The West Japan Twins and Higher Order Multiple Births Registry

India's Opportunities and Challenges in Establishing a Twin Registry: An Unexplored Human Resource for the World's Second-Most Populous Nation

Nature and nurture have always been a prerogative of evolutionary biologists. The environment's role in shaping an organism's phenotype has always intrigued us. Since the inception of humankind, twinning has existed with an unsettled parley on the contribution of nature (i.e. genetics) versus nurture (i.e. environment), which can influence the phenotypes. The study of twins measures the genetic contribution and that of the environmental influence for a particular trait, acting as a catalyst, fine-tuning the phenotypic trajectories. This is further evident because a number of human diseases show a spectrum of clinical manifestations with the same underlying molecular aberration. As of now, there is no definite way to conclude just from the genomic data the severity of a disease or even to predict who will get affected. This greatly justifies initiating a twin registry for a country as diverse and populated as India. There is an unmet need to set up a nationwide database to carefully curate the information on twins, serving as a valuable biorepository to study their overall susceptibility to disease. Establishing a twin registry is of paramount importance to harness the wealth of human information related to the biomedical, anthropological, cultural, social and economic significance.

The New West Japan Twins and Higher Order Multiple Births Registry

The new West Japan Twins and Higher Order Multiple Births Registry was established by recruiting young twins and multiple births and by referrals from public health centers in the 1990s. The participants included in the survey comprised over 7800 twins and 4241 higher order multiples, and their families. Specifically, the present registry contains one of the largest triplet samples in the world. For these twins and multiples, data on year of delivery, mode of delivery, gestational age, intrapartum complications, longitudinal physical measures, motor milestones, cerebral palsy and feeding methods were obtained from records in the Maternal and Child Health Handbooks and schools. Participating mothers were asked to indicate family structure, parental educational history, maternal sleeping time, maternal health condition, maternal and paternal age at multiple delivery, complications during pregnancy, handedness of multiples and age at menarche of multiples. However, the zygosity differed among the various collaborating public health centers according to factors such as the time of investigation. Follow-up questionnaires have been mailed out every 3-4 years for longitudinal studies. This article describes the goals of this registry, recruitment of multiples and the focus of the study. The goals of this registry are not only to conduct research on human genetics and maternal and child health, but also to contribute to providing appropriate information for families with multiples.

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

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.

Association between physical and motor development in childhood: a longitudinal study of Japanese twins

Length and weight in infancy are associated with neurodevelopment, but less is known about growth in other anthropometric measures. In this study we analyzed how the development in length, weight, head circumference, and chest circumference over infancy is associated with motor development in early childhood, using a twin study design. Information on physical development over infancy and the age at achievement of eight developmental milestones over early childhood was collected for 370 Japanese twin pairs. Linear mixed models were used to analyze how physical development is associated with motor development between individual twins, as well as within twin pairs, adjusting the results for shared maternal and postnatal environmental factors. Delayed motor development was associated with smaller body size over infancy, and we also found some suggestive evidence that it was associated with catch-up growth as well. When studying the associations within twin pairs discordant for motor development, similar associations were found. However, chest circumference showed the most robust association within discordant twin pairs. Smaller body size and rapid catch-up growth are associated with delayed motor development. When studying these associations within twin pairs and thus adjusting the results for gestational age as well as many other maternal and postnatal environmental factors, chest circumference showed the most robust association. Chest circumference, rarely used in developed countries, can offer additional information on prenatal conditions relevant for further motor development not achieved by more traditional anthropometric measures.

Development of body mass index of Japanese triplets from birth until the onset of puberty

We aimed to analyze the characteristics of development of relative weight in Japanese triplets from birth until 12 years of age. Data were collected through a mailed questionnaire sent to mothers of triplets asking for information recorded in medical records. Altogether we had information on 1,061 triplet children of 354 mothers born between 1978 and 2006. For these births, data on triplets' height and weight growth, gestational age, sex, parity, and maternal age at delivery were obtained from records in the maternal and child health handbooks and records from the schools where children receive health check-ups. In addition, information on maternal height and weight was obtained. Triplets have a lower ponderal index at birth and lower body mass index (BMI) compared with the general population until 12 years of age, except for the period during 1 and 3 years of age. Moreover, birth weight had the strongest contribution to BMI of triplets until 6 years of age. After 9 years of age, maternal BMI was a significant factor affecting BMI of triplets.