Relationship between age, body size, gender, and blood pressure and Doppler flow measurements in the aorta and pulmonary artery

Previous studies have demonstrated a relationship between both age and body surface area (BSA) and M-mode echocardiographic measurements of left ventricular, left atrial, and aortic root dimensions and left ventricular wall thickness. We evaluated the relationships between age, BSA, gender and blood pressure, and Doppler aortic and pulmonary artery (PA) flow velocity measurements in 97 adults, aged 21 to 78 years, without clinical evidence of cardiac disease. No significant relationship was found between gender or blood pressure and aortic or PA flow velocity measurements. Aortic peak flow velocity, flow velocity integral, and average acceleration decreased with increasing age (all p less than 0.001), whereas ejection time (corrected for heart rate) increased, and acceleration time did not change. In contrast, there was no relationship between age and Doppler PA flow velocity measurements. Although there was no relationship between BSA and Doppler aortic flow measurements, PA peak flow velocity and average acceleration increased, while acceleration time decreased with increasing BSA (all p less than 0.02). Decreases in aortic peak flow velocity and flow velocity integral may be partly related to known increases in aortic root diameter with aging. The relationship between PA flow velocity measurements and BSA is not readily explained.     

The relationship between gestational age, systolic blood pressure and pulse pressure in children

This cross-sectional study investigates the relationship between gestational age and systolic blood pressure and pulse pressure in childhood. Blood pressure was measured in 483 schoolchildren, free from cardiovascular disease, aged between 6 and 16 years. Pulse pressure was estimated as the difference between the 24-h mean systolic and diastolic blood pressure values. Linear regression showed an inverse relationship between gestational age and mean 24-h systolic blood pressure (adjusted regression coefficient mm Hg per week gestation -0.631, 95% confidence interval (CI) -1.21 to -0.04, P=0.036). Further, linear regression showed a significant negative association between gestational age and log-transformed pulse pressure (adjusted antilog regression coefficient mm Hg per week of gestation -1.39, 95% CI -2.96 to -0.3, P=0.013), which after gender-specific analyses was found to be restricted to the girls in the study. The results of the present study suggest that low gestational age is associated with elevated systolic blood pressure and pulse pressure in childhood, the latter particularly in girls. This observation provides some support for the developmental origins of adult disease hypothesis-that adverse events in early life may have long-term consequences for cardiovascular health. However, as gestational age itself is unlikely to be the causal event in determining blood pressure control, further investigation is required, particularly with regard to the nutritional, physiological and molecular mechanisms that explain such epidemiological observations.     

Racial differences in the influence of body size on ambulatory blood pressure in youths

BACKGROUND: African Americans have higher night-time blood pressures than Caucasians do despite their having similar daytime blood pressures. It is well established that body size is related to casual blood pressure. OBJECTIVE: To examine the influence of body size on racial differences in patterns of ambulatory blood pressure. METHODS: Ambulatory blood pressure recordings were performed on 292 healthy children and adolescents (148 African Americans and 144 Caucasian) aged 10-18 years (mean 13+/-2 years). These blood pressures were related to height, weight, body surface area, and body mass index in separate regression models that also included race, sex, and age as factors. RESULTS: The race-by-height interaction was significant for night-time systolic blood pressure (P<0.02), with a significant relationship for African Americans (P<0. 0001), but not for Caucasians. The race-by-weight interaction was significant for night-time systolic blood pressure (P<0.04), also with a greater relationship for African Americans (P<0.0001) than for Caucasians (P<0.03). In addition, the race-by-weight interaction was significant for night-time diastolic blood pressure (P<0.04), with a significant relationship for African Americans (P<0.01), but not for Caucasians. Finally, the race-by-body-surface-area interaction was significant for night-time diastolic blood pressure (P<0.05), again with a significant relationship for African Americans (P<0.02) but not for Caucasians. CONCLUSION: Differences in the relationship between body size and blood pressure contribute to the racial differences in patterns of ambulatory blood pressure and should be considered when evaluating patterns of blood pressure in African American youths.     

Influence of body composition, hemoglobin concentration, and cardiac size and function of gender differences in maximal oxygen uptake in prepubertal children

OBJECTIVE: To determine the relative contribution of the gender difference in body composition, blood hemoglobin concentration, and cardiac dimension and function at rest and exercise of the gender difference in maximal oxygen uptake (O(2)max) in 10- to 12-year-old children. SUBJECTS: Thirty-five healthy children (17 girls and 18 boys; mean +/- SD age, 10.5 +/- 0.4 years). Experimental design: An anthropometric evaluation (body surface area, body fat content, and lean body mass [LBM]), assessment of hemoglobin concentration, echocardiographic evaluation at rest (left ventricular dimensions, and diastolic and systolic indexes at rest), and cardiovascular evaluation during a maximal cycle exercise (stroke volume [SV], total peripheral resistance). RESULTS: The boys exhibited a higher mass-relative O(2)max than the girls (47.9 mL/kg/min vs 40.9 mL/kg/min, respectively); but when normalized for LBM (allometric equation), the difference totally disappeared (19.0 mL/kg LBM(1.33)/min vs 18.9 mL/kg LBM(1.33)/min, respectively). No significant gender differences were seen in maximal heart rate and arteriovenous oxygen difference; however, maximal SV (SVmax) was significantly higher in boys than in girls, but when expressed relative to LBM, the difference was no longer significant. CONCLUSIONS: These findings demonstrate that contrary to adults, the sole limiting factor of O(2) that distinguished boys from girls was a lower SVmax in the latter; however, this gender difference totally disappeared when normalized for LBM. Consequently, the gender difference in heart size and cardiac function during exercise should be interpreted as only one aspect of the lower LBM in girls and not as reflective of a more basic functional gender difference.     

Sexual differences in relationships between birth weight or current body weight and blood pressure or cholesterol in young Japanese students.

This study was designed to examine the relationships between birth weight or current body weight and blood pressure (BP) or cholesterol in 178 Japanese high school students (98 male, 80 female, age 15-16 yr). All subjects were born after a full-term pregnancy (gestational age > or = 38 wk) with a birth weight > or = 2,500 g; these data were obtained from routine obstetrical records. At a health check-up, nurses used an automatic device to perform two consecutive BP measurements with each subject in a sitting position after resting for at least 5 min. Serum total and high-density lipoprotein (HDL) cholesterol levels were measured. Birth weight was not related to BP, but was inversely related to serum total cholesterol in both males (r= -0.241, p < 0.05) and females (r= -0.351, p < 0.01). Current body weight was significantly related to systolic BP (r=0.369, p<0.01), diastolic BP (r=0.216, p<0.05), and HDL cholesterol level (r= -0.224, p < 0.05) in males, but not in females. Although no relationship was demonstrated between birth weight and BP level in young Japanese students without intrauterine growth retardation, an inverse relationship between birth weight and serum total cholesterol level was found. There was a gender difference in the relationship between current body weight and either BP or HDL cholesterol in these subjects.     

Association between blood pressure and resting energy expenditure independent of body size

Obesity is an important risk factor for hypertension; however, the pathway through which it raises blood pressure (BP) is poorly understood. Body size is also the primary determinant of energy expenditure, and we therefore examined the joint relationship of energy expenditure and body size to blood pressure. Resting energy expenditure (REE) was measured using respiratory gas exchange in population-based samples of 997 Nigerians and 452 African Americans. In a third sample of 118 individuals, nonresting energy expenditure (ie, physical activity) was measured in addition to REE. The univariate correlation between REE and BP ranged from 0.10 to 0.22 in the 3 samples (P<0.001). In multivariate models, adiposity, whether defined by body mass, fat mass, or leptin, was no longer associated with BP, while REE remained highly significant (P<0.001). The REE-BP association also persisted after adjustment for physical activity measured with doubly labeled water. The odds ratio for hypertension among persons in the highest quartile versus the lowest quartile of REE, after adjustment for body size, was 1.7. This relationship was not the result of hypertension among the obese, because it did not vary across the range of BMI and was the same in lean Nigerians as in obese Americans. These data suggest that metabolic processes represented by REE may mediate the effect of body size on BP. The interrelationship of REE with sympathetic tone, transmembrane ion exchange, or other metabolic processes that determine energy costs at rest could provide physiological explanations for this observation.     

Hormonal influences on the relationships between body fatness, body fat distribution, lipids, lipoproteins, glucose and blood pressure in French working women

The independent associations between overall obesity, body fat distribution, lipids, lipoproteins, glucose, blood pressure and some hormonal factors (sex hormone-binding globulin (SHBG), corticosteroid binding globulin (CBG) and fasting insulin) were cross-sectionally examined in 205 French working women. After adjustment for age, overall adiposity assessed by body mass index (BMI) was significantly associated with most metabolic parameters, whereas regional adiposity assessed by the waist-hip ratio (WHR) was significantly associated only with triglyceride, systolic and diastolic blood pressure. Blood pressure, glucose but not triglyceride, were also negatively and significantly correlated with SHBG and positively with fasting insulin. Negative independent associations were found between SHBG and both BMI and WHR, whereas CBG was positively associated only with WHR. Fasting insulin was no longer related to WHR after adjustment for BMI. After controlling for the effect of SHBG or insulin, the associations between triglyceride, blood pressure and both BMI and WHR were not substantially modified. After adjustment for BMI and WHR, fasting insulin was independently associated with both HDL cholesterol and diastolic blood pressure. In conclusion, in these French women, hormonal factors under study appeared to have little influence on the relationships between body fatness, body fat distribution, metabolic variables and blood pressure.     

Serum lipids, blood pressure and body weight around the age of the menopause

BACKGROUND: Of previous studies, some have indicated an adverse development of serum lipids, blood pressure and body weight in women around the menopause. We sought to study these associations in data collected before the widespread use of lipid lowering drugs and hormone therapy. DESIGN: Population-based cohort study. METHODS: We analysed data from population-based cardiovascular surveys in Norway. During 1985--1988, all women aged 40-54 years in three counties were invited, 83% participated and 24,085 nonusers of hormone therapy were studied, of whom 12,736 had attended similar surveys 5 and 10 years earlier (1974--1978 and 1977--1983). Serum lipids, blood pressure, height and weight were measured, and menopausal status was registered by interview. Analyses were made in cross-sectional data and by comparing changes in serum lipids, body weight and blood pressure between the surveys according to menopausal exposure. RESULTS: Total cholesterol (TC), triglycerides and the TC/high-density lipoprotein (HDL)-cholesterol ratio increased from premenopausal to postmenopausal status. The HDL-cholesterol concentration seemed to increase slightly in the perimenopause. In women who had entered the postmenopausal phase most recently, the increases of TC and triglycerides since 5 years earlier were more than twice the levels of premenopausal women. The results were consistent in subgroups by age. Menopausal status was not associated with adverse development of blood pressure or body weight. CONCLUSION: The menopausal transition may be associated with an accelerated increase of TC and triglyceride concentrations and of the TC/HDL-cholesterol ratio.     

Correlation between age, body size and thyroid volume in an endemic area.

Ultrasound is a safe, non-invasive technique that provides a more precise and objective method of determining thyroid volume than inspection and palpation, particularly in areas of mild endemicity, and generally whenever goiters are small. Thyroid volume is also correlated with age, weight, height and body surface area (BSA) in non-iodine-deficient areas. Different authors prefer different parameters to assess thyroid gland volumes. In this study, thyroid volumes were determined using ultrasound in 605 school children aged 6-11 yr who had been living for at least 5 years in Antalya. The correlation between age, BSA, height, weight, BMI and thyroid volume was sought in this mild to moderate iodine-deficient area. Somatic development of our children was in the normal range. Thyroid volume was significantly correlated with age (r=0.41, p<0.001), height (r=0.33, p<0.001), weight (r=0.30, p<0.001), BSA (r=0.33, p<0.001), and BMI (r=0.13, p<0.001). The most significant correlation was found to be with age. The application of the International Council for Control of Iodine Deficiency Disorders (ICCIDD) and the World Health Organization (WHO) thyroid volume references to our subjects resulted in prevalence estimates of enlarged thyroid of 31% based on BSA and of 34% based on age. In conclusion, when thyroid volumes are to be compared with reference values, assessment of thyroid volumes based on age is the most reliable method, in the event of normal somatic development.     

Association between body composition and blood pressure in a contemporary cohort of 9-year-old children

Elevated blood pressure (BP) in children is an early risk factor for cardiovascular disease and is positively associated with body mass index (BMI). However, BMI does not distinguish between fat and lean masses, and the relationship of BP in children to different elements of body composition is not well established. BP, BMI and body composition were measured in 6863 children enrolled in the Avon Longitudinal Study of Parents and Children. Fat mass, lean mass and trunk fat were assessed using dual-energy X-ray absorptiometry. After full adjustment for confounders, total body fat and BMI were positively associated with systolic blood pressure (SBP) (beta=3.29, 95% confidence interval CI 3.02, 3.57 mm Hg/standard deviation (s.d.) and beta=3.97, 95% CI 3.73, 4.21 mm Hg/s.d., respectively) and diastolic blood pressure (DBP) (beta=1.26, 95% CI 1.05, 1.46 mm Hg/s.d. and beta=1.37, 95% CI 1.19, 1.54 mm Hg/s.d., respectively). SBP was also positively associated with lean mass (beta=3.38, 95% CI 2.95, 3.81 mm Hg/s.d.), and weakly associated with trunk fat (beta=1.42, 95% CI -0.06, 2.90 mm Hg/s.d., independent of total fat mass), which was robust in girls only. The association between lean mass and SBP remained even after accounting for fat mass. SBP in 9-year-old children is independently associated with fat mass and lean mass and, to a lesser extent, trunk fat in girls. In this analysis, because both fat and lean masses are associated with BP, BMI predicts BP at least as well as these components of body composition.     

The relationship between body weight and blood pressure

In adults of Western societies the positive relationship between blood pressure and body weight has often been demonstrated, both cross-sectionally and longitudinally. This correlation is even stronger in children and early adulthood. In most studies in children, the association between age and blood pressure disappears after controlling for weight. Association must be differentiated from causation. It has however been shown in several intervention studies that treatment of obesity by weight loss decreases blood pressure substantially both in hypertensive and normotensive subjects. Although combining results from several intervention trials is difficult this is the only practical way to get an overall estimate of the hypotensive response to be expected from weight reduction. In the randomised controlled intervention studies, conducted in obese hypertensive patients and reviewed in the present meta-analysis, a decrease in body weight by 1 kg resulted in a reduction of systolic and diastolic pressure by 1.2 and 1.0 mmHg, respectively. Blood pressure generally decreased before normal weight was achieved and remained reduced as long as there was no marked regain in body weight. Although a decrease in salt intake during dieting may contribute to the blood pressure lowering effect of weight reduction, also other mechanisms, such as a reduction in plasma renin activity and a decrease in sympathetic tone may also be involved.     

Insulin, adiponectin, IGFBP-1 levels and body composition in small for gestational age born non-obese children during prepubertal ages

Background Being small for gestational age (SGA) at birth and postnatal growth pattern may have an impact on insulin resistance and body composition in later life. Adiponectin is a strong determinant of insulin sensitivity. Objective The aim of this study was to evaluate insulin resistance and adiponectin levels in SGA born children with catch‐up growth (CUG) in the absence of obesity in prepubertal ages and relations with body composition and insulin‐like growth factor binding protein (IGFBP)‐1. Methods Twenty‐four (15F, 9M) SGA born children with CUG but without obesity were evaluated at age 6·3 ± 0·5 years with respect to glucose, insulin, IGFBP‐1, leptin and adiponectin levels, and body composition by dual‐energy X‐ray absorptiometry (DEXA). Their data were compared to that of 62 (27F, 35M) appropriate for gestational age (AGA) children. Results SGA and AGA children had similar height standard deviation score (SDS) corrected for parental height and body mass index (BMI) SDS. Homeostasis model for insulin resistance (HOMA‐IR) was significantly high in SGA (0·7 ± 0·6) than in AGA children (0·4 ± 0·2) (P = 0·029). There were no significant differences in leptin, IGFBP‐1, adiponectin, and total and truncal fat between SGA and AGA children. However, being born SGA and having higher BMI in the upper half for the distribution in the sample, although within normal ranges, was associated with lower adiponectin levels (estimated means of log adiponectin levels 3·8 ± 0·3 vs. 4·4 ± 0·1 µg/ml, P = 0·040). Conclusions SGA children with CUG and with no obesity have higher insulin levels compared to AGA children. Both SGA birth and recent size seem to have an effect on serum adiponectin levels in childhood.     

Relationships between plasma catecholamines, renin, age and blood pressure in essential hypertension

The aim of this study was to examine the interrelationships between age, plasma catecholamines, plasma renin activity (PRA) and blood pressure in essential hypertensive (EH) patients. PRA, plasma noradrenaline (NA) and adrenaline (A) were measured in 76 consecutive EH patients (WHO stages 1-2, aged 24-66 years) and in 28 normotensive subjects (aged 25-64 years) studied at rest in supine position after 5 days of normal fixed sodium and potassium intake. Both plasma NA and A were slightly but significantly higher in EH patients (p less than 0.05). While no relationship was found between the various parameters in normotensive subjects, in EH patients, particularly those at WHO stage 2, plasma NA was directly related to mean blood pressure (MBP) (p less than 0.001) and PRA (p less than 0.01). Plasma A was weakly related to MBP (p less than 0.05); PRA was inversely related to age (p less than 0.01) but no relationship was found between NA or A and age. Partial correlation analysis confirmed all these relationships. In fact, NA was related to MBP also considering constant PRA (p less than 0.001) or age (p less than 0.001), and NA was related to PRA also considering constant MBP (p less than 0.01) or age (p less than 0.001). Acute pharmacological alpha- and beta-blockade, with labetalol 100 mg i.v., induced a reduction of MBP which was directly related to basal plasma NA (p less than 0.001). These results support the view that in EH the sympathetic nervous system might be in part responsible for PRA levels and for the severity of hypertension.     

Gender differences in the relationship between left ventricular size and ambulatory blood pressure in borderline hypertension: The HARVEST Study

AIM: To assess whether there are gender differences in cardiac adaptationto raised blood pressure levels in young subjects with borderlineto mild hypertension. METHODS AND RESULTS: In 499 18–45-year-old stage I hypertensive subjects (377men and 122 women) with a mean age of 33±9 years andoffice blood pressure of 146±11/94±6 mmHg, ambulatoryblood pressure monitoring in duplicate, echocardiography and24-h urinary catecholamines measurement were performed. RESULTS: The whole group was divided into quartiles of increasing daytimeblood pressure and differences in left ventricular echocardiographicdata were analysed in the two sexes separately. In men no leftventricular parameter differed across the quartiles, while inwomen left ventricular mass, posterior wall thickness and interventricularseptum thickness showed a clear tendency to increase with increasinglevels of systolic blood pressure. In multiple regression analysis,daytime systolic blood pressure explained only a small fractionof the variance in left ventricular parameters in men, whilein women daytime systolic blood pressure was a main determinantof left ventricular mass and posterior wall and septal thicknesses.Body weight explained most of the variance in all dimensionalparameters in men. In women weight was an important predictorof left ventricular mass and diameter, but was unrelated toleft ventricular posterior wall and septal thicknesses. CONCLUSIONS: Daytime systolic blood pressure is the most important predictorof left ventricular mass and geometry in pre-menopausal womenwith stage I hypertension, while in men left ventricular dimensionalindeces are chiefly explained by body weight.     

Increased nocturnal blood pressure in healthy prepubertal twins

AIM: To compare ambulatory blood pressure monitoring (ABPM) in twin children to a published singleton population, and to examine the influence of birthweight and fasting plasma cortisol on blood pressure. DESIGN: A cross-sectional study of monozygotic and dizygotic twins compared with a similar previously published normative control population. METHODS: Forty-four healthy prepubertal twin children aged 4-11 years (20 monozygotic, 22 male) were studied. All subjects had 24-h ABPM and a fasting early morning plasma cortisol. RESULTS: Twins had higher 24-h systolic blood pressure (BP) compared with controls with similar daytime and elevated night-time systolic BP (P > 0.3 and P < 0.01, respectively). Twins had reduced systolic and diastolic nocturnal BP dipping compared with controls (P < 0.0001 for both), and 61% of twins exhibited a < 10% fall in nocturnal BP. In the twin cohort there was no association between birth weight and daytime systolic BP (P = 0.6), nor any other ABPM parameter. There was no difference in BP parameters between dizygotic and monozygotic twins, and no difference between the lighter and heavier birthweight twins for any ABPM parameter. Fasting plasma cortisol was not associated with either birthweight (P = 0.2) or daytime systolic BP (P = 0.4). CONCLUSIONS: Healthy prepubertal twins have increased nocturnal BP and reduced nocturnal BP dipping independent of zygosity or birthweight. These abnormalities may be a risk factor for the later development of hypertension in twins. As these BP abnormalities are not associated with twin birth weight, the twin model may not be appropriate in investigating the fetal origins of disease in later adult life.     

Effect of age and blood pressure on aortic size and stroke distance

The diameters of the ascending and descending aorta at the level of the carina were measured from computerised tomograms in 200 adults without cardiac or aortic disease. At all ages the ascending aorta had a greater cross sectional area than the descending aorta, and both areas increased significantly with age. The increase was proportionately greater in the descending than in the ascending aorta and the percentage changes were similar in males and females, the latter having a smaller mean descending aortic diameter. The extent of the increase in cross sectional area of the aorta is sufficient to explain the observed fall of stroke distance that occurs with age. The effect of changing blood pressure on aortic cross sectional area, and hence the relation between stroke distance and stroke volume, was calculated from published data on aortic compliance at different ages. Assuming constant peripheral resistance, stroke distance would change by 34, 82, and 94% for a 100% change of stroke volume at age 20, 50, and 80 respectively. At age 80 the aorta behaves like a rigid pipe but at age 20 its elasticity is such that constancy of aortic size cannot be assumed.