A consistent estimator for logistic mixed effect models

We propose a consistent and locally efficient method of estimating the model parameters of a logistic mixed effect model with random slopes. Our approach relaxes two typical assumptions: the random effects being normally distributed, and the covariates and random effects being independent of each other. Adhering to these assumptions is particularly difficult in health studies where, in many cases, we have limited resources to design experiments and gather data in long‐term studies, while new findings from other fields might emerge, suggesting the violation of such assumptions. So it is crucial to have an estimator that is robust to such violations; then we could make better use of current data harvested using various valuable resources. Our method generalizes the framework presented in Garcia & Ma (2016) which also deals with a logistic mixed effect model but only considers a random intercept. A simulation study reveals that our proposed estimator remains consistent even when the independence and normality assumptions are violated. This contrasts favourably with the traditional maximum likelihood estimator which is likely to be inconsistent when there is dependence between the covariates and random effects. Application of this work to a study of Huntington's disease reveals that disease diagnosis can be enhanced using assessments of cognitive performance. The Canadian Journal of Statistics 47: 140–156; 2019 © 2019 Statistical Society of Canada     

The imbalance of sex-hormones related to depressive symptoms in obese men

Obese men may present hypogonadothrofic hypogonadism, mainly related to higher insulinemia and aromatase activity. Our objectives were to evaluate the relationship of sex-hormones profiles and frequency of depressive symptoms in 43 obese men, in a cross-sectional study. They had 19–60 years, and body mass index 30–50?kg/m². LH, total and free testosterone (TT and FT), estradiol (E₂), sex hormone binding globulin, estradiol/total testosterone ratio (E₂/T) were analyzed. Depressive symptoms were evaluated by “beck depression inventory” (BDI), and significant depression was considered if BDI?≥?16.Thirty-four (80%) presented low TT levels, but only 4 (14%) had low free testosterone and hypogonadism symptoms; 12 of 43 (28%) presented increased E₂. Forty five (56%) presented depressive symptoms, but 16 (28% of the 45) had significant depression. BDI correlated positively with E₂ (r?=?0.407; p?=?0.001) and E₂/T (r?=?0.473; p?=?0.001), but not TT or FT. Patients with significant depressive showed higher levels of estradiol (136?±?48 versus 103?±?48?pg/ml, p?=?0.02) and E₂/T (16.0?±?9.9 versus 9.8?±?4.6; p?=?0.002) (mean?±?SD).In conclusion, obese men may present relatively excess of estradiol and deficiency in testosterone, leading to an imbalance between these two hormones. The greater this imbalance, the more depressive symptoms had our patients.     

A prospective study of adolescent mothers’ social competence,children's effortful control and compliance and children's subsequent developmental outcomes

Previous work has established that caregiver and child temperamental characteristics are associated with child compliance. Given the critical role that parents play in this process, and that children of teen mothers are at risk for poorer developmental outcomes, it is important to understand the development of compliance in the context of at‐risk parenting such as adolescent motherhood. The current study examined child compliance (Wave 5; W5) as a mediator of the association between adolescent mothers’ social competence (Wave 4; W4) and children's behavioral and academic outcomes (Wave 6; W6), and whether this mediation varied depending on children's effortful control (W4) in a sample of 204 Mexican‐origin adolescent mothers (M_age at W4 = 19.94, SD = .99) and their children (M_age at W4 = 36.21 months, SD = .45). Adolescent mothers reported on their own social competence and their children's effortful control and externalizing problems; compliance was assessed using observational methods; and academic readiness was assessed using standardized developmental assessments. Findings based on structural equation modeling revealed that adolescent mothers’ social competence was positively related to children's compliance among children with high effortful control, but not among those with low effortful control. Moreover, child compliance mediated the longitudinal association between adolescent mothers’ social competence and child externalizing problems and academic readiness. Discussion focuses on the importance of considering the role of child temperament in understanding how adolescent mothers’ social competence is subsequently associated with children's social and academic adjustment.     

Dating and Sexual Behavior Among Single Parents of Young Children in the United States

Theory and research on partnered parents suggests trade-offs between parenting and sexuality, with those trade-offs most pronounced among mothers of young children. However, little research has focused on how a growing demographic of single parents negotiates dating and sexual activity. The current study drew upon a 2012 nationally representative sample of 5,481 single Americans 21 years of age and older, of whom 4.3% were parents of a child age five or younger. Dependent variables were sexual thoughts, frequency of sexual activity, number of sexual partners in the past year, dates during the previous three months, and whether one was actively seeking a relationship partner. Covariates included parental age, sex/gender, sexual orientation, education, and income. Using the entire sample of singles, we found no main effects of number (0, 1, 2+) of children aged five years and younger or number of children aged two years and younger on dating and sexual behavior variables. Next, using analyses restricted to single parents (n = 2,121), we found that single parents with a child aged five years or younger, adjusting for covariates, reported greater frequency of sexual activity and first dates but no differences in other outcomes compared with single parents of older children.     

Violence,Networks, and International Migration from Colombia

Although Colombia is a major country of emigration, little is known about its citizens' motivations for migration. Social and economic conditions have been studied as determinants of migration, but violence has received less attention. We examine how social networks and violence function to promote emigration from Colombia by linking event‐history data from the Latin American Migration Project to external data on violence and economic conditions. We show that emigration is more likely to be initiated by those with higher education, those with network connections to migrants, and during periods of greater violence and increased police presence. Although violence acts powerfully to determine when people migrate, the geographic distribution of social capital determines where they go. Not surprisingly, migrants go to locations where people in their social networks are currently living or have been earlier.     

A frailty modeling approach for parental effects in animal breeding

Survival models involving frailties are commonly applied in studies where correlated event time data arise due to natural or artificial clustering. In this paper we present an application of such models in the animal breeding field. Specifically, a mixed survival model with a multivariate correlated frailty term is proposed for the analysis of data from over 3611 Brazilian Nellore cattle. The primary aim is to evaluate parental genetic effects on the trait length in days that their progeny need to gain a commercially specified standard weight gain. This trait is not measured directly but can be estimated from growth data. Results point to the importance of genetic effects and suggest that these models constitute a valuable data analysis tool for beef cattle breeding.     

Empirical Analysis of the Effects of Cyber Security Incidents

We analyze the time series associated with web traffic for a representative set of online businesses that have suffered widely reported cyber security incidents. Our working hypothesis is that cyber security incidents may prompt (security conscious) online customers to opt out and conduct their business elsewhere or, at the very least, to refrain from accessing online services. For companies relying almost exclusively on online channels, this presents an important business risk. We test for structural changes in these time series that may have been caused by these cyber security incidents. Our results consistently indicate that cyber security incidents do not affect the structure of web traffic for the set of online businesses studied. We discuss various public policy considerations stemming from our analysis.