CDC growth charts: United States.

OBJECTIVES: This report presents the revised growth charts for the United States. It summarizes the history of the 1977 National Center for Health Statistics (NCHS) growth charts, reasons for the revision, data sources and statistical procedures used, and major features of the revised charts. METHODS: Data from five national health examination surveys collected from 1963 to 1994 and five supplementary data sources were combined to establish an analytic growth chart data set. A variety of statistical procedures were used to produce smoothed percentile curves for infants (from birth to 36 months) and older children (from 2 to 20 years), using a two-stage approach. Initial curve smoothing for selected major percentiles was accomplished with various parametric and nonparametric procedures. In the second stage, a normalization procedure was used to generate z-scores that closely match the smoothed percentile curves. RESULTS: The 14 NCHS growth charts were revised and new body mass index-for-age (BMI-for-age) charts were created for boys and girls (http://www.cdc.gov/growthcharts). The growth percentile curves for infants and children are based primarily on national survey data. Use of national data ensures a smooth transition from the charts for infants to those for older children. These data better represent the racial/ethnic diversity and the size and growth patterns of combined breast- and formula-fed infants in the United States. New features include addition of the 3rd and 97th percentiles for all charts and extension of all charts for children and adolescents to age 20 years. CONCLUSION: Created with improved data and statistical curve smoothing procedures, the United States growth charts represent an enhanced instrument to evaluate the size and growth of infants and children.

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.

Incremental growth charts.

Serial data from 818 normal American white children have been used to construct 6-month increment charts for weight (0 to 18 years), head circumference and recumbent length (0 to 3 years), and stature (2 to 18 years). The attained growth status of these children is very close to that shown in the National Center for Health Statistics charts at all ages. Consequently, the present increment charts are widely applicable; it is expected secular changes will not affect their usefulness in ther near future. The need for accurate anthropometric techniques is emphasized and guides to the interpretation of findings are presented.

Race- and sex-specific reference data for triceps and subscapular skinfolds and weight/stature.

The best clinical indicators of percentage body fat on statistical grounds are triceps skinfold thickness in females aged 6 to 50.0 yr and boys 6 to 8 yr, and weight/stature 2 (W/S2) in men. The most valid simple clinical estimators of total body fat are W/S2 in females aged 6 to 50.9 yr and adult males 19 yr and older, and subscapular skinfold thickness in boys 6 to 18 yr. This report presents race- and sex-specific reference data for these three measures based on the First Health and Nutrition Examination Survey for individuals 6 to 50.9 yr of age. Data for Blacks and whites are presented separately because of the large differences in their distributions on these measures. When compared to data from the Health Examination Survey, 1960 to 1962, the present data show evidence of a secular trend toward higher values for triceps and subscapular skinfold thickness in the upper percentiles in adults. The tables presented can be used clinically, with the specified reservations to indicate percentage body fat or total body fat for individuals.

Fat areas as estimates of total body fat.

The efficacy of cross-sectional fat areas in estimating total body fat was investigated in a sample of white American children and adults. Body density and total fat weight (kg) in the body were determined by hydrostatic weighing. Fat areas were calculated for the arm and calf using the appropriate limb circumferences and skinfolds measured at the triceps, biceps, and calf sites; also, a fat area was calculated using the average of triceps and biceps sites and arm circumference. Cross-sectional fat areas do not estimate body density (and percentage fat) any better than the corresponding skinfolds. In estimating weight of fat in the body, however, fat areas are systematically better estimators than corresponding skinfold thicknesses.

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.

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.

Abdominal composition quantified by computed tomography.

Abdominal composition was quantified from computed tomography (CT) scans of 96 clinically normal men and women aged 20-83 y. Measurements were taken of total and intraabdominal areas and of muscle, bone, and subcutaneous and intraabdominal adipose-tissue areas from each of six 8-mm-thick transverse slices from CT images of abdomen and pelvis. Men had a significantly greater percentage of intraabdominal adipose tissue than women and the percentage increased with age in each sex. Percentages of total abdominal area that were adipose tissue were significantly negatively correlated with percentages of muscle and bone in each sex. Ratios of total areas of abdominal slices to total areas of pelvic slices (analogous to waist:hip ratios) had significant positive correlations with the absolute and relative areas of intraabdominal and subcutaneous adipose tissue for the abdomen in women but not in men. These ratios also had significant negative correlations with absolute and relative areas of muscle and bone in women.

Bioelectric impedance phase angle and body composition.

The use of bioelectric impedance phase angle for predicting body composition was determined in 53 males and 69 females 9-62 y of age. The phase angle describes the amount of reactance (Xc) in a conductor relative to the amount of resistance (R). Bioelectric resistance (R) and reactance (Xc) were determined for the whole body and separately for arm, leg, and trunk. Weight, stature, and skinfold thicknesses were measured. Body composition was determined from densitometry. Phase angles for the trunk (phi t), leg (phi 1), and whole body (phi w) had significant (p less than 0.05) negative correlations with percent body fat (%BF) in each sex, and positive correlations with fat-free mass (FFM) in males. In multiple regression analyses, phi t was associated significantly with %BF after controlling for age, mean skinfold thickness, and weight/stature2 in each sex. Bioelectric phase angle for the trunk may be useful for predicting %BF in clinical and survey research.

Specific resistivity used to estimate fat-free mass from segmental body measures of bioelectric impedance.

This report provides estimates of specific resistivity for a sample of 123 children and adults aged 9-62 y. The mean muscle-specific resistivities for the upper and lower extremities (arm and leg) and trunk of these participants were used to compute estimates of fat-free mass (FFM) from the sum of the corrected total muscle conductive volumes of the arms, legs, and trunk. Mean values for predictions of FFM from S2/Z or from the product of total muscle conductive volume and the density of FFM were not significantly different from means of FFM estimated from body density by underwater weighing. This analysis demonstrates that an estimate of FFM can be obtained by summing the conductive muscle volumes of each body segment derived from the corresponding segment lengths squared, measures of bioelectric impedance, and mean muscle-specific resistivities. These mean estimates of FFM are not as accurate as mean predictions of FFM from S2/Z in regression equations.

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.

Grading body fatness from limited anthropometric data.

Measurements relevant to body fatness are made commonly in clinical settings. However, associations between these measurements and body fatness are poorly known and procedures are needed to facilitate the interpretation of these measurements. Consequently, data from 405 white children and adults aged 6 to 49 yr were used to calculate the correlations between selected anthropometric measurements and estimates of percentage body fat and total body fat. Comparisons among these correlations, for children and adults of each sex, lead to conclusions that the triceps skinfold is the best single indicator of percentage body fat in children and women; weight/stature is the best single indicator of total body fat in girls and adults. In men weight/stature is the best indicator of percentage body fat and in boys the subscapular skinfold is the best indicator of total body fat. Weight/stature can be obtained using a calculator or the nomogram provided. It is recommended that these measures be obtained when there is interest in body fatness and the data compared with percentiles from a nationally representative sample.

Incremental growth tables: supplementary to previously published charts.

Serial data from 818 normal white American children from the Fels Longitudinal Study have been used to construct tables of 6-mo increments for weight (0 to 18 yr), stature (3.0 to 18 yr), head circumference, and recumbent length (0 to 3 yr). The tables supplement previously published incremental growth charts. The attained growth status of these children has been shown to be very close to that displayed in the National Center for Health Statistics tables at all ages, and secular trends in the data have been shown to be minimal. Consequently, the present tables should be widely applicable for some time in the future. Guidelines for the use of the tables and interpretation of findings are presented.

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.

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.