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Biomedical subjects

A F Roche

Publications and source records attributed to A F Roche.

At least 19 recordsLinked to original sources
PubMed1992

Serial changes in blood pressure from adolescence into adulthood.

High blood pressure is an established risk factor for cardiovascular disease outcomes in adulthood. Furthermore, numerous longitudinal studies of blood pressure in childhood with length of follow-up from 1 to 17 years indicate that blood pressure levels track over the short term. This study addresses the question of the predictive value of childhood blood pressure readings for adult levels, using repeated blood pressure determinations from a sample of 501 participants in the Fels Longitudinal Study, an ongoing cohort study in southwestern Ohio that began in 1929. A damped autoregressive model indicated tracking correlations from 0.39 (4-year intervals) to 0.24 (20 years) for systolic pressure and 0.37 (4 years) to 0.20 (20 years) for diastolic pressure. These results indicate that tracking of blood pressure persists from age 13 years to age 40 years, which translates into moderate levels of relative risk for adult hypertension (diastolic pressure above 90 mmHg) for adolescents with high normal blood pressure. The estimated relative risks of hypertension at age 35 for white 15-year-olds with a true mean diastolic pressure of 80 mmHg were 1.9 for males and 2.6 for females, relative to 15-year-olds with a true diastolic pressure of 60 mmHg.

Adolescent↗
PubMed1992

Bioelectrical impedance estimation of fat-free body mass in children and youth: a cross-validation study.

The purposes of this study were to develop and cross-validate the "best" prediction equations for estimating fat-free body mass (FFB) from bioelectrical impedance in children and youth. Predictor variables included height2/resistance (RI) and RI with anthropometric data. FFB was determined from body density (underwater weighing) and body water (deuterium dilution) (FFB-DW) and from age-corrected density equations, which account for variations in FFB water and bone content. Prediction equations were developed using multiple regression analyses in the validation sample (n = 94) and cross-validated in three other samples (n = 131). R2 and standard error of the estimate (SEE) values ranged from 0.80 to 0.95 and 1.3 to 3.7 kg, respectively. The four samples were then combined to develop a recommended equation for estimating FFB from three regression models. R2 and SEE values and coefficients of variation from these regression equations ranged from 0.91 to 0.95, 2.1 to 2.9 kg, and 5.1 to 7.0%, respectively. As a result of all cross-validation analyses, we recommend the equation FFB-DW = 0.61 RI + 0.25 body weight + 1.31, with a SEE of 2.1 kg and adjusted R2 of 0.95. This study demonstrated that RI with body weight can predict FFB with good accuracy in Whites 10-19 yr old.

Adipose Tissue↗
PubMed1991

Measures of body composition. Their relationship to blood pressure and use in epidemiologic research.

The association between "overweight" and increased risk of high blood pressure has long been recognized. The quantification of overweight into various aspects of body composition and the relationships of these aspects to blood pressure remain important areas of current research. The manner in which adipose tissue is distributed over the body is proving to be another important risk factor. Methodologies for assessing body composition include a variety of approaches commonly used in epidemiologic studies, ranging from simple indices (e.g., body mass index) to estimation of total body fat mass from equations based on skinfolds and other anthropometry, to newer approaches incorporating bioelectric impedance. Refined laboratory methods for assessing body composition are important in the study of small groups and in the development of predictive equations. These refined methods include the traditional approaches of hydrostatic weighing and K40 determinations, as well as newer improvements on these techniques incorporating estimates of bone mineral content and total body water. Other new sophisticated methodologies include dual-energy x-ray absorptiometry and nuclear magnetic resonance imaging. The approach to assessing body composition may vary among age groups; methodologies applicable to children may not work for the elderly.

Blood Pressure↗
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

Differences between the hand-wrist and the knee in assigned skeletal ages.

Skeletal ages were assessed for 4,902 pairs of hand-wrist and knee radiographs of children aged 2-17 years. The FELS method was used to assess the hand-wrist, and the RWT method was used to assess the knee. These methods have the same conceptual and statistical basis. The mean absolute differences, within age- and sex-specific groups, ranged from 0.34 to 0.87 years. The SD of the differences ranged from 0.31 to 0.68 years and, like the means, tended to increase with age until about 8-11 years. The means and SD were generally larger for the boys than for the girls, except after 14 years. Within age- and sex-specific groups, the maximum absolute differences were from 1.45 to 2.99 years. These maximum differences changed irregularly with age but tended to increase until 11 years in the boys and 9 years in the girls. These large absolute differences between the skeletal ages of the hand-wrist and the knee cannot be explained completely by the effects of observer errors. The means of the relative (signed) differences between the skeletal ages of the hand-wrist and the knee were all close to zero, but there was a wide range within age- and sex-specific groups. These skeletal ages of the hand-wrist and the knee are not interchangeable. The 95th percentiles of the absolute differences show that, in at least 5% of children, the choice of the area for skeletal age assessment will markedly influence the evaluation of individuals. They also demonstrate that descriptions of populations based on distributions of skeletal ages from one part of the skeleton may be misleading.

Adolescent↗
PubMed1989

Alternative genetic models for the inheritance of the phenylthiocarbamide taste deficiency.

Pedigree segregation analysis was used to examine several one- and two-locus models of the inheritance of phenylthiocarbamide (PTC) taste deficiency that extend the traditional one-locus recessive model by the addition of either another allele or another locus, and in some cases predict two types of nontasters. These models allow nontaster by nontaster matings to produce taster offspring, consistent with our data and several previous studies which use the Harris and Kalmus [Annals of Eugenics 15:24-32, 1949] dilution method. The models fit our data set of 1,152 individuals from 120 families significantly better than the one-locus recessive model. The best fit was obtained with a two-locus model in which one locus controls PTC tasting and the other locus controls a more general taste ability. This model is consistent with research on the physiology of PTC tasting and with results from genetic linkage studies. Further study is suggested to evaluate better the accuracy of the proposed model.

Alleles↗
PubMed1989

Weight and recumbent length from 1 to 12 mo of age: reference data for 1-mo increments.

Serial data from 504 infants were used to develop reference data for 1-mo increments in weight and recumbent length by fitting a family of three-parameter mathematical functions to the serial data for each individual. The percentiles for status and for increments tended to be larger for the boys than for the girls except for the lower percentiles of increments for weight after 9-10 mo and for recumbent length after 8-9 mo. These data can be used to assess growth in white or black infants whether they are breast-fed or formula-fed. These new data will allow earlier evaluation of growth velocity than the reference data for 3- and 6-mo increments that were available previously. This can lead to the earlier initiation of diagnostic procedures and treatment. The present data should be useful also in research studies.

Body Height↗
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

Fat-free mass in children and young adults predicted from bioelectric impedance and anthropometric variables.

Fat-free mass (FFM) values calculated from densitometry by using a multicomponent model were significantly (p less than 0.05) larger than those from the Siri two-component model (465 males, 441 females), especially in children and females. The multicomponent model assumes the density of FFM varies by age and sex because of differences in its constituents. With FFM values from the multicomponent model as the dependent variable and impedance and anthropometry as the independent variables, prediction equations were derived by all possible subsets of regression (140 males, 110 females). These equations had RMSEs of 2.2-2.3 kg and CVs of 5.0-5.8%. Cross-validation results were excellent for young adults but less satisfactory for children for whom a different calf skinfold had been measured. The selected equations are applicable to healthy white individuals aged 7-25 y.

Adipose Tissue↗
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↗
PubMed1988

Reference data for head circumference and 1-month increments from 1 to 12 months of age.

Serial head circumference measurements in 462 participants in the Fels Longitudinal Study were used to develop reference data for ages 1 to 12 months. We used a three-parameter mathematical function to model the serial head circumference data for each individual and estimated head circumference at 1-month intervals. Reference data for selected percentiles of head circumference status and 1-month increments were calculated from the estimated head circumferences. These reference data are presented in tables and charts for use in testing hypotheses about group differences or to monitor changes within individuals.

Cephalometry↗
PubMed1988

Late growth changes in the craniofacial skeleton.

Analysis of serial radiographs shows that growth in the cranial base and in the mandible continues into the third decade. Variations in rate and timing are great, and the total increments after 18 years are usually small.

Adolescent↗