Body size, composition, and fitness in adolescents with elevated blood pressures

The relationship between body composition and blood pressure among primary school children in Eastern Cape province, South Africa

Background

In South Africa, especially in the Eastern Cape province, despite reported high prevalence of underweight and obesity, little is known regarding the relationship of body composition (BC) with blood pressure (BP) in primary school children. Understanding the relationship between BC and BP in these children is important because it is associated with adverse effects on health and social repercussion in both adolescence and adulthood.

Aim

The aim of this study was to examine the relationship between BC and BP among South African primary school children.

Setting

This study was conducted on a cohort of primary school learners in the Eastern Cape Province of South Africa.

Methods

A school-based cross-sectional survey was conducted among 876 school children aged 9–14 years, using multistage sampling techniques. Body mass and stature were measured using a calibrated scale. Anthropometric measurements including weight, height, waist circumference, triceps, gluteal and subscapular were also collected. Body mass index, percentage body fat and waist-to-hip ratio were calculated.

Results

Of the 876 participants, 356 (40.6%) were boys and 520 (59.0%) were girls. The Spearman’s rho correlation coefficients revealed positive significant correlations between systolic BP with age (r = 0.171; p < 0.0001), stature (r = 0.205; p < 0.0001), weight (r = 0.277; p < 0.0001), body mass index (r = 0.243; p < 0.0001), waist circumference (r = 0.259; p < 0.0001), gluteal (r = 0.214; p < 0.0001), triceps (r = 0.203; p < 0.0001), subscapular (r = 0.167; p < 0.0001), body fat percentage (r = 0.206; p < 0.0001), fat mass (r = 0.257; p < 0.0001) and fat-free mass (r = 0.238; p < 0.0001). There was no statistically significant correlation between waist-to-hip ratio and systolic BP (r = 0.064; p = 0.059). In terms of diastolic BP, there existed no significant correlations with age (r = 0.026; p = 0.443) and waist-to-hip ratio (r = 0.002; p = 0.947). Collectively, the prevalence of hypertension was 76.4% in the normal group compared with those who were pre-hypertensive (18.4%) and hypertensive (5.3%). Girls showed a higher prevalence of pre-hypertension than boys (19.6% compared with 16.6%, respectively).

Conclusion

There is a relationship between most of the BC variables and BP in children. The screening of BP as part of physical examinations of school children is necessary for early prevention and intervention programmes for hypertension.

Association of different obesity indices with blood pressure and blood lipids in children and adolescents

The aim of the present study was to compare individual associations of BMI, triceps skinfold (TSF), waist circumference (WC) and percentage fat mass (%FM) with blood pressure (BP) and blood lipids in children and adolescents. Cross-sectional data on BMI, TSF, WC, %FM as well as on BP, TAG and HDL were analysed in 4220 (BP) and 729 (lipids) 9–11-year-old children and 3174 (BP) and 536 (lipids) 13–16-year-old adolescents as part of the Kiel Obesity Prevention Study. All obesity indices were similarly associated with BP and blood lipids. In girls, WC had closer correlations to BP than BMI (systolic BP: 0·27 and 0·24 for BMI, 0·34 and 0·28 for WC in 9–11- and 13–16-year-olds). Subjects with an obesity index ≥ 90th percentile had higher prevalences of elevated BP and blood lipids than subjects with a normal index. In children with normal BMI or WC, an additionally elevated second obesity index was associated with a 2·5–7·4-fold higher prevalence of high BP when compared with children with normal indices. In adolescents, an elevated WC plus an elevated second obesity index was associated with a 2·6–8·2-fold higher prevalence of high BP when compared with adolescents with an elevated WC plus a normal second index. We conclude that (i) both BMI and WC are appropriate to estimate CVD risk, (ii) the use of a second obesity index is recommended in children with normal BMI or normal WC as well as in adolescents with elevated WC and (iii) all obesity indices seemed to be appropriate for risk assessment.

Relationship between body composition and blood pressure in Bahraini adolescents

The objective of the present study was to examine the relationship between body composition and blood pressure (BP) in Bahraini adolescents. A sample of 504 Bahraini schoolchildren aged 12–17 years (249 boys and 255 girls) was selected using a multi-stage stratified sampling procedure. BP measurements were performed on the students. Anthropometric data including weight, height, waist circumference (WC), hip circumference, and triceps, subscapular and medial calf skinfold thicknesses were also collected. BMI, percentage body fat, waist:hip (WHR), and subscapular:triceps skinfold ratio were calculated. Mean systolic BP and mean diastolic BP were higher in males than in females. Weight and height in boys and weight only in girls were significantly associated with systolic BP independent of age or percentage fat. Nearly 14% of the adolescents were classified as having high BP. BMI and percentage body fat were significantly and positively associated with the risk of having high BP in the boys and girls. Adolescents with high WHR or WC, as indicators for central obesity, tended to have higher BP values. The results from the present study indicate that obesity influences the BP of Bahraini adolescents and that simple anthropometric measurements such as WHR and WC are useful in identifying children at risk of developing high BP. These findings together with the known tracking of BP from adolescence into adulthood underline the importance of establishing intervention programmes in order to prevent the development of childhood and adolescent obesity.

Blood pressure in adolescence and early adulthood related to obesity and birth size

OBJECTIVE

Obesity is an established risk factor for higher systolic (SBP) and diastolic (DBP) blood pressure in adolescence and early adulthood, but birth size may also have a role. We analyzed the effects of adolescent and adult obesity and birth size on BP in the young adult.

RESEARCH METHODS AND PROCEDURES

In a prospective longitudinal study, anthropometric measurements were obtained at birth on 67 boys and 67 girls born in Boston. Their body mass indices (BMI) and BP were recorded 17 years and 30 years later.

RESULTS

For women, adolescent and early adult obesity appeared to be the stronger determinants of higher BP, although smaller head and chest circumferences at birth may also be related. We found some evidence of birth (ponderal index [PI] and head circumference) anthropometric influences on age 17 BP levels in boys. By age 30, body mass variables were the dominant predictors of male BP levels. Female BMI at age 17 was positively correlated with birth adiposity (PI), but BMI at 30 was related only to age 17 BMI. Similarly, male BMI at 17 years was higher for those who weighed more at birth, but BMI at 30 years was again related only to age 17 BMI.

DISCUSSION

We conclude that adult weight and weight gain are the major determinants of adult BP.

Genetic regulation of hemodynamic variables during dynamic exercise. The MCV twin study

BACKGROUND

Both resting and exercise levels of blood pressure in individuals have been used as predictors of adult hypertension. One possible mechanism underlying the relation between childhood resting and exercise blood pressure and future blood pressure is a set of genes expressed in childhood that persists to regulate adult blood pressure.

METHODS AND RESULTS

To investigate the genetic relation of blood pressure and heart rate during both rest and exercise, we asked: (1) Are the genes that regulate resting hemodynamic variables the same genes that regulate these variables during exercise? (2) How much of the variance in exercise hemodynamic variables is genetic and how much is environmental? (3) Do the genetic and environmental influences on hemodynamic responses change with increasing levels of exercise? To determine how genetic and environmental effects expressed at rest influenced responses during dynamic exercise, a genetic analysis was conducted by fitting a series of models to the covariance matrices with the use of the LISREL VII program.

CONCLUSIONS

We found that all the genetic effects expressed at the later stages of exercise can be explained by genetic effects expressed at rest and at the first stage of exercise. The environmental effects appear to be workload specific and include errors of measurement.

The relationship between the intrauterine environment and blood pressure in 3-year-old Japanese children

In 195 Japanese children the systolic pressure at 3 years of age was inversely correlated to the body weight at birth and positively correlated to the mothers' systolic pressure during pregnancy: the average systolic pressure in children whose body weight at birth exceeded 3510 g was 3.0 mmHg, which was lower than that of children whose body weight at birth was 2990 g or less. There was an increase of 0.12 mmHg in the children's systolic pressure with each increment of 1 mmHg in the systolic pressure of their mothers. The systolic pressure at 3 years in children of mothers who had had pretibial oedema during pregnancy (101.0 +/- 8.8 mmHg) was significantly higher compared with children whose mothers did not have oedema (96.6 +/- 9.6 mmHg).

Correlates of blood pressure in Seventh-Day Adventist (SDA) and non-SDA adolescents

OBJECTIVE

This comparative study was designed to discover early determinants of systolic (S) and diastolic (D) blood pressure (BP) elevations in 138 Seventh-Day Adventist (SDA) and 89 non-SDA male and female adolescents (median age, 17 years) living at three residential secondary schools in North Carolina.

METHODS

Measurements were made of blood pressure, body weight, and height, and information was collected on lifestyle factors, dietary intake, and other behaviors, including exercise, religiosity, Type A behavior, and anger, by questionnaire. Multiple stepwise regression analyses were performed with BP, either SBP or DBP, as the independent variable.

RESULTS

A significant direct association was found only between body weight and BP, but weak associations were shown between BP and other variables, including exercise, diet, religiosity, Type A behavior, and anger. Male and female SDA students showed significantly higher SBPs and DBPs than did non-SDA adolescents though the differences were small (approximately 5 mm for each sex).

CONCLUSIONS

These findings suggest that the higher BP values of SDA adolescents, who were all practicing lacto-ovo-vegetarians, compared to similarly aged health-conscious non-SDAs, are determined more by eating behaviors that contribute to gains in body weight than by any other lifestyle variable. Furthermore, these data support the notion that the BP-protective effects of the vegetarian diet may not emerge in these SDA youth until early adulthood.

Pre-eclampsia and offspring's blood pressure, cognitive ability and physical development at 17-years-of-age

OBJECTIVE

To investigate the influence of maternal pre-eclampsia on the blood pressure, physique and intelligence of the offspring at the age of 17 years.

DESIGN

Data obtained at the age of 17 during assessment for drafting to the Israel Defence Forces and from the records of the mothers' pregnancies from the Jerusalem Perinatal Study.

SUBJECTS

Study subjects were 145 girls and 283 boys whose mothers had had pre-eclampsia and controls were 12,701 girls and 20,416 boys whose mothers did not have pre-eclampsia.

MAIN OUTCOME MEASURES

Systolic and diastolic blood pressure, weight, height and intelligence scores at the age of 17 were related to birthweight and the occurrence of pre-eclampsia during their mothers' pregnancies.

RESULTS

Systolic blood pressure was greater than 140 mmHg in 6.9 and 11.0% of the study girls and boys, compared with 2.9 and 9.9% of the control girls and boys. The study boys but not the girls had a higher mean body mass index than the controls (P less than 0.001). There were no differences in the intelligence scores. Using multiple logistic regression to allow for the confounding effects of body mass index, weight and birthweight, the odds ratio for the risk of a systolic pressure greater than 140 mmHg was 2.30 (95% CI 1.80-4.46) for the study girls but was not significantly increased for the study boys.

CONCLUSION

Maternal pre-eclampsia does not impair growth and cognitive performance in the children who reach late adolescence but may be associated with hypertension.

Birth weight, current body weight, and blood pressure in late adolescence

Objective--To study the effect of birth weight and body weight on blood pressure in late adolescence. Design--Analysis of data on weight, height, and blood pressure at age 17 of subjects from the Jerusalem perinatal study, according to their birth weight. Data for men and women were analysed separately. Setting--Jerusalem, Israel. Subjects--32,580 subjects (19,734 men and 12,846 women) born in the three major hospitals in Jerusalem during 1964-71 and subsequently drafted in to the army. MAIN OUTCOME MEASURES--Correlations between birth weight and blood pressure at age 17 and weight and height at age 17 and blood pressure. Results--Diastolic and systolic blood pressures were associated with birth weight in both young men and young women, but the correlation coefficients were low. A high body weight at age 17 (greater than 66 kg for women, greater than 75 kg for men) rather than a low birth weight (less than 2500 g) was linked with higher systolic and diastolic blood pressures in both men and women (p less than 0.01). Conclusions--Intrauterine environment, as reflected by birth weight, has little effect on blood pressure in young men and women. Modification of factors which lead to excess weight during adolescence may have a major role in preventing hypertension in adults.

Relation of serum and erythrocyte magnesium levels to blood pressure and a family history of hypertension. A follow-up study in Japanese children, 12-14 years old

Serum and erythrocyte magnesium concentrations (S-Mg, E-Mg) were measured in 122 junior high school students followed up for two years from 12 to 14 years of age, and the relationship to blood pressure and a family history of hypertension were investigated. The subjects who had high S-Mg and E-Mg levels at the first examination two years prior tended to show high levels after this follow-up. There were significant positive correlations between two intraindividual values of S-Mg and E-Mg. A similar tendency was found for blood pressure. Tracking phenomena were observed with these measures. The subjects who had high E-Mg levels at the first examination showed no blood pressure elevation during the two-year period. The subjects with a family history of hypertension [FH(+)] showed a higher degree of blood pressure rise during two years than those with no family history [FH(-)], with a significant difference in systolic blood pressure at the age of 14. E-Mg tended to be lower in the FH(+) group than in the FH(-) group with a significant difference in 14-year-old girls. These results suggest that a hereditary predisposition to hypertension is related to magnesium metabolism and that intracellular magnesium deficiency may influence blood pressure elevation in the FH(+) children.

The relationship of treadmill test performance to blood pressure and other cardiovascular risk factors in adolescents

Associations between treadmill test performance, blood pressure, and other cardiovascular risk factors in over 6000 adolescents, aged 12 to 17 years, were examined with data from the third cycle of the National Health Examination Survey. Exercise tolerance was measured by a 5-minute submaximal treadmill test. Estimated VO2 increased with age in boys but decreased with age in girls. VO2 was higher in boys than girls and similar in black and white subjects. Exercise heart rate was significantly correlated with blood pressure in white boys and girls and with obesity in white and black persons. A small but significant association between exercise heart rate and systolic blood pressure was demonstrated in white boys and girls independent of age and obesity. Aerobic exercise may be useful in adolescents for prevention of adult hypertension by means of obesity control and improved cardiopulmonary fitness.

Prevalence of "significant" hypertension in junior high school-aged children: the Children and Adolescent Blood Pressure Program

Blood pressure (BP) data obtained during a BP screening program were analyzed to determine the prevalence of "significant" hypertension, defined by the Second National Heart, Lung, and Blood Institute Task Force on Blood Pressure Control in Children-1987 as the level of BP above which medical evaluation and intervention are recommended. In 14,686 black and white St. Paul and Minneapolis schoolchildren aged 10 to 15 years, BP was measured twice during an initial screening examination. Children with systolic BP in the upper 30 percentiles of distribution after the initial screening had their BP remeasured two additional times at a rescreening examination. The prevalence of significant hypertension was determined according to BP criteria established by the Task Force report. After the two screening BP measurements were averaged, significant systolic hypertension was found in 1.0%, significant diastolic hypertension in 3.5%, and significant systolic or diastolic hypertension, or both, in 4.2% of the students. After the rescreening examination, the percentage of students remaining with significant hypertension was reduced to 0.3% for systolic, 0.8% for diastolic, and 1.1% for systolic or diastolic hypertension, or both. These results show that significant hypertension is uncommon in pre-high-school students and confirm the need for repeated BP measurements to make an accurate diagnosis of hypertension. However, the results should not detract from current recommendations to monitor BP in children on a yearly basis to detect longitudinal BP tracking patterns that may be consistent with early essential hypertension.

Body fat patterning and blood pressure in children and young adults. The Bogalusa Heart Study

The relationship of central body fat (measured by subscapular skinfold) and peripheral body fat (measured by triceps skinfold) to blood pressure was investigated in 3784 subjects aged 5 to 24 years old from the biracial community of Bogalusa, Louisiana. After adjustment for height, age, sex, and race, significant relationships were found for both central body fat (r = 0.19 and 0.14, p less than 0.0001) and peripheral body fat (r = 0.15 and 0.12; p less than 0.0001) with systolic and diastolic (fourth phase) blood pressure, respectively. However, the relationship between peripheral body fat and blood pressure, after controlling for the level of central body fat, was negligible (r = 0.00 and 0.01 for systolic and diastolic blood pressure, respectively). In contrast, the central body fat-blood pressure relationship remained statistically significant even after controlling for the peripheral body fat level. For central body fat, the partial correlations with systolic blood pressure were highest in young children (r = 0.15), dropped slightly during adolescence (r = 0.12), and became nonsignificant only in 18- to 24-year-old female subjects; correlations remained high in both black and white 18- to 24-year-old male subjects (r = 0.18 and 0.16, respectively). Mean levels of systolic blood pressure from the lowest to the highest quartile of central body fat ranged from 100.4 to 108.9 mm Hg. The adult hypertension-central body fat relationship, which has been shown by others, appears to exist in children. Continued efforts at early identification and prevention of obesity in children are warranted.