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Biomedical subjects

W C Chumlea

Publications and source records attributed to W C Chumlea.

At least 55 records · Page 3Linked to original sources
PubMed1997

Age- and maturity-related changes in body composition during adolescence into adulthood: the Fels Longitudinal Study.

OBJECTIVES: To examine patterns of change in total body fat (TBF), percent body fat (%BF), and fat-free mass (FFM), from 8-20 y of age and the effect of rate of skeletal maturation. To determine the degree of tracking of body composition for individuals from childhood into adulthood. RESEARCH DESIGN: Annual serial data for TBF, %BF and FFM from underwater weighing using a multicomponent body composition model were collected from 130 Caucasian males and 114 Caucasian females between 1976 and 1996. Rate of maturation was defined as FELS skeletal age (SA) less chronological age (CA). Random effects models were used to evaluate general patterns of change and tracking of individual serial data over the 12 y age range. RESULTS: Changes in TBF followed a quadratic model for males and for females with declining rates of change. Changes for %BF followed a cubic model for males and females. General patterns of change for FFM followed a cubic model for males and a quadratic model for females. TBF for males and females increased with age, but the rates of change declined with age. %BF for females increased from age 8-20 y. For males, %BF increased with age, but the positive rates of change declined and became a negative when aged about 13 y and reached a minimum at about the age of 15 y. The rate of change for %BF increased thereafter. FFM for males and females increased with age, but the rates of change decreased with age. The extent of tracking is inversely related to the length of the time interval. At the same age, rapidly-maturing children have significantly larger amounts of TBF, %BF and FFM then slow-maturing children. Tracking in body composition for individuals persisted from childhood to adulthood. CONCLUSIONS: (1) There are gender-associated differences in these patterns of change for %BF and FFM but not for TBF; (2) TBF, %BF and FFM increased with increased rates of maturation; (3) significant tracking in body composition for individuals persists from childhood to adulthood.

Adolescent↗
PubMed1996

Weight-for-length reference data for preterm, low-birth-weight infants.

OBJECTIVE: To provide weight-for-length reference data for preterm, very-low-birth-weight and low-birth-weight infants. DESIGN: Data from 867 infants (428 boys and 439 girls) in the Infant Health and Development Program, who each were preterm and who had a low birth weight, were used to develop weight-for-length reference data. The Infant Health and Development Program is a national, randomized, clinical trial that included various ethnic groups at 8 sites. At each site, sampling ensured that two thirds of the infants in the study weighed 2000 g or less and that one third of the infants weighed from 2001 to 2500 g at birth. Infants were examined at birth, at 40 weeks' postconception, and at 4, 8, 12, 18, 24, 30, and 36 months' gestation-adjusted age. Gestation-adjusted age was used instead of chronological age from birth to correct for the degree of prematurity. RESULTS: Weight-for-length percentiles are given for lengths at 3-cm intervals ranging from 48 to 100 cm. These percentiles are sex specific and are for a very-low-birth-weight group (< or = 1500 g) and a low-birth-weight group (1501-2500 g). CONCLUSIONS: These data should assist screening for deviations from normal growth and may aid in the early detection of failure to thrive and excessive weight gain in infancy.

Anthropometry↗
PubMed1996

Mechanical and physiologic modifiers and bioelectrical impedance spectrum determinants of body composition.

Fat-free mass and total and percentage body fat were determined by dual-energy X-ray absorptiometry (DXA) and total-body and segmental impedance measures were taken at 16 frequencies from 5 to 1300 kHz in a sample of white men and women aged 18-30 y. Plots of total-body and segmental impedance against frequency for each individual indicated that the general shape of these curves was described by the same mathematical function consisting of three components-ai, bi, and ci,-that contain information derived from the individual measurements of impedance summarized across the spectrum of current frequencies. Total-body and segmental multifrequency impedance were significantly correlated with hemoglobin, hematocrit, and serum sodium, potassium, creatinine, and osmolality. Regression models of body composition with total-body or segmental impedance measures at discrete frequencies or the impedance spectrum variables were similar to corresponding findings for impedance models at 50 kHz. The segmental impedance spectrum variables for total and percentage body fat and the ratios of low- to high-frequency impedance from the trunk were significantly associated with total body fatness as measured by DXA.

Absorptiometry, Photon↗
PubMed1996

Use of statistical methods to estimate body composition.

Epidemiologic investigations of chronic diseases in relation to body composition require large samples. This necessitates simple, reliable, and portable measures of body composition. Bioelectrical impedance analysis (BIA) variables and selected anthropometric characteristics are frequently used to predict body composition for groups or individuals when the application of sophisticated methods is not practical. We address statistical issues pertinent to the formulation of prediction equations for body composition from BIA measures and anthropometry, and factors associated with the accuracy and precision of the prediction equations.

Body Composition↗
PubMed1995

Techniques of assessing muscle mass and function (sarcopenia) for epidemiological studies of the elderly.

For epidemiological studies, reliable and valid measurements or indices of muscle mass are needed to screen for those elderly persons at risk for sarcopenia, and to determine the prevalence of these conditions on a national level. The methods more suitable for field or epidemiological settings are anthropometry, bioelectrical impedance, and grip strength. These field methods, while reliable, have limited demonstrated validity in their application to the elderly and are restricted by the limited functional capabilities of the elderly, which decrease with age. Epidemiological studies of the elderly need to include sufficient numbers of persons of different ethnic backgrounds, and at the older ages. For an epidemiological study of the elderly today, one also needs to select the categories of elderly persons to be included in such studies: healthy, sick, very old, handicapped, level of functional status, etc., because relationships among variables can have different statistical and biological associations. Future work should be directed at improving the design and methodology of epidemiological and serial studies so as to maximize the numbers and categories of elderly persons who can be studied.

Age Factors↗
PubMed1994

Prediction of stature from knee height for black and white adults and children with application to mobility-impaired or handicapped persons.

OBJECTIVE: No adequate methods exist for predicting stature to help assess the growth of handicapped (including mobility-impaired) children or to help in developing indexes of obesity or equations for estimating basal energy expenditure for adults. In this project, equations were developed to predict stature in white and black adults and children from nationally representative samples for application to mobility-impaired and handicapped persons. SAMPLES: Samples of healthy adults (n = 5,415) and children (n = 13,821) were selected from cycles I, II, and III of the National Health Examination Survey (NHES) conducted by the National Center for Health Statistics from 1960 to 1970. Balanced validation and cross-validation groups were created with regard to age, ethnic group, and sex. OUTCOME MEASURES: The NHES is the only national survey that contains body measurements biologically appropriate for predicting stature. These measurements include stature, sitting height, knee height, and buttocks to knee length. STATISTICAL ANALYSIS: Equations were computed from an all-possible-subsets of weighted regression procedure to select the predictor variables in the validation group based on the values of R2 and the root mean square error. RESULTS: Knee height predicted stature for white and black men, but the predictor variables for white and black women were knee height and age. For predicting stature in children 6 to 18 years of age, the predictor variable was knee height for all children. APPLICATIONS: The equations presented here were developed for use with mobility-impaired or handicapped persons, but the measurements were collected from ambulatory people by means of standard techniques. The use of recumbent anthropometric data from mobility-impaired or handicapped persons in the equations will expand the errors of prediction over those presented in this report. The standard error for a person is a guide to the range of probability within which a predicted value can occur.

Adolescent↗
PubMed1994

Body composition in white adults by dual-energy x-ray absorptiometry, densitometry, and total body water.

Percent body fat (%BF) and fat-free mass (FFM) were determined in 151 adults from the Fels Longitudinal Study by total body scans with a Lunar DPX (DXA), by underwater weighing and residual lung volume with a two-compartment model using body density (Dens), and total body water (TBW) using deuterium dilution. For the DPX, the medium scan mode ensures precision up to 100 kg body wt and for a ratio of weight to stature < or = 0.7214. Because of these specifications, 15% (n = 23) of the original sample of 151 were excluded. Results for 78 women and 50 men are presented. %BFTBW was significantly (P < 0.05) less than %BFDens in women (mean difference 2.7 +/- 4.2%) and %BFDXA in men (mean difference 2.2 +/- 4.3%). No other significant intermethod differences were observed for %BF and FFM estimates. Pairwise regressions showed the lowest SEEs for %BFDens regressed vs %BFDXA (2.3% for men, 3.2% for women) and for FFMDens vs FFMDXA (2.2 kg for men, 1.9 kg for women). For each sex, reliability analyses and limits of agreement for body composition estimates showed less agreement between TBW and either Dens and DXA than between Dens and DXA.

Absorptiometry, Photon↗
PubMed1994

The predictive value of childhood body mass index values for overweight at age 35 y.

Larger body mass index values (BMI in kg/m2) are associated with increased morbidity and mortality in adulthood and there are significant correlations between BMI values in childhood and in adulthood. The present study addresses the predictive value of childhood BMI for overweight at 35 +/- 5 y, defined as BMI > 28 for men and > 26 for women. Analyses of data for 555 white children indicated that overweight at 35 y can be predicted from BMI at younger ages. The prediction is excellent at age 18 y, good at 13 y, but only moderate at ages younger than 13 y. For 18-y-olds with a BMI value exceeding the 60th percentile, the odds of overweight at 35 y are 34% for men and 37% for women. A clinically applicable method is provided to assign an overweight child to a group with a known probability of high BMI values in adulthood.

Adolescent↗
PubMed1994

Bioelectrical impedance and body composition: present status and future directions.

Single-frequency bioelectrical impedance analyzers used to assess body composition are being replaced by multiple-frequency analyzers. At low frequencies, the current flows primarily through extracellular fluids; at high frequencies, it completely penetrates all body tissues. Measures of bioelectrical impedance at multiple frequencies can differentiate total and extracellular fluid compartments in the body. This has considerable value for assessing clinical and nutritional status. Impedance measures at a single frequency contain only a small window of the available impedance spectrum information, which may explain the difficulty in discriminating among individuals. The impedance spectrum and its analysis may provide a much clearer picture of individual differences in body water and body composition. With increasing clinical uses of bioelectrical impedance in individuals and sample populations, the use of multiple-frequency impedance may help to elucidate differences that are not discernible with single-frequency impedance.

Body Composition↗
PubMed1993

Serial analysis of plasma lipids and lipoproteins from individuals 9-21 y of age.

Total cholesterol (TC) and low-density- (LDL-C) and high-density-lipoprotein cholesterol (HDL-C) concentrations were recorded annually from 9 to 21 y of age to study tracking and predictive values for adulthood lipid concentrations associated with cardiovascular disease. The tracking coefficients for TC and LDL-C were congruent to 0.7 for 4-, 6-, and 12-y intervals, indicating good predictive value at ages 9-11 y for risk of elevated concentrations at ages 19-21 y. Tracking of HDL-C was less marked but the patterns were similar. The risk ratios for high concentrations at 19-21 y were 3.8 for TC, 2.6 for LDL-C, and 4 for HDL-C for 9-y-olds with values of 5.17 mmol/L for TC, 3.36 mmol/L for LDL-C, and 0.90 mmol/L for HDL-C, relative to 9-y-olds with values of 4.65 mmol/L for TC, 2.84 mmol/L for LDL-C, and 1.29 mmol/L for HDL-C.

Adolescent↗
PubMed1993

Bioelectric and anthropometric assessments and reference data in the elderly.

Most studies using bioelectric impedance have estimated the volume of total body water, fat-free mass and on occasion extracellular fluid volume using whole-body resistance and reactance. However, the validity of bioelectric impedance has not been established for the elderly except in small samples of limited age ranges. The estimation of whole-body composition from impedance of body segments may be an alternative method that can be applied to many chair- and bedfast elderly patients. Also, measures of bioelectric impedance at lower and higher frequencies than 50 kHz are reported to differentiate the proportions of intra- and extracellular fluid volumes, and this could also provide important information about fluid quantities and balances in the elderly. Distribution statistics for body measurements for persons 65-85 y of age are available from the national health surveys and large clinical studies but reference data for persons > or = 80 y are sparse. Some reference data may be from groups that are not representative of the elderly because the samples were from cohorts older than elderly persons living today and significant group and racial differences existed among these as children and adults. These differences may have increased interindividual variances among the elderly. Suitable reference data for the present generations of elderly in the United States will be available with the culmination of NHANES III after 1994, but limited reference data for elderly persons up to 90 y of age have been published.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Equations for predicting stature in white and black elderly individuals.

In an anthropometric nutritional assessment, elderly individuals are frequently unable to assume the positions needed for many measurements. This is especially true for stature, which is affected by mobility and skeletal deformities, and as a result measurements may be unreliable and inaccurate. An alternative is to use a surrogate value of stature. We developed predictive equations using data from elderly subjects in Cycle I of the National Health Examination Survey (NHES). The developed equations were cross-validated using two separate independent and more contemporary samples of elderly White men and women. The possible predictor variables were knee height and buttocks-knee length in the men and knee height and age in the women. For both the men and the women, the majority of the variance in stature was accounted for by knee height. Selected equation models were cross-validated, and a single equation was recommended for each elderly group that included knee height rather than buttocks-knee length as predictor variables. This selection was based upon the performance of the equations, and also upon the practical ease of collecting the possible predictor variables. Included with the recommended equations are the RMSEs and the standard error for predicting stature for an individual (SEI). The successful application of the recommended equations with two recent sets of elderly persons indicates the current utility of the recommended equations in White elderly Americans.

Aged↗