influence BP and BMI. Third, our samples in this study were collected in north China, where the composition of food and geographical environment are different from those in the southern part of the country. Given the importance of the environmental effect on BP and BMI, similar twin- based studies conducted in south China should help to reveal the interplay between genetics and environment as a result of environmental adaptation for the same ethnic population. Fourth, there is no known causal order among PP, SBP, DBP, and BMI, so we are unable to discriminate the causative orders in our Cholesky decomposition model. In conclusion, our multivariate analyses revealed com- mon genetic and environmental backgrounds for PP, BP, and BMI in Chinese twins. Our results could provide useful information for the discovery of specific genes or environ- mental factors that impact PP, BP, and BMI, especially in northern Han Chinese.
The Chinese population is the world’s largest and most rapidly aging population. The aging Chinese population is potentially creating a growing burden to a society under eco- nomic transition. Studying and promoting healthy aging in the Chinese population may hold the key to improving pub- lic health in China. This is especially important considering that the current findings from Western populations may not apply to the Chinese population, who live in a different social and physical environment. This article reports results from the first twin-based multivariate modeling of cogni- tion, memory, and depression symptomatology as part of a comprehensive investigation of genetic and environmen- tal regulation on aging-related phenotypes in middle-aged and older Chinese twins. Results from different multivari- ate models will be presented, with the aim of testing our hypothesis of a common genetic and environmental back- ground for the three phenotypes. The article ends with dis- cussion on findings from our analysis, together with their implications.
The prevalence of overweight and obesity is growing rapidly in many countries. Socioeconomic inequalities might be important for this increase. The aim of this study was to determine associations of body mass index (BMI), overweight and obesity with educational level and marital status in Chinese twins. Participants were adult twins recruited through the Chinese National Twin Registry (CNTR), aged 18 to 79 years, and the sample comprised 10,448 same-sex twin pairs. Current height, weight, educational attainment, and marital status were self-reported. Regression analyses and structural equation models were conducted to evaluate BMI, overweight, and obesity associated with educational level and marital status in both sexes. At an individual level, both educational level and marital status were associated with higher BMI and higher risk of being overweight and obesity in men, while in women the effects of educational level on BMI were in the opposite direction. In within-Monozygotic (MZ) twin-pair analyses, the effects of educational level on BMI disappeared in females. Bivariate structural equation models showed that genetic factors and shared environmental confounded the relationship between education and BMI in females, whereas marital status was associated with BMI on account of significant positive unique environmental correlation apart in both sexes. The present data suggested that marital status and BMI were associated, independent of familiar factors, for both sexes of this study population, while common genetic and shared environmental factors contributed to education-associated disparities in BMI in females.
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2012). However, few studies have quantified social related- ness between twins reared apart. In 2003, I studied the so- cial relationship information provided for twins in the three early monozygotic reared apart (MZA) twin studies (Juel- Nielsen, 1965; Newman et al., 1937; Shields, 1962). Forty of the 54 pairs for whom information was available devel- oped close social relations soon after meeting (Segal et al., 2003). Based on data from the Minnesota Study of Twins Reared Apart, I also showed that MZA twins expressed greater closeness and familiarity than dizygotic reared apart (DZA) twins, and that both types of twins felt closer to their newly found co-twins than to the unrelated siblings with whom they had been raised (Segal, 2012). More recently, I obtained parental observations of young Chinese twins meeting and leaving one another for the first time (Segal et al., 2011). Only 10 pairs were available at the time (5 MZA and 5 DZA), too few to organize the data by zygosity. How- ever, twins older than 18 months were strongly attracted to one another, while leave-taking behaviors proved more variable. Plans are in place to follow these children as they mature.
Similar to the previous twin study, participant recruit- ment in the ongoing study mainly relies on the assistance of local schools. The research team has also taken advan- tage of more widespread use of social media such as Face- book (HK Bilingual Twin Study), Whatsapp, and the e- banners of websites, and has been able to recruit partici- pants through these forms of social media. The Facebook page of the project also serves as a platform for the dissem- ination of project updates and useful information for twins and their parents. Additionally, the Facebook page is a reg- istry platform for the research team to maintain the par- ticipants’ records and engagement, which is important for conducting a longitudinal twin study. In addition, booklets and posters were created and distributed to NGOs, schools, and related governmental departments. Given the exciting findings obtained from the previous twin study and other research on literacy development in Hong Kong available, the research team organized public seminars to attract more twin participants and enhance the publicity of the project. With heightened public awareness of the twin study, it is ex- pected that participant recruitment will be made easier.
We did not find significant genetic correlation between cognition and the other four indicators of physical function. In our estimates, the correlation between handgrip strength and cognition was very low in both MZ (0.07) and DZ (-0.08) twins. The weak correlation and the reversed pat- tern in MZ and DZ twins (DZ > MZ) did not support or suggest the existence of genetic involvement between them, which complied with the subsequent bivariate analysis that showed no genetic correlations between the two indicators. Although the CTCTCs for cognition with FTSST, near vi- sual acuity, and number of teeth lost were higher in MZ than DZ twins, our twin modeling still failed to reveal the shared genetic basis between them. We concluded that al- though handgrip strength, FTSST, near visual acuity, num- ber of teeth lost, and cognitive function presented moderate heritability, they may be modulated by their own genes and they were less likely to share similar genetic basis.
Epidemiological studies have indicated that hearing and cognitive functions are closely associated with each other in general populations (Schmulian Taljaard et al., 2015). There may be an underlying mechanistic link that regulates the re- lationship between hearing and cognitive function (Wayne & Johnsrude, 2015). Here, we hypothesize that the correla- tion between hearing and cognitive function could be due to genes and/or environment. In the literature, no studies about genetic and/or environmental correlations between hearing and cognitive functions have been found. A num- ber of studies have suggested that the hearing and cogni- tive function are affected by both genetic and environmen- tal factors using twin or family methods (DeStefano et al., 2003; Hendrickx et al., 2013; Karlsson et al., 1997; Momi et al., 2015; Polderman et al., 2015; Viljanen et al., 2007; Wingfield et al., 2007). Although the genetic influences on hearing and cognitive function have been well studied in Western populations, the genetic background for their con- cordance remains unclear. This article first reports results from the first twin study on hearing and cognitive perfor- mance in Chinese middle- and older-aged adult twins as part of a comprehensive investigation on genetic and envi- ronmental regulation on aging-related phenotypes or traits; and second, presents our novel findings on the genetic and environmental bases for the correlation between aging- related hearing and cognitive performances. The findings may have an insight into the genetic basis for hearing and cognition and may also reveal at least the etiology of hear- ing and cognition.
Background: Despite evidence for some genetic control of dietary intake in adults, there is little evidence of how genetic factors influence children’s dietary patterns. Objective: To estimate heritability of dietary intake in twin children from China and test if genetic effects on dietary intakes vary by the children’s socio- economic status (SES). Methods: A sample of 622 twins (162 monozygotic and 149 dizygotic pairs; 298 boys and 324 girls aged 7–15 years) was recruited in South China. Dietary intakes were assessed using a vali- dated 145-item semi-quantitative food frequency questionnaire. Pooled and sex-specific dietary patterns were identified using factor analysis. Heritability was estimated using structural equation models. Results: Heritable components differed by gender and for nutrients and food groups; and estimated heritability of dietary patterns was generally greater in girls than boys. In boys, estimated heritabilities ranged from 18.8% (zinc) to 58.4% (fat) for nutrients; and for food group, 1.1% (Western fast foods) to 65.8% (soft drinks). In girls, these estimates ranged from 5.1% (total energy) to 38.7% (percentage of energy from fat) for nutri- ents, and 12.6% (eggs) to 94.6% (Western fast foods) for food groups. Factor analysis identified five food patterns: vegetables and fruits, fried and fast foods, beverages, snacks and meats. Maternal education and family income were positively associated with higher heritabilities for intake of meat, fried, and fast food. Conclusions: Genetic influence on dietary intakes differed by gender, nutrients, food groups, and dietary patterns among Chinese twins. Parental SES characteristics modified the estimated genetic influence.
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The Fullerton Study of Chinese Twins Reared Apart came about in response to a Canadian mother who had adopted one MZ female twin from China and wrote to me in 2001 for information about raising a ‘singleton twin’. In fact, China’s one-child policy, enacted in 1979, led to the abandonment of hundreds of thousands of female infants; that policy and the cultural preference for male children are indirectly responsible for separating twins, mostly female (Segal, 2005; Segal et al., 2011). I have assessed 23 sepa- rated sets (21 from China and 2 from Vietnam) and com- pleted follow-up visits for approximately half the sample. The twins’ mean age at their first assessment was 9.60 years (SD = 6.48), and ranged between 3.19 and 24.98 years. Twins completed a general intelligence test, and their par- ents completed forms concerning their child’s behavioral problems, medical life histories, family background, and other areas. Companion studies of adopted Chinese twins raised together (CTTs) and virtual twins (VTs; same-age unrelated children of all backgrounds raised together from birth) are also in progress.
Some twins seek psychotherapy to help manage issues aris- ing within their twinship. Unfortunately, very few clini- cal psychologists and psychotherapists are well acquainted with the unique events and circumstances that characterize some twins (e.g., fear of life apart from the co-twin; inabil- ity to connect meaningfully with others), especially twins in identical pairs. (These issues also affect non-twins, but assume a different meaning and significance when twins are involved. That is because social problems stem directly from the twin relationship.) Wright (2010), an identical twin, has written clearly and candidly about her own ex- perience as a twin undergoing psychotherapy for twin re- lationship difficulties. This article should be read by clin-
A museum housed in the original Dionne home is a project that has not moved forward, given the costs that their birth city of North Bay does not want to accept. However, they are pleased that the new Dionne Quints Heritage Board is working to preserve their home and to organize commemorative events (Dionne Quints Heritage Board, 2019). Visitors to their website (https:// dionnequintshome.com/) can view the boards ’ future plans, survey photographs, examine artifacts and watch videotapes of the quints’ early and later behaviors and activities. This museum will, hopefully, prevent the further exploitation of young multiple birth children, as well as anyone whose birth circumstances present unusual professional opportunities to researchers. Annette and Cécile are divided over whether or not their museum will serve as a warning sign that children need protection (Austen, 2017). They can only hope that it will. Unfortunately, as I indicated, there are other examples in which twins were badly abused at the hands of physicians and scientists.
According to the studbook, there are 45 pairs of panda twins living in the captive population of Wolong (243 pan- das in total by the end of 2016): 25 pigeon pairs and 20 same-sex twins. Considering all pigeon pairs are DZ, blood or fecal samples were only collected from 18 pairs of same-sex twins (the missing two pairs were exhibited in other zoos during the study period). All blood samples were obtained from routine health examinations. Total ge- nomic DNA of blood and feces were obtained using Qia- gen Dneasy Blood & Tissue Kit and Qiagen QIAamp DNA Stool Mini Kit, respectively, according to the manufacturer’s instructions.
Untreated TTTS causes intra and perinatal death in 90% of cases. 50% of surviving twins has neurological sequelae as a result of prematurity or death of one twin 34 . TTTS can be diagnosed at any gestational age. Signs of development of TTTS in ultrasound are membrane folding, discordance in fetal growth between the two twins, increased thickness of nuchal translucency and increase in amniotic fluid volumes. When the mother develops acute symptoms related to polyhydramnios like distension of uterus, uterine contractions and dyspnea , TTTS should be a diagnostic consideration 33 .
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Impact on Cerebral Mantle Growth in Donor Twins Overall brain growth, reflected by cBTD, was significantly lin- early associated with GA (Fig 1A). This growth curve was fit to a group-nested model without interaction: [cBTD] ⫽ ⫺ 4.46 ⫹ 2.35 ⫻ [age] ⫺ 3.41 I (group ⫽ donor) ⫹ 0.57 I (group ⫽ recipient) (P value ⫽ .0001). This model implies that the slope of the growth curve is the same for all groups, but the intercepts are significantly different (Fig 1A). The default state of the equation describes the growth curve of control singleton fetuses. The intercept is located at ⫺3.41 for the donor and ⫹ 0.57 for the recipient. The growth curve of donor fetuses is significantly different from that of recipient and con- trol fetuses due to significantly different intercept values (P value ⬍ .0001). There was no significant difference between recipient and control fetuses (P value ⫽ .53). This suggests that the brain development of donor twins during this obser- vation period (early third trimester) was abnormal despite the fact that “gross” MR imaging findings appeared to be normal. The growth curve of CMT is illustrated in Fig 1B. Similar to cBTD, the growth curve of CMT also fits a linear regression model without interaction: [CMT] ⫽ ⫺8.56 ⫹ 0.81 ⫻ [age] ⫺ 1.41 I (group ⫽ donor) ⫹ 0.30 I (group ⫽ recipient) (P value ⬍ .0001). The growth curve of donor fetuses is signif- icantly different from that of recipient and control fetuses due to a significantly different intercept value (P value ⬍ .001). There was no significant difference between recipient and con- trol fetuses (P value ⫽ .39).
The male monozygotic twins with strabismus also presented the same clinical exam. They had a history of sharing the same placenta in the prenatal period. The third sibling, who did not manifest strabismus, had a different placenta. Parents were also unaffected and there was no family history of strabismus in the previous first and second generations. This is the first report in the literature that shows simultaneous observation in monozygotic twins with unaffected parents and dizygotic sibling manifesting similar genetic pattern, reinforcing the genetic basis of strabismus. The constitution of the AHI1 gene contains at least 33 exons and spans 213.7kb . Mutations in this gene were identified in patients with specific types of Joubert syndrome-related disorders . Pathogenic variants in AHI1 were identified in 7.3% of 137 individuals with Joubert syndrome . Additionally, about 80% of them had retinal dystrophy . Herein, genetic analysis also points to AHI1 as a potential target associated with congenital esotropia, possibly through an additive effect. AHI1 amplified in all the patients of the control group and it did not amplify in any of the individuals with infantile esotropia and the familial control group.
This study did not find a correlation between zygosity and gender with twins reared apart, meaning it could not be said that twins of a certain zygosity or gender were more likely to be reared apart. However, age and region were discovered to be correlated with the proportion of twins reared apart, and, in particular, their age. As age grew, the proportion experienced linear growth. This implies that it is easier to find twins reared apart as ages increase. There could be two reasons for this phenomenon. The first could be due to economic influence. The other could be Chi- nese child policy in the past. Twins might be adopted by relatives or friends without children because their parents could not raise twins in a poor family or they had already had too many children. This is different from the MISTRA study, in which twins were separated mainly because of il- legitimate birth (44.5%) and financial limitations (13.1%) (Segal, 2012). At present, China is in a transformative stage. Under the influence of both rapid economic growth and the one child policy, twins become a pleasant surprise for the majority of families and are therefore more likely to grow up within the same family. Thus, although twins reared apart are a valuable resource for genetic epidemiological studies, they are rarer and more difficult to find. This makes the currently available resources involving twins reared apart more valuable, and these resources should be fully uti- lized by researchers. As for the regional distribution, we found only limited information based on this study. Zhe- jiang, Beijing, and Shanghai, the top three provinces/cities, are all in the east of China. However, Qingdao (Shandong Province), with the lowest percentage of twins separated when they were 0–10 years old, is also an eastern region. In addition, Zhejiang and Shanghai are in southern of China, while Beijing is in the north. Further investigation is necessary in order to answer questions about regional distribution.
The results of multiple regression models examining the associations of obesity indicators with BP components in the whole twin sample as well as within MZ twin pairs are presented in Tables 3 and 4. In the whole sample, treat- ing twins as individuals, a positive relationship was ob- served between obesity indicators and BP components in both genders (Table 3). In further analyses controlling for familial factors within 248 MZ twin pairs, obesity indicators still exerted significant associations with BP components (Table 4). In order to compare the strength of the associ- ation for various obesity indicators in relation to BP com- ponents, we further standardized all the obesity indicators into z scores and performed similar linear regression within MZ twin pairs. As shown in the bottom of Table 4, there ex- isted a stronger positive correlation of BP components with BMI than with other measures of obesity. The proportion of the variance in the levels of BP components explained by obesity indicators varied (6–11%), and obesity indicators in our models with larger β coefficients had relatively higher R 2 values, accounting for more variability of the BP compo-
The British neurologist and author, Oliver Sacks, passed away in August 2016, leaving a rich professional and per- sonal legacy. One of my favorite essays included in his well- known collection, The Man Who Mistook His Wife for a Hat (Sacks, 1985), is simply titled ‘The Twins’. The identi- cal twins in questions, John and Michael, were 26-year-old autistic savants. They displayed extraordinary memory and abilities to manipulate numbers, skills that brought them a great deal of joy. Sadly, their physicians separated them in 1977 to prevent what they saw as the twins’ injurious communication with one another, a decision that cost them their remarkable mental skills and their life’s happiness.
Thoracopagus conjoined twins (twins joined from the upper thorax to the umbilicus) were detected in a 24-year- old mother who had delivered two children previously. Conjoined twinning was confirmed by two-dimensional ultrasound, generating images that were shown and ex- plained to the parents by their physicians. During this ses- sion, the parents were informed that the structural connec- tions between the twins made the twins’ survival virtually impossible. However, the couple had had difficulty compre- hending the severity of their situation. Many people hear news accounts describing successful conjoined twin sepa- rations, so they may entertain unreasonable expectations as to what surgical intervention can accomplish. Next, the par- ents viewed three-dimensional images of the twins, which were more realistic and easier to understand. This experi- ence assuages parental concerns, enables parental bonding with their unborn infants, and encourages more informed decision-making. The parents in this case chose to termi- nate the pregnancy.
Absence of the factors, such as universality, uniqueness, permanence, and acceptability, leads to a weak recogni- tion system with high error rates. Therefore, all the factors must be available at the same time in order to get a good distinguishing system. In all the cases, the face trait meets the aforementioned factors perfectly which makes it a good choice as a biometric trait. However, there is a case of face recognition that represents the main challenges with one of those factors which is identical (monozygotic) twins case . In identical twins case, universality, per- manence, and acceptability are satisfied, but the factor that represents a serious problem is the uniqueness. It is axiomatic that the identical twins have the same face shape, size, and features, so new methods and algorithms should be studied and considered in order to deal with the high similarities in case of identical twins. It is obvious
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