| 1. |
- Jelenkovic, Aline, et al.
(författare)
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Zygosity Differences in Height and Body Mass Index of Twins From Infancy to Old Age : A Study of the CODATwins Project
- 2015
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Ingår i: Twin Research and Human Genetics. - : Cambridge University Press. - 1832-4274 .- 1839-2628. ; 18:5, s. 557-570
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Tidskriftsartikel (refereegranskat)abstract
- A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m(2) in childhood and adolescence and up to 0.2 kg/m(2) in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.
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| 2. |
- Silventoinen, Karri, et al.
(författare)
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The CODATwins Project : The Cohort Description of Collaborative Project of Development of Anthropometrical Measures in Twins to Study Macro-Environmental Variation in Genetic and Environmental Effects on Anthropometric Traits
- 2015
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Ingår i: Twin Research and Human Genetics. - : Cambridge University Press. - 1832-4274 .- 1839-2628. ; 18:4
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Tidskriftsartikel (refereegranskat)abstract
- For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.
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| 3. |
- Jelenkovic, Aline, et al.
(författare)
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Associations between birth size and later height from infancy through adulthood : An individual based pooled analysis of 28 twin cohorts participating in the CODATwins project
- 2018
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Ingår i: Early Human Development. - : Elsevier BV. - 0378-3782 .- 1872-6232. ; 120, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- Background: There is evidence that birth size is positively associated with height in later life, but it remains unclear whether this is explained by genetic factors or the intrauterine environment. Aim: To analyze the associations of birth weight, length and ponderal index with height from infancy through adulthood within mono- and dizygotic twin pairs, which provides insights into the role of genetic and environmental individual-specific factors. Methods: This study is based on the data from 28 twin cohorts in 17 countries. The pooled data included 41,852 complete twin pairs (55% monozygotic and 45% same-sex dizygotic) with information on birth weight and a total of 112,409 paired height measurements at ages ranging from 1 to 69 years. Birth length was available for 19,881 complete twin pairs, with a total of 72,692 paired height measurements. The association between birth size and later height was analyzed at both the individual and within-pair level by linear regression analyses. Results: Within twin pairs, regression coefficients showed that a 1-kg increase in birth weight and a 1-cm increase in birth length were associated with 1.14–4.25 cm and 0.18–0.90 cm taller height, respectively. The magnitude of the associations was generally greater within dizygotic than within monozygotic twin pairs, and this difference between zygosities was more pronounced for birth length. Conclusion: Both genetic and individual-specific environmental factors play a role in the association between birth size and later height from infancy to adulthood, with a larger role for genetics in the association with birth length than with birth weight.
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| 4. |
- Magnusson, Karin, et al.
(författare)
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Is the association between obesity and hip osteoarthritis surgery explained by familial confounding?
- 2018
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Ingår i: Epidemiology. - 1044-3983. ; 29:3, s. 414-420
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Tidskriftsartikel (refereegranskat)abstract
- Background: Familial confounding is confounding due to genetics or environmental exposures shared by family members. We aimed to study whether familial confounding explains the association between body mass index (BMI) and severe hip osteoarthritis (OA). Methods: We linked data from the Norwegian Arthroplasty Registry with the Norwegian Twin Registry on the National ID-number in 2014, generating a population-based prospective cohort study of same-sex twins born between 1915 and 1960 (53.4% females). BMI was calculated from self-reported height/weight. The outcome was incident hip arthroplasty due to OA (follow-up time, 1987-2014; 424 914 person-years). We performed sex-specific co-twin control analyses of dizygotic (N = 5,226) and monozygotic (MZ, N = 3,803) twin pairs using Cox regression models and explored reasons for any familial confounding using bivariate twin models. Results: The mean (SD) BMI was 22.6 (2.96), peak lifetime BMI 25.6 (2.61), and N = 614 had hip surgery due to OA. In cohort analyses, BMI was associated with hip OA for women and men (hazard ratio [HR] = 1.09, 95% confidence intervals [CIs] = 1.06 to 1.11 and HR = 1.08, 95% CI = 1.04 to 1.12, respectively). When adjusting for familial confounding within MZ twins, the association got stronger for women (HR = 1.19; 95% CI = 1.05 to 1.36) but weaker for men (HR = 0.93; 95% CI = 0.75 to 1.16). There was no genetic overlap between BMI and hip OA, yet the familial confounding in men provides suggestive evidence that the association could be explained by shared environmental factors. Conclusion: The association between BMI and hip OA may be explained by familial confounding for men. For women, there was no evidence for familial confounding, consistent with a causal association. See video abstract at, http://links.lww.com/EDE/B336.
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