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

Components of height and blood pressure in childhood

BACKGROUND

In children being taller is associated with higher blood pressure (BP), but few studies have divided height into its components: trunk and leg length. We examined the associations of total height, trunk length and leg length with systolic BP (SBP), diastolic BP (DBP) and pulse pressure (PP) at early childhood and mid-childhood visits, as well as change between the two visits.

METHODS

We obtained five measures of SBP and DBP at the early childhood visit (N = 1153, follow-up rate = 54%) and at the mid-childhood visit (N = 1086, follow-up rate = 51%) respectively, in Project Viva, a US cohort study. We measured total height and sitting height (a measure of trunk length that includes head and neck) and calculated leg length as the difference between the two. Using mixed models, we adjusted the cross-sectional analyses for leg length when trunk length was the exposure of interest, and vice versa. We also adjusted for maternal race/ethnicity, child age, sex, overall adiposity and BP measurement conditions.

RESULTS

At the mid-childhood visit, total height was positively associated with SBP [0.34 (0.24; 0.45) mmHg/cm] but not with DBP [0.07 (-0.003; 0.15)]. In models examining trunk and leg length separately, each was positively associated with SBP [0.72 (0.52; 0.92) and 0.33 (0.16; 0.49) respectively]. In a fully adjusted model with both leg and trunk length, only trunk length remained associated with BP. For a given leg length, a 1-cm increment in trunk length was associated with a 0.63-mmHg (0.42; 0.83) higher SBP and a 0.17-mmHg (0.02; 0.31) higher DBP. For a given trunk length, however, the associations of leg length with SBP [0.13 (-0.03; 0.30)] and with DBP [0.002 (-0.11; 0.12)] were null. These patterns were similar at the early childhood visit.

CONCLUSIONS

Children with greater trunk lengths have higher BPs, perhaps because of the additional pressure needed to overcome gravity to perfuse the brain.

A population-based comparison of BMI percentiles and waist-to-height ratio for identifying cardiovascular risk in youth

OBJECTIVE

Determine whether waist-to-height ratio (WHtR) or sex- and age-specific percentiles of body mass index (BMI) better identifies cardiovascular risk.

STUDY DESIGN

The third National Health and Nutrition Examination Survey (NHANES III) provided measurements on 7657 participants statistically weighted to represent 50.05 million youth 4 to 17 years of age. We estimated the subpopulations corresponding to BMI strata that were normal (< 85th percentile), at risk for overweight (85th to <95th percentile), and overweight (> or =95th percentile). We chose WHtR cutoff points (0.490 and 0.539) so that subpopulation sizes in the three WHtR strata would equal those in the three BMI strata. For 13 cardiovascular risk factors we compared mean levels among youth discordant for their BMI and WHtR strata.

RESULTS

726 participants (representing 3.69 million youth) were identified as having WHtR stratum >BMI stratum. Compared with the 603 participants (representing 3.70 million youth) who were discordant in the opposite direction, weighted analyses showed they had higher mean levels of heart rate, low-density lipoprotein (LDL) cholesterol, fasting triglycerides, and total cholesterol ( P <.015, adjusted for sex, age, and race-ethnicity). Their mean systolic blood pressure was lower, but this difference was eliminated after adjustment for their shorter stature.

CONCLUSION

WHtR, a simpler anthropometric index than sex- and age-specific BMI percentiles, better identifies youth with adverse cardiovascular risk factors.

Blood pressure measurement in childhood epidemiological studies

BACKGROUND

Accurate measurement of blood pressure in childhood epidemiological studies requires standardized conditions, valid instruments, and multiple measurements.

METHODS AND RESULTS

We used published literature and our own data to make recommendations on the reduction of biases caused by various technical factors, to discuss the advantages and disadvantages of selected measurement devices, and to evaluate the optimal number of visits and measurements per visit for accurate estimation of a child's blood pressure level. The conditions under which blood pressure is measured should be standardized. This includes training and certification to minimize observer biases; equipment factors such as use of an appropriate cuff bladder size, subject factors such as minimizing activities before and during the reading, environmental factors such as accounting for the time of day and ambient temperature, and technique factors such as recording both the fourth and fifth Korotkoff sounds. The choice of instrument for measuring blood pressure depends on the goals of the study and the resources available to the investigators.

CONCLUSIONS

Although relatively economical and easy to use, the standard mercury sphygmomanometer is subject to the bias resulting from knowledge of earlier readings. The random-zero sphygmomanometer overcomes this bias, but it is more expensive and difficult to use and may underestimate blood pressure levels. In contrast to auscultatory devices, automated oscillometric devices are not subject to observer biases. They are gaining wider use and may be especially appropriate for younger children. However, they are expensive, and each model requires validation before use in epidemiological studies. Ambulatory blood pressure monitoring represents a potentially useful technique for future epidemiological studies. Multiple measurements are vital in estimating a child's blood pressure, and the number of visits, days or weeks apart, is at least as important as the number of measurements per visit.

Height, infant-feeding practices and cardiovascular functioning among 3 or 4 year old children in three ethnic groups

Barker recently hypothesized that factors affecting prenatal and infant growth are related to adult blood pressure and CVD mortality. Predictions from Barker's hypothesis in regard to infant feeding were tested among a sample of 3 or 4 year old children. The relationship of infant-feeding characteristics (duration of breast-feeding, times of introduction of high fat, high carbohydrate, high potassium foods and table salt) to indicators of cardiovascular functioning (resting blood pressures and heart rates, and heart rate response to graded activity) while controlling for anthropometric (height, sum of seven skinfolds, BMI) and demographic (ethnicity, gender, social status) characteristics revealed that infant-feeding practices were not related to CV functioning in the predicted directions among this sample of 3 or 4 year old children. Furthermore, the positive relationship between height and systolic blood pressure was inconsistent with the Barker hypothesis.

Determinants of antihypertensive response to calcium antagonists in systemic hypertension

Calcium antagonists are an important group of drugs in the treatment of systemic hypertension. Examination of the factors that determine the magnitude of antihypertensive response to calcium antagonists is of interest for clinical and basic pathophysiologic reasons. Possible factors influencing response include drug dose, plasma drug concentration, plasma renin activity, baseline blood pressure, nonionized calcium in blood and inside vascular smooth muscle cells, patient age and patient race. Published studies have examined the determinants of antihypertensive response. The striking fact about many of these studies is that they fail to control for other possible factors that might influence response. This article reviews the methods used and the results of 23 different studies that examined the determinants of response to calcium antagonists. Possible relationships between plasma renin activity, intra- and extracellular calcium levels, and the antihypertensive response, are of interest from a pathophysiologic point of view. From a clinician's standpoint, the only determinants that matter are the dose of the drug and the degree of elevation of the blood pressure. In this regard, calcium channel blocking drugs are no different from other drugs that act by peripheral vasodilation.