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Twin Data (twin + data)
Selected AbstractsEvaluating Normal Approximation Confidence Intervals for Measures of 2 × 2 Association with Applications to Twin DataBIOMETRICAL JOURNAL, Issue 1 2003M.M. Shoukri Abstract Twin data are of interest to genetic epidemiologists for exploring the underlying genetic basis of disease development. When the outcome is binary, several indices of 2 × 2 association can be used to measure the degree of within twin similarity. All such measures share a common feature, in that they can be expressed as a monotonic increasing function of the within twin correlation. The sampling distributions of their estimates are influenced by the sample size, the correlation and the marginal distribution of the binary response. In this paper we use Monte-Carlo simulations to estimate the empirical coverage probabilities and evaluate the adequacy of the classical normal confidence intervals on the population values of these measures. [source] Developmental path between language and autistic-like impairments: a twin studyINFANT AND CHILD DEVELOPMENT, Issue 2 2008Katharina Dworzynski Abstract Autism spectrum disorders (ASDs) are diagnosed when individuals show impairments in three behavioural domains: communication, social interactions, and repetitive, restrictive behaviours and interests (RRBIs). Recent data suggest that these three sets of behaviours are genetically heterogeneous. Early language delay is strongly associated with ASD, but the basis for this association and the relationship with individual sub-domains of ASD has not been systematically investigated. In the present study, data came from a population-based twin sample with language development data at 2,4 years, measured by the MacArthur Communicative Development Inventory (MCDI), and data at 8 years using the Childhood Asperger Syndrome Test (CAST). For the total CAST and the three subscales at 8 years, approximately 300 same-sex twin pairs were selected as showing extreme autistic-like traits (ALTs), defined here as pairs in which at least one member of the twin pair scored in the highest 5% of the distribution. Phenotypic analyses indicated that children showing extreme social and communication ALTs (but not the RRBI subscale) at 8 years were below average in language development at 2,4 years. A regression model for selected twin data suggested that genetic influences account for this overlap, but that these effects are only in part mediated by genes that are shared between language and extreme autistic traits. Copyright © 2008 John Wiley & Sons, Ltd. [source] The Moderating Effect of Religiosity on the Genetic Variance of Problem Alcohol UseALCOHOLISM, Issue 9 2010Tanya M. M. Button Background:, Previous studies have demonstrated that the heritability of alcohol-related phenotypes depends upon the social background in which it is measured (e.g., urbanicity, marital status, and religiosity). The aim of the current study was to identify whether religiosity moderated the genetic variance of problem alcohol use in men and women at two time points: adolescence and early adulthood. Method:, Participants were 312 male MZ pairs, 379 female MZ pairs, 231 male DZ pairs, 235 female DZ pairs, and 275 opposite sex DZ pairs participating in the University of Colorado Center on Antisocial Drug Dependence. Religiosity was measured using the Value on Religion Scale (Jessor and Jessor, 1977), and problem alcohol use was measured using the Composite International Diagnostic Interview,Substance Abuse Module (Cottler et al., 1989). Data were analyzed using a model-fitting approach to the twin data. Results:, In adolescence, genetic variance of problem alcohol use decreased significantly with increasing levels of religiosity in both men and women, whereas in early adulthood, religiosity did not moderate the genetic variance of problem alcohol use in either men or women. Conclusion:, Religiosity appears to moderate the genetic effects on problem alcohol use during adolescence, but not during early adulthood. The reduced genetic variance for problem alcohol use in adolescence may be the consequence of greater social control in adolescence than in young adulthood. [source] Influence of genetics on irritable bowel syndrome, gastro-oesophageal reflux and dyspepsia: a twin studyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 11 2007A. LEMBO Summary Background A genetic contribution has been proposed for irritable bowel syndrome (IBS) and gastro-oesophageal reflux disease (GERD), but is controversial. No twin data exist for dyspepsia. Aim To determine the relative contribution of genetic factors in GERD, dyspepsia (upper abdominal pain) and IBS. Methods A total of 986 twin pairs (from initial mail-out response 51%). Both members completed validated symptom and psychological questionnaires; 481 monozygotic pairs [mean (s.d.) age 53 ± 5.8 years] and 505 dizygotic pairs (mean age 54 ± 5.6 years). Results Prevalence of IBS, dyspepsia and GERD was 12%, 10% and 20%, respectively. Polychoric correlation for monozygotic twins for IBS (0.47) and GERD (0.44) were both substantially larger than those for dizygotic twins (0.17 and ,0.37, respectively). Polychoric correlation was slightly lower in monozygotic than dizygotic twins for dyspepsia. Genetic modelling confirmed the independent additive genetic effects in GERD and IBS but not dyspepsia. Estimates of genetic variance were 22% for IBS, 13% for GERD and 0% for dyspepsia, but adjusting for anxiety and depression removed the statistical significance for IBS and GERD. Conclusions There is a genetic contribution to GERD and IBS but not dyspepsia; this may be mediated by the hereditability of anxiety and depression. [source] Analysis of Twin Data Using SASBIOMETRICS, Issue 2 2009Rui Feng Summary Twin studies are essential for assessing disease inheritance. Data generated from twin studies are traditionally analyzed using specialized computational programs. For many researchers, especially those who are new to twin studies, understanding and using those specialized computational programs can be a daunting task. Given that SAS (Statistical Analysis Software) is the most popular software for statistical analysis, we suggest that the use of SAS procedures for twin data may be a helpful alternative and demonstrate that we can obtain similar results from SAS to those produced by specialized computational programs. This numerical validation is practically useful, because a natural concern with general statistical software is whether it can deal with data that are generated from special study designs such as twin studies and if it can test a particular hypothesis. We concluded through our extensive simulation that SAS procedures can be used easily as a very convenient alternative to specialized programs for twin data analysis. [source] Economic Returns to Communist Party Membership: Evidence From Urban Chinese Twins,THE ECONOMIC JOURNAL, Issue 523 2007Hongbin Li This article estimates the returns to membership of the Chinese Communist Party using unique twins data we collected from China. Our OLS estimate shows a Party premium of 10%, but the within-twin-pair estimate becomes zero. One interpretation is that the OLS premium is due to omitted ability and family background. This interpretation suggests that Party members fare well not because of their political status but because of the superior ability that made them Party members. The estimates are also consistent with another interpretation that Party membership not only has its own effect but also has an external effect on siblings. [source] Heritability of Obesity-related Phenotypes and Association with Adiponectin Gene Polymorphisms in the Chinese National Twin RegistryANNALS OF HUMAN GENETICS, Issue 2 2010Juan Lee Summary The purpose of this study was to estimate the heritability of obesity-related phenotypes and investigate the association of adiponectin gene polymorphisms +45T>G and +276G>T with these measures in Chinese twins. 1260 twin pairs were recruited from two cities through the Chinese National Twin Registry System from 2001 to 2005. Two SNPs at the adiponectin locus (+45T>G and +276G>T) were genotyped. Structural equation modeling (SEM) was used to estimate heritability and the best-fitting variance component model. The regular association among all twins was analysed with generalised estimating equations (GEE). Sib-transmission/disequilibrium test (TDT) within dizygotic (DZ) twin pairs discordant for their genotype was performed using SEM. Additive genetic, common and unique environmental (ACE) model-based heritability of body mass index (BMI) was 61%, while additive genetic and unique environmental (AE)-model-based heritability of waist circumference (WC) and waist-hip ratio (WHR) were 75% and 61%, respectively. There was no association of adiponectin gene +45T>G and +276G>T genotypes with obesity-related phenotypes in all twins or discordant DZ twins. Our twins data did not support that there was an association between adiponectin gene polymorphisms +45T>G and +276G>T and the obesity-related phenotypes. Further studies are required to better understand the role of adiponectin gene polymorphisms in obesity. [source] | |||||||||||||