Longitudinal changes in calcaneal quantitative ultrasound measures during childhood.

UNLABELLED: This longitudinal study examined how calcaneal quantitative ultrasound (QUS) measures change during childhood while taking into account skeletal maturation, body mass index (BMI), and physical activity. The study reported sex differences in QUS growth curves and an inverse relationship between BMI and speed of sound (SOS) measures. INTRODUCTION: The aim of this study was to examine how calcaneal QUS parameters change over time during childhood and to determine what factors influence these changes. METHODS: The study sample consisted of a total of 192 Caucasian children participating in the Fels Longitudinal Study. A total of 548 calcaneal broadband ultrasound attenuation (BUA) and SOS observations were obtained between the ages of 7.6 and 18 years. The best fitting growth curves were determined using statistical methods for linear mixed effect models. RESULTS: There are significant sex differences in the pattern of change in QUS parameters (p < 0.05). The relationship between QUS measures and skeletal age is best described by a cubic growth curve in boys and a linear pattern among girls. Boys experience their most rapid growth in BUA and SOS in early and late adolescence, while girls experience constant growth throughout childhood. Adiposity levels were significantly associated with the changes in SOS among boys (p < 0.001) and girls (p < 0.01), indicating that children with higher BMI are likely to have lower SOS over time compared to children with lower BMI. For girls, physical activity levels showed positive associations with changes in QUS measures (p < 0.05). CONCLUSION: This study documents significant sex differences in the pattern of change in QUS measures over childhood and adolescence. Our study also shows significant influences of adiposity and physical activity on the pattern of change in QUS measures during childhood.

The first seriatim study into old age for weight, stature and BMI: the Fels Longitudinal Study.

PURPOSE: To document the serial status of measures of weight, stature and BMI from birth into old age. METHODS: Longitudinal measures of weight, stature and BMI were taken from birth to 76 years of age for 5 men and 7 women as part of the Fels Longitudinal Study. RESULTS: Sex-specific plots of means for weight, stature and BMI are presented that describe the changes and sex differences in these measurements between birth (or the first year of life) into old age. These serial data demonstrate a continuous increase in body weight through much of adulthood and a small decline in stature starting in late middle age. The plots for BMI indicate the early onset of overweight and subsequent obesity early in adulthood and its continuance into old age for men and women. CONCLUSIONS: These are the first plots of serial means for weight, stature and BMI measured from the same group of individuals from birth into old age. These findings demonstrate the changes in these measurements through childhood and maturity into old age. Similar data are needed for individuals from other racial/ethnic groups and countries in order to understand the aging process better.

A review of body water status and the effects of age and body fatness in children and adults.

BACKGROUND: Most investigations of TBW, ECW and body composition and reports of their intra-body relationships were published prior to 1980. Distributional TBW and ECW relationships within the body have been considered fixed, but there was evidence these relationships were affected by the level of fatness. Body composition models based on past findings and assumptions could produce inaccurate estimates when the majority of the population is overweight to obese. METHODS: TBW and ECW volumes, their proportions of body weight, FFM and percent body fat and associations with age are considered in U.S. children and adults. This review focuses on studies reporting measured body water volumes from large samples except for the national predicted values from NHANES III. RESULTS: Measured TBW volumes for children and adults are almost exclusively from whites with the exception of the estimated values from NHANES III for non-Hispanic black and Mexican-Americans. Mean adult TBW volumes are as much as 9 liters greater than those reported prior to 1980. Low mean percentages of TBW%WT reflect the greater level of adiposity in children and adults, and this level of adiposity affects the value of TBW% FFM. Mean ECW volumes for white adults are 10 to 12 liters larger than those reported previously. With greater fatness in adults, ECW%TBW has increased to near 60%, and this implies that a calculation of FFM based on 73% and an ECW%TBW of 25-45% could produce an overestimation but more important clinically an underestimation of body fatness. CONCLUSION: There is inadequate timely information on measured total and extra-cellular water volumes for the population. Available data indicate a coincident increase in body water with overweight and obesity, and a shifting in the proportion of ECW in TBW. Clinical and pharmacological treatments based upon past assumptions of body water volumes, proportions and relationships could produce inaccurate estimates.

Quantitative genetic analysis of blood pressure reactivity to orthostatic tilt using principal components analysis.

Blood pressure (BP) reactivity to orthostatic tilt may be predictive of cardiovascular disease. However, the genetic and environmental influences on BP reactivity to tilt have not been well examined. Identifying different influences on BP at rest and BP during tilt is complicated by the intercorrelation among multiple measurements. In this study, we use principal components analysis (PCA) to reduce multivariate BP data into components that are orthogonal. The objective of this study is to characterize and examine the genetic architecture of BP at rest and during head-up tilt (HUT). Specifically, we estimate the heritability of individual BP measures and three principal components (PC) derived from multiple BP measurements during HUT. Additionally, we estimate covariate effects on these traits. The study sample consisted of 444 individuals, distributed across four large families. HUT consisted of 70 degrees head-up table tilting while strapped to a tilt table. BP reactivity (deltaBP) was defined as BP during HUT minus BP while supine. Three PC extracted from the PCA were interpreted as 'general BP' (PC1), 'pulse pressure' (PC2) and 'BP reactivity' (PC3). Variance components methods were used to estimate the heritabilities of resting BP, HUT BP, deltaBP, as well as the three BP PC. Significant (P<0.05) heritabilities were found for all BP measurements, except for systolic deltaBP at 1 and 3 min, and diastolic deltaBP at 2 min. Significant genetic effects were also found for the three PC. Each of these orthogonal components is significantly influenced by somewhat different sets of covariates.

Dosage of the maternal effect gene associated with the tumorous-head abnormality in Drosophila melanogaster.

The penetrance of tuh-3 observed in the progeny of triploids with two doses of tuh-1 was not statistically different from that occurring in the progeny of their diploid sisters with two doses. A higher penetrance was observed in the progeny of triploids with three doses of tuh-1 than in the progeny of their diploid sisters with two doses. These observations suggest that the maternal effect responsible for increasing the penetrance of tuh-3, the gene causing the tumorous-head abnormality, is caused by a specific gene product of tuh-1, the maternal-effect allele. In addition there is probably a maternal-effect threshold, lying between amounts produced by one and two doses of tuh-1, below which no increased penetrance of tuh-3 is observed.

Blood pressure changes during adolescence and subsequent adult blood pressure level.

Serial data were analyzed for blood pressure recorded between the ages of 9 to 18 years for 278 children and for a subset of this group whose blood pressure was measured at the age of 30 +/- 5.0 years (n = 93). Blood pressures were measured by auscultation over the antecubital fossa with the participant seated. Systolic blood pressure was recorded when the first sound was heard, and diastolic blood pressure was recorded when all sounds disappeared (fifth phase). A linear regression model was fitted to the data for each individual, and adjustments were made for regression toward the mean using maximum likelihood procedures. There were no significant correlations between the estimated initial values of blood pressure and the rate of change from 9 to 18 years of age. The associations between the levels of blood pressure at 9 years of age and at 30 years of age were significant for systolic blood pressure only in male subjects and were not significant for diastolic blood pressure in either sex. The correlations between the rate of blood pressure change from 9 to 18 years of age and blood pressure levels at 30 years of age were nonsignificant. When the initial values and the rate of change in blood pressure from 9 to 18 years of age were taken into account simultaneously, they accounted for approximately 20% of the variation in systolic blood pressure levels at 30 years of age. This finding indicates that children with higher blood pressure levels at about 9 years of age and with rapid increases in blood pressure during pubescence may have an increased risk of becoming hypertensive.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure, electrolytes, and body size: their relationships in young relatives of men with essential hypertension.

In 154 white chldren aged 8 to 18 years from four large kindreds, relationships among blood pressure (BP), age, sex, body size, and electrolyte excretion were studied. Each kindred was ascertained through one male aged 35-58 years with essential hypertension, namely, a diastolic blood pressure (DBP) over 95 mm Hg. Weight, relative weight (relative to NCHS median for age, sex, and stature), subcutaneous fatfolds, various indices of obesity, and other measures of body size were significantly correlated with systolic blood pressure (SBP) and DBP in each sex (r = 0.3 to 0.7). Sodium and potassium excretion in 24-hour urine was also positively correlated with some measures of body size, and tended to increase with body size at a slightly more rapid rate in boys than in girls. In addition, there was a strong correlation between electrolyte excretion and BP in boys (r = 0.2 to 0.6); however, when the effects of age, body size and fatness were statistically removed, the correlations between BP and electrolyte excretion were not significant, except for 4th phase diastolic pressure (DBP4). These data, therefore, while not strongly supporting a relationship between sodium excretion and BP in children, do not rule out such a relationship, especially in families with a history of hypertension. In addition, these data provide further evidence of a very strong association between BP and body size and fatness in boys and girls.

Blood pressure, body composition, and fat tissue cellularity in adults.

While total body mass has been recognized for many years as having a strong positive association with blood pressure, it is not known whether body mass per se is important in this association or if a component of total mass, such as lean body mass or total body fat, is responsible for the relationship. To determine the relative importance of these components, 217 healthy adults unselected with respect to blood pressure or body composition, who were 18 to 49 years of age (X +/- sd = 33.1 +/- 8.9 years) had body density measured by underwater weighing. Body density was used to estimate percent body fat from which lean body mass and total body fat mass were determined. In addition, an adipose tissue biopsy from the gluteal area was made, and average fat cell size was measured using the osmium tetroxide method; fat cell number was then estimated. In both males and females, after adjusting for age, there were highly significant, positive partial correlations (r = 0.2 to 0.3) between measures of blood pressure (systolic, diastolic, and mean arterial) and percent body fat, total body fat mass or fat cell number. No significant correlation existed between lean body mass or fat cell size and any measure of blood pressure. These findings suggest that fat mass as opposed to body mass, per se, may be an important etiological component in elevated blood pressure in adults.

Compressibility of skinfolds and the measurement of subcutaneous fatness.

Compressibility of subcutaneous fat thickness when measured with skinfold calipers was investigated in 65 white American youths. Compression of skinfolds was determined relative to measurements of subcutaneous fat thickness from radiographs at each of seven sites. There is statistically significant heterogeneity among sites in skinfold compression, with skinfolds on the medial and lateral calf being the least compressible of those measured. There is little statistically significant sex difference in skinfold compression in the present sample and, within the range concerned, there were no significant correlations between skinfold compressibility and age. When compressibilities of the seven skinfolds were intercorrelated within individuals, statistically significant average correlations were obtained, indicating that individuals tend toward similar degrees of skinfold compressibility among sites. This communality of skinfold compression within individuals is such that, at least in male youth, there are significant differences among individuals in the average compressibility of the seven skinfolds.

Aging, body composition, and lifestyle: the Fels Longitudinal Study.

BACKGROUND: Changes in body composition in men and women occur with age, but these changes are affected by numerous covariate factors. OBJECTIVE: The study examined patterns of change in body composition and determined the effects of long-term patterns of change in physical activity in older men and women and in menopausal status and estrogen use in women. DESIGN: Serial measures of height, weight, body mass index (BMI), total body fat (BF), percentage BF, and fat-free mass (FFM) from underwater weighing of 102 men and 108 women enrolled in the Fels Longitudinal Study were analyzed. Physical activity levels and menopausal status were included as covariates. RESULTS: There were significant age-related decreases in FFM and height and increases in total BF, percentage BF, weight, and BMI. Physical activity was associated with decreases in total BF, percentage BF, weight, and BMI in men and were associated with increases in FFM and decreases in total BF and percentage BF in women. Postmenopausal women had significantly higher total BF and percentage BF than did pre- and perimenopausal women. The longer the time since menopause the greater were the increases in weight, BMI, total BF, and percentage BF; however, estrogen use attenuated these increases. CONCLUSIONS: Low FFM can be improved by increased physical activity. The effects of an intervention program on body composition can be masked if only body weight or BMI is measured. The effects of physical activity were more profound in postmenopausal than in premenopausal women, and estrogen use had beneficial effects on body composition.

Size and number of adipocytes and measures of body fat in boys and girls 10 to 18 years of age.

In 111 boys and girls, 10 to 18 yr of age, body density was measured by underwater weighing, and the size of adipocytes in adipose tissue from the buttocks was measured by the osmium tetroxide method. From these two measures, estimates of percentage body fat, total body fat, and adipocyte number were computed for most of the children. Their skeletal age was also calculated by an acceptable method. Across chronological age, the girls have significantly larger mean values of total and percentage body fat and larger and more numerous adipocytes than the boys. The mean number of adipocytes in each sex is within adult levels, as is the mean size of the adipocytes in the girls. The boys' mean adipocyte size is below the adult level. There are negative, significant correlations between percentage body fat and chronological or skeletal age in the boys, and positive significant correlations between total body fat and chronological or skeletal age in the girls. Also, adipocyte size is positively correlated with percentage body fat but only in the boys. With the effects of chronological age removed, percentage body fat was significantly and negatively correlated with skeletal age in boys only. All other correlations among the variables were not statistically significant.

Adipocytes and adiposity in adults.

Measures of adipocyte size and body density were collected from 217 nonobese adults 20 to 50 yr of age, and estimates of total body fat, percentage body fat, and adipocyte number were calculated. Women had a greater percentage body fat than men in every age group except the oldest. Women had significantly greater amounts of total body fat and larger adipocytes than men in the 20- to 24-yr group, but men had significantly greater amounts of total body fat than the women in the 45- to 50-yr group. Adipocyte number, total body fat, and percentage body fat are each positively correlated with age in both sexes. Adipocyte size is not correlated with age but is positively correlated with total and percent body fat in men and women irrespective of age. These cross-sectional data suggest that adipocyte number, rather than being stable during adulthood, increases with age and is associated with corresponding increases in total and percentage body fat.

Subcutaneous fat distribution in males and females from 1 to 39 years of age.

Subcutaneous fat thicknesses measured in two longitudinal studies, the Denver Growth Study and the Melbourne Growth Study, were examined to determine 1) if one site of subcutaneous fat measurement is more representative than another of the body's subcutaneous fat layer, 2) if some measurements of subcutaneous fat from specific body areas are more representative of the subcutaneous fat layer than others, and 3) if there are sex and age differences in intersite relationships. Data from the Denver Study include skinfold thicknesses from 10 sites measured serially at annual ages from 4 to 39 yr and radiographic fat thickness measured at five sites at annual ages from 1 to 18 yr. In the Melbourne Study, five skinfold thicknesses were measured serially in children from 2 to 15 yr of age. Relatively low intersite communalities during the prepubertal years suggest a tendency in each sex for considerable site-to-site variation during this period. However, immediately before puberty and throughout adolescence, high communalities indicate that the thickness of subcutaneous fat at any site is highly related to thickness at all other sites. After puberty and into the mid-20's, there is a reoccurrence of greater site-to-site variability. This higher degree of variation continues into early middle age only in women, implying that more changes occur in their subcutaneous fat, that differentially affect various parts of the body, than in men.

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.

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.

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.

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.

Total-body and regional bone mineral content and areal bone mineral density in children aged 8-18 y: the Fels Longitudinal Study.

BACKGROUND: Techniques for cross-calibration of bone mineral content (BMC) and bone mineral density (BMD) between manufacturers of dual-energy X-ray absorptiometry (DXA) instruments are currently inadequate for total body measurements. Therefore, manufacturer-specific data for BMC and BMD in children are needed. OBJECTIVE: We provided age- and sex-specific means and SDs for total-body and regional BMC and areal BMD in 8-18-y-old white children. DESIGN: BMC and BMD of the head, arms, legs, pelvis, spine, and total body were determined by DXA. Data include 465 annual measurements from 148 healthy children with body weights between 30 and 100 kg and statures <190 cm. RESULTS: There were significant sex differences in BMC at ages 15-18 y for the total body and legs, at ages 12 and 15-18 y for arms and pelvis, at ages 11-13 and 16-18 y for the spine, and at ages 10-11 y for the head. There were significant sex differences in BMD at ages 16-18 y for total body, arms, and legs; at ages 12-13 and 16-18 y for the pelvis; at ages 12-14 and 18 y for the spine; and at ages 13-18 y for the head. CONCLUSIONS: Data presented in this investigation can be used to compare the BMC and BMD of 8-18-y-old white children (with statures <190 cm and body weights between 30 and 100 kg) using DXA.

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.

Major gene model for the inheritance of catechol-O-methyltransferase activity in five large families.

Five large families including 1,189 individuals were each ascertained through one proband with essential hypertension. Four of the probands were white and one was black. Erythrocyte catechol-o-methyltransferase (COMT) activity was measured in 551 family members. Standard statistical methods were used to investigate sex, age, and family differences in COMT activity. Maximum-likelihood methods were used to fit mixtures of normal distributions to COMT activity. COMT activity is distinctly bimodal. Pedigree segregation analyses were performed on the untransformed COMT values, their square roots, and natural logarithms in each family. In no family and under none of the three transformations was it possible to reject the hypothesis of Mendelian transmission of a major gene with two alleles in Hardy-Weinberg equilibrium. In most cases a genetic hypothesis with complete dominance or recessiveness, or a hypothesis of equal transmission probabilities was rejected. While the different transformations had a large effect on the skewness and kurtosis of the overall distribution of the data, they had little effect on the outcome of these segregation analyses. Therefore, this study strongly supports the concept that variation in COMT activity is due in large part to the effects of a major gene.