The effect of perceived social support on fatigue in mothers having twin infants: the mediating role of sleep quality.

The aim of this study is to investigate the mediating role of sleep quality in the relationship between multidimensional perceived social support and fatigue among mothers of twin infants. One hundred and six (106) twin mothers participated in this cross-sectional study, who completed the Descriptive Information Form, Multidimensional Scale of Perceived Social Support, Pittsburgh Sleep Quality Index, and Checklist Individual Strength. The scale score averages of the mothers in the study are as follows: social support, 61.41 ± 23.86; fatigue, 77.64 ± 28.68; and sleep quality, 8.26 ± 2.38. According to the path model, perceived social support has a negative effect on poor sleep quality (p = .001, Beta = -0.411), and poor sleep quality has a positive effect on fatigue (p = .001, Beta = 0.335). Sleep quality also mediates the effect of multidimensional perceived social support on mothers' fatigue levels (p = .001, Beta = -0.138). The study results suggest that the perceived social support and fatigue levels of twin mothers are moderate, while their sleep quality is poor. Therefore, mothers of twin infants may benefit from increased social support to alleviate fatigue and enhance sleep quality.

Literary tastes are as heritable as other human phenotypes: Evidence from twins' library borrowing.

Social science research argues that differences in individuals' literary and cultural tastes originate in social environments. Yet, it might be that these differences are partly associated with genetic differences between individuals. To address this possibility, we use nation-scale registry data on library borrowing among Danish twins (N = 67,900) to assess the heritability of literary tastes. We measure literary tastes via borrowing of books of different genres (e.g., crime and biographical novels) and formats (physical, digital, and audio) and decompose the total variance in literary tastes into components attributable to shared genes (heritability), shared environments (social environment shared by siblings), and unique environments (social environments not shared by siblings). We find that genetic differences account for 45-70 percent of the total variance in literary tastes, shared environments account for almost none of the variance, and unique environments account for a moderate share. These results suggest that literary tastes are approximately as heritable as other human phenotypes (e.g., physical traits, cognition, and health). Moreover, heritability is higher for socioeconomically disadvantaged groups than for advantaged groups. Overall, our results suggest that research should consider the role of genetic differences in accounting for individual differences in literary and broader cultural tastes.

Five years of change in adult twins: longitudinal changes of genetic and environmental influence on epigenetic clocks.

BACKGROUND: Epigenetic clocks were known as promising biomarkers of aging, including original clocks trained by individual CpG sites and principal component (PC) clocks trained by PCs of CpG sites. The effects of genetic and environmental factors on epigenetic clocks are still unclear, especially for PC clocks. METHODS: We constructed univariate twin models in 477 same-sex twin pairs from the Chinese National Twin Registry (CNTR) to estimate the heritability of five epigenetic clocks (GrimAge, PhenoAge, DunedinPACE, PCGrimAge, and PCPhenoAge). Besides, we investigated the longitudinal changes of genetic and environmental influences on epigenetic clocks across 5 years in 134 same-sex twin pairs. RESULTS: Heritability of epigenetic clocks ranged from 0.45 to 0.70, and those for PC clocks were higher than those for original clocks. For five epigenetic clocks, the longitudinal stability was moderate to high and was largely due to genetic effects. The genetic correlations between baseline and follow-up epigenetic clocks were moderate to high. Special unique environmental factors emerged both at baseline and at follow-up. PC clocks showed higher longitudinal stability and unique environmental correlations than original clocks. CONCLUSIONS: For five epigenetic clocks, they have the potential to identify aging interventions. High longitudinal stability is mainly due to genetic factors, and changes of epigenetic clocks over time are primarily due to changes in unique environmental factors. Given the disparities in genetic and environmental factors as well as longitudinal stability between PC and original clocks, the results of studies with original clocks need to be further verified with PC clocks.

Unveiling the epigenetic impact of vegan vs. omnivorous diets on aging: insights from the Twins Nutrition Study (TwiNS).

BACKGROUND: Geroscience focuses on interventions to mitigate molecular changes associated with aging. Lifestyle modifications, medications, and social factors influence the aging process, yet the complex molecular mechanisms require an in-depth exploration of the epigenetic landscape. The specific epigenetic clock and predictor effects of a vegan diet, compared to an omnivorous diet, remain underexplored despite potential impacts on aging-related outcomes. METHODS: This study examined the impact of an entirely plant-based or healthy omnivorous diet over 8 weeks on blood DNA methylation in paired twins. Various measures of epigenetic age acceleration (PC GrimAge, PC PhenoAge, DunedinPACE) were assessed, along with system-specific effects (Inflammation, Heart, Hormone, Liver, and Metabolic). Methylation surrogates of clinical, metabolite, and protein markers were analyzed to observe diet-specific shifts. RESULTS: Distinct responses were observed, with the vegan cohort exhibiting significant decreases in overall epigenetic age acceleration, aligning with anti-aging effects of plant-based diets. Diet-specific shifts were noted in the analysis of methylation surrogates, demonstrating the influence of diet on complex trait prediction through DNA methylation markers. An epigenome-wide analysis revealed differentially methylated loci specific to each diet, providing insights into the affected pathways. CONCLUSIONS: This study suggests that a short-term vegan diet is associated with epigenetic age benefits and reduced calorie intake. The use of epigenetic biomarker proxies (EBPs) highlights their potential for assessing dietary impacts and facilitating personalized nutrition strategies for healthy aging. Future research should explore the long-term effects of vegan diets on epigenetic health and overall well-being, considering the importance of proper nutrient supplementation. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT05297825.

Overlapping genetic influences between creativity and borderline personality symptoms in a large Dutch sample.

Creativity and mental disorders are sometimes seen as intertwined, but research is still unclear on whether, how much, and why. Here we explore the potential role of shared genetic factors behind creativity and symptoms of borderline personality disorder (BPD, characterized by mood swings and randomness of thoughts). Data were collected from 6745 twins (2378 complete pairs) by the Netherlands Twin Register on BPD scores (PAI-BOR questionnaire) and working in a creative profession (proxy for creativity). First, we tested whether there is an association between BPD symptoms and creative professions. Results confirmed that individuals scoring higher on the BPD spectrum are more likely to have a creative profession (Cohen's d = 0.16). Next, we modeled how much of this association reflects underlying genetic and/or environmental correlations-by using a bivariate classical twin design. We found that creativity and BPD were each influenced by genetic factors (heritability = 0.45 for BPD and 0.67 for creativity) and that these traits are genetically correlated rG = 0.17. Environmental influences were not correlated. This is evidence for a common genetic mechanism between borderline personality scores and creativity which may reflect causal effects and shed light on mechanisms.

Characteristics of unilateral and bilateral bovine twin foetuses.

Twin pregnancy in cattle is undesirable for a number of reasons, including a higher abortion risk compared to pregnancies with a single foetus. Yet, the abortion risk is significantly influenced by the intrauterine location of the foetuses, that is, the abortion risk is several times higher if they are implanted in the same uterine horn (unilateral twin pregnancy) than if they are implanted with one foetus in each uterine horn (bilateral twin pregnancy). The reason for the higher abortion risk in unilateral twin pregnancies is unknown, but it may be related to malnutrition of the outermost foetus due to a limited placental capacity, as is the case for equine twin foetuses. A slaughterhouse study was performed and the foetuses of cattle pregnant with twins were measured. We identified 65 cases of twin pregnancies, of which 35 were unilateral twin pregnancies and 30 were bilateral twin pregnancies. There was no significant difference between the outermost and the more centrally located foetus in unilateral twin pregnancies in terms of body weight and length of the metacarpal diaphysis. Growth retardation of the outermost foetus could therefore not be confirmed as the cause of the higher abortion risk in unilateral bovine twin pregnancies. Four cases of pre-slaughter foetal mortality were identified. In three of these cases, both twins were dead, of equal size and at a comparable level of degradation. In the fourth case, with approximately 40-day-old twin foetuses of equal size, only one of the foetuses showed signs of pre-slaughter death.

Testing Quantitative and Qualitative Sex Effects in a National Swedish Twin-Sibling Study of Posttraumatic Stress Disorder.

OBJECTIVE: Twin studies have demonstrated that posttraumatic stress disorder (PTSD) is moderately heritable, and the pattern of findings across studies suggests higher heritability in females compared with males. Formal testing of sex differences has yet to be done in twin studies of PTSD. The authors sought to estimate the genetic and environmental contributions to PTSD, and to formally test for sex differences, in the largest sample to date of both sexes, among twins and siblings. METHODS: Using the Swedish National Registries, the authors performed structural equation modeling to decompose genetic and environmental variance for PTSD and to formally test for quantitative and qualitative sex differences in twins (16,242 pairs) and in full siblings within 2 years of age of each other (376,093 pairs), using diagnostic codes from medical registries. RESULTS: The best-fit model suggested that additive genetic and unique environmental effects contributed to PTSD. Evidence for a quantitative sex effect was found, such that heritability was significantly greater in females (35.4%) than males (28.6%). Evidence of a qualitative sex effect was found, such that the genetic correlation was high but less than complete (rg=0.81, 95% CI=0.73-0.89). No evidence of shared environment or special twin environment was found. CONCLUSIONS: This is the first demonstration of quantitative and qualitative sex effects for PTSD. The results suggest that unique environmental effects, but not the shared environment, contributed to PTSD and that genetic influences for the disorder are stronger in females compared with males. Although the heritability is highly correlated, it is not at unity between the sexes.

Sacrificed Maya boys tied to myth of 'Hero Twins'.

Ancient DNA shows continuity between living and ancient Maya communities.

Adolescent leisure-time physical activity and eating disorders: a longitudinal population-based twin study.

PURPOSE: High levels of physical activity have been documented in eating disorder patients. Our aim was to examine whether adolescent leisure-time physical activity is prospectively associated with eating disorders in adolescence and young adulthood. METHODS: Finnish twins born in 1983-1987 reported their physical activity frequency at ages 12, 14, and 17. A subsample of participants underwent structured, retrospective interviews for eating disorders at the mean age of 22.4 years. Associations between female twins' physical activity and future eating disorders (571-683 twins/wave) were investigated with the Cox proportional hazards model. To illustrate the physical activity similarity of the co-twins in a twin pair, we used cross-tabulation of eating disorder-discordant twin pairs (13-24 pairs/wave). RESULTS: After adjusting for several covariates, we found no statistically significant longitudinal association between physical activity and eating disorders. This applied when all eating disorders were combined but also when assessed separately as restrictive and non-restrictive eating disorders. Co-twins' physical activity in adolescence tended to be similar irrespective of their future eating disorder, supporting the results of the regression analysis. CONCLUSION: We observed no evidence of adolescent physical activity frequency being prospectively associated with eating disorders in female twins. Further longitudinal studies with larger sample sizes and more detailed physical activity data are needed. LEVEL OF EVIDENCE: III, evidence obtained from cohort or case-control analytic studies.

Familial confounding or measurement error? How to interpret findings from sibling and co-twin control studies.

Epidemiological researchers often examine associations between risk factors and health outcomes in non-experimental designs. Observed associations may be causal or confounded by unmeasured factors. Sibling and co-twin control studies account for familial confounding by comparing exposure levels among siblings (or twins). If the exposure-outcome association is causal, the siblings should also differ regarding the outcome. However, such studies may sometimes introduce more bias than they alleviate. Measurement error in the exposure may bias results and lead to erroneous conclusions that truly causal exposure-outcome associations are confounded by familial factors. The current study used Monte Carlo simulations to examine bias due to measurement error in sibling control models when the observed exposure-outcome association is truly causal. The results showed that decreasing exposure reliability and increasing sibling-correlations in the exposure led to deflated exposure-outcome associations and inflated associations between the family mean of the exposure and the outcome. The risk of falsely concluding that causal associations were confounded was high in many situations. For example, when exposure reliability was 0.7 and the observed sibling-correlation was r = 0.4, about 30-90% of the samples (n = 2,000) provided results supporting a false conclusion of confounding, depending on how p-values were interpreted as evidence for a family effect on the outcome. The current results have practical importance for epidemiological researchers conducting or reviewing sibling and co-twin control studies and may improve our understanding of observed associations between risk factors and health outcomes. We have developed an app (SibSim) providing simulations of many situations not presented in this paper.

A qualitative investigation of experiences of breastfeeding twins and multiples.

BACKGROUND: Research has found that twins and multiples are less likely to be breastfed than singleton babies. Exploration of the experience of breastfeeding twins and multiples from parents' perspectives is limited, and we know little about the experiences of those who breastfeed twins and multiples and the possible barriers they face. AIM: The aim of the research was to explore experiences of breastfeeding twins and multiples in the UK from the perspective of birthing parents. METHODS: A qualitative online survey was carried out (n = 94), followed by online semi-structured interviews (n = 18). The data were analysed using reflexive thematic analysis. FINDINGS: Four themes were developed from the data: (1) "It's one of the things I'm most proud of in my life" (2) The importance of support: "it definitely takes a village with twins" (3) Barriers and the pressure to formula feed: "all they wanted to do was stuff 'em full of formula" and (4) The dynamic experience of breastfeeding twins. DISCUSSION: Many of the participants were able to feed their babies in part due to sheer determination and the refusal to give up when met with challenges. Breastfeeding was an important part of their identity as a mother, however mental health was often impacted by their experiences, as well as the challenges they faced when seeking support. CONCLUSION: Breastfeeding twins and multiples is a challenging yet rewarding experience. Our findings indicate that further training and support is needed to enable healthcare providers to support parents of twins on their breastfeeding journey.

Neonatal respiratory complications in twins at 36-38 weeks of gestation.

BACKGROUND: Twin pregnancies are associated with a high risk of perinatal mortality and morbidity. Late preterm or early term delivery is frequently performed to avoid unexpected fetal death in uncomplicated twin pregnancies. Nonetheless, delivery before full term is associated with neonatal respiratory complications. This study aimed to evaluate perinatal respiratory complications in twins delivered between 36 and 38 weeks of gestation. METHODS: A retrospective cohort study was conducted on twins delivered between 36 and 38 weeks of gestation from January 2008 to June 2020. The primary outcomes were the incidence of composite neonatal respiratory morbidity, which included respiratory distress syndrome, transient tachypnea of the newborn, meconium aspiration syndrome, mechanical ventilation or continuous positive airway pressure according to gestational age at delivery, and chorionicity. The relationship between gestational age at delivery and composite neonatal respiratory morbidity was evaluated using multivariate logistic regression analysis adjusted for potential confounders. RESULTS: This study included 1608 twins (614 monochorionic diamniotic twins, 994 dichorionic diamniotic twins). At 36, 37, and 38 weeks of gestation, the frequencies of composite neonatal respiratory morbidity were 19.4%, 10.7%, and 9.2% in dichorionic diamniotic twins and 13.6%, 8.7%, and 9.4% in monochorionic diamniotic twins, respectively. In dichorionic diamniotic twins, the composite neonatal respiratory morbidity rate was higher for twins delivered at 36 weeks of gestation than for those delivered at 37 weeks. No significant differences between monochorionic diamniotic twins were detected. CONCLUSIONS: In uncomplicated dichorionic diamniotic twin pregnancies, delivery should be considered after 37 weeks of gestation to reduce neonatal respiratory complications.

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OBJECTIVES: To investigate the risk factors for bronchopulmonary dysplasia (BPD) in twin preterm infants with a gestational age of <34 weeks, and to provide a basis for early identification of BPD in twin preterm infants in clinical practice. METHODS: A retrospective analysis was performed for the twin preterm infants with a gestational age of <34 weeks who were admitted to 22 hospitals nationwide from January 2018 to December 2020. According to their conditions, they were divided into group A (both twins had BPD), group B (only one twin had BPD), and group C (neither twin had BPD). The risk factors for BPD in twin preterm infants were analyzed. Further analysis was conducted on group B to investigate the postnatal risk factors for BPD within twins. RESULTS: A total of 904 pairs of twins with a gestational age of <34 weeks were included in this study. The multivariate logistic regression analysis showed that compared with group C, birth weight discordance of >25% between the twins was an independent risk factor for BPD in one of the twins (OR=3.370, 95%CI: 1.500-7.568, P<0.05), and high gestational age at birth was a protective factor against BPD (P<0.05). The conditional logistic regression analysis of group B showed that small-for-gestational-age (SGA) birth was an independent risk factor for BPD in individual twins (OR=5.017, 95%CI: 1.040-24.190, P<0.05). CONCLUSIONS: The development of BPD in twin preterm infants is associated with gestational age, birth weight discordance between the twins, and SGA birth.

Ancient genomes reveal insights into ritual life at Chichén Itzá.

The ancient city of Chichén Itzá in Yucatán, Mexico, was one of the largest and most influential Maya settlements during the Late and Terminal Classic periods (AD 600-1000) and it remains one of the most intensively studied archaeological sites in Mesoamerica1-4. However, many questions about the social and cultural use of its ceremonial spaces, as well as its population's genetic ties to other Mesoamerican groups, remain unanswered2. Here we present genome-wide data obtained from 64 subadult individuals dating to around AD 500-900 that were found in a subterranean mass burial near the Sacred Cenote (sinkhole) in the ceremonial centre of Chichén Itzá. Genetic analyses showed that all analysed individuals were male and several individuals were closely related, including two pairs of monozygotic twins. Twins feature prominently in Mayan and broader Mesoamerican mythology, where they embody qualities of duality among deities and heroes5, but until now they had not been identified in ancient Mayan mortuary contexts. Genetic comparison to present-day people in the region shows genetic continuity with the ancient inhabitants of Chichén Itzá, except at certain genetic loci related to human immunity, including the human leukocyte antigen complex, suggesting signals of adaptation due to infectious diseases introduced to the region during the colonial period.

Posttraumatic Stress Disorder and Obstructive Sleep Apnea in Twins.

Importance: Obstructive sleep apnea (OSA) is a common condition in older adult (aged >65 years) populations, but more mechanistic research is needed to individualize treatments. Previous evidence has suggested an association between OSA and posttraumatic stress disorder (PTSD) but is limited by possible selection bias. High-quality research on this association with a careful evaluation of possible confounders may yield important mechanistic insight into both conditions and improve treatment efforts. Objective: To investigate the association of current PTSD symptoms and PTSD diagnosis with OSA. Design, Setting, and Participants: This cross-sectional study of twin pairs discordant for PTSD, which allows for adjustment for familial factors, was conducted using in-laboratory polysomnography from March 20, 2017, to June 3, 2019. The study sample comprised male veteran twins recruited from the Vietnam Era Twin Registry. The data analysis was performed between June 11, 2022, and January 30, 2023. Exposure: Symptoms of PTSD in twins who served in the Vietnam War. Diagnosis of PTSD was a secondary exposure. Main Outcomes and Measures: Obstructive sleep apnea was assessed using the apnea-hypopnea index (AHI) (≥4% oxygen saturation criterion as measured by events per hour) with overnight polysomnography. Symptoms of PTSD were assessed using the PTSD Checklist (PCL) and structured clinical interview for PTSD diagnosis. Results: A total of 181 male twins (mean [SD] age, 68.4 [2.0] years) including 66 pairs discordant for PTSD symptoms and 15 pairs discordant for a current PTSD diagnosis were evaluated. In models examining the PCL and OSA within pairs and adjusted for body mass index (BMI) and other sociodemographic, cardiovascular, and psychiatric risk factors (including depression), each 15-point increase in PCL was associated with a 4.6 (95% CI, 0.1-9.1) events-per-hour higher AHI. Current PTSD diagnosis was associated with an adjusted 10.5 (95% CI, 5.7-15.3) events-per-hour higher AHI per sleep-hour. Comparable standardized estimates of the association of PTSD symptoms and BMI with AHI per SD increase (1.9 events per hour; 95% CI, 0.5-3.3 events per hour) were found. Conclusions and Relevance: This cross-sectional study found an association between PTSD and sleep-disordered breathing. The findings have important public health implications and may also enhance understanding of the many factors that potentially affect OSA pathophysiology.

Zygotic-splitting after in vitro fertilization and prenatal parenthood testing after suspected embryo mix-up - a case report.

After in vitro fertilization with a single embryo, the parents learned about being pregnant with twins in the 10th week with various indications that an embryonic mix-up could have taken place. The affected couple thus expressed the urgent desire for a clarification of parenthood considering an abortion. However, the prenatal test results would not have been available until the 14/15th week of pregnancy. Legally, then, severe physical or mental distress of the pregnant woman must be claimed by physicians to justify an abortion after the twelfth week. However, a lack of genetic relatedness could lead to serious psychological distress for the parents, making a pregnancy termination possible even after the twelfth week, which is discussed in this case study alongside the interdisciplinary team's ethical, legal, and medical considerations.For the invasive relationship testing, cultivated chorionic villi samples (CVS) from both unborn and saliva samples from the putative parents were genetically analyzed using classical short tandem repeats (STR) analysis. The perfect match of both CVS profiles suggested the occurrence of an unusual late twin shaft, for which, fortunately, parenthood could be confirmed. To our knowledge, this is the first report on a prenatal investigation of a suspected embryo mix-up after assisted reproductive technology (ART), in which parenthood should be fixed. We want to draw attention to this unthinkable scenario, which may increase in the future with ART-induced rising multiple pregnancies.

Adolescents' Perceptions of Household Chaos Predict Their Adult Mental Health: A Twin-Difference Longitudinal Cohort Study.

This study tested whether adolescents who perceived less household chaos in their family's home than their same-aged, same-sex sibling achieved more favorable developmental outcomes in young adulthood, independent of parent-reported household chaos and family-level confounding. Data came from 4,732 families from the Twins Early Development Study, a longitudinal, U.K.-population representative cohort study of families with twins born in 1994 through 1996 in England and Wales. Adolescents who reported experiencing greater household chaos than their sibling at the age of 16 years suffered significantly poorer mental-health outcomes at the age of 23 years, independent of family-level confounding. Mental-health predictions from perceived household chaos at earlier ages were not significant, and neither were predictions for other developmental outcomes in young adulthood, including socioeconomic status indicators, sexual risk taking, cannabis use, and conflict with the law. The findings suggest that altering children's subjective perceptions of their rearing environments may help improve their adult mental health.