The association between body height and coronary heart disease among Finnish twins and singletons

OBJECTIVE: An inverse association between body height and the incidence of coronary heart disease (CHD) has been observed. However, the mechanisms behind this association are still largely unknown. We will examine the role of genetic and familial factors behind the association in a large twin data set. DESIGN AND SETTING: The data were derived from the Finnish Twin cohort including 2438 singletons, 4073 monozygotic (MZ) twins, and 9202 dizygotic (DZ) twins aged 25-69 years at baseline in 1976. Incident CHD cases were derived from hospital discharge data and cause of death data between 1977 and 1995. Cox regression analysis and conditional logistic regression analysis were used. RESULTS: In population-level analyses no differences in the general risk of CHD between zygosity groups were found. The association between body height and CHD was similar between sexes and zygosity groups. When men and women in all zygosity groups were studied together an increased risk of CHD was found only among the shortest quartile (hazard ratio [HR] = 1.34, 95% CI: 1.14-1.57). Among the twin pairs discordant for CHD a suggestive increased risk for the shorter twin was seen among DZ twins (odds ratio [OR] = 1.19, 95% CI: 0.95-1.48) when men and women were studied together. CONCLUSION: An inverse association between body height and CHD was broadly similar between sexes and twin zygosity groups and was associated with short stature. Among discordant twin pairs we found a weak association among DZ twins but not MZ twins. This may suggest the role of genetic liability behind the association between body height and CHD.     

Blood pressure in relation to birth weight in twins and singleton controls matched for gestational age

Associations between adult blood pressure and birth weight were investigated in 122 same-sex twin pairs aged 18-50 years and 86 singleton controls matched according to maternal age and parity, gender, gestational age, and current age who were recruited via an obstetric database in Aberdeen, Scotland, in 1999. Twins weighed on average 425 g less than controls at birth (p < 0.001) but did not differ significantly in adult height or systolic or diastolic blood pressure from the controls. Among controls, the differences in systolic and diastolic blood pressure per kg of difference in birth weight, adjusted for gender, gestational age, current age, body mass index, smoking, physical activity level, and alcohol intake, were -4.3 (95% confidence interval (CI): -12.8, 4.3) and -6.1 (95% CI: -10.8, -1.5) mmHg/kg, respectively. In unpaired analysis among all twins, the equivalent values were -0.1 (95% CI: -4.0, 3.8) mmHg/kg for systolic pressure and -0.4 (95% CI: -2.9, 2.2) mmHg/kg for diastolic pressure, while in within-pair analysis the values were -0.9 (95% CI: -6.4, 4.6) mmHg/kg for systolic pressure and -0.2 (95% CI: -4.1, 3.7) mmHg/kg for diastolic pressure. The results suggest that in-utero growth restriction in twins is not a major determinant of their blood pressure as adults.     

The influence of birth weight and genetic factors on lipid levels: a study in adult twins

Twins can be used to investigate the biological basis for observed associations between birth weight and later disease risk, as they experience in utero growth restriction compared with singletons, which can differ in magnitude within twin pairs despite partial or total genetic identity. In the present study, sixty monozygotic and seventy-one dizygotic same-sex twin pairs aged 19-50 years and eighty-nine singleton controls matched for age, gestational age, sex, maternal age and parity were recruited from an obstetric database. Associations between fasting lipid levels and birth weight were assessed by linear regression with adjustment for possible confounding factors. Twins were significantly lighter at birth but were not significantly different in adult height, weight or lipid levels from the singleton controls. There was a significant inverse association between birth weight and both total and LDL-cholesterol levels among singleton controls (-0.53 mmol/l per kg (95 % CI -0.97, -0.09), P = 0.02 and -0.39 mmol/l per kg (95 % CI -0.76, -0.02), P = 0.04, respectively), but there was no significant association between birth weight and lipid levels in either unpaired or within-pair analysis of twins. The results suggest that the in utero growth restriction and early catch-up growth experienced by twins does not increase the risk of an atherogenic lipid profile in adult life.     

Birth weight and risk of angina pectoris: analysis in Swedish twins

Objective: Intrauterine nutrition approximated by birth weight has been shown to be inversely associated with risk of coronary heart disease (CHD). By investigating the association within twin pairs discordant for disease, the influence of genetic and early environmental factors is substantially reduced. Methods: We have investigated the association between birth weight and angina pectoris in same-sexed twins with known zygosity included in the population-based Swedish Twin Registry. Self-reports of birth weight and angina pectoris were collected in a telephone interview between 1998 and 2000. The cohort analyses were based on 4594 same-sexed twins, and the within-pair analyses included 55 dizygotic and 37 monozygotic twin pairs discordant for angina pectoris. Odds ratios (OR) and 95% confidence intervals (CI) were calculated by logistic regression. Results: Compared with birth weight between 2.0 and 2.9 kg, low birth weight (<2.0 kg) was associated with increased risk of angina pectoris in the twin cohort, (OR: 1.46; 95% CI: 1.14–1.87), but after adjustment for potential confounders the risk decreased, and did not reach significance. Within twin pairs discordant for angina pectoris, low birth weight was significantly associated with increased risk of angina pectoris within dizygotic twins (adjusted OR: 5.73; 95% CI: 1.59–20.67), but not within monozygotic twins (adjusted OR: 1.20; 95% CI: 0.40–3.58). Conclusions: The results suggest that genetic differences associated with foetal growth and adult risk of CHD may have affected previously reported associations between birth weight and CHD.     

Heritability of body size and muscle strength in young adulthood: a study of one million Swedish men

Moderate heritability for skeletal muscle strength has been reported in twin studies, but genetic co-variation between muscle strength at different parts of body and body size is not well known. Further, representativeness of twin cohorts needs to be critically evaluated. Height, weight, elbow flexion, hand grip and knee extension strength were measured in young adulthood in 1,139,963 Swedish men born between 1951 and 1976. We identified 154,970 full-brother pairs and 1582 monozygotic (MZ) and 1864 same-sex dizygotic (DZ) complete twin pairs. The data were analyzed using quantitative genetic modeling for twin and family data. Twins compared to singletons and MZ twins compared to DZ twins were shorter, lighter and had lower muscle strength. In singletons, there was more variation in weight and the strength measures compared to twins with known zygosity but not when compared to twins with unknown zygosity. Full-sib correlations for these traits were lower than DZ correlations. Additive genetic factors explained 81% of variation in height, 59% in body mass index and 50-60% in the strength measures. Additive genetic correlations varied from 0.13 between height and elbow flexion strength to 0.78 between elbow flexion and hand grip strength. Our results suggest that extra variation may exist in general populations not found in twin samples, probably because of selection due to non-participation. This may have inflated heritability estimates in previous twin studies. Nonetheless, we showed that genetic factors affect muscle strength and part of these genes are common to different strength indicators and body size.     

The relationship between maternal birthweight and gestational age in twins and singletons and those of their offspring in Norway

In order to elucidate whether maternal plurality affects offspring intrauterine growth, the relationship between birthweight and gestational age of twins and singletons and those of their first singleton liveborn children in Norway was studied using data from the Medical Birth Registry. The population-based sample consisted of 49 698 mother–offspring pairs (48 842 with singleton and 856 with twin-mothers). In bivariate analyses, no significant differences in mean birthweight and gestational age of offspring of twin and singleton mothers were found, although the mean birthweight and gestational age of the twin-mothers themselves were significantly lower than those of singletons (819 g and 14 days respectively). In multiple regression analysis, the expected birthweight of offspring was 230.3 g (95% CI: 193.2–267.4 g) higher when the mother was a twin than when the mother was a singleton, when controlling for non-standardised maternal birthweight. When adjusting for relative maternal birthweight ( z -score), the association between maternal plurality and offspring birthweight was not statistically significant. The results suggest that being born as a twin has no substantial consequences on offspring growth in utero and show that mean differences in birthweight between twins and singletons should be standardised when both groups are included in multivariate studies.     

Birthweight, childhood growth, and blood pressure at 43 years in a British birth cohort

BACKGROUND: Low birthweight is associated with high blood pressure in later life, but it is unclear whether the association is confounded with or modified by maternal and socioeconomic factors or childhood growth. METHODS: A total of 3157 men and women from a British birth cohort study where the survey members have been followed up regularly since their birth in 1946 were included in analyses. The associations between birthweight, childhood growth and blood pressure at 43 years of age were assessed using multiple regression models. RESULTS: Systolic blood pressure (SBP) decreased by 2.3 mmHg (95% CI: 0.8, 3.5) for men and 1.8 mmHg (95% CI: 0.1, 3.5) for women per 1-kg increase in birthweight. The effect was stronger in first born or those born to younger mothers. There was no confounding with any maternal, socioeconomic, or childhood growth variable. SBP increased by 1.45 mmHg (95% CI: 0.11, 2.78) in women and 0.46 mmHg (95% CI: -0.70, 1.62) in men per standard deviation of body mass index (BMI) change between ages 7 and 15 years. Among women this effect was not completely accounted for by adult size and was independent of birthweight. CONCLUSIONS: The determinants of birthweight, possibly related to maternal health during pregnancy, may impact on the relationship with SBP in middle life. The importance of tackling the increasing levels of childhood obesity seen in later cohorts is highlighted by the detrimental impact on SBP of large increases in BMI during adolescence.     

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.     

Major genetic susceptibility for venous thromboembolism in men: a study of Danish twins

BACKGROUND: Although several genetic determinants (mutations or polymorphisms) have been associated with increased risk of venous thromboembolism, the overall influence of genetic factors on this disease is unknown. METHODS: We linked the Danish Twin Registry, which includes twins born 1870-1953, with the Danish National Registry of Patients, comprising all hospitalizations in Denmark since 1977. We then determined the risk of venous thromboembolism as determined from discharge diagnosis. RESULTS: We identified 26,982 twins who were alive on 1 January 1977, and computed measures of familial and genetic association of venous thrombotic disorders. Individuals were classified according to zygosity and hospitalization with venous thromboembolism. Since 1977, 678 twins were hospitalized with an episode of venous thromboembolism. Of these, only 545 pairs (281 male pairs and 264 female pairs) were alive in 1977. For men, the concordance rates for mono- and dizygotic twin pairs, respectively, were 0.22 (95% confidence interval = 0.14 to 0.30) and 0.08 (0.04-0.12). The odds ratio (interpreted as the relative risk of venous thromboembolism for one twin, given venous thromboembolism in the partner twin) was 13.5 (7.3-24.8) among monozygotic twins and 3.8 (1.8-8.3) among dizygotic twins. The respective correlations for venous thromboembolism were 0.55 (0.38-0.70) and 0.26 (0.09-0.42). The proportion of the variance attributable to genetic effects on venous thromboembolism in males was 55% (39%-68%). The remaining variation could be attributed to men's nonfamilial environments. In contrast, for women there was no intra-twin pair similarity for venous thromboembolism. CONCLUSIONS: We found differences in genetic susceptibility to venous thromboembolism between the sexes, with genetic factors playing a substantially stronger role in males than in females.     

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.     

Do genetic factors contribute to the association between birth weight and blood pressure?

OBJECTIVES: To evaluate whether genetic factors contribute to the association between low birth weight and increased blood pressure among adolescents. DESIGN: Historical cohort study of twin pairs. It was evaluated whether (1) a negative association between birth weight and systolic blood pressure was found in the overall twin sample and (2) whether the intrapair difference in birth weight correlated with the intrapair difference in systolic blood pressure-thereby controlling for the effect of genetic factors (all in monozygotic and on average half in dizygotic pairs). SETTING: The Minnesota Twin Family Study. PARTICIPANTS: 1311 pairs of adolescent twins. MAIN RESULTS: A negative association between birth weight and systolic blood pressure was retrieved in the overall sample. The regression coefficient after controlling for current weight was -1.88 mm Hg/kg (SE 0.61), which corresponds to results from previous studies of singleton adolescents. The regression coefficient fell to -0.64 mm Hg/kg (SE 0.86) when the intrapair analyses were used. The largest reduction was observed among monozygotic twins: from -2.44 mm Hg/kg (SE 0.75) in the overall monozygotic twin sample to -1.06 mm Hg/kg (SE 1.14) in the analyses of the within monozygotic pair differences. CONCLUSION: The association between low birth weight and increased blood pressure later in life is well established. "The fetal programming hypothesis" suggests that the association is caused by intrauterine malnutrition while a new hypothesis "the fetal insulin hypothesis" proposes that genetically determined insulin resistance also contributes significantly to the association. A recent twin study of middle aged twins showed no evidence for an influence of genetic factors while this larger study provides support for the fetal insulin hypothesis: the association between birth weight and blood pressure attenuated among adolescents when genetic factors were controlled. Together this suggests an important contribution of genetic factors to the association between fetal growth and systolic blood pressure in adolescence.     

济宁市6～14岁双生子血铅水平调查及遗传度分析

目的 了解济宁市双生子血铅水平,探讨遗传因素和环境因素对儿童血铅水平的影响.方法 于2008年6月,随机抽取济宁市144对同性别6～14岁双生子作为研究对象,测定其血铅含量并进行评价[分为相对安全(血铅＜60μg/L)、超标(60μg/L≤血铅＜100μg/L)、铅中毒(血铅≥100μg/L)].在DNA卵型鉴定基础上计算血铅的遗传度.结果 经卵型鉴定,144对双生子中同卵双生子76对,异卵双生子68对;血铅含量相对安全的占62.50%,超标的占23.61%,铅中毒的为13.89%,三者在性别间分布差异无统计学意义(X~2=4.077,P=0.130).双生子血铅含量为(58.80±40.30)μg/L,不同性别、年龄间差异无统计学意义(t_(性别)=0.17,P=0.87;F_(年龄)=1.37,P=0.21).儿童铅中毒发生率和血铅含量在9～11岁均出现突增现象,9～10岁女童高于男童,但差异均无统计学意义(P＞0.05).经遗传度分析,血铅含量的遗传度为9.19%.结论 影响血铅含量的遗传因素作用远小于环境因素作用.     

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.     

Perinatal characteristics and risk of polio among Swedish twins

Perng W, Cnattingius S, Iliadou A, Villamor E. Perinatal characteristics and risk of polio among Swedish twins. Paediatric and Perinatal Epidemiology 2012; 26: 218–225. Prenatal exposure to adverse environmental conditions is related to increased adult mortality in regions where infections are highly prevalent, yet there is little evidence of the impact of perinatal conditions on the risk of severe infections throughout life. Using prospectively collected data from 21 604 like‐sexed Swedish twins of known zygosity born in 1926–1958, we examined the risk of polio in relation to perinatal characteristics using cohort and nested co‐twin case–control analyses. Polio incidence was determined through an interview in 1998, and linkage with the Swedish national inpatient and death registries. There were 133 cases of polio. In the cohort analysis, birth length, birthweight and head circumference were positively associated with polio risk. After adjustment for sex, birth year, gestational age at birth and within‐twin pair correlations, twins of shortest length (<44 cm) had a 67% ([95% CI: 6%, 88%]; P = 0.04) lower risk of polio compared with the reference group (47–49 cm). After additional adjustment for birth length, every 100‐g increase in birthweight was related to a 34% increased risk of polio ([95% CI: ?1%, 82%]; P = 0.06), and every 10‐mm increase in head circumference was related to a 17% greater risk of polio ([95% CI: 5%, 31%]; P = 0.004). In co‐twin control analyses among 226 disease‐discordant twins, birth length, birthweight and head circumference were 0.3 cm (P = 0.19), 84 g (P = 0.07) and 3 mm (P = 0.08) higher in cases than controls, respectively. Similar associations were observed among monozygotic (n = 84) and dizygotic (n = 142) twins. These findings suggest that early intrauterine growth restriction may be inversely related to the incidence of polio.     

Birthweight and perinatal mortality among singletons and twins in north-eastern Tanzania

BACKGROUND: Low birthweights as well as high perinatal mortality rates are common in most African populations. Little is known, however, about how low birthweight corresponds with higher mortality rates within African populations. Twins are known to have lower birthweights and higher perinatal mortality rates than singletons. If lower birthweights represent higher perinatal risk per se, small twins within a population with generally lower birthweights should have critically increased risks. METHODS: In total, 15,255 births in a Tanzanian hospital during 1999-2006 were analysed to determine birthweight distribution and examine perinatal mortality rates (including stillbirths and neonatal deaths within 24 hours) by birthweight in twins and singletons. Referral births from outside the district where the hospital was situated were excluded from analysis. RESULTS: The mean birthweight for births within an estimated normal distribution was 3172 g, with a standard deviation of 462 g. The overall perinatal mortality rate was 43.9 per 1000 births (95% confidence interval: 40.7-47.2). Perinatal mortality rates among twins and singletons were 91.0 and 41.1 per 1000 babies respectively, corresponding to a relative risk of 2.2 (95% confidence interval: 1.7-2.8). The birthweight distribution for twins was shifted to lower birthweights. Twins had a generally lower birthweight and an excess of extremely small births as compared to singletons. The increased mortality rate for twins appeared to be independent of birthweight. CONCLUSIONS: The two-fold increased risk of perinatal death for twins was observed across the whole birthweight distribution, and very small twins appeared to have an excess perinatal risk that was almost similar to that of larger twins.     

Maternal birthweight and outcome of twin pregnancy

There is evidence from singletons that maternal birthweight is positively related to offspring gestational length and birthweight, and some evidence of an inverse relationship with preterm birth. Among twins very preterm birth is the major cause of neonatal mortality and of immediate and later morbidity, including neurodevelopmental impairment. We hypothesised that the relationship between maternal birthweight and gestational length would be more evident in twin than in singleton pregnancies, as there is more variation in gestation in the former. Among 131 singleton mothers carrying twins, there was weak evidence of a positive relationship between maternal birthweight and twin gestational length (+0.6 weeks [95% CI -0.05, +1.3] per kg increase in maternal birthweight, but stronger evidence among 56 of these who went into labour spontaneously (+1.9 weeks [+0.7, +3.1], P = 0.003 for interaction). In the latter group we estimated that the odds of very preterm birth (at <32 weeks) were reduced by 50% [95% CI 10%, 82%] per 250 g increase in maternal birthweight. In the whole cohort, and in this subgroup, maternal birthweight was strongly positively related to both twin offspring total birthweight and total placental weight. Our data, consistent with intergenerational programming of early development, suggest the possibility of a stronger and more clinically relevant association among twins than among singletons. Nevertheless, our sample size was modest and this finding needs to be confirmed in a larger cohort.     

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.     

女性出生体重与成年期高血压的关联及代际关联研究

目的 分析女性出生体重与成年期血压水平及高血压患病的关联,探讨出生体重及高血压的代际关联。方法 2012年11月～2016年12月期间在上海闵行区11 660名有直系血缘关系的2~4代女性中进行了横断面调查,收集人口学特征、出生信息、生活方式及疾病史等数据。对20岁及以上研究对象行身高、体重、腰臀围、血压测量。采用线性、非线性回归和通径分析方法进行数据分析。结果 出生体重每增加1.0 kg,成年期收缩压、舒张压和脉压分别变化-0.2（95%CI：-0.6～0.7）、-0.3（95%CI：-0.6～0.2）和0.3（95%CI-0.2～0.8）mm Hg（均有P<0.05）。出生体重与成年后高血压患病风险关联差异无统计学意义（OR=0.9,95%CI：0.7～1.0,P=0.140）。与出生体重2.5～kg的女性相比,调整年龄等混杂因素后,出生体重<2.5,3.0~,3.5~kg及≥4.0 kg的女性成年后患高血压的OR（95%CI）值分别为0.8（0.5～1.2）、1.0（0.9～1.2）、0.8（0.6～1.0）和0.7（0.4～1.2）。通径分析结果显示,母女两代人群的出生体重、血压水平及高血压患病状况均相关（均有P<0.05）,但未见母亲出生体重对女儿血压水平影响。结论 女性出生体重与成年期血压水平及高血压患病风险无显著的代际关联。     

Familial patterns of covariation for cardiovascular risk factors in adults: The Victorian Family Heart Study

The Victorian Family Heart Study was established to address the causes of familial patterns in cardiovascular risk factors. From 1990 to 1996, a representative population sample of 783 adult families (2,959 individuals), each comprising both parents (40-70 years) and at least one natural adult offspring (18-30 years), was recruited in Melbourne, Australia. Included in both generations were 461 monozygotic and dizygotic twins as pairs or singletons. A multivariate normal model was used for pedigree analysis of height, weight, body mass index, diastolic and systolic blood pressure, pulse rate, and total and high density lipoprotein cholesterol. All traits showed evidence for additive genetic variation, explaining from 55% (height) to 26% (pulse) of age- and sex-adjusted variance. An effect persisting into adulthood of shared family environment during cohabitation explained from 39% (body mass index) to 13% (systolic blood pressure) of variance (not nominally significant for diastolic blood pressure). These shared environmental effects were strongest within twin pairs, less so for sibling pairs, and least for parent-offspring pairs (in which an effect was not observed for weight, diastolic and systolic blood pressure, and total cholesterol). On a background of genetic influences, there are periods in early life during which the family environment cements long-term correlations between adult relatives in cardiovascular risk factors.