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Craniosynostosis involves the early closure of one or more joints connecting the bones of an infant's skull. A case of young monozygotic (MZ) male twins with an unidentified variant of this condition is described, followed by a summary of relevant published reports. This overview is followed by descriptions of a kangaroo care program for premature twins, developmental delay in an MZ twin pair, osteosarcoma in one MZ twin and controversial issues in the management of multiple pregnancies. Media reports of twin and triplet Olympic athletes, a twin's rescue from a crocodile, the birth of twin pandas in Japan, a case of twin surrogacy and the birth of identical triplets are also presented. [ABSTRACT FROM AUTHOR]

Using vital statistics in Japan (1995-2008), 154,578 live-born twin pairs (128,236 monozygotic [MZ] and 180,920 dizygotic [DZ]) were identified. The proportion of severe discordance among live-born twin births was twice as high in Japanese than Caucasian infants. There were 1858 MZ and 1620 DZ infant deaths. Computation of the relationship between infant mortality rate and birth weight discordance among the twins was performed. Discordance levels were classified into seven groups: <5%, five groups from 5-9% to 25-29%, and ≥30%.The mortality rate was significantly higher in MZ than DZ twins for discordances except at 5-9% and 10-14%. The lowest rate for MZ twins was at 5-9% (7.5 per 1000 live twins) and significantly increased from 10-14% (9.4) to ≥30% (83.4), while the lowest rate for DZ twins was at <5% (6.7), which significantly increased at 10-14% (8.0) and from 25-29% (12.1) to ≥30% (35.5). The relationship was also computed in two gestational age groups (<28 and ≥28 weeks). For births at <28 weeks, three discordances (after 20-24%) in MZ twins were associated with adverse mortality rate. For births at ≥28 weeks, the same relationship was obtained after 10-14% in MZ and after 20-24% in DZ twins. The relationship from 2002 to 2008 showed that the mortality rates significantly increased after 10-14% for both types of twins. In conclusion, five discordance levels in MZ and three levels in DZ twins were associated with adverse mortality rates. [ABSTRACT FROM AUTHOR]

The study focused on the extent to which the general factor of intelligence g and heritability coefficients of the subtests of an IQ battery correlate. Modest to strong positive correlations were found in five studies from Western countries and six studies from a Japanese meta-analysis. The results for Russian twins were compared with those of the Western and Japanese studies. Data from 402 twins aged 13 and 296 twins aged 16 showed correlations of r=−0.45 and r=−0.60, respectively. It is concluded that the two data points are clearly not in line with established findings. It may be that the link between g loadings and heritabilities is more complex than previously thought. [ABSTRACT FROM PUBLISHER]

The 4th International Network of Twin Registries (INTR) Consortium Meeting took place in Osaka, Japan, September 28–29, 2015. The venue was the Osaka Medical Center for Medical Innovation and Translational Research. An overview of presentations and other activities is provided. Next, 1930s research on familial fraternal twinning, preference for masculine faces, physical aggression and epigenetics, and a prenatal education program for parents of multiples are described. Current twin-related events include the 2016 Guinness Book of World Records (GWR), the oldest living male twins, newly reunited twins, the birth of panda twins and a controversial twin-based website. [ABSTRACT FROM PUBLISHER]

Background: The occurrence of multiple births has been recognized as a risk factor for child maltreatment. However, few population-based studies have examined the relationship between multiple births and child maltreatment. This study aimed to evaluate the degree of risk of child maltreatment among singletons and multiple births in Japan and to identify factors associated with increased risk.Methods: Using population-based data, we analyzed the database of records on child maltreatment and medical checkups for infants aged 1.5 years filed at Nishinomiya City Public Health Center between April 2007 and March 2011. To protect personal information, the data were transferred to anonymized electronic files for analysis.Results: After adjusting by logistic regression for each associated factor and gestation number, multiples themselves were not associated with the risk of child maltreatment. However, compared with singletons, multiples had a significantly higher rate of risk factors for child maltreatment, including low birth weight and neural abnormality. Moreover, compared with mothers of singleton, mothers of twins had a significantly higher rate of poor health, which is a risk factor of child maltreatment.Conclusion: Multiples were not associated with the risk of child maltreatment. However, compared with singletons, multiples and their mothers had a significantly higher rate of risk factors of child maltreatment. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to clarify the characteristics of fatal child maltreatment in families with multiple births in Japan. An exhaustive information search was performed to find multiple-birth cases between July 2003 and March 2011. There were 437 cases of fatal maltreatment of children aged 0–17 years during this period, including 14 involving multiple-birth children. A keyword search was performed to create a full profile for each multiple-birth case. The 14 multiple-birth victims were twins from 13 families. No significant difference between twins and singletons with fatal maltreatment was observed for most characteristics. However, in the case of twins, 0-month victims were rare, and the number of children per family was larger. One twin died from shaken baby syndrome. The victim's siblings were also maltreated in six out of 12 relevant cases, including all six co-twins. Premature birth, having a disabled co-twin, delay of growth or development, and parental disfavor tended to be factors of maltreatment when only one twin was maltreated. Four families were given suspended sentences in total, including three mothers who acted as solitary murderers (43% = 3/7). In conclusion, recent Japanese nationwide data suggests that the non-specific overburden of child rearing might be one possible reason for higher frequency of child maltreatment for multiples compared with singletons, and parental comparisons between two twins might be another. The penal sentences for fatal child maltreatment might be more lenient for perpetrators of this crime against twins than against singletons. [ABSTRACT FROM PUBLISHER]

The infant mortality rate (IMR) among single and twin births from 1999 to 2008 was analyzed using Japanese Vital Statistics. The IMR was 5.3-fold higher in twins than in singletons in 1999 and decreased to 3.9-fold in 2008. The reduced risk of infant mortality in twins relative to singletons may be related, partially, to survival rates, which improved after fetoscopic laser photocoagulation for twin — twin transfusion syndrome. The proportion of neonatal deaths among total infant deaths was 54% for singletons and 74% for twins. Thus, intensive care of single and twin births may be very important during the first month of life to reduce the IMR. The IMR decreased as gestational age (GA) rose in singletons, whereas the IMR in twins decreased as GA rose until 37 weeks and increased thereafter. The IMR was significantly higher in twins than in singletons from the shortest GA (<24 weeks) to 28 weeks as well as ≥38 weeks, whereas the IMR was significantly higher in singletons than in twins from 30 to 36 weeks. As for maternal age, the early neonatal and neonatal mortality rates as well as the IMR in singletons were significantly higher in the youngest maternal age group than in the oldest one, whereas the opposite result was obtained in twins. The lowest IMR in singletons was 1.1 per 1,000 live births for ≥38 weeks of gestation and heaviest birth weight (≥2,000 g), while the lowest IMR in twins was 1.8 at 37 weeks and ≥2,000 g. [ABSTRACT FROM AUTHOR]

Osaka University Center for Twin Research is currently organizing a government-funded, multidisciplinary research project using a large registry of aged twins living in Japan. The purpose of the project is to collect various information as well as biological resources from registered twins, and to establish a biobank and databases for preserving and managing these data and resources. The Center is collecting data from twin pairs, both of whom have agreed to participate in a one-day comprehensive medical examination. The following data are being collected: physical data (e.g., height, body mass, blood pressure, theoretical visceral fat, pulse wave velocity, and bone density), data regarding epidemiology (e.g., medical history, lifestyle, quality of life, mood status, cognitive function, and nutrition), electrocardiogram, ultrasonography (carotid artery and thyroid), dentistry, plastic surgery, positron emission tomography, magnetoencephalogram, and magnetic resonance imaging of brain. These data are then aggregated and systematically stored in specific databases. In addition, peripheral blood is obtained from the participants, and then genomic DNA is purified and sera are stored. A wide variety of studies are ongoing, and more are in the planning stage. [ABSTRACT FROM AUTHOR]

The West Japan Twins and Higher Order Multiple Births Registry was established in the 1990s by recruiting young twins and multiples and through referrals from public health centers. To date, over 7,000 twins and 4,300 higher order multiple births and their families have been registered in the survey, and it includes one of the largest triplet samples in the world. Follow-up questionnaires are also mailed every 2 to 3 years as part of longitudinal survey studies. This article describes the goals of the registry, the recruitment of multiples, and the overall focus of the study. The goals of the registry are not only to provide data for research on human genetics and maternal and child health, but also to provide appropriate information for families with multiples. [ABSTRACT FROM AUTHOR]

Sex differences in mental rotation ability have been observed in many countries. A previous study of Finnish participants reported that genetic and environmental influences on mental rotation ability differ between sexes. In this study, we assessed genetic and environmental influences on variance in mental rotation ability in 649 Japanese twins using a mental rotation test. To explain the influence of sex on variance in mental rotation ability, we applied genetic analysis using the sex limitation model. The following two factors explained variance in mental rotation ability: (1) the additive genetic factor, which reflects the accumulated small influence of many genes, and (2) the unique environmental factor, which is a type of environmental factor that differs between co-twins. The shared environmental factor, a type of environmental factor common for co-twins, could not explain the variance in mental rotation ability. Furthermore, the additive genetic factor was the same between sexes (i.e., not qualitative sex differences for the additive genetic factor), indicating that the same genes affect mental rotation ability in both sexes. Despite this observation, the additive genetic influence was greater in males than in females. In contrast, the unique environmental influence was not different between sexes. Considering the current results and those of a previous study, the quantitative sex difference for the additive genetic influences in mental rotation ability may be universal, while the unique environmental differences may depend on the characteristics of specific populations. [ABSTRACT FROM AUTHOR]

The purpose of this study was to estimate the number of siblings in each Japanese family with multiple birth children using two sets of census data, from 1990 and 1995. The mean number of siblings for singletons was 2.3 in 1990 (2.4 in 1995), 2.9 (2.9) for one set of twins, 4.6 (4.5) for two sets of twins, and 3.5 (3.3) for one set of triplets. For birth order of multiples, the highest mean sibling number was 4.4 for one set of twins (the middle), 7.5 for two sets of twins (the middle-middle), and 4.3 for one set of triplets (the last). The mean sibling number was slightly higher for like-sexed twins and triplets than in unlike-sexed twins and triplets. The mean sibling number was highest in the Okinawa District, among nine districts (0.4 for singletons, 0.6 for one set of twins, 1.0 for two sets of twins and 0.6 for triplets). The current study of the number of siblings in each family with multiple birth children will help provide data for designing programs to help support multiple-birth families. The method of using census data on multiple births might result in a system to analyze nationwide data on multiple birth children if there is no national registry of multiple births after live births in any country. [ABSTRACT FROM AUTHOR]

Our aims were to assess the incidence of birthweight discordance of twins, to explore risk factors and its impact on perinatal mortality, and to quantify the risks at different severity of birthweight discordance in Japan, by using a nationwide obstetric database. There were 10,828 pairs of twins, born from 2001 to 2005 recorded in the database of the national Perinatal Health Care Project, fully enrolled. The overall incidence of birthweight discordance was 47.34%. The incidence of mild, severe and extremely severe discordance was 19.26%, 10.21% and 17.87%, respectively. The incidence of birthweight discordance in Japan is much higher than that in other countries, particularly at higher severity level. By linear regression model, our study added independent factors of primiparity (p < .001), sex composition (p < .001), chorionicity (p < .001), gestational age (p < .001), and delivery mode (p < .001) in determining birthweight discordance percentage. Maternal age and application of assisted reproduction technologies (ART) didn't significantly influence the birthweight discordance. The birthweight discordance is closely associated with gestational age and affected discharge mortality. From 25% of birthweight discordance, risk to discharge mortality tended to significantly increase, suggesting it should be added as a reference for clinical practices. [ABSTRACT FROM AUTHOR]

In three studies, a General Factor of Personality (GFP) was found to occupy the apex of the hierarchical structure. In Study 1, a GFP emerged independent of method variance and accounted for 54% of the reliable variance in a multitrait-multimethod assessment of 391 Italian high school students that used self-, teacher-, and parent-ratings on the Big Five Questionnaire - Children. In Study 2, a GFP was found in the seven dimensions of Cloninger's Temperament and Character Inventory as well as the Big Five of the NEO PI-R, with the GFPtci correlating r = .72 with the GFPneo. These results indicate that the GFP is practically the same in both test batteries, and its existence does not depend on being extracted using the Big Five model. The GFP accounted for 22% of the total variance in these trait measures, which were assessed in 651 pairs of 14- to 30-year-old Japanese twins. In Study 3, a GFP accounted for 32% of the total variance in nine scales derived from the NEO PI-R, the Humor Styles Questionnaire, and the Trait Emotional Intelligence Questionnaire assessed in 386 pairs of 18- to 74-year-old Canadian and U.S. twins. The GFP was found to be 50% heritable with high scores indicating openness, conscientiousness, sociability, agreeableness, emotional stability, good humor and emotional intelligence. The possible evolutionary origins of the GFP are discussed. [ABSTRACT FROM AUTHOR]

Frequencies of recurrent multiple maternities were estimated using two sets of census data in Japan in 1990 and 1995. The repeat frequency (RF) of the twinning rate is the frequency of 2 sets of twins among families or couples who have already had 1 set of twins and 2 more siblings. The overall RFs were 9.6 per 1000 couples in 1990 and 9.3 in 1995. The RFs of the monozygotic (MZ) twinning rates were 5.9 per 1000 couples in 1990 and 5.5 in 1995. The RFs of the dizygotic (DZ) twinning rates were 3.7 in 1990 and 3.8 in 1995. For unlike-sexed propositus twins, the RF of MZ twins were 5.0 per 1000 couples in 1990 and 5.5 in 1995. The RF of DZ twins were 5.3 in 1990 and 4.6 in 1995. As for like-sexed propositus twins, the corresponding RFs were 6.2 and 5.5 for MZ twins, and 3.4 and 3.6 for DZ twins, respectively. In mothers who have experienced a twin maternity, the overall RF of twinning was 1.5 to 2 times as high as the average mother's chance of having twins. There was no RF for triplets for both census years. As for geographic variations of the overall RF, the rates in Okinawa (16.2) and Hokkaido (15.3) were significantly higher than those in the Tohoku (8.7), Kanto (8.0) and Kyushu (7.4) districts. [ABSTRACT FROM AUTHOR]

This study was performed using population-based data to analyze whether motor development in early life is different between singletons and twins in Japan. For better comparison and investigation, we divided the 2 groups into a group with a birthweight of 2.5 kg or greater (subgroup A) and a group with a birthweight of less than 2.5 kg (subgroup B), respectively. We analyzed the database of medical check-ups for children aged 3 years between April 2001 and July 2004. They received medical checkups at 4 months, 1.5, and 3 years of age. Children who were suspected of having neurological abnormality or disability were referred to specialists and excluded from the database. The data of 14,132 children were analyzed. Among these, 13,040 (92.3%) children were singletons in subgroup A, 75 (0.5%) were twins in subgroup A, 866 (6.1%) were singletons in subgroup B and 151 (1.1%) were twins in subgroup B. The mean age at achieving milestones was slower in twins of subgroup A for each developmental outcome than singletons of subgroup A, and the difference between twins and singletons was significant after adjustment for rolling over. On the contrary, after adjusting for a confounding factor (gestational age), singletons of subgroup B attained motor development facilitating walking independently slower than twins of subgroup B. There were different tendencies in the results regarding the motor development of subjects of subgroup A and that of subjects of subgroup B. [ABSTRACT FROM AUTHOR]

Since established in 1998, the Keio Twin Project (KTP) has been dedicated to investigating genetic and environmental sources contributing to human psychological traits in adolescence and young adulthood. A population-based twin registry was constructed by the KTP through the use of official residential records in the Tokyo area, and to date requests to participate in our research have generated 1040 pairs of twins and triplets of age 14 to 30, forming one of the largest twin registries in Asia. Our comprehensive datasets, obtained through questionnaires, performance tests, and physical measurements, cover a wide range of human traits: personality, psychiatry, mental health, sociality, cognition, and physical index. Demographic variables and environment of upbringing are also sought by twins and by some parents. This extensive information allows us to clarify the genetic and environmental overlap across multiple traits as well as specificities unique to single traits. Adding an evolutionary psychology perspective to the behavior genetics framework is currently being attempted in order to develop a grand theory of human genetics. [ABSTRACT FROM AUTHOR]

The Tokyo Twin Cohort Project (ToTCoP) is a large-scale longitudinal study of 5 years based on 1619 pairs of infant twins reared together. The purpose of the study is to construct a population-based twin registry in Japan and to investigate human growth and development and twin themselves. It covers behavioral, neurological, physical and environmental variables measured by questionnaire, home visiting and brain imaging technology. The full registry contains over 47,000 multiple births collected from the Basic Resident Register, and the targeted population is 3070 probable twins of 0 to 2 years old. Preliminary analysis of the entry questionnaire data showed no serious sampling biases. Descriptive statistics of parental characteristics (parental age, gestation age, parity and placentation, maternal weight, parenting stress) and children's characteristics (body size at birth, 4 and 10 months of age, milk consumption, and sleeping and social behavior) and their correlations, genetic and environmental contributions and correlations are reported. [ABSTRACT FROM AUTHOR]

This article profiles the historical twin databases of the secondary education school attached to the Faculty of Education at the University of Tokyo. The school was established in 1948. Every year, about 50 pairs of twins of all sex and zygosity combinations and aged 11 to 12 years take an examination, and about 10 to 20 pairs are admitted based on the results. Three independent datasets exist: one for applicants (11-12 years), one for students (12-18 years), and one for graduates (18-72 years). These three historical databases and research perspectives are introduced herein. [ABSTRACT FROM AUTHOR]

The Osaka University Aged Twin Registry (OUATR) is the largest adult twin registry in Japan. Since its establishment in 1974, the OUATR has conducted a number of studies with particular focus on the environmental contribution to physical-cognitive-mental aging, longevity and aging-dependent diseases in later adulthood. The registry consists of 12,000 pairs of Japanese twins born between 1900 and 1935. Two hundred and fifty pairs of twins have undergone comprehensive medical examination to date. Follow-up questionnaires have been mailed out on a regular basis, for the purpose of checking current vital statuses, health conditions, and so forth. The main objective of this longitudinal twin study is to contribute to the prevention of lifestyle-related diseases and the promotion of successful aging. [ABSTRACT FROM AUTHOR]

More than 100 pairs of adult twins, reared apart and growing old separately, have participated in the Japanese Study of Adult Twins Reared Apart and Growing Old Separately since it began in 1974. The subjects are 161 pairs of adult twins born between 1910 and 1945 in Japan. The main focus of this study is to investigate the influences of environmental factors and life history on life satisfaction and psychological well-being in later adulthood. A mail survey has been conducted on these twins each year since 1974. To date, the Wechsler Adult Intelligent Scale, Maudsley Personality Inventory, Newgarten Life Satisfaction Index, comprehensive medical examinations and personal interviews have been conducted for 12 twin pairs residing in various areas of Japan. [ABSTRACT FROM AUTHOR]