Family history and risk of hair loss.

INTRODUCTION: The genetic basis of androgenetic alopecia (AGA) is well accepted in the medical community and among the general population. However, rigorous studies investigating the familial basis of AGA are lacking. The purpose of the current study was to explore the relationship between family history and expression of AGA in a sample of men from the general community. METHODS: Hair loss was assessed by an independent observer trained by an expert dermatologist using the Norwood/Hamilton classification scale and a 7-point global description of hair loss. Men were classified into two groups, one as having little or no hair loss and the other having hair loss. The family history of hair loss in parents and grandparents was assessed by subject self-report. RESULTS: Adjusting for age, men whose fathers had hair loss were 2.5 times as likely to have had some level of hair loss compared to men whose fathers had no hair loss (95% CI: 1.3-4.9). Likewise, men whose fathers had hair loss were twice as likely to have hair loss than men whose fathers had no hair loss even after adjusting for age (OR = 2.1, 95% CI: 1.2-3.7 and OR = 2.5, 95% CI: 1.4-4.7 for Norwood/Hamilton and global description of hair loss assessments, respectively). CONCLUSION: Results suggest that the probability of male pattern hair loss is dependent on family history and age. Hair loss in a man's father also appears to play an important role in increasing a man's risk of hair loss, either in conjunction with a history of hair loss in the mother or hair loss in the maternal grandfather.

2000 CDC Growth Charts for the United States: methods and development.

OBJECTIVES: This report provides detailed information on how the 2000 Centers for Disease Control and Prevention (CDC) growth charts for the United States were developed, expanding upon the report that accompanied the initial release of the charts in 2000. METHODS: The growth charts were developed with data from five national health examination surveys and limited supplemental data. Smoothed percentile curves were developed in two stages. In the first stage, selected empirical percentiles were smoothed with a variety of parametric and nonparametric procedures. In the second stage, parameters were created to obtain the final curves, additional percentiles and z-scores. The revised charts were evaluated using statistical and graphical measures. RESULTS: The 1977 National Center for Health Statistics (NCHS) growth charts were revised for infants (birth to 36 months) and older children (2 to 20 years). New body mass index-for-age (BMI-for-age) charts were created. Use of national data improved the transition from the infant charts to those for older children. The evaluation of the charts found no large or systematic differences between the smoothed percentiles and the empirical data. CONCLUSION: The 2000 CDC growth charts were developed with improved data and statistical procedures. Health care providers now have an instrument for growth screening that better represents the racial-ethnic diversity and combination of breast- and formula-feeding in the United States. It is recommended that these charts replace the 1977 NCHS charts when assessing the size and growth patterns of infants, children, and adolescents.

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.

Statistical effects of varying sample sizes on the precision of percentile estimates.

The present study evaluates the precision of outlying percentile estimates, with age- and sex-associated variations and facilitates decisions needed to revise the current NCHS 1977 Growth Charts with regard to 1) the inclusion of 3(rd) and 97(th) percentiles and 2) the selection of survey data for the construction of the revised growth charts. Simulation was performed to obtain data with distribution characteristics similar to those of The Third National Health and Nutritional Examination Survey (NHANES III) (1988-1991) data. NHANES III consists of a two-phase, 6-year, complex stratified multistage probability cluster, cross-sectional survey conducted from 1988 through 1994 to represent the US noninstitutionalized population. Phase I of the survey consisted of 679 boys and 622 girls in age groups 3, 8, 13, and 18 years. Weight and stature, the body mass index (BMI) (weight/stature(2); kg/m(2)) was calculated. The results show that 1) the precision of the percentile estimates is greater for stature than for weight and BMI, 2) percentiles during the pubertal period are less precise than those during the prepubertal and postpubertal periods for weight and BMI but there is little difference for stature, and 3) percentile estimates are more precise for girls than boys for weight and BMI, but not for stature. The present findings suggest that pooling of NHANES III and earlier National Center for Health Statistics (NCHS) survey data is necessary to achieve reasonable precision for the 3(rd) and 97(th) percentile estimates. Am. J. Hum. Biol. 12:64-74, 2000. Copyright 2000 Wiley-Liss, Inc.

Relationship of skeletal age to limb composition during pubescence.

The relationships between skeletal age (SA) and limb composition (arms, legs, and all four limbs) in terms of fat mass (FM), fat-free mass (FFM), muscle mass (MM) and bone mineral content (BMC) were investigated in 55 males and 53 females aged 9-15 years. The Fels method was used to assess hand-wrist SAs which were expressed as SA/chronological age (SA/CA). The limb composition data were obtained from a Lunar dual-energy x-ray absorptiometer using 3.6z software. The means for the limb composition variables increased gradually with age except in males for whom FM decreased from 12 to 13 years, and FFM and MM increased markedly from 13 to 14 years. There were similar findings when the limb composition data were expressed as percentages of body weight. All of the regressions of SA/CA on limb composition variables had positive slopes. Each of the slopes was significant for males, but nonsignificant for females. © 1996 Wiley-Liss, Inc.

Body composition measures from underwater weighing and dual energy X-ray absorptiometry in black and white girls: A comparative study.

The purpose of this study was to compare estimates of body composition in two ethnic groups, 31 black and 38 white girls 10 through 16 years of age, to establish accurate and precise laboratory standards for field measures of body composition in the NHLBI Growth and Health Study HC 55025. The dual energy X-ray absorptiometry (DXA) measures of fat free mass (FFM) and % body fat (%BF) were made using Hologic QDR-1000/W. Corresponding values of FFM and %BF from underwater weighing (UWW) were determined using the two-component model of Siri, and these were corrected using the model of Lohman for white girls only. In the comparison of the different models and methods, the two-component model overestimated FFM compared to estimates from DXA for black girls, as did the corrected Lohman model for white girls. The two-component model significantly overestimated %BF in both white and black girls compared to corresponding estimates from DXA. The ratio of bone mineral content (BMC)/FFM affected the degree of %BF differences in black girls but not in white girls. Also, as the density of FFM increased or approached adult status in black girls (BMC/FFM increased), differences between the two-component model and estimates from DXA decreased. In both groups of girls, the relationship of %BF from UWW and DXA are a function of the level of body fatness. DXA values of %BF are greater than those from UWW under about 24% body fat, but the converse occurs above 25% body fat. The inability of UWW using the two-component model to account for the body composition in these girls can be corrected in part by measuring the variables for a multicomponent model or more easily by using DXA estimates of body composition. © 1994 Wiley-Liss, Inc.

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.

Prediction of fat-free mass in black and white pre-adolescent and adolescent girls from anthropometry and impedance.

As an ancillary project of the National Heart Lung and Blood Institute's Growth and Health Study (NGHS), data of 31 black girls and 38 white girls, 10-16 years of age, were used to develop equations to predict fat-free mass (FFM) from selected anthropometric dimensions and bioelectric impedance measures of resistance and reactance. Subjects were drawn from ongoing projects at the Children's Hospital Medical Center (CHMC) to obtain girls of both races from a wide range of body mass indices. FFM was estimated from measures of dual energy X-ray absorptiometry (DXA). The resulting equations had a root mean square error (RMSE) of 1.9 kg and a coefficient of variation (CV) of 4.9% for black girls using independent variables: stature divided by resistance squared (S2 /R), thigh circumference, subscapular and suprailiac skinfold thicknesses. The corresponding values for white girls were 1.1 kg and 3.2% using independent variables: S2 /R, arm circumference, weight, and reactance divided by resistance (R/Rc ). In addition to cross-validating the ethnic-specific equations using PRESS statistics, the equation for white girls was also cross-validated using an independent sample of 35 girls from the Fels Longitudinal Study selected to match the CHMC sample. The cross-validation yielded a pure error of 2.4 kg FFM and a CV of 7%. The predicted values for FFM from the equations were used to calculate percentage of body fat in the CHMC sample and the pure errors for estimating percentage of body fat were 3% for blacks and 2% for whites. © 1993 Wiley-Liss, Inc.