Sex-specific Equations Research Articles

Sex differences in the toxicokinetics of inhaled solvent vaporsin humans 1. m-Xylene

The aim of this study was to evaluate possible sex differences in the inhalation toxicokinetics of m-xylene vapor. Seventeen healthy volunteers (nine women and eight men) were exposed to m-xylene (200 mg/m 3) and to clean air (control exposure) on different occasions during 2 h of light physical exercise (50 W). The chosen level corresponds to the occupational exposure limit (8-h time weighted average) in Sweden. m-Xylene was monitored up to 24 h after exposure in exhaled air, blood, saliva, and urine by headspace gas chromatography. m-Methylhippuric acid (a metabolite of m-xylene) was analyzed in urine by high-performance liquid chromatography. Body fat and lean body mass (LBM) were estimated from sex-specific equations using bioelectrical impedance, body weight, height, and age. Genotypes and/or phenotypes of cytochromes P450 2E1 and 1A1, glutathione transferases M1 and P1, and epoxide hydrolase were determined. The toxicokinetic profile in blood was analyzed using a two-compartment population model. The area under the concentration–time curve (AUC) of m-xylene in exhaled air postexposure was larger in women than in men. In addition, the excretion via exhaled air was significantly higher in women when correcting for body weight or LBM. In contrast, the men had a significantly higher volume of distribution, excretion of m-methylhippuric acid in urine, and AUC of m-xylene in urine. The toxicokinetic analyses revealed no differences between subjects of different metabolic genotypes or phenotypes. In conclusion, the study indicates small sex differences in the inhalation toxicokinetics of m-xylene, which can be explained by body build.

Potassium per kilogram fat-free mass and total body potassium: predictions from sex, age, and anthropometry.

Total body potassium (TBK) is located mainly intracellularly and constitutes an index of fat-free mass (FFM). The aim was to examine whether TBK and the TBK-to-FFM ratio (TBK/FFM) can be estimated from sex, age, weight, and height. A primary study group (164 males, 205 females) and a validation group (161 and 206), aged 37-61 yr, were randomly selected from the general population. TBK was determined by whole body counting, and FFM was obtained by dual-energy X-ray absorptiometry (DEXA; FFM(DEXA)). The primary study group was used to construct sex-specific equations predicting TBK and TBK/FFM from age, weight, and height. The equations were used to estimate TBK and TBK/FFM in the validation group. The estimates were compared with measured values. TBK in different age ranges was predicted, with errors ranging from 5.0 to 6.8%; errors for TBK/FFM ranged from 2.7 to 4.8%, respectively. By adding FFM(DEXA) as a fourth predictor, the error of the TBK prediction decreased by approximately two percentage units. In conclusion, TBK and TBK/FFM can be meaningfully estimated from sex, age, weight, and height.

The prediction of height by armspan in older Chinese people

Objective : To compare the accuracy of the predictive equations derived from older Chinese people without vertebral deformity with those derived from unselected older people, in estimating height from armspan. Methodology : Height and armspan were measured in 789 older Chinese and 885 young Chinese in Hong Kong. All the older subjects had spinal X-ray (T4 to L4). Vertebral deformity was determined by a trained technician using a translucent digital analyser. Definite deformity was defined by a greater than 3 standard deviation increase in one of the three vertebral height ratios (anterior/posterior, middle/posterior and posterior/posterior). Eighty of the older subjects without vertebral deformity were randomly selected from the studied population for internal validation of predictive equations. The remaining subjects were used to derive sex-specific predictive equations for height by linear regression against armspan. The accuracy of these equations was analysed by the Bland and Altman method. Results : Vertebral deformity was present in 30.7% and 15.6% of older female and male subjects, respectively. Older women without vertebral deformity had significantly greater armspan: height ratio when compared with the young (1.04 versus 1.02), but the corresponding ratios were the same in older and young men (both 1.04). The predictive equation derived from older females without vertebral deformity had lower standard error of estimation and gave estimates closer to measured height than those derived from unselected older women. But this was not the case in older men. Conclusion : In deriving predictive equation to estimate height by armspan in older Chinese women, selecting out older women without vertebral deformity increased accuracy of the equation. This was, however, not the case in older men.

ESTIMATING FITNESS IN OLDER ADULTS

This study evaluated the validity of the Long Distance Corridor Walk (LDCW) as a low cost alternative to treadmill-based assessment of cardiorespiratory fitness in older adults. The LDCW consist of: 1) a 2-min warm-up walk (“covering as much ground as possible”) that also serves as a stepped-down test for those unable to walk for a longer period and 2) a 400m walk “done as quickly as possible”. The 400m component has been found to encourage greater effort than time-limited tests, such as the 6-min walk. Overall and sex-specific equations for estimating VO2max using time to walk 400m, age, race, HR and BP response, perceived effort, height, weight, stride length, and activity level were also developed. The study population consisted of 56 men and 46 women aged 60–91 participating in the Baltimore Longitudinal Study on Aging who had a maximal treadmill test with measured O2 consumption. Subjects did the LDCW the day after treadmill testing on a 20m course. VO2max ranged from 12.2 - 31.1 ml O2/kg/min and time on the 400m walk ranged from 2:52 to 6:18. The correlation between 400m walk time and VO2max was −0.79. The linear regression equation including all variables listed explained 76% of the variance in VO2max. Using a stepwise procedure, only 400m walk time (partial R2 = .625), stride length (partial R2 = 0.55), and ending SBP (partial R2 = 0.32) entered the model explaining 74% of the variance in VO2max. The LDCW provides a valid estimate of cardiorespiratory fitness in older adults. Time to walk 400m with adjustment for stride length and effort, as indicated by ending SBP, produces remarkably close estimates of VO2max, correlating 0.82 for men and 0.86 for women with that determined from a maximal treadmill test.

Absolute risk assessment in the clinical setting

Absolute risk assessment in the clinical setting

Development of sex-specific equations for estimating stature of frail elderly Hispanics living in the northeastern United States

The accurate measurement of stature is not possible in many frail elderly persons because of problems affecting their ability to stand straight. In such cases, knee height may be used to estimate stature. This study was designed to explore the applicability of published regression equations to estimate stature of Puerto Rican and other Hispanic elderly persons living in the northeastern United States and to formulate ethnicity-specific equations for these persons. The study subjects (60-92 y of age) included 569 Hispanics and a comparison group of 153 non-Hispanic whites. Equations to estimate stature of Hispanics and Puerto Ricans living in the northeastern United States were developed with regression models in a randomly selected subgroup of the Hispanics. These equations were tested with the remaining Hispanic subgroup. The published equations significantly overestimated stature of our Hispanic subjects. Equations developed for Massachusetts Hispanics and Puerto Ricans provided estimates of stature that did not differ significantly from measured stature. We found further that equations for non-Hispanic whites published in 1985 predicted statures of our relatively low-income, non-Hispanic white subjects better than did newer 1998 equations developed from a national sample. The stature of elderly Hispanics from the northeastern United States can be estimated by using equations derived from the same population. These, or similar equations, should be used to estimate stature of frail elderly persons for whom standing height cannot be taken accurately. Socioeconomic status as well as ethnicity may affect results when knee height equations are used.

Racial differences in amounts of visceral adipose tissue in young adults: the CARDIA (Coronary Artery Risk Development in Young Adults) Study

In several white populations, visceral adipose tissue (VAT) is a risk factor for development of type 2 diabetes and dyslipidemia. VAT can be accurately assessed by computed topography or magnetic resonance imaging, but is also estimated from anthropometric variables, such as waist-to-hip ratio, waist circumference, or sagittal diameter. To date, anthropometric variables have been used largely in whites and inadequate data are available to evaluate the validity of these variables in other groups. The objectives of this study were to 1) determine whether amount of VAT in relation to total body fatness differs in different race and sex groups and 2) determine which anthropometric variables predict amount of VAT in different race and sex groups. We determined the amount and location of body fat, including assessment of VAT by computed tomography, in young adult white and black men and women participating in the 10-y follow-up of the CARDIA (Coronary Artery Risk Development in Young Adults) Study. Black men had less visceral fat (73.1+/-35.9 cm2) than white men (99.3+/-40 cm2), even when VAT was corrected for total body fatness. Black women were more obese than white women and thus had more visceral fat (75.1+/-37.5 compared with 58.6+/-35.9 cm2, respectively). This difference disappeared when corrected for total body fatness. Both waist circumference and sagittal diameter were good predictors of VAT in all groups. However, the nature of this relation differed such that race- and sex-specific equations will likely be required to estimate VAT from waist circumference or sagittal diameter.

Prediction of body cell mass, fat-free mass, and total body water with bioelectrical impedance analysis: effects of race, sex, and disease

The inability to precisely estimate body composition with simple, inexpensive, and easily applied techniques is an impediment to clinical investigations in nutrition. In this study, predictive equations for body cell mass (BCM), fat-free mass (FFM), and total body water (TBW) were derived from direct measurements through use of single-frequency bioelectrical impedance analysis (BIA) in 332 subjects, including white, black, and Hispanic men and women, who were both healthy control subjects and patients infected with the human immunodeficiency virus (HIV). Preliminary studies showed more accurate predictions of BCM when parallel-transformed values of reactance were used rather than the values reported by the bioelectrical impedance analyzer. Modeling equations derived after logarithmic transformation of height, reactance, and impedance were more accurate predictors than equations using height2/resistance, and the use of sex-specific equations further improved accuracy. The effect of adding weight to the modeling equation was less important than the BIA measurements. The resulting equations were validated internally, and race and disease (HIV infection) were shown not to affect the predictions. The equation for FFM was validated externally against results derived from hydrodensitometry in 440 healthy individuals; the SEE was < 5%. These results indicate that body composition can be estimated with simple and easily applied techniques, and that the estimates are sufficiently precise for use in clinical investigation and practice.

Age estimation from teeth using soft X-ray findings

Soft X-ray photos of 68 premolars and 98 molars from 102 males and 64 females were taken to measure the length (mm) of the corona (CL) and the length of coronal pulp cavity (CPCL). Then the coronal index CI = CPCL x 100/CL after Ikeda et al. (1985) was computed for each tooth and regressed on the actual age of the individuals to obtain equations that allow estimation of age in unknown bodies and isolated teeth. The correlation coefficients ranged from -0.73 (female molars) to -0.89 (female premolars). No significant differences were observed in age estimation using sex-specific equations.

Estimation of age at death from second metacarpals

This study examined the estimation of age at death from the second metacarpal in 227 individuals aged 30-98 years. Variables ascertained from each bone were: cortical thickness and microdensitometric cortical bone density measured on radiographs of the bone and total osteon count and density recorded on microradiographs of the complete cross section at its midshaft. Based on the latter two variables, two age groups were formed; a middle age group representing those individuals aged 30-65 years, and an older group aged 65+. Stepwise regression analysis of the four variables produced a series of regression equations for age estimation for the middle, old and combined age groups for each sex and sexes combined. Sex-specific equations provided better results than nonspecific ones, especially in females. Total osteon density and combined cortical thickness were found to be the most useful estimators in the middle and the old age group, respectively. The standard error of estimate was 6.71 and 6.90 years in each age group for the sexes combined. In the combined age group, age could be estimated accurately from total osteon count, cortical thickness and MD cortical bone density with the standard error of estimate of 11.10 years. The relative error of estimate ranged within +/- 30% in almost all individuals aged above 60 years.

Single- versus dual-energy quantitative computed tomography for spinal densitometry in patients with rheumatoid arthritis

Lumbar bone mineral density was measured by both single- and dual-energy quantitative computed tomography in 109 patients with rheumatoid arthritis. The results were corrected for the age-related increase in vertebral fat content by converting them to percentages of expected densities, using sex and energy-level specific regression equations obtained in a normal reference population. The percentages of expected density are approximately 10% lower in the single- than in the dual-energy mode, both in the patients with and without prednisone therapy. This difference is statistically highly significant, and is positively correlated with the duration of the disease and with the degree of radiological joint destruction. The data suggest that the vertebral fat content may be increased in patients with rheumatoid arthritis, as a consequence of disease-dependent mechanisms.

Histologic estimation of age at death using the anterior cortex of the femur

This report describes a new histologic method for determination of age at death, the latest in a series of studies that began with Kerley's pioneer presentation in 1965. The study population was collected from 328 documented individuals from an anatomy dissecting room in the United States, from two modern cemeteries in the Dominican Republic, and from autopsies performed in a Chilean hospital. Undecalcified thin sections 1.0 cm wide were made from specimens taken from the femoral midshaft directly opposite the linea aspera. Five 0.886 mm2 fields were located at the periosteal edge and photographed, mainly for purposes of defining the fields and providing a permanent record. Secondary osteons, type II osteons, osteon fragments, resorption spaces, and non-Haversian canals were recorded as number/mm2, and a 100-space grid was used to measure average percent of unremodeled, osteonal, and fragmental bone. Stepwise regression analysis of the measurements produced a series of regression equations for age estimation for females, males, and sexes combined. Most equations have a standard error of estimate of about 10 years, but the coefficients of determination (r2) range from 0.48 to 0.72. In practice, sex-specific equations gave better results than opposite-sex or nonspecific equations, mainly because males and females differed in the pattern of relations between osteons and osteon fragments with advancing age.

Estimation of &amp;OV0312;O2max from a one-mile track walk, gender, age, and body weight

The purpose of this investigation was to explore an alternative field test to estimate maximal oxygen consumption (VO2max) using a one-mile walk test. VO2max was determined in 343 healthy adult (males = 165, females = 178) subjects 30 to 69 yr using a treadmill protocol (mean +/- SD: VO2max = 37.0 +/- 10.7 ml X kg-1 X min-1). Each subject performed a minimum of two, one-mile track walks as fast as possible. The two fastest walks (T1, T2) with elapsed times within 30 s were used for subsequent analyses. Heart rates were monitored continuously and recorded every one-quarter mile. Multiple regression analysis (best sub-sets) to estimate VO2max (l X min-1) yielded the following predictor variables: track walk-1 time (T1); fourth quarter heart rate for track walk-1 (HR 1-4); age (yr); weight (lb); and sex (1 = male, 0 = female). The best equation (N = 174) was: VO2max = 6.9652 + (0.0091*WT) - (0.0257*AGE) + (0.5955*SEX) - (0.2240*T1) - (0.0115*HR1-4); r = 0.93, SEE = 0.325 l X min-1. Comparing observed and estimated VO2max values in a cross-validation group (N = 169) resulted in r = 0.92, SEE = 0.355 l X min-1. Generalized and sex-specific equations to estimate VO2max (ml X kg-1 X min-1) were also generated. The accuracy of estimation as expressed by SEE was similar among the equations. The results indicate that this one-mile walk test protocol provides a valid sub-maximum assessment for VO2max estimation.

Estimation of total body water by bioelectrical impedance analysis

Total body water (TBW) measured by bioelectrical impedance analysis (BIA) was directly compared with deuterium-isotope dilution in a total of 58 subjects. First, sex-specific and group equations were developed by multiple regression analysis in (10 each) obese and nonobese men and women. Height2/resistive impedance was the most significant variable used to predict deuterium-dilution space (D2O-TBW) and, combined with weight, yielded R = 0.99 and SE of estimate = 1.75 L. Equations predicted D2O-TBW equally well for obese and nonobese subjects. Second, the equations were prospectively tested in a heterogenous group of 6 males and 12 females. Sex-specific equations predicted D2O-TBW with good correlation coefficients (0.96 and 0.93), total error (2.34 and 2.89 L), and a small difference between mean predicted and measured D2O-TBW (−1.4 ± 2.05 and −0.48 ± 2.83 L). BIA predicts D2O-TBW more accurately than weight, height, and/or age. A larger population is required to validate the applicability of our equations.