Direct Effect Of Sex Research Articles

Are sex differences in the outcome of peritoneal dialysis explained by nurse assistance? A cohort study with data from the Registre de Dialyse Péritonéale de Langue Française.

We aimed to evaluate sex differences in peritoneal dialysis (PD) outcomes and to explore direct and indirect effects of nurse-assisted PD on outcomes. This was a retrospective study using data from the Registre de Dialyse Péritonéale de Langue Française of incident PD patients between 2005 and 2016. Cox proportional hazards modelling was used to analyse transfer to haemodialysis (HD), death, PD failure, peritonitis and renal transplantation. Mediation analyses with a counterfactual approach were carried out to evaluate natural direct and indirect effects of sex on transfer to HD and peritonitis, with nurse-assisted PD as a mediator a priori. Of the 14 659 patients included, there were 5970 females (41%) and 8689 males (59%). Women were more frequently treated by nurse-assisted PD than men [2926/5970 (49.1%) versus 3357/8689 (38.7%)]. In the multivariable analysis, women had a lower risk of transfer to HD [cause-specific hazard ratio {cs-HR} 0.82 {95% confidence interval (CI) 0.77-0.88}], death [cs-HR 0.90 (95% CI 0.85-0.95)], peritonitis [cs-HR 0.82 (95% CI 0.78-0.87)], PD failure [cs-HR 0.86 (95% CI 0.83-0.90)] and a lower chance of undergoing transplant [cs-HR 0.83 (95% CI 0.77-0.90)] than men. There was a direct effect of sex on the risk of transfer to HD [cs-HR 0.82 (95% CI 0.82-0.83)], with an indirect effect of nurse-assisted PD [cs-HR 0.97 (95% CI 0.96-0.99)]. Nurse-assisted PD had no indirect effect on the risk of peritonitis. Our results suggest that compared with men, women have a lower risk of both transfer to HD and peritonitis. Mediation analysis showed that nurse assistance was a potential mediator in the causal pathway between sex and transfer to HD.

Social support drives female dominance in the spotted hyaena.

Identifying how dominance within and between the sexes is established is pivotal to understanding sexual selection and sexual conflict. In many species, members of one sex dominate those of the other in one-on-one interactions. Whether this results from a disparity in intrinsic attributes, such as strength and aggressiveness, or in extrinsic factors, such as social support, is currently unknown. We assessed the effects of both mechanisms on dominance in the spotted hyaena (Crocuta crocuta), a species where sexual size dimorphism is low and females often dominate males. We found that individuals with greater potential social support dominated one-on-one interactions in all social contexts, irrespective of their body mass and sex. Female dominance emerged from a disparity in social support in favour of females. This disparity was a direct consequence of male-biased dispersal and the disruptive effect of dispersal on social bonds. Accordingly, the degree of female dominance varied with the demographic and kin structure of the social groups, ranging from male and female co-dominance to complete female dominance. Our study shows that social support can drive sex-biased dominance and provides empirical evidence that a sex-role-defining trait can emerge without the direct effect of sex.

Toward Understanding Sex Differences in the Prevalence of Posttraumatic Stress Disorder

It is unclear whether the higher prevalence of posttraumatic stress disorder (PTSD) in women than in men is due to sex differences in the prevalence of the exposure to traumatic events or to differences in vulnerability to traumatic events among those exposed to them. We applied mediation and moderated mediation models to a large nationally representative sample of US adults (N = 34,653) drawn from Wave 2 (2004-2005) of the National Epidemiologic Survey on Alcohol and Related Conditions. A model that assumed that the effect of 19 traumatic events was the same across sexes and examined whether sex differences in the prevalence of DSM-IV PTSD were due exclusively to sex differences in exposure to traumatic events predicted similar prevalence of PTSD among men and women (indirect effect standardized β = 0.04, P = .61), contrary to empirical findings. By contrast, a model that allowed the effect of 19 traumatic events on risk of PTSD to vary by gender, while taking into account sex differences in the prevalence of exposure, indicated that, for 13 of the traumatic events, the effect was significantly greater in women than in men (range of standardized β coefficients = 0.02-0.12, P < .05). The total indirect and direct effects of sex on PTSD in this model were, respectively, β = 0.42 (P < .01) and β = -0.03 (P = .76), indicating that all of the effect of sex on PTSD was explained by this moderated mediation model. The higher prevalence of PTSD among women appears to be due mainly to their greater vulnerability to the effects of traumatic events.

Political learning during the 2000 U.S. presidential election: The impact of the campaign on the gender gap in political knowledge

We examine how political campaigns influence individuals’ levels of correct, incorrect, and don’t know responses and the gender gap in political knowledge during the 2000 American presidential campaign. Using data from the 2000 National Annenberg Election Survey (NAES), we demonstrate that as the campaign progresses the electorate provides more correct answers and fewer incorrect answers. Moreover, the political campaign significantly reduces (and possibly eliminates) the direct effect of sex on political knowledge. While the political campaign decreases the number of incorrect answers provided by both men and women, the number of correct answers provided by women increases. Our findings highlight the importance of the political campaign in determining relative levels of political knowledge for men and women.

Condition-dependent tolerance of monoterpenes in an insect herbivore

The ability of a herbivore to tolerate plant defensive chemicals may vary with the herbivore’s energetic state. We investigated the effect of body condition on the survivorship of individual mountain pine beetles, Dendroctonus ponderosae, exposed to host monoterpenes at concentrations comparable to constitutive and induced levels of defence using fumigant exposure. Body condition index was calculated as the residual mass after fitting the relationship between fresh weight and body size. Differences in survivorship among the four monoterpenes tested (α-pinene, myrcene, terpinolene and limonene) were small. Beetles with a higher body condition index survived high monoterpene concentrations better than those in poorer condition. There was no direct effect of sex, but positive effects of body size and fat content on survivorship favoured females, the sex that pioneers attacks on live trees. Higher body condition index corresponded to both higher fat content and fat-free body mass; the same conclusions about monoterpene identity and size-dependent or energy-dependent tolerance of high monoterpene concentrations held if fat or fat-free body mass were used in place of body condition index. This study highlights the need to consider insect body condition in understanding insect–plant interactions.

Defining the genital immune correlates of protection against HIV acquisition: co-infections and other potential confounders

The sexual transmission of HIV is very inefficient, presumably because mucosal immune defences prevent infection after most exposures. Since numerous genital immune factors have antiviral effects in vitro, their elucidation might greatly inform the microbicide and HIV prevention fields, particularly in the context of HIV-exposed but persistently seronegative (ESN) individuals. However, several important confounders must be considered in such research. First, sound epidemiological criteria are needed to define individuals as ESN. Then, since high-risk sexual activity is commonly one of these criteria, its potential impact on genital immunology must be carefully considered, both the direct effects of sex and the secondary immune effects of genital co-infections. This means that it may be very difficult to determine whether differences in genital immunology between ESN and control groups are responsible for HIV protection, or are a consequence of high-risk sexual activity. To overcome this confounding, the demographics and epidemiology of ESN cohorts must be described very carefully, thorough co-infection diagnostics must be performed and, if possible, prospective studies with an endpoint of HIV acquisition should be performed to define the direction of causality.

Individual variation in behavioural plasticity: direct and indirect effects of boldness, exploration and sociability on habituation to predators in lizards.

Little is known about the factors causing variation in behavioural plasticity and the interplay between personality and plasticity. Habituation to predators is a special case of behavioural plasticity. We investigated the direct and indirect effects of boldness, exploration and sociability traits on the habituation ability of Iberian wall lizards, considering exposure and sex effects. Individual boldness was consistent across several non-habituation contexts, but it did not significantly affect habituation. Exploration had a strong direct effect on habituation, with more exploratory individuals being able to habituate faster than less exploratory ones, probably because of their ability to assess risk better. Individual variation in habituation was also affected by sociability, but this was an indirect effect mediated by exposure to the predator. Less social individuals avoided refuges with conspecific cues, increasing exposure to the predator and eventually habituation. Finally, the direct effects of sex (females habituated faster than males) were opposite to its indirect effects through exposure. We conclude that risk assessment, instead of the proactivity-reactivity gradient usually considered in the literature, can affect behavioural plasticity through complex interactions between direct and indirect effects, including exploratory behaviour, degree of exposure to the predator and sex, which represent novel mechanisms generating inter-individual variation in plasticity.

Sex differences in mental rotation and spatial visualization ability: Can they be accounted for by differences in working memory capacity?

Sex differences in spatial ability are well documented, but poorly understood. In order to see whether working memory is an important factor in these differences, 50 males and 50 females performed tests of three-dimensional mental rotation and spatial visualization, along with tests of spatial and verbal working memory. Substantial differences were found on all spatial ability and spatial working memory tests (that included both a spatial and verbal processing component). No significant differences were found in spatial short-term memory or verbal working memory. In addition, spatial working memory completely mediated the relationship between sex and spatial ability, but there was also a direct effect of sex on the unique variance in three-dimensional rotation ability, and this effect was not mediated by spatial working memory. Results are discussed in the context of research on working memory and intelligence in general, and sex differences in spatial ability more specifically.

Higher Rates of Physical Symptoms Among Homeless Women Do Not Appear to be Due to Reporting Bias: A Comment on Ritchey et al. (1991)

Health statistics consistently show women to have higher rates of morbidity than men, particularly for mild conditions (Verbrugge 1976, 1985, 1989). One of the hypothesized explanations of this relationship is that women are more willing than men to report their physical and mental health problems. Although this explanation is inconsistent with most of the available evidence (see below), it needs to be taken very seriously because it raises fundamental questions about the observed gender difference in morbidity and, more generally, the techniques used in data acquisition. In a recent paper in this journal, Ritchey, La Gory, and Mullis (1991) look at the reports of health risks and 24 physical symptoms among 72 homeless men and 28 homeless women. According to Ritchey et al., homelessness is "a natural laboratory" because homeless men are at much greater risk of illness and, as a consequence, "gender differences in reported symptoms should be reversed, attenuated, or erased" (p. 45). Their position is that if women report more symptoms than men, "it would suggest that the higher female morbidity detected in all types of health surveys is influenced greatly by reporting bias" (p. 35). Ritchey et al. find that the number of symptoms reported by homeless women (x =7.86) was significantly greater than the number of symptoms reported by homeless men (x = 5.19). In their final analysis they report that they "isolate the direct effect of sex" by statistically controlling the risk factors related to the experience of physical symptoms (p. 44). The estimated effects of these statistical controls modestly increase the gender difference in the number of symptoms from 2.67 to 2.88. Ritchey et al.

A causal model of sexual arousal to erotic fantasies

To test a causal model derived from discrete affect (Tomkins, 1962) and involvement (Mosher, 1980) theories, 120 male and 121 female subjects responded to four erotic conditions with self‐reports of discrete affects and subjective sexual arousal. The four erotic conditions were (a) recall of a past heterosexual episode, (b) recall of a past masturbatory episode, (c) free sex fantasy, and (d) guided sex fantasy. The model posits (a) a direct effect of sex on sex guilt only; (b) sex guilt and masturbation guilt would have direct effects and indirect effects on sexual arousal; and (c) discrete positive affects would amplify sexual arousal, discrete negative affects would attenuate sexual arousal, and discrete affects would mediate the indirect effects of sex guilt on sexual arousal. Covariance structure analysis (Duncan, 1975; Kenny, 1979) was used to generate path coefficients. Incremental fit indices indicated an excellent goodness of fit of the model. Sex had no significant paths. Sex guilt had both direc...