Prevalence of hepatitis B surface antigen in vaccinated children and controls in rural Nigeria.

OBJECTIVE: To determine the prevalence of hepatitis B surface antigen (HBsAg) amongst vaccinated children and controls aged 1-4 years in a rural community in mid-western Nigeria. METHODS: The vaccinated children had received at least three doses of hepatitis B vaccine. The vaccines included recombinant hepatitis B vaccine at birth and a combined diphtheria, tetanus, pertussis (whole cell) plus hepatitis B (DTPw-HBV) vaccine. HBsAg was determined by a rapid immunoassay method based on the immunochromatographic sandwich principle. Two hundred and twenty-three children and 219 controls were recruited into the study. RESULTS: The prevalence of HBsAg was significantly lower in the vaccinated group (1.3%) than in the control group (4.6%, p=0.04). The prevalence rates were significantly higher in males (p=0.02) and two-year birth cohort (p=0.01). The controls were estimated to be at a six-fold higher risk of being positive for the surface antigen than the vaccinated children. The vaccine effectiveness was estimated to be approximately 80%. CONCLUSION: These results confirm that hepatitis B vaccine protects against hepatitis B surface antigen carriage and confirm immunogenicity of the combined DTPw-HBV vaccine.

Body composition in white adults by dual-energy x-ray absorptiometry, densitometry, and total body water.

Percent body fat (%BF) and fat-free mass (FFM) were determined in 151 adults from the Fels Longitudinal Study by total body scans with a Lunar DPX (DXA), by underwater weighing and residual lung volume with a two-compartment model using body density (Dens), and total body water (TBW) using deuterium dilution. For the DPX, the medium scan mode ensures precision up to 100 kg body wt and for a ratio of weight to stature < or = 0.7214. Because of these specifications, 15% (n = 23) of the original sample of 151 were excluded. Results for 78 women and 50 men are presented. %BFTBW was significantly (P < 0.05) less than %BFDens in women (mean difference 2.7 +/- 4.2%) and %BFDXA in men (mean difference 2.2 +/- 4.3%). No other significant intermethod differences were observed for %BF and FFM estimates. Pairwise regressions showed the lowest SEEs for %BFDens regressed vs %BFDXA (2.3% for men, 3.2% for women) and for FFMDens vs FFMDXA (2.2 kg for men, 1.9 kg for women). For each sex, reliability analyses and limits of agreement for body composition estimates showed less agreement between TBW and either Dens and DXA than between Dens and DXA.

Family size and age at menarche in athletes.

The association between family size and age at menarche was evaluated in 370 university athletes representing seven sports, 291 white and 79 black. Age at menarche, number of children in the family (family size), and birth order were collected retrospectively by questionnaire with a follow-up interview if necessary. The effect of family size on menarche was estimated with linear regression and multiple regression. For each additional sibling in the family-age at menarche was later by 0.17 yr in white athletes, 0.21 yr in black athletes, and 0.16 yr in the total sample (about 2.0-2.5 months). The slopes for white (beta = 0.167) and black (beta = 0.208) athletes did not differ significantly. Controlling for the effects of birth order significantly increased the family size effect in white athletes (beta = 0.221), but not in black athletes (beta = 0.203) or in the total sample (beta = 0.164). The slopes for white and black athletes, after controlling for birth order, also did not significantly differ. Thus, after controlling for birth order, menarche was later by 0.16-0.22 yr (about 2.0-2.6 months) for each additional sibling in the family, which was within the range of family size effects observed in samples of nonathletes and athletes. The family size effect also persists after controlling for maternal age at menarche in a subsample of 134 athletes, thus implying an independent effect of family size. Later ages at menarche observed in athletes may thus be due in part to larger family sizes.

Body size and fatness in young adults in relation to age at menarche.

The relationships among age at menarche, body size, and body composition were considered in university students surveyed in 1970 (n = 342) and 1987 (n = 109). Recalled ages at menarche, stature, weight, and the triceps skinfold thickness were measured. Subjects ranged in age from 17.5 to 22.5 years in both surveys and were divided into four categories by age at menarche: before 12 years, 12.0 through 12.99 years, 13.0 through 13.99 years, and older than 14 years. In both the 1970 and 1987 surveys, later maturers had significantly more linear physiques than those experiencing menarche earlier. Late maturers also showed a tendency to lower values for the body mass index (BMI) and triceps skinfold compared with early maturers. Comparative data for women of the same age from the Fels Longitudinal Study (n = 234) showed similar findings. Women who reached menarche at ages older than 14 years were significantly taller than women with menarcheal ages less than 13 years. Women with menarcheal ages younger than 12 years were significantly heavier and had higher BMIs than those from any older menarcheal category. They also had significantly thicker triceps skinfolds than those with menarcheal ages older than 14 years. © 1992 Wiley-Liss, Inc.

The timing of sexual maturation in a group of US white youths.

The purpose of this study was to present US reference data for chronological ages at which stages of sexual maturation were observed in white youths. Recent serial data from 78 males and 67 females were analyzed to obtain descriptive statistics for the ages at onset of these stages and the mean ages at which the stages are observed. These reference data should assist the identification of white US youths who are maturing at rapid or slow rates and the interpretation of growth data.

Skeletal maturity and body size of teenage Belgian track and field athletes.

Attained skeletal maturity (TW2 RUS method), skeletal maturity relative to chronological age, and body size of national-level Belgian track and field athletes 15 to 18 years of age were considered. Among the 47 male athletes, 29 (62%) were skeletally mature, while 15 (52%) of the 29 female athletes were skeletally mature. There appeared to be a predominance of skeletally mature individuals among male sprinters and jumpers, while a majority of female sprinters were not skeletally mature. Both skeletally mature and immature individuals were rather evenly represented in the other track and field categories, with the exception of female throwers, who were skeletally mature. Mean statures and weights of skeletally mature and immature 16-, 17-and 18-year-old male athletes did not differ significantly, though the skeletally mature tended to be heavier. In contrast, the skeletally mature female athletes, on the average, were taller and heavier than the skeletally immature, although the differences among the small groups were not statistically significant.

Age at menarche in Flemish girls: current status and secular change in the 20th century.

The age at menarche in a national sample of 4894 Flemish schoolgirls was surveyed in 1979-1980. The probit estimate of the mean age at menarche was 13.20 +/- 0.02 years (SD = 1.25 years). This estimate falls well within the range of reported ages at menarche for girls in northwestern Europe, but is slightly later than those for French-speaking girls in Belgium and in France. Status quo secular data for the 20th century indicate a decline in estimated mean ages at menarche of Flemish girls from about 14.3 years before World War II to 13.6 and 13.2 years, respectively, among girls born just before and during the war. Subsequently, mean ages at menarche of Flemish girls are fairly stable between 13.0 and 13.2 years. These secular changes are of the same magnitude as those observed in other European countries.

Bone mineral content and dietary calcium intake in children prescribed a low-lactose diet.

Bone density is related to body size and other factors including dietary calcium intake. The purpose of this study was to determine the effect of a low-lactose, low-calcium diet on the bone mineral content (BMC) of prepubertal children with documented lactose intolerance. Radial BMC was determined by single-photon absorptiometry. Dietary intake was assessed by 24-h recall and two 3-day food records, and weight and height were measured. The group of lactose-intolerant children was compared with a group of healthy children of similar age, gender, race, and size and to the prediction equations based on body size from Chan's Utah children. Nineteen children, ages 9.6 +/- 1.9 years, participated in the study. They were relatively short compared with standards (height Z score, -0.30 +/- 0.83). BMC was 0.428 +/- 0.081 g/cm in the study group versus 0.440 +/- 0.116 g/cm in the comparison group (n = 19; p > 0.05). Both the study group and the size-selected comparison group had lower BMC than the Utah children. The diet of the study group was low in calcium: 84% of the Recommended Dietary Allowance in children < 11 years old and 32% in children > 11. Calcium intake was associated (p = 0.03) with BMC in the study group after adjusting for body size. The low-lactose diet resulted in a low calcium intake, and BMC was associated with calcium intake in prepubertal children with lactose intolerance. Evaluation of dietary calcium intake should be considered in this group of patients, with follow-up dietary counseling, calcium supplementation (diet or medication), and bone density assessment when clinically indicated.

Fat-free mass from dual-energy X-ray absorptiometry and from other procedures.

Fat-free mass (FFM) values were obtained for 99 males and 114 females (8-68 years) who are participants in the Fels Longitudinal Study. These participants were assessed by dual-energy X-ray absorptiometry (DEXA) and by densitometry using (i) a multi-component model including measures of total body water (TBW) and total body mineral (Fels), (ii) a model with age- and sex-specific values for the density of FFM (Lohman), and (iii), a 2-component model (Siri). In males <25 years, the mean DEXA and Siri values were similar, but both were significantly smaller than the Lohman and Fels means. In females <25years, the mean DEXA values are smaller than those from the other methods. In men aged 25-54 years, the mean DEXA and Fels means showed good correspondence, but the Lohman and Siri means were significantly smaller. In women aged 25-54 years, the DEXA means were considerably smaller than those from the Siri, Lohman and Fels models. At ages >54 years, the findings are tentative because of the small sample sizes but they indicate that the DEXA and Fels means are similar in men and that both are larger than the Lohman and Siri means. In women aged >54 years, the DEXA, Siri and Lohman means are similar, but they are smaller than the Fels means. In another overlapping group (50 men; 78 women; 18-67 years), FFM was obtained from TBW and from the Siri method. The technical errors for TBW-Siri comparisons were 1.7 kg (men) and 1.8 kg (women) with large coefficients of reliability (87%, men; 90% women). It was concluded that DEXA estimates of FFM are not interchangeable with those from the other methods tested. These findings are relevant to the selection of methods for the measurement of body composition and the interpretation of the literature.

High frequency energy absorption and the measurement of limb muscle.

High frequency energy absorption (HFEA) is being developed as a portable, inexpensive, non-invasive procedure for the measurement of muscle mass within cross-sections of limbs. The instrument consists of a flexible coil 2.5 cm wide of which the length can be adjusted over a 10 cm range. A series of coils of different lengths has been constructed that are jointly suitable for limbs with circumferences ranging from 20 to 75 cm. To measure HFEA, a coil of appropriate length is attached to a 9v battery that, through an oscillator, produces a frequency varying from 15 MHz (longest coil) to 40 MHz (shortest coil). Zero readings, with the coil set at the same circumference as the limb, are obtained before and after HFEA is measured and they are used to adjust the observed values. HFEA, in theory, is related to the number of electrolytes deep to the coil and almost all these electrolytes are in muscle. Good precision has been demonstrated and the instrument has been successfully validated against saline solutions. A previous model was validated against magnetic resonance images with good results (r2 about 0.8). Further validation of the present model against magnetic resonance images is almost complete; these findings are presented.

Relationships between the Body Mass Index and body composition.

The aims of this study were to evaluate the Body Mass Index (BMI) (weight/stature2) as a proxy for percent body fat (%BF) and to determine its association with fat-free mass (FFM). Multivariate analysis of variance and partial correlations were used to examine relationships between BMI and %BF and FFM from densitometry for 504 men and 511 women, aged 20 to 45 years. Sensitivity/specificity analyses used cut offs of 28 kg/m2 in men and 26 kg/m2 in women for BMI, and 25% in men and 33% in women for %BF. Significantly higher associations existed in each gender between BMI and %BF in the upper BMI tertile than in the lower BMI tertiles. In the lower BMI tertiles, correlations between BMI and FFM were approximately twice as large as those between BMI and %BF. The BMI correctly identified about 44% of obese men, and 52% of obese women when obesity was determined from %BF. BMI is an uncertain diagnostic index of obesity. Results of Receiver Operator Characteristic (ROC) analyses using %BF and total body fat, both provided a BMI of 25 kg/m2 in men and 23 kg/m2 in women as diagnostic screening cut offs for obesity.