Differences between brachial and aortic blood pressure in adolescence and their implications for diagnosis of hypertension

OBJECTIVES

Blood pressure (BP) is the leading global cause of mortality, and its prevalence is increasing in children and adolescents. Aortic BP is lower than brachial BP in adults. We aimed to assess the extent of this difference and its impact on the diagnosis of hypertension among adolescents.

METHODS

We used data from 3850 participants from a UK cohort of births in the early 1990s in the Southwest of England, who attended their ∼17-year follow-up and had valid measures of brachial and aortic BP at that clinic [mean (SD) age 17.8 (0.4) years, 66% female individuals]. Data are presented as mean differences [95% prediction intervals] for both sexes.

RESULTS

Aortic systolic BP (SBP) was lower than brachial SBP [male, -22.3 (-31.2, -13.3) mmHg; female, -17.8 (-25.5, -10.0) mmHg]. Differences between aortic and brachial diastolic BP (DBP) were minimal. Based on brachial BP measurements, 101 male individuals (6%) and 22 female individuals (1%) were classified as hypertensive. In contrast, only nine male individuals (<1%) and 14 female individuals (<1%) met the criteria for hypertension based on aortic BP, and the predictive value of brachial BP for aortic hypertension was poor (positive-predictive value = 13.8%). Participants with aortic hypertension had a higher left ventricular mass index than those with brachial hypertension.

CONCLUSION

Brachial BP substantially overestimates aortic BP in adolescents because of marked aortic-to-brachial pulse pressure amplification. The use of brachial BP measurement may result in an overdiagnosis of hypertension during screening in adolescence.

Associations of Maternal Educational Level, Proximity to Greenspace During Pregnancy, and Gestational Diabetes With Body Mass Index From Infancy to Early Adulthood: A Proof-of-Concept Federated Analysis in 18 Birth Cohorts

International sharing of cohort data for research is important and challenging. We explored the feasibility of multi-cohort federated analyses by examining associations between three pregnancy exposures (maternal education, exposure to green vegetation and gestational diabetes) with offspring BMI from infancy to 17 years. We used data from 18 cohorts (n=206,180 mother-child pairs) from the EU Child Cohort Network and derived BMI at ages 0-1, 2-3, 4-7, 8-13 and 14-17 years. Associations were estimated using linear regression via one-stage IPD meta-analysis using DataSHIELD. Associations between lower maternal education and higher child BMI emerged from age 4 and increased with age (difference in BMI z-score comparing low with high education age 2-3 years = 0.03 [95% CI 0.00, 0.05], 4-7 years = 0.16 [95% CI 0.14, 0.17], 8-13 years = 0.24 [95% CI 0.22, 0.26]). Gestational diabetes was positively associated with BMI from 8 years (BMI z-score difference = 0.18 [CI 0.12, 0.25]) but not at younger ages; however associations attenuated towards the null when restricted to cohorts which measured GDM via universal screening. Exposure to green vegetation was weakly associated with higher BMI up to age one but not at older ages. Opportunities of cross-cohort federated analyses are discussed.

Protocol for the PLAY Study: a randomised controlled trial of an intervention to improve infant development by encouraging maternal self-efficacy using behavioural feedback

INTRODUCTION

The early infant caregiving environment is crucial in the formation of parent-child relationships, neurobehavioural development and thus child outcomes. This protocol describes the Play Love And You (PLAY) Study, a phase 1 trial of an intervention designed to promote infant development through encouraging maternal self-efficacy using behavioural feedback, and supportive interventions.

METHODS AND ANALYSIS

210 mother-infant pairs will be recruited at delivery from community clinics in Soweto, South Africa, and individually randomised (1:1) into two groups. The trial will consist of a standard of care arm and an intervention arm. The intervention will start at birth and end at 12 months, and outcome assessments will be made when the infants are 0, 6 and 12 months of age. The intervention will be delivered by community health helpers using an app with resource material, telephone calls, in person visits and behavioural feedback with individualised support. Every 4 months, mothers in the intervention group will receive rapid feedback via the app and in person on their infant's movement behaviours and on their interaction styles with their infant. At recruitment, and again at 4 months, mothers will be screened for mental health risk and women who score in the high-risk category will receive an individual counselling session from a licensed psychologist, followed by referral and continued support as necessary. The primary outcome is efficacy of the intervention in improving maternal self-efficacy, and the secondary outcomes are infant development at 12 months, and feasibility and acceptability of each component of the intervention.

ETHICS AND DISSEMINATION

The PLAY Study has received ethical approval from the Human Research Ethics Committee of the University of the Witwatersrand (M220217). Participants will be provided with an information sheet and required to provide written consent prior to being enrolled. Study results will be shared via publication in peer-reviewed journals, conference presentation and media engagement.

TRIAL REGISTRATION NUMBER

This trial was registered with the Pan African Clinical Trials Registry (https://pactr.samrc.ac.za) on 10 February 2022 (identifier: PACTR202202747620052).

Abstract P5-03-06: Effect of Sleep Traits on Subtype Specific Breast Cancer Survival: a Mendelian Randomization Analysis

Background There is increasing interest in the relationship between sleep traits and both quality of life and survival in breast cancer. Recent work has found that oestrogen receptor positive (ER+) tumour cells are more likely to spread, via the circulation, at night than in the morning, providing support for a potential role of sleep characteristics influencing metastasis and therefore survival from breast cancer. The aim of this study was to investigate causal effects of sleep traits on subtype-specific breast cancer survival. Methods Single-nucleotide polymorphisms (SNPs) identified from GWAS associated with sleep traits with were used as a genetic instruments for Chronotype (N=697,828), Insomnia (N=1,331,010), Sleep Duration (N=446,118), Napping (N=452,633), Daytime sleepiness(N=452,071) and Ease of Getting up (N=461,658). All instruments were identified in data from UK Biobank, except chronotype and insomnia, which were identified in meta-analyses of UK Biobank and 23andme. For all instruments female-specific effect estimates were used. For these SNPs, summary statistics of their association with breast cancer survival were obtained from GWAS meta-analyses of European women from the Breast Cancer Association Consortium (BCAC), (N=91,686, with 7531 breast cancer specific deaths over a median follow-up of 8.1 years). To estimate the causal effect of the sleep traits on breast cancer survival, we applied two-sample MR for both overall and subtype-specific breast cancer (Luminal A-like, Luminal B-like, Human Epidermal Growth Factor 2 (Her2) positive, Her2 negative and triple negative (TNBC)). Further stratification by tumour characteristics at diagnosis and treatment received was also used. Sensitivity analyses were used to assess the robustness of main analyses to MR assumptions. Results For every hour increase in sleep duration, we observed worsening 5-year breast cancer specific survival in patients with ER+ tumours who received endocrine therapy (HR: 2.55, 95% CI: 1.10, 5,82) and for all patients receiving aromatase inhibitors (HR: 9.57, 95% CI: 1.61, 57.10). Conversely, improved 5-year survival was observed in patients with ER- tumours who received chemotherapy (HR: 0.30, 95% CI: 0.10, 0.87) and all patients receiving taxanes (HR: 0.23, 95% CI: 0.05, 0.98). We also observed that an increase in daytime sleepiness improved 15-year survival in patients both overall (HR: 0.34, 95% CI: 0.14, 0.80) and with lymph node negative tumours at diagnosis (HR: 0.12, 95% CI: 0.02, 0.64). Detailed sensitivity analyses are ongoing. Conclusions The current study uses a causal approach to identify potential effects between sleep patterns and breast cancer survival and confirms the previously observed relationships with increased sleep duration and worse survival in ER+ breast cancer. The reasons for opposite effects seen in those with ER- and those receiving taxanes needs further mechanistic work. Although the improved survival in relation to increased daytime sleepiness appears to be in-keeping with previous findings, this may largely reflect shorter sleep duration. Further work accurately characterising sleep quality, rather than duration in those with breast cancer, examining the effects on quality of life and survival and establishing mechanisms are needed.

Citation Format: Bryony Hayes, Richard Martin, Deborah Lawlor, Rebecca Richmond, Tim Robinson. Effect of Sleep Traits on Subtype Specific Breast Cancer Survival: a Mendelian Randomization Analysis [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-03-06.

Surgical-PEARL protocol: a multicentre prospective cohort study exploring aetiology, management and outcomes for patients with congenital anomalies potentially requiring surgical intervention

INTRODUCTION

Congenital anomalies affect over 2% of pregnancies. Surgical advances have reduced mortality and improved survival for patients with congenital anomalies potentially requiring surgical (CAPRS) intervention. However, our understanding of aetiology, diagnostic methods, optimal management, outcomes and prognostication is limited. Existing birth cohorts have low numbers of individual heterogenous CAPRS. The Surgical Paediatric congEnital Anomalies Registry with Long term follow-up (Surgical-PEARL) study aims to establish a multicentre prospective fetal, child and biological parent cohort of CAPRS.

METHODS AND ANALYSIS

From 2022 to 2027, Surgical-PEARL aims to recruit 2500 patients with CAPRS alongside their biological mothers and fathers from up to 15 UK centres. Recruitment will be antenatal or postnatal dependent on diagnosis timing and presentation to a recruitment site. Routine clinical data including antenatal scans and records, neonatal intensive care unit (NICU) records, diagnostic and surgical data and hospital episode statistics will be collected. A detailed biobank of samples will include: parents' blood and urine samples; amniotic fluid if available; children's blood and urine samples on admission to NICU, perioperatively or if the child has care withdrawn or is transferred for extracorporeal membrane oxygenation; stool samples; and surplus surgical tissue. Parents will complete questionnaires including sociodemographic and health data. Follow-up outcome and questionnaire data will be collected for 5 years. Once established we will explore the potential of comparing findings in Surgical-PEARL to general population cohorts born in the same years and centres.

ETHICS AND DISSEMINATION

Ethical and health research authority approvals have been granted (IRAS Project ID: 302251; REC reference number 22/SS/0004). Surgical-PEARL is adopted onto the National Institute for Health Research Clinical Research Network portfolio. Findings will be disseminated widely through peer-reviewed publication, conference presentations and through patient organisations and newsletters.

TRIAL REGISTRATION NUMBER

ISRCTN12557586.

Exposure to natural environments during pregnancy and birth outcomes in 11 European birth cohorts

Research suggests that maternal exposure to natural environments (i.e., green and blue spaces) promotes healthy fetal growth. However, the available evidence is heterogeneous across regions, with very few studies on the effects of blue spaces. This study evaluated associations between maternal exposure to natural environments and birth outcomes in 11 birth cohorts across nine European countries. This study, part of the LifeCycle project, was based on a total sample size of 69,683 newborns with harmonised data. For each participant, we calculated seven indicators of residential exposure to natural environments: surrounding greenspace in 100m, 300m, and 500m using Normalised Difference Vegetation Index (NDVI) buffers, distance to the nearest green space, accessibility to green space, distance to the nearest blue space, and accessibility to blue space. Measures of birth weight and small for gestational age (SGA) were extracted from hospital records. We used pooled linear and logistic regression models to estimate associations between exposure to the natural environment and birth outcomes, controlling for the relevant covariates. We evaluated the potential effect modification by socioeconomic status (SES) and region of Europe and the influence of ambient air pollution on the associations. In the pooled analyses, residential surrounding greenspace in 100m, 300m, and 500m buffer was associated with increased birth weight and lower odds for SGA. Higher residential distance to green space was associated with lower birth weight and higher odds for SGA. We observed close to null associations for accessibility to green space and exposure to blue space. We found stronger estimated magnitudes for those participants with lower educational levels, from more deprived areas, and living in the northern European region. Our associations did not change notably after adjustment for air pollution. These findings may support implementing policies to promote natural environments in our cities, starting in more deprived areas.

Maternal vitamin D during pregnancy and offspring autism and autism-associated traits: a prospective cohort study

BACKGROUND

There has been a growing interest in the association between maternal levels of vitamin D during pregnancy and offspring autism. However, whether any associations reflect causal effects is still inconclusive.

METHODS

We used data from a UK-based pregnancy cohort study (Avon Longitudinal Study of Parents and Children) comprising 7689 births between 1991 and 1992 with maternal blood vitamin D levels recorded during pregnancy and at least one recorded outcome measure, including autism diagnosis and autism-associated traits. The association between each outcome with seasonal and gestational age-adjusted maternal serum 25-hydroxyvitamin D during pregnancy was estimated using confounder-adjusted regression models. Multiple imputation was used to account for missing data, and restricted cubic splines were used to investigate nonlinear associations. Mendelian randomization was used to strengthen causal inference.

RESULTS

No strong evidence of an association between maternal serum 25-hydroxyvitamin D during pregnancy and any offspring autism-associated outcome was found using multivariable regression analysis (autism diagnosis: adjusted OR = 0.98, 95% CI = 0.90-1.06), including with multiple imputation (autism diagnosis: adjusted OR = 0.99, 95% CI = 0.93-1.06), and no evidence of a causal effect was suggested by Mendelian randomization (autism diagnosis: causal OR = 1.08, 95% CI = 0.46-2.55). Some evidence of increased odds of autism-associated traits at lower levels of maternal serum 25-hydroxyvitamin D was found using spline analysis.

LIMITATIONS

Our study was potentially limited by low power, particularly for diagnosed autism cases as an outcome. The cohort may not have captured the extreme lows of the distribution of serum 25-hydroxyvitamin D, and our analyses may have been biased by residual confounding and missing data.

CONCLUSIONS

The present study found no strong evidence of a causal link between maternal vitamin D levels in pregnancy and offspring diagnosis or traits of autism.

A national cohort of children born after assisted conception in the UK (1992-2009)

ObjectiveTo establish a cohort of children consisting of those born after assisted reproductive technology (ART) in the UK between 1992 and 2009, their naturally conceived siblings (NCS) and matched naturally conceived population controls (NCP) and linking this to postnatal health records up to 2015. MethodsDeterministic record linkage between the Human Fertilization & Embryology Authority (HFEA) register and Office for National Statistics (ONS) birth registration datasets was carried out to identify a cohort of children born after ART between 1992 and 2009, their NCS, and matched NCP controls (HFEA-ONS linkage). This cohort was linked to the UK Hospital Episode Statistics database to allow monitoring of the child’s post-natal health outcomes up to 2015 (HFEA-ONS-HES linkage). Birthweight and health outcomes were compared between groups and by treatment type. ResultsThe HFEA-ONS linkage consisted of 75348 children born after non-donor ART carried out in the UK between 1st April 1992 and 31st July 2009, 14763 NCS and 164823 matched NCP controls. Of these, 63877 ART, 11343 NCS, and 127544 matched NCP controls were linked to hospital admissions and outpatient data (HFEA-ONS-HES sub-cohort). The study had 1.6-million-person years of follow-up (mean: 12.9 years; range 0-19 years). Children born after fresh embryo transfers were lighter and those born after frozen embryo transfers were heavier than the NCP controls. The within-sibling analyses were directionally consistent with the NCP analyses, but attenuated for the fresh vs NC and increased for the frozen vs NC analyses. ART singletons had increased risk of hospital admission as well as higher admission rates compared to NCP but not NCS. ConclusionBespoke record linkage was carried out to generate a new child cohort for use in exploring the relationship between conception via ART and short- and long-term health outcomes in offspring. Identification of NCS as well as matched NCP controls allows exploration of the association of ART with adverse offspring outcomes while accounting for parental factors related to sub-fertility which may confound these associations.

Vulnerabilities in child well-being among primary school children: a cross-sectional study in Bradford, UK

OBJECTIVE

To describe the prevalence of factors related to well-being among primary school children in a deprived multiethnic community in the UK.

DESIGN AND PARTICIPANTS

Cross-sectional survey of 15 641 children aged 7-10 years in Born in Bradford's Primary School Years study: whole-classroom samples in 89 Bradford primary schools between 2016 and 2019.

MAIN OUTCOME MEASURES

Prevalence estimates by ethnicity (%, 95% CI) of single and multiple vulnerabilities in child well-being within and across four domains (Home, Family, Relationships; Material Resources; Friends and School; Subjective Well-being).

RESULTS

Only 10% of children had no vulnerabilities in any domain of well-being; 10% had one or more vulnerabilities in all four domains. The highest prevalence estimates were for being bullied some or all of the time (52.7%, 95% CI: 51.9% to 53.4%), keeping worries to oneself (31.2%, 95% CI: 30.5% to 31.9%), having no park near home (30.8%, 95% CI: 30.1% to 31.5%) and worrying all the time about how much money their family has (26.3%, 95% CI: 25.6% to 27%). Boys were consistently significantly more likely than girls to report all of the vulnerabilities in the Home, Family and Family Relationships domain, and the majority of indicators in the other domains, and in all domains except Friends and School, boys were significantly more likely to have at least one vulnerability. Girls were significantly more likely to report not having many friends (16.7%, 95% CI: 15.9% to 17.6% vs 12.5%, 95% CI: 11.8% to 13.2%), being bullied some or all of the time (55.8%, 95% CI: 54.7% to 56.9% vs 49.7%, 95% CI: 48.6% to 50.8%) and feeling left out all the time (12.1%, 95% CI: 11.4% to 12.8%) versus (10.3%, 95% CI: 9.7% to 11.0%). Variations in vulnerabilities by ethnicity were complex, with children in black, Asian and minority ethnic groups sometimes reporting more vulnerabilities and sometimes fewer than white British children. For example, compared with children of Pakistani heritage, white British children were more likely to say that their family never gets along well (6.3%, 95% CI: 5.6% to 7.1% vs 4.1%, 95% CI: 3.6% to 4.6%) and to have no access to the internet at home (22.3%, 95% CI: 21% to 23.6% vs 18%, 95% CI: 17% to 18.9%). Children with Pakistani heritage were more likely than white British children to say they had no park near their home where they can play with friends (32.7%, 95% CI: 31.6% to 33.9% vs 29.9%, 95% CI: 28.6% to 31.3%), to report not having three meals a day (17.9%, 95% CI: 16.9% to 18.8% vs 11.9%, 95% CI: 10.9% to 12.9%) and to worry all the time about how much money their families have (29.3%, 95% CI: 28.2% to 30.3%) vs (21.6%, 95% CI: 20.4% to 22.9%). Gypsy/Irish Traveller children were less likely than white British children to say they were bullied some or all of the time (42.2%, 95% CI: 35.4% to 49.4% vs 53.8%, 95% CI: 52.3% to 55.3%), but more likely to say they were mean to others all the time (9.9%, 95% CI: 6.3% to 15.2% vs 4%, 95% CI: 3.5% to 4.7%) and can never work out what to do when things are hard (15.2%, 95% CI: 10.6% to 21.2% vs 9%, 95% CI: 8.2% to 9.9%). We considered six vulnerabilities to be of particular concern during the COVID-19 pandemic and associated national and local lockdowns: family never gets along well together; no garden where child can play; no nearby park where they can play; not having three meals a day; no internet at home; worried about money all the time. Pre-pandemic, 37.4% (95% CI: 36.6% to 38.3%) of Bradford children had one of these vulnerabilities and a further 29.6% (95% CI: 28.9% to 30.4%) had more than one.

CONCLUSIONS

Although most primary school children aged 7-10 in our study had good levels of well-being on most indicators across multiple domains, fewer than 10% had no vulnerabilities at all, a worrying 10% had at least one vulnerability in all the four domains we studied and two-thirds had vulnerabilities of particular concern during the COVID-19 lockdowns.

0490 Longitudinal associations between sleep and behavior and cognition in preschoolers from five European birth-cohorts

Introduction

There has been little focus on sleep and its relation to behavior and cognition in preschool-aged children. We aimed to investigate the association between sleep duration in early preschoolers (» 3.5 years of age) and later behavioral and cognitive outcomes (» 5 years of age) in European children.

Methods

We used harmonized data from five cohorts from the EU Child Cohort Network, established by the LifeCycle Project (n=16.444 children): ALSPAC and SWS from UK, EDEN and ELFE from France and INMA from Spain. Within all cohorts, total sleep duration per day and behavioral and cognitive information were reported by parents. Internalizing and externalizing behaviors were measured with the Strengths and Difficulties Questionnaire and treated as percentile scores. Verbal and non-verbal intelligence were assessed by the Wechsler Preschool and Primary Scale of Intelligence or with the McCarthy Scales of Children’s Abilities depending on the cohort and treated as standardized scores. All scores were cohort specific. Associations between sleep duration during early preschool age and later behavior and/or cognition were estimated using linear regression and pooled with two-stage individual participant data meta-analysis adjusted for child, maternal and household information. Analyses were done in DataSHIELD.

Results

Global mean sleep duration was 11h54 ± 1h00 per day at mean age 3.5 years but differed by country, with children from France showing longer sleep duration than children from the UK or Spain. In multivariate meta-analysis, 1 hour of additional sleep duration per day at mean age 3.5 years was associated with reduced internalizing and externalizing behavior percentile scores at mean age 5.1 years (internalizing behavior: badjusted= -1.05, 95%-CI [-1.93, -0.18], I2: 30.3%; externalizing behavior: badjusted= -2.12, 95%-CI [-2.78, -1.47], I2: 0.0%). No association was observed between sleep duration and subsequent verbal or non-verbal intelligence

Conclusion

Longer sleep duration in early preschool age (» 3.5 years of age) was associated with subsequent lower internalizing and externalizing behavior scores (» 5 years of age), but not with verbal or non-verbal intelligence. Adequate sleep duration at an early age is important for children’s later mental health.

Support (If Any)

KG was granted a LifeCycle fellowship.

Maternal haemoglobin levels in pregnancy and child DNA methylation: a study in the pregnancy and childhood epigenetics consortium

Altered maternal haemoglobin levels during pregnancy are associated with pre-clinical and clinical conditions affecting the fetus. Evidence from animal models suggests that these associations may be partially explained by differential DNA methylation in the newborn with possible long-term consequences. To test this in humans, we meta-analyzed the epigenome-wide associations of maternal haemoglobin levels during pregnancy with offspring DNA methylation in 3,967 newborn cord blood and 1,534 children and 1,962 adolescent whole-blood samples derived from 10 cohorts. DNA methylation was measured using Illumina Infinium Methylation 450K or MethylationEPIC arrays covering 450,000 and 850,000 methylation sites, respectively. There was no statistical support for the association of maternal haemoglobin levels with offspring DNA methylation either at individual methylation sites or clustered in regions. For most participants, maternal haemoglobin levels were within the normal range in the current study, whereas adverse perinatal outcomes often arise at the extremes. Thus, this study does not rule out the possibility that associations with offspring DNA methylation might be seen in studies with more extreme maternal haemoglobin levels.

1484Selection bias in COVID-19 research: Prospective analyses of two UK cohort studies

Background

Non-random sampling could bias estimates of association in observational studies but the extent to which this occurs in studies of SARS-CoV-2 infection/COVID-19 severity is not well established.

Methods

Using ALSPAC and UK Biobank we investigated pre-pandemic predictors of selection (i.e. having data on SARS-CoV-2 infection and COVID-19 severity from self-report and/or health record linkage). We conducted empirical analyses and simulations to explore the potential presence, direction and magnitude of bias due to selection when estimating the association of BMI with SARS-CoV-2 infection and COVID-19 severity.

Results

A broad range of characteristics related to selection in both cohorts, sometimes in opposite directions. We found bias in all simulated scenarios, mostly of small magnitude. Both the direction and magnitude of bias was influenced by the presence of an effect of BMI on SARS-CoV-2 infection and COVID-19 severity and the control group definition used (e.g. assuming no effect of BMI on SARS-CoV-2 infection our main simulation showed bias equivalent to an estimated odds ratio of 0.99 when using non-infected controls but 1.16 when using controls combining non-infected and non-assessed).

Conclusions

Despite small amounts of bias in most scenarios, a control group definition including those non-assessed (e.g. non-tested) can induce more bias. In large samples such as UK Biobank the statistical power means incorrect conclusions could be made.

Key messages

Observational studies estimating associations of factors with SARS-CoV-2 or COVID-19 may be biased due to non-random selection into the analytic sample.

586Effects of maternal circulating amino acids on offspring birthweight: a Mendelian randomisation analysis

Background

It is suggested amino acids are critical for fetal growth, but analyses assessing causality are lacking. Mendelian randomisation (MR) can be used to examine causal effects under instrumental variable (IV) assumptions.

Methods

We conducted a two-sample MR study utilizing summary data from genome-wide association studies (GWAS) of amino acids (sample 1, n = 86,507) and of offspring birthweight (sample 2, combined UK Biobank and Early Growth Genetics Consortium, n = 406,063). Seventy-five independent single nucleotide polymorphisms (SNPs) robustly associated with 18 amino acids (p &lt; 4.9 × 10-10) were used as genetic instruments. Wald ratio and inverse variance weighted methods were used in MR main analysis. Sensitivity analyses were performed to explore IV assumption violations. To explore whether there was consistency between SNP-amino acid associations in pregnancy and in the GWAS, the latter were compared to associations in the Born in Bradford cohort.

Results

There was evidence of positive causal effects of maternal alanine (51.9 g birthweight increase per SD increase in amino acid level, 95% CI: 24.2, 79.5), glutamine (51.3 g, 95% CI: 33.5, 69.0), glycine (10.4 g, 95% CI: 1.3, 19.6) and serine (27.1 g, 95% CI: 11.2, 43.0) on birthweight and inverse causal effects of maternal isoleucine (-109.7 g, 95% CI: -194.6, -24.9) and histidine (-41.1 g, 95% CI: -78.5, -3.7) on birthweight. Sensitivity analyses to explore reverse causality and bias due to horizontal pleiotropy supported our findings.

Conclusions

Some maternal circulating amino acids have causal effects on birthweight.

Key messages

MR can be extended to probe effects of maternal nutrition on offspring development.

221Association of physical activity bout length and changing intensity with mortality in UK Biobank

Background

Spending more time active (and less time sedentary) is associated with many health benefits but it is unclear whether these associations differ depending on whether time spent sedentary or in moderate-vigorous physical activity (MVPA) is accumulated in long or short bouts. We used a novel analytical approach to examine whether length of sedentary and MVPA bouts associates with all-cause mortality.

Methods

We used data on 79,507 participants from UK Biobank. We derived the total time participants spent in activity categories (sleep, sedentary, light activity and MVPA) and in sedentary and MVPA bouts of short (1-15 minutes), medium (16-40 minutes) and long (41+ minutes) duration, on average per day. We used Cox proportion hazards regression to estimate the association of spending 10 minutes more average daily time in one activity or bout length category, coupled with spending 10 minutes less time in another, with all-cause mortality.

Results

Those spending more time in MVPA had lower mortality risk, irrespective of whether this replaced time spent sleeping, sedentary or in light activity. We found little evidence to suggest that mortality risk differed depending on the length of sedentary or MVPA bouts.

Conclusions

We uniquely show that higher total MVPA improves health irrespective of whether it is obtained from several short bouts or fewer longer bouts, supporting recent policy changes in some countries.

Key messages

Our results suggest that time spent in MVPA associates with lower mortality risk irrespective of whether it is obtained from several short bouts or fewer longer bouts.

454Relationships between sleep traits and metabolic profiles: evidence from multivariable regression and Mendelian randomization analyses

Background

Sleep traits are associated with cardiometabolic disease. The aim of this study was to explore the causal effect of sleep traits (duration and insomnia) on multiple metabolic traits.

Methods

We used age, sex and BMI adjusted multivariable regression (N = 17,370) and two-sample summary statistic Mendelian randomization (MR) to examine effects of sleep duration and insomnia symptoms on ∼150 NMR metabolites. Multivariable analyses were conducted on data from nine European cohorts and meta-analysed. MR analyses utilised summary statistics from published genome-wide association studies (GWAS) of self-reported sleep traits (sample 1; N = 446,118 to 1,331,010) and from GWAS on NMR serum metabolites (sample 2; N = 38,618). We used inverse-variance weighted (IVW) for the main MR analyses and weighed median (WM) and MR-Egger to explore bias due to pleiotropy.

Results

MR IVW and multivariable analyses both suggest a positive effect of insomnia symptoms on glycoprotein acetyls (MR: 0.06 s.d. increase in mean concentration comparing any symptoms to none; p = 5.9e-4) and between total sleep duration and creatinine (MR: 0.16 s.d. increase per additional hour; p = 0.03). WM and MR-Egger analyses show consistent results. There was evidence for thirteen and eight effects of insomnia and duration in multivariable only and three and one, respectively, in MR only.

Conclusions

Insomnia symptoms lead to higher levels of an inflammatory marker (glycoprotein acetyls) and longer sleep duration leads to higher creatinine levels.

Key messages

We found no evidence of widespread metabolic disruption by sleep traits.

1518Preterm birth and trajectories of cardiometabolic health measures from birth to adulthood

Background

Preterm birth is associated with increased cardiovascular disease risk, but it is unclear when this risk emerges. We compared life course trajectories from birth to adulthood of multiple cardiometabolic health measures in adults born preterm compared with term.

Methods

Multilevel models were used to compare trajectories from birth to age 25 years of BMI, fat mass, lean mass, systolic and diastolic blood pressure (BP), lipids, glucose and insulin, between participants born preterm (N = 311-560) and term (N = 5365-9262) in a contemporary UK birth cohort study. We also investigated gestational age as a continuum.

Results

Systolic and diastolic BP were higher at age 7 (mean predicted differences 0.8mmHg; 95%CI -0.1, 1.7 and 0.7mmHg; 95%CI 0.03, 1.3, respectively). The difference in SBP persisted and in DBP disappeared by 25 years. Preterm participants had lower BMI between 7 and 18 years, but by age 25, there was no difference. Lean mass and fat mass (measured from age 9 only) trajectories were consistent with BMI. HDL-c was higher, and triglycerides lower at birth in those born preterm, but this difference disappeared by 25 years. No other differences were found.

Conclusions

There were few, modest differences in cardiometabolic health measures during early life in those born preterm versus term. All disappeared by age 25, except SBP. Longer follow-up is needed to establish if and when trajectories diverge.

Key messages

By age 25, there were no differences in measures of cardiometabolic health between people born preterm and term except for a higher SBP in those born preterm.

Cohort profile: a national, population-based cohort of children born after assisted conception in the UK (1992-2009): methodology and birthweight analysis

PURPOSE

To generate a large cohort of children born after assisted reproductive technology (ART) in the UK between 1992 and 2009, their naturally conceived siblings (NCS) and matched naturally conceived population (NCP) controls and linking this with health outcome data to allow exploration of the effects of ART. The effects of fresh and frozen embryo transfer on birth weight (BW) were analysed to test the validity of the cohort.

PARTICIPANTS

Children recorded on the Human Fertilisation and Embryology Authority (HFEA) register as being born after ART between 1992 and 2009, their NCS and matched NCP controls linked to Office for National Statistics birth registration dataset (HFEA-ONS cohort). This cohort was further linked to the UK Hospital Episode Statistics database to allow monitoring of the child's post-natal health outcomes up to 2015 (HFEA-ONS-HES subcohort).

FINDINGS TO DATE

The HFEA-ONS cohort consisted of 75 348 children born after non-donor ART carried out in the UK between 1 April 1992 and 31 July 2009 and successfully linked to birth registration records, 14 763 NCS and 164 823 matched NCP controls. The HFEA-ONS-HES subcohort included 63 877 ART, 11 343 NCS and 127 544 matched NCP controls further linked to health outcome data. The exemplar analysis showed that children born after fresh embryo transfers were lighter (BW difference: -131 g, 95% CI: -140 to -123) and those born after frozen embryo transfers were heavier (BW difference: 35 g, 95% CI: 19 to 52) than the NCP controls. The within-sibling analyses were directionally consistent with the population control analyses, but attenuated markedly for the fresh versus natural conception (BW difference: -54 g; 95% CI: -72 to -36) and increased markedly for the frozen versus natural conception (BW difference: 152 g; 95% CI: 113 to 190) analyses.

FUTURE PLANS

To use this cohort to explore the relationship between ART conception and short-term and long-term health outcomes in offspring.

The mother during pregnancy and the puerperium: Detailed data abstracted from the clinical obstetric records of ALSPAC pregnancies

Background: When the Avon Longitudinal Study of Parents and Children (ALSPAC) was planned, it was assumed that the clinical obstetric data would be easily accessible from the newly developed National Health Service computerised ‘STORK’ system. Pilot studies, however, showed that, although fairly accurate in regard to aspects of labour and delivery, it was, at the time (1990-2), inadequate for identifying the full antenatal and postnatal details of clinical complications and treatments of the women in the Study. Methods: A scheme was therefore developed to train research staff to find and abstract relevant details from clinical records onto proformas designed for the purpose. Extracting such data proved very time consuming (up to six hours for complicated pregnancies) and consequently expensive. Funding for the enterprise was obtained piecemeal using specific focussed grants to extract data for subsamples of the Study, including a random sample to serve as controls. Results: To date, detailed records have been completed for 8369 pregnancies, and a further 5336 (13,705 in total) have complete details on specific prenatal areas, including serial measures of maternal blood pressure, proteinuria and weight. In this Data Note we describe the information abstracted from the obstetric medical records concerning the mother during pregnancy, labour, delivery and the first two weeks of the puerperium. Information abstracted relating to the fetus (including fetal monitoring, presentation, method of delivery) and neonate (signs of asphyxia, resuscitation, treatment and well-being) will be described in a further Data Note. Conclusions: These data add depth to ALSPAC concerning ways in which the signs and symptoms, procedures and treatments of the mother prenatally, intrapartum and postnatally, may impact on the long-term health and development of both mother and child. They augment the data collected from the mothers’ questionnaires and the ‘STORK’ digital hospital data.

External validation of the improving partial risk adjustment in surgery (PRAIS-2) model for 30-day mortality after paediatric cardiac surgery

OBJECTIVE

Independent temporal external validation of the improving partial risk adjustment in surgery model (PRAIS-2) to predict 30-day mortality in patients undergoing paediatric cardiac surgery.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Paediatric cardiac surgery.

INTERVENTION

PRAIS-2 validation was carried out using a two temporally different single centre (Bristol, UK) cohorts: Cohort 1 surgery undertaken from April 2004 to March 2009 and Cohort 2 from April 2015 to July 2019. For each subject PRAIS-2 score was calculated according to the original formula.

PARTICIPANTS

A total of 1352 (2004-2009) and 1197 (2015-2019) paediatric cardiac surgical procedures were included in the Cohort 1 and Cohort 2, respectively (median age at the procedure 6.3 and 7.1 months).

PRIMARY AND SECONDARY OUTCOME MEASURES

PRAIS-2 performance was assessed in terms of discrimination by means of ROC (receiver operating characteristic) curve analysis and calibration by using the calibration belt method.

RESULTS

PRAIS-2 score showed excellent discrimination for both cohorts (AUC 0.72 (95%CI: 0.65 to 0.80) and 0.88 (95%CI: 0.82 to 0.93), respectively). While PRAIS-2 was only marginally calibrated in Cohort 1, with a tendency to underestimate risk in lowrisk and overestimate risk in high risk procedures (P-value = 0.033), validation in Cohort 2 showed good calibration with the 95% confidence belt containing the bisector for predicted mortality (P-value = 0.143). We also observed good prediction accuracy in the non-elective procedures (N = 483;AUC 0.78 (95%CI 0.68 to 0.87); Calibration belt containing the bisector (P-value=0.589).

CONCLUSIONS

In a single centre UK-based cohort, PRAIS-2 showed excellent discrimination and calibration in predicting 30-day mortality in paediatric cardiac surgery including in those undergoing non-elective procedures. Our results support a wider adoption of PRAIS-2 score in the clinical practice.

Using Mendelian randomization to determine causal effects of maternal pregnancy (intrauterine) exposures on offspring outcomes: Sources of bias and methods for assessing them

Mendelian randomization (MR), the use of genetic variants as instrumental variables (IVs) to test causal effects, is increasingly used in aetiological epidemiology. Few of the methodological developments in MR have considered the specific situation of using genetic IVs to test the causal effect of exposures in pregnant women on postnatal offspring outcomes. In this paper, we describe specific ways in which the IV assumptions might be violated when MR is used to test such intrauterine effects. We highlight the importance of considering the extent to which there is overlap between genetic variants in offspring that influence their outcome with genetic variants used as IVs in their mothers. Where there is overlap, and particularly if it generates a strong association of maternal genetic IVs with offspring outcome via the offspring genotype, the exclusion restriction assumption of IV analyses will be violated. We recommend a set of analyses that ought to be considered when MR is used to address research questions concerned with intrauterine effects on post-natal offspring outcomes, and provide details of how these can be undertaken and interpreted. These additional analyses include the use of genetic data from offspring and fathers, examining associations using maternal non-transmitted alleles, and using simulated data in sensitivity analyses (for which we provide code). We explore the extent to which new methods that have been developed for exploring violation of the exclusion restriction assumption in the two-sample setting (MR-Egger and median based methods) might be used when exploring intrauterine effects in one-sample MR. We provide a list of recommendations that researchers should use when applying MR to test the effects of intrauterine exposures on postnatal offspring outcomes and use an illustrative example with real data to demonstrate how our recommendations can be applied and subsequent results appropriately interpreted.

Vitamin D and pre-eclampsia: original data, systematic review and meta-analysis

BACKGROUND/AIMS

Vitamin D may protect from pre-eclampsia through influences on immune modulation and vascular function. To evaluate the role of vitamin D in the development of pre-eclampsia, we conducted a systematic review and meta-analysis including novel data from 2 large-scale epidemiological studies.

METHODS

PubMed, EMBASE and the Cochrane Central Register of Controlled Trials were searched for prospective observational studies of association between vitamin D supplementation or status (measured by maternal 25-hydroxyvitamin D, 25(OH)D) with a subsequent risk of pre-eclampsia, or randomised controlled trials using vitamin D supplementation to prevent pre-eclampsia. The Hungarian Case-Control Surveillance of Congenital Abnormalities (HCCSCA) and the Avon Longitudinal Study of Parents and Children (ALSPAC) were included in meta-analyses with published studies.

RESULTS

Mothers receiving vitamin D supplementation earlier in pregnancy had lower odds of pre-eclampsia [pooled odds ratios (OR) 0.81 and 95% confidence interval (CI) 0.75-0.87, p = 2.4 × 10(-8), 2 studies] in the meta-analysis of published studies with HCCSCA. The meta-analysis of published studies with ALSPAC suggested an association between higher serum 25(OH)D levels and a reduced risk of pre-eclampsia (pooled OR 0.52 and 95% CI 0.30-0.89, p = 0.02, 6 studies). Randomised trials of supplementation were suggestive of protective association (pooled OR 0.66 and 95% CI 0.52-0.83, p = 0.001, 4 studies).

CONCLUSIONS

This study suggests that low maternal serum 25(OH)D concentrations increase pre-eclampsia risk and that vitamin D supplementation lowers this risk. The quality of evidence is insufficient to determine a causal association, which highlights the need for adequately powered clinical trials.