The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform
Nancy L Segal - One of the best experts on this subject based on the ideXlab platform.
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Twin data the lives that drive the findings Twin research reviews Twin Concordance for kleine levin syndrome Twin study of political discussion Twin relationship quality and urinary cortisol level Twin research guide in the news Twins same day delive
Twin Research and Human Genetics, 2020Co-Authors: Nancy L SegalAbstract:Twin data and the results generated by research are driven by the behavioral and physical attributes of Twin participants. However, many investigators working with Twin data have limited personal contact with actual Twin-pairs. This situation may be limiting with respect to interpretation of results and formulation of new hypotheses. In an attempt to rectify this issue, key aspects of the interconnected lives of co-Twins in three monozygotic male Twin-pairs are presented. The section that follows includes a review of Twin research on Kleine-Levin syndrome, political discussion, Twin relationship quality and urinary cortisol level, and guidelines for determining sample sizes. The final part of this report presents Twin-related news items relating to Twins' same day deliveries, death of a Twin Holocaust survivor, the Vindman Twins, a Twin festival in France and the tiniest Twins on record.
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co Twin control studies natural events experimental interventions and rare happenings Twin research cancer risk in overweight Twins prognosis after fetal loss of one Twin Twin Concordance for parkinson s disease neuroanatomy of musically discordant m
Twin Research and Human Genetics, 2019Co-Authors: Nancy L SegalAbstract:: Co-Twin control is a well-known methodological Twin research design, but its variations and complexities are less well known. Various issues and illustrations are presented with reference to studies involving natural events, experimental interventions and rare happenings that underlie monozygotic (MZ) Twins' environmental differences. This discussion is followed by summaries of recent Twin research pertaining to cancer risk in overweight Twins, the physical risk to surviving Twins after fetal loss of a co-Twin, a 20-year update of Twin Concordance for Parkinson's disease, and neuroanatomical differences in musically discordant MZ Twin pairs. Several Twin-related items that have attracted attention in the news are also summarized.
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situs inversus totalis in Twins a brief review and a life history Twin research Twin studies of trisomy 21 monozygotic Twin Concordance for bilateral coronoid hyperplasia prenatal hormonal effects in mixed sex non human primate litters insurance mand
Twin Research and Human Genetics, 2017Co-Authors: Nancy L SegalAbstract:The presence of situs inversus totalis (full reversal of internal organs) in Twins is briefly reviewed. Information gathered from 35-year-old monozygotic (MZ) female Twin pair discordant for this condition is presented. This is followed by summaries of research on the frequency of trisomy 21 (Down syndrome) in Twins, the first case of MZ Twin Concordance for bilateral coronoid hyperplasia, prenatal hormonal effects in mixed-sex non-human primate litters, and links between insurance mandates and Twinning following in vitro fertilization. The final section of this article describes Twin-related events reported in the news, namely, the first recorded birth of identical Twin puppies; the 100th birthday celebration of a pair of fraternal female Twins, the passing of an award-winning identical Twin production designer, and the first running of the New York City Marathon by a set of quadruplets.
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suicidal behaviors in surviving monozygotic and dizygotic co Twins is the nature of the co Twin s cause of death a factor
Suicide and Life Threatening Behavior, 2009Co-Authors: Nancy L SegalAbstract:Genetically informative samples can address hereditary and experiential influences on suicide-related behaviors. The frequency of suicide-related behaviors was compared in Twins from two survivor groups: (1) those whose co-Twins' deaths were suicides (monozygotic [MZ]: n = 47; dizygotic [DZ]: n = 31), and (2) those whose co-Twins' deaths were nonsuicides (MZ: n = 347; DZ: n = 170). The frequency of suicide attempts among suicide survivors was significantly higher in MZ than DZ Twins, while the frequency of suicide attempts among nonsuicide Twin survivors did not differ between MZ and DZ Twins. Twin Concordance for suicide attempts more likely reflects a genetic predisposition than a behavioral reaction to the loss.
Thomas M Mack - One of the best experts on this subject based on the ideXlab platform.
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differential Twin Concordance for multiple sclerosis by latitude of birthplace
Annals of Neurology, 2006Co-Authors: Talat Islam, James W Gauderman, Wendy Cozen, Ann S Hamilton, Margaret Burnett, Thomas M MackAbstract:Objective: To address the inconsistency in the reported Concordance of multiple sclerosis (MS) among Twins by zygosity, sex, and latitude. Methods: Four hundred eighteen medically documented monozygotic (MZ) and 380 same-sex dizygotic (DZ) pairs were ascertained from 1980 to 1992 and followed. The study population was representative of Twins with multiple sclerosis. Twins from Canada and adjacent US states (at or above 41– 42° N) were considered “northern,” and ancestry was dichotomized from descent from high-risk populations. Diagnosis before median age 29.3 years was considered “early.” Results: The MZ/DZ Concordance ratio was 2.9 (95% confidence interval [CI], 1.0 – 8.9) among men and 2.6 (95% CI, 1.5– 4.5) among women. The average age at northern diagnosis was independent of ancestry and 2 years earlier for both MZ (p 0.02) and DZ (p 0.01) patients. Among DZ Twins, Concordance was independent of all characteristics. Among MZ Twins, Concordance was 1.9 times (95% CI, 1.2–3.2) greater among northern Twins, 1.9 (95% CI, 1.1–3.6) times greater among Twins with high-risk ancestry, and 2.1 (95% CI, 1.2–3.6) times greater if diagnosis was early. Ancestry and early diagnosis made independent significant contributions to the differential Concordance by latitude. Interpretation: Multiple sclerosis is similarly heritable by sex, and the apparent variation in MZ Concordance by latitude is influenced by environmental and genetic factors. Ann Neurol 2006;60:56 – 64 The incidence and prevalence of multiple sclerosis (MS) increases with distance from the equator in both the northern 1 and southern 2 hemispheres. Migrant
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a revised estimate of Twin Concordance in systemic lupus erythematosus
Arthritis & Rheumatism, 1992Co-Authors: Dennis Deapen, Agustin Escalante, Lisa Weinrib, David A Horwitz, Barbara Bachman, Pradip Royburman, Ann Walker, Thomas M MackAbstract:Objective. Based on a small clinical series and previously published case reports, Concordance for systemic lupus erythematosus (SLE) among monozygous (MZ) Twins has been reported to be as high as 69%. Using a larger and less biased sample, we provide another estimate of this percentage. Methods. We established a registry of Twins with SLE, based upon self-reports and information provided by the patients' physicians. We used DNA fingerprinting to validate the reported zygosity in a sample of these Twins. Results. Of 107 Twin pairs meeting the American College of Rheumatology 1982 revised criteria for the diagnosis of SLE, 24% of 45 MZ pairs and 2% of 62 dizygous (DZ) pairs were concordant. The frequency distributions of diagnostic criteria and disease symptoms in the SLE patients were similar to those in other published reports of SLE patients. Zygosity was confirmed by DNA fingerprinting in a subsample of 15 self-described MZ Twins and 7 self-described DZ Twins. AH individuals had correctly predicted their zygosity. Conclusion. MZ Concordance for SLE is similar to that for other autoimmune diseases and is much lower than previously believed.
Jacob V B Hjelmborg - One of the best experts on this subject based on the ideXlab platform.
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the nordic Twin study on cancer norTwincan
Twin Research and Human Genetics, 2019Co-Authors: Jennifer R Harris, Hans-olov Adami, Jacob V B Hjelmborg, Kamila Czene, Lorelei A Mucci, Jaakko KaprioAbstract:Nordic Twin studies have played a critical role in understanding cancer etiology and elucidating the nature of familial effects on site-specific cancers. The NorTwinCan consortium is a collaborative effort that capitalizes on unique research advantages made possible through the Nordic system of registries. It was constructed by linking the population-based Twin registries of Denmark, Finland, Norway and Sweden to their country-specific national cancer and cause-of-death registries. These linkages enable the Twins to be followed many decades for cancer incidence and mortality. To date, two major linkages have been conducted: NorTwinCan I in 2011–2012 and NorTwinCan II in 2018. Overall, there are 315,413 eligible Twins, 57,236 incident cancer cases and 58 years of follow-up, on average. In the initial phases of our work, NorTwinCan established the world’s most comprehensive Twin database for studying cancer, developed novel analytical approaches tailored to address specific research considerations within the context of the Nordic data and leveraged these models and data in research publications that provide the most accurate estimates of heritability and familial risk of cancers reported in the literature to date. Our findings indicate an excess familial risk for nearly all cancers and demonstrate that the incidence of cancer among Twins mirrors the rate in the general population. They also revealed that Twin Concordance for cancer most often manifests across, rather than within, cancer sites, and we are currently focusing on the analysis of these cross-cancer associations.
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estimating Twin Concordance for bivariate competing risks Twin data
Statistics in Medicine, 2014Co-Authors: Thomas H Scheike, Klaus K Holst, Jacob V B HjelmborgAbstract:For Twin time-to-event data, we consider different Concordance probabilities, such as the casewise Concordance that are routinely computed as a measure of the lifetime dependence/correlation for specific diseases. The Concordance probability here is the probability that both Twins have experienced the event of interest. Under the assumption that both Twins are censored at the same time, we show how to estimate this probability in the presence of right censoring, and as a consequence, we can then estimate the casewise Twin Concordance. In addition, we can model the magnitude of within pair dependence over time, and covariates may be further influential on the marginal risk and dependence structure. We establish the estimators large sample properties and suggest various tests, for example, for inferring familial influence. The method is demonstrated and motivated by specific Twin data on cancer events with the competing risk death. We thus aim to quantify the degree of dependence through the casewise Concordance function and show a significant genetic component.
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genetic analysis of rare disorders bayesian estimation of Twin Concordance rates
Behavior Genetics, 2012Co-Authors: Stephanie Martine Van Den Berg, Jacob V B HjelmborgAbstract:Twin Concordance rates provide insight into the possibility of a genetic background for a disease. These Concordance rates are usually estimated within a frequentistic framework. Here we take a Bayesian approach. For rare diseases, estimation methods based on asymptotic theory cannot be applied due to very low cell probabilities. Moreover, a Bayesian approach allows a straightforward incorporation of prior information on disease prevalence coming from non-Twin studies that is often available. An MCMC estimation procedure is tested using simulation and contrasted with frequentistic analyses. The Bayesian method is able to include prior information on both Concordance rates and prevalence rates at the same time and is illustrated using Twin data on cleft lip and rheumatoid arthritis.
Wer Ollier - One of the best experts on this subject based on the ideXlab platform.
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Twin Concordance rates for rheumatoid arthritis results from a nationwide study
Rheumatology, 1993Co-Authors: A J Silman, A J Macgregor, Wendy Thomson, S Holligan, D Carthy, A Farhan, Wer OllierAbstract:We report the Concordance rate for RA in a nationwide study of 91 monozygotic (MZ) and 112 dizygotic (DZ) pairs. Twin pairs were recruited from both a national media campaign and a 2-month prospective inquiry of all UK rheumatologists. Disease status was established following a structured clinical and serological appraisal, together with radiological assessment where necessary. Zygosity was confirmed using DNA fingerprinting. In all, 14 (15.4%) of the MZ and four (3.6%) of the DZ pairs were disease concordant (risk ratio: 4.3 95% CI 1.5 to 12.6). There was no difference in the Concordance between the media and clinical derived Twins. Further the excess MZ Concordance persisted after adjusting for age, age at disease onset, sex and rheumatoid factor status. Analysing the data in relation to the timing of disease onset in the first affected Twin showed that subsequent disease risk in the initially unaffected co-Twins of the MZ affected probands increased with increasing duration of follow-up. We conclude that the overall MZ Concordance at 15% is lower than the 30% figure normally quoted from a study some 30 years ago and sets a ceiling at the potential genetic contribution to disease susceptibility
Matt Mcgue - One of the best experts on this subject based on the ideXlab platform.
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adolescent Twins discordant for major depressive disorder shared familial liability to externalizing and other internalizing disorders
Journal of Child Psychology and Psychiatry, 2003Co-Authors: Stephanie L Burcusa, William G Iacono, Matt McgueAbstract:Background: In adolescents, as in adults, there is often comorbidity between major depressive disorder (MDD) and many other disorders. In this study, the discordant Twin method was used to investigate whether this comorbidity in adolescents may be due to a shared familial liability between MDD and other internalizing disorders, and between MDD and externalizing disorders. Methods: We examined prevalence rates of anxiety disorders, substance use disorders, and childhood externalizing disorders in 624 seventeen-year-old same-sex monozygotic and dizygotic Twin pairs. Overall prevalence of MDD in this sample was 12.9%. Twenty-seven Twin pairs were concordant for MDD, 107 were discordant for MDD, and 490 were concordant for no MDD. Results: Prevalence rates for disorders other than MDD were elevated in the depressed Twins relative to the control Twins from pairs concordant for no MDD. Prevalence rates were also elevated in the nondepressed co-Twins of depressed Twins. Twin Concordance for disorders other than MDD was higher in Twin pairs where at least one Twin was depressed than in pairs where neither Twin was depressed. Conclusions: These results support a shared familial liability between MDD and other internalizing disorders and between MDD and externalizing disorders in adolescents.
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Twin Concordance for attention deficit hyperactivity disorder a comparison of teachers and mothers reports
American Journal of Psychiatry, 1997Co-Authors: Dianne K Sherman, Matt Mcgue, William G IaconoAbstract:Objective: The present study examined probandwise Concordance rates for attention deficit hyperactivity disorder (ADHD) in a community sample of 194 monozygotic and 94 dizygotic male Twins, ages 11‐12 years. Method: DSM-III and DSM-III-R diagnoses of ADHD were based on rating scale reports from the Twins’ teachers and structured interview reports obtained from their mothers. Model-fitting analyses were used to estimate genetic and environmental effects on ADHD. Results: Concordance rates for ADHD were greater for monozygotic than dizygotic Twins according to both mothers’ and teachers’ reports; this finding indicates the importance of genetic factors in the etiology of this syndrome. Fifteen percent of subjects received an ADHD diagnosis by teachers’ ratings, compared with 6% by mothers’ reports. Three percent of subjects met criteria for ADHD in both school and home settings. Teachers’ ratings yielded moderate monozygotic and dizygotic Concordance rates, in contrast to mothers’ reports, which indicated a high monozygotic and a zero dizygotic Concordance for ADHD. A model that included additive genetic and nonshared environmental factors provided the best fit to these ADHD data. Conclusions: ADHD, as defined by DSM criteria, appears to be a genetically influenced disorder whether diagnoses are based on teachers’ or mothers’ reports. However, the extent of this genetic influence seems to vary by informant source. These findings suggest that obtaining diagnostic data from either teachers’ or mothers’ reports alone may provide an incomplete characterization of ADHD. (Am J Psychiatry 1997; 154:532‐535)
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when assessing Twin Concordance use the probandwise not the pairwise rate
Schizophrenia Bulletin, 1992Co-Authors: Matt McgueAbstract:Geneticists and Twin researchers have long debated the relative merits of two alternative measures of Twin Concordance: the pairwise and probandwise Concordance rates. The results of this debate are now quite clear, for almost every application the probandwise rate is preferred over the pairwise rate. In a recent review of schizophrenia Twin studies, however, Torrey (1992) chose to analyze pairwise rather than probandwise rates. Torrey's use of pairwise rates led him to conclude that the monozygotic Twin Concordance for schizophrenia is weaker than what is widely accepted, and that, by implication, the magnitude of the genetic contribution to schizophrenia has been overestimated. In this brief commentary, we review the relative strengths and weaknesses of the pairwise and probandwise rates and show that Torrey's conclusion is based upon his incorrect use of pairwise rates. Twin studies of schizophrenia continue to support the existence of a strong genetic influence on the development of schizophrenia.
