Significant associations of age, menopausal status and lifestyle factors with visceral adiposity in African-American and European-American women.

BACKGROUND: Elevated visceral adiposity is strongly predictive of cardiometabolic disease, but, due to the high cost of biomedical imaging, assessment of factors contributing to normal variation in visceral (VAT) and subcutaneous (SAT) adipose tissue partitioning in large cohorts of healthy individuals are few, particularly in ethnic and racial minority populations. OBJECTIVE: To describe age, menopausal status, smoking and physical activity differences in VAT and abdominal subcutaneous adipose tissue (ASAT) mass in African-American (AA) and European-American (EA) women. METHODS: Magnetic resonance imaging measures of VAT and ASAT mass and VAT% (VAT/VAT+ASAT, %) were obtained from a cross-sectional sample of 617 EA and 111 AA non-diabetic women aged 18-80 years. Multivariate linear regression was used to test independent effects of the covariates. RESULTS: VAT and VAT% were higher in EA than AA women (p < 0.01). Differences in VAT, ASAT and VAT% across age groups began in early adulthood in both ethnic groups, but the association of age with VAT% was stronger in EA women (p for interaction = 0.03). Current smokers had higher VAT and VAT% (p < 0.01) and lower TBF than non-smokers. Frequent participation in sports activities was associated with ∼30% lower VAT in older (>55 years) as well as younger ( < 40 years) women (p < 0.0001). CONCLUSION: Greater allocation of abdominal adipose tissue into the visceral compartment occurs in EA than AA women and in older than younger women. Avoidance of cigarette smoking and frequent participation in sports activities may partially counteract this deleterious phenomenon of ageing.

Bayesian longitudinal plateau model of adult grip strength.

OBJECTIVES: This article illustrates the use of applied Bayesian statistical methods in modeling the trajectory of adult grip strength and in evaluating potential risk factors that may influence that trajectory. METHODS: The data consist of from 1 to 11 repeated grip strength measurements from each of 498 men and 533 women age 18-96 years in the Fels Longitudinal Study (Roche AF. 1992. Growth, maturation and body composition: the Fels longitudinal study 1929-1991. Cambridge: Cambridge University Press). In this analysis, the Bayesian framework was particularly useful for fitting a nonlinear mixed effects plateau model with two unknown change points and for the joint modeling of a time-varying covariate. Multiple imputation (MI) was used to handle missing values with posterior inferences appropriately adjusted to account for between-imputation variability. RESULTS: On average, men and women attain peak grip strength at the same age (36 years), women begin to decline in grip strength sooner (age 50 years for women and 56 years for men), and men lose grip strength at a faster rate relative to their peak; there is an increasing secular trend in peak grip strength that is not attributable to concurrent secular trends in body size, and the grip strength trajectory varies with birth weight (men only), smoking (men only), alcohol consumption (men and women), and sports activity (women only). CONCLUSIONS: Longitudinal data analysis requires handling not only serial correlation but often also time-varying covariates, missing data, and unknown change points. Bayesian methods, combined with MI, are useful in handling these issues.

Genetic analysis of self-reported physical activity and adiposity: the Southwest Ohio Family Study.

OBJECTIVE: Physical inactivity poses a major risk for obesity and chronic disease, and is influenced by both genetic and environmental factors. However, the genetic association between physical activity (PA) level and obesity is not well characterized. Our aims were to: (i) estimate the extent of additive genetic influences on physical activity while adjusting for household effects; and (ii) determine whether physical activity and adiposity measures share common genetic effects. SUBJECTS: The sample included 521 (42 % male) adult relatives, 18-86 years of age, from five large families in the Southwest Ohio Family Study. DESIGN: Sport, leisure and work PA were self-reported (Baecke Questionnaire of Habitual Physical Activity). Total body and trunk adiposity, including percentage body fat (%BF), were measured using dual-energy X-ray absorptiometry. Abdominal visceral and subcutaneous adipose tissue mass were measured using MRI. RESULTS: Heritabilities for adiposity and PA traits, and the genetic, household and environmental correlations among them, were estimated using maximum likelihood variance components methods. Significant genetic effects (P < 0.05) were found for sport (h2 = 0.26) and leisure PA (h2 = 0.17). Significant (P < 0.05) household effects existed for leisure PA (c2 = 0.25). Sport PA had a negative genetic correlation with central adiposity measurements adjusted for height (rhoG > |-0.40|). Sport and leisure PA had negative genetic correlations with %BF (rhoG > |-0.46|). CONCLUSIONS: The results suggest that the association of sport and leisure PA with lower adiposity is due, in part, to a common genetic inheritance of both reduced adiposity and the predisposition to engage in more physical activity.

Childhood obesity predicts adult metabolic syndrome: the Fels Longitudinal Study.

OBJECTIVES: To determine the age of significant divergence in body mass index (BMI) and waist circumference in adults with and without the metabolic syndrome, and to provide age- and sex-specific childhood values that predict adult metabolic syndrome. STUDY DESIGN: Part 1 of this study is a retrospective cohort study of 92 men and 59 women (mean age, 51 years) who had metabolic syndrome and 154 randomly selected adults matched for age and sex who did not have the syndrome. Part 2 is a study of predictive accuracy in a validation sample of 743 participants. RESULTS: The first appearance of differences between adults with and without metabolic syndrome occurred at ages 8 and 13 for BMI and 6 and 13 for waist circumference in boys and girls, respectively. Odds ratios (ORs) for the metabolic syndrome at 30 years and older ranged from 1.4 to 1.9 across age groups in boys and from 0.8 to 2.8 across age groups in girls if BMI exceeded criterion values in childhood. The corresponding ORs for waist circumference ranged from 2.5 to 31.4 in boys and 1.7 to 2.5 in girls. These ORs increased with the number of examinations. CONCLUSIONS: Children with BMI and waist circumference values exceeding the established criterion values are at increased risk for the adult metabolic syndrome.

Approximation of total visceral adipose tissue with a single magnetic resonance image.

BACKGROUND: A single axial image measured between the 4th and 5th lumbar vertebrae (L4-L5) is most frequently chosen to approximate total abdominal visceral adipose tissue (VAT) volume, but growing evidence suggests that this measurement site is not ideal. OBJECTIVE: The objective was to determine the single magnetic resonance (MR) image that best approximates the total VAT volume in a biracial sample of healthy subjects. DESIGN: We used contiguous abdominal MR images to measure VAT area and summed them to determine total VAT volume. The sample included 820 healthy men and women (n = 692 whites, 128 blacks) aged 18-88 y. RESULTS: A range of MR images had equally high correlations with total VAT in each race and sex group. The image 6 cm above L4-L5 (L4-L5 + 6) was within the best equivalent range for all race and sex groups. The L4-L5 + 6 image crossed the L3 vertebra in 85% of subjects and crossed the L2-L3 intervertebral space or the L2 vertebra for 15% of subjects. Linear regression models indicated that the L4-L5 + 6 image explained 97% of the variance in total abdominal VAT volume, and additional covariates did not increase the R(2) value significantly. The L4-L5 image explained 83% of the variance in VAT volume, and the covariates accounted for an additional 7% of the variance. Rank-order values for VAT can change if total VAT volume is approximated by a single image area. Whereas 25% of subjects changed rank by >or=10% with the L4-L5 image, only 3% changed rank to that degree with the L4-L5 + 6 image. CONCLUSIONS: A single MR image located approximately at the L3 vertebra can accurately estimate total VAT volume in blacks and whites of both sexes.

Quantitative genetics of cortical bone mass in healthy 10-year-old children from the Fels Longitudinal Study.

The genetic influences on bone mass likely change throughout the life span, but most genetic studies of bone mass regulation have focused on adults. There is, however, a growing awareness of the importance of genes influencing the acquisition of bone mass during childhood on lifelong bone health. The present investigation examines genetic influences on childhood bone mass by estimating the residual heritabilities of different measures of second metacarpal bone mass in a sample of 600 10-year-old participants from 144 families in the Fels Longitudinal Study. Bivariate quantitative genetic analyses were conducted to estimate genetic correlations between cortical bone mass measures, and measures of bone growth and development. Using a maximum likelihood-based variance components method for pedigree data, we found a residual heritability estimate of 0.71 for second metacarpal cortical index. Residual heritability estimates for individual measures of cortical bone (e.g., lateral cortical thickness, medial cortical thickness) ranged from 0.47 to 0.58, at this pre-pubertal childhood age. Low genetic correlations were found between cortical bone measures and both bone length and skeletal age. However, after Bonferonni adjustment for multiple testing, rho(G) was not significantly different from 0 for any of these pairs of traits. Results of this investigation provide evidence of significant genetic control over bone mass largely independent of maturation while bones are actively growing and before rapid accrual of bone that typically occurs during puberty.

Quantitative genetic analysis of cellular adhesion molecules: the Fels Longitudinal Study.

Circulating concentrations of inflammatory markers predict cardiovascular disease (CVD) risk and are closely associated with obesity. However, little is known concerning genetic influences on serum levels of inflammatory markers. In this study, we estimated the heritability (h2) of soluble cellular adhesion molecule (sCAM) concentrations and examined the correlational architecture between different sCAMs. The study population included 234 men and 270 women aged 18-76 years, belonging to 121 families participating in the Fels Longitudinal Study. Serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sESEL-1) and P-selectin (sPSEL-1) were assayed using commercially available kits. A variance components-based maximum likelihood method was used to estimate the h2 of the different serum inflammatory markers while simultaneously adjusting for the effects of known CVD risk factors, such as age and smoking. Additionally, we used bivariate extensions of these methods to estimate genetic and random environmental correlations among sCAMs. Levels of sCAMs were significantly heritable: h2=0.24+/-0.10 for sICAM-1, h2=0.22+/-0.10 for sVCAM-1, h2=0.50+/-0.11 for sESEL-1, and h2=0.46+/-0.10 for sPSEL-1. In addition, a significant genetic correlation (rho(G)=0.63) was found between sICAM-1 and sVCAM-1 indicating some degree of shared genetic control. In the Fels Longitudinal Study, the levels of four sCAMs are significantly influenced by genetic effects, and sICAM-1 shares a common genetic background with sVCAM-1.

Early menarche and the development of cardiovascular disease risk factors in adolescent girls: the Fels Longitudinal Study.

The purpose of this study was to evaluate the influence of menarcheal age on changes in insulin, glucose, lipids, and blood pressure during adolescence and to assess whether body composition modifies this relationship. We examined 391 girls, a subset of Fels Longitudinal Study female participants (8-21 yr of age). Self-reported menarcheal age was classified based on the National Health and Nutrition Examination Survey III distribution, in which early menarche was at the 25th percentile or less (11.9 yr). Age at menarche was examined in relation to measures of body composition [e.g. fat-free mass (FFM) and percent body fat (PBF)], insulin resistance, blood pressure, and lipid profile. The effects of menarcheal age and body composition on cardiovascular disease risk factor changes were analyzed with serial data mixed models. Median menarcheal age was 12.7 yr (range, 9.8-17.0 yr), with 91 girls (23%) classified as early menarche. Girls with early menarche had more deleterious changes in insulin, glucose, blood pressure, FFM, and PBF levels than girls with average or late menarche. Menarcheal age adversely affected cardiovascular disease risk factor changes independent of age and changes in FFM or PBF. Girls with early menarche exhibited elevated blood pressure and glucose intolerance compared with later maturing girls, independent of body composition.

QDR 4500A dual-energy X-ray absorptiometer underestimates fat mass in comparison with criterion methods in adults.

BACKGROUND: Dual-energy X-ray absorptiometry (DXA) has become one of the most frequently used methods for estimating human body composition. Although the DXA technique has been validated for the measurement of fat-free mass and fat mass, differences in calibration between instruments produced by different manufacturers, as well as between different models produced by the same manufacturer, have been reported. OBJECTIVE: The objective was to compare the calibration of the QDR 4500A against criterion methods in a large heterogeneous population. DESIGN: DXA-derived body-composition data were obtained from 7 studies: 6 data sets were provided by the investigators, one of which was published. The data included fat mass and fat-free mass measured with a QDR 4500A and criteria measurements of body composition from total body water by dilution at 4 centers, densitometry from 1 center, and four-compartment analysis at 2 centers. RESULTS: In the cohort of 1195 subjects, 602 men and 593 women aged 19-82 y with a body mass index (in kg/m2) of 16-44, the fan-beam DXA overestimated fat-free mass (P < 0.05). A significant difference was observed in all 7 data sets, and the mean (+/-SE) was 5 +/- 1%. CONCLUSIONS: It is recommended that the lean soft tissue mass estimate with the fan-beam QDR 4500A be reduced by 5% and that for fat mass be increased by that same mass. This finding is particularly important because the National Health and Nutrition Examination Survey is using the QDR 4500A to assess body composition in a nationally representative sample of persons in the United States.

Quantitative genetic analysis of blood pressure response during the cold pressor test.

BACKGROUND: The genetic association between blood pressure (BP) at rest and during the cold pressor test (CPT) is not well characterized. The purpose of this study was to examine the genetic architecture of BP during the CPT, and to determine whether BP at rest and during the CPT share common genetic influences. METHODS: In 419 individuals distributed across four large families, variance components methods were used to estimate heritabilities of resting BP and CPT BP, along with genetic correlations among BP traits. The CPT consisted of immersion of the left foot in 4 degrees C water while the participant was supine. Blood pressure reactivity (DeltaBP) was defined as BP at 15 to 30 sec and 45 to 60 sec of foot immersion minus resting BP. RESULTS: Significant (P < .05) heritabilities were found for supine BP (h(2)(SBP) = 0.35), CPT BP (h(2)(SBP) = 0.27 and 0.33, h(2)(DBP) = 0.18 and 0.30), and DeltaSBP (h(2)(SBP) = 0.12 and 0.37) but not for DeltaDBP. Bivariate analyses detected significant (P < .05) genetic correlations between resting SBP and CPT SBP that were different from 0 and 1. Genetic correlations between resting DBP and CPT DBP were not significantly different from 1. Genetic correlations between resting SBP and DeltaSBP were not significant. CONCLUSIONS: Measures of BP at rest and during cold immersion are significantly influenced by additive genetic effects. These genetic influences are only partially shared between SBP at rest and SBP during cold immersion, suggesting that a somewhat different set of genes may influence SBP during cold immersion. Unique sets of genes also appear to influence DeltaSBP independent of those influencing resting SBP.

Relations between frame size and body composition and bone mineral status.

BACKGROUND: Frame size is a description of the supportive structure of the skeleton that is used to adjust for skeletal mass and size in measures of body composition and weight. OBJECTIVE: Data from the Fels Longitudinal Study were used to investigate the relation between bicristal, elbow, knee, biacromial, and wrist breadths and measures of total body fat (TBF), fat-free mass (FFM), bone mineral content (BMC), and bone mineral density (BMD) from dual-energy X-ray absorptiometry. DESIGN: The sample consisted of cross-sectional data from 224 white men and 277 white women aged 23-65 y. Multiple regressions were conducted with stature-adjusted measures of body composition and bone mineral status as dependent variables and age and frame size as independent variables. RESULTS: Frame-size measures were significantly and positively associated with all body-composition and bone mineral measures in bivariate analyses. In both men and women, the significant models explained more of the variance in measures of TBF (R2 = 0.51 and 0.66, respectively) and FFM (R2 = 0.35 and 0.39, respectively) than in measures of BMC (R2 = 0.18 and 0.23, respectively) and BMD (R2 = 0.08 and 0.18, respectively). Bicristal, knee, and wrist breadths were associated with TBF, and biacromial, knee, and wrist breadths were positively associated with FFM. Biacromial breadth was positively associated with BMC and BMD. CONCLUSIONS: Frame size was more closely associated with TBF and FFM than with BMC and BMD. The association between frame size and body composition seems to be more structural than substantive. The relations between frame size and BMC and BMD are weak and apparently not related to body composition.

Development and validation of skinfold-thickness prediction equations with a 4-compartment model.

BACKGROUND: Skinfold-thickness measurements are commonly obtained for the indirect assessment of body composition. OBJECTIVE: We developed new skinfold-thickness equations by using a 4-compartment model as the reference. Additionally, we compared our new equations with the Durnin and Womersley and Jackson and Pollock skinfold-thickness equations to evaluate each equation's validity and precision. DESIGN: Data from 681 healthy, white adults were used. Percentage body fat (%BF) values were calculated by using the 4-compartment model. The cohort was then divided into validation and cross-validation groups. Equations were developed by using regression analyses and the 4-compartment model. All equations were then tested by using the cross-validation group. Tests for accuracy included mean differences, R(2), and Bland-Altman plots. Precision was evaluated by comparing root mean squared errors. RESULTS: Our new equations' estimated means for %BF in men and women (22.7% and 32.6%, respectively) were closest to the corresponding 4-compartment values (22.8% and 32.8%). The Durnin and Womersley equation means in men and women (20.0% and 31.0%, respectively) and the Jackson and Pollock mean in women (26.2%) underestimated %BF. All equations showed a tendency toward underestimation in subjects with higher %BF. Bland-Altman plots showed limited agreement between Durnin and Wormersley, Jackson and Pollock, and the 4-compartment model. Precision was similar among all the equations. CONCLUSIONS: We developed accurate and precise skinfold-thickness equations by using a 4-compartment model as the method of reference. Additionally, we found that the skinfold-thickness equations frequently used by clinicians and practitioners underestimate %BF.

Fifty-year trends in serial body mass index during adolescence in girls: the Fels Longitudinal Study.

BACKGROUND: A decline in the age at menarche was recently reported for US girls. Although it is possible that this recent drop stems from the concurrent increase in childhood obesity, few longitudinal studies of growth and development have been undertaken to specifically address the temporal relation between growth, adiposity, and the age at menarche. OBJECTIVE: The objective was to simultaneously examine the effects of birth cohort (secular trend) and rate of maturation (age at menarche) on the timing and pattern of increases in body mass index (BMI) during adolescence in girls. DESIGN: We applied mixed-effects polynomial models to serial BMI data, spanning from 6 y before menarche to 6 y after menarche, obtained from 211 girls enrolled in the Fels Longitudinal Study. We examined the effects of birth cohort (defined as girls born 1929-1946, 1947-1964, and 1965-1983) and age at menarche (defined as < or =11.9 y, 12.0-13.1 y, and > or =13.2 y) on the magnitude and velocity of BMI during adolescence. RESULTS: BMI and BMI velocity in girls born after 1965 were significantly greater than those of girls of earlier birth cohorts, despite stability in the mean age at menarche. Although girls with early menarche tended to have significantly higher BMIs than did girls with average or later menarche, these differences did not emerge until after menarche. CONCLUSION: These data suggest that increases in relative weight are a consequence, rather than a determinant, of the age at menarche and that secular changes in BMI and in the mean age at menarche could be independent phenomena.

A life span approach to cardiovascular disease risk and aging: the Fels Longitudinal Study.

As the leading cause of chronic disease mortality in developed nations, cardiovascular disease is a widely prevalent condition that is integral to evaluation of aging populations. Chronic diseases such as coronary heart disease, hypertension and type 2 diabetes have been associated with adulthood body composition-namely excess body fat, altered lipid levels and elevated blood pressures. The Fels Longitudinal Study conducted at the Lifespan Health Research Center at Wright State University's School of Medicine has examined these same health status indicators-body composition, blood pressure, lipids, maturation, and hormones-during early life and their relationships to developing risk factors for these chronic diseases in adulthood. Research conducted during the past 10 years has shown health status indicators to track over time from childhood to adulthood. Furthermore, chronic disease risk factors attained during childhood, adolescence or early adulthood may represent an early warning system for future risk of developing cardiovascular disease.

Heritability of calcaneal quantitative ultrasound measures in healthy adults from the Fels Longitudinal Study.

Quantitative ultrasound (QUS) measurements of bone have been reported to predict osteoporotic fracture risk in postmenopausal women and older men. Although many studies have examined the heritability of bone mineral density (BMD), few studies have estimated the heritability of calcaneal QUS phenotypes. In the present study, we examined the genetic regulation of calcaneal QUS parameters in individuals from nuclear and extended families. The study population includes 260 men and 295 women aged 18-91 years (mean+/-SD: 46+/-16 years) who belong to 111 pedigrees in the Fels Longitudinal Study. Three measures of calcaneal structure were collected from both the right and left heel using the Sahara bone sonometer. These measures included broadband ultrasound attenuation (BUA), speed of sound (SOS), and the quantitative ultrasound index (QUI). We used a variance components based maximum likelihood method to estimate the heritability of QUS parameters while simultaneously adjusting for covariate effects. Additionally, we used bivariate extensions of these methods to calculate additive genetic and random environmental correlations among QUS measures. All phenotypes demonstrated statistically significant heritabilities (P<0.0000001). Heritabilities in the right heel (h2+/-SE) were h2=0.59+/-0.10 for BUA, h2=0.73+/-0.09 for SOS, and h2=0.72+/-0.09 for QUI. Similarly, heritabilities for the left heel were h2=0.52+/-0.10, h2=0.75+/-0.10, and h2=0.70+/0.10, respectively. There was evidence for significant genetic and environmental correlations among these six QUS measures. Combinations of QUS measures in the right and left heel demonstrated genetic correlations of 0.94-0.99 and all were significantly different from one indicating at least a partially unique genetic architecture for each of these measures. This study demonstrates that QUS measures of the calcaneus among healthy men and women are heritable, and there are large shared additive genetic effects among all of the traits examined.

Mathematical modelling of human growth: A comparative study.

Kernel regression is a nonparametric procedure that provides good approximations to individual serial data. The method is useful and flexible when a parametric method is inappropriate due to restricted assumptions on the shape of the curve. In the present study, we compared kernel regression in fitting human stature growth with two models, one of which incorporates the possible existence of the midgrowth spurt while the other does not. Two families of mathematical functions and a nonparametric kernel regression were fitted to serial measures of stature on 227 participants enrolled in the Fels Longitudinal Study. The growth parameters that describe the timing, magnitude, and duration of the growth spurt, such as midgrowth spurt and pubertal spurts, were derived from the fitted models and kernel regression for each participant. The two parametric models and kernel regression were compared in regard to their overall goodness of fit and their capabilities to quantify the timing, rate of increase, and duration of the growth events. The Preece-Baines model does not describe the midgrowth spurt. The dervied growth parameters from the Preece-Baines model show an earlier onset and a longer duration of the pubertal spurt, and a slower increase in velocity. The kernel regression with bandwidth 2 years and a second-order polynomial kernel function yields relatively good fits compared with the triple logistic model. The derived biological parameters for the pubertal spurt are similar between the kernel regression and the triple logistic model. Kernel regression estimates an earlier onset and a more rapid increase of velocity for the midgrowth spurt.

Clustering of cardiovascular risk factors in association with indices of adiposity and adipose tissue distribution in adults.

The hypothesis, that clustering of elevated levels of blood pressures, plasma lipids and lipoprotein cholesterols, and serum glucose in men and women was associated with indices of adiposity and adipose tissue distributione was tested while controlling for family membership, age, level of education, income, and smoking as well as menopause (surgical and natural )and the use of oral contraceptives and replacement estrogens in women. The study population included 146 white men and 171 white women, 18-88 years of age, from 4 large kindreds residing in the Dayton, Ohio, metropolitan area. The data were collected between 1977 and 1980 as part of a study of genetic factors in essentials hypertension. Four groups of individuals with similar levels for blood pressures, plasma lipids and lipoprotein cholesterols, and serum glucose were defined for each sex by using a k-means clustering algorithm. A group was identified in each sex that had higher than average values for all of these risk factors. Membership in this group was associated significantly with age and weight/stature2 in the men, and with age, weight/stature2 and the interaction of age and weight/stature2 in the women, after controlling for level of education, income, smoking, and, in the women, also for menopause, use of oral contraceptives, and replacement estrogens. Group membership was not associated significantly with family membership or with an index of adipose tissue distribution.

X-linked pattern of inheritance for serial measures of weight/stature2.

The pattern of family resemblance for long-term serial measures of weight/stature2 (W/S2 ) in approximately 500 individuals from the Fels Longitudinal Growth Study suggests that X-linked genes may be contributing to the variability in this trait among children, particularly during the prepubertal age range of 2-9 years. In this data set, W/S2 was measured serially at the same ages in all family members. Thus, a parent-child correlation at a specific age can be determined even though the measurements were made on the child a generation later than on the parent. The pattern of family resemblance at each annual age up to 10 years and at ages 14-18 years is consistent with the presence of an X-linked genetic effect. Opposite-sex parent-child pairs are more similar than same-sex pairs, and sister-sister pairs are more similar than brother-brother or brother-sister pairs at these ages. Furthermore, when the distribution of W/S2 is examined separately in boys and girls, there is evidence of commingling in the distribution of boys from 5 to 8 years of age but not in girls. This is consistent with the existence of a major X-linked gene with a frequency of about 3%. This pattern of family resemblance and commingling suggestive of partial X-linkage for W/S2 has not been detected previously because cross-sectional family studies generally compare individuals at different stages of growth.

Reliability for multiple frequency bioelectric impedance.

Multifrequency impedance may help to quantify body fluid compartments and levels of hydration among individuals. Most studies of bioelectric impedance use impedance machines operating at a frequency of 50 kHz, and observer error is low. The present study evaluates multifrequency impedance measurements at 15 frequencies from 5 to 1,300 kHz to determine observer reliability in 20 White subjects of each sex, 18-65 years of age. Data were collected during two time periods so that a participant was measured by each of two observers during each period. There was an effect of frequency and sex on reliability. The intra- and inter-observer reliability for resistance and reactance were high with coefficients of reliability of greater than 95% at frequencies under about 500 kHz for resistance and under 100 kHz for reactance. Technical errors of measurement were generally stable across frequencies for resistance but became increasingly large above 100 kHz for reactance. Resistance measures of men were more reliable than those of women. Reliability was reduced at high frequencies which are potentially useful in determining body fluid volumes. There was no effect of age on reliability. © 1994 Wiley-Liss, Inc.

Serial changes in blood pressure from childhood into young adulthood for females in relation to body mass index and maturational age.

This study determines: (1) patterns of change from childhood to young adulthood in body mass index (BMI), systolic blood pressure (SBP), and diastolic blood pressure (DBP), (2) effects of elevated BMI values on changes in blood pressures (BP), (3) extent of tracking for SBP, DBP, and BMI, and (4) prediction of future risk for elevated BP from earlier values. Annual serial BP and BMI data were available for 198 white females, ages 8-22 years, enrolled in the Fels Longitudinal Study. Patterns of change in BMI were described by a random effects model with a time series model for the correlated residuals. Serial BMI measures were differentiated from age-specific means to measure relative individual BMI levels. Serial BP were analyzed using a similar model to the BMI where relative individual BMI levels were included as an explanatory variable. There was a general increasing trend for SBP, DBP, and BMI from 8-22 years, but the rates of increase declined with age. At the same chronological age, early menarche females had a significantly greater BMI mean value than late menarche females. An average increase of 1 kg/m2 in deviation from BMI population means resulted in an average increase of 1.2 mmHg in SBP and 0.6 mmHg in DBP. Having SBP and DBP levels 1 standard deviation above mean levels, relative to females at mean levels, as early as age 9 represents an odds ratio of 2 for exceeding national 75th percentile levels of SBP and DBP at age 21. Am. J. Hum. Biol. 10: 589-598, 1998. © 1998 Wiley-Liss, Inc.