Genetic influences on ambulatory blood pressure patterns. The Medical College of Virginia Twin Study

Locking the Revolving Door: Racial Disparities in Cardiovascular Disease

Racial disparities in cardiovascular disease are unjust, systematic, and preventable. Social determinants are a primary cause of health disparities, and these include factors such as structural and overt racism. Despite a number of efforts implemented over the past several decades, disparities in cardiovascular disease care and outcomes persist, pervading more the outpatient rather than the inpatient setting, thus putting racial and ethnic minority groups at risk for hospital readmissions. In this article, we discuss differences in care and outcomes of racial and ethnic minority groups in both of these settings through a review of registries. Furthermore, we explore potential factors that connote a revolving door phenomenon for those whose adverse outpatient environment puts them at risk for hospital readmissions. Additionally, we review promising strategies, as well as actionable items at the policy, clinical, and educational levels aimed at locking this revolving door.

Cardiovascular Health in African Americans: A Scientific Statement From the American Heart Association

BACKGROUND AND PURPOSE

Population-wide reductions in cardiovascular disease incidence and mortality have not been shared equally by African Americans. The burden of cardiovascular disease in the African American community remains high and is a primary cause of disparities in life expectancy between African Americans and whites. The objectives of the present scientific statement are to describe cardiovascular health in African Americans and to highlight unique considerations for disease prevention and management.

METHOD

The primary sources of information were identified with PubMed/Medline and online sources from the Centers for Disease Control and Prevention.

RESULTS

The higher prevalence of traditional cardiovascular risk factors (eg, hypertension, diabetes mellitus, obesity, and atherosclerotic cardiovascular risk) underlies the relatively earlier age of onset of cardiovascular diseases among African Americans. Hypertension in particular is highly prevalent among African Americans and contributes directly to the notable disparities in stroke, heart failure, and peripheral artery disease among African Americans. Despite the availability of effective pharmacotherapies and indications for some tailored pharmacotherapies for African Americans (eg, heart failure medications), disease management is less effective among African Americans, yielding higher mortality. Explanations for these persistent disparities in cardiovascular disease are multifactorial and span from the individual level to the social environment.

CONCLUSIONS

The strategies needed to promote equity in the cardiovascular health of African Americans require input from a broad set of stakeholders, including clinicians and researchers from across multiple disciplines.

Childhood-Onset Essential Hypertension and the Family Structure

The prevalence and effect of single-parent families in childhood-onset essential hypertension (EH) is unknown. Children with EH and age-, sex-, and ethnicity-matched controls were enrolled. Family structure data were obtained by in-person interview. A total of 148 families (76 hypertension probands, 72 control probands; median 14 years) were prospective-ly enrolled in the study. Single-parent status was seen in 42% of the families--with and without EH (38% vs 46%, P=.41; odds ratio, 0.7; 95% confidence interval, 0.4-1.4). After multivariable analysis, a statistically significant sociofamilial contributor to the development of childhood-onset EH was not identified. A significant number of single-parent families (42%), the majority with single mothers, were found in our pedigree study. Sociofamilial factors are known to contribute to the expression of adult-onset EH, but findings in our study suggest that they appear to contribute less in the expression of childhood-onset EH.

Associations of common variants at APLN and hypertension in Chinese subjects with and without diabetes

Background. Apelin, the endogenous ligand for the APJ receptor, has a potent hypotensive effect via a nitric oxide-dependent mechanism in vivo. The aim of the study was to investigate the association between the common variants of apelin gene (APLN) and hypertension, which was reported recently in a Chinese Han population with and without diabetes. Methods. Three single nucleotide polymorphisms (SNPs) on APLN were genotyped in 3156 diabetic patients and 3736 nondiabetic individuals. For non-diabetic subjects, 1779 were enrolled in stage 1 and 1757 were recruited for validation. A meta-analysis combining the two stages was carried out to obtain the overall effect. Results. In diabetic patients, no significant associations of the three SNPs with hypertension were observed. In contrast, we found that rs2235306 was associated with hypertension in non-diabetic males after adjusting for covariates (OR = 1.19, P = 0.039) while rs2235307 and rs3115759 displayed no evidence of association in both genders. One haplotype, C-C-A, also showed an association with hypertension (OR = 1.47, P = 0.032) only in men. However, analysis in stage 2 and meta-analysis did not support these findings. Conclusions. We conclude that common variants on APLN are not associated with the prevalence of hypertension in the Chinese.

Pediatric ambulatory blood pressure monitoring: indications and interpretations

The prevalence of hypertension in children and adolescents is increasing, especially in obese and ethnic children. The adverse long-term effects of hypertension beginning in youth are known; therefore, it is important to identify young patients who need intervention. Unfortunately, measuring blood pressure (BP) is difficult due to the variety of techniques available and innate biologic variation in BP levels. Ambulatory BP monitoring may overcome some of the challenges clinicians face when attempting to categorize a young patient's BP levels. In this article, the authors review the use of ambulatory BP monitoring in pediatrics, discuss interpretation of ambulatory BP monitoring, and discuss gaps in knowledge in usage of this technique in the management of pediatric hypertension.

Non-replication study of a genome-wide association study for hypertension and blood pressure in African Americans

Background

A recent genome wide association study in 1017 African Americans identified several single nucleotide polymorphisms that reached genome-wide significance for systolic blood pressure. We attempted to replicate these findings in an independent sample of 2474 unrelated African Americans in the Milwaukee metropolitan area; 53% were women and 47% were hypertensives.

Methods

We evaluated sixteen top associated SNPs from the above genome wide association study for hypertension as a binary trait or blood pressure as a continuous trait. In addition, we evaluated eight single nucleotide polymorphisms located in two genes (STK-39 and CDH-13) found to be associated with systolic and diastolic blood pressures by other genome wide association studies in European and Amish populations. TaqMan MGB-based chemistry with fluorescent probes was used for genotyping. We had an adequate sample size (80% power) to detect an effect size of 1.2-2.0 for all the single nucleotide polymorphisms for hypertension as a binary trait, and 1% variance in blood pressure as a continuous trait. Quantitative trait analyses were performed both by excluding and also by including subjects on anti-hypertensive therapy (after adjustments were made for anti-hypertensive medications).

Results

For all 24 SNPs, no statistically significant differences were noted in the minor allele frequencies between cases and controls. One SNP (rs2146204) showed borderline association (p = 0.006) with hypertension status using recessive model and systolic blood pressure (p = 0.02), but was not significant after adjusting for multiple comparisons. In quantitative trait analyses, among normotensives only, rs12748299 was associated with SBP (p = 0.002). In addition, several nominally significant associations were noted with SBP and DBP among normotensives but none were statistically significant.

Conclusions

This study highlights the importance of replication to confirm the validity of genome wide association study results.

Heritability of Tpeak-Tend interval and T-wave amplitude: a twin study

BACKGROUND

Tpeak-Tend interval (TpTe) and T-wave amplitude (Tamp) carry diagnostic and prognostic information regarding cardiac morbidity and mortality. Heart rate and QT interval are known to be heritable traits. The heritability of T-wave morphology parameters such as TpTe and Tamp is unknown. TpTe and Tamp were evaluated in a large sample of twins.

METHODS AND RESULTS

Twins from the GEMINAKAR study (611 pairs, 246 monozygotic, 365 dizygotic; mean age, 38±11 years; 49% men) who had an ECG performed during 1997 to 2000 were included. Tamp was measured in leads V1 and V5. Duration variables (RR interval, QTpeak and QTend interval) were measured and averaged over 3 consecutive beats in lead V5. TpTe was calculated as the QTend- and QTpeak-interval difference. Heritability was assessed using structural equation models adjusting for age, sex, and body mass index. All models were reducible to a model of additive genetics and unique environment. All variables had considerable genetic components. Adjusted heritability estimates were as follows: TpTe, 46%; Tamp lead V1, 34%; Tamp lead V5, 47%; RR interval, 55%; QT interval, 67%; and Bazett-corrected QT interval, 42%.

CONCLUSIONS

RR interval, QT interval, Tamp, and TpTe interval are heritable ECG parameters.

Genetic influence on blood pressure measured in the office, under laboratory stress and during real life

To determine to what extent the genetic influences on blood pressure (BP) measured in the office, under psychologically stressful conditions in the laboratory and during real life are different from each other. Office BP, BP during a video game challenge and a social stressor interview, and 24-h ambulatory BP were measured in 238 European American and 186 African American twins. BP values across the two tasks were averaged to represent stress levels. Genetic model fitting showed no ethnic or gender differences for any of the measures. The model fitting resulted in heritability estimates of 63, 75 and 71% for office, stress and 24-h systolic BP (SBP) and 59, 67 and 69% for diastolic BP (DBP), respectively. Up to 81% of the heritability of office SBP and 71% of office DBP were attributed to genes that also influenced stress BP. However, only 45% of the heritability of 24-h SBP and 49% of 24-h DBP were attributed to genes that also influence office BP. Similarly, about 39% of the heritability of 24-h SBP and 42% of 24-h DBP were attributed to genes that also influence stress BP. Substantial overlap exists between genes that influence BP measured in the office, under laboratory stress and during real life. However, significant genetic components specific to each BP measurement also exist. These findings suggest that partly different genes or sets of genes contribute to BP regulation in different conditions.

Genome-wide association studies of hypertension: have they been fruitful?

Over the last two decades candidate gene association studies and genome-wide linkage scans have met with little success in characterizing risk variants for hypertension. Several factors could be responsible for the relative lack of success, although our understanding of the genetics has evolved to support the belief that there are multiple common risk variants, which are associated with hypertension with modest effect sizes. Genome-wide association studies (GWAS) have successfully identified risk loci for several complex polygenic disease states. Until recently, the productivity of GWAS with respect to identifying risk loci for hypertension was limited. In this paper we describe the recent success of GWAS of hypertension in identifying over a dozen loci associated with essential hypertension. We will review these findings, and place these results in the context of the future potential of pharmocogenetics of hypertension.

Heritability of daytime ambulatory blood pressure in an extended twin design

The present study estimated the genetic influences on ambulatory systolic and diastolic blood pressure, and on hypertensive status derived from ambulatory levels, in a family sample of 535 twins and 257 singleton siblings. This "extended twin design" was used to explicitly test the possibility that results obtained in singleton siblings are different from those obtained in twins. To examine the effects of excluding (medicated) hypertensive subjects, the genetic analyses were first performed under strict exclusion (medication and/or blood pressure >135/85 mm Hg), then without the medicated subjects, and, finally, without any exclusion. For the latter analysis, the untreated blood pressure values in subjects using antihypertensive medication were estimated by augmenting the observed blood pressure by the published efficacy of the specific antihypertensive medication used. No evidence was found for differential means, variances, or covariances of ambulatory blood pressure in singletons compared with twins. This indicates that estimates of heritability of ambulatory blood pressure from twin studies can be generalized to the singleton population. Heritability of hypertension, defined as a mean daytime blood pressure >135/85 mm Hg or antihypertensive medication use, was 61%. Genetic contribution to ambulatory blood pressure was highest when all subjects were included (systolic, 44% to 57%; diastolic, 46% to 63%) and lowest under strict exclusion (systolic, 32% to 50%; diastolic, 31% to 55%). We conclude that exclusion of (medicated) hypertensives removes part of the true genetic variance in ambulatory blood pressure.

Familiality of heart rate and cardiac-related autonomic activity in five-month-old twins: The Québec newborn twins study

The familiality of infant sleeping heart rate (HR) and cardiac-related autonomic activity, as indexed by spectral analysis of HR variability (HRV) and response to postural change, was investigated in 322 5-month-old twin pairs. The postural change elicited only minor changes in cardiovascular activity. As a result, analyses focused on supine cardiovascular activity. Multivariate genetic modeling indicated that individual differences in sleeping HR and high frequency (HF) HRV were determined by unique environmental and distinct additive genetic factors. These variables, along with low frequency (LF) HRV, were also affected by overlapping familial environmental influences. Familial influences in HF HRV were more pronounced for baby girls than boys. Estimates of relative LF and HF HRV were determined by common (familial) and unique environmental factors; familial influences on these estimates did not overlap with familial influences on sleeping HR.

Influence of chorionicity on the heritability estimates of blood pressure: a study in twins

BACKGROUND

A basic assumption of the twin design is that environmental influences including prenatal experiences are equal across twin types. However, the intra-uterine environment may differ according to the chorionicity of the monozygotic twins, which may have biased previous heritability estimates of blood pressure.

OBJECTIVE

The aim of the present study was to assess whether the heritability of blood pressure, derived from measurements in monozygotic and dizygotic twins, differs according to the chorionicity of the monozygotic twins.

METHODS

Conventional and 24-h ambulatory blood pressures were measured in 125 dizygotic twin pairs and in 97 dichorionic and 128 monochorionic monozygotic twin pairs at the age of 18-34 years. The twin sample was drawn from the East Flanders Prospective Twin Survey, in which perinatal data were collected at birth. Intra-pair correlation coefficients were calculated and compared between both types of monozygotic twin pairs. Heritability was estimated from model-fitting and path analysis, based on the dizygotic twins and, respectively, all monozygotic twins and the two subtypes.

RESULTS

Intra-pair correlation coefficients for the various blood pressures, after adjustment for body mass index, ranged from 0.45 to 0.71 in the monozygotic twin pairs and did not differ significantly according to chorionicity. Heritability estimates of blood pressure were between 52 and 64%, and were similar when calculated from dizygotic twins and, respectively, dichorionic and monochorionic monozygotic twins.

CONCLUSIONS

Heritability estimates of conventional and ambulatory blood pressure do not differ significantly according to the chorionicity of the monozygotic twins.

Dissecting the genetic architecture of the cardiovascular and renal stress response

We review the evidence for a genetic basis of the cardiovascular and renal stress response. A bio-behavioral model of stress-induced hypertension is presented that explains how repeated exposure to stress in combination with genetic susceptibility might lead to the development of hypertension. In this model, we focus on three underlying physiological systems that mediate the stress response of the heart, vasculature and kidney: the sympathetic nervous system (SNS), the renin-angiotensin-aldosterone system (RAAS) and the endothelial system (ES). We then review the evidence for a genetic influence on cardiovascular reactivity to psychological stress and stress-induced sodium retention using data from twin and family studies and a limited number of candidate gene studies. Finally, by describing the underlying physiological systems of our model and their genetic underpinning we emphasize the importance of inclusion of genetic measurements in any future studies testing the reactivity hypothesis.

A comparison of ambulatory blood pressure patterns across populations

BACKGROUND

Black individuals are characterized by a blunted nocturnal decline (i.e. dipping) in blood pressure compared with whites. The resulting increase in cardiovascular load has been hypothesized to contribute to ethnic differences in hypertension and its sequelae.

OBJECTIVE

To examine data from two different locations and determine factors related to ethnic differences in ambulatory blood pressure pattern.

METHODS

Ambulatory blood pressure recordings were performed on 300 youths from Memphis, Tennessee and 195 youths from Augusta, Georgia, USA. Stepwise regressions were performed to determine the factors associated with daytime and night-time blood pressure and the nocturnal decline in blood pressure. The factors examined were recording location, ethnicity, gender, age, height, weight and genetic predisposition.

RESULTS

Significant factors in the model for the nocturnal decline in systolic blood pressure included location (R(2) = 0.031, P < 0.001), followed by ethnicity (R(2) change = 0.015, P < 0.006) and height (R(2) change = 0.009,P < 0.03). Significant factors in the model for the nocturnal decline in diastolic blood pressure included location ( R(2) = 0.176, P < 0.001), followed by ethnicity ( R(2) change = 0.016, P < 0.002) and height (R(2) change = 0.02, P < 0.001). The nocturnal decline was greater in the Augusta subjects because of higher daytime systolic (P < 0.002) and diastolic (P < 0.001) blood pressure. Weight contributed significantly to the models for resting blood pressure and daytime blood pressure. Gender was the only variable that contributed to the model for resting systolic blood pressure.

CONCLUSIONS

Both genetic and environmental factors contribute to individual differences in ambulatory blood pressure patterns. Much of the variance of ambulatory blood pressure levels and patterns remains, however, unexplained.

The influence of heredity on self-reported sleep patterns in free-living humans

The heritability of self-reported sleep patterns was investigated with 86 identical and 78 fraternal same-sex and 51 fraternal mixed-gender adult twin pairs who were paid to maintain 7-day diaries. Linear structural modeling was applied to investigate the nature and degree of genetic and environmental influences and revealed significant genetic influences on the time that individuals went to sleep and woke up, how often the individual woke up during the night, the duration of sleep and wakefulness, and how alert the individual felt upon waking and over the day, accounting for 21% to 41% of the variance. These influences of heredity were present for sleep-wake behavior over the entire week and also when the sleep-wake pattern was analyzed separately for weekdays and weekends. Further, it was demonstrated that there were multiple independent influences of heredity on sleep-wake behavior. The results suggest that sleep-wake patterns are not learned but result in part from multiple heritable influences.

Repeated blood pressure measurements in a sample of Swedish twins: heritabilities and associations with polymorphisms in the renin-angiotensin-aldosterone system

BACKGROUND

Twin and family studies have shown that genetic effects explain a relatively high amount of the phenotypic variation in blood pressure. However, many studies have not been able to replicate findings of association between specific polymorphisms and diastolic and systolic blood pressure.

METHODS

In a structural equation-modelling framework the authors investigated longitudinal changes in repeated measures of blood pressures in a sample of 298 like-sexed twin pairs from the population-based Swedish Twin Registry. Also examined was the association between blood pressure and polymorphisms in the angiotensin-I converting enzyme and the angiotensin II receptor type 1 with the 'Fulker' test. Both linkage and association were tested simultaneously revealing whether the polymorphism is a Quantitative Trait Locus (QTL) or in linkage disequilibrium with the QTL.

RESULTS

Genetic influences explained up to 46% of the phenotypic variance in diastolic and 63% of the phenotypic variance in systolic blood pressure. Genetic influences were stable over time and contributed up to 78% of the phenotypic correlation in both diastolic and systolic blood pressure. Non-shared environmental effects were characterised by time specific influences and little transmission from one time point to the next. There was no significant linkage and association between the polymorphisms and blood pressure.

CONCLUSIONS

There is a considerable genetic stability in both diastolic and systolic blood pressure for a 6-year period of time in adult life. Non-shared environmental influences have a small long-term effect. Although associations with the polymorphisms could not be replicated, results should be interpreted with caution due to power considerations.

Heritability of diurnal changes in food intake in free-living humans

OBJECTIVES

The time of day of meal ingestion, the number of people present at the meal, the subjective state of hunger, and the estimated before-meal contents in the stomach have been established as influences on the amount eaten in a meal, and this influence has been shown to be heritable. Because these factors intercorrelate, the possibility that the calculated heritabilities for some of these variables could result indirectly from their convariation with one of the other heritable variables was assessed.

METHODS

The independence of the heritability of the influence of these four factors was investigated with 110 identical and 102 fraternal same-sex and 53 fraternal mixed-sex adult twin pairs who were paid to maintain 7-d food intake diaries. From the diary reports, the meal sizes were calculated and subjected to multiple regression analysis using the estimated before-meal stomach contents, the reported number of other people present, the subjective hunger ratings, and the time of day of the meal as predictors. Linear structural modeling was applied to the beta coefficients from the multiple regression to investigate whether the heritability of the influences of these four variables was independent.

RESULTS

Significant genetic effects were found for the beta coefficients for all four variables, indicating that the heritability of their relationship with intake is to some extent heritable.

CONCLUSIONS

These results suggest that the influences of multiple factors on intake are influenced by the genes and become part of the total package of genetically determined physiologic, sociocultural, and psychological processes that regulate energy balance.

The impact of genetic and environmental influences on blood pressure variance across age-groups

OBJECTIVE

The purpose of the present investigation was to examine the age-dependency of blood pressure heritability by use of the twin method in different age groups.

DESIGN

In 272 (150 monozygous and 122 dizygous) twin pairs, aged 18 to 76 years, both conventional and ambulatory blood pressure were measured. After correction for possible confounders, model fitting was used to estimate heritability and 95% confidence limits in three age groups of similar size, i.e. 18-29, 30-39 and > or = 40 years.

RESULTS

Heritability estimates were significant in each age group, ranging from 35 to 67% for the various blood pressure measurements. The estimates tended to decrease with increasing age, except for conventional diastolic blood pressure, but the intergroup differences did not reach statistical significance, despite adequate power.

CONCLUSIONS

In conclusion, blood pressure heritability is significant in various age groups, but does not substantially change with advancing age. Twin analysis does not indicate that models for blood pressure regulation in various age groups should take into account the possibility of age-related changes in the expression of relevant genes, in the presence of relevant environmental agents, or in the susceptibility to the latter (gene-environment interaction).

Heritability of central systolic pressure augmentation: a twin study

Less than 50% of the variance in left ventricular mass is explained by conventional factors such as age, blood pressure, and body size. Genetic influences may account for part of the unexplained variance. The central (aortic) pressure augmentation index has been suggested as a noninvasive measure of pulsatile load, which is a likely determinant of left ventricular mass. We quantified the genetic influence on augmentation index and determined the extent to which this influence is dependent on the effects of age, height, heart rate, and blood pressure. We performed a classical twin study composed of 225 monozygotic and 594 dizygotic female white twin pairs aged 18 to 73 years. Augmentation index and mean arterial pressure were based on the central pressure wave derived from the radial waveform as measured by applanation tonometry. Quantitative genetic modeling techniques were used to analyze the data. The heritability of augmentation index was 37%, whereas heritabilities for blood pressure traits varied between 13% and 25%. Most of the variance in augmentation index could be explained by genetic and environmental factors specifically influencing augmentation index. Only a relatively small part of the total variance in augmentation index could be attributed to genes in common with height (3.1%), heart rate (4.6%), and mean arterial pressure (5.6%). Age explained 19% of the total variation in augmentation index. In conclusion, augmentation index has a significant heritable component, which is largely independent of the influence of blood pressure, heart rate, height, and age. Finding genes for the augmentation index could help to unravel pathophysiological mechanisms causing left ventricular hypertrophy and lead to improvements in prevention, diagnosis, and treatment of at-risk populations.

The Emerging Importance of Genetics in Epidemiologic Research III. Bioinformatics and statistical genetic methods

PURPOSE

To outline potential benefits of integrating recent developments in bioinformatics and statistical genetics with traditional epidemiologic studies to localize genes influencing complex phenotypes and examine genetic effects on disease susceptibility.

METHODS

An overview of bioinformatic and statistical approaches for localizing disease-susceptibility genes as well as challenges associated with identifying functional DNA variants and context-dependent genetic effects concludes this three-part series on the importance of genetics in epidemiologic research.

RESULTS

Rapidly evolving bioinformatic and statistical methods are providing invaluable information on newly-discovered genes and molecular variation influencing human diseases that is readily available to epidemiologic researchers.

CONCLUSIONS

Integrating bioinformatics and molecular biotechnology with epidemiologic methods of assessing disease risk is rapidly expanding our ability to identify genetic influences on complex human diseases. These technological advances are likely to have a profound impact on current knowledge of complex disease etiology, and may reveal novel approaches to disease treatment and prevention.

Normotensive offspring with non-dipper hypertensive parents have abnormal sleep pattern

The objective of this study was to determine whether abnormal microstructure of sleep in non-dipper hypertensive patients was present in their offspring. Subjects included 11 normotensive offspring of non-dipper hypertensive parents (FH + ND), 6 of dipper hypertensive parents (FH + D) and 5 of normotensive parents (Controls). We measured blood pressure beat-to-beat by Finapres and all stages of sleep by polysomnographically recording simultaneously during spontaneous nocturnal sleep. We analysed blood pressure pattern for 4-min long random periods while the subjects were awake and during all stages of sleep; sleep efficiency (SE), sleep latency (SL), delta-sleep latency (delta-SL), REM sleep latency (REM-SL), Stage 1, Stage 2, Stage 3, Stage 4 and REM duration and percentage values, and microstructural aspects of sleep (arousal and microarousal temporization and features). FH + D and controls showed a fall in blood pressure greater than 10% in all stages of NREM sleep and in the FH + ND blood pressure fall in less than 10% of waking values in all NREM stages. REM sleep and heart rate were similar in the three groups during all stages of sleep. FH + ND showed the same number of arousals but more microarousals than FH + D and controls (p < 0.0001). Microarousals induced several stage shifts through lighter sleep. For this reason, FH + ND spent more time in stage 2 than FH + D and controls. In conclusion, offspring of non-dipper hypertension parents showed a greater number of microarousals than the other two groups.

Predictors of future ambulatory blood pressure in youth

OBJECTIVE

The objective of this study was to determine the predictors of future ambulatory blood pressure in normotensive youths with family histories of essential hypertension.

STUDY DESIGN

Eighty-eight healthy youths (mean age 10.9 +/- 2.5 years; 52 blacks, 36 whites; 45 boys) were studied. During an initial visit anthropometric variables and hemodynamics were measured at rest and before, during, and after three laboratory stressors: postural change, forehead cold, and video game challenge. The subjects' ambulatory blood pressure was monitored for 24 hours as part of a follow-up evaluation an average of 2.5 years later.

RESULTS

Anthropometric and demographic variables and measures of reactivity to laboratory stressors were related to future daytime and nighttime ambulatory blood pressure.

CONCLUSION

These findings provide important information on the predictors of ambulatory blood pressure and underscore the importance of resting blood pressure and adiposity. These results support the guidelines of the Second Task Force, which recommend the measurement of blood pressure and adiposity in the context of ongoing health care.

Genetic variants of the renin-angiotensin system and ambulatory blood pressure in essential hypertension

OBJECTIVE

To examine whether the angiotensinogen M235T and angiotensin converting enzyme insertion/deletion (I/D) variants are related to the severity of hypertension in patients with established essential hypertension.

DESIGN

A cross-sectional study.

SETTING

The hypertension clinic of the Benjamin Franklin University Hospital, Free University of Berlin.

PARTICIPANTS

Three hundred and forty-three consecutive Caucasian patients who presented with treated or untreated (n = 115) hypertension were enrolled into the study. Twenty-two patients were excluded from analysis because they had secondary hypertension.

MAIN OUTCOME MEASURES

Angiotensinogen M235T and angiotensin-converting enzyme I/D genotypes, 24 h ambulatory blood pressure values, the number of antihypertensive medications administered and left ventricular dimensions assessed by two-dimensional echocardiography.

RESULTS

Neither the angiotensinogen nor the angiotensin converting enzyme genotype was related significantly to the average ambulatory blood pressure and left ventricular dimensions in hypertensives. Furthermore, neither the number of antihypertensive medications administered to treated patients nor blood pressure levels in untreated patients (n = 115) differed significantly between the genotypic groups.

CONCLUSIONS

These results do not support the hypothesis that the studied molecular variants of the renin-angiotensin system may represent clinically useful markers of the severity of hypertension in Caucasians with established essential hypertension.