PubMed Health⌕ Search

Biomedical subjects

W C Chumlea

Publications and source records attributed to W C Chumlea.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1992

Fat distribution and blood lipids in a sample of healthy elderly people.

The cross-sectional sample consisted of data for 41 white men and 63 white women, 67-92 years of age who were healthy volunteer participants in the Aging Process Study at the University of New Mexico School of Medicine in Albuquerque, New Mexico. The variables consisted of anthropometric measures of body fatness, blood lipids and blood pressures. Correlations were computed between principal component scores, ratios of body circumferences, W/S2, blood lipid values and blood pressures for each sex. In the men, the significant correlations were of the abdomen/hip and abdomen/thigh ratios with W/S2, and the principal component scores with HDL cholesterol, triglyceride and systolic blood pressure. In the women, the abdomen/hip ratio had a low negative correlation with HDL cholesterol but a low positive correlation with triglyceride levels. The principal component scores also had low correlations with blood pressure and triglycerides. Multiple regressions were used to determine further associations between risk factors and fat distribution indices. In the men, the relationships of age and levels of body fatness with HDL cholesterol were much stronger and more complex than those with triglyceride or systolic blood pressure. In the women, only HDL cholesterol and triglyceride were associated with abdomen/hip ratio after removing the effects of overall fatness. The present findings indicate that a large abdominal circumference, implying a correspondingly large internal adipose tissue deposit, produces negative health alterations in blood lipid levels in this sample of elderly individuals. In younger adults, these changes are considered to increase the risk for cardiovascular disease.

Adipose Tissue↗
PubMed1991

Reference data on gains in weight and length during the first two years of life.

Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.

Age Factors↗
PubMed1991

Patterns of change in weight/stature2 from 2 to 18 years: findings from long-term serial data for children in the Fels longitudinal growth study.

Serial weight/stature2 (W/S2) data recorded semi-annually from 2 to 18 years in the Fels longitudinal study were analyzed to establish an approach for the investigation of long-term serial changes in body fatness during childhood and adolescence in individuals. To describe patterns of change in body fatness during childhood and adolescence, a family of mathematical models was fitted to individual serial W/S2 data recorded from 250 boys and 246 girls. The selected models fitted the W/S2 data well as judged by the root mean square errors. Based on the fitted models, variables representing patterns of change in an individual were derived. These included estimated value of W/S2 at 2 years of age (W/S(2)2yr), minimum value of W/S2 (W/S2min), age at minimum value of W/S2 (Amin), maximum velocity of W/S (Vmax), age at maximum velocity of W/S2 (AVmax), maximum value of W/S2 (W/S2max), and age at maximum value of W/S2 (Amax). There were highly significant correlations between observed W/S2 at 18 years and all the derived variables except AVmax indicating, for example, that in both sexes about 25 percent of the variation in W/S2 at 18 years could be explained by when Amin occurs or by the value of W/S2min. The negative correlations (r = -0.5) between Amin and W/S2 at 18 years suggested that the earlier children reach their nadir in W/S2, the earlier they began to increase in adiposity and the fatter they were at 18 years. Likewise, the positive correlations (r approximately 0.3 and 0.5, respectively) between the W/S(2)2yr or W/S2min and W/S2 at 18 years indicated that increased childhood adiposity may lead to increased adult adiposity.

Adipose Tissue↗
PubMed1990

Bioelectric impedance methods for the estimation of body composition.

The present use of bioelectric impedance is based upon the greater electrolyte content and conductivity of fat-free mass (FFM). The limitation of the whole body impedance approach may be the use of S2/R as an index of the conductive volume of the body. The use of body lengths that closely resemble the actual length of the conductor rather than stature can improve predictions of FFM. Theoretically, the specific resistivity approach to bioelectric impedance also provides a means of circumventing this problem. Another alternative is the estimation of whole body composition or the composition of body segments from measurements of the lengths and resistances of the segments and the use of the phase angle of the whole body and or body segments. Possible alternative methods for the use of bioelectric impedance would be the measurement of the composition of body segments, the determination of specific resistivities so that estimates of FFM can be calculated without the need for regression equations and the determination of the use of different current frequencies in measuring body composition with bioelectric impedance.

Body Composition↗