for offspring BMI suggested the parental associations were largely due to the association of parental BMI with offspring BMI. Limitations of this study are that inferences cannot be drawn about the role of circulating maternal fetal fuels (i.e., glucose, lipids, fatty acids, and amino acids) on later offspring metabolic profile. In addition, BMI may not reflect potential effects of maternal pregnancy fat distribution.

CONCLUSION

Our findings suggest that maternal BMI-offspring metabolome associations are likely to be largely due to shared genetic or familial lifestyle confounding rather than to intrauterine mechanisms.

Infant adiposity following a randomised controlled trial of a behavioural intervention in obese pregnancy

OBJECTIVES

Randomised controlled trials are required to address causality in the reported associations between maternal influences and offspring adiposity. The aim of this study was to determine whether an antenatal lifestyle intervention, associated with improvements in maternal diet and reduced gestational weight gain (GWG) in obese pregnant women leads to a reduction in infant adiposity and sustained improvements in maternal lifestyle behaviours at 6 months postpartum.

SUBJECTS AND METHODS

We conducted a planned postnatal follow-up of a randomised controlled trial (UK Pregnancies Better Eating and Activity Trial (UPBEAT)) of a complex behavioural intervention targeting maternal diet (glycaemic load (GL) and saturated fat intake) and physical activity in 1555 obese pregnant women. The main outcome measure was infant adiposity, assessed by subscapular and triceps skinfold thicknesses. Maternal diet and physical activity, indices of the familial lifestyle environment, were assessed by questionnaire.

RESULTS

A total of 698 (45.9%) infants (342 intervention and 356 standard antenatal care) were followed up at a mean age of 5.92 months. There was no difference in triceps skinfold thickness z-scores between the intervention vs standard care arms (difference -0.14 s.d., 95% confidence interval -0.38 to 0.10, P=0.246), but subscapular skinfold thickness z-score was 0.26 s.d. (-0.49 to -0.02; P=0.03) lower in the intervention arm. Maternal dietary GL (-35.34; -48.0 to -22.67; P<0.001) and saturated fat intake (-1.93% energy; -2.64 to -1.22; P<0.001) were reduced in the intervention arm at 6 months postpartum. Causal mediation analysis suggested that lower infant subscapular skinfold thickness was partially mediated by changes in antenatal maternal diet and GWG rather than postnatal diet.

CONCLUSIONS

This study provides evidence from follow-up of a randomised controlled trial that a maternal behavioural intervention in obese pregnant women has the potential to reduce infant adiposity and to produce a sustained improvement in maternal diet at 6 months postpartum.

Treatments for gestational diabetes: a systematic review and meta-analysis

OBJECTIVE

To investigate the effectiveness of different treatments for gestational diabetes mellitus (GDM).

DESIGN

Systematic review, meta-analysis and network meta-analysis.

METHODS

Data sources were searched up to July 2016 and included MEDLINE and Embase. Randomised trials comparing treatments for GDM (packages of care (dietary and lifestyle interventions with pharmacological treatments as required), insulin, metformin, glibenclamide (glyburide)) were selected by two authors and double checked for accuracy. Outcomes included large for gestational age, shoulder dystocia, neonatal hypoglycaemia, caesarean section and pre-eclampsia. We pooled data using random-effects meta-analyses and used Bayesian network meta-analysis to compare pharmacological treatments (ie, including treatments not directly compared within a trial).

RESULTS

Forty-two trials were included, the reporting of which was generally poor with unclear or high risk of bias. Packages of care varied in their composition and reduced the risk of most adverse perinatal outcomes compared with routine care (eg, large for gestational age: relative risk0.58 (95% CI 0.49 to 0.68; I2=0%; trials 8; participants 3462). Network meta-analyses suggest that metformin had the highest probability of being the most effective treatment in reducing the risk of most outcomes compared with insulin or glibenclamide.

CONCLUSIONS

Evidence shows that packages of care are effective in reducing the risk of most adverse perinatal outcomes. However, trials often include few women, are poorly reported with unclear or high risk of bias and report few outcomes. The contribution of each treatment within the packages of care remains unclear. Large well-designed and well-conducted trials are urgently needed.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42013004608.

Variants in the fetal genome near FLT1 are associated with risk of preeclampsia

Preeclampsia, which affects approximately 5% of pregnancies, is a leading cause of maternal and perinatal death. The causes of preeclampsia remain unclear, but there is evidence for inherited susceptibility. Genome-wide association studies (GWAS) have not identified maternal sequence variants of genome-wide significance that replicate in independent data sets. We report the first GWAS of offspring from preeclamptic pregnancies and discovery of the first genome-wide significant susceptibility locus (rs4769613; P = 5.4 × 10^-11) in 4,380 cases and 310,238 controls. This locus is near the FLT1 gene encoding Fms-like tyrosine kinase 1, providing biological support, as a placental isoform of this protein (sFlt-1) is implicated in the pathology of preeclampsia. The association was strongest in offspring from pregnancies in which preeclampsia developed during late gestation and offspring birth weights exceeded the tenth centile. An additional nearby variant, rs12050029, associated with preeclampsia independently of rs4769613. The newly discovered locus may enhance understanding of the pathophysiology of preeclampsia and its subtypes.

Genomic analyses identify hundreds of variants associated with age at menarche and support a role for puberty timing in cancer risk

The timing of puberty is a highly polygenic childhood trait that is epidemiologically associated with various adult diseases. Using 1000 Genomes Project-imputed genotype data in up to ∼370,000 women, we identify 389 independent signals (P < 5 × 10-8) for age at menarche, a milestone in female pubertal development. In Icelandic data, these signals explain ∼7.4% of the population variance in age at menarche, corresponding to ∼25% of the estimated heritability. We implicate ∼250 genes via coding variation or associated expression, demonstrating significant enrichment in neural tissues. Rare variants near the imprinted genes MKRN3 and DLK1 were identified, exhibiting large effects when paternally inherited. Mendelian randomization analyses suggest causal inverse associations, independent of body mass index (BMI), between puberty timing and risks for breast and endometrial cancers in women and prostate cancer in men. In aggregate, our findings highlight the complexity of the genetic regulation of puberty timing and support causal links with cancer susceptibility.

Estimating the causal influence of body mass index on risk of Parkinson disease: A Mendelian randomisation study

BACKGROUND

Both positive and negative associations between higher body mass index (BMI) and Parkinson disease (PD) have been reported in observational studies, but it has been difficult to establish causality because of the possibility of residual confounding or reverse causation. To our knowledge, Mendelian randomisation (MR)-the use of genetic instrumental variables (IVs) to explore causal effects-has not previously been used to test the effect of BMI on PD.

METHODS AND FINDINGS

Two-sample MR was undertaken using genome-wide association (GWA) study data. The associations between the genetic instruments and BMI were obtained from the GIANT consortium and consisted of the per-allele difference in mean BMI for 77 independent variants that reached genome-wide significance. The per-allele difference in log-odds of PD for each of these variants was estimated from a recent meta-analysis, which included 13,708 cases of PD and 95,282 controls. The inverse-variance weighted method was used to estimate a pooled odds ratio (OR) for the effect of a 5-kg/m2 higher BMI on PD. Evidence of directional pleiotropy averaged across all variants was sought using MR-Egger regression. Frailty simulations were used to assess whether causal associations were affected by mortality selection. A combined genetic IV expected to confer a lifetime exposure of 5-kg/m2 higher BMI was associated with a lower risk of PD (OR 0.82, 95% CI 0.69-0.98). MR-Egger regression gave similar results, suggesting that directional pleiotropy was unlikely to be biasing the result (intercept 0.002; p = 0.654). However, the apparent protective influence of higher BMI could be at least partially induced by survival bias in the PD GWA study, as demonstrated by frailty simulations. Other important limitations of this application of MR include the inability to analyse non-linear associations, to undertake subgroup analyses, and to gain mechanistic insights.

CONCLUSIONS

In this large study using two-sample MR, we found that variants known to influence BMI had effects on PD in a manner consistent with higher BMI leading to lower risk of PD. The mechanism underlying this apparent protective effect warrants further study.

Causal Associations of Adiposity and Body Fat Distribution With Coronary Heart Disease, Stroke Subtypes, and Type 2 Diabetes Mellitus: A Mendelian Randomization Analysis

BACKGROUND

The implications of different adiposity measures on cardiovascular disease etiology remain unclear. In this article, we quantify and contrast causal associations of central adiposity (waist-to-hip ratio adjusted for body mass index [WHRadjBMI]) and general adiposity (body mass index [BMI]) with cardiometabolic disease.

METHODS

Ninety-seven independent single-nucleotide polymorphisms for BMI and 49 single-nucleotide polymorphisms for WHRadjBMI were used to conduct Mendelian randomization analyses in 14 prospective studies supplemented with coronary heart disease (CHD) data from CARDIoGRAMplusC4D (Coronary Artery Disease Genome-wide Replication and Meta-analysis [CARDIoGRAM] plus The Coronary Artery Disease [C4D] Genetics; combined total 66 842 cases), stroke from METASTROKE (12 389 ischemic stroke cases), type 2 diabetes mellitus from DIAGRAM (Diabetes Genetics Replication and Meta-analysis; 34 840 cases), and lipids from GLGC (Global Lipids Genetic Consortium; 213 500 participants) consortia. Primary outcomes were CHD, type 2 diabetes mellitus, and major stroke subtypes; secondary analyses included 18 cardiometabolic traits.

RESULTS

Each one standard deviation (SD) higher WHRadjBMI (1 SD≈0.08 U) associated with a 48% excess risk of CHD (odds ratio [OR] for CHD, 1.48; 95% confidence interval [CI], 1.28-1.71), similar to findings for BMI (1 SD≈4.6 kg/m²; OR for CHD, 1.36; 95% CI, 1.22-1.52). Only WHRadjBMI increased risk of ischemic stroke (OR, 1.32; 95% CI, 1.03-1.70). For type 2 diabetes mellitus, both measures had large effects: OR, 1.82 (95% CI, 1.38-2.42) and OR, 1.98 (95% CI, 1.41-2.78) per 1 SD higher WHRadjBMI and BMI, respectively. Both WHRadjBMI and BMI were associated with higher left ventricular hypertrophy, glycemic traits, interleukin 6, and circulating lipids. WHRadjBMI was also associated with higher carotid intima-media thickness (39%; 95% CI, 9%-77% per 1 SD).

CONCLUSIONS

Both general and central adiposity have causal effects on CHD and type 2 diabetes mellitus. Central adiposity may have a stronger effect on stroke risk. Future estimates of the burden of adiposity on health should include measures of central and general adiposity.

Screening for familial hypercholesterolaemia in childhood: Avon Longitudinal Study of Parents and Children (ALSPAC)

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) is an autosomal-dominant disease with frequency of 1/500 to 1/250 that leads to premature coronary heart disease. New approaches to identify FH mutation-carriers early are needed to prevent premature cardiac deaths. In a cross-sectional study of the Avon Longitudinal Study of Parents and Children (ALSPAC), we evaluated the biochemical thresholds for FH screening in childhood, and modelled a two-stage biochemical and sequencing screening strategy for FH detection.

METHODS

From 5083 ALSPAC children with cholesterol measurement at age nine years, FH genetic diagnosis was performed in 1512 individuals, using whole-genome or targeted sequencing of known FH-causing genes. Detection rate (DR) and false-positive rate (FPR) for proposed screening thresholds (total-cholesterol > 1.53, or LDL-C > 1.84 multiples of the median (MoM)) were assessed.

RESULTS

Six of 1512 sequenced individuals had an FH-causing mutation of whom five had LDL-C > 1.84 MoM, giving a verification-bias corrected DR of 62.5% (95% CI: 25-92), with a FPR of 0.2% (95% CI: 0.1-0.4). The DR for the TC cut-point of 1.53 MoM was 25% (95% CI: 3.2-65.1) with a FPR of 0.4% (95% CI: 0.2-0.6). We estimated 13 of an expected 20 FH mutation carriers (and 13 of the 20 parental carriers) could be detected for every 10,000 children screened, with false-positives reliably excluded by addition of a next generation sequencing step in biochemical screen-positive samples.

CONCLUSIONS

Proposed cholesterol thresholds for childhood FH screening were less accurate than previously estimated. A sequential strategy of biochemical screening followed by targeted sequencing of FH genes in screen-positive children may help mitigate the higher than previously estimated FPR and reduce wasted screening of unaffected parents.

Risk factor screening to identify women requiring oral glucose tolerance testing to diagnose gestational diabetes: A systematic review and meta-analysis and analysis of two pregnancy cohorts

BACKGROUND

Easily identifiable risk factors including: obesity and ethnicity at high risk of diabetes are commonly used to indicate which women should be offered the oral glucose tolerance test (OGTT) to diagnose gestational diabetes (GDM). Evidence regarding these risk factors is limited however. We conducted a systematic review (SR) and meta-analysis and individual participant data (IPD) analysis to evaluate the performance of risk factors in identifying women with GDM.

METHODS

We searched MEDLINE, Medline in Process, Embase, Maternity and Infant Care and the Cochrane Central Register of Controlled Trials (CENTRAL) up to August 2016 and conducted additional reference checking. We included observational, cohort, case-control and cross-sectional studies reporting the performance characteristics of risk factors used to identify women at high risk of GDM. We had access to IPD from the Born in Bradford and Atlantic Diabetes in Pregnancy cohorts, all pregnant women in the two cohorts with data on risk factors and OGTT results were included.

RESULTS

Twenty nine published studies with 211,698 women for the SR and a further 14,103 women from two birth cohorts (Born in Bradford and the Atlantic Diabetes in Pregnancy study) for the IPD analysis were included. Six studies assessed the screening performance of guidelines; six examined combinations of risk factors; eight evaluated the number of risk factors and nine examined prediction models or scores. Meta-analysis using data from published studies suggests that irrespective of the method used, risk factors do not identify women with GDM well. Using IPD and combining risk factors to produce the highest sensitivities, results in low specificities (and so higher false positives). Strategies that use the risk factors of age (>25 or >30) and BMI (>25 or 30) perform as well as other strategies with additional risk factors included.

CONCLUSIONS

Risk factor screening methods are poor predictors of which pregnant women will be diagnosed with GDM. A simple approach of offering an OGTT to women 25 years or older and/or with a BMI of 25kg/m2 or more is as good as more complex risk prediction models. Research to identify more accurate (bio)markers is needed. Systematic Review Registration: PROSPERO CRD42013004608.

Are parents' motivations to exercise and intention to engage in regular family-based activity associated with both adult and child physical activity?

BACKGROUND/AIM

To examine the associations between parents' motivation to exercise and intention to engage in family-based activity with their own and their child's physical activity.

METHODS

Cross-sectional data from 1067 parent-child pairs (76.1% mother-child); children were aged 5-6 years. Parents reported their exercise motivation (ie, intrinsic motivation, identified regulation, introjected regulation, external regulation and amotivation) as described in self-determination theory and their intention to engage in family-based activity. Parents' and children's mean minutes of moderate-to-vigorous-intensity physical activity (MVPA) and mean counts per minute were derived from ActiGraph accelerometers worn for 3 to 5 days (including a mixture of weekdays and weekend days). Multivariable linear regression models, adjusted for parent sex, number of children, indices of multiple deprivation and clustering of children in schools were used to examine associations (total of 24 associations tested).

RESULTS

In fully adjusted models, each unit increase in identified regulation was associated with a 6.08 (95% CI 3.27 to 8.89, p<0.001) min-per-day increase in parents' MVPA. Parents' external regulation was associated with children performing 2.93 (95% CI -5.83 to -0.03, p=0.05) fewer minutes of MVPA per day and a 29.3 (95% CI -53.8 to -4.7, p=0.02) accelerometer count-per-minute reduction. There was no evidence of association for the other 21 associations tested.

CONCLUSIONS

Future family-based physical activity interventions may benefit from helping parents identify personal value in exercise while avoiding the use of external control or coercion to motivate behaviour.

Programming of Adiposity in Childhood and Adolescence: Associations With Birth Weight and Cord Blood Adipokines

CONTEXT

Exposure to maternal adiposity during pregnancy is associated with higher offspring birth weight and greater adiposity through childhood and adult life. As birth weight reflects the summation of lean and fat mass, the extent to which fat mass at birth tracks into later life is unknown.

OBJECTIVE

To determine whether fat mass at birth is associated with child and adolescent adiposity.

DESIGN, SETTING, AND PARTICIPANTS

UK birth cohort with markers of neonatal fat mass; cord blood leptin, adiponectin, and birth weight and adiposity outcomes at age 9 (n = 2775) and 17 years (n = 2138).

MAIN OUTCOMES

Offspring body mass index (BMI), waist circumference, dual-energy X-ray absorptiometry-determined fat mass, and obesity at age 9 and 17 years.

RESULTS

Higher cord blood leptin was associated with higher z scores of fat mass [difference in mean per 10 pg/mL: 0.03 standard deviation (SD); 95% confidence interval (CI), 0.00 to 0.06], waist circumference (0.04 SD; 95% CI, 0.00 to 0.07), and BMI (0.04 SD; 95% CI, 0.00 to 0.08) at age 9. However, by age 17 the adjusted results were attenuated to the null. Cord blood adiponectin was not associated with measures of adiposity at age 9. At age 17, cord blood adiponectin was positively associated with fat mass (0.02 SD per 10 μg/mL; 95% CI, 0.02 to 0.03) and waist circumference (0.04 SD per 10 μg/mL; 95% CI, 0.03 to 0.05). Birth weight was positively associated with waist circumference (0.03 SD per 100 g; 95% CI, 0.02 to 0.04) and BMI (0.02 SD per 100 g; 95% CI, 0.00 to 0.03), but not fat mass or odds of obesity. Cord blood leptin and adiponectin were not associated with obesity at either age.

CONCLUSIONS

Increased cord blood leptin and adiponectin, known surrogates of fetal fat mass, were weakly associated with increased fat mass in late childhood and adolescence, respectively.

Using Genetic Variation to Explore the Causal Effect of Maternal Pregnancy Adiposity on Future Offspring Adiposity: A Mendelian Randomisation Study

BACKGROUND

It has been suggested that greater maternal adiposity during pregnancy affects lifelong risk of offspring fatness via intrauterine mechanisms. Our aim was to use Mendelian randomisation (MR) to investigate the causal effect of intrauterine exposure to greater maternal body mass index (BMI) on offspring BMI and fat mass from childhood to early adulthood.

METHODS AND FINDINGS

We used maternal genetic variants as instrumental variables (IVs) to test the causal effect of maternal BMI in pregnancy on offspring fatness (BMI and dual-energy X-ray absorptiometry [DXA] determined fat mass index [FMI]) in a MR approach. This was investigated, with repeat measurements, from ages 7 to 18 in the Avon Longitudinal Study of Parents and Children (ALSPAC; n = 2,521 to 3,720 for different ages). We then sought to replicate findings with results for BMI at age 6 in Generation R (n = 2,337 for replication sample; n = 6,057 for total pooled sample). In confounder-adjusted multivariable regression in ALSPAC, a 1 standard deviation (SD, equivalent of 3.7 kg/m2) increase in maternal BMI was associated with a 0.25 SD (95% CI 0.21-0.29) increase in offspring BMI at age 7, with similar results at later ages and when FMI was used as the outcome. A weighted genetic risk score was generated from 32 genetic variants robustly associated with BMI (minimum F-statistic = 45 in ALSPAC). The MR results using this genetic risk score as an IV in ALSPAC were close to the null at all ages (e.g., 0.04 SD (95% CI -0.21-0.30) at age 7 and 0.03 SD (95% CI -0.26-0.32) at age 18 per SD increase in maternal BMI), which was similar when a 97 variant generic risk score was used in ALSPAC. When findings from age 7 in ALSPAC were meta-analysed with those from age 6 in Generation R, the pooled confounder-adjusted multivariable regression association was 0.22 SD (95% CI 0.19-0.25) per SD increase in maternal BMI and the pooled MR effect (pooling the 97 variant score results from ALSPAC with the 32 variant score results from Generation R) was 0.05 SD (95%CI -0.11-0.21) per SD increase in maternal BMI (p-value for difference between the two results = 0.05). A number of sensitivity analyses exploring violation of the MR results supported our main findings. However, power was limited for some of the sensitivity tests and further studies with relevant data on maternal, offspring, and paternal genotype are required to obtain more precise (and unbiased) causal estimates.

CONCLUSIONS

Our findings provide little evidence to support a strong causal intrauterine effect of incrementally greater maternal BMI resulting in greater offspring adiposity.

Customised and Noncustomised Birth Weight Centiles and Prediction of Stillbirth and Infant Mortality and Morbidity: A Cohort Study of 979,912 Term Singleton Pregnancies in Scotland

BACKGROUND

There is limited evidence to support the use of customised centile charts to identify those at risk of stillbirth and infant death at term. We sought to determine birth weight thresholds at which mortality and morbidity increased and the predictive ability of noncustomised (accounting for gestational age and sex) and partially customised centiles (additionally accounting for maternal height and parity) to identify fetuses at risk.

METHODS

This is a population-based linkage study of 979,912 term singleton pregnancies in Scotland, United Kingdom, between 1992 and 2010. The main exposures were noncustomised and partially customised birth weight centiles. The primary outcomes were infant death, stillbirth, overall mortality (infant and stillbirth), Apgar score <7 at 5 min, and admission to the neonatal unit. Optimal thresholds that predicted outcomes for both non- and partially customised birth weight centiles were calculated. Prediction of mortality between non- and partially customised birth weight centiles was compared using area under the receiver operator characteristic curve (AUROC) and net reclassification index (NRI).

FINDINGS

Birth weight ≤25th centile was associated with higher risk for all mortality and morbidity outcomes. For stillbirth, low Apgar score, and neonatal unit admission, risk also increased from the 85th centile. Similar patterns and magnitude of associations were observed for both non- and partially customised birth weight centiles. Partially customised birth weight centiles did not improve the discrimination of mortality (AUROC 0.61 [95%CI 0.60, 0.62]) compared with noncustomised birth weight centiles (AUROC 0.62 [95%CI 0.60, 0.63]) and slightly underperformed in reclassifying pregnancies to different risk categories for both fatal and non-fatal adverse outcomes (NRI -0.027 [95% CI -0.039, -0.016], p < 0.001). We were unable to fully customise centile charts because we lacked data on maternal weight and ethnicity. Additional analyses in an independent UK cohort (n = 10,515) suggested that lack of data on ethnicity in this population (in which national statistics show 98% are white British) and maternal weight would have misclassified ~15% of the large-for-gestation fetuses.

CONCLUSIONS

At term, birth weight remains strongly associated with the risk of stillbirth and infant death and neonatal morbidity. Partial customisation does not improve prediction performance. Consideration of early term delivery or closer surveillance for those with a predicted birth weight ≤25th or ≥85th centile may reduce adverse outcomes. Replication of the analysis with fully customised centiles accounting for ethnicity is warranted.

Early Antenatal Prediction of Gestational Diabetes in Obese Women: Development of Prediction Tools for Targeted Intervention

All obese women are categorised as being of equally high risk of gestational diabetes (GDM) whereas the majority do not develop the disorder. Lifestyle and pharmacological interventions in unselected obese pregnant women have been unsuccessful in preventing GDM. Our aim was to develop a prediction tool for early identification of obese women at high risk of GDM to facilitate targeted interventions in those most likely to benefit. Clinical and anthropometric data and non-fasting blood samples were obtained at 15+0-18+6 weeks' gestation in 1303 obese pregnant women from UPBEAT, a randomised controlled trial of a behavioural intervention. Twenty one candidate biomarkers associated with insulin resistance, and a targeted nuclear magnetic resonance (NMR) metabolome were measured. Prediction models were constructed using stepwise logistic regression. Twenty six percent of women (n = 337) developed GDM (International Association of Diabetes and Pregnancy Study Groups criteria). A model based on clinical and anthropometric variables (age, previous GDM, family history of type 2 diabetes, systolic blood pressure, sum of skinfold thicknesses, waist:height and neck:thigh ratios) provided an area under the curve of 0.71 (95%CI 0.68-0.74). This increased to 0.77 (95%CI 0.73-0.80) with addition of candidate biomarkers (random glucose, haemoglobin A1c (HbA1c), fructosamine, adiponectin, sex hormone binding globulin, triglycerides), but was not improved by addition of NMR metabolites (0.77; 95%CI 0.74-0.81). Clinically translatable models for GDM prediction including readily measurable variables e.g. mid-arm circumference, age, systolic blood pressure, HbA1c and adiponectin are described. Using a ≥35% risk threshold, all models identified a group of high risk obese women of whom approximately 50% (positive predictive value) later developed GDM, with a negative predictive value of 80%. Tools for early pregnancy identification of obese women at risk of GDM are described which could enable targeted interventions for GDM prevention in women who will benefit the most.

Cord Blood Adipokines and Lipids and Adolescent Nonalcoholic Fatty Liver Disease

CONTEXT

Maternal adiposity in pregnancy is associated with offspring adiposity and metabolic dysfunction postnatally, including greater risk of nonalcoholic fatty liver disease (NAFLD). Recent genetic analyses suggest a causal effect of greater maternal body mass index on offspring birth weight and ponderal index, but the relative roles of the environment in utero or later in life remains unclear.

OBJECTIVE

We sought to determine whether markers of infant adiposity (birth weight, umbilical cord blood leptin, adiponectin, and lipids) were associated with markers of NAFLD in adolescence.

DESIGN, SETTING, AND PARTICIPANTS

This was a UK prospective birth cohort with 17 years of follow-up with liver function tests (aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase) (n = 1037 participants), and ultrasound scan assessed liver fat, volume, and sheer velocity at age 17 (n = 541 participants). Missing covariate data were imputed.

MAIN OUTCOMES

Ultrasound and biochemical measures of NAFLD were measured.

RESULTS

Birth weight, cord blood leptin, and adiponectin were not associated with a diagnosis of NAFLD. In adjusted analyses, 2 of 42 associations attained conventional 5% levels of significance. Birth weight was positively associated with liver volume (1.0% greater per 100 g [95% confidence interval 0.5%-2.0%]). Cord high-density lipoprotein-cholesterol was positively associated with alanine aminotransferase (11.6% higher per 1 mmol/L [95% confidence interval 0.3, 23.4]); however, this association was primarily mediated via offspring adiposity.

CONCLUSIONS

In this extensive analysis, we found little evidence measurements of infant fat mass and birth size were related to adolescent markers of NAFLD. The association between birth weight and adolescent liver volume may indicate the contribution of greater organ size to birth weight and tracking of organ size.

Bone Mineral Density Is Positively Related to Carotid Intima-Media Thickness: Findings From a Population-Based Study in Adolescents and Premenopausal Women

Osteoporosis and cardiovascular disease (CVD) are both common causes of morbidity and mortality. Previous studies, mainly of people older than 60 years, suggest a relationship between these conditions. Our aim was to determine the association between bone characteristics and CVD markers in younger and middle-aged individuals. Women (n = 3366) and their adolescent offspring (n = 4368) from the UK population-based cohort study, Avon Longitudinal Study of Parents and Children (ALSPAC), were investigated. We measured total body (TB) and hip bone mineral density (BMD), TB bone area (BA) and bone mineral content (BMC) by dual-energy X-ray absorptiometry (DXA), and carotid intima-media thickness (cIMT) by high-resolution ultrasound. Arterial distensibility was calculated as the difference between systolic and diastolic arterial diameters. Linear regression determined associations between bone exposures and cIMT (in adolescents) and both cIMT and arterial distensibility (in women), generating partial correlation coefficients. Mean (SD) age of women was 48 (4.2) years, body mass index (BMI) was 26.2 (5.0) kg/m² , and 71% were premenopausal. In confounder-adjusted analyses (age, height, lean mass, fat mass, menopause, smoking, estrogen replacement, calcium/vitamin D supplementation, and education) TB and hip BMD were both positively associated with cIMT (0.071 [0.030, 0.112], p = 0.001; 0.063 [0.025, 0.101], p = 0.001, respectively). Femoral neck BMD and TB BMD, BMC, and BA were positively associated with arterial distensibility. Mean (SD) age of adolescents was 17 (0.4) years, BMI was 23 (4.1) kg/m² , and 44.5% were male. Total hip and TB measurements were positively associated with cIMT, with similar magnitudes of association to those found in their mothers. In contrast to most published findings, we identified weak positive associations between BMD and cIMT in predominantly premenopausal women and their adolescent offspring. We found greater femoral neck BMD and TB DXA measurements to be associated with reduced arterial stiffness. Rather than a relationship with preclinical atherosclerosis, in these relatively young populations, we speculate our associations between BMD, cIMT, and arterial distensibility may reflect a shared relationship between bone and vascular growth and development. © 2016 American Society for Bone and Mineral Research.

Triangulation in aetiological epidemiology

Triangulation is the practice of obtaining more reliable answers to research questions through integrating results from several different approaches, where each approach has different key sources of potential bias that are unrelated to each other. With respect to causal questions in aetiological epidemiology, if the results of different approaches all point to the same conclusion, this strengthens confidence in the finding. This is particularly the case when the key sources of bias of some of the approaches would predict that findings would point in opposite directions if they were due to such biases. Where there are inconsistencies, understanding the key sources of bias of each approach can help to identify what further research is required to address the causal question. The aim of this paper is to illustrate how triangulation might be used to improve causal inference in aetiological epidemiology. We propose a minimum set of criteria for use in triangulation in aetiological epidemiology, summarize the key sources of bias of several approaches and describe how these might be integrated within a triangulation framework. We emphasize the importance of being explicit about the expected direction of bias within each approach, whenever this is possible, and seeking to identify approaches that would be expected to bias the true causal effect in different directions. We also note the importance, when comparing results, of taking account of differences in the duration and timing of exposures. We provide three examples to illustrate these points.

Long-term effects of the Active for Life Year 5 (AFLY5) school-based cluster-randomised controlled trial

OBJECTIVE

To investigate the long-term effectiveness of a school-based intervention to improve physical activity and diet in children.

DESIGN

Cluster-randomised controlled trial.

SETTING

60 primary schools in the southwest of England.

PARTICIPANTS

Primary school children who were aged 8-9 years at recruitment, 9-10 years during the intervention and 10-11 years at the long-term follow-up assessment.

INTERVENTION

Teacher training, provision of lesson and child-parent interactive homework plans and teaching materials.

MAIN OUTCOME MEASURES

Primary outcomes were accelerometer-assessed minutes of moderate to vigorous physical activity (MVPA) per day, accelerometer-assessed minutes of sedentary behaviour per day and reported daily consumption of servings of fruit and vegetables.

RESULTS

60 schools with 2221 eligible children were recruited. As in the previously published assessment immediately after the end of the intervention, none of the three primary outcomes differed between children in schools allocated to the intervention, compared with those in control schools at the end of the long-term follow-up (1 year after the end of the intervention). Differences in secondary outcomes were consistent with those at the immediate follow-up, with no evidence that these had diminished over time. Comparing intervention with control schools, the difference in mean child-reported screen viewing at the weekend was -16.03 min (95% CI -32.82 to 0.73), for servings of snacks per day, the difference was -0.11 (95% CI -0.39 to 0.06), in servings of high-energy drinks per day -0.20 (95% CI -0.39 to -0.01) and in servings of high-fat foods per day -0.12 (95% CI -0.39 to 0.00). None of these reached our predefined level of statistical significance, especially after accounting for multiple testing.

CONCLUSIONS

School-based curriculum interventions alone are unlikely to have a major public health impact on children's diet and physical activity.

TRIAL REGISTRATION NUMBER

ISRCTN50133740, Post-results.

Hypertensive Disorders of Pregnancy and Offspring Cardiac Structure and Function in Adolescence

Background

Fetal exposure to preeclampsia is associated with higher blood pressure and later risk of stroke. We aimed to investigate the associations of maternal preeclampsia, gestational hypertension, and maternal blood pressure change in pregnancy with offspring cardiac structure and function in adolescence.

Methods and Results

Using data from a prospective birth cohort study, we included offspring who underwent echocardiography (mean age, 17.7 years; SD, 0.3; N=1592). We examined whether hypertensive disorders of pregnancy were associated with offspring cardiac structure and systolic/diastolic function using linear regression. Using multilevel linear spline models (measurement occasions within women), we also investigated whether rate of maternal systolic/diastolic blood pressure change during pregnancy (weeks 8–18, 18–30, 30–36, and 36 or more) were associated with offspring outcomes. Main models were typically adjusted for maternal age, offspring age and sex, prepregnancy body mass index, parity, glycosuria/diabetes mellitus, education, and maternal smoking. Exposure to maternal preeclampsia (0.025; 95% CI, 0.008–0.043) and gestational hypertension (0.010; 0.002–0.017) were associated with greater relative wall thickness. Furthermore, preeclampsia was also associated with a smaller left ventricular end‐diastolic volume (−9.0 mL; −15 to −3.1). No associations were found between hypertensive disorders of pregnancy and offspring cardiac function. Positive rate of maternal systolic blood pressure change during weeks 8 to 18 was associated with greater offspring left ventricular end‐diastolic volume, left ventricular mass indexed to height^2.7, and E/A.

Conclusions

Adolescent offspring exposed to maternal preeclampsia had greater relative wall thickness and reduced left ventricular end‐diastolic volume, which could be early signs of concentric remodeling and affect future cardiac function as well as risk of cardiovascular disease.

Genome-wide associations for birth weight and correlations with adult disease

Birth weight (BW) has been shown to be influenced by both fetal and maternal factors and in observational studies is reproducibly associated with future risk of adult metabolic diseases including type 2 diabetes (T2D) and cardiovascular disease. These life-course associations have often been attributed to the impact of an adverse early life environment. Here, we performed a multi-ancestry genome-wide association study (GWAS) meta-analysis of BW in 153,781 individuals, identifying 60 loci where fetal genotype was associated with BW (P < 5 × 10-8). Overall, approximately 15% of variance in BW was captured by assays of fetal genetic variation. Using genetic association alone, we found strong inverse genetic correlations between BW and systolic blood pressure (Rg = -0.22, P = 5.5 × 10-13), T2D (Rg = -0.27, P = 1.1 × 10-6) and coronary artery disease (Rg = -0.30, P = 6.5 × 10-9). In addition, using large -cohort datasets, we demonstrated that genetic factors were the major contributor to the negative covariance between BW and future cardiometabolic risk. Pathway analyses indicated that the protein products of genes within BW-associated regions were enriched for diverse processes including insulin signalling, glucose homeostasis, glycogen biosynthesis and chromatin remodelling. There was also enrichment of associations with BW in known imprinted regions (P = 1.9 × 10-4). We demonstrate that life-course associations between early growth phenotypes and adult cardiometabolic disease are in part the result of shared genetic effects and identify some of the pathways through which these causal genetic effects are mediated.

Placental Size Is Associated Differentially With Postnatal Bone Size and Density

We investigated relationships between placental size and offspring adolescent bone indices using a population-based, mother-offspring cohort. The Avon Longitudinal Study of Parents and Children (ALSPAC) recruited pregnant women from the southwest of England between 1991 and 1993. There were 12,942 singleton babies born at term who survived at least the first 12 months. From these, 8933 placentas were preserved in formaldehyde, with maternal permission for their use in research studies. At the approximate age of 15.5 years, the children underwent a dual-energy X-ray absorptiometry (DXA) scan (measurements taken of the whole body minus head bone area [BA], bone mineral content [BMC], and areal bone mineral density [aBMD]). A peripheral quantitative computed tomography (pQCT) scan (Stratec XCT2000L; Stratec, Pforzheim, Germany) at the 50% tibial site was performed at this visit and at approximately age 17.7 years. In 2010 a sample of 1680 placentas were measured and photographed. To enable comparison of effect size across different variables, predictor and outcome variables were standardized to Z-scores and therefore results may be interpreted as partial correlation coefficients. Complete placental, DXA, and pQCT data were available for 518 children at age 15.5 years. After adjustment for gender, gestational age at birth, and age at time of pQCT, the placental area was positively associated with endosteal circumference (β [95% CI]: 0.21 [0.13, 0.30], p < 0.001), periosteal circumference (β [95% CI]: 0.19 [0.10, 0.27], p < 0.001), and cortical area (β [95% CI]: 0.10 [0.01, 0.18], p = 0.03), and was negatively associated with cortical density (β [95% CI]: -0.11 [-0.20, -0.03], p = 0.01) at age 15.5 years. Similar relationships were observed for placental volume, and after adjustment for additional maternal and offspring covariates. These results suggest that previously observed associations between placental size and offspring bone development persist into older childhood, even during puberty, and that placental size is differentially related to bone size and volumetric density. © 2016 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research (ASBMR).

Relationship between mediation analysis and the structured life course approach

Many questions in life course epidemiology involve mediation and/or interaction because of the long latency period between exposures and outcomes. In this paper, we explore how mediation analysis (based on counterfactual theory and implemented using conventional regression approaches) links with a structured approach to selecting life course hypotheses. Using theory and simulated data, we show how the alternative life course hypotheses assessed in the structured life course approach correspond to different combinations of mediation and interaction parameters. For example, an early life critical period model corresponds to a direct effect of the early life exposure, but no indirect effect via the mediator and no interaction between the early life exposure and the mediator. We also compare these methods using an illustrative real-data example using data on parental occupational social class (early life exposure), own adult occupational social class (mediator) and physical capability (outcome).

Hyperglycaemia and risk of adverse perinatal outcomes: systematic review and meta-analysis

OBJECTIVES

 To assess the association between maternal glucose concentrations and adverse perinatal outcomes in women without gestational or existing diabetes and to determine whether clear thresholds for identifying women at risk of perinatal outcomes can be identified.

DESIGN

 Systematic review and meta-analysis of prospective cohort studies and control arms of randomised trials.

DATA SOURCES

 Databases including Medline and Embase were searched up to October 2014 and combined with individual participant data from two additional birth cohorts.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

 Studies including pregnant women with oral glucose tolerance (OGTT) or challenge (OGCT) test results, with data on at least one adverse perinatal outcome.

APPRAISAL AND DATA EXTRACTION

 Glucose test results were extracted for OGCT (50 g) and OGTT (75 g and 100 g) at fasting and one and two hour post-load timings. Data were extracted on induction of labour; caesarean and instrumental delivery; pregnancy induced hypertension; pre-eclampsia; macrosomia; large for gestational age; preterm birth; birth injury; and neonatal hypoglycaemia. Risk of bias was assessed with a modified version of the critical appraisal skills programme and quality in prognostic studies tools.

RESULTS

 25 reports from 23 published studies and two individual participant data cohorts were included, with up to 207 172 women (numbers varied by the test and outcome analysed in the meta-analyses). Overall most studies were judged as having a low risk of bias. There were positive linear associations with caesarean section, induction of labour, large for gestational age, macrosomia, and shoulder dystocia for all glucose exposures across the distribution of glucose concentrations. There was no clear evidence of a threshold effect. In general, associations were stronger for fasting concentration than for post-load concentration. For example, the odds ratios for large for gestational age per 1 mmol/L increase of fasting and two hour post-load glucose concentrations (after a 75 g OGTT) were 2.15 (95% confidence interval 1.60 to 2.91) and 1.20 (1.13 to 1.28), respectively. Heterogeneity was low between studies in all analyses.

CONCLUSIONS

 This review and meta-analysis identified a large number of studies in various countries. There was a graded linear association between fasting and post-load glucose concentration across the whole glucose distribution and most adverse perinatal outcomes in women without pre-existing or gestational diabetes. The lack of a clear threshold at which risk increases means that decisions regarding thresholds for diagnosing gestational diabetes are somewhat arbitrary. Research should now investigate the clinical and cost-effectiveness of applying different glucose thresholds for diagnosis of gestational diabetes on perinatal and longer term outcomes.

SYSTEMATIC REVIEW REGISTRATION

 PROSPERO CRD42013004608.

Effects of hormonal contraception on systemic metabolism: cross-sectional and longitudinal evidence

Background: Hormonal contraception is commonly used worldwide, but its systemic effects across lipoprotein subclasses, fatty acids, circulating metabolites and cytokines remain poorly understood.

Methods: A comprehensive molecular profile (75 metabolic measures and 37 cytokines) was measured for up to 5841 women (age range 24–49 years) from three population-based cohorts. Women using combined oral contraceptive pills (COCPs) or progestin-only contraceptives (POCs) were compared with those who did not use hormonal contraception. Metabolomics profiles were reassessed for 869 women after 6 years to uncover the metabolic effects of starting, stopping and persistently using hormonal contraception.

Results: The comprehensive molecular profiling allowed multiple new findings on the metabolic associations with the use of COCPs. They were positively associated with lipoprotein subclasses, including all high-density lipoprotein (HDL) subclasses. The associations with fatty acids and amino acids were strong and variable in direction. COCP use was negatively associated with albumin and positively associated with creatinine and inflammatory markers, including glycoprotein acetyls and several growth factors and interleukins. Our findings also confirmed previous results e.g. for increased circulating triglycerides and HDL cholesterol. Starting COCPs caused similar metabolic changes to those observed cross-sectionally: the changes were maintained in consistent users and normalized in those who stopped using. In contrast, POCs were only weakly associated with metabolic and inflammatory markers. Results were consistent across all cohorts and for different COCP preparations and different types of POC delivery.

Conclusions: Use of COCPs causes widespread metabolic and inflammatory effects. However, persistent use does not appear to accumulate the effects over time and the metabolic perturbations are reversed upon discontinuation. POCs have little effect on systemic metabolism and inflammation.

Sensitivity analysis for the effects of multiple unmeasured confounders

PURPOSE

Observational studies are prone to (unmeasured) confounding. Sensitivity analysis of unmeasured confounding typically focuses on a single unmeasured confounder. The purpose of this study was to assess the impact of multiple (possibly weak) unmeasured confounders.

METHODS

Simulation studies were performed based on parameters estimated from the British Women's Heart and Health Study, including 28 measured confounders and assuming no effect of ascorbic acid intake on mortality. In addition, 25, 50, or 100 unmeasured confounders were simulated, with various mutual correlations and correlations with measured confounders.

RESULTS

The correlated unmeasured confounders did not need to be strongly associated with exposure and outcome to substantially bias the exposure-outcome association at interest, provided that there are sufficiently many unmeasured confounders. Correlations between unmeasured confounders, in addition to the strength of their relationship with exposure and outcome, are key drivers of the magnitude of unmeasured confounding and should be considered in sensitivity analyses. However, if the unmeasured confounders are correlated with measured confounders, the bias yielded by unmeasured confounders is partly removed through adjustment for the measured confounders.

CONCLUSIONS

Discussions of the potential impact of unmeasured confounding in observational studies, and sensitivity analyses to examine this, should focus on the potential for the joint effect of multiple unmeasured confounders to bias results.

A structured approach to hypotheses involving continuous exposures over the life course

Background: Epidemiologists are often interested in examining different hypotheses for how exposures measured repeatedly over the life course relate to later-life outcomes. A structured approach for selecting the hypotheses most supported by theory and observed data has been developed for binary exposures. The aim of this paper is to extend this to include continuous exposures and allow for confounding and missing data.

Methods: We studied two examples, the association between: (i) maternal weight during pregnancy and birthweight; and (ii) stressful family events throughout childhood and depression in adolescence. In each example we considered several plausible hypotheses including accumulation, critical periods, sensitive periods, change and effect modification. We used least angle regression to select the hypothesis that explained the most variation in the outcome, demonstrating appropriate methods for adjusting for confounders and dealing with missing data.

Results: The structured approach identified a combination of sensitive periods: pre-pregnancy weight, and gestational weight gain 0-20 weeks and 20-40 weeks, as the best explanation for variation in birthweight after adjusting for maternal height. A sensitive period hypothesis best explained variation in adolescent depression, with the association strengthening with the proximity of stressful family events. For each example, these models have theoretical support at least as strong as any competing hypothesis.

Conclusions: We have extended the structured approach to incorporate continuous exposures, confounding and missing data. This approach can be used in either an exploratory or a confirmatory setting. The interpretation, plausibility and consistency with causal assumptions should all be considered when proposing and choosing life course hypotheses.

International Genome-Wide Association Study Consortium Identifies Novel Loci Associated With Blood Pressure in Children and Adolescents

BACKGROUND

Our aim was to identify genetic variants associated with blood pressure (BP) in childhood and adolescence.

METHODS AND RESULTS

Genome-wide association study data from participating European ancestry cohorts of the Early Genetics and Lifecourse Epidemiology (EAGLE) Consortium was meta-analyzed across 3 epochs; prepuberty (4-7 years), puberty (8-12 years), and postpuberty (13-20 years). Two novel loci were identified as having genome-wide associations with systolic BP across specific age epochs: rs1563894 (ITGA11, located in active H3K27Ac mark and transcription factor chromatin immunoprecipitation and 5'-C-phosphate-G-3' methylation site) during prepuberty (P=2.86×10(-8)) and rs872256 during puberty (P=8.67×10(-9)). Several single-nucleotide polymorphism clusters were also associated with childhood BP at P<5×10(-3). Using a P value threshold of <5×10(-3), we found some overlap in variants across the different age epochs within our study and between several single-nucleotide polymorphisms in any of the 3 epochs and adult BP-related single-nucleotide polymorphisms.

CONCLUSIONS

Our results suggest that genetic determinants of BP act from childhood, develop over the lifecourse, and show some evidence of age-specific effects.

Metabolic Characterization of a Rare Genetic Variation Within APOC3 and Its Lipoprotein Lipase-Independent Effects

BACKGROUND

Plasma triglyceride levels have been implicated in atherosclerosis and coronary heart disease. Apolipoprotein C-III (APOC3) plays a key role in the hydrolysis of triglyceride-rich lipoproteins to remnant particles by lipoprotein lipase (LPL) and their uptake by the liver. A rare variant in APOC3(rs138326449) has been associated with triglyceride, very low-density lipoprotein, and high-density lipoprotein levels, as well as risk of coronary heart disease. We aimed to characterize the impact of this locus across a broad set of mainly lipids-focused metabolic measures.

METHODS AND RESULTS

A high-throughput serum nuclear magnetic resonance metabolomics platform was used to quantify 225 metabolic measures in 13 285 participants from 2 European population cohorts. We analyzed the effect of the APOC3 variant on the metabolic measures and used the common LPL(rs12678919) polymorphism to test for LPL-independent effects. Eighty-one metabolic measures showed evidence of association with APOC3(rs138326449). In addition to previously reported triglyceride and high-density lipoprotein associations, the variant was also associated with very low-density lipoprotein and high-density lipoprotein composition measures, other cholesterol measures, and fatty acids. Comparison of the APOC3 and LPL associations revealed that APOC3 association results for medium and very large very low-density lipoprotein composition are unlikely to be solely predictable by the action of APOC3 through LPL.

CONCLUSIONS

We characterized the effects of the rare APOC3(rs138326449) loss of function mutation in lipoprotein metabolism, as well as the effects of LPL(rs12678919). Our results improve our understanding of the role of APOC3 in triglyceride metabolism, its LPL independent action, and the complex and correlated nature of human metabolites.

Active for Life Year 5: a cluster randomised controlled trial of a primary school-based intervention to increase levels of physical activity, decrease sedentary behaviour and improve diet

Background

Previous studies of the effect of school-based interventions to improve healthy behaviours have had important limitations.

Objective

To investigate the effectiveness of a school-based intervention to increase physical activity, reduce sedentary behaviour and increase fruit and vegetable consumption.

Design

Cluster randomised controlled trial.

Setting

Sixty English primary schools.

Participants

Children in year 4 (aged 8–9 years) at recruitment, year 5 (aged 9–10 years) during the intervention and immediate follow-up and year 6 (aged 10–11 years) during 1 year of follow-up.

Intervention

Active for Life Year 5 (AFLY5) included teacher training, lesson plans, materials for 16 lessons, parent-interactive homework and written materials for school newsletters and parents.

Main outcome measures

Primary outcome measures included accelerometer-assessed levels of physical activity and sedentary behaviour, and child-reported consumption of fruit and vegetables. Secondary outcome measures included child-reported screen viewing; consumption of snacks, high-fat food and high-energy drinks; body mass index; and waist circumference.

Results

We recruited 60 schools (2221 children). At the immediate follow-up, no difference was found between children in intervention and control schools for any of the three primary outcomes. The intervention was effective on three of the nine secondary outcomes; children in intervention schools reported spending less time screen viewing at weekends [–21 minutes per day, 95% confidence interval (CI) –37 to –4 minutes per day], eating fewer servings of snacks per day (–0.22, 95% CI –0.38 to –0.05 servings of snacks per day) and drinking fewer servings of high-energy drinks per day (–0.26, 95% CI –0.43 to –0.10 servings of high-energy drinks per day) than the children in control schools. The results remained consistent 1 year later. The intervention increased children’s perception of maternal efforts to limit the time they spent screen viewing and children’s knowledge about healthy physical activity and fruit and vegetable consumption, with these two mediators explaining approximately one-quarter of the effect of the intervention on screen viewing. The intervention did not affect other mediators. The cost of implementing the intervention from a provider perspective was approximately £18 per child. Process evaluation showed that AFLY5 was implemented with a high degree of fidelity. Teachers supported the aims of AFLY5, but their views of the programme itself were mixed.

Limitations

Responses to parental questionnaires for the economic evaluation were low and we struggled to engage all teachers for the process evaluation. Although the participating schools included a range of levels of socioeconomic deprivation, class sizes and rural and urban settings, we cannot assume that results generalise to all primary schools.

Conclusions

AFLY5 is not effective at increasing levels of physical activity, reducing sedentary behaviour and increasing fruit and vegetable consumption in primary school children, but may be effective in reducing time spent screen viewing at weekends and the consumption of snacks and high-energy drinks.

Future work

Our findings suggest that school-based interventions are unlikely to have a major impact on promoting healthy levels of physical activity and healthy diets in primary school children. We would recommend trials of the effect and cost-effectiveness of more intensive family and community interventions.

Trial registration

Current Controlled Trials ISRCTN50133740.

Funding

This project was funded by the National Institute for Health Research Public Health Research programme and will be published in full inPublic Health Research; Vol. 4, No. 7. See the NIHR Journals Library website for further project information.

Role of Adiponectin in Coronary Heart Disease Risk: A Mendelian Randomization Study

Supplemental Digital Content is available in the text.

Rationale:

Hypoadiponectinemia correlates with several coronary heart disease (CHD) risk factors. However, it is unknown whether adiponectin is causally implicated in CHD pathogenesis.

Objective:

We aimed to investigate the causal effect of adiponectin on CHD risk.

Methods and Results:

We undertook a Mendelian randomization study using data from genome-wide association studies consortia. We used the ADIPOGen consortium to identify genetic variants that could be used as instrumental variables for the effect of adiponectin. Data on the association of these genetic variants with CHD risk were obtained from CARDIoGRAM (22 233 CHD cases and 64 762 controls of European ancestry) and from CARDIoGRAMplusC4D Metabochip (63 746 cases and 130 681 controls; ≈ 91% of European ancestry) consortia. Data on the association of genetic variants with adiponectin levels and with CHD were combined to estimate the influence of blood adiponectin on CHD risk. In the conservative approach (restricted to using variants within the adiponectin gene as instrumental variables), each 1 U increase in log blood adiponectin concentration was associated with an odds ratio for CHD of 0.83 (95% confidence interval, 0.68–1.01) in CARDIoGRAM and 0.97 (95% confidence interval, 0.84–1.12) in CARDIoGRAMplusC4D Metabochip. Findings from the liberal approach (including variants in any locus across the genome) indicated a protective effect of adiponectin that was attenuated to the null after adjustment for known CHD predictors.

Conclusions:

Overall, our findings do not support a causal role of adiponectin levels in CHD pathogenesis.

Development and evaluation of an intervention for the prevention of childhood obesity in a multiethnic population: the Born in Bradford applied research programme

Background

There is an absence of evidence about interventions to prevent or treat obesity in early childhood and in South Asian populations, in whom risk is higher.

Objectives

To study patterns and the aetiology of childhood obesity in a multiethnic population and develop a prevention intervention.

Design

A cohort of pregnant women and their infants was recruited. Measures to compare growth and identify targets for obesity prevention, sensitive to ethnic differences, were collected. A feasibility randomised controlled trial (RCT) was undertaken.

Setting

Bradford, UK.

Participants

A total of 1735 mothers, 933 of whom were of South Asian origin.

Intervention

A feasibility trial of a group-based intervention aimed at overweight women, delivered ante- and postnatally, targeting key modifiable lifestyle behaviours to reduce infant obesity.

Main outcome measures

The feasibility and acceptability of the pilot intervention.

Data sources

Routine NHS data and additional bespoke research data.

Review methods

A systematic review of diet and physical activity interventions to prevent or treat obesity in South Asian children and adults.

Results

Routine measures of growth were accurate. The prevalence of risk factors differed between mothers of white British ethnicity and mothers of Pakistani ethnicity and weight and length growth trajectories differed between Pakistani infants and white British infants. Prediction equations for risk of childhood obesity were developed. An evidence-based intervention was evaluated in a pilot RCT and was found to be feasible and acceptable.

Limitations

This was a single-centre observational study and a pilot evaluation.

Conclusions

The programme has been successful in recruiting a unique multiethnic childhood obesity cohort, which has provided new evidence about modifiable risk factors and biethnic growth trajectories. A novel group-based behavioural change intervention has been developed and successfully piloted. A multisite cluster RCT is required to evaluate effectiveness.

Trial registration

Current Controlled Trials ISRCTN56735429.

Funding

The National Institute for Health Research Programme Grants for Applied Research programme.

DNA Methylation and BMI: Investigating Identified Methylation Sites at HIF3A in a Causal Framework

Multiple differentially methylated sites and regions associated with adiposity have now been identified in large-scale cross-sectional studies. We tested for replication of associations between previously identified CpG sites at HIF3A and adiposity in ∼1,000 mother-offspring pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC). Availability of methylation and adiposity measures at multiple time points, as well as genetic data, allowed us to assess the temporal associations between adiposity and methylation and to make inferences regarding causality and directionality. Overall, our results were discordant with those expected if HIF3A methylation has a causal effect on BMI and provided more evidence for causality in the reverse direction (i.e., an effect of BMI on HIF3A methylation). These results are based on robust evidence from longitudinal analyses and were also partially supported by Mendelian randomization analysis, although this latter analysis was underpowered to detect a causal effect of BMI on HIF3A methylation. Our results also highlight an apparent long-lasting intergenerational influence of maternal BMI on offspring methylation at this locus, which may confound associations between own adiposity and HIF3A methylation. Further work is required to replicate and uncover the mechanisms underlying the direct and intergenerational effect of adiposity on DNA methylation.

Plasma urate concentration and risk of coronary heart disease: a Mendelian randomisation analysis

BACKGROUND

Increased circulating plasma urate concentration is associated with an increased risk of coronary heart disease, but the extent of any causative effect of urate on risk of coronary heart disease is still unclear. In this study, we aimed to clarify any causal role of urate on coronary heart disease risk using Mendelian randomisation analysis.

METHODS

We first did a fixed-effects meta-analysis of the observational association of plasma urate and risk of coronary heart disease. We then used a conventional Mendelian randomisation approach to investigate the causal relevance using a genetic instrument based on 31 urate-associated single nucleotide polymorphisms (SNPs). To account for potential pleiotropic associations of certain SNPs with risk factors other than urate, we additionally did both a multivariable Mendelian randomisation analysis, in which the genetic associations of SNPs with systolic and diastolic blood pressure, HDL cholesterol, and triglycerides were included as covariates, and an Egger Mendelian randomisation (MR-Egger) analysis to estimate a causal effect accounting for unmeasured pleiotropy.

FINDINGS

In the meta-analysis of 17 prospective observational studies (166 486 individuals; 9784 coronary heart disease events) a 1 SD higher urate concentration was associated with an odds ratio (OR) for coronary heart disease of 1·07 (95% CI 1·04-1·10). The corresponding OR estimates from the conventional, multivariable adjusted, and Egger Mendelian randomisation analysis (58 studies; 198 598 individuals; 65 877 events) were 1·18 (95% CI 1·08-1·29), 1·10 (1·00-1·22), and 1·05 (0·92-1·20), respectively, per 1 SD increment in plasma urate.

INTERPRETATION

Conventional and multivariate Mendelian randomisation analysis implicates a causal role for urate in the development of coronary heart disease, but these estimates might be inflated by hidden pleiotropy. Egger Mendelian randomisation analysis, which accounts for pleiotropy but has less statistical power, suggests there might be no causal effect. These results might help investigators to determine the priority of trials of urate lowering for the prevention of coronary heart disease compared with other potential interventions.

FUNDING

UK National Institute for Health Research, British Heart Foundation, and UK Medical Research Council.

Association of maternal diabetes/glycosuria and pre-pregnancy body mass index with offspring indicators of non-alcoholic fatty liver disease

BACKGROUND

Little is known about early life determinants of non-alcoholic fatty liver disease (NAFLD). We examined associations of maternal pregnancy diabetes/glycosuria and pre-pregnancy body mass index (BMI) with offspring markers of NAFLD and liver pathology and examined mediation by birthweight and concurrent offspring adiposity.

METHODS

We used data from a UK prospective pregnancy cohort. Offspring underwent abdominal ultrasonography (USS) at mean age 17.8 years. Outcomes included USS-assessed fatty liver, estimated liver volume and shear velocity, a variant of elastography (a marker of liver fibrosis) (N = 1 215) and blood-based markers of liver pathology [alanine amino transferase, aspartate amino transferase, gamma- glutamyltransferase and haptoglobin] (N = 2 359).

RESULTS

2.1 % (N = 25) of participants had USS-assessed fatty liver [maternal diabetes/glycosuria (N = 7) and no diabetes/glycosuria (N = 18)]. Maternal diabetes/glycosuria was associated with greater odds of offspring USS fatty liver in confounder adjusted models [adjusted odds ratio (aOR) 6.74 (95 % confidence interval (CI) 2.47, 18.40)] and higher shear velocity [adjusted ratio of geometric mean (aRGM):1.10 (95 % CI 1.05, 1.15)]. These associations were not mediated by offspring birthweight or concurrent adiposity. Maternal diabetes/glycosuria was not associated with liver volume or blood-based outcomes. Greater maternal pre-pregnancy BMI was associated with greater odds of offspring USS fatty liver [aOR 2.72 (95 % CI: 1.20, 6.15)], higher liver volume [aRGM 1.03 (95 % CI 1.00, 1.07)] and shear velocity [aRGM1.03 (95 % CI: 1.01, 1.06)] in confounder adjusted models. These associations were largely mediated by offspring adiposity. Maternal pre-pregnancy BMI was not consistently associated with blood-based outcomes.

CONCLUSIONS

Results suggest that maternal pregnancy diabetes/glycosuria is associated with offspring NAFLD through mechanisms other than offspring's own adiposity.

Genetic Evidence for Causal Relationships Between Maternal Obesity-Related Traits and Birth Weight

IMPORTANCE

Neonates born to overweight or obese women are larger and at higher risk of birth complications. Many maternal obesity-related traits are observationally associated with birth weight, but the causal nature of these associations is uncertain.

OBJECTIVE

To test for genetic evidence of causal associations of maternal body mass index (BMI) and related traits with birth weight.

DESIGN, SETTING, AND PARTICIPANTS

Mendelian randomization to test whether maternal BMI and obesity-related traits are potentially causally related to offspring birth weight. Data from 30,487 women in 18 studies were analyzed. Participants were of European ancestry from population- or community-based studies in Europe, North America, or Australia and were part of the Early Growth Genetics Consortium. Live, term, singleton offspring born between 1929 and 2013 were included.

EXPOSURES

Genetic scores for BMI, fasting glucose level, type 2 diabetes, systolic blood pressure (SBP), triglyceride level, high-density lipoprotein cholesterol (HDL-C) level, vitamin D status, and adiponectin level.

MAIN OUTCOME AND MEASURE

Offspring birth weight from 18 studies.

RESULTS

Among the 30,487 newborns the mean birth weight in the various cohorts ranged from 3325 g to 3679 g. The maternal genetic score for BMI was associated with a 2-g (95% CI, 0 to 3 g) higher offspring birth weight per maternal BMI-raising allele (P = .008). The maternal genetic scores for fasting glucose and SBP were also associated with birth weight with effect sizes of 8 g (95% CI, 6 to 10 g) per glucose-raising allele (P = 7 × 10(-14)) and -4 g (95% CI, -6 to -2 g) per SBP-raising allele (P = 1×10(-5)), respectively. A 1-SD ( ≈ 4 points) genetically higher maternal BMI was associated with a 55-g higher offspring birth weight (95% CI, 17 to 93 g). A 1-SD ( ≈ 7.2 mg/dL) genetically higher maternal fasting glucose concentration was associated with 114-g higher offspring birth weight (95% CI, 80 to 147 g). However, a 1-SD ( ≈ 10 mm Hg) genetically higher maternal SBP was associated with a 208-g lower offspring birth weight (95% CI, -394 to -21 g). For BMI and fasting glucose, genetic associations were consistent with the observational associations, but for systolic blood pressure, the genetic and observational associations were in opposite directions.

CONCLUSIONS AND RELEVANCE

In this mendelian randomization study, genetically elevated maternal BMI and blood glucose levels were potentially causally associated with higher offspring birth weight, whereas genetically elevated maternal SBP was potentially causally related to lower birth weight. If replicated, these findings may have implications for counseling and managing pregnancies to avoid adverse weight-related birth outcomes.

The Active for Life Year 5 (AFLY5) school-based cluster randomised controlled trial: effect on potential mediators

BACKGROUND

Active for life year 5 (AFLY5) is a school-based intervention, based on social cognitive theory, which aims to promote healthy levels of physical activity and healthy eating by improving a child's self-efficacy to make healthy choices, their knowledge of how to make such choices and prompting parents to support their children to make healthy choices. Previously published results showed no effect on the three primary outcomes and beneficial effects on three of nine secondary outcomes (time spent screen-viewing at weekends, consumption of snacks and of high energy drinks). This paper aims to determine the effect of the intervention on potential mediators.

METHODS

We conducted a cluster RCT of a school-based intervention, with allocation concealed by use of a remote system. The study was undertaken in the South West of England between 2011 and 2013. Participants were school children who were age 8-9 years at baseline assessment and 9-10 years during the intervention. Potential mediators were assessed at the end of the intervention. The intervention consisted of teacher training, provision of all materials required for lessons and homeworks and written materials for school newsletters and parents. The ten potential mediators were child-reported self-efficacy for physical activity and fruit and vegetable consumption, perceived parental logistic support and modelling for their child's physical activity, parental efforts to limit their child's sedentary behaviour and modelling of healthy fruit and vegetable consumption, together with a knowledge assessment.

RESULTS

We successfully recruited 60 schools with over 2,221 children; valid data for the 10 mediators were available for 87 % to 96 % of participants. Three of the ten potential mediators were greater in the intervention, compared with the control group: fruit and vegetable self-efficacy 2.2 units (95 % CI: 0.7 to 3.8), assessed on a scale 26 to 130; child-reported maternal limitation of sedentary behaviour 0.5 (0.1 to 0.8), scale 4 to 16; and knowledge 0.5 (0.2, 0.7) scale 0 to 9. Reported maternal limitation of sedentary behaviour and the child's knowledge explained 23 % of the effect of the intervention on reducing time spent on sedentary behaviour at the weekend. There was no effect on other mediators.

CONCLUSIONS

Our findings suggest that the effect of the AFLY5 intervention on reducing screen-viewing at weekends was partially mediated by an effect on mothers limiting their child's time spent sedentary and on increasing the child's knowledge about healthy behaviour. However, overall our findings suggest that theory driven interventions, like AFLY5, can fail to influence most potential mediators and this may explain the failure of the intervention to improve most primary and secondary outcomes.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN50133740. Registered 17/03/2011.

Genome-wide association study identifies common and low-frequency variants at the AMH gene locus that strongly predict serum AMH levels in males

Anti-Müllerian hormone (AMH) is an essential messenger of sexual differentiation in the foetus and is an emerging biomarker of postnatal reproductive function in females. Due to a paucity of adequately sized studies, the genetic determinants of circulating AMH levels are poorly characterized. In samples from 2815 adolescents aged 15 from the ALSPAC study, we performed the first genome-wide association study of serum AMH levels across a set of ∼9 m '1000 Genomes Reference Panel' imputed genetic variants. Genetic variants at the AMH protein-coding gene showed considerable allelic heterogeneity, with both common variants [rs4807216 (P(Male) = 2 × 10(-49), Beta: ∼0.9 SDs per allele), rs8112524 (P(Male) = 3 × 10(-8), Beta: ∼0.25)] and low-frequency variants [rs2385821 (P(Male) = 6 × 10(-31), Beta: ∼1.2, frequency 3.6%)] independently associated with apparently large effect sizes in males, but not females. For all three SNPs, we highlight mechanistic links to AMH gene function and demonstrate highly significant sex interactions (P(Het) 0.0003-6.3 × 10(-12)), culminating in contrasting estimates of trait variance explained (24.5% in males versus 0.8% in females). Using these SNPs as a genetic proxy for AMH levels, we found no evidence in additional datasets to support a biological role for AMH in complex traits and diseases in men.

Genetic markers as instrumental variables

The use of genetic markers as instrumental variables (IV) is receiving increasing attention from economists, statisticians, epidemiologists and social scientists. Although IV is commonly used in economics, the appropriate conditions for the use of genetic variants as instruments have not been well defined. The increasing availability of biomedical data, however, makes understanding of these conditions crucial to the successful use of genotypes as instruments. We combine the econometric IV literature with that from genetic epidemiology, and discuss the biological conditions and IV assumptions within the statistical potential outcomes framework. We review this in the context of two illustrative applications.

Hypertensive disorders of pregnancy, respiratory outcomes and atopy in childhood

Few epidemiological studies have investigated the role of hypertensive disorders of pregnancy in the aetiology of childhood respiratory and atopic outcomes.In the Avon Longitudinal Study of Parents and Children we examined associations of maternal gestational hypertension, hypertension before pregnancy and pre-eclampsia with wheezing at 18 months, wheezing and asthma at 7 years and lung function at 8-9 years, after controlling for potential confounders (n=5322-8734, depending on outcome).Gestational hypertension was not associated with any of the outcomes. There was weak evidence for a positive association between pre-eclampsia and early wheezing (adjusted OR 1.31, 95% CI 0.94-1.82, compared to normotensive pregnancies) and for negative associations between pre-eclampsia and forced expiratory volume in 1 s (adjusted mean difference in sd score -0.14, 95% CI -0.33-0.06) and maximal mid-expiratory flow (-0.15, 95% CI -0.34-0.04). Hypertension before pregnancy was positively associated with wheezing (OR 1.63, 95% CI 1.16-2.31) and asthma (OR 1.34, 95% CI 1.00-1.79).Gestational hypertension is unlikely to be a risk factor for childhood respiratory disorders; hypertension before pregnancy may be a risk factor for childhood wheezing and asthma, but this finding needs replication. Larger studies are needed to confirm whether pre-eclampsia is associated with impaired childhood lung function.

Live-Birth Rate Associated With Repeat In Vitro Fertilization Treatment Cycles

IMPORTANCE

The likelihood of achieving a live birth with repeat in vitro fertilization (IVF) is unclear, yet treatment is commonly limited to 3 or 4 embryo transfers.

OBJECTIVE

To determine the live-birth rate per initiated ovarian stimulation IVF cycle and with repeated cycles.

DESIGN, SETTING, AND PARTICIPANTS

Prospective study of 156,947 UK women who received 257,398 IVF ovarian stimulation cycles between 2003 and 2010 and were followed up until June 2012.

EXPOSURES

In vitro fertilization, with a cycle defined as an episode of ovarian stimulation and all subsequent separate fresh and frozen embryo transfers.

MAIN OUTCOMES AND MEASURES

Live-birth rate per IVF cycle and the cumulative live-birth rates across all cycles in all women and by age and treatment type. Optimal, prognosis-adjusted, and conservative cumulative live-birth rates were estimated, reflecting 0%, 30%, and 100%, respectively, of women who discontinued due to poor prognosis and having a live-birth rate of 0 had they continued.

RESULTS

Among the 156,947 women, the median age at start of treatment was 35 years (interquartile range, 32-38; range, 18-55), and the median duration of infertility for all 257,398 cycles was 4 years (interquartile range, 2-6; range, <1-29). In all women, the live-birth rate for the first cycle was 29.5% (95% CI, 29.3%-29.7%). This remained above 20% up to and including the fourth cycle. The cumulative prognosis-adjusted live-birth rate across all cycles continued to increase up to the ninth cycle, with 65.3% (95% CI, 64.8%-65.8%) of women achieving a live birth by the sixth cycle. In women younger than 40 years using their own oocytes, the live-birth rate for the first cycle was 32.3% (95% CI, 32.0%-32.5%) and remained above 20% up to and including the fourth cycle. Six cycles achieved a cumulative prognosis-adjusted live-birth rate of 68.4% (95% CI, 67.8%-68.9%). For women aged 40 to 42 years, the live-birth rate for the first cycle was 12.3% (95% CI, 11.8%-12.8%), with 6 cycles achieving a cumulative prognosis-adjusted live-birth rate of 31.5% (95% CI, 29.7%-33.3%). For women older than 42 years, all rates within each cycle were less than 4%. No age differential was observed among women using donor oocytes. Rates were lower for women with untreated male partner-related infertility compared with those with any other cause, but treatment with either intracytoplasmic sperm injection or sperm donation removed this difference.

CONCLUSIONS AND RELEVANCE

Among women in the United Kingdom undergoing IVF, the cumulative prognosis-adjusted live-birth rate after 6 cycles was 65.3%, with variations by age and treatment type. These findings support the efficacy of extending the number of IVF cycles beyond 3 or 4.

Re-Examining the Association between Vitamin D and Childhood Caries

Background

Previous studies have reported an inverse association between vitamin D and childhood dental caries, but whether this is causal is unclear.

Objective

To determine the causal effect of circulating 25-hydroxyvitamin D concentration on dental caries experience, early caries onset and the requirement for a dental general anesthetic.

Design

A Mendelian randomization study was undertaken, using genetic variants known to be associated with circulating 25-hydroxyvitamin D concentrations in 5,545 European origin children from the South West of England. Data on caries and related characteristics were obtained from parental and child completed questionnaires between 38 and 91 months and clinical assessments in a random 10% sample at 31, 44 and 61 months.

Results

In multivariable confounder adjusted analyses no strong evidence for an association of 25-hydroxyvitamin D with caries experience or severity was found but there was evidence for an association with early caries onset, or having a general anesthetic for dental problems. In Mendelian randomization analysis the odds ratio for caries experience per 10 nmol/L increase in 25-hydroxyvitamin D was 0.93 (95% confidence interval: 0.83, 1.05; P = 0.26) and the odds ratio for dental general anaesthetic per 10 nmol/L increase in 25-hydroxyvitamin D was 0.96 (95% confidence interval: 0.75, 1.22; P = 0.72).

Conclusions

This Mendelian randomization study provides little evidence to support an inverse causal effect of 25-hydroxyvitamin D on dental caries. However, the estimates are imprecise and a larger study is required to refine these analyses.