The Detroit project studies of blood pressure. A prologue and review of related studies and epidemiological issues

A family study of developmental effects upon blood pressure variation

In an earlier study of blood pressure variation in middle aged parents and their young adult twin offspring, the greater blood pressure variation observed in the parent sample was accounted for in terms of an increasing influence of individual environmental experiences with increasing age and a commensurate reduction in the impact of heredity. In the present study, the sample size was enlarged to provide a more powerful test of these effects. Maximum likelihood model-fitting techniques were applied to blood pressure covariation in balanced pedigrees, consisting of 85 families (40 MZ and 45 DZ twin pairs). As before, our analysis indicated that a developmental effect was a salient factor in the older age group.

Familial aggregation in physical fitness, coronary heart disease risk factors, and pulmonary function measurements

In order to test for the presence of familial aggregation in physical fitness and coronary heart disease risk factors, body fat, submaximal power output, muscular strength, muscular endurance, blood pressure, pulmonary functions, and several blood biochemical variables were measured in 304 nuclear families living in the Quebec city area. Analysis of variance indicated a larger between-family than within-family variation for all the variables. When all members of nuclear families were considered, intraclass correlations ranged from 0.21 to 0.34 (P less than or equal to 0.01). Interclass correlations computed for various pairs of relatives revealed significant parent-child and sibling correlations for all the variables (0.14 less than or equal to r less than or equal to 0.55; P less than or equal to 0.01). On the other hand, spousal correlations tended to be lower but significant (0.10 less than or equal to r less than or equal to 0.30; P less than or equal to 0.05) for all variables except subcutaneous fat and hemoglobin concentration. These results suggest that heredity and common lifestyle shared by members of nuclear families are responsible for the familial aggregation of physical fitness, coronary heart disease risk factors, and pulmonary functions. The findings also support the notion of considering the nuclear family as a unit of intervention in the application of preventive measures aimed at the reduction of several risk factors.

Familial and individual influences on blood pressure

Although familial aggregation of blood pressure is well documented, few studies have considered the changing contribution of genetic and environmental influences during adulthood. Applying maximum likelihood model fitting to blood pressure covariation in balanced pedigrees including both parents and their young adult twin offsprings (25 MZ, 32 DZ, aged between 16 and 24 years), it is shown that the increased variation in parents is explained by such developmental changes. For DBP, an apparent reduction in heritability from 68% to 38% from young adulthood to middle age results from the increasing impact of individual environmental experience (E1), with little or no influence from shared family environmental (E2). For SBP, shared environmental effects may play a part. Given the relatively small size of the present sample, the conclusions are to be seen as tentative. An augmented family study, incorporating middle aged twins and their young adult offspring, will clarify the causation of these developmental changes.

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.

Residential mobility and urban-rural residence within life stages related to health risk and chronic disease in Tecumseh, Michigan

Residential history, diagnosis of three chronic diseases, five clinical measurements and histories of smoking and drinking were obtained from a sample of 615 women and 529 men, aged 35-69, randomly selected from respondents of the Tecumseh Community Health Study. Two measures of residential mobility and one of urban-rural residence, during early life stages and over the entire lifetime, were related to subsequent adult health traits. Greater residential mobility, particularly in childhood but also in later life, was significantly associated with greater prevalence of hypertension and higher mean diastolic blood pressure in older persons. Greater duration of urban residence was associated with greater prevalence of chronic bronchitis. Both residential traits were associated with greater prevalence of CHD, and with behavior patterns, namely cigarette smoking and drinking, that are risk factors for certain chronic diseases.

Social factors in the etiology of multiple outcomes: the case of blood pressure and alcohol consumption patterns

The literature addressing the relationships between biological and social factors in the etiology of multiple chronic diseases occurring simultaneously is presented. The rationale for studying such multiple outcomes is presented in terms of providing a realistic appraisal of the development of chronic diseases from a clinical perspective; i.e. persons with chronic illnesses often have more than one illness at the same time. Social processes related to the development of one joint disease outcome, namely clinically elevated blood pressure and heavy alcohol consumption patterns, are discussed, and emphasis is given to elaborating the role of stress and social support in the etiologic process. Several alternative models are presented to account for the etiology of the joint outcome, and a research agenda is suggested.

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.

Pathophysiology of hypertension in blacks and whites. A review of the basis of racial blood pressure differences

Differences in blood pressure between blacks and whites in the United States are now well documented. The causes of these differences remain speculative. Genetic factors, personal characteristics, renal physiology, endocrine factors, autonomic nervous system function, cardiac function and various environmental factors are examined in the present review as potential determinants of racial blood pressure differences. Racial differences in renal physiology and environmental influences such as socioeconomic status seem to be likely candidates for important contributions to blood pressure differences. Further research aimed specifically at black-white blood pressure differences is of great importance to a fundamental understanding of the etiology and prevention of essential hypertension.

Skin color, ethnicity, and blood pressure II: Detroit whites

Census areas in Detroit were ranked for their stress scores based on instability (e.g., crime, marital break up) and socioeconomic status. Four areas were selected for detailed study: 1) high stress, population predominantly black and 2) white, and 3) low stress, population predominantly black and 4) white. A sample was drawn from each area of persons of the predominant race, 25-60 years old, married and living with spouse, and having relatives in the Detroit Area. Nurses interviewed such persons; three blood pressure readings were taken during the first half-hour of medical history, and skin color was rated. While lighter skin color showed a negligible relation to higher blood pressure, a four-category division of European national background based on a skin color cline in Europe from Northern areas to the Mediterranean was significantly associated with a nurse-rating of skin color. The rank order of this four category variable, white ethnicity, was related linearly to both systolic and diastolic blood pressure means. Respondents with parents from Mediterranean countries had the lowest pressures and those from Northern Europe had the highest. The relationship is stronger for women than men. The relationship was independent of nine other control variables including age, overweight, smoking etc., and high and low stress areas, although of greater magnitude for the high than low stress groups. In this article, findings in whites are compared with prior results in blacks. Findings suggest that physiological and biological correlates exist that can be explored profitably by future research.