Assessment of type A behavior in preschoolers

Teachers and mothers of 219 four-year-old preschoolers assessed their children for Type A behavior pattern using the Matthews Youth Test for Health (MYTH). The sample was derived from five day care centers with Black, White, and Hispanic teachers and students from middle and lower class families. This study indicates that Type A behavior can be identified in four-year-old preschoolers on the basis of ratings by their teachers. A statistically significant difference was found between the ratings of Type A/B characteristics by teachers and those by mothers; however, these were not related to the sex or ethnicity of the children. Repeated measurements of Type A ratings in a subsample of the children at age five showed no significant change among boys or girls. However, repeated measurements at age six on a second subsample showed that boys had lower mean scores, i.e. were more Type B at age six than at age four.     

Boys and girls on the playground: sex differences in social development are not stable across early childhood

Sex differences in human social behaviors and abilities have long been a question of public and scientific interest. Females are usually assumed to be more socially oriented and skillful than males. However, despite an extensive literature, the very existence of sex differences remains a matter of discussion while some studies found no sex differences whereas others reported differences that were either congruent or not with gender stereotypes. Moreover, the magnitude, consistency and stability across time of the differences remain an open question, especially during childhood. As play provides an excellent window into children's social development, we investigated whether and how sex differences change in social play across early childhood. Following a cross-sectional design, 164 children aged from 2 to 6 years old, divided into four age groups, were observed during outdoor free play at nursery school. We showed that sex differences are not stable over time evidencing a developmental gap between girls and boys. Social and structured forms of play emerge systematically earlier in girls than in boys leading to subsequent sex differences in favor of girls at some ages, successively in associative play at 3-4 years, cooperative play at 4-5 years, and social interactions with peers at 5-6 years. Preschool boys also display more solitary play than preschool girls, especially when young. Nevertheless, while boys catch up and girls move on towards more complex play, sex differences in social play patterns are reversed in favor of boys at the following ages, such as in associative play at 4-5 years and cooperative play at 5-6 years. This developmental perspective contributes to resolve apparent discrepancies between single-snapshot studies. A better understanding of the dynamics of sex differences in typical social development should also provide insights into atypical social developments which exhibit sex differences in prevalence, such as autism.     

Circulatory and respiratory responses to muscular exercise in Czech and Norwegian children

This paper presents a comparison between Czech and Norwegian rural healthy children with regard to the functional characteristics of the circulatory and respiratory system based upon work physiological variables and measurements of some pulmonary volumes. The study included randomised samples of boys and girls at the age of 8, 12 and 16 years, 66 Czech boys and 63 girls, 54 Norwegian boys and 57 girls. At the age of 8 years the maximal aerobic power was closely similar in both countries, but in the older age groups the Norwegian children exhibited lower physical fitness. The maximal heart rate was close to 200 min-1 on the average without any sex, age or ethnic differences. In agreement with the higher maximal aerobic power the 12 and 16 year old Czech children had lower submaximal heart rates for the same oxygen uptake than the Norwegian children. The forced vital capacity and forced expiratory volume in one second was significantly higher on the average in Czech than in Norwegian children but the latter, expressed in percent age of the former, averaged 87 to 91% without any sex, age or ethnic differences. The maximal ventilation volumes during muscular exercise reached higher values in Czech than in Norwegian children of the same age, but the mean maximal respiratory rate was close to 60 min-1, being independent of age, sex and cultural differences. During heavy exercise only 40 to 50% of the vital capacity and 45 to 55% of the forced expiratory volume were taken into account and this index of pulmonary function did not differ with sex, age or ethnic differences.     

Sexual dimorphism in bone growth as a function of body size in moderately malnourished Guatemalan preschool age children

The sexual dimorphism in second metacarpal bone growth was investigated in 710 malnourished Guatemalan children one to seven years old to determine if the sex differences seen are only the result of differences in stature and weight. The study sample was mixed-longitudinal and consisted of 1,586 annual examinations. Boys have greater mean stature, weight, periosteal diameter, medullary diameter and cortical area than girls the same age, while girls have greater age specific mean cortical thickness and percent cortical area than boys. When the effects of stature, weight and age are removed boys still have significantly larger periosteal and medullary diameters and less cortical thickness and percent cortical area than girls. These differences between boys and girls therefore cannot be explained by sex differences in body size. However, no sex differences in cortical area remain after accounting for differences in stature, weight and age.     

A factor analysis of cranial base and vault dimensions in children

Lengths within the cranial base and vault were measured in cephalometric radiographs of 220 boys and 177 girls ranging in age from 0 to 15 years; all these children are participants in The Fels Longitudinal Growth Study. The present study is based on mixed longitudinal data derived from 1640 radiographs for boys and 1260 radiographs for girls. Factor analysis was applied separately for boys and girls for each age group; i.e., 0–3, 4–6, 7–9, 10–12, and 13–15 years. For the 0–3 year age group, two factors were extracted in each sex, whereas four factors were extracted in the rest of the age groups. The factor structures are similar in the three older age groups of boys (7–9, 10–12, and 13–15 years). The first four factors for these groups are labelled, respectively: cranial vault size, posterior cranial base length, presphenoid length, and basisphenoid length. The order of the third and fourth factors is reversed in the 7–9 year olds. For girls, the factors extracted were also the same in both the 7–9 and 10–12 year age groups, even though the order of factors was different between age groups; i.e., anterior cranial base length, cranial vault size, basisphenoid length, and basioccipital length. Differential growth rates among cranial base dimensions probably cause changes in factor patterns. Obliteration of the spheno-occipital synchondrosis is suggested as the mechanism responsible for the change of factor pattern in the girls. Closure of this synchondrosis would have occurred too late to affect the patterns in boys.     

Trends in Childhood Obesity in Japan over the Last 25 Years from the National Nutrition Survey

Objective: To describe the 25‐year changes in BMI (measured in kilograms per meters squared) and the prevalence of obesity in Japanese children with special reference to urban‐rural differences. Research Methods and Procedures: We used the data sets from the cross‐sectional annual nationwide surveys (National Nutrition Survey, Japan) conducted from 1976 to 2000 and comprising 29, 052 boys and 27, 552 girls between 6 and 14 years of age. We carried out the trend analyses with the data on sex and age groups and on residential areas according to the size of the municipality (metropolitan areas, cities, and small towns). Results: The mean (age‐adjusted) BMI increased by +0.32 kg/m² per 10 years in boys and by +0.24 kg/m² per 10 years in girls, increases that were remarkable in small towns. The prevalence of obese boys and girls increased from 6.1% and 7.1%, respectively, in the time‐period 1976 to 1980, to 11.1% and 10.2% in 1996 to 2000. The increasing trend was most evident in 9‐ to 11‐year‐old children of both sexes living in small towns, whereas no changes were observed in girls in metropolitan areas. Discussion: Our data clearly show increasing trends in obesity prevalence in Japanese school children. Degrees of the increasing trends, however, differed across sex and age groups and residential areas, demonstrating a particular phenomenon that girls in metropolitan areas were unlikely to become obese. These epidemiological aspects indicate the priorities for intervention in population strategies to control obesity in children.     

Age-related changes and sex differences in postural control adaptability in children during periodic floor oscillation with eyes closed

We investigated age-related changes and sex differences in adaptability of anticipatory postural control in children. Subjects comprised 449 children (4-12 years old) and 109 young adults (18-29 years old). Subjects stood with eyes closed on a force-platform fixed to a floor oscillator. We conducted five trials of 1-minute oscillation (0.5 Hz frequency, 2.5 cm amplitude) in the anteroposterior direction. Postural steadiness was quantified as the mean speed of the center of pressure in the anteroposterior direction (CoPy). In young adults, CoPy speed decreased rapidly until the third trial for both sexes. Adaptability was evaluated by changes in steadiness. The adaptability of children was categorized as "good," "moderate," and "poor," compared with a standard variation of the mean CoPy speed regression line between the first and fifth trials in young adults. Results were as follows: (1) anticipatory postural control adaptability starts to develop from age 6 in boys and 5 in girls, and greatly improves at age 7-8 in boys and 6 in girls; (2) the adaptability of children at age 11-12 (74% of boys and 63% of girls were categorized as "good") has not yet reached the same level as for young adults; (3) the adaptability at age 11-12 for girls is temporarily disturbed due to early puberty.     

Ethnic Differences in Subcutaneous Adiposity and Waist Girth in Children and Adolescents

The purpose of this study was to examine ethnic differences in adiposity as measured by sum of skinfolds (SKF) and waist circumference (WC) in children and adolescents, after statistical adjustment for the BMI and age. A cross sectional sample of 3,218 (55% white, 49% male) children and adolescents aged 5–18 years who participated in the Bogalusa Heart Study (1992–1994) were included in these analyses. Sex‐specific ANOVAs, adjusted for BMI and age, for each 2‐year age group compared measures of adiposity (SKF and WC) between ethnic groups. No significant differences in the proportions of children and adolescents who were overweight and obese by ethnicity or sex were found. Mean SKF in normal weight (P < 0.0001) and overweight (P < 0.0001) categories was higher for white than black children of both sexes. Across most age categories, white boys and girls had significantly higher SKF than black boys and girls, respectively (P ≤ 0.05). Across most age categories, white boys had significantly higher WC than black boys (P ≤ 0.05) with no difference in the girls, when adjusted for BMI and age. Measures of adiposity in childhood and adolescence were significantly higher in white children compared to black children, when adjusted for BMI and age. Throughout childhood and adolescence, white boys and girls had higher SKF and white boys had higher WC. Differences in adiposity between ethnic groups should be considered in disease risk assessment and stratification as they are observed even for a given BMI level.     

Pre-academic and early academic achievement in children with velocardiofacial syndrome (del22q11.2) of borderline or normal intelligence

School-aged children with del22q11.2 tend to show a typical learning and neuropsychological profile, which is characterised by a VIQ-PIQ discrepancy (in favour of the VIQ) and significantly better scores for reading (decoding) and spelling compared to mathematics. To the best of our knowledge, there exists no systematic research on the pre-academic and early academic skills that might underpin these learning difficulties. The purpose of the current study was to investigate more systematically these pre-academic and early academic skills in borderline to normal intelligent (FSIQ > 70) children with del22q11.2 in the last year of kindergarten and first grade of primary school in Flanders. In the kindergarten group, meta-linguistic awareness and counting skills were examined. In the group of first graders, children were tested on reading, spelling and mathematics. Thirteen children (mean age: 6 years 4 months (SD = 0.84); 9 boys, 4 girls) participated in this study. In the present study, there were no differences in intelligence and academic outcomes between boys and girls, and no differences in IQ and academic achievement between children with cardiac defects or severe velopharyngeal insufficiency (VPI) and children without these deficits. With regard to pre-academic achievement in general, a characteristic profile with clearly better results for meta-linguistic awareness in comparison to counting skills was found, but this difference is not statistically significant. Concerning early academic achievement, children with del22q11.2, as a group, perform (despite their somewhat lower general intelligence) on average compared with their age-related peers. However, at an individual level--especially within the domain of counting skills and mathematics--there is a wide variability, with some children showing remarkable learning difficulties already at an early age.     

Sex and age-level differences of walking time in preschool children on an obstacle frame

Background

Stepping over an obstacle is a kind of compound movement that makes walking more difficult, especially for preschool children. This study examines sex and age-level differences in walking time in preschool children on an obstacle frame.

Methods

The participants included 324 healthy preschool children: four-year-old boys (51) and girls (51), five-year-old boys (50) and girls (60), and six-year-old boys (62) and girls (50). A 5 cm- or 10 cm-high obstacle (depth 11.5 cm, width 23.5 cm) was set at the halfway point of a 200 cm × 10 cm walking course.

Results

The participants walked to the end of the course and back as fast as possible under three conditions: no obstacle, low obstacle and high obstacle. Walking time showed age-level differences in all conditions, but there were no differences in sex. Age levels were divided into two groups, with one group within the first six months of their birthday, and the second group within the last six months of that year. Walking time for children in the first half of their fourth year was longer than that of the five- and six-year-old children. In addition, for children in the last half of their fourth year, walking time was longer than both sexes in the last half of their fifth and sixth years. The children in the latter half of their fifth year had a longer walking time in the high obstacle condition than those in the last half of their sixth year. In the four-year-old participants, walking time was shorter with no obstacles than with a high obstacle frame.

Conclusions

In the above data, obstacle course walking time does not show a gender difference, except that the four-year-old participants needed longer than the five- and six-year-old children. Setting the obstacle 10 cm high also produced a different walking time in the five- and six-year-old participants. The high obstacle step test (10 cm) best evaluated the dynamic balance of preschool children.     

Growth of lowland native children of European Ancestry during sojourn at high altitude (3,200 m)

The moderate growth retardation frequently observed among children living at high altitude is usually assumed to result from hypoxic stress. However, such children are frequently from the poorer socioeconomic strata of their societies and may suffer malnutrition, poor hygiene, inadequate medical care, and overcrowding—factors also associated with growth retardation. The objective of this study was to determine if there is a statistically observable alteration in the growth of middle-class children of European ancestry during sojourn at high altitude. Semilongitudinal height/weight measurements were gathered retrospectively from medical records of 18 boys and 17 girls who were born at low altitude, were well-nourished and clinically normal, and who had lived at Achoma, Peru (altitude 3,200 m), continuously for 9–36 months. Measurements were divided, by sex, into four cohorts: I (3–6 months at Achoma), II (6–12 months), III (12–18 months), and IV (18–24 months); initial, presojourn, height and weight were also obtained. All heights and weights were normalized with age-specific reference values. Changes in Z scores (ΔZ) during sojourn were calculated for each subject by subtracting the score of the presojourn value from those of cohorts I–IV. Paired t-tests revealed, among the boys, a significant decline in Z score for weight during sojourn in all four cohorts. Weight scores for the girls also declined in all four cohorts, although only the change in cohort III was significant. Height scores showed a decline with time at sojourn in the boys, but in girls there is an initial drop followed by a steady increase to presojourn levels. These results are consistent with the view that moderate hypoxia exerts a primary growth-limiting effect even on healthy, well-nourished children.     

Sex differences in weight in infancy and the British 1990 national growth standards.

OBJECTIVES: To determine if there is a sex difference in infancy in the new British national standards for weight (based on data from 1990). DESIGN: Weight data in a birth cohort were compared with the 1990 standards and Tanner and Whitehouse (1966) standards up to age 12 months. SETTING: Newcastle upon Tyne. SUBJECTS: 3418 term infants. RESULTS: Our cohort showed a mean difference in standard deviation scores of 0.42 between boys and girls (P < 0.0001) when compared with the 1990 standards. Two and a half times as many girls as boys had weights below the 3rd centile during the first year, with an equivalent excess of boys above the 97th centile (P < 0.0001). Similar results were found with Tanner and Whitehouse standards. CONCLUSIONS: These differences could result in substantial sex bias in the identification of poor growth in early childhood. The standards need modification.     

Isometric and isokinetic muscle strength, anthropometry and physical activity in 8 and 13 year old Swedish children

Isometric muscle strength of the hand-grip and of trunk flexion and extension, and isokinetic torque of elbow and knee flexion and knee extension were assessed in a random sample of 8 and 13 year old Swedish children. The results were compared with respect to sex and age in absolute terms and relative to weight, height2 and estimates of lean body mass and cross-sectional muscle area. Daily physical activity was also estimated. The muscle strength variables were in general found to be very similar in the 8 year old boys and girls. In the 13 year old group the boys were generally stronger than the girls, in both absolute and relative terms, except for similar torque values during knee extension. The absolute and relative muscle strength and torque values were higher in the older than in the younger children, with the exception of trunk strength per unit of body weight and of lean body mass, which were similar in boys of both ages and significantly lower in the older than in the younger girls. No significant correlation was found between the estimates of physical activity and isometric and isokinetic muscle strength and torque.     

Sexual dimorphism in growth in the relative length of the forearm and relative knee height during adolescence

There are numerous studies concerning sexual dimorphism in body proportions, but only a few have investigated growth in the relative length of particular segments of the upper and lower limbs during adolescence. The aim of the study is an assessment of sex differences of longitudinal growth in the relative length of the forearm and knee height among adolescents. Sample involved 121 boys and 111 girls, participants of the Wroclaw Growth Study, examined annually between 8 and 18 years of age. Sexual dimorphism in six ratios: forearm length and knee height relatively to: trunk, height, and limb length were analyzed using a two‐way analysis of variance with repeated measurements. The sex and age relative to an estimate of maturity timing (3 years before, and after age class at peak height velocity [PHV]) were independent variables. All of the ratios showed significant sex differences in interaction with age relative to age at PHV. The relative length of the forearm, in boys, did not change significantly with the years relative to age at PHV, whereas in girls, was the lowest in the two first age classes and afterward significantly increased just 1 year before and during the adolescent growth spurt, remaining unchanged in further age classes. For relative knee height no clear pattern for sex differences was noticed. It is proposed that relatively longer forearms, particularly in relation to the trunk in girls, could have evolved as an adaptation to more efficient infant carrying and protection during breastfeeding.     

Height, weight, and lines of arrested growth in young Guatemalan children

A cross-sectional study of height, weight and skeletal maturity as judged from radiographs of hand and wrist, of 1,412 children under seven years of age (694 boys and 718 girls) living in rural Guatemala was performed. Height and weight were compared to standards prepared by the Institute of Nutrition of Central America and Panama (INCAP). Skeletal age was assessed by the Tanner-Whitehouse and the Greulich and Pyle methods. All x-rays were read by the senior author. The children surveyed were significantly shorter and lighter than well noruished Guatemalan children. Differences were evident by age six months and at a maximum by age five years. Both methods showed skeletal age to lag behind chronological age so that the Guatemalan rural children mature at slower rates than either the British children or the Ohio, U.S.A., children, from whom the two sets of standards were developed. Children of both sexes with radio-opaque transverse lines at the metaphysis showed a consistent tendency to be shorter than children without such lines. Boys but not girls showed similar trends for weight. In general, the data are consistent with the view that the physical development in boys is more severely retarded by an adverse environment than that of girls.     

Testosterone measured in infancy predicts subsequent sex-typed behavior in boys and in girls

The testes are active during gestation, as well as during early infancy. Testosterone elevation during fetal development has been shown to play a role in human neurobehavioral sexual differentiation. The role of early postnatal gonadal activation in human psychosexual development is largely unknown, however. We measured testosterone in 48 full term infants (22 boys, 26 girls) by monthly urinary sampling from day 7 postnatal to age 6 months, and related the area under the curve (AUC) for testosterone during the first 6 months postnatal to subsequent sex-typed behavior, at the age of 14 months, using the Pre-School Activities Inventory (PSAI), and playroom observation of toy choices. In boys, testosterone AUC correlated significantly with PSAI scores (Spearman's rho = 0.54, p = 0.04). In addition, play with a train and with a baby doll showed the anticipated sex differences, and play with the train correlated significantly and positively with testosterone AUC in girls (Spearman's rho = 0.43, p = 0.05), while play with the doll correlated significantly and negatively with testosterone AUC in boys (Spearman's rho = -0.48, p < 0.03). These results may support a role for testosterone during early infancy in human neurobehavioral sexual differentiation.     

Obesity,Fasting Plasma Insulin,and C‐Reactive Protein Levels in Healthy Children

Objective: Obesity is associated with hyperinsulinemia and increased level of C‐reactive protein in older children and adults, but little is known about these relationships in very young children. We examined these relationships in healthy 2‐ to 3‐year‐old children. Research Methods and Procedures: Analyses were performed on data from 491 healthy 2‐ to 3‐year‐old Hispanic children enrolled in a dietary study conducted in New York City, 1992 to 1995. Results: Body mass index (BMI), ponderal index, and sum of four skinfolds were highly correlated (r > 0.75) in both boys and girls. Fasting insulin and glucose levels were only modestly correlated (r = 0.37 for boys and r = 0.28 for girls; p < 0.001 for both), but essentially all of the variability in a calculated index of insulin resistance was attributable to variability in fasting insulin level. The correlations of BMI with fasting insulin level were r = 0.16 (p < 0.05) in boys and r = 0.14 (p < 0.05) in girls. In separate multivariate regression analyses adjusting for age and sex, BMI and ponderal index were associated with fasting plasma insulin level (p < 0.001 for both obesity measures). In multivariate regression analyses adjusting simultaneously for age, sex, and either BMI or ponderal index, fasting insulin level, but not these obesity measures, was associated with C‐reactive protein level. Discussion: Obesity is associated with higher fasting insulin level, and fasting insulin is associated with C‐reactive protein level, in healthy 2‐ to 3‐year‐old children.     

Maximal voluntary isometric strength in Danish adolescents 16-19 years of age

The force in maximal voluntary isometric contraction of elbow flexors, knee extensors, trunk flexors, and trunk extensors was measured in a representative sample of Danish school children 16-19 years of age (128 boys and 165 girls). The 16 year old boys were 177.8 cm in height, with a mean increase of 1.4 cm per year up to 19 years, and they weighed 66.0 kg, with a mean increase of 1.8 kg per year up to age 19. The girls were 168.0 cm in height with no increase up to age 19, and their mean weight was 59.6 kg, which increased by 1.8 kg per year up to age 19 (p greater than 0.05). The strength in the four muscle groups for boys a girls respectively was 281 N and 182 N for elbow flexors, 574 N and 419 N for knee extensors, 601 N and 404 N for trunk flexors and 664 N and 499 N for trunk extensors. An increase in strength in the elbow and trunk flexors and a decrease in strength in the trunk extensors in relation to values obtained in 1956 was seen, and a difference in strength per kg lean body mass between the boys and the girls was also observed. The estimated strength per unit cross-sectional area of muscle was 38 N X cm-2 in both boys and girls.     

Sex Differences and Activity of the Left and Right Brain Hemispheres

The problem is reviewed of sex differences and the brain organization of the visual-spatial and verbal-cognitive functions both in adults and in the 5–15-year old children. Characteristic of men are the integral strategy of the face image recognition, specialization of the right hemisphere for visual-spatial functions, and the tonic inhibitory effect of the right hemisphere on the left one. Typical of women are the fragmented type of the image recognition, the equality of the brain hemispheres functions at the unfamiliar face recognition, and predominance of the left hemisphere by accuracy of the object localization in the visual field. It is possible that the general strategy of the recognition in women is not realized due to the right hemisphere submitted to the interfering effect of the left hemisphere. Analysis of sex differences in distribution of verbal functions shows that the capability for the verbal learning at the age of 5 years and older is higher in girls than in boys. Such capability seems to be accounted for by the superiority of the left hemisphere in girls in this type of its activity and by its earlier development and maturation. The phenomenon of semantic paralexia appearing more often in boys is accounted for by inclusion of lexical-semantic fields of the right hemisphere symmetric areas in the verbal-cognitive activity There are reasons to believe that the higher capability in girls for the verbal learning is mainly due to processes of the auditory-verbal integration within the limits of the left hemisphere, whereas this verbal ability in boys depends on the relative predominance of the interhemispheric connections.     

Human sympathoadrenal system and adrenal cortex in prepubertal and pubertal periods

A complex study of the functional state of the sympathoadrenal system and adrenal cortex in 10–15-year-old children of both sexes was carried out using the indices of daily excretion of adrenaline, noradrenaline, 17-ketosteroids, and 17-hydroxycorticosteroids. A synchronism in the functional activity of the mediator component of the sympathoadrenal system as well as of the androgenic and glucocorticoid functions of the adrenal cortex was observed with age and during pubertal development of children. At the same time, heterochronic maturation was observed in the sex groups: in girls at the age of 10 and 12 years and in boys at the age of 14–15 years. The changes of different direction and intensity in the excretion of the studied hormones and hormonal metabolites were observed in the sex and age groups. A sharp increase in the daily excretion of glucocorticoid metabolites accompanied by a considerable decrease in the age index of noradrenaline secretion was observed in 14-and 15-year-old boys from beginning to end of school year; in addition, an increase in the daily excretion of sex hormones was observed at the age of 15 years. In girls, these indices varied within the age range, which points to a more sophisticated neuroendocrine control of physiological functions in girls during puberty.