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PubMed2006

Evidence for sex differences in the relationships of pain, mood, and disability.

UNLABELLED: Disability demonstrates strong univariate associations with pain and negative mood. These relationships are more complex at the multivariate level and might be further complicated by sex differences. We investigated sex differences in the relationships of pain and negative mood to overall disability and to disability in specific functional domains. One hundred ninety-seven consecutive patients with low back, myofascial, neck, arthritis, and fibromyalgia pain were recruited from university pain clinics and completed measures of disability and negative mood. Overall disability and disability in voluntary activities were significantly associated with pain and negative mood (factor score) for both sexes. Significant sex differences emerged in the strength of the disability-mood relationship, with women evincing a stronger relationship. Disability in obligatory activities was also significantly related to pain and negative mood for both sexes; however, there were no sex differences in the strength of these relationships. Mediation analyses indicated that, in men, negative mood partially mediated the relationship between pain and both overall disability and disability in voluntary activities; mediation was not supported for disability in obligatory activities. In women, negative mood fully mediated the relationship between pain and all 3 types of disability. These data suggest that disability is more directly related to pain in men. In women, the effect of pain on disability appears to operate through negative mood. PERSPECTIVE: Results of this study demonstrate that sex differences exist in the relationships of pain, mood, and disability. Men and women might thus benefit from treatment interventions that differentially target these variables.

Adult↗
PubMed2005

Sex differences in Fos protein expression in the neonatal rat brain.

Sex differences in the brain and behaviour are mostly a result of transient increases in testosterone during the perinatal period. Testosterone influences brain development primarily through aromatization to oestradiol and subsequent binding to oestrogen receptors. Although some studies report that steroid hormones regulate the expression of the inducible transcription factor, Fos, in developing brain, it is not known if there is a sex difference in Fos expression. Changes in Fos protein can be used as an indicator of neuronal/genomic activity. Thus, it provides a useful tool to identify brain regions responding directly or indirectly to steroid hormones. In a first experiment, we examined Fos protein expression in the developing male and female rat brain using western immunoblotting. Dissections were taken from male and female rat pups on the day of birth (postnatal day 0; PN 0), PN1, PN5, PN11 or PN20. Although there was no difference on PN 0, males expressed significantly greater levels of Fos protein on PN1, PN5 and PN20. In a second experiment, we localized the sex difference in Fos protein expression using immunocytochemistry. We found that males expressed significantly higher levels of Fos within a variety of brain regions. These data indicate a sex difference in Fos protein expression during brain development, suggesting a potential role for Fos in differentiating male from female rat brain.

Age Factors↗
PubMed1995

A sex difference in synaptic efficacy at the laryngeal neuromuscular junction of Xenopus laevis.

Under physiological conditions, the response of Xenopus laevis laryngeal muscle fibers to nerve stimulation is sexually differentiated; subthreshold potentials are common in males and rare in females. This sex difference in muscle fiber response is correlated with sex differences in vocal behavior. Quantal analyses at male and female laryngeal synapses were performed to determine if there is a sex difference in synaptic strength. Quantal content at laryngeal synapses is significantly higher in females than in males. Values for quantal content in males can be increased by raising extracellular calcium concentration. There is no sex difference in miniature endplate potential amplitude suggesting that ACh receptor number or properties are not different in the sexes. Sex difference in synaptic strength thus appear presynaptic in origin; transmitter release is less in males. Ultrastructural analyses of the laryngeal motor terminal indicate that there is no sex difference in the length of active zones or in the number of channels per length of active zone. Thus, ultrastructural characteristics of the laryngeal motor terminal do not account for the pronounced sex difference in quantal content.

Animals↗
PubMed2000

Are there age and sex differences in the investigation and treatment of heart failure? A population-based study.

BACKGROUND: Heart failure is a serious, common, and growing problem. Hospital admissions, which account for the bulk of health service costs associated with heart failure, are becoming more frequent. AIM: To determine whether management of heart failure differs by age and sex. METHOD: A retrospective case note review of prevalent cases in 16 general practices in West London. Five hundred and eighty-three patients (57% women) with a diagnosis of heart failure were reviewed. RESULTS: Mean age of patients with heart failure was 78 years (SD = 9.5)--74 years at diagnosis (SD = 10)--and was higher for women than men (76 years versus 71 years, P < 0.001). In 32% of patients there was no record of a chest X-ray, electrocardiogram, or echocardiogram to support diagnosis. Echocardiography, performed in 34% of patients, was less likely in older patients in both sexes (test for trend P = 0.04 in women and 0.02 in men) and, overall, in women (29% compared with 40% of men, P = 0.006). Angiotensin-converting enzyme (ACE) inhibitor treatment, recorded in 54% of patients, decreased with age in both sexes (P < 0.001) and, on unadjusted data, was more likely in men than in women (61% compared with 49%, P = 0.005). On adjustment for age, sex differences in the use of echocardiography and ACE inhibitors were reduced and no longer significant. CONCLUSIONS: With increasing age, men and women with heart failure were less likely to have undergone echocardiography or to have received an ACE inhibitor. When account was taken of age, there were no statistically significant sex differences in management; however, because of the demographic distribution of heart failure, women are disproportionately affected by age differences in management. Clinical trials, physician practice, and service developments in heart failure have neglected older people. This balance should be redressed.

Adult↗
PubMed1981

Sex differences in the reporting of symptoms of depression in the general population.

The notion of sex differences in depression is well documented in the clinical literature. The origin of such differences is rather less well understood, though some recent opinion has it that sex differences represent no more than measurement artifact based on social influences on the reporting of emotional symptoms. The present study examined sex differences in the reporting of depressive symptoms in a random sample of a general population. Differences in prevalence were found to exist in the expected direction. Moreover, it was found that sex differences held as prominently for somatic symptoms of depression as for emotional or affective symptoms. This latter point is contrary to predictions which can be made on the basis of the "artifact' theory fo sex differences in depression, and leads to the conclusion that such differences represent a real clinical phenomenon.

Adult↗
PubMed1998

Sex differences in the recall of affective experiences.

Three studies tested hypotheses for sex differences in the recall of life events: differences in (a) affect intensity at encoding, (b) affect intensity at retrieval, (c) rehearsal, (d) detail of encoding, and (e) artifacts such as motivation or verbal ability. In Study 1 (N = 419), women recalled more positive (p < .01) and more negative (p < .05) life events than men. Differences in retrieval mood were not found. Study 2 (N = 55) replicated the recall differences and showed that neither rehearsal nor artifacts were responsible. Sex differences in recalling neutral everyday events also were obtained (p < .05), suggesting that affect intensity was not responsible. In Study 3 (N = 132), affective reactions to events were unrelated to recall, but sex differences in the detail of encoding (p < .001) were related to recall (p < .05). Sex differences in autobiographical memory are reliable and may be due to differences in the detail of encoding.

Affect↗
PubMed2004

Sex differences in spatial ability: a lateralization of function approach.

The current study was designed to examine whether the extent of the male advantage in performance on a spatial task was determined by the extent to which the task was right-hemisphere dependent. Participants included 108 right-handed men and women who completed the mental rotation, waterlevel, and paperfolding tasks, all of which were presented bilaterally. The results partially supported the hypothesis. On the mental rotation task, men showed a right-hemisphere advantage, whereas women showed no hemispheric differences; however, no overall sex differences were observed. On the waterlevel task, men outperformed women, and both men and women showed a right-hemisphere advantage. On the paperfolding task, no sex or hemispheric differences were observed. Although the findings of the current study were mixed, the study provides a framework for examining sex differences across different types of spatial ability.

Adolescent↗
PubMed2000

Sex differences, but no seasonal variations in the hippocampus of food-caching squirrels: a stereological study.

Recent studies have described sex differences in the relative size of the hippocampus that are associated with sex differences in space use in birds and short-lived mammals. A correlation between spatial learning and increased hippocampal volume has also been demonstrated in food-caching animals. Such results suggest that sexually dimorphic spatial learning (sex differences in space use during the breeding season) and seasonal variations in food-caching behavior (spatial memory for cache locations) might correlate with morphological changes in the hippocampus of adult long-lived mammals. We used modern stereological techniques to examine the volume and neuron number of the structures forming the hippocampal complex (dentate gyrus, CA3, and CA1) of wild adult eastern gray squirrels (Sciurus carolinensis) throughout the year. We observed differences in brain size between samples collected at different times of the year (October, January, and June). Our analysis showed sex differences, but no seasonal variations, in the volume of CA1 stratum oriens and stratum radiatum. There were no sex differences or seasonal variations in the relative volume or the number of neurons of any other layer of the structures forming the hippocampal complex. These results confirm the existence of sex differences in the structure of the hippocampus; however, this sexual dimorphism does not vary seasonally in adulthood and is likely to result from developmental processes. These results do not support the hypothesis that seasonal variations in food-caching behavior might correlate with morphological changes, such as variations in volume or neuron number, in the hippocampal complex of adult long-lived mammals.

Age Factors↗
PubMed2006

Sex differences in regret: all for love or some for lust?

Few sex differences in regret or counterfactual thinking are evident in past research. The authors discovered a sex difference in regret that is both domain-specific (i.e., unique to romantic relationships) and interpretable within a convergence of theories of evolution and regulatory focus. Three studies showed that within romantic relationships, men emphasize regrets of inaction over action (which correspond to promotion vs. prevention goals, respectively), whereas women report regrets of inaction and action with equivalent frequency. Sex differences were not evident in other interpersonal regrets (friendship, parental, sibling interactions) and were not moderated by relationship status. Although the sex difference was evident in regrets centering on both sexual and nonsexual relationship aspects, it was substantially larger for sexual regrets. These findings underscore the utility of applying an evolutionary perspective to better understand goal-regulating, cognitive processes.

Adolescent↗
PubMed2000

Sex differences in dog corpus callosum.

Human studies reported sex differences in size and shape of the corpus callosum. These observations have been contested. The purpose of the present study is to investigate possible sex differences in the corpus callosum of dogs. The entire brains including the medulla from 12 female and 9 male adult mongrel dogs were removed and weighed. Total and partial area measurements of the callosum were made from photographic tracings of its outline. The callosum was partitioned into 3 regions; anterior half, posterior half, posterior one-fifth. The total corpus callosum, anterior half, posterior half, and posterior fifth or splenium areas were measured. Sex differences were found. The anterior half, the posterior half, the posterior fifth, and the total callosum were significantly greater in absolute area in males than in females.

Analysis of Variance↗
PubMed2006

Sex differences in mechanomyographic responses to voluntary isometric contractions.

PURPOSE: This study was designed to compare mechanomyography (MMG) and the force relationship during isometric ramp contractions of biceps brachii muscles in females and males to identify sex differences in the MMG responses. METHODS: Subjects (10 females and 9 males; age range, 20-26 yr) were asked to exert an isometric elbow flexion torque from 5 to 80% maximal voluntary contraction (MVC) at a constant rate of 10% MVC per second. The MMG signal was normalized to muscle cross-sectional area (CSA) as measured by ultrasound imaging. RESULTS: MVC and CSA were significantly different between the two sex groups (males>females); however, there was no sex difference in the MVC relative to muscle CSA (MVC/CSA). The root mean squared amplitude of the MMG (RMSMMG) was significantly greater in the male group than the female group. The RMSMMG relative to muscle CSA was also different between the two sex groups (males>females). The sex difference in the RMSMMG/CSA was more pronounced with increasing torque. The torque levels at which the inflection points in the MMG amplitude were located were different between the two sex groups. The mean power frequency (MPF) of the MMG in the female group increased monotonously, which was different from that in the male group. CONCLUSION: Our results suggest that the sex differences in MMG responses and motor unit (MU) activation strategy result from the predominant activity of the MU with slow-twitch fibers and an effective fused tetanus in females. In addition, the sex-related differences in muscle morphology, subcutaneous adipose tissue, and muscle stiffness appear to be insufficiently reflected in the present MMG responses, particularly relative to muscle CSA.

Adult↗
PubMed2001

Sex differences in EEG correlates of a self-reported measure of hemisphere preference.

The present study explored sex differences in hemisphere preference (HP) assessed by the Preference Test (PT) and its EEG correlates. PT is a paper-and-pencil test designed to measure the extent of individuals relaying on right-hemisphere or left-hemisphere cognition. "Study 1" verified sex differences in HP only among subjects with statistical significant differences between mean and/or median of right- respect to left-HP abilities scores. No sex differences in the frequency of right- and left-HP among the 16 to 17% of a cohort of 1,057 young subjects (473 men and 584 women) with a significant HP were registered. Minimal sex-differences were observed in relation to the magnitude of PT score. "Study 2" verified on 34 healthy adults (22 women and 12 men) the sex differences in correlation between PT-defined HP and a more direct index of hemisphere activation such as the alpha power asymmetry derived from resting EEG (vertex reference). In both sexes, PT scores were found to be related with frontal (0.54 women, 0.69 men), but not parietal, alpha power asymmetries. Higher positive correlation of PT score with frontal alpha ratios was reported in both sexes when the median difference of right- respect to left-HP abilities scores in PT score calculation was used. Overall, this study confirmed and extended the evidence on the association between PT-defined HP and frontal, but not parietal, alpha power asymmetries. No significant sex differences were registered in this pattern.

Adolescent↗
PubMed2003

Sex differences in knee cartilage volume in adults: role of body and bone size, age and physical activity.

OBJECTIVE: To test the hypothesis that sex differences in knee cartilage volume may be mediated through body and bone size, age and/or physical activity. METHODS: A cross-sectional convenience sample of 372 subjects (males 43%; mean age 45 yr, range 26-61) was studied. Articular cartilage volumes and bone size were determined at the patella, medial and lateral tibia by processing images acquired in the sagittal plane using T1-weighted fat saturation magnetic resonance imaging. Height, weight, physical activity (lower limb muscle strength, endurance fitness and questionnaire items) and radiographic osteoarthritis (ROA) were measured. RESULTS: Gender explained 33-42% of the variation in knee cartilage volumes (all P < 0.001). Males had 33-42% higher cartilage volume than females at all sites. In the whole group, the magnitude of sex differences decreased to 8-18% after adjustment for body height, weight and bone size, but remained significant (all P < 0.05). Further adjustment for physical activity had no effect on the sex differences. The sex differences in cartilage volume were greater in those aged over 50 compared with those aged under 50 (P < 0.05 for age-sex interaction at all sites) and were independent of ROA. CONCLUSIONS: Men have substantially higher knee cartilage volumes than women. These sex differences appear to be mediated in part by body and bone size but a significant amount remains unexplained. Furthermore, the differences become more marked over the age of 50 yr suggesting that both cartilage development and cartilage loss in later life contribute to sex differences in cartilage volume. Further longitudinal studies in large samples will be required to confirm these findings.

Adult↗
PubMed1996

Searching for sex differences in the vomeronasal pathway.

The sexual differentiation of brain and behavior is reviewed from the findings of sex differences in the vomeronasal pathway. A motivational approach to sex differences in reproductive behavior is stressed by taking into account that sex differences are present in neural networks: from the receptor organ (the vomeronasal organ) to effector nuclei. Sex differences in the brain appear in two morphological patterns. In one, the male presents greater morphological measurements than the female; in the other, the opposite occurs. These two morphological patterns are actively differentiated by gonadal steroids. The functional significance of these two morphological patterns is addressed. Moreover, since the GABA(A) receptor is involved in the organization of sex differences in vomeronasal structures such as the accessory olfactory bulb and in maternal behavior, the role of membrane mechanisms, 5alpha reduced hormones, and neurosteroids in the sexual differentiation process is discussed.

Animals↗
PubMed2001

Sex differences in human olfaction: between evidence and enigma.

The sex of individuals plays an important part in determining their olfactory abilities, with females generally being superior to males. The present review examines the way in which sex differences influence sensitivity, identification, familiarity, and recognition of odours. It also examines whether sex differences are more pronounced with some odours than others, and how sex differences are affected by the manner of testing. Two different explanations for the superiority of females over males in olfaction are evaluated.

Female↗
PubMed1997

Transient sex differences of aromatase (CYP19) mRNA expression in the developing rat brain.

Sex differences in the activity of aromatase cytochrome P450 (CYP19) in the rat brain have been reported during pre- and postnatal development. It is unclear, however, whether these differences are reflected by corresponding differences in specific mRNA levels. To address this question, we have examined aromatase mRNA levels in specific regions of male and female rat brains by means of in situ hybridization (ISH). At prenatal stages of development, i.e. at gestational day 18 (GD18) and GD20, aromatase mRNA was detected in several preoptic, hypothalamic and limbic brain regions. Semiquantitative analysis of aromatase mRNA did not reveal sex differences in any of these regions. In contrast, clear-cut sex differences were determined at postnatal day (PN) 2; male animals expressed significantly more aromatase mRNA in the bed nucleus of stria terminalis (BST) and the sexually dimorphic nucleus of the preoptic area (SDN). Smaller but still significant differences (females > males) were obtained in the medial preoptic area (MPO). At PN6, sex differences of aromatase mRNA signals (males > females) were still present in the BST, but were no longer detectable in the SDN and the MPO. At PN15 and in adult animals, aromatase mRNA levels were similar in BST and medical amygdaloid nucleus of male and female rats. Since aromatase mRNA expression decreases during postnatal development, no ISH signals could be detected anymore in MPO, SDN and ventromedial hypothalamic nucleus. Our results are consistent with the concept that differential regulation of aromatase mRNA expression might be important for the establishment of different neuronal circuitry in male and female animals.

Animals↗
PubMed2000

Sex differences in the prevalence of mobility disability in old age: the dynamics of incidence, recovery, and mortality.

OBJECTIVES: This study examined sex differences in the prevalence of mobility disability in older adults according to the influences of three components of prevalence: disability incidence, recovery from disability, and mortality. METHODS: Participants in a population-based study of older adults from three communities in the United States (N = 10,263) were studied for up to 7 years. Life table methods were used to estimate the influence of each of the three components of disability prevalence in women and men. Sex differences in probabilities for transition states were measured by relative risks derived from a single model using a Markov chain approach. RESULTS: The proportion of disabled women increased from 22% of women aged 70 years to 81% of those aged 90 years. In men, comparable figures were 15% and 57%. Incidence had the greatest impact on the sex differences in disability prevalence until age 90 and older when recovery rates had a greater impact on differences in prevalence. Mortality differences in men and women had only a modest impact on sex differences in disability prevalence. These findings initially seemed to contradict striking sex differences observed in the relative risks for mortality in men compared with women. Subsequent graphical analyses showed that incidence rather than recovery or mortality largely accounted for sex differences in disability prevalence in old age. CONCLUSION: Disability incidence, recovery from disability, and mortality dynamically influence the sex differences in the prevalence of mobility disability. However, incidence has the greatest impact overall on the higher prevalence of disability in women compared with men.

Adult↗
PubMed1980

Sex differences in the ilia of a known sex and age sample of fetal and infant skeletons.

Ilia from a known sex, race, and age sample of fetal and infant skeletons from the collections of the Smithsonian Institution were evaluated for six metric and one nonmetric characters. Three indices calculated from the measurements were analyzed. The nonmetric trait was examined for fit with known sex. The three indices failed to show significant sex differences. The nonmetric trait, Auricular Surface Elevation, proved dependable (91% accurate) for the male Fetal and Six Month age groups.

Age Factors↗