Sex differences between the combined and inattentive types of attention-deficit/hyperactivity disorder: An EEG perspective

This study investigated sex differences between the EEGs of Combined and Inattentive types of attention-deficit/hyperactivity disorder (AD/HD) within boys and girls aged 8–12 years. Subject groups included 80 AD/HD Combined type (40 boys and 40 girls), 80 AD/HD Inattentive type (40 boys and 40 girls) and 80 controls (40 boys and 40 girls). An eyes-closed resting EEG was recorded and Fourier transformed to provide estimates for absolute and relative power in the delta, theta, alpha and beta frequency bands, as well as total power and the theta/beta ratio. The boy AD/HD groups, compared with boy controls, had greater absolute and relative theta, greater theta/beta ratio, reduced absolute and relative alpha, and reduced absolute and relative beta. The girl AD/HD groups, compared with girl controls, had greater absolute delta, greater absolute and relative theta, greater theta/beta ratio, greater total power, and reduced relative delta and relative beta. Between AD/HD types, Combined type boys had globally greater absolute and relative theta, greater theta/beta ratio, and less relative alpha than Inattentive type boys. While topographical differences emerged, there were no significant global differences between AD/HD types in girls. That is, EEG differences between AD/HD types are dissimilar in boys and girls. Different EEG maturational patterns between boys and girls also obscure AD/HD-related EEG abnormalities. These results have important implications for our understanding of AD/HD in girls. Ignoring such sex differences may have compromised the value of previous AD/HD investigations, and these sex differences should be recognised in future research.     

Sex differences in FSH-regulatory peptides in pubertal age boys and girls and effects of sex steroid treatment

BACKGROUND: FSH concentrations are higher in girls than in boys before puberty. We hypothesized that steroid-mediated changes in FSH-regulatory proteins underlie the sex differences in FSH secretion and pubertal timing. METHODS: FSH-regulatory proteins, LH, FSH and sex steroids were measured in five boys, 10 girls, and five girls with Turner syndrome before and during sex steroid treatment (girls, 0.05 mg/day estradiol; boys, 5 mg/day testosterone) for up to 4 weeks. Blood was obtained every 15 min from 20.00 to 08.00 h before and during sex steroid treatment. RESULTS: The mean FSH concentration was higher in girls than in boys (P = 0.0044). Activin-A concentrations were greater (P < 0.0001) and inhibin-B concentrations lower (P < 0.0001) in girls compared with boys. Steroid treatment (i) suppressed LH/FSH concentrations in all subjects; (ii) increased the mean activin-A concentration in all but the Turner girls (P = 0.001); and (iii) decreased inhibin-B concentrations in boys (P = 0.005) but not in girls. Total follistatin and follistatin 288 concentrations did not differ by sex. CONCLUSIONS: Sex steroids regulate circulating activin-A and inhibin-B concentrations in children. The lower inhibin-B and higher activin-A concentrations may explain the higher FSH and earlier onset of puberty in girls.     

Adolescent growth events in eight decades of Japanese cohort data: Sex differences

The presence of secular trends in sex differences for the onset or takeoff of the adolescent growth spurt and subsequent (adolescent) growth of Japanese boys and girls were investigated using data published in “The Statistical Report of the School Health Survey” of the Ministry of Education, Science, Sports and Culture, Japan. An optimum kernel regression method was used to derive the biological parameters of the adolescent growth curve. The six parameters derived from the regression analysis were age at takeoff (ATO), height at takeoff (HTO), velocity at takeoff (VTO), peak height velocity (PHV), age at PHV (APHV), and height at PHV (HPHV). The sex difference in age at PHV is about 2.1 years. The sex difference in age at takeoff was about 2.1 years starting with the birth year of 1943, but has become almost insignificant with the birth year of 1980. After 1960, the sex difference in mean HPHV varied within 12–13 cm, but the difference in HTO showed a decreasing trend. After the birth year of 1911, the rate of growth at HTO for girls has become markedly greater than for boys. In contrast, the rate of growth at HPHV for girls has become significantly smaller than for boys (P < 0.05). Sex differences in ATO, HTO and VTO were significantly and negatively correlated with differences in APHV and HPHV, but positively correlated with the difference in PHV. The sex difference in PHV had no relationship with the differences in APHV and HPHV. Am. J. Hum. Biol. 13:390–397, 2001. © 2001 Wiley‐Liss, Inc.     

A longitudinal analysis of sex differences in bone mineral accrual in healthy 8-19-year-old boys and girls

Background: Although early in life there is little discernible difference in bone mass between boys and girls, at puberty sex differences are observed. It is uncertain if these differences represent differences in bone mass or just differences in anthropometric dimensions. Aim: The study aimed to identify whether sex independently affects bone mineral content (BMC) accrual in growing boys and girls. Three sites are investigated: total body (TB), femoral neck (FN) and lumbar spine (LS). Subjects and methods: 85 boys and 67 girls were assessed annually for seven consecutive years. BMC was assessed by dual energy X-ray absorptiometry (DXA). Biological age was defined as years from age at peak height velocity (PHV). Data were analysed using a hierarchical (random effects) modelling approach. Results: When biological age, body size and body composition were controlled, boys had statistically significantly higher TB and FN BMC at all maturity levels (p < 0.05). No independent sex differences were found at the LS (p > 0.05). Conclusion: Although a statistical significant sex effect is observed, it is less than the error of the measurement, and thus sex difference are debatable. In general, sex difference are explained by anthropometric difference.     

A longitudinal analysis of sex differences in bone mineral accrual in healthy 8-19-year-old boys and girls

Background : Although early in life there is little discernible difference in bone mass between boys and girls, at puberty sex differences are observed. It is uncertain if these differences represent differences in bone mass or just differences in anthropometric dimensions. Aim : The study aimed to identify whether sex independently affects bone mineral content (BMC) accrual in growing boys and girls. Three sites are investigated: total body (TB), femoral neck (FN) and lumbar spine (LS). Subjects and methods : 85 boys and 67 girls were assessed annually for seven consecutive years. BMC was assessed by dual energy X-ray absorptiometry (DXA). Biological age was defined as years from age at peak height velocity (PHV). Data were analysed using a hierarchical (random effects) modelling approach. Results : When biological age, body size and body composition were controlled, boys had statistically significantly higher TB and FN BMC at all maturity levels ( p < 0.05). No independent sex differences were found at the LS ( p > 0.05). Conclusion : Although a statistical significant sex effect is observed, it is less than the error of the measurement, and thus sex difference are debatable. In general, sex difference are explained by anthropometric difference.     

Sex differences in pubertal growth of the heart

The aim of this study was to determine sex differences in growth of the heart during puberty. Three-year increments of growth of the heart and body structures and functions related to heart size were compared between the sexes. Echocardiographically estimated left ventricular mass (LVM) represented heart size, body surface area (BSA) represented the area supplied by the left ventricle, and diastolic blood pressure (DBP) represented a segment of arterial resistance. Pubertal changes in these and several other parameters were compared in 67 healthy girls and 84 healthy boys followed longitudinally from 11.5 to 14.5 years. Increments were compared by t-tests. Left ventricular mass of boys was larger than in girls. The sex difference was not significant at 11.5 years, but increased during the three pubertal years. LVM increased 26% in girls and 53% in boys (P <.001). During the same period, BSA increased 22% in girls and 29% in boys (P <.001), while DBP increased 6% in girls and 9% in boys (P <.05). The larger increment of BSA and DBP in boys corresponds to the sex difference in the increment of the heart size. These differences account, in part, for the greater increase (P <.001) in physical working capacity in boys compared to girls. Am. J. Hum. Biol. 9:297–302, 1997. © 1997 Wiley-Liss, Inc.     

Preconception sex selection for non-medical reasons:a representative survey from Germany

BACKGROUND: Preconception sex selection for non-medical reasons raises serious moral, legal and social issues. The main concern is based on the assumption that a freely available service for sex selection will distort the natural sex ratio and lead to a severe gender imbalance. However, for a severe gender imbalance to happen, at least two conditions have to be met. First, there must be a significant preference for children of a particular sex, and second, there must be a considerable demand for preconception sex selection. To ascertain whether or not these two conditions are met, we have conducted a survey in Germany. METHODS: As a representative sample of the German population, 1094 men and women aged 18-45 years were asked about their gender preferences and whether or not they could imagine selecting the sex of their children through flow cytometric separation of X- and Y-bearing sperm followed by intrauterine insemination. RESULTS: 58% of respondents stated that they do not care about the sex of their offspring. 30% wish to have a family with an equal number of boys and girls. 4% would like to have more boys than girls, 3% more girls than boys, 1% only boys and 1% only girls. For first-borns, however, there is still a preference for boys over girls. While 75.6% claimed to have no gender preference, 14.2% would like their first child to be a boy and 10.1% would like their first child to be a girl. Whereas 6% could imagine taking advantage of preconception sex selection, 92% found this to be out of the question. Even in the hypothetical case that a medication for sex selection were ever to become available, 90% stated that they would not want to use it. CONCLUSION: Given that a majority does not seem to care about the sex of their offspring and only a minority seem to be willing to select the sex of their children, a freely available service for preconception sex selection for non-medical reasons is rather unlikely to cause a severe gender imbalance in Germany.     

GnRH agonist stimulation of the pituitary-gonadal axis in children: age and sex differences in circulating inhibin-B and activin-A

BACKGROUND: Inhibin-B decreases and activin increases FSH secretion in adults. We investigated whether an FSH-inhibin/activin feedback loop exists before or during puberty. METHODS: FSH secretion was stimulated with 10 microg/kg leuprolide acetate (GnRH agonist) in 18 girls, ages 1.0-13.2 years, and 11 boys, ages 8.9-15.2 years, with variations in pubertal development, and in five normal 9- to 10-year-old girls. Blood, obtained at 0, 0.5, 1, 2, 4, 8, 12, 16, 20 and 24 h after GnRH agonist, was analysed for LH, FSH, activin-A, inhibin-A, inhibin-B, follistatin 288 and estradiol/testosterone. RESULTS: FSH increased within 30 min of GnRH agonist administration with a peak greater in girls than boys (P=0.0006). Baseline inhibin-B was greater in boys than girls (P=0.01), while baseline activin-A concentrations were greater in girls. GnRH agonist-stimulated FSH increased inhibin-B in girls by 8 h and in boys by 20 h (P<0.05), but did not affect activin-A. Inhibin-B increases were seen only in girls older than 5 years. CONCLUSIONS: An inhibin-B-FSH feedback loop exists prior to the onset of puberty in girls older than 5 years. Sex differences in activin-A and inhibin-B concentrations may be responsible for sex differences in serum FSH concentrations.     

Individual differences in mood in early childhood: their relation to gender and neonatal sex steroids

Predominant mood states were assessed for 104 children via 24-hr mother diaries during the first 2 years of life. Consistent sex differences were found across ages and across cohorts: boys were more often reported to be in a happy/excited mood, girls in a quiet/calm mood. The sexes did not differ in the frequency of negative moods (including crying), however. Scores for happy/excited and quiet/calm mood states were quite stable across the ages sampled: 6, 9, 12, 18, and 26 months. These stabilities were generally greater for boys. Negative moods showed only borderline stability. Relationships between the mood scores and five sex-steroid hormones (progesterone, androstenedione, testosterone, estrone, and estradiol), assayed from umbilical cord blood at the time of the children's birth, were assessed. For boys small, but significant, positive relationships were found between happy/excited moods and androstenedione, estrone, and progesterone. Correlations of opposite sign were found between these hormones and boys' scores for quiet/calm mood. For girls, the correlations were low and insignificant, but generally of opposite sign from those found for boys, and a number of hormones showed significant sex-by-hormone interactions in their relation to children's mood scores. The implication of these findings for the understanding of sex differences is discussed. Also discussed are the problems of interpretation posed by the intercorrelations among hormones when hormone scores are used for prediction of aspects of later development.     

Assessment and Etiology of Attention Deficit Hyperactivity Disorder and Oppositional Defiant Disorder in Boys and Girls

Attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are more common in boys than girls. In this paper, we investigated whether the prevalence differences are attributable to measurement bias. In addition, we examined sex differences in the genetic and environmental influences on variation in these behaviors. Teachers completed the Conners Teacher Rating Scale-Revised:Short version (CTRS-R:S) in a sample of 800 male and 851 female 7-year-old Dutch twins. No sex differences in the factor structure of the CTRS-R:S were found, implying the absence of measurement bias. The heritabilities for both ADHD and ODD were high and were the same in boys and girls. However, partly different genes are expressed in boys and girls. Edited by Stacey Cherny     

Sex-related differences in immune development and the expression of atopy in early childhood

BACKGROUND: Sex and age are known to influence the clinical expression of asthma and allergic diseases. OBJECTIVE: We sought to evaluate whether immune response profiles also vary by sex and age. METHODS: We performed a prospective birth cohort study (Childhood Origins of Asthma) designed to evaluate interactions among age, sex, immune responses, and virus infections on the development of asthma and allergic diseases. Two hundred eighty-nine subjects were enrolled at birth, and 275 maintained prospective follow-up for 3 years. Cytokine response profiles at birth, 1, and 3 years of age; rates of wheezing, atopic dermatitis, and viral illnesses; and biomarkers of atopy, including total and specific IgE levels and peripheral eosinophil counts, were evaluated. RESULTS: PHA-induced IFN-gamma responses were higher in boys at 1 year of age (median, 35 vs 19 pg/mL; P < .001) and at 3 years of age (median, 282 vs 181 pg/mL; P = .07). Among children who wheezed during the third year of life, boys had increased IFN-gamma, IL-5, and IL-13 responses at age 3 years (P < .001, P = .008, and P = .01, respectively). Boys also demonstrated increased rates of sensitization (P = .05 at year 1), total IgE levels (P = .03 at year 1 and P = .006 at year 3), and peripheral eosinophil counts (2.62 vs 1.85; P = .05 at year 3). CONCLUSION: Sex-specific differences in immune responses develop during early childhood; some of these differences developmentally proceed, whereas others occur in parallel to the clinical expression of various atopic phenotypes. CLINICAL IMPLICATIONS: The differential expression of atopic diseases between boys and girls in early childhood is accompanied by sex-specific differences in immune response profiles.     

Sex differences in behaviour pattern and catecholamine and cortisol excretion in 3-6 year old day-care children

Fifteen boys and eleven girls between three and six years of age were examined at a day-care center and at home as regards their catecholamine and cortisol excretion. Behaviour pattern was assessed by the MYTH-scale, which measures the competitiveness, impatience-anger and aggression components of the type A behaviour pattern in children (Matthews and Angulo, 1980). The boys obtained higher type A scores and excreted more adrenaline and noradrenaline than the girls, while cortisol excretion did not differ between the sexes. In view of previous findings, the results suggest that sex differences in catecholamine excretion in children are induced by sex related differences in behaviour. This relationship in childhood could be of relevance for sex differences in catecholamine responses observed in adulthood. In both sexes, adrenaline excretion was significantly elevated at the day-care center compared with the at-home levels, indicating that mental arousal was greater at the center. In a separate part of the study, eleven new children were tested while they were adjusting to the day-care situation; it was found that only noradrenaline levels during the first week at the center were significantly elevated.     

Gender-related sleep differences in neonates in thermoneutral and cool environments

Although thermoregulation and sleep exhibit gender differences in adults, the question is still debated in neonates. The aim of this study was to examine the relationship between gender-related sleep differences and cool defence mechanisms in neonates. Sleep and thermoregulation were recorded in healthy preterm neonates (21 boys and 17 girls, 37 +/- 2 weeks post-conceptional age) exposed to thermoneutral and cool conditions. Sleep was analysed for continuity and structure. Although the cool exposure did not strongly impair body homeothermia, sleep was altered but without any significant gender difference. However, when data recorded under each of the thermal conditions were pooled, some gender differences emerged: boys slept less, with more wakefulness after sleep onset, more active sleep and less quiet sleep than girls. In contrast to sleep architecture, most of the sleep continuity parameters exhibited greater variability in boys than in girls. This variability may bias the statistical analyses and probably explains the varying conclusions reported in the literature regarding gender-specific sleep-related differences.     

Risk factors for wheezing in early adolescence: a prospective birth cohort study in Brazil.

BACKGROUND: Many asthma studies are available in the literature, but few investigated whether risk factors for asthma differ by sex. OBJECTIVE: To evaluate risk factors for wheezing in early adolescence, with emphasis on sex differences. METHODS: A prospective birth cohort study was initiated in 1993; 87.5% of the original cohort was traced at 11 years, totaling 4,452 adolescents. Current wheezing was defined as at least 1 crisis in the previous 12 months. The following independent variables were analyzed: maternal smoking during pregnancy, wheezing at 4 years, maternal wheezing, and adolescent body mass index. RESULTS: Current wheezing affected 13.5% (95% confidence interval [CI], 12.4%-14.5%) of the cohort. The prevalence of current wheezing was 15.3% (95% CI, 13.7%-16.8%) in boys and 11.7% (95% CI, 10.4%-13.1%) in girls (P < .001). Maternal smoking was related to an increased risk of wheezing for boys but not for girls. There was a significant tracking of wheezing from 4 to 11 years in both sexes, although the magnitude was stronger for boys. A dose-response association between maternal wheezing and adolescent wheezing was observed in boys but not in girls. Finally, obesity was associated with an increased risk of wheezing in boys but not in girls. CONCLUSIONS: The variables explored in this investigation had a stronger effect on adolescent wheezing in boys than in girls. Public health strategies aimed at minimizing the burden of wheezing should take these sex differences into account.     

Urban–rural differences in the growth status of Venezuelan children

The height and weight of 28,752 urban and 10,557 rural individuals aged birth to 18 years were measured as part of a cross-sectional national survey (Project Venezuela) between 1981 and 1986. The Preece-Baines model 1 was fitted to the means; pooled residual mean squares of 0.21 and 0.13 in height and 0.44 and 0.13 in weight, for boys and girls respectively, indicated a good fit. Derived means and biological parameters were compared. The nutritional status of 18,849 children aged birth to 8 years was assessed using the WHO-recommended NCHS/CDC 3rd or 10th and 90th centiles as cut-off points for weight for height, weight for age, and height for age. A t test for proportions was used to test significance. Urban children were taller and heavier than their rural counterparts; differences were evident after age 2 and maximal at 14 years in boys and 12 years in girls, due to differences in tempo, although part of the differences persist into adulthood. Prevalences of wasting and stunting were 3.5% and 10.5% higher in rural children and overweight was 3.6% higher in urban children, significantly so in height for age. A mixed nutritional problem is present in Venezuelans, with a prevalence of stunting greater than that of wasting and a prevalence of overweight greater in urban children. Urban–rural differences in growth persisted into adulthood in boys, while rural girls were similar to urban girls at the end of growth.     

Morbidity in early childhood: differences between girls and boys under 10 years old.

The aim of the study was to investigate the differences in presented morbidity and use of health services among boys and girls in early childhood. The study was performed using data collected by the continuous morbidity registration project of the department of general practice at Nijmegen University. All recorded morbidity, referrals to specialists and admissions to hospitals were recorded by the registration project. The study population included children born in four practices from 1971 to 1984. The children were followed up until the age of five years and if possible until the age of 10 years. The morbidity of the children had been categorized into three levels of seriousness of diagnosis and 15 diagnostic groups as part of the registration project. Boys presented more morbidity than girls in the first years of their lives. For the age group 0-4 years this was true for all levels of seriousness of diagnosis except the most serious. In this younger age group significantly more boys than girls suffered respiratory diseases, behaviour disorders, gastroenteritis and accidents. Girls suffered from more episodes of urinary infection than boys in both age groups. More boys were referred to specialists and admitted to hospital than girls. The findings of this study suggest that not only inborn factors can explain the sex differences in presented morbidity and use of health services in early childhood. In particular, differences between girls and boys in terms of non-serious morbidity and referral and admission rates suggest a different way of handling health problems in boys and girls in early childhood both by parents and doctors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children

Thirty-five prepubertal children, 17 boys and 18 girls, between the ages of 8 and 11 years, were studied to examine electrophysiological and cognitive sex differences during a face-recognition-memory (FRM) task and a facial-affect-identification task (FAIT). All participants were prepubertal, as determined by J. M. Tanner's (1962) staging and endocrine evaluation. Sex-dependent event-related potential (ERP) amplitude asymmetries were found during FRM. Boys displayed greater right versus left ERP amplitude to auditory tone probes during the task, whereas girls displayed the opposite pattern. In addition, positive correlations were obtained between ERP amplitude during FRM and FAIT accuracy scores for boys, but not for girls. Results suggest that girls and boys may use different neuronal systems in the processing of faces and facial affect. Findings are consistent with developmental theories regarding sex differences in visuospatial processing.     

Gender preferences and demand for preconception sex selection: a survey among pregnant women in Pakistan

BACKGROUND: In its recent report 'Human Reproductive Technologies and the Law', the House of Commons' Select Committee on Science and Technology called for greater efforts to establish the potential demographic impact of sex selection across all sectors of UK society. Given the well-known preference for boys over girls among some communities, there is concern that a readily available service for social sex selection may upset the balance of the sexes. Of particular interest are the gender preferences and the demand for sex selection among Pakistanis. METHODS: We conducted a social survey on gender preferences and potential demand for preconception sex selection among 301 pregnant women in Karachi, Pakistan, using a self-report questionnaire consisting of 14 questions. RESULTS: About 41.5% wish to have a family with an equal number of boys and girls; 3.3% would like to have only boys, 1.0% only girls, 27.6% more boys than girls and 4.3% more girls than boys, and 22.3% stated that they do not care about the sex composition of their family. Whereas 6.3% could imagine employing cytometric sperm separation for social sex selection, 76.1% could not and 17.6% were undecided. About 27.2% felt that social sex selection ought to be legal, 48.8% thought it ought to be illegal and 23.9% were undecided. CONCLUSIONS: Although Pakistani women do show a statistically significant preference for boys over girls, the number of women willing to subject themselves to cytometric sperm separation appears to be too small to cause a severe imbalance of the sexes. However, further research among British citizens of Pakistani origin is needed to establish whether sex selection poses a serious threat to the sex ratio of UK communities.     

Neonatal sex-steroid hormones and muscular strength of boys and girls in the first three years

Five sex-steroid hormones were assayed in umbilical cord blood. Strength was assessed in children in three samples at several ages from birth to 33 months. At different ages, different strength measures were taken, viz., at birth, prone head responses; at 3 months, leg strength; from 6 to 33 months, grip strength. Boys had higher average strength scores than girls but the sex differences were small and did not increase or decrease over the age period studied. Across-age strength scores showed a significant relation to androstenedione and a significant interaction of sex and progesterone. Both boys and girls with higher strength scores had lower androstenedione. Girls with high cord blood progesterone showed low strength while boys with high progesterone showed high strength. There were no sex differences in androstenedione or progesterone level. The androstenedione finding did not replicate across samples but the Progesterone X Sex interaction was replicated in all three samples. No relationship was found between strength and other hormones assayed: testosterone, estradiol, and estrone.     

Brief report: the Brazelton Neonatal Behavioral Assessment Scale detects differences among newborn infants of optimal health

OBJECTIVE: To determine whether the Brazelton Neonatal Behavioral Assessment Scale (NBAS) can detect behavioral differences in newborn infants of optimal health and, if such differences appear, also detect gender differences among those neonates. METHODS: Participants were a group of healthy Swedish neonates, 20 boys and 18 girls. The infants were assessed by the NBAS under standardized conditions at 48-72 hours of age, at the midpoint between two meals. RESULTS: All items except those in the dimensions Autonomic System and Motor System had a wide interquartile range. The trend was that girls had higher median item profiles, which means a higher level of functioning than boys. Four out of seven median values in the dimension Social Interactive Organization, as well as the median value in the self-quieting item in the dimension State Regulation, were significantly higher for girls. The interquartile range of the items seemed wider for boys than for girls. CONCLUSIONS: The results indicate behavioral variability among healthy neonates. Gender differences were also observed with girls showing higher levels of functioning than boys.