Linear spline multilevel models for summarising childhood growth trajectories: A guide to their application using examples from five birth cohorts

Associations of Maternal Educational Level, Proximity to Green Space 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 multicohort federated analyses by examining associations between 3 pregnancy exposures (maternal education, exposure to green vegetation, and gestational diabetes) and offspring body mass index (BMI) from infancy to age 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 1-stage individual participant data 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, at age 2-3 years = 0.03 (95% confidence interval (CI): 0.00, 0.05), at 4-7 years = 0.16 (95% CI: 0.14, 0.17), and at 8-13 years = 0.24 (95% CI: 0.22, 0.26)). Gestational diabetes was positively associated with BMI from age 8 years (BMI z score difference = 0.18, 95% CI: 0.12, 0.25) but not at younger ages; however, associations attenuated towards the null when restricted to cohorts that measured gestational diabetes via universal screening. Exposure to green vegetation was weakly associated with higher BMI up to age 1 year but not at older ages. Opportunities of cross-cohort federated analyses are discussed.

The onset of mental health disparities in sexual minority and majority youth: evidence from the UK Millennium Cohort Study

Decades of research shows that sexual minority youth (SMY) display heightened risk for mental health problems, although the onset of such disparities remains unclear. The Millennium Cohort Study is the largest nationally representative longitudinal study of adolescents in the United Kingdom. In this study, participants (N = 10,047, 50% female) self-reported their sexual identity at age 17 and had parent-reported mental health data, from the Strengths and Difficulties Questionnaire, reported across five waves at ages 5, 7, 11, 14, and 17. Multilevel linear spline models, stratified by sex, were used to examine mental health trajectories between sexual identity groups (completely heterosexual, mostly heterosexual, SMY). SMY showed heightened peer problems from the baseline assessment at age five, increasing over time, and heightened emotional problems from age 11, increasing over time. Mostly heterosexual youth showed heightened emotional problems at age 11 in males, and at age 17 in females. Findings are discussed in light of the literature on minority stress and gender conformity in youth. The use of parent-reported mental health data means that estimates are likely to be conservative. We conclude that interventions supporting SMY should start early and be available throughout adolescence.

Prevalence, Incidence, and Reversal Pattern of Childhood Stunting From Birth to Age 2 Years in Ethiopia

Importance

Although there has been a reduction in stunting (low-height-for-age and low-length-for-age), a proxy of malnutrition, the prevalence of malnutrition in Ethiopia is still high. Child growth patterns and estimates of stunting are needed to increase awareness and resources to improve the potential for recovery.

Objective

To estimate the prevalence, incidence, and reversal of stunting among children aged 0 to 24 months.

Design, Setting, and Participants

This population-based cohort study of the Birhan Maternal and Child Health cohort in North Shewa Zone, Amhara, Ethiopia, was conducted between December 2018 and November 2020. Eligible participants included children aged 0 to 24 months who were enrolled during the study period and had their length measured at least once. Data analysis occurred from Month Year to Month Year.

Main Outcomes and Measures

The primary outcome of this study was stunting, defined as length-for-age z score (LAZ) at least 2 SDs below the mean. Z scores were also used to determine the prevalence, incidence, and reversal of stunting at each key time point. Growth velocity was determined in centimeters per month between key time points and compared with global World Health Organization (WHO) standards for the same time periods. Heterogeneity was addressed by excluding outliers in sensitivity analyses using modeled growth trajectories for each child.

Results

A total of 4354 children were enrolled, out of which 3674 (84.4%; 1786 [48.7%] female) had their length measured at least once and were included in this study. The median population-level length was consistently below WHO growth standards from birth to 2 years of age. The observed prevalence of stunting was highest by 2 years of age at 57.4% (95% CI, 54.8%-9 60.0%). Incidence of stunting increased over time and reached 51.0% (95% CI, 45.3%-56.6%) between ages 12 and 24 months. Reversal was 63.5% (95% CI, 54.8%-71.4%) by age 6 months and 45.2% (95% CI, 36.0%-54.8%) by age 2 years. Growth velocity point estimate differences were slowest compared with WHO standards during the neonatal period (-1.4 cm/month for girls and -1.6 cm/month for boys). There was substantial heterogeneity in anthropometric measurements.

Conclusions and Relevance

The evidence from this cohort study highlights a chronically malnourished population with much of the burden associated with growth faltering during the neonatal periods as well as after 6 months of age. To end all forms of malnutrition, growth faltering in populations such as that in young children in Amhara, Ethiopia, needs to be addressed.

Association of linear growth velocities between 0 and 6 years with kidney function and size at 10 years: A birth cohort study in Ethiopia

BACKGROUND

Risk of noncommunicable diseases accrues from fetal life, with early childhood growth having an important role in adult disease risk. There is a need to understand how early-life growth relates to kidney function and size.

OBJECTIVES

This study aimed to assess the association of linear growth velocities among children between 0 and 6 y with kidney function and size among children aged 10 y.

METHODS

The Ethiopian Anthropometric and Body Composition birth cohort recruited infants born at term to mothers living in Jimma with a birth weight of ≥1500 g and without congenital malformations. Participants were followed up with 13 measurements between birth and 6 y of age. The latest follow-up was at ages 7-12 y with measurement of serum cystatin C as a marker of kidney function and ultrasound assessment of kidney dimensions. Kidney volume was computed using an ellipsoid formula. Linear-spline multilevel modeling was used to compute linear growth velocities between 0 and 6 y. Multiple linear regression modeling was used to examine the associations of linear growth velocities in selected age periods with cystatin C and kidney size.

RESULTS

Data were captured from 355 children, at a mean age of 10 (range 7-12) y. The linear growth velocity was high between 0 and 3 mo and then decreased with age. There was no evidence of an association of growth velocity ≤24 mo with cystatin C at 10 y. Between 24 and 48 and 48 and 76 mo, serum cystatin C was higher by 2.3% [95% confidence interval (CI): 0.6, 4.2] and 2.1% (95% CI: 0.3, 4.0) for 1 SD higher linear growth velocity, respectively. We found a positive association between linear growth velocities at all intervals between 0 and 6 y and kidney volume.

CONCLUSIONS

Greater linear growth between 0 and 6 y of development was positively associated with kidney size, and greater growth velocity after 2 y was associated with higher serum cystatin C concentrations.

Association between maternal blood lipids during pregnancy and offspring growth trajectories in a predominantly macrosomic cohort: findings from the ROLO longitudinal birth cohort study

The purpose of this study is to examine associations between maternal lipid profiles in pregnancy and offspring growth trajectories in a largely macrosomic cohort. This is a secondary analysis of the ROLO birth cohort (n = 293), which took place in the National Maternity Hospital, Dublin, Ireland. Infants were mostly macrosomic, with 55% having a birthweight > 4 kg. Maternal mean age was 32.4 years (SD 3.9 years), mean BMI was 26.1 kg/m2 (SD 4.4 kg/m2) and 48% of children born were males. Total cholesterol, high density lipoprotein cholesterol (HDL-cholesterol), low density lipoprotein cholesterol (LDL-cholesterol) and triglycerides were measured from fasting blood samples of mothers at 14 and 28 week gestation. The change in maternal lipid levels from early to late pregnancy was also examined. Offspring abdominal circumference and weight were measured at 20- and 34-week gestation, birth, 6 months, 2 years and 5 years postnatal. Linear spline multilevel models examined associations between maternal blood lipid profiles and offspring growth. We found some weak, significant associations between maternal blood lipids and trajectories of offspring growth. Significant findings were close to the null, providing limited evidence. For instance, 1 mmol/L increase in maternal triglycerides was associated with faster infant weight growth from 20- to 34-week gestation (0.01 kg/week, 95% CI - 0.02, - 0.001) and slower abdominal circumference from 2 to 5 years (0.01 cm/week, 95% CI - 0.02, - 0.001). These findings do not provide evidence of a clinically meaningful effect.    Conclusion: These findings raise questions about the efficacy of interventions targeting maternal blood lipid profiles in pregnancies at risk of macrosomia. New studies on this topic are needed. What is Known: • Maternal fat accumulation during early pregnancy may potentially support fetal growth in the third trimester by providing a reserve of lipids that are broken down and transferred to the infant across the placental barrier. • There are limited studies exploring the impact of maternal lipid profiles on infant and child health using growth trajectories spanning prenatal to postnatal life. What is New: • Maternal blood lipid profiles were not associated with offspring growth trajectories of weight and abdominal circumference during pregnancy up to 5 years of age in a largely macrosomic cohort, as significant findings were close to the null, providing limited evidence for a clinically meaningful relationship. • Strengths of this work include the use of infant growth trajectories that span prenatal to postnatal life and inclusion of analyses of the change of maternal lipid levels from early to late pregnancy and their associations with offspring growth trajectories from 20-week gestation to 5 years of age.

Childhood socioeconomic position and sex-specific trajectories of metabolic traits across early life: prospective cohort study

BACKGROUND

Socioeconomic inequalities in cardiovascular disease risk begin early in life and are more pronounced in females than males later in life. Causal atherogenic traits explaining this are not well understood. We explored sex-specific associations between childhood socioeconomic position (SEP) and molecular measures of systemic metabolism across early life.

METHODS

Data were from the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort in southwest England. Pregnant women with an expected delivery date between 1991 and 1992 were invited to participate. Maternal education was the primary indicator of SEP. Concentrations of 148 metabolic traits from targeted metabolomics (nuclear magnetic resonance spectroscopy) from research clinics at ages 7, 15, 18 and 25 years were analysed. The sex-specific slope index of inequality (SII) in trajectories of metabolic traits was estimated using multilevel models.

FINDINGS

Total number of participants included was 6537 (12,543 repeated measures). Lower maternal education was associated with more adverse levels of several atherogenic lipids and key metabolic traits among females at age 7 years, but not males. For instance, SII for very small very-low-density lipoprotein (VLDL) concentrations was 0.16SD (95% CI: 0.01, 0.30) among females and -0.02SD (95% CI: -0.16, 0.13) among males. Between 7 and 25 years, inequalities widened among females and emerged among males particularly for VLDL particle concentrations, apolipoprotein-B concentrations, and inflammatory glycoprotein acetyls. For instance, at 25 years, SII for very small VLDL concentrations was 0.36SD (95% CI: 0.20, 0.52) and 0.22SD (95% CI: 0.04, 0.40) among females and males respectively.

INTERPRETATION

Prevention of socioeconomic inequalities in cardiovascular disease risk requires a life course approach beginning at the earliest opportunity, especially among females.

FUNDING

The UK Medical Research Council and Wellcome (grant ref: 217065/Z/19/Z) and the University of Bristol provide core support for ALSPAC. A comprehensive list of grants funding is available on the ALSPAC website (http://www.bristol.ac.uk/alspac/external/documents/grant-acknowledgements.pdf). KON is supported by a Health Research Board (HRB) of Ireland Investigator Led Award (ILP-PHR-2022-008). JB, GDS and KT work in a unit funded by the UK MRC (MC_UU_00011/1 and MC UU 00011/3) and the University of Bristol. OR is supported by a UKRI Future Leaders Fellowship (MR/S03532X/1). These funding sources had no role in the design and conduct of this study. This publication is the work of the authors and KON will serve as guarantor for the contents of this paper.

Associations between maternal gestational diabetes metformin or insulin treatment and offspring growth trajectories from birth to 60 months of age: Findings from the Born in Bradford (BiB) study

AIM

To investigate the associations between gestational diabetes mellitus (GDM) metformin or insulin treatment and offspring growth trajectories from 0 to 60 months.

METHODS

Participants were from the Born in Bradford birth cohort study. Using covariate-adjusted multilevel linear spline models (4 splines: 0-1.6, 1.6-6, 6-17 and 17-60 months), we compared weight, height and body mass index (BMI) z-score trajectories of: (1) 76 offspring exposed to metformin (OGDM-Metformin) and 420 offspring exposed to insulin (OGDM-Insulin); (2) OGDM-Metformin and 9171 offspring not exposed to GDM (No-GDM); (3) OGDM-Insulin and No-GDM.

RESULTS

(1) OGDM-Metformin had comparable growth trajectories to OGDM-Insulin from 0 to 60 months. (2) OGDM-Metformin had a lower mean birthweight z-score than No-GDM. OGDM-Metformin had faster changes in height z-score (0.13 [95% CI 0.026, 0.24]) from 17 to 60 months and by 60 months, had comparable mean BMI z-score to No-GDM. (3) OGDM-insulin had lower mean birthweight and height z-scores than No-GDM. OGDM-Insulin had faster changes in weight (0.32 [0.021, 0.62]) and height (0.50 [0.087, 0.91]) from 1.6 to 6 months and by 60 months, had comparable mean BMI z-score to No-GDM.

CONCLUSIONS

GDM metformin treatment was not associated with differences in offspring growth trajectories compared to insulin treatment. Both metformin and insulin-exposed offspring had comparable BMI z-score to No-GDM by 60 months.

The relationship between timing of onset of menarche and depressive symptoms from adolescence to adulthood

AIMS

Girls who experience an earlier onset of menarche than their peers are at increased risk of depressive symptoms in mid-adolescence, but it is unclear if this association persists into adulthood. This study examines whether longitudinal patterns of depressive symptoms from adolescence to adulthood vary according to timing of menarche.

METHODS

About 4,864 female participants in the UK Avon Longitudinal Study of Parents and Children provided data on age at onset of menarche (assessed in repeated questionnaires from 8 to 17 years) and depressive symptoms across nine time points (13 to 26 years) using the Short Mood and Feelings Questionnaire. We compared patterns of depressive symptoms in girls with 'early' (<11.5 years), 'normative' (11.5 to 13.5 years) and 'late' (≥13.5 years) menarche using a linear spline multilevel growth curve model adjusted for indicators of socioeconomic position, father absence and body mass index.

RESULTS

Early, compared with normative, menarche was associated with higher levels of depressive symptoms at age 14 (imputed adjusted estimated difference = 0.94, 95% confidence interval [CI] = 0.44, 1.45), but the association attenuated at 24 years (0.24 [-0.72, 1.19]). Late menarche, compared with normative, was associated with a lower level of depressive symptoms at age 14 (-0.69 [-1.10, -0.29]), but this association also attenuated at 24 years (-0.15 [-0.92, 0.62]).

CONCLUSIONS

This study did not find a persistent effect of early menarche, compared to normative, on depressive symptoms. However, our findings are consistent with the level of depressive symptoms increasing at the onset of menarche irrespective of timing. The late onset girls 'catch up' with their peers who experience menarche earlier in terms of depressive symptoms. Future studies should continue to assess the impact of timing of menarche further into adulthood.

Late preterm birth and growth trajectories during childhood: a linked retrospective cohort study

BACKGROUND

Evidence suggests that accelerated postnatal growth in children is detrimental for adult cardiovascular health. It is unclear whether children born late preterm (34-36 weeks) compared to full term (≥ 39 weeks), have different growth trajectories. Our objective was to evaluate the association between gestational age groups and growth trajectories of children born between 2006-2014 and followed to 2021 in Ontario, Canada.

METHODS

We conducted a retrospective cohort study of children from singleton births in TARGet Kids! primary care network with repeated measures of weight and height/length from birth to 14 years, who were linked to health administrative databases. Piecewise linear mixed models were used to model weight (kg/month) and height (cm/month) trajectories with knots at 3, 12, and 84 months. Analyses were conducted based on chronological age.

RESULTS

There were 4423 children included with a mean of 11 weight and height measures per child. The mean age at the last visit was 5.9 years (Standard Deviation: 3.1). Generally, the more preterm, the lower the mean value of weight and height until early adolescence. Differences in mean weight and height for very/moderate preterm and late preterm compared to full term were evident until 12 months of age. Weight trajectories were similar between children born late preterm and full term with small differences from 84-168 months (mean difference (MD) -0.04 kg/month, 95% CI -0.06, -0.03). Children born late preterm had faster height gain from 0-3 months (MD 0.70 cm/month, 95% CI 0.42, 0.97) and 3-12 months (MD 0.17 cm/month, 95% CI 0.11, 0.22).

CONCLUSIONS

Compared to full term, children born late preterm had lower average weight and height from birth to 14 years, had a slightly slower rate of weight gain after 84 months and a faster rate of height gain from 0-12 months. Follow-up is needed to determine if growth differences are associated with long-term disease risk.

Prenatal ambient air pollution exposure and child weight trajectories from the 3rd trimester of pregnancy to 2 years of age: a cohort study

BACKGROUND

Prenatal air pollution exposure may increase risk for childhood obesity. However, few studies have evaluated in utero growth measures and infant weight trajectories. This study will evaluate the associations of prenatal exposure to ambient air pollutants with weight trajectories from the 3rd trimester through age 2 years.

METHODS

We studied 490 pregnant women who were recruited from the Maternal and Development Risks from Environmental and Social Stressors (MADRES) cohort, which comprises a low-income, primarily Hispanic population in Los Angeles, California. Nitrogen dioxide (NO2), particulate matter < 10 µm (PM10), particulate matter < 2.5 µm (PM2.5), and ozone (O3) concentrations during pregnancy were estimated from regulatory air monitoring stations. Fetal weight was estimated from maternal ultrasound records. Infant/child weight measurements were extracted from medical records or measured during follow-up visits. Piecewise spline models were used to assess the effect of air pollutants on weight, overall growth, and growth during each period.

RESULTS

The mean (SD) prenatal exposure concentrations for NO2, PM2.5, PM10, and O3 were 16.4 (2.9) ppb, 12.0 (1.1) μg/m3, 28.5 (4.7) μg/m3, and 26.2 (2.9) ppb, respectively. Comparing an increase in prenatal average air pollutants from the 10th to the 90th percentile, the growth rate from the 3rd trimester to age 3 months was significantly increased (1.55% [95%CI 1.20%, 1.99%] for PM2.5 and 1.64% [95%CI 1.27%, 2.13%] for NO2), the growth rate from age 6 months to age 2 years was significantly decreased (0.90% [95%CI 0.82%, 1.00%] for NO2), and the attained weight at age 2 years was significantly lower (- 7.50% [95% CI - 13.57%, - 1.02%] for PM10 and - 7.00% [95% CI - 11.86%, - 1.88%] for NO2).

CONCLUSIONS

Prenatal ambient air pollution was associated with variable changes in growth rate and attained weight from the 3rd trimester to age 2 years. These results suggest continued public health benefits of reducing ambient air pollution levels, particularly in marginalized populations.

A modified Michaelis-Menten equation estimates growth from birth to 3 years in healthy babies in the US

Background and Objectives

Standard pediatric growth curves cannot be used to impute missing height or weight measurements in individual children. The Michaelis-Menten equation, used for characterizing substrate-enzyme saturation curves, has been shown to model growth in many organisms including nonhuman vertebrates. We investigated this equation could be used to interpolate missing growth data in children in the first three years of life.

Methods

We developed a modified Michaelis-Menten equation and compared expected to actual growth, first in a local birth cohort (N=97) then in a large, outpatient, pediatric sample (N=14,695).

Results

The modified Michaelis-Menten equation showed excellent fit for both infant weight (median RMSE: boys: 0.22kg [IQR:0.19; 90%<0.43]; girls: 0.20kg [IQR:0.17; 90%<0.39]) and height (median RMSE: boys: 0.93cm [IQR:0.53; 90%<1.0]; girls: 0.91cm [IQR:0.50;90%<1.0]). Growth data were modeled accurately with as few as four values from routine well-baby visits in year 1 and seven values in years 1-3; birth weight or length was essential for best fit.

Conclusions

A modified Michaelis-Menten equation accurately describes growth in healthy babies aged 0-36 months, allowing interpolation of missing weight and height values in individual longitudinal measurement series. The growth pattern in healthy babies in resource-rich environments mirrors an enzymatic saturation curve.

A modified Michaelis-Menten equation estimates growth from birth to 3 years in healthy babies in the US

Background and Objectives

Standard pediatric growth curves cannot be used to impute missing height or weight measurements in individual children. The Michaelis-Menten equation, used for characterizing substrate-enzyme saturation curves, has been shown to model growth in many organisms including nonhuman vertebrates. We investigated this equation could be used to interpolate missing growth data in children in the first three years of life.

Methods

We developed a modified Michaelis-Menten equation and compared expected to actual growth, first in a local birth cohort (N=97) then in a large, outpatient, pediatric sample (N=14,695).

Results

The modified Michaelis-Menten equation showed excellent fit for both infant weight (median RMSE: boys: 0.22kg [IQR:0.19; 90%<0.43]; girls: 0.20kg [IQR:0.17; 90%<0.39]) and height (median RMSE: boys: 0.93cm [IQR:0.53; 90%<1.0]; girls: 0.91cm [IQR:0.50;90%<1.0]). Growth data were modeled accurately with as few as four values from routine well-baby visits in year 1 and seven values in years 1-3; birth weight or length was essential for best fit.

Conclusions

A modified Michaelis-Menten equation accurately describes growth in healthy babies aged 0-36 months, allowing interpolation of missing weight and height values in individual longitudinal measurement series. The growth pattern in healthy babies in resource-rich environments mirrors an enzymatic saturation curve.

Sex-specific trajectories of molecular cardiometabolic traits from childhood to young adulthood

BACKGROUND

The changes which typically occur in molecular causal risk factors and predictive biomarkers for cardiometabolic diseases across early life are not well characterised.

METHODS

We quantified sex-specific trajectories of 148 metabolic trait concentrations including various lipoprotein subclasses from age 7 years to 25 years. Data were from 7065 to 7626 offspring (11 702 to14 797 repeated measures) of the Avon Longitudinal Study of Parents and Children birth cohort study. Outcomes were quantified using nuclear magnetic resonance spectroscopy at 7, 15, 18 and 25 years. Sex-specific trajectories of each trait were modelled using linear spline multilevel models.

RESULTS

Females had higher very-low-density lipoprotein (VLDL) particle concentrations at 7 years. VLDL particle concentrations decreased from 7 years to 25 years with larger decreases in females, leading to lower VLDL particle concentrations at 25 years in females. For example, females had a 0.25 SD (95% CI 0.20 to 0.31) higher small VLDL particle concentration at 7 years; mean levels decreased by 0.06 SDs (95% CI -0.01 to 0.13) in males and 0.85 SDs (95% CI 0.79 to 0.90) in females from 7 years to 25 years, leading to 0.42 SDs (95% CI 0.35 to 0.48) lower small VLDL particle concentrations in females at 25 years. Females had lower high-density lipoprotein (HDL) particle concentrations at 7 years. HDL particle concentrations increased from 7 years to 25 years with larger increases among females leading to higher HDL particle concentrations in females at 25 years.

CONCLUSION

Childhood and adolescence are important periods for the emergence of sex differences in atherogenic lipids and predictive biomarkers for cardiometabolic disease, mostly to the detriment of males.

Mitochondrial DNA haplogroups and trajectories of cardiometabolic risk factors during childhood and adolescence: A prospective cohort study

BACKGROUND

Mitochondria are organelles responsible for converting glucose into energy. Mitochondrial DNA is exclusively maternally inherited. The role of mitochondrial DNA haplogroups in the aetiology of cardiometabolic disease risk is not well understood.

METHODS

Sex-specific associations between common European mitochondrial DNA haplogroups (H, U, J, T, K, V, W, I and X) and trajectories of cardiometabolic risk factors from birth to 18 years were examined in a prospective cohort. Cardiometabolic risk factors measured from birth/mid-childhood to 18 years included body mass index (BMI), fat and lean mass, systolic and diastolic blood pressure, pulse rate, high-density lipoprotein cholesterol (HDL-c), non-HDL-c and triglycerides. Fractional polynomial and linear spline multilevel models explored the sex-specific association between haplogroups and risk factor trajectories.

RESULTS

Among a total of 7,954 participants with 79,178 repeated measures per outcome, we found no evidence that haplogroups U, T, J, K and W were associated with cardiometabolic risk factors compared to haplogroup H. In females, haplogroup V was associated with 4.0% (99% CI: -7.5, -0.6) lower BMI at age one but associations did not persist at age 18. Haplogroup X was associated with 1.3kg (99% CI: -2.5, -0.2) lower lean mass at age 9 which persisted at 18. Haplogroup V and X were associated with 9.3% (99% CI: -0.4, 19.0) and 16.4% (99% CI: -0.5,33.3) lower fat mass at age 9, respectively, although confidence intervals spanned the null and associations did not persist at 18. In males, haplogroup I was associated with 2.4% (99% CI: -0.5, 5.3) higher BMI at age 7; widening to 5.1% (99% CI: -0.5, 10.6) at 18 with confidence intervals spanning the null.

CONCLUSIONS

Our study demonstrated little evidence of sex-specific associations between mitochondrial DNA haplogroups and cardiometabolic risk factors.

Maternal BMI in the preconception period, and association with child zBMI growth rates

BACKGROUND

Elevated body mass index (BMI) and rapid growth in early childhood are important predictors of obesity risk. The association between maternal preconception BMI and child growth rates is unclear.

OBJECTIVES

To assess the association between measured maternal preconception BMI and child age- and sex- standardized WHO BMI z-score (zBMI) growth rates and mean zBMI, in children aged 0-10 years old.

METHODS

A longitudinal cohort study was conducted with children (n = 499) enrolled in The Applied Research Group for Kids (TARGet Kids!) primary care practice-based research cohort. Maternal BMI was measured during the preconception period, defined as the 2 years prior to pregnancy. Repeated measures of child weight and height were obtained between 0 and 10 years of age. Linear mixed models were used to evaluate the association between maternal BMI and child zBMI growth rates and mean zBMI.

RESULTS

Maternal preconception BMI was associated with child zBMI growth rate during some growth periods, with the strongest association from age 0 to 4 months; a 5 kg/m2 higher maternal BMI was associated with 0.031 zBMI SD unit/mo higher growth rate (p = 0.004), and 0.186 SD unit higher mean child zBMI (p = 0.0002).

CONCLUSIONS

Maternal preconception BMI was associated with growth rate and mean zBMI in early childhood. The preconception period may be an important target for health interventions to promote healthy child growth rate and weight outcomes.

Application of multilevel linear spline models for analysis of growth trajectories in a cohort with repeat antenatal and postnatal measures of growth: a prospective cohort study

OBJECTIVES

To model trajectories of antenatal and postnatal growth using linear spline multilevel models.

DESIGN

Prospective cohort study.

SETTING

Maternity hospital in Dublin, Ireland.

PARTICIPANTS

720-759 mother-child pairs from the ROLO study (initially a randomised control trial of a low glycaemic index diet in pregnancy to prevent recurrence of macrosomia [birth weight >4 kg]).

PRIMARY OUTCOMES

Trajectories of growth from 20 weeks gestation (abdominal circumference [AC], head circumference [HC] and weight) or birth (length/height) to 5 years.

RESULTS

Over 50% of women had third-level education and 90% were of white ethnicity. Women were a mean (SD) age of 32 years (4.2) at recruitment. The best fitting model for AC, HC and weight included a model with 5 linear spline periods. The best fitting models for length/height included a model with 3 linear spline periods from birth to 6 months, 6 months to 2 years and 2 years to 5 years. Comparison of observed and predicted values for each model demonstrated good model fit. For all growth measures, growth rates were generally fastest in pregnancy or immediately post partum (for length/height), with rates of growth slowing after birth and becoming slower still as infancy and childhood progressed.

CONCLUSION

We demonstrate the application of multilevel linear spline models for examining growth trajectories when both antenatal and postnatal measures of growth are available. The approach may be useful for cohort studies or randomised control trials with repeat prospective assessments of growth.

Tax on sugary drinks and trends in daily soda consumption by family affluence: an international repeated cross-sectional survey among European adolescents

BACKGROUND

The WHO recommends soda taxes to reduce sugar consumption, but the effect across socioeconomic groups is unclear.

OBJECTIVES

We assessed 16-y trends in daily soda consumption among adolescents in 4 European countries with a soda tax and 5 comparison countries, by family affluence.

METHODS

Five rounds of the international "Health Behaviour in School-Aged Children" school-based survey were used (school years 2001/2002 to 2017/2018, repeated cross-sectional design). Finland, France, Belgium, and Portugal introduced or updated a soda tax during this period. For comparison, we selected 5 neighboring countries without such a tax. Nationally representative samples of adolescents aged 13 and 15 y (n = 165,521; 51.2% girls) completed a standardized questionnaire, including a question on soda consumption frequency. Using the family affluence scale (FAS), we categorized adolescents into lower-, middle- or higher-affluent groups. Changes in daily soda consumption were assessed in each country independently.

RESULTS

Before taxation, daily soda consumption was more likely among lower-affluent adolescents in France and Belgium (P < 0.001, socioeconomic inequalities) and was similar across FAS groups in Finland and Portugal (no inequalities). After the tax, daily soda consumption was reduced across all FAS groups in Finland, Belgium, and Portugal (P_interactions ≥ 0.33). In France, a posttax decrease was observed only among lower-affluent adolescents (OR_lower, 0.76; 95% CI: 0.60, 0.96; reduced inequalities). During the same periods, socioeconomic patterns remained stable in 3 comparison countries (P_interactions ≥ 0.38), and larger reductions in daily soda consumption were observed among middle- or higher-affluent adolescents compared with lower-affluent adolescents in the remaining 2 comparison countries (P_interactions ≤ 0.08, increased inequalities).

CONCLUSIONS

Socioeconomic patterns did not change after the tax implementation in 3 out of 4 countries, and socioeconomic inequalities were reduced in France. Taxing sodas might be an effective measure to attenuate, or at least not exacerbate, socioeconomic inequalities in adolescent daily soda consumption. Am J Clin Nutr 20XX;xx:xx-xx.

Gestational age and trajectories of body mass index and height from birth through adolescence in the Danish National Birth Cohort

Preterm birth is associated with smaller body dimensions at birth. The impact on body size in later life, measured by body mass index (BMI) and height, remains unclear. A prospective register-based cohort study with 62,625 singletons from the Danish National Birth Cohort born 1996-2003 for whom information on gestational age (GA) at birth, length or weight at birth, and at least two growth measurements scheduled at the ages of 5 and 12 months, and 7, 11 and 18 years were available. Linear mixed effects with splines, stratified by sex, and adjusted for confounders were used to estimate standardised BMI and height. GA was positively associated with BMI in infancy, but differences between preterm and term children declined with age. By age 7, preterm children had slightly lower BMI than term children, whereas no difference was observed by adolescence (mean difference in BMI z-score - 0.28 to 0.15). GA was strongly associated with height in infancy, but mean differences between individuals born preterm and term declined during childhood. By adolescence, the most preterm individuals remained shorter than their term peers (mean difference in height z-score from - 1.00 to - 0.28). The lower BMI in preterm infants relative to term infants equalizes during childhood, such that by adolescence there is no clear difference. Height is strongly positively associated with GA in early childhood, whilst by end of adolescence individuals born preterm remain slightly shorter than term peers.

Paternal BMI in the preconception period, and the association with child zBMI

BACKGROUND

Rapid growth and excess weight in early childhood are associated with obesity risk. While maternal preconception BMI has been identified as a potential risk factor, the role of paternal preconception BMI is less clear.

OBJECTIVES

To examine the association between paternal preconception BMI and age- and sex-standardized WHO BMI z-score (zBMI) growth rates, zBMI, and weight status, in 0- to 10-year-old children. To determine whether these associations differed by child sex and maternal preconception weight status.

METHODS

A longitudinal cohort study was conducted through The Applied Research Group for Kids (TARGet Kids!). Children (n = 218) underwent repeated measures of height and weight from birth to 10 years old. Piecewise linear mixed models were used to assess the association between paternal preconception BMI and child zBMI growth rates (zBMI SD units/month) between 0, 4, 30, 48 and 120 months of age. Linear mixed models were used to examine the association with child zBMI, and logistic generalized estimation equations (GEE) were used to assess the association with child weight status. Child sex and maternal preconception weight status were tested as effect modifiers.

RESULTS

Paternal preconception BMI was associated with child zBMI growth rate, mean zBMI and weight status in boys, but not girls. A 5 kg/m² higher paternal preconception BMI was associated with approximately 0.01 zBMI SD unit/month higher growth rate for boys born to mothers with preconception overweight. Higher paternal BMI was associated with higher mean zBMI and increased odds of overweight and obesity in boys, with greater effects seen when mothers had preconception overweight compared to normal weight.

CONCLUSION

Paternal preconception BMI was associated with child zBMI growth rate, zBMI and weight status in boys, with greater effects when the biological mother had preconception overweight or obesity. Further understanding of sex differences in paternal preconception weight effects in children is needed.

Associations between maternal metabolic parameters during pregnancy and fetal and child growth trajectories from 20 weeks' gestation to 5 years of age: Secondary analysis from the ROLO longitudinal birth cohort study

OBJECTIVE

To examine the association between maternal metabolic parameters in pregnancy and growth trajectories up to 5 years of age.

METHODS

Data from mother-child pairs who participated in the ROLO study, a randomized trial examining the impact of a low glycaemic index diet on the recurrence of macrosomia, were analysed. Fetal and child growth trajectories were developed from longitudinal measurements from 20 weeks gestation up to 5 years of age. We examined associations between maternal fasting glucose, insulin, HOMA-IR and leptin, taken in early pregnancy (14-16 weeks) and late pregnancy (28 weeks), and weight (kg) and abdominal circumference (cm) trajectories using linear spline multilevel models.

RESULTS

We found no strong evidence of associations between any maternal metabolic parameters and fetal to childhood weight and abdominal circumference trajectories from 20 weeks gestation to 5 years.

CONCLUSION

In a cohort of women with obesity with infants at risk of macrosomia, maternal metabolic markers were not strongly associated with trajectories of weight or abdominal circumference from 20 weeks gestation to 5 years of age.

Lactose-reduced infant formula with corn syrup solids and obesity risk among participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)

BACKGROUND

The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), a federal nutrition assistance program supporting low-income families, serves half of United States-born infants, most of whom are issued infant formula by age 2 mo. Obesity prevalence is high among children of low-income households, particularly formula-fed children.

OBJECTIVES

This study was conducted to determine whether glucose-based lactose-reduced infant formula made with corn syrup solids (CSSF) is associated with increased obesity risk compared with non-CSSFs that are lactose based.

DESIGN

WIC administrative data on infant formula issuance and child weights and lengths were collected prospectively in Southern California between 2012 and 2020. Included children stopped breastfeeding by 3 mo, were issued cow's milk-based formula through 12 mo, and were enrolled through the final year of WIC eligibility at age 4 y ( n = 15,246). CSSF issuance was assessed continuously (range 0-13 mo) and dichotomously (any, none). Poisson and linear risk regression with robust SE estimates generated risk ratios (RRs), risk differences, and CIs for child obesity [BMI for age (in kg/m 2) ≥95th percentile].

RESULTS

Any CSSF was issued to 23% of children, and 25% were obese at age 4 y. Children with any CSSF issuance had 10% higher obesity risk (RR: 1.10; 95% CI: 1.02, 1.20) than children with no CSSF issuance at age 2 y. Associations remained significant through age 4 y (RR: 1.07; 95% CI: 1.01,1.14), independent of maternal weight status, total formula issued and breastfeeding duration, and were not modified by child race or sex. Obesity risk increased with additional mo of CSSF exposure, reaching 16% higher risk (RR: 1.16; 95% CI: 1.05, 1.28) at age 2 y for children with 12 mo of CSSF.

CONCLUSIONS

CSSF issuance is associated with increased obesity risk in the first 5 y life in a dose dependent manner, independently of maternal weight status, breastfeeding duration, and total formula issuance.

Association of growth patterns during infancy and puberty with lung function, wheezing and asthma in adolescents aged 17.5 years: evidence from ‘Children of 1997’ Hong Kong Chinese Birth Cohort

Background

Rapid growth is related to adverse respiratory outcomes although possibly confounded or limited by growth modelling methods. We investigated the association of infant and pubertal growth with lung function, wheezing and asthma in a non-Western setting.

Methods

In Hong Kong’s ‘Children of 1997’ Chinese birth cohort (n = 8327), weight during infancy and weight, height and body mass index (BMI) during puberty were modelled using a super-imposition by translation and rotation model to identify (larger or smaller) size, (earlier or later) tempo and (slower or faster) velocity. Sex-specific associations with forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), FEV1/FVC (Global Lung function Initiative z-score) and self-reported wheezing and asthma at ∼17.5 years were assessed.

Results

For each fraction higher than average weight growth velocity during infancy, FVC was higher in boys (0.90 SD, 95% CI 0.35; 1.44) and girls (0.77 SD, 95% CI 0.24; 1.30), FEV1/FVC was lower (–0.74 SD, 95% CI –1.38; –0.10) and wheezing was higher (odds ratio 6.92, 95% CI 1.60; 29.99) in boys and an inverse association with FVC was observed for tempo but not for size. Associations for weight growth velocity in puberty were similar but weaker. Greater size and higher velocity of BMI growth was associated with higher FVC, lower FEV1/FVC and higher asthma and wheezing risk.

Conclusion

Accelerated infant and pubertal weight growth were associated with disproportionate lung size and airway growth, and higher risk of asthma; optimizing early-life growth patterns could be important.

Puberty Timing and Sex-Specific Trajectories of Systolic Blood Pressure: a Prospective Cohort Study

BACKGROUND

Sex differences in systolic blood pressure (SBP) emerge during adolescence but the role of puberty is not well understood. We examined sex-specific changes in SBP preceding and following puberty and examined the impact of puberty timing on SBP trajectories in females and males.

METHODS

Trajectories of SBP before and after puberty and by timing of puberty in females and males in a contemporary birth cohort study were analyzed. Repeated measures of height from age 5 to 20 years were used to identify puberty timing (age at peak height velocity). SBP was measured on ten occasions from 3 to 24 years (N participants, 4062; repeated SBP measures, 29 172). Analyses were performed using linear spline multilevel models based on time before and after puberty and were adjusted for parental factors and early childhood factors.

RESULTS

Mean age at peak height velocity was 11.7 years (SD, 0.8) for females and 13.6 years (SD, 0.9) for males. Males had faster rates of increase in SBP before puberty leading to 10.19 mm Hg (95% CI, 6.80-13.57) higher mean SBP at puberty which remained similar at 24 years (mean difference, 11.43 mm Hg [95% CI, 7.22-15.63]). Puberty timing was associated with small transient differences in SBP trajectories postpuberty in both sexes and small differences at 24 years in females only.

CONCLUSIONS

A large proportion of the higher SBP observed in males compared with females in early adulthood is accrued before puberty. Interventions targeting puberty timing are unlikely to influence SBP in early adulthood.

The role of family, school and neighbourhood in Explaining Inequalities in Physical Activity Trajectories between age 9 and 18

Differentials in physical activity (PA) between social and economic groups has been shown to contribute significantly to social gradients in health and life expectancy, yet relatively little is known about why differentials in PA emerge. This paper uses longitudinal data on a nationally representative sample of 6,216 young people aged between 9 and 18, from Ireland, to measure the role of family, school and neighbourhood level factors in accounting for differentials in PA trajectories between groups of young people, defined by level of maternal education, whilst adjusting for the individual characteristics of the young person (sex, age, personality, body mass index and health-status). Levels of PA fall significantly across the sample between 9 and 18, and the decline in PA is larger for the children of lower educated mothers. We find a clear gradient in PA at each age by maternal education for both males and females. Descriptive analyses found social gradients in the majority of our risk factors. Using multi-level, linear spline regression models to decompose differentials between groups, we find that family-level mechanisms account for the biggest proportion of the differential in PA for both males (50.8%) and females (35.1%). Differences in income across maternal education categories accounted for 24.1% of the differential for males and 14.7% among females, making it the second most effective mechanism in explaining the social patterning of PA. Neighbourhood-level processes resulted in a modest reduction in the same differential, while school level processes had the effect of equalising differences in PA across maternal education groups.

•

The potential social determinants of inequalities in physical activity were outlined.

•

The role of family, school and neighbourhood in explaining these inequalities was quantified.

•

The cumulative effect of social environment was observed over a 10-year period.

•

Family-level characteristics were identified as the most effective explanatory mechanism.

•

Highly educated mothers were observed to be enrolling their children in organised sport.

Prenatal Exposure to Insecticides and Weight Trajectories Among South African Children in the VHEMBE Birth Cohort

BACKGROUND

Dichlorodiphenyltrichloroethane (DDT) or pyrethroid insecticides are sprayed inside dwellings for malaria vector control, resulting in high exposure to millions of people, including pregnant women. These chemicals disrupt endocrine function and may affect child growth. To our knowledge, few studies have investigated the potential impact of prenatal exposure to DDT or pyrethroids on growth trajectories.

METHODS

We investigated associations between gestational insecticide exposure and child growth trajectories in the Venda Health Examination of Mothers, Babies and their Environment, a birth cohort of 751 children born between 2012 and 2013 in South Africa. Based on child weight measured at follow-up and abstracted from medical records, we modeled weight trajectories from birth to 5 years using SuperImposition, Translation and Rotation, which estimated two child-specific parameters: size (average weight) and tempo (age at peak weight velocity). We estimated associations between peripartum maternal concentrations of serum DDT, dichlorodiphenyldichloroethylene, or urinary pyrethroid metabolites and SuperImposition, Translation and Rotation parameters using marginal structural models.

RESULTS

We observed that a 10-fold increase in maternal concentrations of the pyrethroid metabolite trans-3-(2,2,-dicholorvinyl)-2,2-dimethyl-cyclopropane carboxylic acid was associated with a 21g (95% confidence interval = -40, -1.6) smaller size among boys but found no association among girls (Pinteraction = 0.07). Estimates suggested that pyrethroids may be associated with earlier tempo but were imprecise. We observed no association with serum DDT or dichlorodiphenyldichloroethylene.

CONCLUSIONS

Inverse associations between pyrethroids and weight trajectory parameters among boys are consistent with hypothesized disruption of androgen pathways and with our previous research in this population, and support the endocrine-disrupting potential of pyrethroids in humans.

The Course of General Cognitive Ability in Individuals With Psychotic Disorders

Importance

Schizophrenia is associated with major cognitive deficits and has been conceptualized as both a neurodevelopmental and a neurodegenerative disorder. However, when deficits develop and how they change over the course of illness is uncertain.

Objective

To trace cognition from elementary school to old age to test neurodevelopmental and neurodegenerative theories of psychotic disorders.

Design, Setting, and Participants

Data were taken from the Suffolk County Mental Health Project, a first-admission longitudinal cohort study of individuals with psychotic disorders. Participants were recruited from all 12 inpatient psychiatric facilities in Suffolk County, New York. This analysis concerns the 428 participants with at least 2 estimates of general cognitive ability. Data were collected between September 1989 and October 2019, and data were analyzed from January 2020 to October 2021.

Exposures

Psychiatric hospitalization for psychosis.

Main Outcomes and Measures

Preadmission cognitive scores were extracted from school and medical records. Postonset cognitive scores were based on neuropsychological testing at 6-month, 24-month, 20-year, and 25-year follow-ups.

Results

Of the 428 included individuals (212 with schizophrenia and 216 with other psychotic disorders), 254 (59.6%) were male, and the mean (SD) age at psychosis onset was 27 (9) years. Three phases of cognitive change were observed: normative, declining, and deteriorating. In the first phase, cognition was stable. Fourteen years before psychosis onset, those with schizophrenia began to experience cognitive decline at a rate of 0.35 intelligence quotient (IQ) points per year (95% CI, 0.29-0.42; P < .001), a significantly faster decline than those with other psychotic disorders (0.15 IQ points per year; 95% CI, 0.08-0.22, P < .001). At 22 years after onset, both groups declined at a rate of 0.59 IQ points per year (95% CI, 0.25-0.94; P < .001).

Conclusions and Relevance

In this cohort study, cognitive trajectories in schizophrenia were consistent with both a neurodevelopmental and neurodegenerative pattern, resulting in a loss of 16 IQ points over the period of observation. Cognitive decline began long prior to psychosis onset, suggesting the window for primary prevention is earlier than previously thought. A window for secondary prevention emerges in the third decade of illness, when cognitive declines accelerate in individuals with schizophrenia and other psychotic disorders.

Decline in attention-deficit hyperactivity disorder traits over the life course in the general population: trajectories across five population birth cohorts spanning ages 3 to 45 years

BACKGROUND

Trajectories of attention-deficit hyperactivity disorder (ADHD) traits spanning early childhood to mid-life have not been described in general populations across different geographical contexts. Population trajectories are crucial to better understanding typical developmental patterns.

METHODS

We combined repeated assessments of ADHD traits from five population-based cohorts, spanning ages 3 to 45 years. We used two measures: (i) the Strengths and Difficulties Questionnaire (SDQ) hyperactive-inattentive subscale (175 831 observations, 29 519 individuals); and (ii) scores from DSM-referenced scales (118 144 observations, 28 685 individuals). Multilevel linear spline models allowed for non-linear change over time and differences between cohorts and raters (parent/teacher/self).

RESULTS

Patterns of age-related change differed by measure, cohort and country: overall, SDQ scores decreased with age, most rapidly declining before age 8 years (-0.157, 95% CI: -0.170, -0.144 per year). The pattern was generally consistent using DSM scores, although with greater between-cohort variation. DSM scores decreased most rapidly between ages 14 and 17 years (-1.32%, 95% CI: -1.471, -1.170 per year). Average scores were consistently lower for females than males (SDQ: -0.818, 95% CI: -0.856, -0.780; DSM: -4.934%, 95% CI: -5.378, -4.489). This sex difference decreased over age for both measures, due to an overall steeper decrease for males.

CONCLUSIONS

ADHD trait scores declined from childhood to mid-life, with marked variation between cohorts. Our results highlight the importance of taking a developmental perspective when considering typical population traits. When interpreting changes in clinical cohorts, it is important to consider the pattern of expected change within the general population, which is influenced by cultural context and measurement.

Infliximab Is Not Associated With a General Long-Term Weight Gain in Patients With Inflammatory Bowel Disease: A Nationwide Study

INTRODUCTION

Patients with Crohn's disease (CD) and ulcerative colitis (UC) may lose weight during periods of active disease and may gain weight when inflammation heals. Studies have hypothesized an association between antitumor necrosis factor-alpha (anti-TNF-α) and unintended weight gain during maintenance therapy, and this association has not been previously clarified.

METHODS

In a nationwide observational study based on Danish national health registries, we included patients who initiated therapy with infliximab and followed changes in weight during induction therapy (0-90 days) and maintenance therapy (91-270 days). The association between the use of infliximab and weight gain was analyzed by a multilevel mixed-effects linear regression model.

RESULTS

Among 851 patients with CD and UC who initiated infliximab therapy, long-term weight gain was not observed during maintenance therapy in most of the patients. Women with CD who were underweight at the initiation of therapy had an average weight gain of 7.5 kg. Men and women with CD and UC with normal or increased body mass index had an average weight gain of <2 kg during maintenance therapy. Underweight men with CD and UC gained 2.9 kg (95% confidence interval 2.1-3.6) and 2.9 kg (95% confidence interval 1.9-3.9), respectively, in the first 90 days, although neither group had statistically significant weight gain in the maintenance period. Less than 3% of the patients had weight gain greater than 10% of their baseline body weight during the study period.

DISCUSSION

Weight gain among patients treated with anti-TNF-α therapies is unlikely to be due to an effect from anti-TNF-α therapy.

Association of Cesarean Delivery with Trajectories of Growth and Body Composition in Preschool Children

This study aimed to examine the association of cesarean delivery with trajectories of growth and body composition in preschool children. This ambidirectional cohort study was conducted between 2017 and 2020 in China. Information on the delivery mode, weight, and length/height of the children measured at routine healthcare visits was obtained from maternal and child health records. For three years while in kindergarten, children’s body mass index (BMI), fat mass index (FMI), fat-free mass index (FFMI), and percentage of body fat (FM%) were repeatedly measured. A BMI z score (zBMI) was calculated and standardized to WHO measures, and overweight and obesity were defined using the WHO reference. After adjustment for maternal age, maternal education, annual family income, prepregnancy BMI, gestational weight gain, gravidity, parity, gestational age, child sex, birthweight, breastfeeding duration, and the parent-reported dietary intake of the children, children born via cesarean delivery (n = 1992) versus those born vaginally (n = 1578) had higher zBMI growth rates beyond 36 months (β: 0.003; 95% CI: 0.001, 0.005 SD units/month) and elevated levels of FMI (β: 0.097; 95% CI: 0.026, 0.168 kg/m²), FM% (β: 0.402; 95% CI: 0.058, 0.745%) and zBMI (β: 0.073; 95% CI: 0.012, 0.133 units), but not FFMI (β: 0.022; 95% CI: −0.022, 0.066 kg/m²). The adjusted OR of overweight and obesity was 1.21 (95% CI: 1.04, 1.40). Cesarean delivery likely elevated zBMI growth rates and increased the risk of overweight and obesity in preschool children, with the elevation of fat mass but not fat-free mass.

Studying latent change process in height growth of children in Ethiopia, India, Peru and Vietnam

BACKGROUND

Anthropometric measurements of healthy children differ in different parts of the world due to the diverse ethnicity and cultural backgrounds of families. In longitudinal studies, appropriate modeling of repeated anthropometric measures can improve the understanding of patterns of change, determinants of patterns, and variations in patterns of change over time. The objective of this study was to examine the latent change in physical height of children in Ethiopia, India, Peru, and Vietnam.

METHOD

Longitudinal data of 6601 children aged 1 to 15 years were obtained from the Young Lives cohort study. The data were analyzed using a latent basis growth curve model.

RESULTS

The findings of the study revealed that the rates of growth did not remain constant across the time intervals, which indicates the nonlinearity of the growth trajectory over time. For instance, children had the highest rate of growth between age 1 and 5 years, then between age 8 and 12 years, and a low rate of growth was observed between age 12 and 15 years. At the first measurement occasion (age 1 year) females were 0.826 cm (p < 0.0001) times shorter than males. The mean height at one year of age ranged from 72.13 cm in Ethiopia to 72.62 cm in India. Children in India and Vietnam had higher mean height at age one year. However, no significant difference in mean height at age one year was found between Ethiopian and Peruvian children, ([Formula: see text]). Peruvian and Vietnamese children grew at a faster rate, while Indian children grew at a slower rate than Ethiopian children.

CONCLUSION

We found substantial latent growth variations among children in four low- and middle-income countries. The latent trajectories differed by gender and country. The outcomes of the study could aid in detecting inequalities in children's height growth.

Using linear and natural cubic splines, SITAR, and latent trajectory models to characterise nonlinear longitudinal growth trajectories in cohort studies

BACKGROUND

Longitudinal data analysis can improve our understanding of the influences on health trajectories across the life-course. There are a variety of statistical models which can be used, and their fitting and interpretation can be complex, particularly where there is a nonlinear trajectory. Our aim was to provide an accessible guide along with applied examples to using four sophisticated modelling procedures for describing nonlinear growth trajectories.

METHODS

This expository paper provides an illustrative guide to summarising nonlinear growth trajectories for repeatedly measured continuous outcomes using (i) linear spline and (ii) natural cubic spline linear mixed-effects (LME) models, (iii) Super Imposition by Translation and Rotation (SITAR) nonlinear mixed effects models, and (iv) latent trajectory models. The underlying model for each approach, their similarities and differences, and their advantages and disadvantages are described. Their application and correct interpretation of their results is illustrated by analysing repeated bone mass measures to characterise bone growth patterns and their sex differences in three cohort studies from the UK, USA, and Canada comprising 8500 individuals and 37,000 measurements from ages 5-40 years. Recommendations for choosing a modelling approach are provided along with a discussion and signposting on further modelling extensions for analysing trajectory exposures and outcomes, and multiple cohorts.

RESULTS

Linear and natural cubic spline LME models and SITAR provided similar summary of the mean bone growth trajectory and growth velocity, and the sex differences in growth patterns. Growth velocity (in grams/year) peaked during adolescence, and peaked earlier in females than males e.g., mean age at peak bone mineral content accrual from multicohort SITAR models was 12.2 years in females and 13.9 years in males. Latent trajectory models (with trajectory shapes estimated using a natural cubic spline) identified up to four subgroups of individuals with distinct trajectories throughout adolescence.

CONCLUSIONS

LME models with linear and natural cubic splines, SITAR, and latent trajectory models are useful for describing nonlinear growth trajectories, and these methods can be adapted for other complex traits. Choice of method depends on the research aims, complexity of the trajectory, and available data. Scripts and synthetic datasets are provided for readers to replicate trajectory modelling and visualisation using the R statistical computing software.

Postnatal exposure to PM2.5 and weight trajectories in early childhood

BACKGROUND

Inconsistent evidence has assessed the impact of air pollution exposure on children's growth trajectories. We investigated the role of 90-day average postnatal fine particulate matter (PM2.5) exposures by estimating the magnitude of effects at different ages, and the change in child weight trajectory by categories of exposure.

METHODS

We obtained weight values from electronic health records at each hospital visit (males = 1859, females = 1601) from birth to 6 years old children recruited into the Boston-based Children's HealthWatch cohort (2009-2014). We applied mixed models, adjusting for individual and maternal confounders using (1) varying-coefficient models allowing for smooth non-linear interaction between age and PM2.5, (2) factor-smooth interaction between age and PM2.5 quartiles. Additionally, we stratified by sex and low birthweight (LBW) status (≤2500 g).

RESULTS

Using varying-coefficient models, we found that PM2.5 significantly modified the association between age and weight in males, with a positive association in children younger than 3 years and a negative association afterwards. In boys, for each 10 µg/m3 increase in PM2.5 we found a 2.6% increase (95% confidence interval = 0.8, 4.6) in weight at 1 year of age and a -0.6% (95% confidence interval = -3.9, 2.9) at 5 years. We found similar but smaller changes in females, and no differences comparing growth trajectories across quartiles of PM2.5. Most of the effects were in LBW children and null for normal birthweight children.

CONCLUSIONS

This study suggests that medium-term postnatal PM2.5 may modify weight trajectories nonlinearly in young children, and that LBW babies are more susceptible than normal-weight infants.

Obstetrical mode of delivery and behavioural outcomes in childhood and adolescence: findings from the Millennium Cohort Study

PURPOSE

To examine the association between mode of delivery (in particular caesarean section) and behavioural outcomes in offspring at six time-points between age 3 and 17 years.

METHODS

Similar to previous work examining the association between mode of delivery and behavioural outcomes in offspring at age 7, we used maternal-reported data from the Millennium Cohort Study. Data on mode of delivery were collected when children were 9 months and categorised as spontaneous vaginal delivery, assisted vaginal delivery, induced vaginal delivery, emergency caesarean section, planned caesarean section and caesarean section after induction of labor. Data on behavioural outcomes were collected at ages 3, 5, 7, 11, 14 and 17 years using the Strengths and Difficulties Questionnaire (SDQ). Crude and adjusted logistic regression examined mode of delivery-behavioural difficulties relationship, using validated SDQ cut-off points (total SDQ ≥ 17, emotional ≥ 5, conduct ≥ 4, hyperactivity ≥ 7, peer problems ≥ 4 and prosocial behaviour ≤ 4). Multilevel models with linear splines examined the association between mode of delivery and repeated measures of SDQ.

RESULTS

There were 18,213 singleton mother-child pairs included at baseline, 13,600 at age 3; 13,831 at age 5; 12,687 at age 7; 11,055 at age 11; 10,745 at age 14 and 8839 at age 17. Adjusted logistic regression suggested few associations between mode of delivery and behavioural outcomes at ages 3, 5, 11, 14 and 17 years using validated SDQ cut-off points. After correction for multiple testing, only the protective association between planned caesarean section-Conduct difficulties at age 5 years (OR 0.63, 95% CI 0.46, 0.85) and positive association between caesarean section after induction-Emotional difficulties at age 11 years (OR 1.57, 95% CI 1.19, 2.07) remained statistically significant. Multilevel modelling suggested mean SDQ scores were similar in each mode of delivery group at each time point.

CONCLUSIONS

Results of this study indicate that mode of delivery is unlikely to have a major impact on behavioural outcomes.

Combining Longitudinal Data From Different Cohorts to Examine the Life-Course Trajectory

Longitudinal data are necessary to reveal changes within an individual as he or she ages. However, rarely will a single cohort study capture data throughout a person's entire life span. Here we describe in detail the steps needed to develop life-course trajectories from cohort studies that cover different and overlapping periods of life. Such independent studies are probably from heterogenous populations, which raises several challenges, including: 1) data harmonization (deriving new harmonized variables from differently measured variables by identifying common elements across all studies); 2) systematically missing data (variables not measured are missing for all participants in a cohort); and 3) model selection with differing age ranges and measurement schedules. We illustrate how to overcome these challenges using an example which examines the associations of parental education, sex, and race/ethnicity with children's weight trajectories. Data were obtained from 5 prospective cohort studies (carried out in Belarus and 4 regions of the United Kingdom) spanning data collected from birth to early adulthood during differing calendar periods (1936-1964, 1972-1979, 1990-2012, 1996-2016, and 2007-2015). Key strengths of our approach include modeling of trajectories over wide age ranges, sharing of information across studies, and direct comparison of the same parts of the life course in different geographical regions and time periods. We also introduce a novel approach of imputing individual-level covariates of a multilevel model with a nonlinear growth trajectory and interactions.

Infant feeding and growth trajectories in early childhood: the application and comparison of two longitudinal modelling approaches

BACKGROUND/OBJECTIVES

The role of infant feeding practices in longitudinal growth trajectories in children remains equivocal. This study utilised two longitudinal approaches to examine the associations of infant feeding mode (breastfeeding, mixed feeding, formula feeding), breastfeeding duration, and the timing of solid foods introduction with body mass index (BMI) z-score in early childhood.

SUBJECTS/METHODS

Secondary analyses of data from the Healthy Beginnings Trial were conducted. Infant feeding practices were reported by mothers at 6, 12, and 24 months of child age. Child weight and length were measured at birth, 12, 24, 42, and 60 months. Two longitudinal approaches: linear spline multilevel model (LSMM) and group-based trajectory modelling (GBTM) were used to describe BMI z-score trajectories and assess its associations with infant feeding practices.

RESULTS

The LSMM approach demonstrated that the breastfeeding group showed lower BMI z-scores from ages 12 to 60 months than the mixed feeding and formula feeding groups. Children who were breastfed for ≥ 6 versus < 6 months exhibited a lower BMI z-score trajectory from ages 12 to 60 months. Results from the GBTM approach revealed that the mixed feeding (OR: 1.83, 95%CI 1.04, 3.21) and the formula feeding group (OR: 2.00, 95%CI 0.67, 5.92) showed a tendency for higher odds of following the "High BMIz" trajectory than the breastfeeding group. Breastfeeding duration ≥6 versus < 6 months was linked with lower odds of following the "High BMIz" trajectory (OR 0.65, 95%CI 0.43, 0.98). Both approaches revealed no evidence of an association between the timing of solid foods introduction and BMI z-score trajectory.

CONCLUSIONS

The two longitudinal approaches revealed similar findings that infant feeding mode and breastfeeding duration, but not the timing of solid foods introduction, were associated with BMI z-score trajectory in early childhood. The findings provide robust longitudinal evidence to encourage and support extended breastfeeding for childhood obesity prevention.

Joint associations of parental personality traits and socio-economic position with trajectories of offspring depression: Findings from up to 6925 families in a UK birth cohort

Background

Parental personality may influence the course of offspring depression but epidemiological evidence for associations is lacking. It is also unknown whether associations between parental personality and offspring depression differ by socio-economic position (SEP). Our aims were to describe the trajectories of depressive symptoms across adolescence of offspring of parents with and without maladaptive personality traits and to test for effect modification by SEP.

Methods

A longitudinal study in the Avon Longitudinal Study of Parents and Children birth cohort (ns = 3054-7046). Exposures were binary measures of maladaptive maternal and paternal personality traits. The outcome was depressive symptoms measured over nine occasions (ages 11-24) using the short mood and feelings questionnaire (SMFQ; range: 0-26). Effect modifiers were parental education and self-reported material hardship. Multilevel growth curve models were used to estimate trajectories.

Results

offspring of mothers with high (vs. low) maladaptive traits showed higher levels of depressive symptoms at multiple ages of adolescence, the greatest of which was observed at age 22 (predicted SMFQ difference age 10 = 0.66, 95% confidence intervals [CIs]: 0.25 to 1.28; age 22 = 1.00, CI: 0.51 to 1.50). There was weaker and inconsistent evidence of an association between paternal maladaptive personality and offspring depressive symptoms (SMFQ difference age 10 = 0.21, CI: -0.58 to 0.99; age 22 = 0.02, CI: -0.94 to 0.90). Lower SEP was also associated with higher offspring depressive symptoms (SMFQ difference material hardship vs. no hardship age 10 = 0.79, 95% CI: 0.46 to 1.13; age 22 = 0.96, CI: 0.56 to 1.36). There was minimal statistical evidence for effect modification.

Conclusions

The offspring of mothers with high levels of maladaptive personality traits show evidence of greater depressive symptoms throughout adolescence although the absolute increase in symptoms is small. Evidence for the associations with fathers' personality was weaker. Socio-economic position and maladaptive personality traits appear to be independent risk factors for offspring depressive symptoms.

Socioeconomic inequalities in prevalence and development of multimorbidity across adulthood: A longitudinal analysis of the MRC 1946 National Survey of Health and Development in the UK

BACKGROUND

We aimed to estimate multimorbidity trajectories and quantify socioeconomic inequalities based on childhood and adulthood socioeconomic position (SEP) in the risks and rates of multimorbidity accumulation across adulthood.

METHODS AND FINDINGS

Participants from the UK 1946 National Survey of Health and Development (NSHD) birth cohort study who attended the age 36 years assessment in 1982 and any one of the follow-up assessments at ages 43, 53, 63, and 69 years (N = 3,723, 51% males). Information on 18 health conditions was based on a combination of self-report, biomarkers, health records, and prescribed medications. We estimated multimorbidity trajectories and delineated socioeconomic inequalities (based on childhood and adulthood social class and highest education) in multimorbidity at each age and in longitudinal trajectories. Multimorbidity increased with age (0.7 conditions at 36 years to 3.7 at 69 years). Multimorbidity accumulation was nonlinear, accelerating with age at the rate of 0.08 conditions/year (95% CI 0.07 to 0.09, p < 0.001) at 36 to 43 years to 0.19 conditions/year (95% CI 0.18 to 0.20, p < 0.001) at 63 to 69 years. At all ages, the most socioeconomically disadvantaged had 1.2 to 1.4 times greater number of conditions on average compared to the most advantaged. The most disadvantaged by each socioeconomic indicator experienced an additional 0.39 conditions (childhood social class), 0.83 (adult social class), and 1.08 conditions (adult education) at age 69 years, independent of all other socioeconomic indicators. Adverse adulthood SEP was associated with more rapid accumulation of multimorbidity, resulting in 0.49 excess conditions in partly/unskilled compared to professional/intermediate individuals between 63 and 69 years. Disadvantaged childhood social class, independently of adulthood SEP, was associated with accelerated multimorbidity trajectories from age 53 years onwards. Study limitations include that the NSHD cohort is composed of individuals of white European heritage only, and findings may not be generalizable to the non-white British population of the same generation and did not account for other important dimensions of SEP such as income and wealth.

CONCLUSIONS

In this study, we found that socioeconomically disadvantaged individuals have earlier onset and more rapid accumulation of multimorbidity resulting in widening inequalities into old age, with independent contributions from both childhood and adulthood SEP.

Hypertensive Disorders of Pregnancy and Behavioural Outcomes in the Offspring: Findings from the Millennium Cohort Study

BACKGROUND

The aim of this study was to examine the association between hypertensive disorders of pregnancy (HDP) and behavioural outcomes in offspring at five time-points.

METHODS

We used maternal-reported data from the Millennium Cohort Study. Data on HDP were collected when children were 9-months. Data on behavioural outcomes were collected at age 3, 5, 7, 11 and 14years using the Strengths and Difficulties Questionnaire (SDQ). Multivariate logistic regression analysis examined a HDP-behavioural difficulties relationship, using validated SDQ cut-off points. Multilevel models with linear splines examined the association between HDP and repeated measures of SDQ.

RESULTS

18,274 singleton children were included in the study at baseline, Multivariate logistic regression suggested HDP was not significantly associated with SDQ domain cut-off points at ages 3, 7 and 11years. At age 5years, HDP was associated with a 40% increased odds of behavioural difficulties based on total SDQ(≥17) (OR:1.40, 95% CI:1.03,1.91). HDP was associated with a 43% increased odds of Peer Problem difficulties at age 5 (OR:1.43, 95% CI:1.10,1.86), and a 28% increased odds of Peer Problem difficulties(≥4) at age 14 (OR:1.28, 95% CI:1.02,1.61). In the linear spline model, mean SDQ score was higher at each time-point in those exposed to HDP, although did not always reach statistical significance.

LIMITATIONS

Data on different classifications of HDP were unavailable; therefore, we could not examine the effect of gestational hypertension and preeclampsia separately.

CONCLUSIONS

While we did not find strong evidence of associations between HDP and behavioural outcomes overall, some associations between HDP and behavioural difficulties did persist at age 5 and 14years.

Joint Modeling of Individual Trajectories, Within-Individual Variability, and a Later Outcome: Systolic Blood Pressure Through Childhood and Left Ventricular Mass in Early Adulthood

Within-individual variability of repeatedly measured exposures might predict later outcomes (e.g., blood pressure (BP) variability (BPV) is an independent cardiovascular risk factor above and beyond mean BP). Because 2-stage methods, known to introduce bias, are typically used to investigate such associations, we introduce a joint modeling approach, examining associations of mean BP and BPV across childhood with left ventricular mass (indexed to height; LVMI) in early adulthood with data (collected 1990-2011) from the UK Avon Longitudinal Study of Parents and Children cohort. Using multilevel models, we allowed BPV to vary between individuals (a "random effect") as well as to depend on covariates (allowing for heteroskedasticity). We further distinguished within-clinic variability ("measurement error") from visit-to-visit BPV. BPV was predicted to be greater at older ages, at higher body weights, and in female participants and was positively correlated with mean BP. BPV had a weak positive association with LVMI (10% increase in within-individual BP variance was predicted to increase LVMI by 0.21%, 95% credible interval: -0.23, 0.69), but this association became negative (-0.78%, 95% credible interval: -2.54, 0.22) once the effect of mean BP on LVMI was adjusted for. This joint modeling approach offers a flexible method of relating repeatedly measured exposures to later outcomes.

Fetal growth at different gestational periods and risk of impaired childhood growth, low childhood weight and obesity: a prospective birth cohort study

OBJECTIVE

To examine the longitudinal associations of fetal growth with adverse child growth outcomes and to assess whether maternal metabolic factors modify the associations.

DESIGN

Prospective cohort study.

SETTING

Born in Guangzhou Cohort Study, China.

POPULATION

A total of 4818 mother-child pairs.

METHODS

Fetal growth was assessed according to estimated fetal weight (EFW) from 22 weeks of gestation until birth and the measurement of the birthweight. Fetal growth Z-scores were computed from random effects in the multilevel linear spline models to represent fetal size in early pregnancy (22 weeks of gestation) and growth in mid-pregnancy (22-27 weeks of gestation), early third trimester (28-36 weeks of gestation) and late third trimester (≥37 weeks of gestation).

MAIN OUTCOME MEASURES

Z-scores for childhood stunting, low weight, overweight or obesity, length/height for age (LAZ/HAZ), weight for age (WAZ) and body mass index for age (BMIZ) at the age of 3 years. Adjusted associations were examined using multiple Poisson or linear regression models.

RESULTS

Increased Z-scores of fetal size in early pregnancy and growth in mid-pregnancy and early third trimester were associated with a higher risk of childhood overweight or obesity (risk ratios 1.25-1.45). Fetal growth in each period was negatively associated with stunting and low weight, with the strongest associations observed for fetal size in early pregnancy and growth in mid-pregnancy. The results for continuous outcomes (LAZ/HAZ, WAZ and BMIZ) were similar. The associations of fetal growth with overweight or obesity in childhood were stronger among mothers who were underweight and who were overweight or obese than among mothers of normal weight.

CONCLUSIONS

Accelerated fetal growth before 37 weeks of gestation is associated with children who are overweight or obese, whereas the critical period for stunting and low weight occurs before 28 weeks of gestation.

TWEETABLE ABSTRACT

Fetal growth during different periods is differentially associated with childhood stunting, underweight and overweight or obesity.

Clustering Longitudinal Blood Pressure Trajectories to Examine Heterogeneity in Outcomes Among Preeclampsia Cases and Controls

[Figure: see text].

Growth and neurodevelopment in low birth weight versus normal birth weight infants from birth to 24 months, born in an obstetric emergency hospital in Haiti, a prospective cohort study

BACKGROUND

Low birthweight (LBW) infants are at higher risk of mortality and morbidity (growth, chronic disease and neurological problems) during their life. Due to the high incidence of (pre-) eclampsia in Haiti, LBW infants are common. We assessed the anthropometric growth (weight and length) and neurodevelopmental delay in LBW and normal birthweight (NBW) infants born at an obstetric emergency hospital in Port au Prince, Haiti, between 2014 and 2017.

METHODS

Infants were followed at discharge and 3, 6, 12, 15, 18, 21 and 24 months of corrected gestational age. At each visit they underwent a physical checkup (weight, length, physical abnormalities, identification of morbidities). At 6, 12, 18 and 24 months they underwent a neurodevelopmental assessment using the Bayley Scale III (motor, cognitive and communication skills). We modelled the trajectories between birth and 24 months of age of NBW compared to LBW infants for weight, length, and raw scores for Bayley III assessments using mixed linear models.

RESULTS

In total 500 LBW and 210 NBW infants were recruited of which 333 (46.7%) were followed up for 24 months (127 NBW; 60.5% and 206 LBW; 41.2%) and 150 died (LBW = 137 and NBW = 13). LBW and NBW babies gained a mean 15.8 g and 11.4 g per kg of weight from discharge per day respectively. The speed of weight gain decreased rapidly after 3 months in both groups. Both groups grow rapidly up to 6 months of age. LBW grew more than the NBW group during this period (22.8 cm vs. 21.1 cm). Both groups had WHZ scores <- 2 up to 15 months. At 24 months NBW babies scored significantly higher on the Bayley scales for gross motor, cognitive and receptive and expressive communication skills. There was no difference between the groups for fine motor skills.

CONCLUSION

LBW babies that survive neonatal care in urban Haiti and live up to 24 months of age, perform similar to their NBW for weight, length and fine motor skills. LBW babies are delayed in gross motor, cognitive and communication skills development. Further research on the clinical significance of these findings and long term implications of this neurodevelopmental delay is needed.

Maternal diet in pregnancy is associated with differences in child body mass index trajectories from birth to adolescence

BACKGROUND

Nutrition in pregnancy and accelerated childhood growth are important predictors of obesity risk. Yet, it is unknown which dietary patterns in pregnancy are associated with accelerated growth and whether there are specific periods from birth to adolescence that are most sensitive to these associations.

OBJECTIVES

To examine the extent to which 3 dietary indices in pregnancy [Dietary Inflammatory Index (DII), Alternate Healthy Eating Index for Pregnancy (AHEI-P), and Mediterranean Diet Score (MDS)] are associated with child BMI z-score (BMI-z) trajectories from birth to adolescence.

METHODS

We examined 1459 mother-child dyads from Project Viva that had FFQ data in pregnancy and ≥3 child BMI-z measurements between birth and adolescence. We used linear spline mixed-effects models to examine whether BMI-z growth rates and BMI z-scores differed by quartile of each dietary index from birth to 1 mo, 1-6 mo, 6 mo to 3 y, 3-10 y, and >10 y.

RESULTS

The means ± SDs for DII (range, -9 to +8 units), AHEI-P (range, 0-90 points), and MDS (range, 0-9 points) were -2.6 ± 1.4 units, 61 ± 10 points, and 4.6 ± 2.0 points, respectively. In adjusted models, children of women in the highest (vs. lowest) DII quartile had higher BMI-z growth rates between 3-10 y (β, 0.03 SD units/y; 95% CI: 0.00-0.06) and higher BMI z-scores from 7 y through 10 y. Children of women with low adherence to a Mediterranean diet had higher BMI z-scores from 3 y through 15 y. Associations of AHEI-P with growth rates and BMI z-scores from birth through adolescence were null.

CONCLUSIONS

A higher DII and a lower MDS in pregnancy, but not AHEI-P results, are associated with higher BMI-z trajectories during distinct growth periods from birth through adolescence. Identifying the specific dietary patterns in pregnancy associated with rapid weight gain in children could inform strategies to reduce child obesity.

Prenatal lead exposure: associations with growth and anthropometry in early childhood in a UK observational birth cohort study

Background: Lead is a neurotoxic metal that crosses the placenta freely. It has adverse effects on a range of birth outcomes. The few studies reporting on the associations of prenatal exposure to lead and child growth have had conflicting results. This study aimed to examine the effect of prenatal exposure to lead on children’s growth from 4 to 61 months of age. Methods: Pregnant women were enrolled in the UK Avon Longitudinal Study of Parents and Children (ALSPAC). Whole blood samples for pregnancies with a live birth were analysed for lead (n=4140). A 10% subsample of the offspring cohort (Children in Focus) were invited to clinics at 10 time points (4–61 months) at which anthropometric measurements were carried out; z-scores for height, weight and BMI were calculated using the 1990 British Growth Reference Standards. Associations between prenatal log10-lead concentrations and z-scores and other anthropometric measures were modelled using adjusted linear regression models in an imputed dataset for children who attended at least one clinic (n=574). Results: The median prenatal blood lead concentration was 3.60 (IQR 2.61–4.16) µg/dl. There was no evidence for any associations of prenatal lead exposure with z-scores for BMI, height or weight in adjusted models from age 4 to 61 months. There were no associations for other anthropometric measures including mid-upper arm circumference, head circumference and waist circumference. There was some evidence for a weakly positive effect of prenatal lead exposure on head circumference in girls at age 43 and 61 months (at 61 months unstandardised B coefficient 1.59 (95% CI 0.12, 3.16) cm, p=0.048) but not at other ages. Conclusions: There was no consistent evidence of associations between prenatal exposure to lead and measures of growth and anthropometry from age 4 to 61 months in this cohort of children in the UK.

Longitudinal analysis of growth trajectories in young children of Chinese-born immigrant mothers compared with Australian-born mothers living in Victoria, Australia

BACKGROUND

Chinese immigrants are the third largest immigrant group in Australia. Little is known about growth trajectories of their offspring when moving to a Western country. The aim was to describe the growth trajectories between birth to 3.5 years in children of Chinese-born immigrant mothers compared with Australian-born mothers living in Victoria, Australia.

METHODS

Ten nurse measured weights and lengths from birth to 3.5 years were used to examine growth trajectory using linear spline multilevel models. Five knot points were identified at visit 2 (0.5 months), visit 4 (2 months), visit 5 (4.5 months), visit 8 (18 months) and visit 9 (25 months).

RESULTS

Ethnic disparities in growth trajectories between these two groups were revealed in models adjusted for birth weight, sex and level of socioeconomic disadvantage. Children of Chinese-born compared with Australian-born mothers revealed different growth rates and significant differences in predicted mean body mass index Z score (zBMI) at all time points from birth to 44 months, except for 12 months. Specifically, when compared with children of Australian-born mothers, children of Chinese-born mothers started with lower predicted zBMI from birth until 0.5 months, had a higher zBMI from 1 to 8 months and a lower zBMI from 12 to 44 months. Early and sharp acceleration of growth was also observed for children of Chinese-born mothers (0.5-2 months) when compared with children of Australian-born mothers (2-18 months).

CONCLUSION

Differences in growth trajectories exist between young children of Chinese-born and Australian-born mothers. Better understanding of these ethnically patterned growth trajectories is important for identifying key opportunities to promote healthy growth in early life.

Associations of Longitudinal Fetal Growth Patterns With Cardiometabolic Factors at Birth

BACKGROUND

Birth weight is associated with cardiometabolic factors at birth. However, it is unclear when these associations occur in fetal life. We aimed to investigate the associations between fetal growth in different gestational periods and cord blood cardiometabolic factors.

METHODS

We included 1,458 newborns from the Born in Guangzhou Cohort Study, China. Z-scores of fetal size parameters [weight, abdominal circumference (AC), and femur length (FL)] at 22 weeks and growth at 22-27, 28-36, and ≥37 weeks were calculated from multilevel linear spline models. Multiple linear regression was used to examine the associations between fetal growth variables and z-scores of cord blood cardiometabolic factors.

RESULTS

Fetal weight at each period was positively associated with insulin levels, with stronger association at 28-36 weeks (β, 0.31; 95% CI, 0.23 to 0.39) and ≥37 weeks (β, 0.15; 95% CI, 0.10 to 0.20) compared with earlier gestational periods. Fetal weight at 28-36 (β, -0.32; 95% CI, -0.39 to -0.24) and ≥37 weeks (β, -0.26; 95% CI, -0.31 to -0.21) was negatively associated with triglyceride levels, whereas weight at 28-36 weeks was positively associated with HDL levels (β, 0.12; 95% CI, 0.04 to 0.20). Similar results were observed for AC. Fetal FL at 22 and 22-27 weeks was associated with increased levels of insulin, glucose, and HDL.

CONCLUSIONS

Fetal growth at different gestational periods was associated with cardiometabolic factors at birth, suggesting that an interplay between fetal growth and cardiometabolic factors might exist early in pregnancy.

Longitudinal trajectories of adiposity-related measures from age 2-5 years in a population of low-income Hispanic children

BACKGROUND

We estimated longitudinal trajectories of body mass index (BMI) z-score and percentile, weight for height (WFH) z-score and percentile, and percentage of the 95th BMI percentile (BMIp95) among low-income Hispanic children ages 2-5 years to provide normative data for this population and compare the behavior of different measures.

METHODS

Longitudinal height and weight measurements obtained from 18,072 Hispanic children aged 2-5 years enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children in Los Angeles County were analyzed. Trajectories of adiposity-related measures were estimated using mixed models, stratified by sex and BMI percentile at age 2 years.

RESULTS

For children in the 5th-85th BMI percentile at age 2 years, all adiposity-related measures rose during ages 2-3.5 years; during ages 3.5-5 years, BMI-based measures increased, BMIp95 decreased, and WFH-based measures were stable. For children exceeding the 85th BMI percentile at age 2 years, measures generally trended downward during ages 2-5 years, except for BMIp95, which had variable trends.

CONCLUSIONS

Adiposity measures changed at different rates as children grew during ages 2-3.5 years compared to ages 3.5-5 years, and different measures displayed different trends. Studies should consider examining multiple measures and focusing on change relative to a comparison group.

IMPACT

To address the childhood obesity epidemic, information on normative trajectories of adiposity-related measures in at-risk populations of young children is needed. Longitudinal analysis of data collected from low-income Hispanic children during ages 2-5 years revealed different patterns for different adiposity measures and for ages 2-3.5 years versus 3.5-5 years. Child obesity studies should consider examining multiple adiposity measures and focus on change relative to a comparison group to avoid misinterpreting longitudinal patterns.

Puberty timing and adiposity change across childhood and adolescence: disentangling cause and consequence

STUDY QUESTION

Is earlier puberty more likely a result of adiposity gain in childhood than a cause of adiposity gain in adulthood?

SUMMARY ANSWER

Pre-pubertal fat mass is associated with earlier puberty timing but puberty timing is not associated with post-pubertal fat mass change.

WHAT IS KNOWN ALREADY

Age at puberty onset has decreased substantially in the last several decades. Whether reducing childhood adiposity prevents earlier puberty and if early puberty prevention itself also has additional independent benefits for prevention of adult adiposity is not well understood.

STUDY DESIGN, SIZE, DURATION

Prospective birth cohort study of 4176 participants born in 1991/1992 with 18 232 repeated measures of fat mass from age 9 to 18 years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used repeated measures of height from 5 to 20 years to identify puberty timing (age at peak height velocity, aPHV) and repeated measures of directly measured fat mass from age 9 to 18 years, from a contemporary UK birth cohort study to model fat mass trajectories by chronological age and by time before and after puberty onset. We then examined associations of these trajectories with puberty timing separately in females and males.

MAIN RESULTS AND THE ROLE OF CHANCE

In models by chronological age, a 1-year later aPHV was associated with 20.5% (95% confidence interval (CI): 18.6-22.4%) and 23.4% (95% (CI): 21.3-25.5%) lower fat mass in females and males, respectively, at 9 years. These differences were smaller at age 18 years: 7.8% (95% (CI): 5.9-9.6%) and 12.4% (95% (CI): 9.6-15.2%) lower fat mass in females and males per year later aPHV. Trajectories of fat mass by time before and after puberty provided strong evidence for an association of pre-pubertal fat mass with puberty timing, and little evidence of an association of puberty timing with post-pubertal fat mass change. The role of chance is likely to be small in this study given the large sample sizes available.

LIMITATIONS, REASONS FOR CAUTION

Participants included in our analyses were more socially advantaged than those excluded. The findings of this work may not apply to non-White populations and further work examining associations of puberty timing and fat mass in other ethnicities is required.

WIDER IMPLICATIONS OF THE FINDINGS

Previous research has relied on self-reported measures of puberty timing such as age of voice breaking in males, has lacked data on pre-and post-pubertal adiposity together and relied predominantly on indirect measures of adiposity such as BMI. This has led to conflicting results on the nature and direction of the association between puberty timing and adiposity in females and males. Our work provides important clarity on this, suggesting that prevention of adiposity in childhood is key for prevention of early puberty, adult adiposity and associated cardiovascular risk. In contrast, our findings suggest that prevention of early puberty without prevention of childhood adiposity would have little impact on prevention of adult adiposity.

STUDY FUNDING/COMPETING INTEREST(S)

The UK Medical Research Council and Wellcome (Grant ref: 102215/2/13/2) and the University of Bristol provide core support for Avon Longitudinal Study of Parents and Children (ALSPAC). L.M.O.K. is supported by a UK Medical Research Council Population Health Scientist fellowship (MR/M014509/1) and a Health Research Board (HRB) of Ireland Emerging Investigator Award (EIA-FA-2019-007 SCaRLeT). J.A.B. is supported by the Elizabeth Blackwell Institute for Health Research, University of Bristol and the Wellcome Trust Institutional Strategic Support Fund (204813/Z/16/Z). L.D.H. and A.F. are supported by Career Development Awards from the UK Medical Research Council (grants MR/M020894/1 and MR/M009351/1, respectively). All authors work in a unit that receives funds from the UK Medical Research Council (grant MC_UU_00011/3, MC_UU_00011/6). No competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Introducing a drift and diffusion framework for childhood growth research

Background: Growth trajectories are highly variable between children, making epidemiological analyses challenging both to the identification of malnutrition interventions at the population level and also risk assessment at individual level. We introduce stochastic differential equation (SDE) models into child growth research. SDEs describe flexible dynamic processes comprising: drift - gradual smooth changes - such as physiology or gut microbiome, and diffusion - sudden perturbations, such as illness or infection. Methods: We present a case study applying SDE models to child growth trajectory data from the Haydom, Tanzania and Venda, South Africa sites within the MAL-ED cohort. These data comprise n=460 children aged 0-24 months. A comparison with classical curve fitting (linear mixed models) is also presented. Results: The SDE models offered a wide range of new flexible shapes and parameterizations compared to classical additive models, with performance as good or better than standard approaches. The predictions from the SDE models suggest distinct longitudinal clusters that form distinct 'streams' hidden by the large between-child variability. Conclusions: Using SDE models to predict future growth trajectories revealed new insights in the observed data, where trajectories appear to cluster together in bands, which may have a future risk assessment application. SDEs offer an attractive approach for child growth modelling and potentially offer new insights.