Modelling subject-specific childhood growth using linear mixed-effect models with cubic regression splines

Even low levels of tree cover improve dietary quality in West Africa

Forests are attracting attention as a promising avenue to provide nutritious and "free" food without damaging the environment. Yet, we lack knowledge on the extent to which this holds in areas with sparse tree cover, such as in West Africa. This is largely due to the fact that existing methods are poorly designed to quantify tree cover in drylands. In this study, we estimate how various levels of tree cover across West Africa affect children's (aged 12-59 months) consumption of vitamin A-rich foods. We do so by combining detailed tree cover estimates based on PlanetScope imagery (3 m resolution) with Demographic Health Survey data from >15,000 households. We find that the probability of consuming vitamin A-rich foods increases from 0.45 to 0.53 with an increase in tree cover from the median value of 8.8 to 16.8% (which is the tree cover level at which the predicted probability of consuming vitamin A-rich foods is the highest). Moreover, we observe that the effects of tree cover vary across poverty levels and ecoregions. The poor are more likely than the non-poor to consume vitamin A-rich foods at low levels of tree cover in the lowland forest-savanna ecoregions, whereas the difference between poor and non-poor is less pronounced in the Sahel-Sudan. These results highlight the importance of trees and forests in sustainable food system transformation, even in areas with sparse tree cover.

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.

Current status and challenges in establishing reference intervals based on real-world data

Reference intervals (RIs) are the cornerstone for evaluation of test results in clinical practice and are invaluable in judging patient health and making clinical decisions. Establishing RIs based on clinical laboratory data is a branch of real-world data mining research. Compared to the traditional direct method, this indirect approach is highly practical, widely applicable, and low-cost. Improving the accuracy of RIs requires not only the collection of sufficient data and the use of correct statistical methods, but also proper stratification of heterogeneous subpopulations. This includes the establishment of age-specific RIs and taking into account other characteristics of reference individuals. Although there are many studies on establishing RIs by indirect methods, it is still very difficult for laboratories to select appropriate statistical methods due to the lack of formal guidelines. This review describes the application of real-world data and an approach for establishing indirect reference intervals (iRIs). We summarize the processes for establishing iRIs using real-world data and analyze the principle and applicable scope of the indirect method model in detail. Moreover, we compare different methods for constructing growth curves to establish age-specific RIs, in hopes of providing laboratories with a reference for establishing specific iRIs and giving new insight into clinical laboratory RI research. (201 words).

A Preliminary Study of Speech Rhythm Differences as Markers of Stuttering Persistence in Preschool-Age Children

PURPOSE

The purpose of this study was twofold: (a) to determine whether there are speech rhythm differences between preschool-age children who stutter that were eventually diagnosed as persisting (CWS-Per) or recovered (CWS-Rec) and children who do not stutter (CWNS), using empirical spectral analysis and empirical mode decomposition of the speech amplitude envelope, and (b) to determine whether speech rhythm characteristics close to onset are predictive of later persistence.

METHOD

Fifty children (3-4 years of age) participated in the study. Approximately 2-2.5 years after the experimental testing took place, children were assigned to the following groups: CWS-Per (nine boys, one girl), CWS-Rec (18 boys, two girls), and CWNS (18 boys, two girls). All children produced a narrative based on a text-free storybook. From the audio recordings of these narratives, fluent utterances were selected for each child from which seven envelope-based measures were extracted. Group-based differences on each measure as well as predictive analyses were conducted to identify measures that discriminate CWS-Per versus CWS-Rec.

RESULTS

CWS-Per were found to have a relatively higher degree of power in suprasyllabic oscillations and greater variability in the timing of syllabic rhythms especially for longer utterances. A logistic regression model using two speech rhythm measures was able to discriminate the eventual outcome of recovery versus persistence, with 80% sensitivity and 75% specificity.

CONCLUSION

Findings suggest that envelope-based speech rhythm measures are a promising approach to assess speech rhythm differences in developmental stuttering, and its potential for identification of children at risk of developing persistent stuttering should be investigated further.

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.

Genetic factors affecting dopaminergic deterioration during the premotor stage of Parkinson disease

To estimate dopaminergic dysfunction in patients with Parkinson disease (PD) during the premotor stage and to investigate the effect of genetic factors on the trajectories. Using longitudinal dopamine transporter single-photon emission computed tomography data from 367 sporadic PD (sPD), 72 LRRK2 (G2019S), and 39 GBA (N370S) PD patients in the Parkinson's Progression Markers Initiative (PPMI) study, we estimated the temporal trajectories of putaminal-specific binding ratios using an integrating function between baseline values and their annual change rates. In order to test reproducibility, we computed another trajectory for sPD using positron emission tomography data of 38 sPD patients at Gangnam Severance Hospital (GSH). Temporal trajectories of sPD were compared between the groups separated by age at onset (AAO) and polygenic load for common PD risk variants, and also compared with genetic PD. sPD patients in both the PPMI and GSH cohorts showed similar onset of dopaminergic degeneration around 10 years before motor onset. Early-onset PD patients exhibited later onset of degeneration and a faster decline in dopaminergic activity during the premotor period than late-onset patients. sPD patients with high polygenic load were associated with earlier onset and slower progression of dopaminergic dysfunction. Compared to the sPD and LRRK2 PD groups, GBA PD patients exhibited faster deterioration of dopaminergic function during the premotor stage. Dopaminergic dysfunction in PD appears to start about 10 years before motor onset. Genetic factors may be contributing to the heterogeneity of dopaminergic deterioration during the premotor stage.

National and State Trends in Anxiety and Depression Severity Scores Among Adults During the COVID-19 Pandemic - United States, 2020-2021

Recent studies indicate an increase in the percentage of adults who reported clinically relevant symptoms of anxiety and depression during the COVID-19 pandemic (1-3). For example, based on U.S. Census Bureau Household Pulse Survey (HPS) data, CDC reported significant increases in symptoms of anxiety and depressive disorders among adults aged ≥18 years during August 19, 2020-February 1, 2021, with the largest increases among adults aged 18-29 years and among those with less than a high school education (1). To assess more recent national trends, as well as state-specific trends, CDC used HPS data (4) to assess trends in reported anxiety and depression among U.S. adults in all 50 states and the District of Columbia (DC) during August 19, 2020-June 7, 2021 (1). Nationally, the average anxiety severity score increased 13% from August 19-31, 2020, to December 9-21, 2020 (average percent change [APC] per survey wave = 1.5%) and then decreased 26.8% from December 9-21, 2020, to May 26-June 7, 2021 (APC = -3.1%). The average depression severity score increased 14.8% from August 19-31, 2020, to December 9-21, 2020 (APC = 1.7%) and then decreased 24.8% from December 9-21, 2020, to May 26-June 7, 2021 (APC = -2.8%). State-specific trends were generally similar to national trends, with both anxiety and depression scores for most states peaking during the December 9-21, 2020, or January 6-18, 2021, survey waves. Across the entire study period, the frequency of anxiety and depression symptoms was positively correlated with the average number of daily COVID-19 cases. Mental health services and resources, including telehealth behavioral services, are critical during the COVID-19 pandemic.

Prenatal exposures to mixtures of endocrine disrupting chemicals and children's weight trajectory up to age 5.5 in the SELMA study

Exposure to endocrine disrupting chemicals (EDCs) may impact early growth, although information is limited on exposure to combination of multiple EDCs. We aimed to evaluate the effect of prenatal exposure to EDC mixtures on birthweight z-scores and childhood weight trajectories. Twenty-six proven and suspected EDCs, were analyzed in prenatal urine and blood samples from 1118 mothers participating in the Swedish Environmental Longitudinal Mother and child Asthma and allergy (SELMA) study. Two growth parameters were estimated from each child's weight trajectory from birth to 5.5 years of age: infant growth spurt rate and age at infant peak growth velocity (PGV). Weighted quantile sum (WQS) regression was used to estimate the mixture effect and identify chemicals of concern. A one-unit increase in the EDC mixture WQS index, was associated with decreased birthweight z-scores of 0.11 (95% CI - 0.16, - 0.06), slower infant growth spurt rate of 0.01 (95% CI - 0.03, - 0.01, on the log10 scale), and delayed age at infant PGV of 0.15 months (95% CI 0.07, 0.24) after adjusting for potential confounders. Stratified analysis by sex, showed that delayed age at infant PGV was mostly observed in girls with 0.51 months (95% CI 0.26, 0.76). Identified chemicals of concern included perfluorinated alkyl substances (PFAS), Triclosan, phthalates, non-phthalate plasticizers, bisphenols, polycyclic aromatic hydrocarbons, pesticides and PCBs. Prenatal exposure to EDC mixtures was associated with lower birthweight and altered infant weight gain trajectories.

Gestational perfluoroalkyl substance exposure and body mass index trajectories over the first 12 years of life

BACKGROUND/OBJECTIVES

Gestational exposure to perfluoroalkyl substances (PFAS), a ubiquitous class of persistent endocrine disrupting chemicals, is associated with increased risk of obesity and cardiometabolic disease. However, it is unclear if gestational PFAS exposure is associated with adiposity trajectories related to adult obesity and cardiometabolic health.

SUBJECTS/METHODS

We measured perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononaoic acid, and perfluorohexanesulfonic acid (PFHxS) concentrations in maternal serum collected between 16 weeks gestation and delivery in a cohort of 345 mother-child pairs in Cincinnati, OH (enrolled 2003-06). From age 4 weeks to 12 years, we measured weight and length or height up to eight times and calculated child body mass index (BMI) (1865 repeated measures). Using covariate-adjusted linear mixed models and splines to account for repeated BMI measures and nonlinear BMI patterns, respectively, we estimated the age/magnitude of infancy BMI zenith (~1 year) and childhood BMI nadir (~5 years), BMI accrual from 8 to 12 years, and BMI at age 12 years by PFAS terciles.

RESULTS

BMI trajectories varied by PFOA concentrations (age × PFOA interaction p value = 0.03). Children born to women with higher PFOA concentrations had lower infancy and early childhood BMI, earlier BMI nadir, accelerating BMI gains in mid-childhood and adolescence, and higher BMI at age 12 years. Some of these associations were non-monotonic. PFOS and PFHxS were not associated with alterations in BMI trajectories, but were monotonically associated with lower BMI across infancy, childhood, and adolescence. Compared to children in the first PFOS tercile, those in the second (β: -0.83; 95% confidence interval (CI): -2.11, 0.51 kg/m2), and third (β: -1.41; 95% CI: -2.65, -0.14 kg/m2) had lower BMI at age 12 years.

CONCLUSIONS

These results suggest that gestational PFOA exposure may be associated with BMI trajectories related to adult obesity and cardiometabolic disease, while PFOS and PFHxS exposure is associated with lower BMI in the first 12 years of life.

Growth Trajectories in Genetic Subtypes of Prader-Willi Syndrome

Prader–Willi syndrome (PWS) is a rare disorder caused by the loss of expression of genes on the paternal copy of chromosome 15q11-13. The main molecular subtypes of PWS are the deletion of 15q11-13 and non-deletion, and differences in neurobehavioral phenotype are recognized between the subtypes. This study aimed to investigate growth trajectories in PWS and associations between PWS subtype (deletion vs. non-deletion) and height, weight and body mass index (BMI). Growth data were available for 125 individuals with PWS (63 males, 62 females), of which 72 (57.6%) had the deletion subtype. There was a median of 28 observations per individual (range 2–85), producing 3565 data points distributed from birth to 18 years of age. Linear mixed models with cubic splines, subject-specific random effects and an autoregressive correlation structure were used to model the longitudinal growth data whilst accounting for the nature of repeated measures. Height was similar for males in both PWS subtypes, with non-deletion females being shorter than deletion females for older ages. Weight and BMI were estimated to be higher in the deletion subtype compared to the non-deletion subtype, with the size of difference increasing with advancing age for weight. These results suggest that individuals with deletion PWS are more prone to obesity.

Family-based treatment program contributors to child weight loss

BACKGROUND

Multicomponent family-based behavioral treatment (FBT) program for pediatric obesity includes nutrition and physical activity education, as well as behavior therapy techniques. Studies suggest that parent weight loss is the best predictor of child weight loss in FBT. However, given the important role that parents play in the implementation of FBT for their child, isolating the effects of specific FBT treatment component requires consideration of parent influences over time.

METHODS

The following treatment components were assessed: stimulus control (high/low-fat food items in home), nutrition knowledge, energy intake, physical activity, and parental monitoring, as well as weekly anthropometric measures. Adjusted models of interest using inverse probability weights were used to evaluate the effect of specific FBT components on time-varying child weight loss rate, adjusting for time-varying influence of parent weight loss.

RESULTS

One hundred thirty-seven parent-child dyads (CHILD: mean BMI = 26.4 (3.7) and BMIz = 2.0 (0.3); mean age = 10.4 (1.3); 64.1% female; ADULT: mean BMI = 31.9 (6.3); mean age = 42.9 (6.5); 30.1% Hispanic parents; 87.1% female) participated in an FBT program. In traditional model, adult BMI change (b = 0.08; p < 0.01) was the most significant predictor of child weight loss rates and no other treatment components were significant (p's > 0.1). In models that accounted for potential influences from parental weight loss and differential attendance during treatment period, lower availability of high-fat items (b = 1.10, p < 0.02), higher availability of low-fat items (b = 3.73; p < 0.01), and higher scores on parental monitoring practices (b = 1.10, p < 0.01) were associated with greater rates of weight loss, respectively.

CONCLUSION

Results suggest that outside of parent weight change, changes in stimulus control strategies at home and improved parental-monitoring practices are important FBT components for child weight loss.

Leisure-time physical activity volume, intensity, and duration from mid- to late-life in U.S. subpopulations by race and sex. The Atherosclerosis Risk In Communities (ARIC) Study

Mitigating age-related disease and disability presents challenges. Physical activity (PA) may be influential for prolonging health and functioning, warranting characterization of its patterns over the life course in population-based data. With the availability of up to three self-reported assessments of past year leisure-time PA (LTPA) over multiple decades in 15,036 participants (26% African American; 55% women; mean baseline age=54; median follow-up=23 years) from the Atherosclerosis Risk in Communities (ARIC) Study sampled from four U.S. communities, race-sex-stratified trajectories of average weekly intensity (metabolic equivalent of task (MET)), duration (hours), and energy expenditure or volume (MET-h) of LTPA were developed from age 45 to 90 using joint models to accommodate expected non-ignorable attrition. Declines in weekly LTPA intensity, duration, and volume from age 70 to 90 were observed in white women (2.9 to 1.2 MET; 2.5 to 0.6 h; 11.1 to 2.6 MET-h), white men (2.5 to 1.0 MET; 3.5 to 1.8 h; 15.5 to 6.4 MET-h), African American women (2.5 to 2.4 MET; 0.8 to 0.1 h; 6.7 to 6.0 MET-h), and African American men (2.3 to 1.4 MET; 1.5 to 0.6 h; 8.0 to 2.3 MET-h). These data reveal population-wide shifts towards less active lifestyles in older adulthood.

Dynamic growth metrics for examining prenatal exposure impacts on child growth trajectories: Application to perfluorooctanoic acid (PFOA) and postnatal weight gain

BACKGROUND

Epidemiologic studies investigating prenatal exposures in relation to growth typically rely on cumulative growth measures such as weight or BMI. However, less is known about how prenatal exposure may impact other aspects of growth dynamics, including timing and velocity.

OBJECTIVES

To describe and apply a nonlinear growth model previously used in other health science fields to characterize postnatal growth trajectories for use in environmental epidemiology studies.

METHODS

We used a double logistic function to model child weight trajectories from birth to 5.5 years using data from the Swedish Environmental Longitudinal Mother and Child, Asthma and Allergy (SELMA) study. From this, we approximated several infant growth metrics: 1) duration of time needed to complete 90% of the infant growth spurt (Δt₁), 2) the maximum growth rate in infancy or infant peak growth velocity (PGV), 3) the age at infant PGV (δ₁), a measure of growth tempo, and 4) the weight plateau at the end of the infant growth spurt (α₁). We assessed these metrics in relation to prenatal perfluorooctanoic acid (PFOA) exposure among 1334 mother-child pairs, and differences between boys and girls.

RESULTS

Average estimated infant PGV and its timing (δ₁) were 0.68 kg/month and 3.4 months, respectively. Mean infant growth spurt duration (Δt₁) was 13 months, ending at an average weight plateau (α₁) of 8.2 kg. Higher prenatal PFOA concentrations were related to a longer duration of infant growth (Δt₁: 0.06; 95% CI = 0.01, 0.11). PGV was not impacted, but higher prenatal PFOA concentrations were significantly related to delayed infant PGV (δ₁: 0.58; 95% CI = 0.17, 0.99) and a higher post-spurt weight plateau (α₁: 0.81; 95% CI = 0.21, 1.41). After adjusting for false discovery, results were only significant for δ₁ and α₁. We observed a significant interaction by sex for the association with δ₁, and stratified analyses revealed the association was only significant among girls.

CONCLUSION

Model-derived growth metrics were consistent with published growth standards. This novel application of nonlinear growth modeling enabled detection of altered infant growth dynamics in relation to prenatal PFOA exposure. Our results may help describe how PFOA yields lower birthweights, but higher weight later in childhood. Future applications may characterize adolescent growth or additional metrics of biological interest.

Prenatal Ambient Particulate Matter Exposure and Longitudinal Weight Growth Trajectories in Early Childhood

Air pollution exposure during pregnancy has been associated with impaired fetal growth and postnatal weight gain, but few studies have examined the effect on weight growth trajectories. We examine the association between validated 1 km² resolution particulate matter (PM_2.5) concentrations, averaged over pregnancy, and sex-specific growth trajectories from birth to age six of participants in the Boston-based Children's HealthWatch cohort (4797 participants, 84,283 measures). We compared weight trajectories, predicted using polynomial splines in mixed models, between prenatal PM_2.5 above or below the median (9.5 µg/m³), and examined birth weight as an effect modifier. Females exposed to average prenatal PM_2.5 ≥ 9.5 µg/m³ had higher weights compared to females exposed to < 9.5 µg/m³ throughout the study period (0.16 kg at 24 months, 0.61 kg at 60 months). In males, higher prenatal PM_2.5 exposure was associated with significantly lower weights after 24 months of age, with differences increasing with time (-0.17 at 24 months, -0.72 kg at 60 months). Associations were more pronounced among low birth weight (<2500 g) females, but did not differ by birth weight status in males. Our findings demonstrate the complex association between air pollution exposures and childhood weight trajectories and emphasize the importance of sex-stratified analyses.

Clinical implications of age-related change of the mandibular plane angle

OBJECTIVE

To identify trajectories of ontogenetic change in the mandibular plane angle (MPA) and to describe the influence of sex and other factors on MPA during growth.

SETTING/SAMPLE

The data consisted of 7026 MPA measurements from lateral cephalographs representing longitudinal series from ages 6 to 21 for 728 individuals from the Craniofacial Growth Consortium Study (CGCS).

MATERIALS AND METHODS

Facial type was determined from MPA for each assessment, with the assessment closest to age 18 representing the adult facial type. The sample includes 366 males and 362 females, each with between 2 and 15 cephalographs. The mean number of cephalographs per individual is 10. Variation in childhood MPA (earliest assessment between 6 and 9 years of age) and adult MPA (closest assessment to age 18 between 15 and 21 years of age), and change in MPA from childhood to adulthood were compared by sex and adult facial type using ANOVA and post hoc t tests.

RESULTS

Mandibular plane angle decreased from childhood to adulthood in 92% of males and 81% of females, yet increased in 36% of males and 50% of females with the hyper-divergent adult facial type. Childhood MPA and overall change in MPA were significantly different by adult facial type.

CONCLUSIONS

Adult facial type is associated with differences in childhood MPA and change in MPA during growth. There are multiple ontogenetic pathways by which an individual can achieve a normo-divergent adult facial type, and an individual's childhood MPA does not necessarily correspond to his or her adult facial type.

Gestational weight gain trajectories over pregnancy and their association with maternal diet quality: Results from the PRINCESA cohort

OBJECTIVE

The aims of this study were to characterize, among pregnant Mexican women, gestational weight gain (GWG) trajectories; assess associations of maternal dietary quality score (MDQS) with GWG during early-mid pregnancy, middle pregnancy, late pregnancy, and prolonged pregnancy; and evaluate the association between MDQS and adequacy of GWG, throughout pregnancy. We hypothesized that higher MDQS adherence is protective against insufficient or excessive GWG across pregnancy and that the association between MDQS adherence and GWG would vary by prepregnancy body mass index (BMI) category.

METHODS

We analyzed data from 660 pregnant women participating in the PRINCESA (Pregnancy Research on Inflammation, Nutrition and City Environments: Systematic Analyses) cohort in Mexico City, 2009 to 2014. Repeated measures of dietary intake and mother's weight were obtained during pregnancy. Individual GWG trajectories were modeled in a multilevel regression framework. Associations between MDQS (low, medium, and high adherence) and GWG were investigated using mixed-effect regression models with linear splines.

RESULTS

Women with prepregnancy BMI of ≥30 kg/m2 had a slower rate of GWG (RGWG) compared with other categories. A higher adherence to MDQS was protective against an insufficient (odds ratio [OR], 0.63; 95% confidence interval [CI], 0.42-0.95; P = 0.03) and an excessive RGWG (OR, 0.62; 95% CI, 0.41-0.94; P = 0.03) throughout pregnancy, adjusting for prepregnancy BMI, energy intake, maternal age, educational level, parity, fetal sex, marital status, and physical activity. Associations between diet and RGWG differed by gestational period.

CONCLUSION

A better quality diet, as measured by MDQS, was associated with appropriate GWG during pregnancy in the PRINCESA cohort.

Comparing predictive abilities of longitudinal child growth models

The Bill and Melinda Gates Foundation's Healthy Birth, Growth and Development knowledge integration project aims to improve the overall health and well-being of children across the world. The project aims to integrate information from multiple child growth studies to allow health professionals and policy makers to make informed decisions about interventions in lower and middle income countries. To achieve this goal, we must first understand the conditions that impact on the growth and development of children, and this requires sensible models for characterising different growth patterns. The contribution of this paper is to provide a quantitative comparison of the predictive abilities of various statistical growth modelling techniques based on a novel leave-one-out validation approach. The majority of existing studies have used raw growth data for modelling, but we show that fitting models to standardised data provide more accurate estimation and prediction. Our work is illustrated with an example from a study into child development in a middle income country in South America.

Heterogeneity in childhood body mass trajectories in relation to prenatal phthalate exposure

Phthalates, compounds commonly used in plastics and personal care products, have been associated with childhood obesity in cross-sectional and some longitudinal studies. Using advanced statistical methods, we characterized the heterogeneity in body mass development patterns over childhood (ages 2-14 years) and explored associations with maternal prenatal urinary concentrations of phthalates among 335 children in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) cohort study. Height and weight were measured every one to two years in this cohort, which had a high prevalence of obesity and overweight. Building upon a previous analysis that showed a positive association between prenatal phthalate exposure and body mass index (BMI) in CHAMACOS children, we used three advanced statistical methods: generalized additive models, growth mixture models, and functional principal component analysis with tree-based methods to identify patterns of childhood BMI development and allow for non-linear relationships with the environmental exposures. Our results highlight the heterogeneity in childhood BMI development patterns and suggest a sex-specific non-linear association between prenatal monoethyl phthalate urinary concentrations and BMI level in children, confirmed across a variety of statistical methods. There is also evidence to suggest positive associations between DEHP metabolites and BMI stabilization during puberty for girls.

The association of maternal alcohol use and paraprofessional home visiting with children's health: A randomized controlled trial

OBJECTIVE

This study examines the effect of a home visiting intervention on maternal alcohol use, problematic drinking, and the association of home visiting and alcohol use on children's behavioral, cognitive, and health outcomes at 5 time points over 5 years.

METHOD

We analyzed 5,099 observations of 1,236 mothers and their children from pregnancy to 5 years postbirth, within a longitudinal cluster-randomized trial evaluating the effect of a home visiting intervention on mothers in Cape Town, South Africa. Paraprofessional home visitors coached mothers on coping with multiple risk factors, including a brief, 1-visit intervention on alcohol prevention in pregnancy. We assessed changes in maternal drinking over time in relation to the intervention, and then examined the impact of these drinking patterns on child outcomes over five years.

RESULTS

Drinking increased over the 5 years postbirth, but it was significantly lower in the intervention condition. Compared with abstinence, mothers' problematic drinking was associated with decreased child weight (-0.21 z-units) at all assessments, increased child aggressive behavior (3 to 7 additional symptoms), and decreased child performance on an executive functioning measure (the silly sounds task; odds ratio = .34) at 3 and 5 years. The intervention's effect was associated with increased child aggression (0.25 to 0.75 of 1 additional symptom), but the intervention appeared to decrease the effect of problem drinking on children's aggressive acts and executive functioning.

CONCLUSION

These findings support the need for sustained interventions to reduce alcohol use, especially for mothers who exhibit problematic drinking. Maternal drinking influences children's health and development over time. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Identifying Critical Points of Trajectories of Depressive Symptoms from Childhood to Young Adulthood

Depression is a common mental illness and research has focused on late childhood and adolescence in an attempt to prevent or reduce later psychopathology and/or social impairments. It is important to establish and study population-averaged trajectories of depressive symptoms across adolescence as this could characterise specific changes in populations and help identify critical points to intervene with treatment. Multilevel growth-curve models were used to explore adolescent trajectories of depressive symptoms in 9301 individuals (57% female) from the Avon Longitudinal Study of Parents and Children, a UK based pregnancy cohort. Trajectories of depressive symptoms were constructed for males and females using the short mood and feelings questionnaire over 8 occasions, between 10 and 22 years old. Critical points of development such as age of peak velocity for depressive symptoms (the age at which depressive symptoms increase most rapidly) and the age of maximum depressive symptoms were also derived. The results suggested that from similar initial levels of depressive symptoms at age 11, females on average experienced steeper increases in depressive symptoms than males over their teenage and adolescent years until around the age of 20 when levels of depressive symptoms plateaued and started to decrease for both sexes. Females on average also had an earlier age of peak velocity of depressive symptoms that occurred at 13.5 years, compared to males who on average had an age of peak velocity at 16 years old. Evidence was less clear for a difference between the ages of maximum depressive symptoms which were on average 19.6 years for females and 20.4 for males. Identifying critical periods for different population subgroups may provide useful knowledge for treating and preventing depression and could be tailored to be time specific for certain groups. Possible explanations and recommendations are discussed.

Effects of Kinesiology Tape on Non-linear Center of Mass Dispersion During the Y Balance Test

Static taping of the ankle or knee joint is a common method of reducing risk of injury by providing mechanical stability. An alternative taping technique employs kinesiology tape, which has the additional benefit of improving functionality by stimulating proprioception. There is substantial disagreement whether kinesiology tape shows significant differences in proprioception and postural stability as compared to rigid/static tape when applied at the lower limb. The current study investigated the effects of kinesiology tape and static tape during a Y Balance Test on center of mass as an indicator for postural stability. Forty-one individuals, free of injury, performed the Y Balance Test under the three conditions; no tape, kinesiology tape, and static tape applied at the lower limb to the quadriceps, triceps surae and ankle joint. All participants completed the Y Balance Test to determine whether any significant differences could be observed using center of mass movement as a surrogate measure for balance and proprioception. The Minkowski-Bouligand and box-counting fractal dimension analyses were used as measures of the dynamic changes in the center of mass whilst undertaking the Y Balance Test. Statistical analyses included the Kruskal Wallis test to allow for non-normally distributed data and a Bonferroni corrected pairwise T-test as a post hoc test to ascertain pairwise differences between the three taping conditions. Significance was set at 0.05. The fractal analyses of the dynamic changes in center of mass showed significant differences between the control and both the static tape and kinesiology tape groups (p = 0.021 and 0.009, respectively). The current study developed a novel measure of dynamic changes in the center of mass during a set movement that indicated real-time processing effects during a balance task associated with the type of taping used to enhance postural stability.

Dynamic prediction in functional concurrent regression with an application to child growth

In many studies, it is of interest to predict the future trajectory of subjects based on their historical data, referred to as dynamic prediction. Mixed effects models have traditionally been used for dynamic prediction. However, the commonly used random intercept and slope model is often not sufficiently flexible for modeling subject-specific trajectories. In addition, there may be useful exposures/predictors of interest that are measured concurrently with the outcome, complicating dynamic prediction. To address these problems, we propose a dynamic functional concurrent regression model to handle the case where both the functional response and the functional predictors are irregularly measured. Currently, such a model cannot be fit by existing software. We apply the model to dynamically predict children's length conditional on prior length, weight, and baseline covariates. Inference on model parameters and subject-specific trajectories is conducted using the mixed effects representation of the proposed model. An extensive simulation study shows that the dynamic functional regression model provides more accurate estimation and inference than existing methods. Methods are supported by fast, flexible, open source software that uses heavily tested smoothing techniques.

Epothilone D accelerates disease progression in the SOD1G93A mouse model of amyotrophic lateral sclerosis

AIMS

Degeneration of the distal neuromuscular circuitry is a hallmark pathology of Amyotrophic Lateral Sclerosis (ALS). The potential for microtubule dysfunction to be a critical pathophysiological mechanism in the destruction of this circuitry is increasingly being appreciated. Stabilization of microtubules to improve neuronal integrity and pathology has been shown to be a particularly favourable approach in other neurodegenerative diseases. We present evidence here that treatment with the microtubule-targeting compound Epothilone D (EpoD) both positively and negatively affects the spinal neuromuscular circuitry in the SOD1^G93A mouse model of ALS.

METHODS

SOD1^G93A mice were treated every 5 days with 2 mg/kg EpoD. Evaluation of motor behaviour, neurological phenotype and survival was completed, with age-dependent histological characterization also conducted, using the thy1-YFP mouse. Motor neuron degeneration, axonal integrity, neuromuscular junction (NMJ) health and gliosis were also assessed.

RESULTS

EpoD treatment prevented loss of the spinal motor neuron soma, and distal axon degeneration, early in the disease course. This, however, was not associated with protection of the NMJ synapse and did not improve motor phenotype or clinical progression. EpoD administration was also found to be neurotoxic at later disease stages. This was evidenced by accelerated motor neuron cell body loss, increasing gliosis, and was associated with detrimental outcomes to motor behaviour, clinical assessment and survival.

CONCLUSIONS

The results suggest that EpoD accelerates disease progression in the SOD1^G93A mouse model of ALS, and highlights that the pathophysiological involvement of microtubules in ALS is an evolving and underappreciated phenomenon.

Environmental enteric dysfunction and systemic inflammation predict reduced weight but not length gain in rural Bangladeshi children

Environmental enteric dysfunction (EED) and systemic inflammation (SI) are common in developing countries and may cause stunting. In Bangladesh, >40 % of preschool children are stunted, but EED and SI contributions are unknown. We aimed to determine the impact of EED and SI (assessed with multiple indicators) on growth in children (n 539) enrolled in a community-based randomised food supplementation trial in rural Bangladesh. EED was defined with faecal myeloperoxidase, α-1 antitrypsin and neopterin and serum endotoxin core antibody and glucagon-like peptide-2, consolidated into gut inflammation (GI) and permeability (GP) scores, and urinary lactulose:mannitol α-1 acid glycoprotein (AGP) characterised SI. Biomarker associations with anthropometry (15-, 18- and 24-month length-for-age (LAZ), weight-for-length (WLZ) and weight-for-age (WAZ) z scores) were examined in pairwise correlations and adjusted mixed-effects regressions. Stunting, wasting and underweight prevalence at 18 months were 45, 15 and 37 %, respectively, with elevated EED and SI markers common. EED and SI were not associated with 15–24-month length trajectory. Elevated (worse) GI and GP scores predicted reduced 18–24-month WLZ change (β −0·01 (se 0·00) z score/month for both). Elevated GP was also associated with reduced 15–18-month WLZ change (β −0·03 (se 0·01) z score/month) and greater 15-month WLZ (β 0·16 (se 0·05)). Higher AGP was associated with reduced prior and increased subsequent WLZ change (β −0·04 (se 0·01) and β 0·02 (se 0·00) z score/month for 15–18 and 18–24 months). The hypothesised link from EED to stunting was not observed in this sample of Bangladeshi 18-month-olds, but the effects of EED on constrained weight gain may have consequences for later linear growth or for other health and development outcomes.

Novel metrics for growth model selection

BACKGROUND

Literature surrounding the statistical modeling of childhood growth data involves a diverse set of potential models from which investigators can choose. However, the lack of a comprehensive framework for comparing non-nested models leads to difficulty in assessing model performance. This paper proposes a framework for comparing non-nested growth models using novel metrics of predictive accuracy based on modifications of the mean squared error criteria.

METHODS

Three metrics were created: normalized, age-adjusted, and weighted mean squared error (MSE). Predictive performance metrics were used to compare linear mixed effects models and functional regression models. Prediction accuracy was assessed by partitioning the observed data into training and test datasets. This partitioning was constructed to assess prediction accuracy for backward (i.e., early growth), forward (i.e., late growth), in-range, and on new-individuals. Analyses were done with height measurements from 215 Peruvian children with data spanning from near birth to 2 years of age.

RESULTS

Functional models outperformed linear mixed effects models in all scenarios tested. In particular, prediction errors for functional concurrent regression (FCR) and functional principal component analysis models were approximately 6% lower when compared to linear mixed effects models. When we weighted subject-specific MSEs according to subject-specific growth rates during infancy, we found that FCR was the best performer in all scenarios.

CONCLUSION

With this novel approach, we can quantitatively compare non-nested models and weight subgroups of interest to select the best performing growth model for a particular application or problem at hand.

Dynamic child growth prediction: A comparative methods approach

Abstract:

We introduce a class of dynamic regression models designed to predict the future of growth curves based on their historical dynamics. This class of models incorporates both baseline and time-dependent covariates, start with simple regression models and build up to dynamic function-on-function regressions. We compare the performance of the dynamic prediction models in a variety of signal-to-noise scenarios and provide practical solutions for model selection. We conclude that (a) prediction performance increases substantially when using the entire growth history relative to using only the last and first observation; (b) smoothing incorporated using functional regression approaches increases prediction performance; and (c) the interpretation of model parameters is substantially improved using functional regression approaches. Because many growth curve datasets exhibit missing and noisy data, we propose a bootstrap of subjects approach to account for the variability associated with the missing data imputation and smoothing. Methods are motivated by and applied to the CONTENT dataset, a study that collected monthly child growth data on 197 children from birth until month 15. R code describing the fitting approaches is provided in a supplementary file.

Bayesian hierarchical piecewise regression models: a tool to detect trajectory divergence between groups in long-term observational studies

Background

Bayesian hierarchical piecewise regression (BHPR) modeling has not been previously formulated to detect and characterise the mechanism of trajectory divergence between groups of participants that have longitudinal responses with distinct developmental phases. These models are useful when participants in a prospective cohort study are grouped according to a distal dichotomous health outcome. Indeed, a refined understanding of how deleterious risk factor profiles develop across the life-course may help inform early-life interventions. Previous techniques to determine between-group differences in risk factors at each age may result in biased estimate of the age at divergence.

Methods

We demonstrate the use of Bayesian hierarchical piecewise regression (BHPR) to generate a point estimate and credible interval for the age at which trajectories diverge between groups for continuous outcome measures that exhibit non-linear within-person response profiles over time. We illustrate our approach by modeling the divergence in childhood-to-adulthood body mass index (BMI) trajectories between two groups of adults with/without type 2 diabetes mellitus (T2DM) in the Cardiovascular Risk in Young Finns Study (YFS).

Results

Using the proposed BHPR approach, we estimated the BMI profiles of participants with T2DM diverged from healthy participants at age 16 years for males (95% credible interval (CI):13.5–18 years) and 21 years for females (95% CI: 19.5–23 years). These data suggest that a critical window for weight management intervention in preventing T2DM might exist before the age when BMI growth rate is naturally expected to decrease. Simulation showed that when using pairwise comparison of least-square means from categorical mixed models, smaller sample sizes tended to conclude a later age of divergence. In contrast, the point estimate of the divergence time is not biased by sample size when using the proposed BHPR method.

Conclusions

BHPR is a powerful analytic tool to model long-term non-linear longitudinal outcomes, enabling the identification of the age at which risk factor trajectories diverge between groups of participants. The method is suitable for the analysis of unbalanced longitudinal data, with only a limited number of repeated measures per participants and where the time-related outcome is typically marked by transitional changes or by distinct phases of change over time.

Electronic supplementary material

The online version of this article (doi:10.1186/s12874-017-0358-9) contains supplementary material, which is available to authorized users.