Factor analysis suggesting contrasting determinants for different blood pressure measurements

Body Size Predicts Cardiac and Vascular Resistance Effects on Men's and Women's Blood Pressure

Key Points Summary We report how blood pressure, cardiac output and vascular resistance are related to height, weight, body surface area (BSA), and body mass index (BMI) in healthy young adults at supine rest and standing.Much inter-subject variability in young adult's blood pressure, currently attributed to health status, may actually result from inter-individual body size differences.Each cardiovascular variable is linearly related to height, weight and/or BSA (more than to BMI).When supine, cardiac output is positively related, while vascular resistance is negatively related, to body size. Upon standing, the change in vascular resistance is positively related to size.The height/weight relationships of cardiac output and vascular resistance to body size are responsible for blood pressure relationships to body size.These basic components of blood pressure could help distinguish normal from abnormal blood pressures in young adults by providing a more effective scaling mechanism. Introduction: Effects of body size on inter-subject blood pressure (BP) variability are not well established in adults. We hypothesized that relationships linking stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) with body size would account for a significant fraction of inter-subject BP variability. Methods: Thirty-four young, healthy adults (19 men, 15 women) participated in 38 stand tests during which brachial artery BP, heart rate, SV, CO, TPR, and indexes of body size were measured/calculated. Results: Steady state diastolic arterial BP was not significantly correlated with any index of body size when subjects were supine. However, upon standing, the more the subject weighed, or the taller s/he was, the greater the increase in diastolic pressure. Systolic pressure strongly correlated with body weight and height both supine and standing. Diastolic and systolic BP were more strongly related to height, weight and body surface area than to body mass index. When supine: lack of correlation between diastolic pressure and body size, resulted from the combination of positive SV correlation and negative TPR correlation with body size. The positive systolic pressure vs. body size relationship resulted from a positive SV vs. height relationship. In response to standing: the positive diastolic blood pressure vs. body size relationship resulted from the standing-induced, positive increase in TPR vs. body size relationship. The relationships between body weight or height with SV and TPR contribute new insight into mechanisms of BP regulation that may aid in the prediction of health in young adults by providing a more effective way to scale BP with body size.

The cardiovascular response to postural change as a function of race

Little is known about racial differences in cardiovascular responses to postural change. The immediate and delayed change from sitting to standing was studied in 207 healthy young Asian, black, and white men and women by means of a noninvasive blood pressure tracking system. Whereas Asians and whites had decreased mean arterial pressure (MAP) 32-41 s after standing, blacks had an increase. During the delayed response (3 min after standing), compared to Asians and whites, blacks had greater increases in diastolic blood pressure and MAP. Their heart rate increase was also greater than Asians. For systolic blood pressure and pulse pressure there were Race x Family History interactions for the immediate response to orthostasis and Race x Gender interactions for the delayed response. Blacks generally displayed different cardiovascular patterns from the other two racial groups, possibly reflecting increased peripheral resistance and altered baroreceptor function.

A factor analytic study of physical risk variables for CHD

The scores of 40 hospitalized male coronary heart disease (CHD) patients, for seven traditionally employed physical CHD risk factors, were subjected to a confirmatory factor analysis that employed a LISREL program. An attempt was made to confirm a two-factor solution that involved family history as one factor, and smoking, serum cholesterol level, blood pressure, physical exercise, diet, and weight control as the second. The obtained goodness-of-fit index (.84) suggests that the two-factor solution is a moderately valid one. These findings raise the question whether many of the physical risk factors for CHD simply may be manifestations of a single behavioral characteristic, perhaps best described as "lack of self-control."

Relation between family history of coronary artery disease and coronary risk variables

The relation between family history of coronary artery disease (CAD) and coronary risk variables was examined in 1,058 Utah adults. Subjects were divided into 3 family history score groups (low, intermediate and high) and the effects of 60 potential risk variables were assessed using multiple stepwise discriminant analysis. After controlling for age effects, the variables entering the discriminant function equation (p less than 0.01) were cholesterol, years smoking cigarettes, high-density lipoprotein cholesterol and triceps skinfold thickness. Although normal blood pressure variation did not discriminate among family history groups, those with a positive family history of CAD were more likely to develop hypertension than those without a family history (age-adjusted relative risk 1.79, with 95% confidence limits 1.03 and 3.09). In spite of significant differences among family history score groups with regard to risk variables, the discriminant analysis classified only 39% of subjects into the correct group. It was concluded that other unknown risk variables must mediate the effects of family history of CAD. Thus, family history should be considered an independent risk factor for CAD.

Family history as an independent risk factor for incident coronary artery disease in a high-risk cohort in Utah

To test independence of family history of coronary artery disease (CAD) as a risk factor for the development of new clinical CAD, data collected at 2 clinic visits on 1,196 men and women, ages greater than 20 years, were analyzed using Cox proportional hazard method. During a mean follow-up of 2.5 years, 16 new CAD cases were observed. After adjustment for age, sex, total cholesterol, high density lipoprotein cholesterol, hypertension, diabetes, cigarette smoking and body mass index, family history remained a highly significant predictor of future CAD (p = 0.0017). Only age was a more significant covariate (p = 0.0001) than family history. Sex (p = 0.00074) and serum total cholesterol (p = 0.015) also contributed significantly to CAD incidence while high density lipoprotein cholesterol, hypertension, diabetes, body mass index and several interaction terms did not improve the prediction in this population. These results provide evidence for the existence of other heritable risk factors which appear to contribute strongly to the occurrence of early CAD in many high-risk families.

Recruitment of members of high-risk Utah pedigrees

Cardiovascular Genetics Research Projects in Utah are designed to investigate genetic and environmental determinants of early coronary disease, stroke, and hypertension in population-based pedigrees. Early coronary disease is defined as the occurrence of documented coronary death or myocardial infarction before age 55. Detailed recruitment experience is reported for 2500 persons age 3-83 years in 98 high-risk pedigrees from three ascertainment groups: 1. Descendants of sibships with two or more stroke deaths before age 75. 2. Descendants of sibships with two or more coronary deaths before age 55. 3. First- and second-degree relatives of hypertensive and normotensive probands randomly selected from the Utah Hypertension Detection and Follow-up Program. A response rate of 94% of invited adults attending the first 4-hour clinic visit for detailed screening in 1980-1983 was achieved by multiple telephone, mail, and personal contacts and rescheduling of missed clinic appointments. For the same participants, a second screening cycle in 1983-1986 showed a 91% response of invited adults. Second visit response rates were examined within subgroups according to data collected at the first clinic visit. Below average response rates included 79% of persons with fewer than 12 years of education, 84% of current smokers, and 86% of divorced persons. Above average response rates included 93% of persons attending college and 95% of persons with total family income above $25,000. There were no differences in response according to sex or age. The average cost of recruitment was $59 per person and represented about 10% of the total budget for the High-Risk Pedigree Project.

Vertex-corrected blood pressure in black girls. Relation to obesity, glucose, and cations

Correlates of resting blood pressure (BP) were explored among 32 inner-city, black girls, ages 11.7 to 13.9 years, a sample drawn from the second and fourth quartiles of the BP distribution in an earlier school survey. Customary BP measurements in the seated position were corrected for the height of the arterial column extending from the BP cuff to the top (vertex) of each girl's head. This vertex correction procedure has previously been shown to eliminate the childhood association between mean arterial pressure and age. Vertex-corrected systolic BP was correlated individually (p less than 0.03) with serum fasting glucose, ionized calcium, sodium, and calculated osmolality. The BP association with serum glucose did not persist after an oral sucrose challenge. Vertex-corrected diastolic BP was correlated individually (p less than 0.02) with serum ionized calcium and four indices of obesity, the best correlated of which was the subscapular skinfold (r = 0.66, p = 0.0001). Vertex-corrected BPs generally provided stronger correlations than customary (uncorrected) BPs with the variables of interest. Correlations with seated BPs were generally stronger than those with supine BPs. By multiple regression analysis, seated vertex-corrected systolic BP was related directly to serum fasting glucose and ionized calcium and inversely to pulse rate (R2 = 0.53). Seated vertex-corrected diastolic BP was related directly to subscapular skinfold and calculated osmolality (R2 = 0.54). Vertex correction may facilitate clinical or epidemiological studies of early hypertension.

Innovative blood pressure measurements yield information not reflected by sitting measurements

A study of 873 healthy adults and children from Utah kindreds was performed to identify redundant and unique information contained in multiple diverse blood pressure determinations. Systolic blood pressure, fourth-phase and fifth-phase diastolic blood pressures, and simultaneous heart rates were measured in subjects sitting, standing, supine, and tilting, during half-maximal handgrip exercise, and just before blood drawing. A correlation matrix of 57 blood pressure and pulse variables in 618 healthy adults was analyzed. Factor analysis of the correlation matrix showed that all systolic blood pressures loaded as a single factor, accounting for 44% of the total variance of the observed variables. All heart rates also loaded together as a single factor. Diastolic blood pressures showed much more heterogeneity of information distributed among five separate factors. The same basic factors were found in young adults (age, 18-35 years) and older adults (age, 36 + years). Children under 12 years of age showed very different factor patterns, and youths 12 to 17 years of age showed patterns intermediate between those of adults and children. In light of recent clinical trials, better definitions are being sought for hypertension. Information from blood pressures other than sitting determinations may improve the definition of hypertension or better predict which patients have the highest risk of hypertension and its cardiovascular complications.