Comparison of the Coincidence of Osteoporosis,Fracture, Arthritis Histories,and DEXA T-Score between Monozygotic and Dizygotic Twins: A Cross-Sectional Study Using KoGES HTS Data

We explored the genetic and environmental inter-relationships among osteoporosis, fracture, arthritis, and bone mineral density concordance in monozygotic twins compared to those in dizygotic twins. This cross-sectional research assessed data of 1032 monozygotic and 242 dizygotic twin pairs aged >20 years included in the Healthy Twin Study data of the Korean Genome and Epidemiology Study between 2005 and 2014. Outcomes of interest included illness concordance and absolute differences in dual-energy X-ray absorptiometry (DEXA) T-scores. We found comparable concordances of osteoporosis, fractures, osteoarthritis, and rheumatoid arthritis between monozygotic and dizygotic twins. Medical histories of osteoporosis, fractures caused by accident or falling, osteoarthritis, and rheumatoid arthritis were not distinct between monozygotic and dizygotic twins. Accidental fracture occurrence in both monozygotic twins showed significantly lower odds than that in dizygotic twins. Genetic influence on liability to fracture risk might thus be maintained. DEXA T-scores for bone mineral density indicated more comparable tendencies within monozygotic twin pairs than within dizygotic ones, suggesting the relative importance of genetic contribution to bone mineral density. The relative importance of genetic factors in bone mineral density is sustained between monozygotic twins; overt disease expression of osteoporosis, fractures, or arthritis may be affected by environmental factors.     

Contribution of genetic and environmental influences to ankle-brachial blood pressure index in the NHLBI Twin Study. National Heart, Lung, and Blood Institute

The ankle-brachial index (ABI) is widely used in the clinical diagnosis of peripheral arterial disease. The contributions of genetic and environmental influences to normal and abnormal ABI values are unknown. In this study, the authors used available data on 94 monozygotic pairs and 90 dizygotic pairs of elderly, White, male twins examined in 1995-1997 to investigate the contributions of genetic and environmental influences to normative ABI values. Within-twin-pair correlations for normative ABI values were statistically significant, and the correlation in monozygotic twin pairs was significantly greater than that in dizygotic pairs. Structural equation modeling of the variance-covariance matrices of monozygotic and dizygotic twins indicated that 48% of the observed variability in ABI values could be attributed to additive genetic effects. In contrast, concordance rates for low ABI values (ABI< or =0.9) for both monozygotic and dizygotic twins were significantly greater than would be expected by chance alone, but within-pair monozygotic similarity was not significantly greater than dizygotic similarity. A matched-cotwin analysis in 21 pairs that were discordant for low ABI values found that twins with low ABI values were physically less active and more likely to be persistent smokers than their normal-control brothers. These findings reinforce the role of individual health practices (e.g., physical activity, smoking) in the manifestation of peripheral arterial disease among subjects matched for age, genetics, and early shared environment.     

Comparison of the Concordance of Cardiometabolic Diseases and Physical and Laboratory Examination Findings between Monozygotic and Dizygotic Korean Adult Twins: A Cross-Sectional Study Using KoGES HTS Data

This study investigated the contribution of genetic and environmental factors to cardiometabolic diseases (CMDs) by comparing disease concordance in monozygotic and dizygotic twins. This cross-sectional study analyzed 1294 (1040 monozygotic and 254 dizygotic) twin pairs (>20 years) based on the Korean Genome and Epidemiology Study data (2005–2014). The odds ratios of disease concordance were calculated using binomial and multinomial logistic regression models. The occurrence of CMDs (hypertension, hyperlipidemia, type 2 diabetes, cerebral stroke, transient ischemic attack, and ischemic heart disease) and related physical and laboratory levels did not differ between the monozygotic and dizygotic twin groups. The odds for concordance of the presence/absence of CMDs and the likelihood of incident CMD within monozygotic twins were comparable to that of dizygotic twins. The absolute differences in hemoglobin A1c, insulin, low- and high-density lipoprotein cholesterol, total cholesterol, triglycerides, and systolic blood pressure were lower in monozygotic twins than in dizygotic twins. Absolute differences in fasting glucose and diastolic blood pressure did not differ between groups. Although baseline levels of several laboratory parameters related to CMD showed a strong likelihood of heritability in monozygotic twins, CMD phenotype appears to be largely affected by environmental factors.     

Comparative study of the consumption of cariogenic food in monozygotic and same-sex dizygotic twins

The eating habits of the 111 monozygotic and 67 like-sexed dizygotic twins were compared with respect to cariogenic foods. The food habits were recorded using a seven-day dietary history with the weekly frequency of the cariogenic foods examined. The biometrical analysis showed that the eating habits of the monozygotic pairs were more similar than that of the dizygotic twin pairs. The differences were statistically significant. Based on these findings, it seems that genetic factors play a role in the development of the food habits.     

Disease concordance and sex similarity in twins

Disease patterns in twins may show the presence of genetic or of environmental causes. Two arguments of inference have been used. Discordances between monozygotic twins have been taken to indicate the presence of environmental determinants; and high levels of concordance in monozygotic (MZ) pairs compared with dizygotic (DZ) pairs have been taken to indicate the presence of genetic causes. Neither argument is rigorous and, at this level, neither is quantitative.     

The correlation of fecundability among twins: evidence of a genetic effect on fertility?

BACKGROUND: Numerous rare genetic conditions are known to influence fecundability in both males and females. It is less clear to what extent more subtle genetic differences influence fecundability on a population level. METHODS: In 1994 a population-based survey was conducted among Danish twins born 1953-1982. Fecundability was assessed as the waiting time to pregnancy at the first attempt to achieve a pregnancy. RESULTS: The reported time to pregnancy for males was slightly shorter than for females but there were no sex differences in intrapair similarity. We found an intrapair correlation in time to pregnancy for 645 monozygotic twin pairs (r = 0.22; 95% confidence interval = 0.12 to 0.32), but no intrapair correlation for 826 like-sex dizygotic twin pairs (r = 0.00; 95% confidence interval = -0.09 to 0.10). CONCLUSIONS: The correlation in time to pregnancy for monozygotic twins suggests genetic factors, although similarities in reporting behaviors could also be contributing to the correlation. The lack of correlation in time to pregnancy for dizygotic twins indicates that possible genetic factors of importance for fecundabililty are acting nonadditively. Hence, it may prove difficult to identify specific gene variants that influence fecundability on a population level if their effects depend on gene-gene interactions.     

Genetic effects on weight change and food intake in Swedish adult twins

BACKGROUND: Obesity is influenced by genetic and environmental factors. Additionally, synergistic effects of genes and environments may be important in the development of obesity. OBJECTIVE: The aim of this study was to test for genetic effects on food consumption frequency, food preferences, and their interaction with subsequent weight gain. DESIGN: Complete data on the frequencies of consumption of 11 foods typical of the Swedish diet were available for 98 monozygotic and 176 dizygotic twin pairs aged 25-59 y who are part of the Swedish Twin Registry. The data were collected in 1973 as part of a questionnaire study. Body mass index was measured in 1973 and again in 1984. RESULTS: There was some evidence that genetic effects influenced the frequency of intake of some foods. Similarity among monozygotic twins exceeded that among dizygotic twins for intake of flour and grain products and fruit in men and women, intake of milk in men, and intake of vegetables and rice in women, suggesting that genes influence preferences for these foods. Analyses conducted for twins reared together and apart also suggested greater monozygotic than dizygotic correlations, but cross-twin, cross-trait correlations were all insignificant, suggesting that the genes that affect consumption frequencies are not responsible for mediating the relation between the frequency of intake and weight change. CONCLUSIONS: Genetic effects and the frequency of intake are independently related to change in body mass index. However, there was no suggestion of differential genetic effects on weight gain that were dependent on the consumption frequency of the foods studied.     

成年双生子血尿酸遗传度研究

目的 用双生子研究方法 对成年人血尿酸的遗传度进行估计.方法 从青岛双生子库募集成年双生子.测量身高、体重和血尿酸.相同性别的双生子采用16个多态标记进行卵型鉴定.通过校正年龄、性别和BMI,来构建结构方程模型估计遗传度.结果 共收集687对双生子数据,其中同卵双生子420对,异卵双生子267对.经平方根转换后,男性血尿酸水平(17.47±1.91)略高于女性(15.22±1.70)(P＜0.0001),通过校正年龄、性别和BMI后双生子血尿酸的组内相关系数分别为,同卵双生子0.70、异卵双生子0.40.运用性别限制模型进行拟合,最佳模型AE模型,加性别遗传因素和特殊环境因素共同作用血尿酸的水平.血尿酸的遗传度为70.5%(95%CI:65.9～74.6),特殊环境因素占29.5%(95%CI:25.4～34.2).结论 遗传因素是影响样本双生子血尿酸水平的主要因素.     

The role of genetic and environmental factors in the association between birthweight and blood pressure: evidence from meta-analysis of twin studies

BACKGROUND: An inverse association between birthweight and later blood pressure has been found in many studies in singletons. Twin studies have been used to examine whether genetic factors or family environment could account for this association. METHODS: A systematic review identified 10 studies covering 3901 twin pairs. Meta-analysis of regression coefficients for the association between birthweight and systolic blood pressure was carried out for unpaired versus paired associations and for paired associations in dizygotic versus monozygotic pairs. RESULTS: After adjustment for current weight or body mass index (BMI), the difference in systolic blood pressure per kg birthweight was -2.0 (95% CI: -3.2, -0.8) mmHg in the unpaired analysis and -0.4 (95% CI: -1.5, 0.7) mmHg in the paired analysis in the same subjects. In the paired analysis by zygosity, in all twins the coefficients were -0.7 (95% CI: -2.3, 0.8) mmHg in dizygotic pairs and -0.8 (95% CI: -2.1, 0.4) mmHg in monozygotic pairs, but in studies which included zygosity tests the coefficients were -1.0 (95% CI: -3.3, 1.6) mmHg in dizygotic pairs and -0.4 (95% CI: -1.9, 1.3) mmHg in monozygotic pairs. CONCLUSIONS: The attenuation of the regression coefficient in the paired analysis provides support for the possibility that factors shared by twins contribute to the association between birthweight and blood pressure in singletons. Comparison of paired analysis in monozygotic and dizygotic pairs could not provide conclusive evidence for a role for genetic as opposed to shared environmental factors.     

Statistical methods for the analysis of twin data

The most important statistical methods currently used for the analysis of twin data are described. The main objective of these methods is to estimate the contribution of the genetic and environmental factors to the variability of normal or pathological human traits, by means of the information obtained from monozygotic and dizygotic twin pairs. In this context, the concept of heritability becomes relevant. Not only the simple comparison between monozygotic and dizygotic twins, based on measures such as the concordance and the correlation, but also new and more complex approaches are presented, with a special emphasis on the structural equation models, and a synthetic view on the DF-analysis and the correlated frailty models. Some examples of applications to the data of the Italian Twin Registry are also illustrated.     

Differences in Nutritional Intake,Total Body Fat,and BMI Score between Twins

The present study aimed to investigate the coincidence of obesity and nutritional intake in monozygotic twins compared to dizygotic twins. The data from the Korean Genome and Epidemiology Study (KoGES) from 2005 through 2014 were analyzed. Participants ≥ 20 years old were enrolled. The 1006 monozygotic twins and 238 dizygotic twins were analyzed for differences in self-reported nutritional intake, total body fat, and body mass index (BMI) using a linear regression model. The estimated values (EV) with 95% confidence intervals (95% CI) of the difference in dietary intake, total body fat, and BMI score were calculated. The monozygotic twin group and the dizygotic twin group showed similar differences in nutritional intake, DEXA fat, and BMI (all p > 0.05). The differences in nutritional intake of total calories and carbohydrates were lower in the monozygotic twin group than in the dizygotic twin group (all p < 0.05). The differences in total body fat were lower in monozygotic twins than in dizygotic twins (adjusted EV = 2427.86 g, 95% CI = 1777.19–3078.53 and adjusted EV = 1.90%, 95% CI = 1.33–2.46). Monozygotic twins had more similar dietary habits for total calories and carbohydrate intake. Other nutritional factors did not show differential similarity between monozygotic and dizygotic twins. Total body fat was more concordant in monozygotic twins.     

Genetic and environmental influences on the tracking of body size from birth to early adulthood

OBJECTIVE: This study identified genetic and environmental influences on the tracking of body size from birth to 16 to 18.5 years of age. RESEARCH METHODS AND PROCEDURES: Longitudinal information was collected from a nationally representative sample of Finnish twin adolescents (birth cohorts 1975 to 1979) and their parents through questionnaires mailed when the twins were ages 16 and 18.5 years old. The sample included 702 monozygotic, 724 same-sex dizygotic, and 762 opposite-sex dizygotic sets of twins. The measures used were length, weight, ponderal index (kilograms per cubic meters), and gestational age at birth, and height, weight, and body mass index (kilograms per square meters) at 16 to 18.5 years of age. The changes in genetic and environmental influences on body size from birth to early adulthood were analyzed by quantitative genetic modeling. RESULTS: The twins who had a higher weight or ponderal index at birth were taller and heavier in early adulthood, whereas those who were longer at birth were taller, but not heavier, later in life. Adult height was affected more by the birth size than body mass index. In the genetic modeling analyses, the genetic factors accounting for the variation of body size became more apparent with age, and both genetic and environmental influences on stature had a sizable carry-over effect from birth to late adolescence, whereas for relative weight, the influences were more age-specific. DISCUSSION: The genetic and environmental architecture of body size changes from birth to adulthood. Even in monozygotic twins who share their genetic background, the initially larger twin tended to remain larger, demonstrating the long-lasting effects of fetal environment on final body size.     

双生子学龄儿童体格发育遗传学分析

目的 分析遗传与环境因素对学龄双生子儿童体格发育的影响,分析其中年龄和性别的作用.方法测量297对6～12岁(同卵167对,同性别异卵90对,异性别异卵40对)学龄儿童身高、坐高、体重、胸围、肱三头肌皮褶、肩胛下皮褶、髂前皮褶厚度;用Mx软件拟合最佳结构方程模型.结果各体格指标均与年龄相关,仅肱三头肌皮褶厚度与性别相关;各指标的遗传模型均为ACES,遗传方差组分高于环境方差组分,男性皮褶厚度的共同环境效应高于女性,皮褶厚度的年龄方差(0.02 ～0.17)明显低于其他指标(0.35 ～0.74);校正年龄后,遗传度分别为身高(男0.80,女0.83)、坐高(男0.76,女0.79)、体重(男0.53,女0.73)、胸围(男0.72,女0.66)、肱三头肌皮褶(男0.51,女0.87)、肩胛下皮褶(男0.56,女0.86)、髂前皮褶(男0.51,女0.83),女生体重及皮褶厚度的遗传度均明显高于男生.结论遗传因素对学龄儿童体格发育起主要作用,但年龄、性别对其也有一定影响.     

遗传与环境因素对女性青春期性征发育的影响

目的探讨遗传与环境因素对女性青春期性征发育的影响,为进一步深入研究女性青春期发育提供依据。方法以学校登记为基础,募集6~18岁女性双生子180对,其中单卵双生(MZ)132对,二卵双生(DZ)48对,按Tanner标准进行青春发育分期,询问有无月经初潮及月经初潮年龄。结果乳房开始发育的年龄为9~12岁,阴毛开始发育的年龄集中在9~13岁,月经初潮年龄多集中在11~13岁。月经初潮、性征发育一致率均为MZ>DZ,月经初潮的遗传指数为0.71,乳房和阴毛发育的遗传指数分别为0.34,0.45。月经初潮年龄的组内相关系数MZ>DZ(P<0.001),偶内均方MZ相似文献   

Concordance for bulimia nervosa in twins

27 pairs of twins with bulimia nervosa according to DSM-III-R were assessed concerning concordance for bulimia nervosa and other eating disorders. There were 6 monozygotic females, 1 monozygotic male, 15 dizygotic females and 5 dizygotic twins of opposite sex. The concordance rates for bulimia nervosa (83.3 versus 26.7%) and for any eating disorder according to DSM-III-R (83.3 versus 33.3%) were significantly higher for monozygotic, as compared to dizygotic females. 27 (54%) of 50 twins had a diagnosis of depression according to ICD-9 criteria, with a small difference between monozygotic (60%) and dizygotic (53%) twins of the same sex. According to our data, monozygotic bulimic twins appear to have an increased genetic-biological vulnerability for a mental or eating disorder. Possible effects of disturbances in the process of individuation and in the development of an autonomous self due to social consequences of their physical identity with the cotwin are discussed.     

Twin study of adolescent genetic susceptibility to mosquito bites using ordinal and comparative rating data

Ordinal and comparative rating measures of mosquito attraction and mosquito bite frequency and symptoms were administered in a self-report questionnaire format to a sample of 197 monozygotic and 326 dizygotic Australian adolescent twin pairs at age 12 between 1992 and 1999, in order to investigate the environmental and possibly genetic determinants of variation between individuals. Repeat measures were obtained from the twin pairs at age 14. Ordinal variable measures, although providing some support for genetic effects on mosquito susceptibility, were affected by low repeatability. However, analysis of a comparative rating variable "compared with your twin, who is bitten by mosquitoes more often?" indicated a strong genetic influence on frequency of being bitten by mosquitoes, with no significant differences observed between males and females. Comparative rating questionnaire items are a potentially valuable tool for complementing and improving the results obtained from more conventional absolute measures.     

Plasma cholesterol variation in the National Heart, Lung and Blood Institute Twin Study

Plasma cholesterol was measured in the fifth decade of the life of 249 pairs of monozygotic (MZ) and 262 pairs of dizygotic (DZ) World War II veteran twins and 70% of the same cohort 10 years later. There were no significant differences between the mean cholesterol values for MZ and DZ twins, and the within DZ pair mean squares were significantly larger than the within MZ pair mean squares for all of the cholesterol variables measured. However, the DZ twins were found to have greater total variance, positive skewness, and leptokurtosis than the MZ twins for total and high-density lipoprotein cholesterol, and the total/high-density ratio. Comparisons with published data revealed that the variance of DZ twins was similar to that of singletons while the MZ twins have smaller total variance, perhaps owing to a missing component of variation. Hypotheses for the source of the differences in the zygosity distributions are proposed including environmental influences (pre- or post-natal and within- or among-families), genetic differences, and selection at the time of induction into the armed services. Because of the differences in total variance of the two zygosities it is difficult to know which estimates of genetic variance or heritability have the least bias. However, these data provide clues that may lead to further understanding of sources of plasma cholesterol variation that could be important to the future understanding of risk for coronary heart disease.     

A comparison of genetic and environmental variance structures for asthma, hay fever and eczema with symptoms of the same diseases: a study of Norwegian twins

BACKGROUND: We compared patterns of genetic and environmental influences on variation in liability for asthma, hay fever and eczema with those for symptoms of the same diseases, and determined how common sets of genes and environmental factors contribute to the relationship between diseases and symptoms among Norwegian twins. METHODS: Analyses were based on self-reported asthma, hay fever and eczema and symptoms of the same diseases among 3334 pairs of Norwegian twins aged 18-35 years. Structural equation modelling was conducted to estimate the genetic and environmental variance structures. RESULTS: For all diseases the concordances and the twin correlations were higher among monozygotic than among dizygotic twins. The results of the modelling confirmed that genetic effects were substantial for the diseases, and were more moderate for symptoms. The phenotypic correlation between disease and symptom was 0.67 for asthma and wheeze (a/w), 0.64 for hay fever and sneeze (hf/s), and 0.54 for eczema and itch (e/i). Decomposition of these correlations into genetic (G) and environmental (E) pathways revealed that G = 0.48 and E = 0.19 for a/w, G = 0.40 and E = 0.24 for hf/s, and G = 0.34 and E = 0.20 for e/i. For the diseases, the specific sources of genetic variance accounted for more variation than the specific environmental variance. Variance decomposition revealed that specific sources of variance were primarily explained by genetic effects for diseases and by environmental influences for symptoms. CONCLUSIONS: Genetic effects account for greater variation in reported diseases than symptoms. Co-occurrence of diseases and symptoms is mainly explained by genetic effects common to both phenotypes, but non-shared environment is also important.     

Handedness and mortality: a follow-up study of Danish twins born between 1900 and 1910

The declining prevalence of left-handed individuals with increasing age has led to two main avenues of hypotheses; the association is due either (1) to a birth cohort effect and/or an age effect caused by a switch to right-handedness with advancing age or (2) to mortality selection that reduces survival in left-handed individuals, or both. It is uncertain whether a cohort or age effect can explain the decline in age-related prevalence, and conflicting evidence exists in favor of the mortality hypothesis. We compared mortality in a subgroup of 118 opposite-handed twin pairs by counting in how many instances the right-handed twin died first. There was no evidence of differential survival between right-handed and non-right-handed individuals in the entire 1900-1910 cohort. With respect to the number of right-handed twins who died first, there was no material disadvantage among those who were not right-handed. In 60% (95% confidence interval = 49.0-71.5%) of dizygotic pairs, the right-handed twins died first. In 50% of monozygotic pairs, right-handed twins died first. The prevalence of not being right-handed was higher among males (9.2%) than females (6.5%); there was a similar frequency of non-right-handedness in monozygotic (8.0%) and dizygotic (7.8%) twins. We did not find evidence of excess mortality among non-right-handed adult twins in this follow-up study.     

Genetic and environmental influences on sleep problems: a study of preadolescent and adolescent twins

Background/Aim The aim of this study was to examine the extent to which additive genetic, shared environmental and non‐shared environmental factors contribute to adolescent and preadolescent sleep problems. Methods The sample consisted of a cohort of 270 monozygotic and 246 dizygotic twins from a university‐based twin registry. Results Results demonstrated that genetic and environmental influences each appear to be important to adolescent sleep problems. Conclusions While the magnitude of genetic influence on sleep problems was consistent with findings from the adult literature, it was smaller than in studies with younger children, suggesting genetic effects may be less influential in adolescence and adulthood.