Determinants of blood pressure in Japanese-American Families

Genetic and environmental influences on blood pressure in an urban Indian population

Aggarwal Baniyas were found to have a high prevalence of high blood pressure. Genetic and environmental influences may be implicated for this risk factor of cardiovascular disease. The aim of this study was to investigate the potential for common genetic and environmental influences on blood pressure measures (systolic and diastolic blood pressure (SBP, DBP)). The population-based sample was comprised of 309 Aggarwal Baniya families, including 1214 individuals (271 fathers, 307 mothers, 311 sons and 325 daughters) from New Delhi, India. The prevalence of obesity in this community was found to be high (BMI: fathers, 26.1 kg/m2; mothers, 29.4 kg/m2; sons, 16.9-22.4 kg/m2; and daughters, 16.3-22.7 kg/m2). Correlation and heritability were estimated. Most sibling-sibling correlations were larger than the parent-offspring correlations, and all parent-offspring and sibling-sibling correlations were larger than the corresponding spouse correlation (SBP=0.026; DBP=0.029). The maximum heritability was estimated as 44.6% for SBP and 62.8% for DBP. The lack of a significant spouse correlation is consistent with little or no influence of the common familial environment. However, the high heritability estimate for both SBP and DBPs reinforces the importance of the non-shared environmental effect.

Nutrient and food intakes of middle-aged adults at low risk of cardiovascular disease: the international study of macro-/micronutrients and blood pressure (INTERMAP)

PURPOSE

Individuals with favorable levels of readily measured cardiovascular disease (CVD) risk factors (low risk, LR) experience low long-term rates of CVD mortality and greater longevity. The purpose of the current study was to compare nutrient/food intakes of LR participants with participants not LR in the INTERMAP study.

METHODS

Men and women (40-59 years) from 17 population samples in four countries (China, Japan, UK, US) provided four 24-h dietary recalls and two timed 24-h urine collections. LR was defined as meeting all of the following CVD risk criteria: systolic/diastolic blood pressure (BP) ≤ 120/ ≤ 80 mmHg; no drug treatment for high BP, hyperlipidemia, or CVD; non-smoking; BMI <25.0 kg/m(2) (US, UK) or <23.0 kg/m(2) (China, Japan); alcohol consumption <26.0 g/day (men)/<13.0 g/day (women); and no history of diabetes or CVD. Multivariate logistic regression was used to examine associations of nutrient/food intakes with LR.

RESULTS

LR individuals reported higher intake of vegetable protein, fiber, magnesium, non-heme iron, potassium; lower energy intake; lower intake of cholesterol, saturated fatty acids, animal protein; and lower 24-h urinary sodium compared with individuals not LR. With regard to foods, LR individuals reported higher intake of fruits, vegetables, grains, pasta/rice, fish; lower intakes of meats, processed meats, high-fat dairy, and sugar-sweetened beverages than individuals not LR.

CONCLUSIONS

Lower energy intake and differential intake of multiple specific nutrients and foods are characteristic of individuals at low risk for developing CVD. Identification of dietary habits associated with LR is important for further development of public health efforts aimed at reduction/prevention of CVD.

Novel quantitative trait locus is mapped to chromosome 12p11 for left ventricular mass in Dominican families: the Family Study of Stroke Risk and Carotid Atherosclerosis

Background

Left ventricular mass (LVM) is an important risk factor for stroke and vascular disease. The genetic basis of LVM is unclear although a high heritability has been suggested. We sought to map quantitative trait loci (QTL) for LVM using large Dominican families.

Methods

Probands were selected from Dominican subjects of the population-based Northern Manhattan Study (NOMAS). LVM was measured by transthoracic echocardiography. A set of 405 microsatellite markers was used to screen the whole genome among 1360 subjects from 100 Dominican families who had complete phenotype data and DNA available. A polygenic covariate screening was run to identify the significant covariates. Variance components analysis was used to estimate heritability and to detect evidence for linkage, after adjusting for significant risk factors. Ordered-subset Analysis (OSA) was conducted to identify a more homogeneous subset for stratification analysis.

Results

LVM had a heritability of 0.58 in the studied population (p < 0.0001). The most significant evidence for linkage was found at chromosome 12p11 (MLOD = 3.11, empirical p = 0.0003) with peak marker at D12S1042. This linkage was significantly increased in a subset of families with the high average waist circumference (MLOD = 4.45, p = 0.0045 for increase in evidence for linkage).

Conclusion

We mapped a novel QTL near D12S1042 for LVM in Dominicans. Enhanced linkage evidence in families with larger waist circumference suggests that gene(s) residing within the QTL interact(s) with abdominal obesity to contribute to phenotypic variation of LVM. Suggestive evidence for linkage (LOD = 1.99) has been reported at the same peak marker for left ventricular geometry in a White population from the HyperGEN study, underscoring the importance of this QTL for left ventricular phenotype. Further fine mapping and validation studies are warranted to identify the underpinning genes.

Maximum-likelihood generalized heritability estimate for blood pressure in Nigerian families

Elevated blood pressure (BP) is more common in relatives of hypertensives than in relatives of normotensives, indicating familial resemblance of the BP phenotypes. Most published studies have been conducted in westernized societies. To assess the ability to generalize these estimates, we examined familial patterns of BP in a population-based sample of 510 nuclear families, including 1552 individuals (320 fathers, 370 mothers, 475 sons, and 387 daughters) from Ibadan, Nigeria. The prevalence of obesity in this community is low (body mass index: fathers, 21.6; mothers, 23.6; sons, 19.2; and daughters=21.0 kg/m2). The BP phenotype used in all analyses was created from the best regression model by standardizing the age-adjusted systolic blood pressure (SBP) and diastolic blood pressure (DBP) to 0 mean and unit variance. Heritability was estimated by use of the computer program SEGPATH from the most parsimonious model of "no spouse and neither gender nor generation difference" as 45% for SBP and 43% for DBP. The lack of a significant spouse correlation is consistent with little or no influence of the common familial environment. However, the heritability estimate of <50% for both SBP and DBPs reinforces the importance of the nonshared environmental effect.

Physiological variation and adaptability in human populations

This review traces some of the developments in population physiology based on contributions to the Annals over the last 25 years. Two broad themes are evident, physiological systems variation and adaptation, and by way of introduction an historical perspective of their relationship within human ecology is explored. Studies of physical fitness and work capacity, and the efforts to create standardized field procedures make up a number of the early papers. Longitudinal studies have provided reliable reference standards for Westernized populations, but are virtually non-existent for primitive groups. The relative importance of phenotypic and genotypic variations in working capacity have yet to be clearly defined. The level of habitual activity during childhood contributes to the development of ventilatory capacity though constitutional influences are of major importance. Variability in strength and motor performance of skeletal muscles are shown to have a direct bearing on aspects of growth, development and biological maturation. Physical and psychological stress in communities have been investigated. These and other studies contribute valuable data on the issue of stress, hypertension and cardiovascular morbidity and mortality. On the theme of human adaptability, high altitude populations, variations in thermal tolerance and adaptations in ageing populations have all received recent investigation. Highland people of all ages have considerably larger lung volumes than coastal dwellers. Haematological, biochemical and pulmonary function show adaptive phenomena that vary in different highland groups. In the tropical biome, more recent work includes the functional consequences of malnutrition, ethnic and cultural differences in work capacity, and the effects of endemic disease on physical performance. Annals of Human Biology papers have more recently contributed to investigations on morphological and physiological changes with human ageing. Though there is a decline in the ability to adapt to environmental stresses with age this may be met by changes in adaptational strategy in physiological systems.

Genetic and environmental contributions to cardiovascular risk factors in Mexican Americans. The San Antonio Family Heart Study

BACKGROUND

The familial aggregation of coronary heart disease can be in large part accounted for by a clustering of cardiovascular disease risk factors. To elucidate the determinants of cardiovascular disease, many epidemiological studies have focused on the behavioral and lifestyle determinants of these risk factors, whereas others have examined whether specific candidate genes influence quantitative variation in these phenotypes.

METHODS AND RESULTS

Among Mexican Americans from San Antonio (Tex), we quantified the relative contributions of both genetic and environmental influences to a large panel of cardiovascular risk factors, including serum levels of lipids, lipoproteins, glucose, hormones, adiposity, and blood pressure. Members of 42 extended families were studied, including 1236 first-, second-, and third-degree relatives of randomly ascertained probands and their spouses. In addition to the phenotypic assessments, information was obtained regarding usual dietary and physical activity patterns, medication use, smoking habits, alcohol consumption, and other lifestyle behaviors and medical factors. Maximum likelihood methods were used to partition the variance of each phenotype into components attributable to the measured covariates, additive genetic effects (heritability), household effects, and an unmeasured environmental residual. For the lipid and lipoprotein phenotypes, age, gender, and other environmental covariates accounted in general for < 15% of the total phenotypic variance, whereas genes accounted for 30% to 45% of the phenotypic variation. Similarly, genes accounted for 15% to 30% of the phenotypic variation in measures of glucose, hormones, adiposity, and blood pressure.

CONCLUSIONS

These results highlight the importance of considering genetic factors in studies of risk factors for cardiovascular disease.

Chromogranin A in human hypertension. Influence of heredity

Multiple heritable traits are associated with essential (genetic) hypertension in humans. Because chromogranin A is increased in both human and rodent genetic hypertension, we examined the influence of heredity and blood pressure on chromogranin A in humans. In estimates derived from among- and within-pair variance in monozygotic versus dizygotic twins, plasma chromogranin A displayed significant (F15,18 = 2.93, P = .016) genetic variance (sigma 2 g), and its broad-sense heritability was high (h2B = 0.983). Plasma chromogranin A was increased in essential hypertension (99.9 +/- 6.7 versus 62.8 +/- 4.7 ng/mL, P < .001) but was influenced little by genetic risk for (family history of) hypertension (in normotensive or hypertensive subjects), by race, or by several antihypertensive therapies (angiotensin-converting enzyme inhibitor, diuretic, or beta-adrenergic antagonist). In normotensive subjects at genetic risk for essential hypertension, neither basal nor sympathoadrenal stress-evoked chromogranin A differed from values found in subjects not at risk. In established essential hypertension, plasma chromogranin A responses to adrenal medullary (insulin-evoked hypoglycemia) or sympathetic neuronal (dynamic exercise) activation were exaggerated, whereas responses to sympathoadrenal suppression (ganglionic blockade) were diminished, suggesting increased vesicular stores of chromogranin A and an adrenergic origin of the augmented chromogranin A expression in this disorder. We conclude that plasma chromogranin A displays substantial heritability and is increased in established essential hypertension. Its elevation in established hypertension is associated with evidence of increased vesicular stores of the protein and with adrenergic hyperactivity but is influenced little by customary antihypertensive therapies. However, the chromogranin A elevation is not evident early in the course of genetic hypertension.

Haplotype analysis of CYP11B2

Polymorphisms affecting the synthesis of aldosterone or its regulation may have effects on blood pressure. For example, an autosomal dominant form of human hypertension, glucocorticoid suppressible hyperaldosteronism, is caused by recombination between the genes for aldosterone synthase (CYP11B2) and steroid 11 beta-hydroxylase (CYP11B1), creating a chimeric gene in which the CYP11B1 promoter and CYP11B2-specific coding sequences are juxtaposed. Thus, aldosterone synthesis is improperly regulated. We have begun an analysis of the human CYP11B2 and CYP11B1 genes to see if frequent polymorphisms exist and if they are correlated with differences in blood pressure. We have found frequent polymorphisms in CYP11B2. One in the promoter influences binding of the transcriptional regulatory protein, SF-1. Another is a gene conversion in intron 2 so that most of the intron has a sequence corresponding to CYP11B1. These polymorphisms are in linkage disequilibrium, defining 3 haplotypes. Blacks and whites differ significantly (p < 0.001) in the frequency with which these haplotypes occur. Further studies are required to determine if the observed differences between blacks and whites in blood pressure and in aldosterone levels can be explained in part by these allelic differences in CYP11B2 or by other polymorphisms in linkage disequilibrium on these haplotypes.

Genetic and environmental effects on coronary heart disease risk factors in northern Norway. The cardiovascular disease study in Finnmark

This study comprised 1377 first degree relatives in 575 families ascertained through a comprehensive screening of the general population from 20 to 52 years of age. Path analysis using parsimonious models gave evidence of significant biologic and environmental transmission for total cholesterol (genetic and cultural heritabilities were 0.46 and 0.05, respectively), high density lipoprotein cholesterol (0.42, 0.10), triglycerides (0.21, 0.07), and systolic (0.48, 0.04) and diastolic (0.35, 0.05) blood pressure. Compared with other studies employing the same path analytic model, heritability estimates in general were among the highest reported, except for the somewhat lower genetic component in total cholesterol and triglycerides. For the first time in a single sample from the general population, lipid and blood pressure variables were investigated applying the same methodology, and good agreement was illustrated by the result that identical parsimonious models were reached for all phenotypes, with the exception of a single additional parameter for total cholesterol. About one fourth to one half of the total phenotypic variance could be ascribed to genetic sources, whereas the contribution from shared familial environment was much smaller.

Age-specific genetic effects for blood pressure

Correlations between relatives were determined for systolic and diastolic blood pressure. The correlations decrease as age differences between relatives increase in a Norwegian sample with 43,751 parent-offspring pairs, 19,140 pairs of siblings, and 169 pairs of twins. A simple biometric model specifying only age-specific genetic additive effects and environmental effects fitted well to correlations between cotwins, pairs of siblings, and parent-offspring dyads in subsets of relatives grouped by age differences. None of the environmental effects appeared to be due to environmental factors that are shared by family members. Models that excluded a parameter for the age-specific genetic influence did not fit the data. The results may partly explain what seems to be a discrepancy between relatively low parent-offspring correlations from previous nuclear family studies and high correlations from twin studies, especially in identical twins.

Segregation analysis of diastolic blood pressure in a large pedigree

Hypertension, a major risk factor for cardiovascular diseases, is thought to be inherited to some extent. However, the nature of its genetic component remains unresolved. In the present study, data from a single large kindred (the HGAR1 pedigree) were used to search for evidence of single gene and multifactorial effects on diastolic blood pressure. Commingling analyses found that a mixture of three distributions fit the data significantly better than a single normal distribution, suggesting a major effect influencing diastolic blood pressure levels. However, segregation analysis, using regressive models, indicated that the transmission probabilities were not consistent with Mendelian expectations. There was no evidence of either major gene or polygenic effects on diastolic blood pressure levels in this family.

Non-modulation as an intermediate phenotype in essential hypertension

Non-modulation is a trait characterized by abnormal angiotensin-mediated control of aldosterone release and the renal blood supply. To determine whether non-modulation defines a specific subgroup of the hypertensive population and its utility as an intermediate phenotype, we have studied the distribution of this quantitative trait, whether its features are reproducible on repeated testing, and whether there is concordance of its multiple features. Essential hypertensive patients (224) and normotensive subjects (119) received an infusion of angiotensin II (Ang II) at 3 ng.kg-1.min-1 for 30-45 minutes. p-Aminohippurate (PAH) clearance was assessed as an index of renal plasma flow while the subjects were on a 200 meq sodium diet; plasma aldosterone levels were measured while the subjects were on a 10 meq sodium diet. In 54 subjects, diuretic-induced volume depletion superimposed on a low salt diet was substituted for the Ang II infusion. The results of each study were submitted to maximum likelihood analysis to assess bimodality. In response to both diuretic-induced volume depletion (p < 0.000023) and Ang II infusion (p < 0.0009), aldosterone responses were bimodally distributed in the essential hypertensive but not in the normotensive subjects, suggesting that this trait identifies a discrete subgroup. In the 59 subjects who had both an adrenal and renal study, 50 (85%) were concordant. Finally, in 27 subjects studied two to six times over a span of 1-60 months, the intraclass correlations of the adrenal, PAH, or both responses were highly significant (p values between 0.001 and 0.00007), indicating high reproducibility of results on repeated testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic and environmental effects on blood pressure in a Norwegian sample

Systolic (SBP) and diastolic (DBP) blood pressures were measured in a health screening of the adult population in Nord-Trøndelag, Norway. Correlations were computed for 23,936 pairs of spouses, 43,586 pairs of parent and offspring, 19,151 pairs of siblings, 1,251 pairs of grandparents-grandchildren, 1,146 pairs of biological uncles/aunts-nephews/nieces (avuncular), 801 non-biological avuncular pairs, 169 pairs of same-sex twins, and smaller groups of other types of relationships. Spouse correlations of 0.08 and 0.09 were approximately constant or slightly decreasing with marital duration. The correlation values for SBP and DBP were approximately 0.16 for parents-offspring, 0.19 to 0.23 for same-sex siblings with similar values for DZ twins, 0.19 and 0.16 for opposite-sex siblings, 0.52 and 0.43 for MZ twins, and close to zero for most of the second-order relationships. Genetic additive variance was estimated at 0.29 and genetic dominance variance at 0.18 with the best model for SBP. The corresponding estimates from the best models for DBP were 0.29 or lower and 0.22 or lower, the sum not exceeding 0.35. There was evidence of a moderate effect of environmental factors shared by same-sex siblings and twins (for DBP), but no cultural transmission, and whether or not adult relatives live together does not affect familial resemblance for BP. The data did not permit a very precise resolution of the relative magnitude of genetic dominance and sibling effects. The correlation structure did not show sex-specific genetic effects.

Pathogenesis of the essential hypertensions

The pathogenesis of essential hypertension (EH) is reviewed with a special focus on the development phase or the pre-hypertensive period. Three animal models are presented: the spontaneously hypertensive rat, the Dahl's salt-sensitive rat, and the Milan hypertensive rat. Some of the findings in animal models have inspired new fields and technical approaches for studying EH in man. From the original idea of Page, a new mosaic of various etiological parameters serves as a basis for reviewing the multiple facets of EH in man. One must conclude that EH is heterogeneous disease and most likely every single hypertensive patient belongs to a subgroup of the whole population of hypertensives.

Ambulatory blood pressure monitoring: assessing the diurnal variation of blood pressure

The purposes of this paper are to examine the effects of activity, situation of measurement, mood, and occupation on the daily variation of blood pressure and to discuss the potential utility of ambulatory blood pressure monitoring in physical anthropological studies. The subjects of the blood pressure variability study are 125 men who were referred to the Hypertension Center at New York Hospital--Cornell Medical Center for evaluation of hypertension. There were 1,386 blood pressure measurements from these subjects available for study, which were taken using noninvasive ambulatory blood pressure monitoring techniques. Pressures were transformed to z scores using the subject's daily mean pressure and standard deviation to assess the relative elevation during the experience of the various factors. The results show that activity and mood are the most significant sources of blood pressure variation (P less than .005) and are additive. Occupation, which may be an indicator of social class in this population, also modified the mood effects. Because ambulatory blood pressure monitors obtain many readings over a day under a variety of circumstances, their use can improve epidemiological and human biological studies of the inheritance and variability of blood pressure. Ambulatory blood pressure monitoring is an important new tool in the study of human biological variation.

Genetic and nongenetic determinants of blood pressure in a southern Brazilian sample

A probabilistic sample representative of the adult population of Rio Grande do Sul, Brazil, was studied to estimate the genetic and nongenetic determinants of blood pressure. Four thousand five hundred and sixty-five individuals, 20 to 74 years old, from 2050 households, were examined. The genetic determination of the SBP (systolic blood pressure) and DBP (diastolic blood pressure) was evaluated in 557 families extracted from this sample. The analysis was performed first with no adjustments for other influencing factors, and then adjusting for the effects of the two significant covariates, age and Quetelet's index, identified through a multiple stepwise regression analysis with nine independent variables. Higher heritability estimates were obtained for DBP (raw data: 0.40; residuals: 0.45) than for SBP (raw data: 0.22; residuals: 0.26). The significant correlation coefficients varied from 0.13 (for father-offspring raw data, total sample), to 0.36 (for siblings, adjusted data, untreated sample). Slight differences were observed between the total and pharmacologically untreated samples in relation to correlation and heritability estimates.

Genetic epidemiological study of blood pressure in a sedentary rural agricultural population of West Bengal, India

To study the genetic epidemiology of blood pressure (BP), data on 78 families were collected from a sedentary agricultural population of eastern India. The general levels of both systolic (SBP) and diastolic (DBP) blood pressures are found to be low (mean SBP = 106.41 mm Hg; mean DBP = 63.94 mm Hg). Trends of blood pressures with age are similar to those reported earlier (e.g., in the Framingham study). Environmental variables--e.g., occupation and tobacco use--do not have any direct significant effect on blood pressure variability in this population. Path analysis of family data shows a highly significant familial aggregation and yields a genetic heritability (maximum) estimate of 0.3 for both SBP and DBP. Sib-sib and mother-child correlation estimates are, respectively, 0.3 and 0.25. Father-child correlation estimates are 0.13 for SBP and near zero for DBP. A pseudopolygenic model yields the best fit to the data on SBP, while for DBP a proper resolution of various models considered could not be obtained.

Essential hypertension and histocompatibility antigens. A linkage study

It is well established that genetic and environmental factors are involved in the etiology of essential hypertension. The presence of genes predisposing to essential hypertension in the human leukocyte antigen (HLA) complex is controversial because studies of an association between HLA antigens and essential hypertension have failed to yield consistent results. Our aim in the present study was to further investigate this issue through the method of linkage analysis. Analysis of 96 hypertensive siblings distributed in 31 families indicated a significant distortion (p = 0.0009) of the normal segregation pattern of inheritance of HLA haplotypes. Thus, our data indicate that at least one of the genes responsible for genetic predisposition to essential hypertension is located very near or within the HLA complex.

Evidence for heritability of non-modulating essential hypertension

We have previously described a subset of subjects with essential hypertension who fail to appropriately modulate renal vascular and adrenal reactivity with changes in dietary sodium and in response to infused angiotensin II (Ang II). In this paper, we studied these responses in 13 unselected hypertensive subjects in whom the family history of hypertension had been carefully detailed. Nine of these 13 subjects had a positive family history (FH+) for hypertension and had significantly smaller decrements in renal blood flow with Ang II infusion than the four subjects who had a negative family history (FH-) (-84 +/- 16 ml/min/1.73 m2 for FH+ vs. -149 ml/min/1.73 m2 for FH-, p = 0.024). These FH+ subjects also showed smaller increases in renal blood flow with increases in dietary sodium than FH- subjects (7 +/- 10 ml/min/1.73 m2 vs. 72 +/- 24 ml/min/1.73 m2, respectively; p = 0.014). When classified as modulators or non-modulators by previously established criteria, all seven non-modulators were FH+, and seven of nine FH+ subjects were non-modulators. This association between non-modulation and family history of hypertension is significant (p = 0.021). To further clarify the association between non-modulation and family history of hypertension, we have studied the renal blood flow response to Ang II in 31 hypertensive siblings from 14 sibships. Twenty-five of these 31 subjects (81%) behaved as non-modulators (p = 0.008 compared with expected value in an unselected hypertensive population). Additionally, strong concordance of non-modulation between sibling pairs was observed (p = 0.004).(ABSTRACT TRUNCATED AT 250 WORDS)

Family resemblance in blood pressure measurements

The correlation for diastolic and systolic blood pressure was studied in two samples of quartets each consisting of two pairs. The first sample comprised pairs of sisters and their husbands, and the second sample was comprised of brothers and their wives. All siblings were between 30 and 55 years of age and had been married for at least 5 years. It was found that unrelated men married to sisters had a significant correlation in both diastolic (r = 0.28) and systolic (r = 0.41) pressure. For systolic blood pressure, the correlation between pairs of unrelated men married to sisters was significantly larger than the homologous correlation existing in pairs of brothers married to unrelated women. The correlations of systolic and diastolic pressure in sisters were significantly smaller than the same correlations measured in the wives of brothers. The correlations in height for men, used as an internal control to compare marital and genetic effects, were unaffected by marriage, as expected. The correlations in height for pairs of sisters, however, were no larger than those observed in pairs of unrelated women married to brothers. It was concluded that in adult married men and women of the Ferrara population, aged 30 to 55 years, the influence of genetic factors on blood pressure is less important than the influence of cultural factors.

Repeated-measures model for the investigation of temporal trends using longitudinal family studies: application to systolic blood pressure

A contemporary path model for the analysis of familial resemblance is extended to incorporate repeated measurements on the entire pedigree over time, in order to assess age-related changes in familiality. The parameters of the model can be defined as arbitrary functions of the ages, age differences, or cohabitation times of the family members at the exact time of measurement. Tracking of the phenotypes is decomposed into a familial and a nonfamilial component, which varies with both the time span between measurements and the ages at measurement. Some of the family members may have data missing on one or more visits, and the visits may be unequally spaced both within and across families. The method incorporates all measurements available from all visits into a single model. The model is applied to longitudinal data on systolic blood pressure in 490 East Boston families measured two times at 3-year intervals. Evidence for some nonfamilial tracking is found. Additionally, significant temporal trends are demonstrated in the familiality as a function of age, t2(A), which appears to be near zero at birth, grow to a maximum of about 40% at around age 30, and then appears to monotonically decrease again. No evidence was found for temporal trends in marital resemblance or residual sibling environmental effects. This model provides an objective method of investigating developmental changes in the correlational structure of families over time using repeated-measures and of estimating continuous changes in familiality with age.

Cardiovascular risk factors in a French Canadian population: resolution of genetic and familial environmental effects on blood pressure using twins, adoptees, and extensive information on environmental correlates

Genetic and environmental influences on systolic (SBP), diastolic (DBP), and mean arterial (MBP) blood pressure were examined using an expanded version of a path model in which parents and their singleton, twin, and adopted offspring were incorporated, and which also included an environmental index as an estimate of the underlying familial environmental component. Estimates of genetic heritability are lower in parents (10-15%) than in offspring (40-50%). Cultural heritability was significant for SBP (0.31) and MBP (0.40), and an intergenerational effect was found for DBP, with higher estimates in parents (0.42) than in offspring (0.21). Marital resemblance was significant, and no support was found for differential maternal and paternal cultural transmission. Two novel results arising from this study are 1) gender-specific sibling effects, with greater female than male resemblance for SBP and MBP and the opposite pattern for DBP, and 2) the suggestion of extra twin resemblance arising on account of additional shared environments and resulting in greater like-sex than opposite-sex twin resemblance. The major conclusions drawn from this study are that 1) parameter estimates are stable with or without the use of extensive environmental indices, and 2) the addition of twins and adoptees did not significantly impact the results, with the exception of a possible influence of the adoptees in estimates of cultural heritability for DBP. Combining both these features (i.e., extended relatives and environmental indices) enables testing for additional sources of familial aggregation, which is not possible using the traditional nuclear family approach and results in a more accurate assessment of the relative roles of heredity and environment on blood pressure than has been previously possible.

Familial aggregation in the presence of temporal trends

Models for assessing temporal trends in familial aggregation are described for both cross-sectional and longitudinal family data. Simultaneous linear structural equations on latent variables are used to model the dependence among family members. The coefficients of the equations are assumed to be parametric functions of time, so that quite complex temporal trends in familial aggregations can be accommodated. Variable family sizes and missing data values pose no problem as the parameters of the models are estimated via maximum likelihood techniques. One of the models is applied to systolic blood pressure data in 542 Japanese-American nuclear families. The results indicate limited evidence for temporal variation in the genetic expression, but that there is substantial temporal variation in environmental influences, which appear to peak at middle age.

Family resemblance for anthropometric and blood pressure measurements in Black Caribs and Creoles from St. Vincent Island

This paper examines family resemblance for five anthropometric measurements (height, weight, triceps skinfold, upper arm circumference relaxed [UACR] and flexed [UACF] and for systolic and diastolic blood pressure in a group of adult Caribbean islanders of primarily African ancestry. Six hypotheses about family resemblance are tested by using path analysis and likelihood ratios. Significant intergenerational transmission is found only for height and UACR. For weight, UACF, and diastolic blood pressure, non-transmissible sibling resemblance is the primary component of family resemblance, although significant marital resemblance exists for diastolic blood pressure. Triceps skinfold and systolic blood pressure show no evidence of any family resemblance. Although results for highly heritable traits such as height are comparable to reports from other populations, measurements with a large contribution from common family environment or residual environmental effects, such as triceps skinfold or blood pressure, have much lower family resemblance in this population than in other populations. We hypothesize that this difference is due to the fact that adult children and their parents do not share a common household in this culture and to the presence of major nonfamilial environmental factors contributing to obesity and hypertension in this population.

Epidemiological studies of hypertension among elderly Japanese and Japanese Americans

A prospective international study of cardiovascular disease among Japanese men living in Japan, Hawaii and California in 1965 provided the opportunity of comparing the levels of blood pressure and hypertension among men aged 45 to 68 years, and of examining the factors which accounted for the differences. In addition, within the group of 8, 006 men from Hawaii, a subsample of men were examined 15 years later when they were aged 60 to 80 to study the influence of migration, the stressful aspects of culture change, diet, life-style, Type A behaviour and biological characteristics for association with blood pressure and as predictors of hypertension.

At the initial examination, the men in California had the highest levels of blood pressure and hypertension, the men in Japan had the lowest levels, and the men born in Hawaii had intermediate levels. When blood pressure was adjusted for relative weight, the differences among the groups disappeared.

Within the Hawaii cohort, bivariate and multivariate analyses of more than 50 variables indicated that age, obesity, alcohol intake, serum glucose and parental history of hypertension were the major variables independently associated with cross-sectional levels of blood pressure and, except for alcohol intake, with longitudinal changes in blood pressure.

Reported dietary intake of calcium, magnesium, potassium, protein and other nutrients were all inversely associated with blood pressure levels. The intake of those nutrients was so highly correlated with each other that it was not possible to identify the independent association of any single dietary factor. The results suggested that the foods which are major sources of the nutrients (vegetables, fruits, whole grains and low fat dairy products) may be protective against hypertension. Blood pressure was not associated with salt, or salty Japanese foods, either in the international comparisons or in the group from Hawaii.

Among the psychosocial factors, there was no evidence that measures of theoretically stressful social situations, social support or the Jenkins measure of Type A personality were associated with blood pressure within the Hawaiian group.

From the perspective of prevention of hypertension in the elderly, these data suggest that obesity, alcohol intake and low intake of minerals found in fruits, vegetables and whole grains are the factors which should receive primary consideration.

Factor analysis suggesting contrasting determinants for different blood pressure measurements

A multiple regression analysis was performed on statistically independent factors derived from blood pressure measurements and possible predictive variables in 618 Utah adults. Nine blood pressure factors obtained in a previous study composed the dependent variables; 35 anthropometric, questionnaire, and biochemical variables were reduced by factor analysis to 10 factors and used as independent variables. Body size and obesity had significant independent effects on different types of blood pressure: body size correlated most highly with systolic blood pressure, while obesity correlated most highly with sitting diastolic blood pressure measurements. Smoking did not correlate with sitting blood pressure but did show a significant positive correlation (after controlling for obesity) with tilt and supine diastolic pressure. Alcohol consumption correlated positively with sitting diastolic pressure when the effects of body size and obesity were controlled. No correlations were found between urinary potassium or sodium excretion and any blood pressure factors, but a significant positive correlation was seen between plasma sodium concentration and several different types of diastolic blood pressure measurements. Psychological stress showed a significant independent positive correlation with systolic blood pressure measurements that was strongest in adults over 35 years of age. The multiple correlation values for the multiple regression equations ranged from 0.19 to 0.52.

Genetics of primary hypertension

Geneticists seek to understand the interaction between genetic and environmental causes of phenotypic variation among individuals in a population. Clinical studies have established that an individual's blood pressure (BP) level is the consequence of the interaction of biologically determined characteristics of the nervous, renal, endocrine and circulatory systems with factors that define one's environment, such as dietary salt, stress and exercise. The many genes that orchestrate the development of these biologically determined characteristics are expected to determine one's BP level, one's increase in BP with age and one's BP response to changes in the environment. One consequence of such a multifactorial etiology is that there are multiple combinations of genetic and environmental factors that may lead to the same BP level. The prevention and control of hypertension will be enhanced when intervention strategies take into account this etiological heterogeneity in determining the hypertensive endpoint. We are pursuing a level crossing strategy in the study of the causes of interindividual BP differences. According to this approach relevant phenotypes that link genetic and environmental factors with blood pressure levels are identified, the genetic contribution to variability in these phenotypes is estimated and then the contribution of this genetic etiology to blood pressure variability is evaluated. We have successfully carried out such a level crossing approach in our investigations of the genetics of red cell sodium lithium countertransport and the relationship between sodium lithium countertransport and blood pressure. A single gene effect on red cell sodium lithium countertransport levels is the only single gene known to affect interindividual blood pressure variability.

Family history of myocardial infarction as an independent risk factor for coronary heart disease

The hypothesis that a family history of heart attack before the age of 60 years is an independent risk factor for coronary heart disease was examined in a random sample of 1044 men aged 40-70. Data on personal and family history, smoking, weight, height, plasma lipid and lipoprotein concentrations, blood pressure, and resting and exercise electrocardiograms were collected according to the standard Lipid Research Clinics protocol. A history of heart attack in first degree relatives was ascertained by interviewing the participants. Evidence of coronary heart disease was found in 123 men (reported heart attack in 20, electrocardiographic findings of ischaemic heart disease at rest in 40, and electrocardiographic findings during heart rate limited exercise in 63). Subjects with coronary heart disease had considerably higher concentrations of total cholesterol, higher blood pressures, and lower concentrations of high density lipoprotein cholesterol than those without. Twenty nine per cent of the subjects with coronary heart disease reported a history of heart attack in a first degree relative before 60 years of age compared with 19% of those without. In a multivariate logistic model, the coefficients for age, cholesterol concentrations, and hypertension were all positive and statistically significant. The coefficient for HDL cholesterol concentration was negative and significant. A family history of heart attack showed a significant positive association, indicating a relation with coronary heart disease that is independent of the other variables in the model. The relation persisted in apparently asymptomatic patients with coronary heart disease.

A new model for the resolution of cultural and biological inheritance in the presence of temporal trends: application to systolic blood pressure

A contemporary path model for the resolution of cultural and biological inheritance is extended to incorporate temporal variation in family resemblance. Specifically, the genetic and environmental effects, like all other parameters of the model, are allowed to vary over an individual's age according to some specific mathematical functions. In the computer program BETREND a library of such functions is incorporated. Data on systolic blood pressure in 542 Japanese-American nuclear families were analyzed. This new methodology detected significant temporal variation in cultural inheritance, a result that was not found previously by using static models which could only distinguish between adult and childhood heritabilities. Cultural heritability, estimated to be 10% at birth, increases to a maximum of 28% at age 36, at which time it declines until it eventually reaches 10% at age 49. Although not statistically significant, there was some evidence for temporal trends in genetic heritability as well. Ignoring trends, the genetic heritability was estimated as .30. On the other hand, trends in sibling environment were clearly nonsignificant. This model provides an objective method of testing the significance of temporal trends in familial resemblance by using multifactorial models, of resolving varying gene expression and transient environmental effects as possible sources of generating the observed temporal variation, and of estimating continuous changes in heritability with age.

The Cincinnati Lipid Research Clinic family study. Bivariate path analyses of lipoprotein concentrations

Methods for the analysis of the joint transmission of two phenotypes are described and used to determine the extent to which lipoprotein concentrations share a common genetic and/or environmental background. Analysis of data on 160 Caucasian nuclear families revealed that the observed phenotypic association between high-density cholesterol (HDL) and low-density cholesterol (LDL) could be accounted for in terms of common family environmental effects alone (estimated genetic correlation, ρG = −0·132±0·136; estimated residual environmental correlation, ρR = 0·065±0·230). The association between HDL and very-low-density cholesterol (VLDL) could not be accounted for in terms of family environmental effects alone. For HDL and VLDL the residual environmental correlation was significant while the genetic correlation was not (ρG = −0·111±0·214, ρR = −0·421±0·172). The correlation between LDL and VLDL also could not be accounted for in terms of common family environmental effects alone, although here a genetic relationship appears to be the important factor (ρG = 0·330±0·192, ρR = 0·010±0·217).

Cultural and biological inheritance of plasma lipids

A path analytic model for the analysis of nuclear family data is described and used to analyze the results of two major studies of cholesterol (CH) and triglyceride (TG), the Honolulu Heart Study (HHS) of Japanese-Americans and the Cincinnati Lipid Research Clinic (LRC) study of Caucasians. The studies were first analyzed separately to assess evidence for genetic and cultural transmission, marital resemblance, and maternal environmental effects for the two plasma lipids, and then simultaneously to identify the nature and sources of any between-study-heterogeneity. There were significant sources of heterogeneity between the two studies for CH (only marital environmental resemblance and non-transmitted sibling environmental resemblance) and for TG (only non-transmitted sibling environmental resemblance). The two studies were homogeneous with respect to the magnitude of genetic and cultural effects; for CH genetic heritability was estimated as h2 = .594 +/- .041 while cultural heritability was estimated as c2 = .035 +/- .008, and for TG the two heritabilities were estimated as h2 = .259 +/- .034 and c2 = .108 +/- .014. An additional bivariate analysis of the association between the two lipids revealed that all phenotypic resemblance could be explained in terms of an association of non-transmitted residual environments with little evidence for a genetic association. The relevance of these results for an understanding of the genetic epidemiology of plasma lipids is discussed.

Coronary heart disease: genetic aspects

Morbidity and mortality differences between populations, between ethnic groups and between individuals are not satisfactorily explained by the variation of risk factors. Differences in genetic susceptibility might be responsible for a part of the unexplained variation of coronary heart disease (CHD) rates. Genetic factors are also significant in determining the level of risk factors in individuals. Ample evidence links genetic factors to the levels of serum cholesterol, blood pressure and diabetes. Marked sex differences in CHD mortality also indicate the role of heredity in the development of the disease. The male:female ratio varies widely between different countries, as well as between different ethnic groups. These variations are difficult to explain by variation in environmental and behavioral differences between males and females alone. The degree of atherosclerosis in males and females varies, depending on the anatomic location of the atherosclerosis. Inherited disorders of metabolism and the variability of anatomic patterns provide additional indications of the role of genetics. The data accumulated in the Israeli Ischemic Heart Disease Study over 15 years reveal an ethnic variation of risk factors coupled with remarkably larger variation in disease rates. Patterns of incidence assessed in the national mortality data of the Israeli study and in histologic findings in the coronary arteries of infants from different ethnic groups are compatible with a hypothesis that ethnic and sex differences in early structural changes of the coronary arteries partly determine the susceptibility of the latter to the development of atherosclerosis. In conclusion, findings from our studies and the review of the evidence from genetic epidemiologic investigations indicate a significant role of genetics in determining the degree, time course and severity of the atherosclerotic process and of the occurrence of symptomatic CHD. This important role of the genetic component is relevant to preventive strategies offered as tools for reducing the burden of CHD. Research into genetic determinants of both susceptibility to atherosclerosis or clinical manifestation of CHD and individual response to preventive measures should be encouraged.

Family resemblance for fasting blood glucose in a population of Japanese Americans

The pattern of inheritance of fasting blood glucose was examined in a Japanese cohort of 500 nuclear families living in Hawaii. A principal component of glucose was defined to improve the ranking of diabetics and individuals receiving treatment (medication and/or diet) for hyperglycemia, thereby allowing as well as possible for inability to determine untreated levels in patients. Results from path and segregation analysis show that family resemblance for glucose is low in this population. The additive variation can be explained by a cultural model of inheritance without introducing intergenerational differences, a maternal-paternal effect, or even genetic parameters. Heritability is approximately 0.125. Complex segregation analysis provides no convincing evidence for a major gene, with preliminary support based upon leptokurtic outliers in five families disappearing on further analysis by partial truncation. A claim by other workers of a major recessive gene for hyperglycemia may be due to their failure to allow for treatment, skewness, and multifactorial heritability. In future, the search for major loci acting on liability to hyperglycemia should use multiple determinations of fasting glucose or be addressed to more primary and repeatable variables than fasting blood glucose.

Heredity, stress and blood pressure, a family set approach: the Detroit Project revisited

Earlier conclusions from the Detroit Project utilizing an innovative "family sets" approach indicated that unspecified environmental factors, rather than genes, are the main determinants of blood pressure variation in blacks and whites. We report new estimates of the fraction of variation in blood pressure associated with genetic differences among individuals obtained under two methodologies: the method originally proposed for family sets and a maximum likelihood method. The family sets estimates of heritability were significant for systolic and diastolic blood pressure in both blacks and whites. Estimates for both the likelihood analysis and family sets method are within the range of estimates reported in other studies. In the present study all sets collected were included, the sets were stratified only by race and a different estimate of variance for the family sets estimate of heritability was used. The discrepancies between results presented here and the original study are attributed to these three factors.

Path analysis under generalized assortative mating. II. American I.Q

Rice, Cloninger & Reich (1980) showed that correlational data on American I.Q. is consistent with a rather low genetic heritability. Here we confirm their general results with a more parsimonious model. From phenotypic data alone, the estimates of genetic and cultural heritability are 0·31 and 0·42, respectively. Using environmental indices, the parsimonious estimates become 0·34 and 0·26, respectively.

Familial determinants of blood pressure in northeastern Brazil

Genetic heritability in this triracial population is 0.41 for systolic pressure in children, 0.14 for systolic pressure in adults, and 0.34 for diastolic pressure in both generations. Cultural inheritance is much smaller, and there is no evidence of maternal effects or major loci.