Precision of recumbent crown-heel length when using an infantometer.

BACKGROUND: Crown-heel length (CHL) measurement is influenced by technique, training, experience and subject cooperation. We investigated whether extending one or both of an infant's legs affects the precision of CHL taken using an infantometer. The influence of staff training and infant cooperation were also examined. METHODS: CHL was measured in children (aged 2), infants (aged 1) and newborns, by extending one or both legs. The subject's level of cooperation was recorded. Mean differences were compared using Student's t-test; intra- and inter-observer variability were assessed using Bland-Altman plots with 95 % limits of agreement. Intra- and inter-observer technical errors of measurement (TEMs) were also calculated. RESULTS: Measuring CHL in newborns using only one leg resulted in significantly longer measurements. Across all groups, there was less inter-observer variability using both legs; 95 % limits of agreement were lower and TEMs smaller. Larger measurement differences were seen if children were uncooperative. CONCLUSIONS: This study supports measuring CHL with both legs extended. The two-leg technique reduces variability and increases precision by allowing the measurer to control better the position and movements of the infant's body.

Validation of Maturity Offset in the Fels Longitudinal Study.

Sex-specific equations for predicting maturity offset, time before or after peak height velocity (PHV), were evaluated in 63 girls and 74 boys from the Fels Longitudinal Study. Serially measured heights (0.1 cm), sitting heights (0.1 cm), weights (0.1 kg), and estimated leg lengths (0.1 cm) from 8 to 18 years were used. Predicted age at PHV (years) was calculated as the difference between chronological age (CA) and maturity offset. Actual age at PHV for each child was derived with a triple logistic model (Bock-Thissen-du Toit). Mean predicted maturity offset was negative and lowest at 8 years and increased linearly with increasing CA. Predicted ages at PHV increased linearly with CA from 8 to 18 years in girls and from 8 to 13 years in boys; predictions varied within relatively narrow limits from 12 to 15 years and then increased to 18 years in boys. Differences between predicted and actual ages at PHV among youth of contrasting maturity status were significant across the age range in both sexes. Dependence of predicted age at PHV upon CA at prediction and on actual age at PHV limits its utility as an indicator of maturity timing and in sport talent programs.

An update of the statistical methods underlying the FELS method of skeletal maturity assessment.

BACKGROUND: Evaluation of skeletal maturity provides clinicians and researchers a window into the developmental progress of the skeleton. The FELS method for maturity assessment provides a point estimate and standard error based on 98 skeletal indicators. AIM: This paper outlines the statistical methodology used by the original FELS method and evaluates improvements that address the following: serial correlation in the calibration sample is now considered, a Bayesian estimation method is now employed to improve estimation near ages 0 and 18 years and uncertainty in the calibration due to sampling is now accounted for when computing confidence limits. SUBJECTS AND METHODS: The original FELS method was calibrated using 677 Fels Longitudinal Study participants. In the improved method, serial correlation is accounted for using GEE, a Bayesian analysis with a prior centred on chronological age is used and the bootstrap is used to account for all sources of variation. RESULTS: Accounting for serial correlation resulted in larger slopes for ordinal indicators. The Bayesian paradigm led to narrower confidence limits and a natural interpretation of skeletal age. Sampling variability in the calibration parameters was negligible. CONCLUSION: Improvements to the statistical basis of the FELS method provide a more effective method of estimating skeletal maturity.

Predicting the timing of maturational spurts in skeletal age.

Measures of maturity provide windows into the timing and tempo of childhood growth and maturation. Delayed maturation in a single child, or systemically in a population, can result from either genetic or environmental factors. In terms of the skeleton, delayed maturation may result in short stature or indicate another underlying issue. Thus, prediction of the timing of a maturational spurt is often desirable in order to determine the likelihood that a child will catch up to their chronological age peers. Serial data from the Fels Longitudinal Study were used to predict future skeletal age conditional on current skeletal age and to predict the timing of maturational spurts. For children who were delayed relative to their chronological age peers, the likelihood of catch-up maturation increased through the average age of onset of puberty and decreased prior to the average age of peak height velocity. For boys, the probability of an imminent maturational spurt was higher for those who were less mature. For girls aged 11 to 13 years, however, this probability was higher for those who were more mature, potentially indicating the presence of a skeletal maturation plateau between multiple spurts. The prediction model, available on the web, is most relevant to children of European ancestry living in the Midwestern US. Our model may also provide insight into the tempo of maturation for children in other populations, but must be applied with caution if those populations are known to have high burdens of environmental stressors not typical of the Midwestern US.

Secular trends in the fat and fat-free components of body mass index in children aged 8-18 years born 1958-1995.

BACKGROUND: It is unknown whether the secular trend in childhood BMI reflects increases in fat-free mass as well as fat mass. METHODS: This study decomposed BMI trends in 488 participants in the Fels Longitudinal Study born between 1958-1995 and aged 8-17.99 years into their fat and fat-free components. Generalized estimating equations estimated birth year cohort (1958-1970, 1971-1983, 1984-1995) effects on 2208 observations of BMI, fat mass index (FMI = fat mass (kg)/height (m)(2)) and fat-free mass index (FFMI = fat-free mass (kg)/height (m)(2)). RESULTS: BMI in boys increased across cohorts, with those born between 1984-1995 being 2 kg/m(2) larger than those born between 1958-1970 (p = 0.001) and increases in FMI were highly significant (p-values < 0.001). FFMI did not differ by cohort. In girls, there was a significant advantage in BMI (1.2 kg/m(2)) and FFMI (0.8 kg/m(2)) of the 1984-1995 cohort compared to the 1971-1983 cohort (p-values < 0.05). CONCLUSIONS: Because the long term trend in childhood BMI in boys appears to be driven by an increase in total body adiposity, evidence is provided to support current knowledge on the predicted deleterious long-term consequences of the childhood obesity epidemic in boys. Research is needed to confirm whether recent changes in BMI in girls are due to increases in fat-free mass resulting from changes in behaviour and lifestyle not yet manifest in boys.

The influence of age at menarche on cross-sectional geometry of bone in young adulthood.

Elucidating the somatic and maturational influences on the biomechanical properties of bone in children is crucial for a proper understanding of bone strength and quality in childhood and later life, and has significant potential for predicting adult fracture and osteoporosis risks. The ability of a long bone to resist bending and torsion is primarily a function of its cross-sectional geometric properties, and is negatively impacted by smaller external bone diameter. In pubescent girls, elevated levels of estrogen impede subperiosteal bone growth and increase endosteal bone deposition, resulting in bones averaging a smaller external and internal diameter relative to boys. In addition, given a well-documented secular trend for an earlier menarche, the age at which the rate of subperiosteal bone deposition decreases may also be younger in more recent cohorts of girls. In this study we examined the relationship between pubertal timing and subsequent bone strength in girls. Specifically, we investigated the effects of age at menarche on bone strength indicators (polar moment of inertia and section modulus) determined from cross-sectional geometry of the second metacarpal (MC2) using data derived from serial hand-wrist radiographs of female participants (N=223) in the Fels Longitudinal Study, with repeated measures of MC2 between the ages of 7 and 35 years. Using multivariate regression models, we evaluated the effects of age at menarche on associations between measures of bone strength in early adulthood and the same measures at a prepubertal age. Results indicate that later age at menarche is associated with stronger adult bone (in torsion and bending) when controlling for prepubertal bone strength (R(2) ranged between 0.54 and 0.70, p<0.001). Since cross-sectional properties of bone in childhood may have long lasting implications, they should be considered along with pubertal timing in assessing risk for future fracture and in clinical recommendations.

Cortical bone health shows significant linkage to chromosomes 2p, 3p, and 17q in 10-year-old children.

Genes play an important role in lifelong skeletal health. Genes that influence bone building during childhood have the potential to affect bone health not only throughout childhood but also into adulthood. Given that peak bone mass is a significant predictor of adult fracture risk, it is imperative that the genetic underpinnings of the normal pediatric skeleton are uncovered. In a sample of 600 10-year-old children from 144 families in the Fels Longitudinal Study, we examined radiographic cortical bone measures of the second metacarpal. Morphometic measurements included bone width, medial and lateral cortical thicknesses, and the calculated cortical index representing the amount of cortex relative to bone width. We then conducted genome-wide linkage analysis on these traits in 440 genotyped individuals using the SOLAR analytic platform. Significant quantitative trait loci (QTL) were identified for bone traits on three separate chromosomes. A QTL for medial cortical thickness was localized to chromosome 2p25.2. A QTL for lateral cortical thickness was localized to chromosomal region 3p26.1-3p25.3. Finally, a QTL detected for cortical index was localized to the 17q21.2 chromosomal region. Each region contains plausible candidate genes for pediatric skeletal health, some of which confirm findings from studies of adulthood bone, and for others represent novel candidate genes for skeletal health.

A genome-wide linkage scan for quantitative trait loci influencing the craniofacial complex in humans (Homo sapiens sapiens).

The genetic architecture of the craniofacial complex has been the subject of intense scrutiny because of the high frequency of congenital malformations. Numerous animal models have been used to document the early development of the craniofacial complex, but few studies have focused directly on the genetic underpinnings of normal variation in the human craniofacial complex. This study examines 80 quantitative traits derived from lateral cephalographs of 981 participants in the Fels Longitudinal Study, Wright State University, Dayton, Ohio. Quantitative genetic analyses were conducted using the Sequential Oligogenic Linkage Analysis Routines analytic platform, a maximum-likelihood variance components method that incorporates all familial information for parameter estimation. Heritability estimates were significant and of moderate to high magnitude for all craniofacial traits. Additionally, significant quantitative trait loci (QTL) were identified for 10 traits from the three developmental components (basicranium, splanchnocranium, and neurocranium) of the craniofacial complex. These QTL were found on chromosomes 3, 6, 11, 12, and 14. This study of the genetic architecture of the craniofacial complex elucidates fundamental information of the genetic architecture of the craniofacial complex in humans.

Significant associations of age, menopausal status and lifestyle factors with visceral adiposity in African-American and European-American women.

BACKGROUND: Elevated visceral adiposity is strongly predictive of cardiometabolic disease, but, due to the high cost of biomedical imaging, assessment of factors contributing to normal variation in visceral (VAT) and subcutaneous (SAT) adipose tissue partitioning in large cohorts of healthy individuals are few, particularly in ethnic and racial minority populations. OBJECTIVE: To describe age, menopausal status, smoking and physical activity differences in VAT and abdominal subcutaneous adipose tissue (ASAT) mass in African-American (AA) and European-American (EA) women. METHODS: Magnetic resonance imaging measures of VAT and ASAT mass and VAT% (VAT/VAT+ASAT, %) were obtained from a cross-sectional sample of 617 EA and 111 AA non-diabetic women aged 18-80 years. Multivariate linear regression was used to test independent effects of the covariates. RESULTS: VAT and VAT% were higher in EA than AA women (p < 0.01). Differences in VAT, ASAT and VAT% across age groups began in early adulthood in both ethnic groups, but the association of age with VAT% was stronger in EA women (p for interaction = 0.03). Current smokers had higher VAT and VAT% (p < 0.01) and lower TBF than non-smokers. Frequent participation in sports activities was associated with ∼30% lower VAT in older (>55 years) as well as younger ( < 40 years) women (p < 0.0001). CONCLUSION: Greater allocation of abdominal adipose tissue into the visceral compartment occurs in EA than AA women and in older than younger women. Avoidance of cigarette smoking and frequent participation in sports activities may partially counteract this deleterious phenomenon of ageing.

Validity of adolescent diet recall 48 years later.

Few studies have evaluated the validity of adolescent diet recall after many decades. Between 1943 and 1970, yearly diet records were completed by parents of adolescents participating in an ongoing US study. In 2005-2006, study participants who had been 13-18 years of age when the diet records were collected were asked to complete a food frequency questionnaire regarding their adolescent diet. Food frequency questionnaires and diet records were available for 72 participants. The authors calculated Spearman correlation coefficients between food, food group, and nutrient intakes from the diet records and food frequency questionnaire and deattenuated them to account for the effects of within-person variation measured in the diet records on the association. The median deattenuated correlation for foods was 0.30, ranging from -0.53 for a beef, pork, or lamb sandwich to 0.99 for diet soda. The median deattenuated correlation for food groups was 0.31 (range: -0.48 for breads to 0.70 for hot beverages); for nutrient intakes, it was 0.25 (range: -0.08 for iron to 0.82 for vitamin B(12)). Some dietary factors were reasonably recalled 3-6 decades later. However, this food frequency questionnaire did not validly measure overall adolescent diet when completed by middle-aged and older adults on average 48 years after adolescence.

Genetic and environmental influences on infant weight and weight change: the Fels Longitudinal Study.

Despite significant progress in understanding the mechanisms by which the prenatal/maternal environment can alter development and adult health, genetic influences on normal variation in growth are little understood. This work examines genetic and nongenetic contributions to body weight and weight change during infancy and the relationships between weight change and adult body composition. The dataset included 501 white infants in 164 nuclear and extended families in the Fels Longitudinal Study, each with 10 serial measures of weight from birth to age 3 years and 232 with body composition data in mid-adulthood. Heritability and covariate effects on weight and weight z-score change from birth to 2 years of age were estimated using a maximum likelihood variance decomposition method. Additive genetic effects explained a high proportion of the variance in infant weight status (h2=0.61-0.95), and change in weight z-score (h2=0.56-0.82). Covariate effects explained 27% of the phenotypic variance at 0-1 month of age and declined in effect to 6.9% of phenotypic variance by 36 months. Significant sex, gestational age, birth order, birth year, and maternal body mass index effects were also identified. For both sexes, a significant increase in weight z-score (>2 SD units) (upward centile crossing) was associated with greater adulthood stature, fat mass, and percent body fat than decrease or stability in weight z-score. Understanding genetic influences on growth rate in a well-nourished, nutritionally stable population may help us interpret the causes and consequences of centile crossing in nutritionally compromised contexts.

Quantitative genetics of cortical bone mass in healthy 10-year-old children from the Fels Longitudinal Study.

The genetic influences on bone mass likely change throughout the life span, but most genetic studies of bone mass regulation have focused on adults. There is, however, a growing awareness of the importance of genes influencing the acquisition of bone mass during childhood on lifelong bone health. The present investigation examines genetic influences on childhood bone mass by estimating the residual heritabilities of different measures of second metacarpal bone mass in a sample of 600 10-year-old participants from 144 families in the Fels Longitudinal Study. Bivariate quantitative genetic analyses were conducted to estimate genetic correlations between cortical bone mass measures, and measures of bone growth and development. Using a maximum likelihood-based variance components method for pedigree data, we found a residual heritability estimate of 0.71 for second metacarpal cortical index. Residual heritability estimates for individual measures of cortical bone (e.g., lateral cortical thickness, medial cortical thickness) ranged from 0.47 to 0.58, at this pre-pubertal childhood age. Low genetic correlations were found between cortical bone measures and both bone length and skeletal age. However, after Bonferonni adjustment for multiple testing, rho(G) was not significantly different from 0 for any of these pairs of traits. Results of this investigation provide evidence of significant genetic control over bone mass largely independent of maturation while bones are actively growing and before rapid accrual of bone that typically occurs during puberty.

Preschool diet and adult risk of breast cancer.

Events before puberty may affect adult risk of breast cancer. We examined whether diet during preschool age may affect a woman's risk of breast cancer later in life. We conducted a case-control study including 582 women with breast cancer and 1,569 controls free of breast cancer selected from participants in the Nurses' Health Study and the Nurses' Health Study II. Information concerning childhood diet of the nurses at ages 3-5 years was obtained from the mothers of the participants with a 30-item food-frequency questionnaire. An increased risk of breast cancer was observed among woman who had frequently consumed French fries at preschool age. For one additional serving of French fries per week, the odds ratio (OR) for breast cancer adjusted for adult life breast cancer risk factors was 1.27 (95% confidence interval [CI] = 1.12-1.44). Consumption of whole milk was associated with a slightly decreased risk of breast cancer (covariate-adjusted OR for every additional glass of milk per day = 0.90; 95% CI = 0.82-0.99). Intake of none of the nutrients calculated was related to the risk of breast cancer risk in this study. These data suggest a possible association between diet before puberty and the subsequent risk of breast cancer. Differential recall of preschool diet by the mothers of cases and controls has to be considered as a possible explanation for the observed associations. Further studies are needed to evaluate whether the association between preschool diet and breast cancer is reproducible in prospective data not subject to recall bias.

Early menarche and the development of cardiovascular disease risk factors in adolescent girls: the Fels Longitudinal Study.

The purpose of this study was to evaluate the influence of menarcheal age on changes in insulin, glucose, lipids, and blood pressure during adolescence and to assess whether body composition modifies this relationship. We examined 391 girls, a subset of Fels Longitudinal Study female participants (8-21 yr of age). Self-reported menarcheal age was classified based on the National Health and Nutrition Examination Survey III distribution, in which early menarche was at the 25th percentile or less (11.9 yr). Age at menarche was examined in relation to measures of body composition [e.g. fat-free mass (FFM) and percent body fat (PBF)], insulin resistance, blood pressure, and lipid profile. The effects of menarcheal age and body composition on cardiovascular disease risk factor changes were analyzed with serial data mixed models. Median menarcheal age was 12.7 yr (range, 9.8-17.0 yr), with 91 girls (23%) classified as early menarche. Girls with early menarche had more deleterious changes in insulin, glucose, blood pressure, FFM, and PBF levels than girls with average or late menarche. Menarcheal age adversely affected cardiovascular disease risk factor changes independent of age and changes in FFM or PBF. Girls with early menarche exhibited elevated blood pressure and glucose intolerance compared with later maturing girls, independent of body composition.

Heritability of calcaneal quantitative ultrasound measures in healthy adults from the Fels Longitudinal Study.

Quantitative ultrasound (QUS) measurements of bone have been reported to predict osteoporotic fracture risk in postmenopausal women and older men. Although many studies have examined the heritability of bone mineral density (BMD), few studies have estimated the heritability of calcaneal QUS phenotypes. In the present study, we examined the genetic regulation of calcaneal QUS parameters in individuals from nuclear and extended families. The study population includes 260 men and 295 women aged 18-91 years (mean+/-SD: 46+/-16 years) who belong to 111 pedigrees in the Fels Longitudinal Study. Three measures of calcaneal structure were collected from both the right and left heel using the Sahara bone sonometer. These measures included broadband ultrasound attenuation (BUA), speed of sound (SOS), and the quantitative ultrasound index (QUI). We used a variance components based maximum likelihood method to estimate the heritability of QUS parameters while simultaneously adjusting for covariate effects. Additionally, we used bivariate extensions of these methods to calculate additive genetic and random environmental correlations among QUS measures. All phenotypes demonstrated statistically significant heritabilities (P<0.0000001). Heritabilities in the right heel (h2+/-SE) were h2=0.59+/-0.10 for BUA, h2=0.73+/-0.09 for SOS, and h2=0.72+/-0.09 for QUI. Similarly, heritabilities for the left heel were h2=0.52+/-0.10, h2=0.75+/-0.10, and h2=0.70+/0.10, respectively. There was evidence for significant genetic and environmental correlations among these six QUS measures. Combinations of QUS measures in the right and left heel demonstrated genetic correlations of 0.94-0.99 and all were significantly different from one indicating at least a partially unique genetic architecture for each of these measures. This study demonstrates that QUS measures of the calcaneus among healthy men and women are heritable, and there are large shared additive genetic effects among all of the traits examined.

Measurement and standardization protocols for anthropometry used in the construction of a new international growth reference.

Thorough training, continuous standardization, and close monitoring of the adherence to measurement procedures during data collection are essential for minimizing random error and bias in multicenter studies. Rigorous anthropometry and data collection protocols were used in the WHO Multicentre Growth Reference Study to ensure high data quality. After the initial training and standardization, study teams participated in standardization sessions every two months for a continuous assessment of the precision and accuracy of their measurements. Once a year the teams were restandardized against the WHO lead anthropometrist, who observed their measurement techniques and retrained any deviating observers. Robust and precise equipment was selected and adapted for field use. The anthropometrists worked in pairs, taking measurements independently, and repeating measurements that exceeded preset maximum allowable differences. Ongoing central and local monitoring identified anthropometrists deviating from standard procedures, and immediate corrective action was taken. The procedures described in this paper are a model for research settings.

Nutritional status assessed from anthropometric measures in the HEMO study.

OBJECTIVE: Anthropometric methods are screening techniques for assessing nutritional stores of fat and lean tissues among persons with renal disease. This report presents cross-sectional baseline data on anthropometric indicators of nutritional status from a group of hemodialysis patients in a multicenter clinical trial, the Hemodialysis (HEMO) Study. DESIGN: The HEMO Study is a prospective, multicenter, randomized, 2 x 2 factorial clinical trial to evaluate the efficacy of the delivered dose of dialysis, defined by Kt/V, and membrane flux in reducing morbidity and mortality in (maintenance) hemodialysis patients. Standardized measures of weight, stature, body mass index (BMI), arm and calf circumference, and triceps and subscapular skinfolds were taken immediately after dialysis. The analytic methods consisted of univariate statistics, including means, standard deviations, and selected percentiles presented as tables of descriptive statistics. Study findings were compared with corresponding national reference data from the Second National Health and Nutrition Examination Survey (NHANES II). PATIENTS: Eligible patients between 18 and 80 years of age on chronic hemodialysis for at least 3 months, receiving hemodialysis 3 times per week and with a residual renal clearance of < 1.5 mL/min were examined. Patients also had to be able to attain an eKt/V of > or = 1.45 in 4.5 hours or an anthropometric volume < 45 to 50 L thus excluding persons with body weights over about 85 kg. The study sample consisted of the first 1,000 randomized patients, 464 men and 536 women; 642 blacks, 318 whites; and 40 of other racial backgrounds out of 1,847 randomized. RESULTS: Differences in nutritional status by sex, race, duration of dialysis, and comorbid disease were found among these patients enrolled in the HEMO Study. In comparison with NHANES II, these hemodialysis patients were, on average, lighter with less adipose and muscle tissue than healthy persons of the same ages. These findings can be indicators of persons with chronic disease. Those with diabetes were overweight based on their BMI values. CONCLUSION: These HEMO Study data provide a clinical reference for the use of these anthropometric indicators in assessing the nutritional status of contemporary hemodialysis patients weighing < 85 kg.

Nutritional status affects quality of life in Hemodialysis (HEMO) Study patients at baseline.

OBJECTIVE: To evaluate associations between frequently used indicators for assessing nutritional status and health-related quality of life in hemodialysis patients after controlling for demographics, comorbidity, and dialysis dose. DESIGN: Survey of 1,387 hemodialysis patients enrolled at baseline in the Hemodialysis (HEMO) Study. Nutritional status indicators included dietary energy intake, equilibrated normalized protein catabolic rate (enPCR), serum creatinine (SCr), serum albumin (SAlb), body mass index (BMI), calf circumference, and appetite. Health-related quality of life was measured by the Medical Outcomes Study Short Form-36 (MOS-SF-36) summary measures: the Physical Component Scale (PCS) and Mental Component Scale (MCS). SETTING: Fifteen clinical sites throughout the United States providing in-center hemodialysis. RESULTS: The mean PCS score was 36.1 +/- 10 SD, lower than normative data in healthy populations. PCS scores were lower among women, whites, and those with diabetes, severe comorbidities, and poor appetites. Appetite, dietary energy intake, SAlb, and SCr were strongly associated with PCS scores even after controlling for demographics and comorbidity. The sum of the parameter estimates for the effects of nutritional status on PCS was large, 7 points or more depending on the individual's nutritional status indicators. The mean MCS score was 49.7 +/- 10.1 SD, similar to scores in healthy populations, but lower among those with severe comorbidities, poor appetites, advanced age, and more years on dialysis. Appetite, age, and years on dialysis were significantly associated with MCS after controlling for other demographics and comorbidity. Dialysis dose did not significantly alter these relationships. CONCLUSION: Easy-to-use indicators for assessing nutritional status (appetite, energy intake, SAlb, and SCr) together are strongly associated with health-related quality of life, even after controlling for comorbidities and dose of dialysis in hemodialysis patients, providing an additional reason for maximizing patients' nutritional status and health.

Statistical effects of varying sample sizes on the precision of percentile estimates.

The present study evaluates the precision of outlying percentile estimates, with age- and sex-associated variations and facilitates decisions needed to revise the current NCHS 1977 Growth Charts with regard to 1) the inclusion of 3(rd) and 97(th) percentiles and 2) the selection of survey data for the construction of the revised growth charts. Simulation was performed to obtain data with distribution characteristics similar to those of The Third National Health and Nutritional Examination Survey (NHANES III) (1988-1991) data. NHANES III consists of a two-phase, 6-year, complex stratified multistage probability cluster, cross-sectional survey conducted from 1988 through 1994 to represent the US noninstitutionalized population. Phase I of the survey consisted of 679 boys and 622 girls in age groups 3, 8, 13, and 18 years. Weight and stature, the body mass index (BMI) (weight/stature(2); kg/m(2)) was calculated. The results show that 1) the precision of the percentile estimates is greater for stature than for weight and BMI, 2) percentiles during the pubertal period are less precise than those during the prepubertal and postpubertal periods for weight and BMI but there is little difference for stature, and 3) percentile estimates are more precise for girls than boys for weight and BMI, but not for stature. The present findings suggest that pooling of NHANES III and earlier National Center for Health Statistics (NCHS) survey data is necessary to achieve reasonable precision for the 3(rd) and 97(th) percentile estimates. Am. J. Hum. Biol. 12:64-74, 2000. Copyright 2000 Wiley-Liss, Inc.

Serial changes in blood pressure from childhood into young adulthood for females in relation to body mass index and maturational age.

This study determines: (1) patterns of change from childhood to young adulthood in body mass index (BMI), systolic blood pressure (SBP), and diastolic blood pressure (DBP), (2) effects of elevated BMI values on changes in blood pressures (BP), (3) extent of tracking for SBP, DBP, and BMI, and (4) prediction of future risk for elevated BP from earlier values. Annual serial BP and BMI data were available for 198 white females, ages 8-22 years, enrolled in the Fels Longitudinal Study. Patterns of change in BMI were described by a random effects model with a time series model for the correlated residuals. Serial BMI measures were differentiated from age-specific means to measure relative individual BMI levels. Serial BP were analyzed using a similar model to the BMI where relative individual BMI levels were included as an explanatory variable. There was a general increasing trend for SBP, DBP, and BMI from 8-22 years, but the rates of increase declined with age. At the same chronological age, early menarche females had a significantly greater BMI mean value than late menarche females. An average increase of 1 kg/m2 in deviation from BMI population means resulted in an average increase of 1.2 mmHg in SBP and 0.6 mmHg in DBP. Having SBP and DBP levels 1 standard deviation above mean levels, relative to females at mean levels, as early as age 9 represents an odds ratio of 2 for exceeding national 75th percentile levels of SBP and DBP at age 21. Am. J. Hum. Biol. 10: 589-598, 1998. © 1998 Wiley-Liss, Inc.