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Twin Cohort (twin + cohort)
Selected AbstractsHeritability of diurnal type: a nationwide study of 8753 adult twin pairsJOURNAL OF SLEEP RESEARCH, Issue 2 2007MARKKU KOSKENVUO Summary Twin studies suggest a genetic component in diurnal types. In 1981, a questionnaire sent to the Older Finnish Twin Cohort yielded responses from 2836 adult monozygotic (MZ) and 5917 like-sexed dizygotic (DZ) twin pairs with four category self-report on diurnal type. We used structural equation modelling to estimate genetic and environmental components of variance in morningness and eveningness. The model fitting was best when the morningness and the eveningness were analysed together. The ADE-model (including additive genetic, dominant genetic and non-shared environmental effects) fitted best to the data. ADE-models for men and women separately did not differ in a statistically significant manner from the combined model, and similarly ADE-models for young and old age groups separately did not differ either. The estimate for overall genetic effect (broad sense heritability) was 49.7% (95% confidence interval 46.4,52.8), with the remainder accounted for by environmental factors not shared by siblings. The variance component estimates for the underlying liability to diurnal type were 11.7% (95% CI 0,23.7) for additive genetic factors, 38.0% (24.7,51.3) for genetic factors due to dominance. Genetic effects thus account for about one-half of the interindividual variability in diurnal type in adults. [source] Assortative mating by body height and BMI: Finnish Twins and their spousesAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2003Karri Silventoinen Assortative mating by body height and weight is well established in various populations, but its causal mechanisms remain poorly understood. We analyzed the effect of phenotypic assortment and social homogamy on spousal correlations for body height and body mass index (BMI, kg/m2). Our data derived from a questionnaire administered to the adult Finnish Twin Cohort in 1990 (response rate 77%) yielding results from 922 monozygotic and 1,697 dizygotic adult twin pairs who reported information about their body height and weight and that of their spouses. Assortative mating was evident for body height and BMI. For body height, the effects of social homogamy (0.24 in men and 0.29 in women) and phenotypic assortment (0.27 and 0.28, respectively) were about the same. For BMI, the effect of social homogamy was stronger (0.31 in men and 0.28 in women) than the effect of phenotypic assortment (0.13 in both men and women). When assortative mating was taken into account, shared environmental factors had no effect on phenotypic variation in body height or BMI. Our results show that assortative mating needs to be considered in population genetic studies of body height and weight. Am. J. Hum. Biol. 15:620,627, 2003. © 2003 Wiley-Liss, Inc. [source] Alcohol Dependence and Reproductive Onset: Findings in Two Australian Twin CohortsALCOHOLISM, Issue 11 2008Mary Waldron Background:, Although early alcohol use is a strong predictor of future alcohol problems and adolescent drinking is associated with risky sexual behavior predictive of early childbearing, reproductive dysfunctions associated with delayed childbearing have been reported in adult drinkers. We examine the relationship between lifetime history of alcohol dependence (AD) and timing of first childbirth across reproductive development. Methods:, Data were drawn from two cohorts of Australian twins born between 1893 and 1964 (3634 female and 1880 male twins) and between 1964 and 1971 (3381 female and 2748 male twins). Survival analyses were conducted using Cox proportional hazards regression models predicting age at first childbirth from AD, with sociodemographic characteristics, regular smoking, history of psychopathology, and family and childhood risks included as control variables in adjusted models. Results:, Results suggest alcoholic women in both cohorts show overall delayed reproduction, with little effect of AD on timing of first reproduction in men. Effects of AD are particularly strong for women in the older cohort, where AD is associated with 73% decreased likelihood of first childbirth after age 29 [hazard ratio (HR) = 0.27, 95% CI: 0.10,0.75]. In adjusted models, effects reduce only slightly (HR = 0.29, 95% CI: 0.11,0.80). For women in the young cohort, AD is associated with delayed reproduction after age 24, with 40% decreased likelihood of first childbirth (HR = 0.60, 95% CI: 0.48,0.75). AD remains predictive in adjusted models, but without age interaction (HR = 0.72, 95% CI: 0.62,0.85). Conclusions:, Findings of delayed reproductive onset in alcoholic women are consistent with alcohol-related reproductive dysfunctions, although underlying mechanisms remain largely unknown. To better understand AD differences in reproductive onset, continued research on both biological and psychosocial risks is needed. [source] Environmental factors in inflammatory bowel disease: A co-twin control study of a Swedish-Danish twin populationINFLAMMATORY BOWEL DISEASES, Issue 10 2006Jonas Halfvarson MD Abstract Background: Genetics and environmental factors are implicated in the etiology of inflammatory bowel disease (IBD). We studied environmental factors in a population-based Swedish-Danish twin cohort using the co-twin control method. Subjects and Methods: A questionnaire was sent to 317 twin pairs regarding markers of exposures in the following areas: infections/colonization and diet as well as smoking, appendectomy, and oral contraceptives. Odds ratios (OR) were calculated by conditional logistic regression. When confounding appeared plausible, multivariate conditional logistic regression was added. The questions were also divided into topic groups, and adjustment was made for multiple testing within each of the groups. Results: The response rate to the questionnaire was 83%. In consideration of the study design, only discordant pairs were included (Crohn's disease [CD], n = 102; ulcerative colitis [UC], n > = 125). Recurrent gastrointestinal infections were associated with both UC (OR, 8.0; 95% confidence interval [CI], 1.0,64) and CD (OR, 5.5; 95% CI, 1.2,25). Hospitalization for gastrointestinal infections was associated with CD (OR, 12; 95% CI, 1.6,92). Smoking was inversely associated with UC (OR, 0.4; 95% CI, 0.2,0.9) and associated with CD (OR, 2.9; 95% CI, 1.2,7.1). Conclusions: The observed associations indicate that markers of possible infectious events may influence the risk of IBD. Some of these effects might be mediated by long-term changes in gut flora or alterations in reactivity to the flora. The influence of smoking in IBD was confirmed. [source] BCG vaccination and risk of atopic diseases in a twin cohortTHE CLINICAL RESPIRATORY JOURNAL, Issue 2 2008Simon Francis Thomsen No abstract is available for this article. [source] Co-twin control and cohort analyses of body mass index and height in relation to breast, prostate, ovarian, corpus uteri, colon and rectal cancer among Swedish and Finnish twinsINTERNATIONAL JOURNAL OF CANCER, Issue 4 2007Ellen Lundqvist Abstract Associations between anthropometric measures and cancer have been studied previously, but relatively few studies have had the opportunity to control for genetic and early shared environmental factors. In this study, we analyzed 2 twin cohorts from Sweden born 1886,1925 (n = 21,870) and 1926,1958 (n = 30,279) and 1 from Finland born 1880,1958 (n = 25,882) including in total 78,031 twins, and studied the association between BMI and height and risk of prostate, breast, ovarian, corpus uteri, colon and rectal cancer. The cohorts were both analyzed through a co-twin control method and as traditional cohorts. In co-twin control analyses, older obese (BMI , 30 kg/m2) subjects (median age 56 years at baseline) were at higher risk of cancer of the corpus uteri (OR = 3.0; 95% CI 0.9,10.6), colon (OR = 1.9; 95% CI 0.8,4.5) and breast (OR = 2.5; 95% CI 1.3,4.2). For younger obese women (median age 30 years at baseline), an inverse tendency was observed for breast cancer (OR = 0.6; 95% CI 0.3,1.5, p for trend = 0.05). The tallest women had an increased risk of breast (OR = 1.8; 95% CI 1.3,2.7) and ovarian cancer (OR = 1.7; 95% CI 0.8,3.5). No consistent associations were found for prostate cancer either for BMI or height. There are some suggestions in our study that uncontrolled genetic or early shared environmental factors may affect risk estimates in studies of anthropometric measures and cancer risk, but do not explain observations of increased cancer risks related to BMI or height. © 2007 Wiley-Liss, Inc. [source] | ||||||||||