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Twin Research and Human Genetics : the... Dec 2021Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the... (Review)
Review
Although twins often participate in medical research, few clinical trials are conducted entirely in twin populations. The purpose of this review is to demonstrate the substantial benefits and address the key challenges of conducting clinical trials in twin populations, or 'twin-only trials'. We consider the unique design, analysis, recruitment and ethical issues that arise in such trials. In particular, we describe the different approaches available for randomizing twin pairs, highlight the similarity or correlation that exists between outcomes of twins, and discuss the impact of this correlation on sample size calculations and statistical analysis methods for estimating treatment effects. We also consider the role of both monozygotic and dizygotic twins for studying variation in outcomes, the factors that may affect recruitment of twins, and the ethics of conducting trials entirely in twin populations. The advantages and disadvantages of conducting twin-only trials are also discussed. Finally, we recommend that twin-only trials should be considered more often.
Topics: Diseases in Twins; Humans; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35074024
DOI: 10.1017/thg.2021.52 -
NeuroImage Oct 2021How much of the functional organization of our visual system is inherited? Here we tested the heritability of retinotopic maps in human visual cortex using functional... (Comparative Study)
Comparative Study
How much of the functional organization of our visual system is inherited? Here we tested the heritability of retinotopic maps in human visual cortex using functional magnetic resonance imaging. We demonstrate that retinotopic organization shows a closer correspondence in monozygotic (MZ) compared to dizygotic (DZ) twin pairs, suggesting a partial genetic determination. Using population receptive field (pRF) analysis to examine the preferred spatial location and selectivity of these neuronal populations, we estimate a heritability around 10-20% for polar angle preferences and spatial selectivity, as quantified by pRF size, in extrastriate areas V2 and V3. Our findings are consistent with heritability in both the macroscopic arrangement of visual regions and stimulus tuning properties of visual cortex. This could constitute a neural substrate for variations in a range of perceptual effects, which themselves have been found to be at least partially genetically determined. These findings also add convergent evidence for the hypothesis that functional map topology is linked with cortical morphology.
Topics: Adolescent; Adult; Biological Variation, Individual; Brain Mapping; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Photic Stimulation; Quantitative Trait, Heritable; Twins, Dizygotic; Twins, Monozygotic; Visual Cortex; Visual Fields; Young Adult
PubMed: 34153449
DOI: 10.1016/j.neuroimage.2021.118286 -
The Australian & New Zealand Journal of... Oct 2016
Topics: Female; Humans; Maternal Age; Pregnancy; Pregnancy, Twin; Single Embryo Transfer; Twins, Dizygotic
PubMed: 27699764
DOI: 10.1111/ajo.12526 -
Twin Research and Human Genetics : the... Dec 2016The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that...
The Brazilian Twin Registry (BTR) was established in 2013 and has impelled twin research in South America. The main aim of the initiative was to create a resource that would be accessible to the Brazilian scientific community as well as international researchers interested in the investigation of the contribution of genetic and environmental factors in the development of common diseases, phenotypes, and human behavior traits. The BTR is a joint effort between academic and governmental institutions from Brazil and Australia. The collaboration includes the Federal University of Minas Gerais (UFMG) in Brazil, the University of Sydney and University of Melbourne in Australia, the Australian Twin Registry, as well as the research foundations CNPq and CAPES in Brazil. The BTR is a member of the International Network of Twin Registries. Recruitment strategies used to register twins have been through participation in a longitudinal study investigating genetic and environmental factors for low back pain occurrence, and from a variety of sources including media campaigns and social networking. Currently, 291 twins are registered in the BTR, with data on demographics, zygosity, anthropometrics, and health history having been collected from 151 twins using a standardized self-reported questionnaire. Future BTR plans include the registration of thousands of Brazilian twins identified from different sources and collaborate nationally and internationally with other research groups interested on twin studies.
Topics: Adult; Australia; Brazil; Diseases in Twins; Female; Humans; Longitudinal Studies; Male; Registries; Surveys and Questionnaires; Twins, Dizygotic; Twins, Monozygotic
PubMed: 27852353
DOI: 10.1017/thg.2016.83 -
European Spine Journal : Official... Apr 2024Previous studies have suggested that genetic factors are important in the development of degenerative disk disease (DDD). However, the concordance rates for the...
PURPOSE
Previous studies have suggested that genetic factors are important in the development of degenerative disk disease (DDD). However, the concordance rates for the phenotypes requiring surgery are unknown. The purpose of this study was to determine the concordance rates for DDD requiring surgery by studying monozygotic (MZ) and dizygotic (DZ) twin pairs.
METHODS
Patients, aged between 18 and 85 years, operated for DDD between 1996 and 2022 were identified in the national Swedish spine register (Swespine) and matched with the Swedish twin registry (STR) to identify MZ and DZ twins. Pairwise and probandwise concordance rates were calculated.
RESULTS
We identified 11,207 patients, 53% women, operated for DDD. By matching the Swespine patients with the STR, we identified 121 twin pairs (37 MZ and 84 DZ) where one or both twins were surgically treated for DDD. The total twin incidence for operated DDD was 1.1%. For DDD requiring surgery, we found no concordant MZ pair and no concordant DZ pair where both twins were operated for DDD. When we evaluated pairs where at least one twin was operated for DDD, we found two concordant MZ pairs (the co-twins were operated for spinal stenosis) and two concordant DZ pairs (one co-twin operated for spinal stenosis and one (co-twin operated for disk herniation).
CONCLUSIONS
Our findings suggest that genetic factors are probably not a major etiologic component in most cases of DDD requiring surgery. The findings of this study can be used for counseling patients about the risk for requiring DDD surgery.
Topics: Adult; Aged; Aged, 80 and over; Female; Humans; Male; Middle Aged; Young Adult; Diseases in Twins; Incidence; Spinal Stenosis; Twins, Dizygotic; Twins, Monozygotic
PubMed: 38416191
DOI: 10.1007/s00586-024-08161-5 -
Twin Research and Human Genetics : the... Apr 2020In the course of twin studies whose main focus was elucidation of genetic and environmental factors on behavioral traits, many twin researchers became aware of the...
In the course of twin studies whose main focus was elucidation of genetic and environmental factors on behavioral traits, many twin researchers became aware of the strong tendency for dizygotic (DZ) twinning to run in families. Over four decades, Nick Martin and others initiated hormone and ultrasound studies, performed segregation and pedigree analyses, tested candidate genes, carried out linkage projects in sister pairs and formed large collaborations to illuminate the genetics of DZ twinning by genome-wide association studies and meta-analysis. This article summarizes the early work on hormone and genetic studies and describes the meta-analyses that have at last met with success in finding the first genes that predispose to DZ twinning, which also appear to influence many other female reproductive traits.
Topics: Genome-Wide Association Study; Genotype; History, 20th Century; History, 21st Century; Humans; Pedigree; Twin Studies as Topic; Twinning, Dizygotic; Twins, Dizygotic; Twins, Monozygotic
PubMed: 32383427
DOI: 10.1017/thg.2020.15 -
Journal of Developmental Origins of... Feb 2021Major obstetrics and gynecology societies offer inconsistent recommendation regarding optimal delivery timing in uncomplicated dizygotic twins. We sought to investigate...
Major obstetrics and gynecology societies offer inconsistent recommendation regarding optimal delivery timing in uncomplicated dizygotic twins. We sought to investigate the impact of delivery timing within term gestation, in dizygotic twins, on the short- and long-term offspring morbidity. A prospectively analyzed cohort of dizygotic twin deliveries was conducted. All women delivered at a regional tertiary medical center, at term (≥37 0/7), between the years 1991 and 2014, were included. The primary exposure was delivery at 37 0/7-37 + 6/7 weeks, while delivery at ≥38 0/7 weeks' gestation was considered the reference. Neonatal short- and long-term outcomes according to hospitalizations of offspring up to 18 years of age due to cardiac, respiratory, hematological, neurological, and infectious morbidity were compared. Kaplan-Meier survival curves were used to compare cumulative incidences per each major-system hospitalization. Cox regression models were used to estimate the adjusted hazard ratios, while adjusting for variables with clinical importance. During the study period, 612 dizygotic twin deliveries met the inclusion criteria. Of them, 200 (31.3%) occurred at 37-37 6/7 weeks, and 412 (68.7%) occurred at ≥38 0/7 weeks' gestation. In the long-term analysis, rates of hospitalizations involving several major morbidity categories exhibited comparable rates in both groups. The Cox regression models did not demonstrate an independent association between gestational age within term and later major pediatric morbidity in offspring (total long-term morbidity: adjusted hazard ratio 1.33, 95% confidence interval 0.77-2.29). Dizygotic twin deliveries occurring at different gestational ages within term do not appear to significantly impact on major short- and long-term outcomes.
Topics: Adolescent; Adult; Child; Child, Preschool; Delivery, Obstetric; Female; Gestational Age; Hospitalization; Humans; Infant; Infant, Newborn; Male; Morbidity; Pregnancy; Pregnancy, Twin; Prospective Studies; Retrospective Studies; Time Factors; Twins, Dizygotic; Young Adult
PubMed: 32127072
DOI: 10.1017/S2040174420000100 -
Nutrients Sep 2022The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean...
The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean Genome and Epidemiology Study (KoGES) from 2005 through 2014 were analyzed. Participants ≥ 20 years old were enrolled. The 1006 monozygotic twins and 238 dizygotic twins were analyzed for differences in self-reported nutritional intake, total body fat, and body mass index (BMI) using a linear regression model. The estimated values (EV) with 95% confidence intervals (95% CI) of the difference in dietary intake, total body fat, and BMI score were calculated. The monozygotic twin group and the dizygotic twin group showed similar differences in nutritional intake, DEXA fat, and BMI (all p > 0.05). The differences in nutritional intake of total calories and carbohydrates were lower in the monozygotic twin group than in the dizygotic twin group (all p < 0.05). The differences in total body fat were lower in monozygotic twins than in dizygotic twins (adjusted EV = 2427.86 g, 95% CI = 1777.19−3078.53 and adjusted EV = 1.90%, 95% CI = 1.33−2.46). Monozygotic twins had more similar dietary habits for total calories and carbohydrate intake. Other nutritional factors did not show differential similarity between monozygotic and dizygotic twins. Total body fat was more concordant in monozygotic twins.
Topics: Adipose Tissue; Adult; Body Mass Index; Eating; Humans; Twins, Dizygotic; Twins, Monozygotic; Young Adult
PubMed: 36079910
DOI: 10.3390/nu14173655 -
Journal of Oral Rehabilitation Sep 2020Sleep bruxism (SB) and awake bruxism (AB) have been considered different entities, although co-occurrence between them has been shown. While genetic factors have a...
BACKGROUND
Sleep bruxism (SB) and awake bruxism (AB) have been considered different entities, although co-occurrence between them has been shown. While genetic factors have a marked influence on phenotypic variance in liability to SB, this remains unclear for AB.
AIM
To examine the degree of co-occurrence of SB and AB, and whether they have common correlates and also twin similarity of SB and AB bruxism traits by zygosity and sex.
METHODS
A questionnaire was mailed to all twins born 1945-1957 in Finland in 2012 (n = 11 766). Age and sex adjusted logistic regression models were used. Twin similarity was assessed using polychoric correlations, and crosstwin-crosstrait correlations were computed.
RESULTS
The response rate was 72% (n = 8410). Any SB was reported by 14.8% and ≥ 3 nights weekly by 5.0%. Percentages for any AB were 18.4% and 6.3%, respectively. There was substantial co-occurrence (29.5%) between SB and AB, and several shared correlates were found. For SB, the polychoric intra-class correlation was 0.366 in monozygotic (MZ) and 0.200 in dizygotic (DZ) pairs, without gender difference. A twofold crosstwin-crosstrait correlation was observed in MZ twins compared to DZ twins.
CONCLUSIONS
The risk factor profiles of SB and AB were largely but not entirely similar. The higher correlation in MZ than in DZ pairs suggests the influence of genetic factors on both SB and AB. The higher crosstwin-crosstrait correlation in MZ than in DZ pairs suggests some degree of genetic influences shared by SB and AB.
Topics: Finland; Humans; Self Report; Twins, Dizygotic; Twins, Monozygotic; Wakefulness
PubMed: 32613647
DOI: 10.1111/joor.13042 -
Genes, Brain, and Behavior Feb 2022Visual search guides goal-directed action in humans and many other species, and it has been studied extensively in the past. Yet, no study has investigated the relative...
Visual search guides goal-directed action in humans and many other species, and it has been studied extensively in the past. Yet, no study has investigated the relative contributions of genes and environments to individual differences in visual search performance, or to which extent etiologies are shared with broader cognitive phenotypes. To address this gap, we studied visual search and general intelligence in 156 monozygotic (MZ) and 158 same-sex dizygotic (DZ) twin pairs. We found that different indexes of visual search performance (response latency and visual search efficiency) were moderately heritable. Phenotypic correlations between visual search and intelligence were small-to-moderate, and only a small proportion of the genetic variance in visual search was shared with genetic variance in intelligence. We discuss these findings in the context of the "generalist genes hypothesis" stating that different cognitive functions have a common genetic basis.
Topics: Humans; Intelligence; Phenotype; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35044053
DOI: 10.1111/gbb.12779