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Joint modeling of intercourse behavior and human fecundability using structural equation models.

ABSTRACT: Human fecundability is defined as the probability of conception during a menstrual cycle among couples at risk for pregnancy. It is highly relevant for understanding human reproduction and represents a series of highly interrelated and timed processes. The statistical literature has recognized the need to incorporate both biological and behavioral factors (Barrett and Marshall, 1969; Dunson and Stanford, 2005) when modeling conception probabilities, given that intercourse during the fertile window is a necessary but not sufficient criterion for conception. The heterogeneity of behaviors such as the timing and frequency of intercourse in a menstrual cycle needs to be considered when estimating conception. Here we propose a joint model of intercourse behavior and human fecundability through a classic conception probability model and a structural equation model (SEM) to accommodate intercourse during the menstrual cycle. The SEM part of the proposed model allows the dependency between intercourse behaviors on consecutive days in a menstrual cycle to vary across days. Consequently, the proposed model can accommodate not only a broad variety of intercourse patterns and dependency structures but also general covariate effects. Finally, we present a detailed analysis of the New York State Angler Cohort Prospective Pregnancy Study to illustrate the proposed methodology.

SUBMITTER: Kim S

PROVIDER: S-EPMC2912701 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Joint modeling of intercourse behavior and human fecundability using structural equation models.

Kim Sungduk S Sundaram Rajeshwari R Buck Louis Germaine M GM

Biostatistics (Oxford, England) 20100219 3

Human fecundability is defined as the probability of conception during a menstrual cycle among couples at risk for pregnancy. It is highly relevant for understanding human reproduction and represents a series of highly interrelated and timed processes. The statistical literature has recognized the need to incorporate both biological and behavioral factors (Barrett and Marshall, 1969; Dunson and Stanford, 2005) when modeling conception probabilities, given that intercourse during the fertile wind ...[more]

PMID: 20173100

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Project description:Study questionDoes sexual intercourse in the implantation time window (5-9 days after ovulation) reduce fecundability?Summary answerAfter adjustment for intercourse in the fecund window and clustering by couple, there was no association between intercourse in the implantation time window and fecundity.What is known alreadyPrevious research has suggested an association between intercourse in the peri-implantation time window (5-9 days after estimated ovulation) and reduced fecundability.Study design, size, durationWe used data from the FERTILI study, a prospective observational study conducted in five European countries, with data collected from 1992 to 1996.Participants/materials, setting, methodsWomen who were experienced in fertility awareness tracking kept a daily diary of cervical mucus observations, basal body temperature measurements, coitus and clinically identified pregnancy. We estimated the day of ovulation as cycle length minus 13 days. From 661 women, 2606 cycles had intercourse during the fecund window (from 5 days before to 3 days after the estimated day of ovulation), resulting in 418 pregnancies (conception cycles). An established Bayesian fecundability model was used to estimate the fecundability ratio (FR) of peri-implantation intercourse on fecundability, while adjusting for each partner's age, prior pregnancy, the couple's probability of conception and intercourse pattern(s). We conducted sensitivity analyses estimating ovulation as cycle length minus 12 days, or alternatively, as the peak day of estrogenic cervical mucus.Main results and the role of chanceThere was no effect of peri-implantation intercourse on fecundability: adjusted FR for three or more acts of peri-implantation intercourse versus none: 1.00, 95% credible interval: 0.76-1.13. Results were essentially the same with sensitivity analyses. There was an inverse relationship between frequency of intercourse in the fecund window and intercourse in the peri-implantation window.Limitations, reasons for cautionWomen with known subfertility were excluded from this study. Many couples in the study were avoiding pregnancy during much of the study, so 61% of otherwise eligible cycles in the database were not at meaningful risk of pregnancy and did not contribute to the analysis. Some couples may not have recorded all intercourse.Wider implications of the findingsWe believe the current balance of evidence does not support a recommendation for avoiding intercourse in the peri-implantation period among couples trying to conceive.Study funding/competing interest(s)No external funding. The authors have no potential competing interests.Trial registration numberN/A.

Project description:The theory of planned behavior (TPB), socio-cognitive model (SCM), and information-motivation-behavioral skills (IMB) model are effective in predicting condom use. However, the adequacy of these three theoretical models in predicting the frequency of condom use (FCU) among young people has not been compared. This cross-sectional study tested the applicability and suitability of these three models in predicting the FCU, and analyzed the relationships among the postulated constructs.Sexually experienced adolescents (n = 410) aged 13-18 completed a survey assessing the TPB, SCM, and IMB model constructs. Participants were students recruited from 18 high schools, randomly selected from the north, south, east, and southeast of Spain. A structural equation modelling (SEM) analysis was applied to test TPB, SCM and IBM and constructs relationships of each model using R.The results of SEM demonstrated that behavioral skills predict behavior via motivation as hypothesized by the IMB model, but not directly via knowledge about condom use and sexually transmitted infections (STIs). Cognitive factors, such knowledge about condom use and STIs as well as condom use self-efficacy, directly predicted the FCU when modeled as per the SCM. According to the TPB, condom use intention was the best predictor of the FCU, and condom use intention was predicted by attitudes toward condom use and subjective norms related to condom use, but perceived control was not directly or indirectly related to the FCU. Based on the data, the TPB becomes the best-fit model for predicting the FCU among young people compared to the SCM and IMB model.From a statistical perspective, the TPB seems to be the most suitable model for predicting the FCU among young people compared to the other models. Overall, key direct predictors of the FCU in adolescents included condom use intention, behavioral skills and cognitive factors, such as STIs knowledge and condom use self-efficacy. The next step should be to test integrative models that include personal, contextual, environmental, and social factors.

Project description:Schizophrenia (SCZ) is a psychiatric disorder of unknown etiology. There is evidence suggesting that aberrations in neurodevelopment are a significant attribute of schizophrenia pathogenesis and progression. To identify biologically relevant molecular abnormalities affecting neurodevelopment in SCZ we used cultured neural progenitor cells derived from olfactory neuroepithelium (CNON cells). Here, we tested the hypothesis that variance in gene expression differs between individuals from SCZ and control groups. In CNON cells, variance in gene expression was significantly higher in SCZ samples in comparison with control samples. Variance in gene expression was enriched in five molecular pathways: serine biosynthesis, PI3K-Akt, MAPK, neurotrophin and focal adhesion. More than 14% of variance in disease status was explained within the logistic regression model (C-value = 0.70) by predictors accounting for gene expression in 69 genes from these five pathways. Structural equation modeling (SEM) was applied to explore how the structure of these five pathways was altered between SCZ patients and controls. Four out of five pathways showed differences in the estimated relationships among genes: between KRAS and NF1, and KRAS and SOS1 in the MAPK pathway; between PSPH and SHMT2 in serine biosynthesis; between AKT3 and TSC2 in the PI3K-Akt signaling pathway; and between CRK and RAPGEF1 in the focal adhesion pathway. Our analysis provides evidence that variance in gene expression is an important characteristic of SCZ, and SEM is a promising method for uncovering altered relationships between specific genes thus suggesting affected gene regulation associated with the disease. We identified altered gene-gene interactions in pathways enriched for genes with increased variance in expression in SCZ. These pathways and loci were previously implicated in SCZ, providing further support for the hypothesis that gene expression variance plays important role in the etiology of SCZ.

Dataset Information

Joint modeling of intercourse behavior and human fecundability using structural equation models.

Publications

Joint modeling of intercourse behavior and human fecundability using structural equation models.

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