Power for balanced linear mixed models with complex missing data processes.

When designing repeated measures studies, both the amount and the pattern of missing outcome data can affect power. The chance that an observation is missing may vary across measurements, and missingness may be correlated across measurements. For example, in a physiotherapy study of patients with Parkinson's disease, increasing intermittent dropout over time yielded missing measurements of physical function.

A Nested Case-Control Study of Allopregnanolone and Preterm Birth in the Healthy Start Cohort.

Context: Chronic stress is a risk factor for preterm birth; however, objective measures of stress in pregnancy are limited. Maternal stress biomarkers may fill this gap. Steroid hormones and neurosteroids such as allopregnanolone (ALLO) play important roles in stress physiology and pregnancy maintenance and therefore may be promising for preterm birth prediction.

Childhood nutrient intakes are differentially associated with hepatic and abdominal fats in adolescence: The EPOCH study.

Objective: The aim of this study was to examine whether nutrient intakes in childhood are associated with abdominal and hepatic fat depots later in adolescence.

Methods: Using data from 302 participants in the longitudinal Exploring Perinatal Outcomes among CHildren (EPOCH) study, energy partition and nutrient density models were constructed to examine associations of nutrient intakes in childhood (~10 years of age), assessed by food frequency questionnaire, with abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and hepatic fat in adolescence (~16 years of age).

Results: In energy partition models (energy intake not held constant), total, monounsaturated, and polyunsaturated fat intakes in childhood were associated with higher SAT in adolescence (β [95% CI]: 8.

Adherence to index-based dietary patterns in childhood and BMI trajectory during the transition to adolescence: the EPOCH study.

Background: In the United States, one in five adolescents are obese. Index-based dietary patterns are measures of the overall diet that have the potential to serve as valuable obesity risk stratification tools. However, little is known about the association between adherence to index-based dietary patterns in childhood and BMI during the transition from childhood to adolescence.

A power approximation for the Kenward and Roger Wald test in the linear mixed model.

We derive a noncentral [Formula: see text] power approximation for the Kenward and Roger test. We use a method of moments approach to form an approximate distribution for the Kenward and Roger scaled Wald statistic, under the alternative. The result depends on the approximate moments of the unscaled Wald statistic.

Associations of Nutrient Intake Changes During Childhood with Adolescent Hepatic Fat: The Exploring Perinatal Outcomes Among CHildren Study.

Objective: To examine associations of dietary changes from childhood to adolescence with adolescent hepatic fat and whether the PNPLA3 rs738409 risk allele, a strong genetic risk factor for hepatic fat, modifies associations.

Study Design: Data were from 358 participants in the Exploring Perinatal Outcomes among CHildren (EPOCH) study, a longitudinal cohort in Colorado. Diet was assessed by food frequency questionnaire in childhood (approximately 10 years of age) and adolescence (approximately 16 years of age) and converted to nutrient densities.

The maternal diet index in pregnancy is associated with offspring allergic diseases: the Healthy Start study.

Background: A systematic review showed limited associations between pregnancy diet and offspring allergy. We developed a maternal diet index during pregnancy that was associated with offspring allergy outcomes.

Methods: Data came from Healthy Start, a Colorado pre-birth cohort of mother/offspring dyads.

Examining Associations Between Dietary Inflammatory Index in Pregnancy, Pro-inflammatory Cytokine and Chemokine Levels at Birth, and Offspring Asthma and/or Wheeze by Age 4 Years.

Background: Few studies have demonstrated associations between maternal dietary inflammatory index (DII) during pregnancy and offspring asthma and/or wheeze.

Objective: The study aimed to assess associations between maternal DII during pregnancy and 1) offspring cord sera pro-inflammatory cytokines (interleukin [IL]-1β, IL-4, IL-6, IL-10, tumor necrosis factor-α) and chemokines (IL-8, monocyte chemoattractant protein-1) at birth and 2) offspring asthma and/or wheeze at age 4 years.

Design: The Healthy Start study is a prospective prebirth longitudinal study that recruited pregnant women in Denver, Colorado and tracked their offspring.

A Prudent dietary pattern is inversely associated with liver fat content among multi-ethnic youth.

Objectives: To identify dietary patterns associated with hepatic fat fraction (HFF), a measure of liver fat content and risk factor for non-alcoholic fatty liver disease, in a prospective study of 397 multi-ethnic youth.

Methods: We obtained information on habitual dietary intake via the Block Kids Food Frequency Questionnaire at age 6 to 15 years ('T1') and 12 to 19 years ('T2'), and measured HFF using magnetic resonance imaging at T2. We derived dietary patterns via principal components analysis and examined associations with ln-transformed HFF using linear regression models that accounted for maternal education, gestational diabetes exposure and smoking habits; and child pubertal status, BMI and physical activity.

Combined environmental and social exposures during pregnancy and associations with neonatal size and body composition: the Healthy Start study.

Background: Prenatal environmental and social exposures have been associated with decreased birth weight. However, the effects of combined exposures in these domains are not fully understood. Here we assessed multi-domain exposures for participants in the Healthy Start study (Denver, CO) and tested associations with neonatal size and body composition.

Sex differences in infant body composition emerge in the first 5 months of life.

Background Sex differences in body composition are appreciated throughout the lifespan with probable contributions from sex steroids: testosterone and estrogen. The purpose of this longitudinal observational study was to determine if sex differences in body composition emerge during the first months of life in healthy infants, corresponding to the age at which male infants produce endogenous testosterone. Methods Linear growth and body composition parameters using air displacement plethysmography were obtained from 602 healthy infants after birth and again at 5 months of age.

Persistent effects of in utero overnutrition on offspring adiposity: the Exploring Perinatal Outcomes among Children (EPOCH) study.

Aims/hypothesis: We previously showed that intrauterine exposure to gestational diabetes mellitus (GDM) increases selected markers of adiposity in pre-pubertal adolescents. In the present study, we examined these associations in adolescence, and explored whether they are strengthened as the participants transition through puberty.

Methods: Data from 597 individuals (505 unexposed, 92 exposed) participating in the longitudinal Exploring Perinatal Outcomes among Children (EPOCH) study in Colorado were collected at two research visits when the participants were, on average, 10.

Improving the diagnostic accuracy of a stratified screening strategy by identifying the optimal risk cutoff.

Background: The American Cancer Society (ACS) suggests using a stratified strategy for breast cancer screening. The strategy includes assessing risk of breast cancer, screening women at high risk with both MRI and mammography, and screening women at low risk with mammography alone. The ACS chose their cutoff for high risk using expert consensus.

Cord Blood Vitamin D Levels and Early Childhood Blood Pressure: The Healthy Start Study.

Background Vitamin D deficiency is associated with cardiovascular events among adults, but it is unclear whether early-life vitamin D deficiency influences cardiovascular risk factors in children. Methods and Results We measured total and bioavailable 25-dihydroxyvitamin D (25OHD) in cord blood and in blood from 4- to 6-year-old children, and we assessed cardiovascular risk factors (blood pressure, arterial stiffness, body size, and adiposity) at 4 to 6 years. We tested for racial/ethnic differences in total and bioavailable 25OHD (n=715) and modeled the adjusted association between cord blood 25OHD and childhood cardiovascular risk factors (n=171).

Infant Feeding Practices In a Diverse Group of Women: The Healthy Start Study.

Background: To describe infant feeding practices among a diverse group of mother-offspring pairs and identify factors associated with adherence to the American Academy of Pediatrics (AAP) recommendations.

Methods: Data were analyzed from 835 mother-offspring dyads in The Healthy Start Study, an ongoing longitudinal prebirth cohort in Denver, Colorado. Maternal report of infant feeding practices was obtained at 4 to 6 months and 18 to 24 months postnatally.

Fetal exposure to maternal active and secondhand smoking with offspring early-life growth in the Healthy Start study.

Background: Previous studies have modeled the association between fetal exposure to tobacco smoke and body mass index (BMI) growth trajectories, but not the timing of catch-up growth. Research on fetal exposure to maternal secondhand smoking is limited.

Objectives: To explore the associations between fetal exposure to maternal active and secondhand smoking with body composition at birth and BMI growth trajectories through age 3 years.

Proinflammatory Diets during Pregnancy and Neonatal Adiposity in the Healthy Start Study.

Objective: To evaluate the association between dietary inflammatory index (DII) scores during pregnancy and neonatal adiposity.

Study Design: The analysis included 1078 mother-neonate pairs in Healthy Start, a prospective prebirth cohort. Diet was assessed using repeated 24-hour dietary recalls.

Fetal Overnutrition and Adolescent Hepatic Fat Fraction: the Exploring Perinatal Outcomes in Children Study.

Objective: To determine if fetal overnutrition resulting from maternal obesity or gestational diabetes mellitus (GDM) is associated with increased liver fat during adolescence, adjusting for past and current metabolic risk factors.

Study Design: Data come from a historical prospective cohort study (Exploring Perinatal Outcomes in Children) of 254 mother-child pairs in Colorado who participated in 2 research visits at T1 (mean age 10.4, SD = 1.

An observational cohort study of weight- and length-derived anthropometric indicators with body composition at birth and 5 mo: the Healthy Start study.

Despite widespread use of weight- and length-based anthropometric indexes as proxies for adiposity, little is known regarding the extent to which they correspond with fat mass (FM) or fat-free mass (FFM) during infancy. This study aimed to examine associations of 3 derived indicators-weight-for-age score (WFAZ), weight-for-length score (WFLZ), and body mass index score (BMIZ)-with FM, percentage of FM, and FFM measured by air-displacement plethysmography during the first 5 mo of life. Applying prospectively collected data from 1027 infants in a Colorado prebirth cohort, we used multivariate regression to evaluate associations between the derived indicators and body composition at birth and at 5 mo, and with change (Δ) during follow-up.