The Minneapolis childrn's blood pressure study. Part 2: multiple determinants of children's blood pressure

Cohort Profile: the international childhood cardiovascular cohort (i3C) consortium

This is a consortium of large children's cohorts that contain measurements of major cardiovascular disease (CVD) risk factors in childhood and had the ability to follow those cohorts into adulthood. The purpose of this consortium is to enable the pooling of data to increase power, most importantly for the follow-up of CVD events in adulthood. Within the consortium, we hope to be able to obtain data on the independent effects of childhood and early adult levels of CVD risk factors on subsequent CVD occurrence.

High blood pressure in school children: prevalence and risk factors

Background

The purpose of this study was to determine the prevalence of high blood pressure (HBP) and associated risk factors in school children 8 to 13 years of age.

Methods

Elementary school children (n = 1,066) were examined. Associations between HBP, body mass index (BMI), gender, ethnicity, and acanthosis nigricans (AN) were investigated using a school based cross-sectional study. Blood pressure was measured and the 95^th percentile was used to determine HBP. Comparisons between children with and without HBP were utilized. The crude and multiple logistic regression adjusted odds ratios were used as measures of association.

Results

Females, Hispanics, overweight children, and children with AN had an increased likelihood of HBP. Overweight children (BMI ≥ 85^th percentile) and those with AN were at least twice as likely to present with HBP after controlling for confounding factors.

Conclusion

Twenty one percent of school children had HBP, especially the prevalence was higher among the overweight and Hispanic group. The association identified here can be used as independent markers for increased likelihood of HBP in children.

Oscillometric blood pressure standards for children

We previously reported blood pressure (BP) readings obtained by the Dinamap (DIN) (Model 8100) were 10 mmHg higher than those obtained by auscultatory methods and thus were not interchangeable. DIN BP data on 7208 schoolchildren ages 5 to 17 were analyzed to generate normative DIN BP standards and to examine the rational for presenting BP standards according to age and height percentiles. Three BP measurements were taken in the sitting position using a BP cuff width 40% to 50% of the circumference of the arm. Boys' systolic pressures (SP) were significantly (p < 0.05) greater (up to 11 mmHg) than those of the girls in subjects age 13 to 17 years. SP levels were most closely correlated with weight (r = 0.595), followed by height (r = 0.560) and age (r = 0.518). When BP levels were adjusted for age and weight, the correlation coefficient of DIN SP with height was negligible (r = 0.026 for boys; r = 0.085 for girls), whereas when adjusted for age and height, the correlation of SP with weight remained high (r = 0.303 for boys; r = 0.216 for girls), indicating that height is not an important independent predictor of BP levels. In conclusion, Dinamap-specific BP standards presented in this report are the only standards that have been generated according to the current BP guidelines recommended by national committees. We found no rational for presenting BP standards according to age and height percentiles.

Trajectory of systolic blood pressure in children and adolescents

PURPOSE

Rapid height and weight changes during childhood contribute markedly to blood-pressure change during children's physical growth. This article evaluates the differences in systolic blood pressure (SBP) growth or changes between four gender-ethnic groups: African American males (AM), Caucasian males (CM), African American females (AF), and Caucasian females (CF).

METHODS

Subjects 6-9 years old at entry (n = 1302) were followed for 12 years. The repeated-measure data of SBP were analyzed using the Gompertz growth model with random coefficients.

RESULTS

Mean SBP (mmHg) at age 6 years was lowest in African American girls (82.23 +/- 0.76) and highest in Caucasian boys (102.83 +/- 0.5). And for both ethnic groups, girls had lower levels at which SBP growth stopped. The peak growth ages (years) also differed by group: 9.30 +/- 0.73, 9.91 +/- 0.28, 10.00 +/- 0.82, and 10.60 +/- 0.22 for African American girls, African American boys, Caucasian girls and Caucasian boys, respectively.

CONCLUSION

SBP growth differed among gender-ethnic groups with respect to mean SBP level at age 6, the level at which SBP growth stops and the mean age at which SBP growth rate was at its peak.

Youth blood pressure levels in Samoa in 1979 and 1991-93

Blood pressure (BP) levels were studied in 524 youth ages 4-19.9 years who reside in Samoa. The data were collected in two separate cross-sectional samples taken in 1979 (n = 292) and in 1991-93 (n = 232). BP was compared between these two study samples to evaluate the temporal change in BP among youth in response to the processes of economic modernization in Samoa, and specifically on how temporal increases in body size influenced BP levels. Proportions of youth with elevated BP levels were estimated using the Second Task Force criteria. In males and females 10-19 years, age-adjusted systolic BP was significantly higher in the 1991-93 sample than in the 1979 sample, and the difference became insignificant after adjustment for body mass index. The proportion of those ages 10-19 years with elevated BP ranged from 11-15% in the 1979 study sample and was approximately 25% in the 1991-93 study sample. There appears to be a temporal trend of increasing adiposity and BP in those 10-19 years and the BP differences are attributable to the higher levels of adiposity.

Relation of weight and rate of increase in weight during childhood and adolescence to body size, blood pressure, fasting insulin, and lipids in young adults. The Minneapolis Children's Blood Pressure Study

BACKGROUND

Weight gain is of concern during early development because adult obesity and its cardiovascular consequences appear to have their origins during childhood. Insulin resistance is known to be related to obesity. Thus, weight gain beginning in childhood may influence the development of insulin-induced cardiovascular risk during adulthood.

METHODS AND RESULTS

We monitored 679 individuals from 7.7+/-0.1 years of age with repeated measures of height, weight, and systolic blood pressure (SBP) until 23.6+/-0.2 years of age, when blood samples were obtained for measurements of insulin and lipids. Initial childhood weight, body mass index (BMI), and height were significantly correlated with young adult weight, BMI, and height and with fasting insulin, lipids, and SBP. The increases in weight and BMI but not height during childhood were significantly related to the young adult levels of insulin, lipids, and SBP.

CONCLUSIONS

These data suggest that weight gain in excess of normal growth during childhood is a determinant of adult cardiovascular risk. The finding in multiple linear regression analysis that weight gain during childhood rather than the childhood weight at 7.7 years of age is significantly related to young adult risk factors suggests that a reduction in weight gain could reduce subsequent levels of cardiovascular risk.

Familial aggregation of cardiovascular disease risk factors: the Cuenca Study

OBJECTIVE

The familial aggregation of lipid levels, blood pressure, and body mass index (BMI) was studied in schoolchildren in Cuenca, Spain.

METHODS

A cross-sectional observation study was made of 307 schoolchildren of both sexes, age range 9-12 years, from three schools in Cuenca, Spain, and of 346 parents. Social and demographic variables, weight, height, body mass index, systolic blood pressure, diastolic blood pressure, and fasting plasma concentrations of total cholesterol, LDL-cholesterol, HDL-cholesterol, and triglycerides were evaluated.

RESULTS

The Spearman coefficients of correlation for total cholesterol, LDL-cholesterol, and BMI for parents and daughters were 0.34-0.42 (P < 0.01). These coefficients of correlation for parents and sons were lower (P > 0.05). The coefficient of correlation for blood pressure in parents and sons was low (P < 0.05). None of the variables showed any coefficient of correlation between spouses. The sexual differences in the correlations between the levels of the different variables were confirmed by multiple regression analysis. Total cholesterol and LDL-cholesterol levels and BMI accounted for larger percentages of variability in these parameters in daughters than in sons. The paternofilial aggregation of HDL-cholesterol and triglyceride levels was weak. The only variable that accounted for a significant variability in blood pressure (systolic and diastolic) was weight in children of both sexes.

CONCLUSIONS

The familial aggregation of lipid levels and body mass index showed sex differences. The paternofilial aggregation of blood pressure was weak. There was no relation between spouses.

Percentiles for body mass index in U.S. children 5 to 17 years of age

OBJECTIVES

It has been recommended that body mass index (BMI) (weight in kilograms/height in meter2) be used routinely to evaluate obesity in children and adolescents. This report describes the distribution of BMI in children and adolescents in the United States.

METHODS

Standardized measurements of height and weight from 9 large epidemiologic studies including 66,772 children age 5 to 17 years were used to develop tables for the distributions of BMI that are age, race, and gender specific.

RESULTS

The mean BMI increases with age and is slightly higher for girls than boys. Mean BMI for black and Hispanic girls was noticeably higher than for white girls. The percentiles of BMI are consistently higher than those based on the NHANES I measures, particularly for the 95th percentile. The proportion of obese children compared with NHANES I standards is higher and is highest for Hispanic boys and black and Hispanic girls.

CONCLUSION

The tables and figures will allow pediatricians to determine the relative ranking of BMI for patients compared with values derived from a large sample of healthy children and adolescents. The identified gender and ethnic differences may be guides to understanding the cause and prevention of obesity.

Hypertension in pediatric patients: current issues

OBJECTIVE

To present current information on the diagnosis, treatment, and epidemiologic features of hypertension in children.

DESIGN

The guidelines published by the Task Force on Blood Pressure Control in Children in 1987 are critically evaluated, and more recent data are discussed.

RESULTS

Prevention of the consequences of hypertension necessitates recognition of the condition. Although hypertension in the pediatric age-group is an uncommon finding, it does exist. The diagnosis is based on careful technique, repetitive blood pressure measurements, and comparison with established norms. Normal blood pressure values for children have been derived from a series of large cross-sectional studies. Although they have certain shortcomings, they are useful. Height and weight are important determinants in the use of the normative data. The selection of a blood pressure cuff that completely encircles the arm is crucial. Tracking--the persistence of systolic and diastolic pressures at stable percentiles--is not a constant finding, but children at risk for development of hypertension as adults may be identifiable. As in the adult population, children with hypertension have no signs or symptoms that clearly distinguish primary from secondary hypertension.

CONCLUSION

Treatment of children with hypertension should be individualized. Etiologic evaluation is probably best performed at referral centers.

Blood pressure and self-assessment of female sexual maturation

The relationship of sexual maturation to blood pressure was investigated in a sample (n = 361) of white, non-Hispanic females, aged 7-18 years. Sexual maturation was determined by self-assessment. Systolic and fourth- and fifth-phase diastolic blood pressures increased significantly with increasing maturation. Body mass index, breast development, and pubic hair growth explained 29% of the systolic blood pressure variance and 23% of the fourth- and fifth-phase diastolic blood pressure variances. The interpretation of a child's or adolescent's blood pressure should take into account his or her stage of sexual maturation and body size. A consideration of growth and maturation may contribute to studies of the natural history of blood pressure.

Tracking and prediction of blood pressure in children

A significant but weak correlation between an initial and a subsequent blood pressure measurement in the same patient has been found in several previous longitudinal studies of blood pressure in children. In the current study, single determinations of blood pressure, weight, and height were recorded in 142 children at 5.9 to 9.5 years of age and again 9 years later. Both examinations were performed in a schoolroom. Body size at the first examination was associated with body size 9 years later. A significant correlation was noted between initial and subsequent raw systolic blood pressures (r = 0.36 in boys and in girls; P less than 0.01). Correlations of systolic blood pressure based on percentiles for age and for height and weight were smaller but also statistically significant. Correlations involving diastolic blood pressure, with use of raw blood pressure measurements, were significant only for boys (r = 0.24, P less than 0.05). Correlations were not improved when indices of body size were used. Single blood pressure measurements obtained under the usual conditions in a schoolroom had only slightly weaker correlations with subsequent blood pressure determinations than those obtained in studies in which considerable care was taken to achieve more "basal" measurements. This degree of blood pressure correlation is insufficient to allow accurate prediction of subsequent blood pressure levels on the basis of a single casual blood pressure measurement in an individual child. This result was indicated by a wide 95% confidence interval for the predicted subsequent systolic blood pressure, even when sex, initial diastolic blood pressure, weight, and change in weight were considered.

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.

Issues in the pharmacologic management of primary hypertension in adolescence

Hypertension may occur in as many as 12% of adolescents and is usually of primary origin. There is an age-related increase of the blood pressure, making it difficult to define the limits of normal. True hypertension can be defined as blood pressure exceeding 140/90 mmHg regardless of age. Borderline blood pressure is said to exist when the blood pressure is above the 90th percentile for age. Blood pressure can be lowered with a wide variety of drugs, and adolescents are most often prescribed adult doses. There are specific concerns about the drugs' side effects in adolescents, particularly effects on growth and development, cognitive function, and metabolism. Diuretics are not the best first choice for therapy because of their metabolic effects. Cardiac hypertrophy and the morbidity of sustained hypertension are reduced by sympathetic inhibitors. Beta-blockers are the best currently available choice, although newer alpha-blocking agents may have some advantages. Even borderline pressure has been associated with evidence of cardiac hypertrophy, and there is substantial evidence that the adolescents with the highest blood pressures, even if still within normal limits, have the highest likelihood of developing sustained hypertension as adults. Yet there is no data establishing a beneficial effect on long-term risk of early treatment with drugs. For these reasons, nonpharmacologic intervention and close follow up are preferred as treatment for borderline blood pressure.

Blood pressure in puberty

The effects of sexual maturation, height, weight, body mass index, triceps skinfold and heart rate on systolic and diastolic blood pressure were studied among 13-year-old children in North Karelia, Eastern Finland. Cross-sectional and two-year longitudinal data were analyzed for 851 children in the six schools participating in the North Karelia Youth Project. In boys, the levels of both systolic and diastolic blood pressure increased during puberty. In girls, the level of systolic blood pressure did not change, but diastolic blood pressure increased as much as in boys. The change in systolic blood pressure was found to be associated with physical growth and stage of sexual maturation. Physical growth seemed to contribute more to the change in the level of systolic blood pressure than the stage of sexual maturation did.

Electrolytes and blood pressure levels in childhood hypertension: measurement and change

Research into the relationship between dietary electrolytes and the primary cause and treatment of hypertension has now reached the stage where long-term, detailed, controlled, randomized, clinical trials of intervention need to be carried out among those at high risk, including children. Such trials must incorporate methods for estimating "sensitive" responders. The designs should also include precise measures of change in dietary electrolyte intake and allow for analysis of interaction of the effects of individual electrolytes. We have sketched the unforeseen errors, that now must be avoided, from earlier studies and given an outline of a current study that sets out to meet optimum requirements. It is to be hoped that many similar studies will soon be initiated in multiple population groups.

Interpretation of children's blood pressure using a physiologic height correction

In a cross-sectional survey of 1834 black, Atlanta schoolchildren we corrected the customary blood pressure (BP) observations for the height of the arterial column extending from the BP cuff to the top (vertex) of the subject's head. Each cuff-to-vertex height was converted to its pressure equivalent in mmHg; then this pressure was subtracted from the observed BP to compute vertex-corrected BP values. The vertex-corrected mean arterial pressure (VMAP) ranged from 22.3 to 83.2 mmHg, but there was no estimated linear association between VMAP and age. For males, mean VMAP was 49.4 mmHg for ages 6-13 and 46.0 mmHg for ages 14-17. For females, mean VMAP was 50.2 mmHg for ages 6-17. Since VMAP appears to be independent of age in most of childhood, its use may simplify the development of pediatric BP reference values. VMAP can also serve as a non-invasive approximation of cerebral perfusion pressure. Investigators of primary hypertension may wish to use VMAP for comparing average BP levels between childhood groups which differ by potentially etiologic characteristics.

Acute postural change--a novel approach to blood pressure tracking in children

Among 1443 children, aged 5 to 18, followed for five consecutive years, we identified 68 who tracked consistently in the lowest blood pressure (BP) quartile and 114 in the highest. BP and corresponding heart rate were taken with subjects in the supine, sitting and erect postures. BP quartiles were established for each height category. Children consistently in the highest BP quartile had greater relative weight and higher heart rates in all three positions. On assuming the erect posture, children in the lowest BP quartile showed an increase in systolic BP, while those in the highest BP quartile showed a decrease. Both groups showed an increase in diastolic BP. On assuming the erect posture, subjects in the two groups showed no difference in heart rate change; subjects in the highest BP quartile did not show the additional reflex increase in heart rate to be expected in response to the decrease in systolic blood pressure. This combination of BP and heart rate findings suggests a subtle change in the baroreceptor reflex.

Personality, behavior, family environment, family social status and hypertension risk factors in children. The Minneapolis Children's Blood Pressure Study

To assess the relationship of psychosocial variables to risk factors for hypertension in children, we administered instruments designed to measure aspects of children's personality, behavior, family environment and family social status to 1505 school children aged 7-10 years. Children's blood pressure was significantly related only to mother's occupation, the children of unskilled employees having higher blood pressure than children of higher status workers. Children's body mass index was directly related to scores on the conformity scale of the personality inventory and inversely related to scores on the intellectual-cultural orientation scale of the family environment instrument and to social class. Social status but not measured dimensions of children's personality, behavior and family environment may influence the risk of hypertension in children.

Determinants of blood pressure in Jerusalem schoolchildren

In 1982, 113 first- and second-graders attending an elementary school in West Jerusalem had their blood pressure (BP), height, weight, and resting pulse measured. Three successive BP readings were taken. The mean of the second and third readings was used for data analysis. Mean systolic blood pressure (SBP) was 98.30 +/- 8.51 mm Hg and mean diastolic blood pressure (DBP) was 67.63 +/- 6.85 mm Hg. An analysis of covariance was performed in order to determine the contribution of each independent variable (height, weight-for-height, sex, age, and resting pulse) to the variance in BP, while adjusting for all other independent variables. Height, weight-for-height, and resting pulse were all found to be significantly associated with both SBP and DBP. Children in the upper quartile of weight-for-height had a mean adjusted SBP that was 10.2 mm Hg higher than those in the lower quartile and a mean adjusted DBP that was 7.9 mm Hg higher. Children in the upper quartile of height (for age) had mean adjusted SBP and DBP that were 6.1 and 4.7 mm Hg higher, respectively, than those of children in the lower quartile. Sex and age showed no significant association with SBP. The associations between DBP and both sex and age were not statistically significant (P less than 0.10), but there was a trend for girls and older children to have a slightly higher DBP. In a subsample of 93 children who had both resting pulse and recovery index measured (using the Modified Harvard Step Test for children).(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of hypertension in children

This article does not consider the secondary causes of high blood pressure in children. Essential hypertension is a major factor in the morbidity and mortality from cardiovascular disease among adult populations throughout the world. The possibility that a raised blood pressure may have its origins in childhood or even in infancy is being extensively explored. Accurate measurement of blood pressure--especially systolic--is now feasible, by the Doppler technique, in very young children. The concept of "tracking" of blood pressure has been investigated. In addition, factors such as familial aggregation, genetic aspects, and the role of obesity in the etiology of hypertension have been considered. The reason for differences in the severity of manifestation of hypertension in black and white populations has not been satisfactorily elucidated, despite a number of childhood population studies. With an increased number of blood pressure measurements more children are being discovered with labile or even essential hypertension. The exact level above which to consider therapy is somewhat controversial. Nevertheless, even with mild persistent elevations, nonpharmacologic measures such as control of obesity, reduction in salt intake, regular exercise, potassium supplementation, and relaxation therapy, seem warranted. These measures should also be seriously considered in the prevention of hypertension in young urban populations.

Health hazards of obesity and weight control in children: a review of the literature

A review of the literature on the health hazards of obesity and weight control in children indicates: 1) methodological flaws tend to invalidate the assumption that obesity is a risk factor for this age group; 2) weight control by children and adolescents may cause a variety of health problems including retardation of growth, development, mental functioning, and reproductive capacity; and 3) preoccupation with weight control in this society makes it likely that weight control-related-health problems are common phenomena. Further research into the short and long-term consequences of obesity and weight control is necessary before enlightened clinical practice in this area is possible.

Indices of obesity and blood pressure in young men followed 32 years

In order to assess the effects of baseline indices of obesity, lean body mass, blood pressure, and weight change on future blood pressure, 112 former college men were examined 20 and 32 years after initial examination at age 20.5 (+/- 2) yr. Baseline body weight, relative body weight, body mass index and body density all showed similar significant correlations with baseline systolic blood pressure (r = 0.35, 0.31, 0.30 - 0.31) but not baseline diastolic blood pressure (r = 0.13, 0.07, 0.10 - 0.11) or follow-up blood pressure. Changes in body weight, relative body weight, body mass index and sum of skinfolds were significantly correlated with change in both systolic and diastolic blood pressure. Baseline systolic blood pressure was the most powerful predictor of 20- and 32-yr follow-up systolic (r = 0.57, 0.42), but baseline diastolic was a much weaker correlate of follow-up diastolic blood pressure (r = 0.24, 0.18).