Racial differences in blood pressure control.

Children from an entire biracial geographical population were examined for blood pressure. A sample of 278 children, stratified by diastolic blood pressure, was reexamined 1 to 2 years later. Dopamine beta-hydroxylase, renin activity, and resting heart rate were observed in black and white children. In the group with high blood pressure, whites had higher heart rates and greater renin activity than blacks. Dopamine beta-hydroxylase concentrations in blacks were lower than in whites over the entire spectrum of blood pressure levels. High blood pressure seems to have a different metabolic background in the two races which may influence the early natural history of essential hypertension. Therefore, the rationale of prevention, and possibly treatment, of early hypertension in blacks and whites may differ.

Time course study of blood pressure in children over a three-year period. Bogalusa Heart Study.

Indirect blood pressure (BP) was measured by mercury sphygmomanometer on 3524 children, ages 5-14 years, representative of a defined geographic population. Year 1 to Year 4 correlations ranged from 0.52 to 0.63 systolic blood pressure (SBP) and from 0.23 to 0.45 diastolic 4th phase blood pressure (DBP4). Some 55% of those originally in the upper decile remained in the uppermost two deciles 3 years later. All children ages 5, 8, 11, and 14 years were reexamined annually, and the mean year-to-year standard deviation (SD) within the child was computed to be 5.5 mm Hg SBP and 5.9 mm Hg DBP. After 3 years, for all available children (n = 2601) the age-specific cross-sectional SD was found to be 8.7-9.7 mm Hg SBP and 7.6-8.0 mm Hg DBP. These data enabled us to quantify the regression to the mean due to within-child variation for the uppermost and the lowest decile BP, using the Gardner-Heady model. These children had an average BP at examination that differed from the expected level (adjusting for regression to the mean due to within-child variation) by 1 mm Hg SBP and DBP. Quantification of the degree to which children's BP "tracks" is important for early diagnosis and intervention in high BP.

Racial contrasts in cardiovascular response tests for children from a total community.

Cardiovascular risk factors in childhood were assessed by re-examining a random sample of 278 children stratified by diastolic blood pressure (BP), obtained from 3524 children aged 7-15 years in an entire geographic biracial community (Bogalusa). Re-examination included plasma renin and serum electrolytes, 24-hour urine electrolytes, heart rates, and BP at rest and in response to standardized physical stresses (orthostatic, isometric handgrip, and cold pressor tests). The BP responses in these tests were not increased in the high BP strata, which argues against a prevailing labile phase in early essential hypertension. Black children tended toward larger BP responses than whites. In black boys of the high BP stratum (n = 25), systolic supine or stressed BP were higher than for other race-sex groups; these pressures were associated negatively with plasma renin activity, which was low. White children in the high BP strata had increased heart rates, possibly indicating hyperkinetic circulation. These findings indicate that multiple mechanisms operate to contol BP at different intensities for black and white children.

Comparison of two automatic blood pressure recorders and the mercury sphygomomanometer.

The Physiometrics automatic blood pressure recorder was compared with the mercury sphygmomanometer in 2200 children aged 5-14 years, each reexamined after 3 and 5 years; the Physiometrics recorder produced higher intrachild correlations. In trials we could transfer what were essentially Physiometrics readings into levels similar to mercury sphygmomanometric readings by filtering out the infrasonic frequency band. The Physiometrics USM-105 was compared with its successor, the Physiometrics SR-2, on 378 children aged 10-17 years. The SR-2 measured lower than the USM-105: 4.1 mm Hg systolic and 8.5 mm Hg diastolic; differences were larger in the younger children. Both in mean levels and correlations, SR-2 readings were closer to the mercury sphygmomanometer's than were USM-105 readings, except or diastolic SR-2 readings, which were farther below the mercury sphygomomanometer 4th-phase readings than the USM-105. However, the SR-2 readings are likely closer to the true diastolic pressure in children 13 years and older, although we did not measure pressures intraarterially. Disc readings for systolic pressures showed coefficients of correlation averaging 0.96 among (n = 168) and 0.98 within (n = 40) readers for both models, but diastolic readings showed marked improvement form USM-105 (0.73, 0.81) to SR-2 (0.91, 0.97). In many of the parameters observed, SR-2 constitutes an improvement over USM-105. Automatic recorders offer certain advantages for measuring blood pressure in large-scale epidemiologic studies.

A model of intervention for prevention of early essential hypertension in the 1980s.

The onset of essential hypertension early in life is indicated by the high tracking of blood pressure during adolescence; intervention in adults with mild hypertension has been found successful. How, then, can high blood pressure levels in children be modified to prevent early hypertensive cardiovascular disease in adulthood? In an entire biracial town (population 9000) we surveyed 1604 (89%) of all children aged 8--18 years for blood pressure and reexamined those in the upper decile of mean blood pressure (for each race, sex, and height) on three additional occasions. On each examination nine blood pressures were taken by trained observers. All children consistently in the top decile were randomly allocated into either a treatment (n = 50) or comparison (n = 50) group. These two groups and an additional midrange blood pressure comparison group (n = 50) were followed regularly using school facilities including community and school programs. Treatment consisted of 1) dietary guidance; 2) modifications of school lunches and snacks with healthy substitutes; 3) parental involvement; 4) a low dose diuretic and beta-antagonist given by usual standards. All study groups were monitored for blood pressure in a blind manner. In 6 months of observation, blood pressure in the treatment group remained 5 and 3 mm Hg (systolic and diastolic) less than controls (p less than 0.001 and p less than 0.01). An orchestrated community-wide attack on early-stage hypertension is feasible and seems to offer exciting potential for prevention of early hypertensive disease.

Relation between ingested potassium and sodium balance in young Blacks and whites.

The relationship of dietary K+ with Na+ balance in young normotensives was studied. A, In two biracial communities, all children with specified age were stratified by blood pressure level. Children from selected strata collected 24-h urines on ambulatory basis and provided fasting blood for electrolytes and creatinine determination. For the upper percentile ranks (n = 160), the Na+ and K+ clearances correlated closer in Blacks than whites (r = 0.7 versus r = 0.4, p less than 0.005 for difference). B, To test for a causal effect of K+ intake on Na+ excretion, six white and eight Black young healthy normotensive volunteers took 80 mEq KCl daily in addition to their usual diets. They collected 24-h ambulatory urine and stool samples for 3 base-line days, and 4 days during K+ supplementation. Na+ and K+ intake was monitored daily. Upon K+ supplementation, Blacks showed natriuresis (p less than 0.01), negative Na+ balance (p less than 0.05), and a cumulative K+ balance more positive than whites (p less than 0.0001 versus p less than 0.05). Dietary K+ enrichment could affect Na+ balance.

Anthropometric and maturation measurements of children, ages 5 to 14 years, in a biracial community--the Bogalusa Heart Study.

An epidemiological survey of anthropometric and maturation variables was conducted on 3,524 children from the biracial community of Bogalusa, Louisiana. These children, representing 93% of the population, were examined during the school year September 1973 through May 1974. Black boys differed slightly from white boys in height and weight; black girls were taller and heavier than white girls. The black children had longer upper arm lengths and smaller upper arm circumferences than the white children. The median ponderosity (weight divided by the cubed height) decreased with increasing heigth for the four race-sex groups, and a skewed distribution of ponderosity indicated an excess of heavy children among the tall. Based on the Tanner criteria for grading secondary sex characteristics, maturation occurred earlier in the more ponderous girls, although such was not the case for boys. Whereas the Tanner secondary sex characteristics appeared earlier in black girls, white girls reported menarche earlier. The racial and sexual differences known to exist in triceps skinfold were observed for this population. No statistically significant difference was observed overall for height and weight between children within this one community and those of the National Health Examination Survey. However, Bogalusa girls at the 95th percentile were heavier after age 11 than girls of the United States. Also, there was a tendency for white girls in this community to report reaching menarche at an earlier age than black girls, which contrasts slightly with the national sample.

A simplified inventory method for quantitating dietary sodium, potassium, and energy.

During an 8-day observation of the effect of K+ supplementation (80 mEq) on Na+ and K+ balance in a biracial sample of young adults (n = 14), a Food Inventory was developed to monitor dietary Na+, K+, and energy intakes. Urine and stool samples provided electrolyte output measures. The Food Inventory reduced heterogeneity of foods consumed and simplified quantitation. It was self-administered and consisted of 10 preselected foods categories, each containing 24 to 40 food items. Energy was higher for whites and for males (p less than 0.10). Both total Na+ intake and Na+ per 1000 kcal were higher for males. A 1.4 Na+/K+ dietary ratio was observed. After K+ supplementation, Na+ balance was negative; a marked natriuresis occurred, being more consistent for Blacks. With K+ supplementation a positive K+ balance occurred and was more evident in Blacks. Significant positive correlations of daily Na+ and K+ intakes with output were observed with higher correlation for K+ than Na+. This dietary assessment method can be useful in metabolic or behavioral studies requiring quantitation of electrolytes and energy.

Cardiovascular risk factors from birth to 7 years of age: the Bogalusa Heart Study. Blood pressure.

BP was measured in 440 children followed longitudinally from birth to 7 years of age in Bogalusa, LA. Levels, trends, and determinants of BP were evaluated in this newborn cohort. Both systolic and diastolic BP levels remained relatively constant between the ages of 6 months and 7 years. BP levels varied between the different instruments, and differences were also noted between measures obtained using the same instrument before and after venipuncture. White children were noted to have slightly higher levels of systolic and diastolic BP pressure at 6 months and 1 year of age, even after adjustment for body size. Significant prediction of year 7 BP rank occurred as early as 6 months of age for systolic and at 1 year of age for diastolic BP levels. Body size was inconsistently related to BP levels from ages 6 months through 4 years, but the relationship was stronger and more consistent with changes in body size. Of interest is the relatively constant levels of indirect BP during this period of rapid growth, as measured by currently available instruments. These data emphasize the importance of cardiovascular risk factor measurement during early life and of the need to improve methods of indirect BP measurement in infancy.

Racial differences of parameters associated with blood pressure levels in children--the Bogalusa heart study.

Racial differences in prevalence of essential hypertension are well known. In order to explore these differences at an early age in terms of etiology, we investigated schoolchildren in an entire, biracial community. A sample of 278 children, stratified by diastolic (fourth-phase) blood pressure and specific for age, race, and sex, was reexamined 1--2 yr after initial observation for the following: (1) a physical examination and urinalysis to exclude secondary hypertension; (2) 24-hr urine sodium, potassium, plasma renin activity, and serum dopamine beta-hydroxylase; (3) 1-hr oral glucose tolerance test; and (4) heart rate and blood pressure at rest and under standarized physical stress. We found that 24-hr urine sodium was positively associated with blood pressure level as measured on the same day for the high blood pressure strata of black children. Urine potassium excretion was lower in blacks than in whites, although their intakes seemed equal. In the high blood pressure strata especially, black boys had lower renin activity than whites, and the resting-supine and stressed systolic blood pressures were higher in black boys than in any other group. In these black boys, resting and stressed systolic pressures were negatively related to plasma renin activity. On the other hand, dopamine beta-hydroxylase levels in white children were higher than in blacks for all blood pressure strata, and in the high blood pressure strata white children had higher 1-hr glucose levels and faster resting heart rates than black children. Different mechanisms may play a role in and contribute to the early stage of essential hypertension.

Combined low-dose medication and primary intervention over a 30-month period for sustained high blood pressure in childhood.

Studies of the pathobiologic consequences of high blood pressure in childhood, as well as those following blood pressure levels into young adulthood, indicate that early intervention in the natural history of essential hypertension is warranted. In an exploratory study of the concept, 95 children out of 1604 (aged 8 to 18 years), who persistently scored higher than the 90th percentile for blood pressure over a 4-month period, considering the race, sex, and height of the children, were studied. Five series of replicate measurements with 30 total observations were obtained. Children with evidence of secondary hypertension were excluded. The study children were randomly divided into treatment (n = 48) and high-comparison (n = 47) groups. Treatment consisted of low-dose combined drug therapy (propranolol and chlorthalidone) with an educational program directed towards hypertension and dietary and exercise modification. Monthly follow-up was continued for 30 months. Significant systolic (-3.59 mm Hg) and diastolic (-1.73 mm Hg) changes were noted up to 30 months (p less than 0.05) with minimal side effects. Furthermore, analyses suggested that the blood pressure change, at least in the first month, was mostly attributable to drug therapy. Moreover, the mechanism of blood pressure change appeared to be race-specific, with whites having pulse rate changes and blacks having significant weight changes, which were associated with blood pressure change. This trial shows further research is warranted to determine optimum approaches for early treatment of essential hypertension to prevent future hypertensive disease.

Epidemiology of essential hypertension in youth--implications for clinical practice.

Essential hypertension, a highly prevalent and devastating disease, likely begins in childhood, and presumably might respond at this stage to general preventive measures. The problems encountered in the recording of reproducible blood pressure levels are largely of a quantitative nature, and involve instrument validity, observer (examiner) training, and the interaction between the child and the physician's office environment. The problems of early diagnosis of hypertension are related to the lack of long-term observations of children. Population percentiles of normal blood pressure values could aid in the early diagnosis of hypertension. For this purpose the method of blood pressure measurement in the physician's office has to be strictly comparable to methods employed in accumulating the percentile or reference observations. Repeated measurements under basal-like conditions are advised, and the weight or height of the child is more important for standardization than is age.

Hemoglobin levels and dietary iron in pubescent children in a biracial community.

Although differences in hemoglobin levels between blacks and whites may be due in part to genetic influences, low hemoglobin levels in black girls of childbearing age may nevertheless constitute a health hazard. To study this problem, hemoglobin levels were examined in children of a biracial community not only before but also during and after puberty and menarche. At the same time, 24-hour dietary recalls of a representative group of 13-year-olds in the same population were examined with respect to the intake of iron and nutrients influencing iron absorption. In black girls, hemoglobin levels dropped after menarche, accompanied by a diet marginal in iron and in iron-absorption-promoting nutrients. Questions as to hemoglobin levels compatible with optimum health remain, and racial differences and genetic influences on levels should not be an excuse for failure to address this problem. More investigational studies are also needed to observe responses to an optimum dietary iron intake.

Relationship between respiratory cancer and wetlands residency in Louisiana.

Cancer mortality is high among white men residing in southern Louisiana parishes (counties). In an effort to elucidate this phenomenon, we studied three environmental correlates of cancer-namely, smoking, residence in urban communities, and residence in the wetlands. Multiple regression analysis was applied to cancer mortalities adjusted for age and urban residency, and specific for race, sex, amount of standing water area in the parish, and cancer site. Cancer sites were grouped according to their correlation with smoking: strong, moderate, and no correlation. For men, the smoking-related cancer mortality not only showed an association with residence in wetlands but also was higher in the Louisiana wetlands than in the remainder of the United States.

Additive statistical effects of cadmium and lead on heart-related disease in a North Carolina autopsy series.

The association of heart-related mortality with tissue cadmium and lead in a study of autopsies performed on persons who resided in a soft-water, leached-soil area of North Carolina was examined. Liver cadmium concentrations and aortic lead level were indices of these elements. Both cadmium and lead levels had statistically significant correlations with cause of death (heart-related disease vs. non-heart-related disease, excluding cancer). Although cause of death was significantly associated with age, the association with cadmium and lead persisted after statistical adjustment for the effect of age. The combined effects of cadmium and lead provided sufficient information in an additive model to predict cause of death correctly for 80% of the cases, with age contributing insignificantly. These findings indicate the intimate relation of these two trace metals with increased risk of heart-related mortality, even in light of known conventional causes of such deaths.