S S Guo's research while affiliated with Wright State University and other places

Body composition estimates for the US population are important in order to analyze trends in obesity, sarcopenia and other weight-related health conditions. National body composition estimates have not previously been available. To use transformed bioelectrical impedance analysis (BIA) data in sex-specific, multicomponent model-derived prediction formulae, to estimate total body water (TBW), fat-free mass (FFM), total body fat (TBF), and percentage body fat (%BF) using a nationally representative sample of the US population. Anthropometric and BIA data were from the third National Health and Nutrition Examination Survey (NHANES III; 1988-1994). Sex-specific BIA prediction equations developed for this study were applied to the NHANES data, and mean values for TBW, FFM, TBF and %BF were estimated for selected age, sex and racial-ethnic groups. Among the non-Hispanic white, non-Hispanic black, and Mexican-American participants aged 12-80 y examined in NHANES III, 15 912 had data available for weight, stature and BIA resistance measures. Males had higher mean TBW and FFM than did females, regardless of age or racial-ethnic status. Mean TBW and FFM increased from the adolescent years to mid-adulthood and declined in older adult age groups. Females had higher mean TBF and %BF estimates than males at each age group. Mean TBF also increased with older age groups to approximately 60 y of age after which it decreased. These mean body composition estimates for TBW, FFM, TBF and %BF based upon NHANES III BIA data provide a descriptive reference for non-Hispanic whites, non-Hispanic blacks and Mexican Americans in the US population.

The Medical Outcomes Study Short-Form Health Survey (SF-36) was used to assess the quality of life for adults who differed in level of risk for cardiovascular disease. Subjects were 51 men and 80 women from southwestern Ohio between the ages of 20 and 86 years. Individuals level of risk was based on the culmination of four cardiovascular disease risk factors: hypertension (i.e., systolic BP>or=140 mmHg or diastolic BP>or= 90 mmHg), obesity (i.e., BMI>or=30), high cholesterol (i.e., total cholesterol>or=240 mg/dL), and presence/absence of smoking. Each risk factor was analyzed independently and cumulatively for effects on the SF-36 dimensions (i.e., Physical Functioning, Role-Physical, Bodily Pain, General Health, Vitality, Social Functioning, Role-Emotional, Mental Health). The data suggested that quality of life impairment (indicated by lower scores on the SF-36 dimensions) increased as the number of cardiovascular disease risk factors an individual had increased. Cardiovascular disease risk factors unknown to the participants had differential effects on the SF-36 dimensions, and quality of life decreased as the number of risk factors individuals had increased.

The purpose of the study was to compare estimates of body density and percentage body fat from air displacement plethysmography (ADP) to those from hydrodensitometry (HD) in adults and children and to provide a review of similar recent studies. Body density and percentage body fat (% BF) were assessed by ADP and HD on the same day in 87 adults aged 18-69 y (41 males and 46 females) and 39 children aged 8-17 y (19 males and 20 females). Differences between measured and predicted thoracic gas volumes determined during the ADP procedure and the resultant effects of those differences on body composition estimates were also compared. In a subset of 50 individuals (31 adults and 19 children), reliability of ADP was measured and the relative ease or difficulty of ADP and HD were probed with a questionnaire. The coefficient of reliability between %BF on day 1 and day 2 was 96.4 in adults and 90.1 in children, and the technical error of measurement of 1.6% in adults and 1.8% in children. Using a predicted rather than a measured thoracic gas volume did not significantly affect percentage body fat estimates in adults, but resulted in overestimates of percentage body fat in children. Mean percentage body fat from ADP was higher than percentage body fat from HD, although this was statistically significant only in adults (29.3 vs 27.7%, P<0.05). The 95% confidence interval of the between-method differences for all subjects was -7 to +9% body fat, and the root mean square error (r.m.s.e.) was approximately 4% body fat. In the subset of individuals who were asked to compare the two methods, 46 out of 50 (92%) indicated that they preferred the ADP to HD. ADP is a reliable method of measuring body composition that subjects found preferable to underwater weighing. However, as shown here and in most other studies, there are differences in percentage body fat estimates assessed by the two methods, perhaps related to body size, age or other factors, that are sufficient to preclude ADP from being used interchangeably with underwater weighing on an individual basis.

In an attempt to determine whether the secular trend toward an earlier onset of puberty has continued over recent decades in the United States of America, published reports concerning the age of attainment of pubertal events have been reviewed. Such reports are very limited and vary in both design and inclusive ages of study subjects. Among females, two recent large cross-sectional studies indicate that fifty percent of females in the United States attain Tanner breast stage 2 at 9.5 to 9.7 years of age. This is younger than previously thought, although adequate earlier studies of girls in the United States are not available for comparison. These two studies also indicate that about 14% of girls attain Tanner stage 2 while 8 years of age; one study extends earlier reporting that about 6% exhibit onset of breast development while 7 years of age. There is no evidence that the age of menarche or the attainment of adult (Tanner 5) breast development has decreased over the past 30 years. The data also suggest an earlier onset of Tanner stage 2 pubic hair but no change in attainment of stage 5. Among males, pubic hair may be appearing at younger ages, but data are inadequate or too inconsistent to allow firm interpretation. The lack of standardization of genital criteria of pubertal onset in the male makes any conclusions regarding secular trends impossible. In summary, earlier secular trends over recent decades related to better health, improved nutrition or socio-economic status, or any putative influence by endocrine disrupters cannot be verified.

Childhood overweight develops during 'critical periods', but the relationship of body mass index (BMI) patterns during 'critical periods' from childhood into adulthood with subsequent overweight and adiposity has not been previously investigated. BMI patterns during early childhood, pubescence and post-pubescence and their independent effects on overweight and body fatness at 35-45 y of age were examined along with birth weight and the effects of adult lifestyle factors. BMI parameters describing the timing, velocity minimum (min) and maximum (max) values from 2 to 25 y of age were related to adulthood BMI values and total and percentage body fat (TBF, %BF) at 35-45 y. These data were from 180 males and 158 females in the Fels Longitudinal Study. There was no sex difference in the timing of BMI rebound, but the age of BMI maximum velocity and maximum BMI were both earlier in girls. Children with an earlier BMI rebound had larger BMI values at rebound and at maximum velocity. Children who reached maximum BMI at later age had larger maximum BMI values. Maximum BMI was a strong predictor for adult BMI and in females, a strong predictor of adulthood TBF and %BF. Maximum BMI was closely related to maximum BMI velocity in females and in males, BMI at maximum velocity is a strong predictor of TBF and %BF. Changes in childhood BMI were related to adult overweight and adiposity more so in females than males. BMI rebound is a significant important period related to overweight at 35-45 y in females but not in males. However BMI patterns during and post-adolescence were more important than the BMI rebound for adulthood TBF and %BF status. There is marked tracking in BMI from approximately 20 y into 35-45 y. The pattern of BMI changes from 2 to 25 y had stronger effects on subsequent adult overweight than birth weight and adult lifestyle variables.

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. 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. 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. 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.