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Biomedical subjects

R N Baumgartner

Publications and source records attributed to R N Baumgartner.

At least 19 recordsLinked to original sources
PubMed1995

Human body composition and the epidemiology of chronic disease.

Obesity and body fat distribution (FD) are established risk factors for chronic diseases. The body mass index (BMI) and the waist/hip circumference ratio (WHR) are used conventionally as indices of obesity and FD in epidemiological studies. Although some general limitations of these indices are recognized, others that affect their use in relative risks for disease are not well recognized. These include effects of sex, ethnicity, and especially age on the relationships between these indices and body composition, which can result in substantial misclassification of obesity and FD. There is considerable variability in body composition for any BMI, and some individuals with low BMIs have as much fat as those with high BMIs. This results in poor sensitivity for classifying levels of body fatness (e.g., too many "false negatives," or overweight individuals classified as not overweight), and relative risks are attenuated across all categories of BMI. A more serious problem, however, is that at different ages the same levels of BMI correspond to different amounts of fat and fat-free mass. Data from the Rosetta Study and the New Mexico Aging Process Study show that older adults have, on average, more fat than younger adults at any BMI, due to the loss of muscle mass with age. As a result, the sensitivity of BMI cutpoints with respect to body fatness decreases with age, and the use of a fixed cutpoint for all ages results in "differential misclassification bias." Taken together, these issues suggest that the increases with age in the prevalences of overweight and obesity, and in the risks for chronic diseases, may be mis-estimated using BMI. Similar issues may affect the use of WHR for estimating prevalences and associated risks of FD. New field methods for estimating body composition are available that can be applied in large, epidemiologic follow-up studies of chronic diseases. These methods will allow epidemiologists to consider, for example, whether it is increased fat, or the replacement of fat-free mass with fat, with age that is associated with risk for chronic disease.

Adipose Tissue↗
PubMed1995

Cross-sectional age differences in body composition in persons 60+ years of age.

BACKGROUND: There is little information for age differences in body composition in elderly people > 65 years of age, especially for those > 80 years. As the proportion of people older than 65 years is expected to nearly double during the next few decades, this information is needed. METHODS: Age differences in body composition and anthropometry were examined in 316 men and women aged 60 to 95 years. Multiple components of body composition were quantified using dual energy X-ray absorptiometry and isotope dilution methods, and expressed in molecular and cellular models. Analysis of variance was used to test for differences between age groups 60 to 70, 71 to 80, and > 80 years in each sex. Body composition components were regressed on age, controlling for knee height, fat-free mass, or total body fat. Age-adjusted correlations were calculated with anthropometric variables. RESULTS: Fat-free mass (FFM), body cell mass (BCM), and appendicular skeletal muscle (ASM) decreased with age in both sexes. ASM decreased relative to FFM in both the men and the women, while BCM decreased relative to FFM in the women only. Total fat mass and percent body fat decreased with age in the women, but not in the men. Body fat distribution did not appear to change with age. Anthropometric indices, muscle area and waist/hip ratio, had low correlations with muscle mass and fat distribution. CONCLUSIONS: "Sarcopenia," or muscle loss, continues to occur into old age, and may have significant impacts on physical function and health status. New anthropometric techniques are needed for assessing muscle loss with age.

Adipose Tissue↗
PubMed1992

Differences in skeletal muscle and bone mineral mass between black and white females and their relevance to estimates of body composition.

This study tested the hypothesis that black females have an increase in skeletal muscle and bone mineral mass compared with white females matched for age (+/- 5 y), weight (+/- 2 kg), height (+/- 3 cm), and menstrual status. Conventional [underwater weighing, whole body 40K counting (WBC), 3H2O dilution] and newly developed (dual-photon absorptiometry) techniques were used to provide ethnicity-independent estimates of body composition in 28 pairs of matched subjects. Black females had greater appendicular skeletal muscle (P less than 0.001), bone mineral (P less than 0.001), and total body potassium (TBK) (P = 0.05) compared with white females. Two classic coefficients used in body composition research [density of fat-free mass (FFM) for underwater weighing and TBK/FFM for WBC] differed significantly (P less than 0.05) between black and white females; currently applied coefficients underestimated fat in black females. This study confirms that black and white females differ in body composition and that errors in fat estimates occur when ethnicity is not accounted for in body composition models.

Absorptiometry, Photon↗
PubMed1992

Prediction of iron absorption based on iron status of female blood donors.

Iron stores were assessed in 27 postmenopausal healthy women who donated five units of blood (approximately 485 mL/unit) over approximately 1 y. The mean (+/- SD) age was 67.7 +/- 4.0 y and the average time between successive blood donations was approximately 10 wk (range 8-30 wk). Steady-state iron stores at entrance were 10.59 +/- 3.88 mg/kg body wt (mean +/- SD) and declined to 1.03 +/- 3.20 mg/kg by the fifth donation. Determination of iron stores was based on biochemical measures of iron status at each donation. Iron intakes were 23.3 +/- 10.1 mg/d. From these data we developed equations that can be used to predict the frequency at which healthy postmenopausal women can donate blood without becoming iron deficient. The ability of elderly women to become successful blood donors depends primarily on initial iron stores, iron intake, and frequency of donation. Women with low steady-state iron stores may be able to donate only two times per year without becoming iron deficient.

Absorption↗
PubMed1992

Appendicular skeletal muscle areas assessed by magnetic resonance imaging in older persons.

Measurements of cross-sectional muscle areas of the upper-arm and mid-thigh from MRI images were compared to corresponding estimates from anthropometric measurements of limb circumferences and skinfold thicknesses in 25 normal, healthy, elderly persons. The anthropometric method significantly overestimated actual muscle areas, and the amount of error increased systematically with level of adiposity. These results agree with those from other, similar studies using CT in younger adults, but indicate that the degree of error is 2 to 3 times greater for elderly persons. At present, there does not appear to be any simple way to "correct" the anthropometric method. Prediction methods may be developed, but these will still produce large errors for some individuals. Alternative approaches are discussed.

Adipose Tissue↗
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

Body composition in elderly people: effect of criterion estimates on predictive equations.

The purposes of this study were to determine whether there are significant differences between two- and four-compartment model estimates of body composition, whether these differences are associated with aqueous and mineral fractions of the fat-free mass (FFM); and whether the differences are retained in equations for predicting body composition from anthropometry and bioelectric resistance. Body composition was estimated in 98 men and women aged 65-94 y by using a four-compartment model based on hydrodensitometry, 3H2O dilution, and dual-photon absorptiometry. These estimates were significantly different from those obtained by using Siri's two-compartment model. The differences were associated significantly (P less than 0.0001) with variation in the aqueous fraction of FFM. Equations for predicting body composition from anthropometry and resistance, when calibrated against two-compartment model estimates, retained these systematic errors. Equations predicting body composition in elderly people should be calibrated against estimates from multicompartment models that consider variability in FFM composition.

Absorptiometry, Photon↗
PubMed1990

Body composition of humans: comparison of two improved four-compartment models that differ in expense, technical complexity, and radiation exposure.

Multicompartment models are of growing importance in the study of body composition in humans. This study compares two improved four-compartment (water, protein, mineral, and fat) models that differ in expense, technological complexity, and radiation exposure. Primary data (from 31 subjects) for the first model were derived by dual-photon absorptiometry, 3H2O dilution, and hydrodensitometry and for the second model by delayed and prompt gamma neutron-activation analysis and 3H2O dilution. Estimates of fat, protein, and mineral from the first model were highly correlated with those from the second model (r = 0.98, 0.72, and 0.94, respectively; all p less than 0.001). The proportions of body weight represented by water, protein, mineral, and fat for the simpler first model (0.532, 0.155, 0.048, and 0.265) were similar to compartment fractions provided by the more complex and costly second model (0.532, 0.143, 0.046, and 0.279). Multicompartment body composition models can thus be developed from increasingly available techniques that compare favorably with similar results derived from limited-access instrumentation.

Absorptiometry, Photon↗
PubMed1990

Evaluation of accuracy and reliability of calipers for measuring recumbent knee height in elderly people.

Height measurements in elderly individuals are frequently not feasible and stature must be estimated from knee height. This study compared the accuracy and reliability of a knee-height caliper developed by Ross Laboratories with Mediform and GPN models. Two observers measured 40 elderly ambulatory volunteers with each caliper. Knee height was measured on the left leg from the heel to a point 5 cm proximal to the patella. Intracaliper reliability was similar. Mean absolute differences between repeated measurements ranged from 0.17 to 0.25 cm, technical errors of the estimate ranged from 0.16 to 0.26 cm, and coefficients of reliability exceeded 0.99 for each model. Equations based on knee height predicted subjects' stature to +/- 2.3 cm, an amount unlikely to substantially impair height-based nutrition indices. This comparatively inexpensive caliper was as accurate and reliable as more expensive commercially available models and may be recommended as an alternative to the other calipers.

Age Factors↗
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↗
PubMed1989

Estimation of body composition from bioelectric impedance of body segments.

The hypothesis that body composition can be estimated accurately from measurements of the length and resistance of the body segments was tested. Weight; stature; whole-body resistance; and the resistances, lengths, and circumferences of the leg, trunk, and arm were measured for 135 white men and women aged 18-58 y. Fat-free mass (FFM) and percent body fat (%BF) were obtained from densitometry. The resistance of the whole body was determined almost entirely by the resistances of the arm and the leg. The accuracy of the prediction of FFM from arm length2/arm resistance and of %BF from weight x arm resistance/arm length2 was only marginally less than that obtained by using whole-body measurements. Thus, measurements of the resistance and length of the arm can be used in place of the whole-body methods for estimating body composition from bioelectric impedance.

Adipose Tissue↗
PubMed1989

Status of anthropometry and body composition data in elderly subjects.

Understanding the normal changes in the body and its composition with increasing old age and their health implications are important to the health care and nutritional support of elderly subjects. Distribution statistics for selected body measurements of persons aged 65-80 y are available from the national health surveys. Recumbent anthropometric techniques and B-mode ultrasound may be applicable to measuring those greater than 80 y who have difficulty standing or are chair- or bedfast. The problems of estimating body composition in elderly subjects could be improved by using a four-compartment model. Noninvasive methods, such as anthropometry and bioelectric impedance, could be used to predict body composition in elderly subjects if appropriate equations were available and validated against direct methods. The most pressing need is for the development of suitable reference data for anthropometry and body composition in large representative samples of black, white, Hispanic and Oriental elderly persons in the US.

Aged↗
PubMed1989

Associations between plasma lipoprotein cholesterols, adiposity and adipose tissue distribution during adolescence.

Associations between changes with age in 'fat pattern' and lipoprotein cholesterols during adolescence were analyzed using serial data for 214 boys and girls between 11 and 18 years of age who were participants in the Fels Longitudinal Study. The logarithms of the ratios of the subscapular to lateral calf and the subscapular to triceps skinfold thicknesses increased with age in each sex, but the increases were greater in the boys. Plasma levels of HDL cholesterol decreased with age in the boys, but not in the girls. Within annual age-groups, neither plasma LDL cholesterol nor HDL cholesterol were correlated with percent body fat or either of the 'fat pattern' indices in each sex. In 51 children with serial data 5 years apart, changes with age in HDL cholesterol had significant negative correlations with changes in the 'fat pattern' indices that were independent of changes in percent body fat in the boys, but not in the girls. In the girls, changes in the indices were due to greater increases in the thickness of the subscapular skinfold than in the triceps and lateral calf skinfolds as percent body fat increased and were not associated with changes in levels of plasma lipoproteins. In the boys, changes in the 'fat pattern' indices were due to decreases in the thicknesses of the lateral calf and triceps skinfolds and increases in thickness of the subscapular skinfold as percent body fat decreased. These results suggest that a redistribution of adipose tissue occurs during adolescence in boys and is associated with decreases in HDL cholesterol.

Adipose Tissue↗