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Developmental sex differences in verbal learning.

Although sex differences in verbal learning and memory have been reported in adults, much less is known about when these sex differences emerge and how they develop. In this study, 401 boys and 410 girls between the ages of 5 and 16 years were administered the California Verbal Learning Test--Children's Version. Sex differences were found at all age levels. Girls performed better than boys on all of the immediate and delayed recall trials and on the delayed recognition trial. Girls were also more likely than boys to use a semantic clustering strategy and displayed more effective long-term memory mechanisms. Boys made more intrusion errors and displayed greater vulnerability to interference between the 2 test lists. Because boys had higher mean scores on Wechsler Intelligence Scale for Children--Revised Vocabulary, the observed female superiority in verbal learning could not be attributed to sex differences in overall word knowledge.

Adolescent↗

Ethnic and sex differences in the total and differential white cell count and platelet count.

AIM/BACKGROUND: Previous studies have suggested that healthy subjects of African ancestry have lower total white cell counts, neutrophil counts and platelet counts than Caucasian subjects and that, at least among Caucasians, women have higher neutrophil and platelet counts than men. The primary aim of this study was to confirm and quantify the ethnic differences, confirm the sex difference in Caucasians and determine whether there was a similar sex difference in non-Caucasians. A secondary aim was to establish reference ranges for white cell and platelet counts for the different ethnic and sex groups. METHODS: The study population comprised 417 healthy volunteers (201 women and 216 men), of whom 200 were Caucasian, 102 were Afrocaribbean and 115 were African. Full blood counts, including a differential white cell count, were measured using a H.2 automated differential counter. White cell and platelet counts were compared between the three different ethnic groups and between men and women. Reference ranges were determined for each ethnic and sex group. RESULTS: Africans and Afrocaribbeans had lower total white cell, neutrophil and platelet counts than Caucasians and counts were lower in Africans than in Afrocaribbeans. Women had higher neutrophil and platelet counts than men in all ethnic groups. CONCLUSIONS: Sex and ethnic origin should be taken into consideration when assessing white cell and platelet counts.

Adult↗

Sex differences in hemispheric function: implications from a hemispheric time sharing task.

A microcomputer controlled test of hemispheric time sharing was conducted on normal male and female students. Subjects engaged in a unimanual task involving sequential finger movement alone and in two conditions with concurrent cognitive activity. The verbal task interfered more with right than left hand activity in both male and female subjects. The spatial task interfered more with left than right hand activity in male subjects while female subjects did not show any hand differences. Possible sex differences in brain function were discussed.

Adult↗

Sex differences in grade three students' attitudes toward physical activity.

The purpose of this study was to investigate the attitudes children have towards physical activity and whether boys and girls differ significantly. Sex differences were hypothesized on one or more of the subdomains of Grade 3 Children's Attitudes Toward Physical Activity inventory. The 46 boys and 51 girls ranged from 8 to 10 years of age. A multivariate analysis of variance indicated a significant effect for sex, and subsequent univariate analysis indicated that the boys had significantly lower scores than the girls on the Aesthetic subscale. Results were discussed in terms of attitides about activity in physical education classes and continued research with younger children.

Attitude↗

Sex differences in the relative lengths of metacarpals and metatarsals in gorillas and chimpanzees.

Sex differences other than the simple dimorphism in size were documented for the metapodials of two primate species. Lengths of metacarpals and metatarsals were obtained from the skeletons of 64 gorillas and 42 chimpanzees. Length ratios were constructed for all possible pairings of the five bones in each individual hand and foot. For both species, several of these length ratios exhibited substantial differences between the sexes. Body size was not the basis for these sex differences; when specimens of similar size were compared, the sex differences remained. In humans, length ratios for the fingers and toes also have previously been demonstrated to exhibit sex differences, and the length ratio for the index and ring fingers (the 2D:4D ratio) has been shown to correlate with various medical conditions. Various facts suggest that length ratios in human digits are associated with androgen exposure, probably during prenatal development. For gorillas, the metacarpal length ratio showing the largest sex difference was 4Mc:5Mc in both hands, and the metatarsal length ratio showing the largest sex difference was 1Mt:2Mt in the left foot. Sex differences in length ratios also existed for chimpanzees, but they were generally smaller than for gorillas. Apparently, both gorillas and chimpanzees are affected by developmental mechanisms, possibly androgenic mechanisms, similar to those in humans. Analyses of previous measurements [Susman, R.L., 1979 Comparative and functional morphology of hominoid fingers. Am. J. Phys. Anthropol. 50, 215-236] revealed that all components of the rays are not affected equally by whatever mechanisms are responsible for the sex differences in length ratios.

Animals↗

Sex differences in adolescent suicides in Norway, 1990-1992.

All suicides in persons under 20 years in Norway in the time period 1990-1992 (99 males, 30 females) were included in a postmortem case-control study with seven controls for each suicide, focusing on gender differences. Few sex differences between the suicide completers were evident, in spite of the difference in suicide rates (M/F rate ratio = 3.0). Females more often attempted suicide (p = .05), more often wrote farewell notes (p = .03), and used less violent suicide methods (ns). The adjusted risk for suicide related to affective disorders (Female OR = 22,1; Male OR = 24.0, both p = .000) and disruptive disorders (female OR = 14,7, ns; male OR = 5.0, p = .002) differed little, as did the effect of frequent use of alcohol or substances (female OR = 0.4, ns; male OR = 0.4, ns).

Adolescent↗

Sex differences in the escalation of oral phencyclidine (PCP) self-administration under FR and PR schedules in rhesus monkeys.

RATIONALE: Studies with male rats indicate that long access (LgA) vs short access (ShA) to i.v. cocaine and heroin self-administration leads to an escalation of drug intake and a subsequent upward shift of the dose-response function. OBJECTIVE: The purpose of this experiment was to extend these results to male and female rhesus monkeys and oral phencyclidine (PCP) self-administration under fixed-ratio (FR) and progressive-ratio (PR) schedules. METHODS: Adult rhesus monkeys (seven females and nine males) orally self-administered PCP (0.25 mg/ml) and water under concurrent FR 16 FR 16 schedules during daily ShA 3-h sessions. Since females weighed less than males, each liquid delivery (0.6 ml) represented a higher unit dose mg/kg for females than males, but drug concentration mg/ml remained constant. Concurrent PR PR schedules were then used to obtain a concentration-response function (0.125, 0.25, 0.5, and 1.0 mg/ml). Next, PCP and water were available during LgA 6-h sessions under concurrent FR 16 FR 16 schedules for 21 days. The monkeys were then retested under the concurrent FR 16 FR 16 and PR PR conditions during ShA sessions. RESULTS: Under the initial ShA concurrent FR 16 FR 16 schedules, females and males did not differ on PCP deliveries or intake (mg/kg); however, during LgA, males and females had more PCP deliveries compared with ShA. During LgA, males exceeded females in PCP deliveries, but females were higher than males in mg/kg PCP intake. Also, PCP (but not water) deliveries and mg/kg PCP intake significantly increased from the first 3 days to the last 3 days of the 21-day LgA period in both males and females. The subsequent ShA FR 16 FR 16 performance did not differ by sex, but it was significantly elevated above the first ShA period in both sexes. The concentration-response function for PCP break point under the PR PR schedules and PCP intake (mg/kg) were significantly shifted upward during the second (vs first) ShA period, and females' mg/kg intake significantly exceeded males'. CONCLUSIONS: Male and female rhesus monkeys both showed escalation of PCP self-administration during LgA to PCP and during ShA that occurred after (vs before) LgA. Both showed vertical upward shifts in the concentration x intake (mg/kg) function under the PR schedule, and females exceeded males on this measure. These findings with PCP and monkeys are consistent with vertical upward shifts of cocaine dose-response functions in previous escalation studies in male rats and reports of sex differences (F>M) during several other phases of drug abuse.

Administration, Oral↗

Sex differences in access to coronary revascularization after cardiac catheterization: importance of detailed clinical data.

BACKGROUND: Although some studies suggest that access to cardiac procedures may differ by sex, others have found no evidence of gender bias in cardiac care. OBJECTIVE: To study rates of percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery in men and women after cardiac catheterization. DESIGN: Cohort study with prospective data collection. SETTING: Alberta, Canada. PATIENTS: Persons undergoing cardiac catheterization between 1 January 1995 and 31 December 1998 (n = 21 816). MEASUREMENTS: The occurrence of revascularization procedures (PCI or CABG) in the year after cardiac catheterization was measured. Unadjusted revascularization rates, partially adjusted rates (adjusted for clinical variables available in most databases, including administrative databases), and fully adjusted rates (additionally adjusted for extent of coronary artery disease and ejection fraction) were also evaluated. RESULTS: The unadjusted relative risk was 0.67 (95% CI, 0.65 to 0.71) for the end point of any revascularization in women relative to men. The relative risk increased to 0.69 (CI, 0.66 to 0.72) with partial adjustment and to 0.98 (CI, 0.94 to 1.03) with full adjustment, indicating equivalent access to revascularization for men and women. For PCI, the corresponding relative risks were 0.77 (CI, 0.73 to 0.82), 0.84 (CI, 0.80 to 0.89), and 1.02 (CI, 0.96 to 1.08). For CABG surgery, the relative risks were 0.54 (CI, 0.51 to 0.58), 0.51 (CI, 0.48 to 0.55), and 0.93 (CI, 0.87 to 1.01). CONCLUSIONS: In Alberta, Canada, clinical variables fully explain sex differences in rates of revascularization after cardiac catheterization, and misleading conclusions would arise without full adjustment for clinical differences between men and women. Extreme caution is needed in interpreting reports on access to care that use sparsely detailed clinical data sources.

Alberta↗

Sex differences in hypokalaemic and electrocardiographic effects of inhaled terbutaline.

BACKGROUND: Gender differences in the chronotropic effects of infused isoprenaline have previously been described. The aim of the present study was to investigate possible gender differences in hypokalaemic, chronotropic, and electrocardiographic effects of inhaled terbutaline. METHODS: Twenty healthy volunteers (10 female) were recruited (mean age 24 years for women (F) and 22 years for men (M). Subjects were given either inhaled terbutaline 5 mg or placebo in single blind, randomised crossover fashion and the following measurements were made for four hours after inhalation: (a) serum potassium concentration; (b) heart rate; (c) electrocardiographic sequelae (T wave amplitude, Q-Tc interval). The effects of terbutaline on serum potassium was chosen as the primary end point for detecting a 0.3 mmol/l difference between sexes, with a beta error of 0.2 and alpha set at 0.05. RESULTS: The hypokalaemic effects of terbutaline were significantly greater in women, the potassium results (means and 95% CI) being as follows: lowest potassium concentration--F 3.12 (2.96-3.28) mmol/l v M 3.65 (3.49-3.81) mmol/l; percentage change from baseline at one hour--F 15.4% (11.5-19.3%) v M 8.5% (4.6-12.3%); average potassium concentration during the four hours--F 3.39 (3.33-3.46) mmol/l v M 3.78 (3.72-3.85) mmol/l. There was no significant regression between body weight and the potassium response to terbutaline. There were also significant sex differences for T wave, Q-Tc, and heart rate response. The percentage fall in T wave amplitude 30 minutes after terbutaline was: F 44.6% (32.1-57.0%) v M 22.4% (9.9-34.8%). CONCLUSIONS: Women are more sensitive to the hypokalaemic, chronotropic, and electrocardiographic sequelae of inhaled terbutaline.

Administration, Inhalation↗

Apolipoprotein E epsilon4 and impaired episodic memory in community-dwelling elderly people: a marked sex difference. The Hordaland Health Study.

BACKGROUND: Among elderly people without dementia, the apolipoprotein E epsilon4 allele (APOE4) has been associated with cognitive deficit, particularly in episodic memory, but few reports are available on whether this association differs by sex. METHODS: In a community-dwelling Norwegian cohort of 2181 elderly people (55% women), aged 70-74 years, episodic memory was examined in relation to sex and APOE4 zygosity, with the Kendrick Object Learning Test (KOLT). RESULTS: Possession of at least one APOE4 allele had a modest, detrimental effect on episodic memory in women, whereas in men, heterozygotes were unaffected and homozygotes had markedly lower scores across the distribution of KOLT scores. This sex difference was found consistently in all analyses: on comparing means and medians, examining trends across quintiles, and studying the distribution of scores and the risk of cognitive impairment. Results were broadly similar when adjusted for known determinants of cognition and also when severely impaired participants were excluded. The adjusted odds ratio (OR) of cognitive impairment in women was shown to be 1.8 (95% confidence interval (CI): 1.1 to 2.8) for heterozygotes and 1.1 (0.3 to 3.7) for homozygotes; the adjusted OR in men was observed to be 1.1 (0.6 to 2.1) for heterozygotes and 10.7 (4.7 to 24) for homozygotes. CONCLUSIONS: Although the harmful effect of APOE4 on episodic memory was modest in women, the risk was found to occur in about 30%. APOE4 was observed to have a dramatic effect on episodic memory in men, but only in homozygotes, who comprised about 3% of men: the whole male homozygous group showed a marked shift to lower memory scores.

Aged↗

Sex differences and the effects of sex hormones on hemostasis and vascular reactivity.

Thrombus formation and vasospasm are involved in the initiation of acute ischemic events in the heart. Gender differences in persons with coronary artery disease and the incidence of myocardial ischemia have been clearly documented. In addition, it is well established that sex hormones influence the risk of developing coronary artery disease. Epidemiologic studies suggest that estrogen may exert a protective effect, yet the results of recently completed and ongoing prospective trials of estrogen and hormone (estrogen + progesterone) replacement suggest that these hormones can increase thrombotic events in postmenopausal women. This review focuses on sex (gender) differences in hemostasis and vascular reactivity and on the influence that sex hormones have on these physiologic systems. This review takes the novel approach of focusing on sex differences in hemostasis and vascular reactivity in healthy premenopausal women and men of a similar age. By comparing men and women in this age group, the confounding issues of age, pathology, or decline in sex hormone levels are avoided. Animal and in vitro investigations pertinent to examining potential cellular mechanism(s) of sex hormones in mediating these sex differences are discussed. We assume there is a relationship between the normal physiologic and pathologic effects of sex hormones; elucidating sex differences in normal cardiovascular function will help clarify the basis for sex differences in the incidence and manifestations of coronary heart disease and will aid in the future development of gender-specific therapies for cardiovascular disease.

Adult↗

The pituitary-adrenocortical system is not involved in the sex difference in passive avoidance.

UNLABELLED: The hypothesis that sex differences in passive avoidance are related to the sex difference in the pituitary-adrenocortical system was studied. A high dose of dexamethasone (500 microg/kg body weight) was injected in male and female rats in order to suppress the activity of the pituitary-adrenocortical system. Dexamethasone treated animals and controls were tested for retention of passive avoidance at one of 4 different intervals after punishment. The percentage of females re-entering the compartment in which they were previously shocked was significantly higher than the percentage of males, after a retention interval of 60 minutes, but not after an interval of 0 minutes or 15 minutes (Experiment 1). Dexamethasone did not affect this pattern of sex differences. The same sex difference was found after an interval of 24 hours (Experiment 2), and again dexamethasone had no effect on it. However, in males a state-dependent effect of dexamethasone treatment was found in Experiment 2 when animals were given two injections of either dexamethasone or saline, one before the learning trial and one before the retention trial. Within the groups of males given two different injections (Dex-Sal and Sal-Dex) a higher percentage re-entered the shock compartment, when compared with the groups of males given the same injection twice (Sal-Sal and Dex-Dex). CONCLUSIONS: (1) A sex difference in passive avoidance apparently occurs after a certain interval during which the animals are not disturbed. (2) This sex difference does not depend on the integrity of the pituitary-adrenocortical system. (3) State-dependency was observed in males only, indicating that changes in the pituitary-adrenocortical system, as a consequence of dexamethasone treatment, may have a more important stimulus value in males.

Adrenocorticotropic Hormone↗

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.

Arousal↗

Pulse administration of estradiol-17 beta cancels sex difference in behavioral estrogen sensitivity.

No sex differences were found in the capability of estradiol-17 beta (E2) to induce female sexual behaviors in adult gonadectomized rats when it was administered by a pulsatile schedule and followed by progesterone. Administration of E2 in constant-release implants resulted in a clear behavioral sex difference, with females showing higher levels than males. The ovaries of proestrous females were shown to secrete E2 in a pulsatile manner and the schedule of E2 administration which cancelled the behavioral sex difference produced pulses of serum E2 of an amplitude which was within the physiological range. Thus, the sex difference in behavioral E2 sensitivity is dependent upon the manner of E2 administration and if a physiological schedule of E2 administration is employed the sex difference is cancelled.

Animals↗

Sex differences in illness incidence, prognosis and mortality: issues and evidence.

This paper reviews current research and presents new evidence concerning sex differences in morbidity and mortality. Attention is focused primarily on the following topics: (1) sex differences in incidence, prognosis and mortality for several major types of chronic disease, (2) causes of sex differences in morbidity and mortality, (3) sex differences in physician visits and (4) a methodological issue, whether there are sex differences in reporting morbidity. Relationships between sex differences in incidence, prognosis and mortality have been analyzed for various types of cancer, ischemic heart disease and rheumatoid arthritis. There was little or no correlation between sex differences in incidence and sex differences in prognosis. Sex differences in prognosis were generally smaller than sex differences in incidence. In most cases, sex differences in prognosis made a relatively small contribution to sex differences in mortality, and sex differences in incidence were the primary determinant of sex differences in mortality. These patterns indicate that the causes of sex differences in incidence frequently have little effect on sex differences in prognosis. Reasons for this are discussed in the text. The causes of sex differences in morbidity and mortality are discussed, with attention to the contributions of genetic and environmental factors, sex roles, sex differences in stress responses and sex differences in risk-taking and preventive behaviors. One conclusion is that, although men take more risks of certain types, there does not appear to be a consistent sex difference in propensity to take risks or to engage in preventive behavior. Rather sex differences in risk-taking and preventive behavior vary depending on the specific behavior and the culture considered. Sex differences in physician visit rates are influenced by a variety of biological and cultural factors. For example, women's more complex and demanding reproductive functions are a major reason for women's higher rates of physician visits, at least in Western countries. The importance of cultural factors is indicated by the cross-cultural and historical variation in sex differences in physician visit rates. In order to test whether there are sex differences in the reporting of health and illness, discrepancies between self-report and medically-evaluated morbidity measures have been assessed for males and females in twelve studies. These data indicate that sex differences in reporting vary depending on the particular type of morbidity measure considered. For example, for self-ratings of general health women may be more predisposed than men to rate their health poor, but no significant sex differences were observed in reporting of physician visits or hospital admissions. The evidence discussed in this paper illustrates the diversity and complexity of factors that influence sex differences in morbidity and mortality...

Arthritis, Rheumatoid↗

The sex difference of plasma homovanillic acid is unaffected by cross-sex hormone administration in transsexual subjects.

There is a close relationship between the brain and the endocrine system. The brain expresses receptors for sex steroids and is capable of metabolizing these hormones. We explored (1) sex differences in homovanillic acid (HVA), a metabolite of the neurotransmitter dopamine, and (2) the effects of cross-sex steroid administration in transsexual subjects. First, we compared plasma HVA levels between 38 male and 34 female healthy volunteers (not using hormone replacement therapy) of a mean age of 72 years (range 65-84 years). Secondly, we measured plasma HVA levels in 15 male-to-female transsexuals treated with 100 microg ethinyl estradiol/day and 100 mg cyproterone acetate/day for 4 months, and in 17 female-to-male transsexuals treated with testosterone esters (250 mg/2 weeks i.m. for 4 months). Plasma HVA levels were lower in elderly men than in elderly postmenopausal women (geometric mean 25.4 nmol/l (percentile (P)10 4.9; P90 69.8) vs 39.0 nmol/l (19.0; 76.1); P=0.027). In transsexuals before cross-sex hormone administration, genetic males also had lower plasma levels of HVA than genetic females (geometric mean 14.8 nmol/l (P10 7.0; P90 35.0) vs 34.3 nmol/l (21.8; 61.4); P<0.001). Cross-sex hormone administration did not affect plasma HVA in either group (P>0.5). The pretreatment sex difference in plasma HVA was unaffected after 4 months of cross-sex hormone administration (P=0.003). The sex difference in plasma HVA was not reversed by cross-sex hormone administration in transsexuals, and was also preserved in elderly subjects. This indicated that differences in dopamine gene expression were largely unaffected by exposure to sex hormone levels in adulthood, but must rather be explained by a sex difference in genetic factors or by the organizing effects of sex hormones during early development.

Aged, 80 and over↗

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.

Adolescent↗

Sex differences in verbal and spatial ability reconsidered in relation to body size, lung volume, and sex hormones.

Sex differences in verbal and nonverbal abilities were reconsidered in relation to bodily measures and sex hormones in Turkish university students. Perceptual-verbal ability was evaluated using As Test. To assess the nonverbal abilities, the mental rotation test and Cattell's Culture Fair Intelligence Test were used. As expected, the 53 women performed better than men on the As Test; 79 men had a higher mean than the 53 women on the mental rotation task; there was no sex difference on Cattell's IQ Test. Cattell IQs correlated only with tidal volume of lungs. Scores on the As Test did not show significant correlations with body size and lung capacities. Mental rotation was significantly correlated with height, weight, and lung volume. With covariates of height, weight, and vital capacity, sex differences in mental rotation completely disappeared, but the difference on the As Test increased while Cattell IQ remained sex-neutral. With testosterone as covariate, the sex difference on the As test increased but on the mental rotation task disappeared; Cattell IQ was sex-neutral. With covariates of estradiol and progesterone, sex differences on the As test disappeared; mental rotation scores and Cattell IQ were not influenced. Under a combined covariation of height, weight, and testosterone, sex differences in mental rotation reversed, women scoring better than men; after adding estradiol or progesterone instead of testosterone to this model, sex differences on mental rotation completely disappeared, but verbal ability and Cattell IQ were not changed. These results suggest that Cattell's Culture Fair Intelligence Test is unique in resistance to sex differences; perceptual-verbal ability was the most sex-specific mental trait but with dependence on estradiol; mental rotation, on the contrary, was least sex-specific, depending on body size, lung volume, sex hormones, and their combined actions, which explains women's better performance.

Adolescent↗