Systolic and fourth- and fifth-phase diastolic blood pressure from ages 8 to 18 years: Project HeartBeat!

Sex-specific trajectories of molecular cardiometabolic traits from childhood to young adulthood

BACKGROUND

The changes which typically occur in molecular causal risk factors and predictive biomarkers for cardiometabolic diseases across early life are not well characterised.

METHODS

We quantified sex-specific trajectories of 148 metabolic trait concentrations including various lipoprotein subclasses from age 7 years to 25 years. Data were from 7065 to 7626 offspring (11 702 to14 797 repeated measures) of the Avon Longitudinal Study of Parents and Children birth cohort study. Outcomes were quantified using nuclear magnetic resonance spectroscopy at 7, 15, 18 and 25 years. Sex-specific trajectories of each trait were modelled using linear spline multilevel models.

RESULTS

Females had higher very-low-density lipoprotein (VLDL) particle concentrations at 7 years. VLDL particle concentrations decreased from 7 years to 25 years with larger decreases in females, leading to lower VLDL particle concentrations at 25 years in females. For example, females had a 0.25 SD (95% CI 0.20 to 0.31) higher small VLDL particle concentration at 7 years; mean levels decreased by 0.06 SDs (95% CI -0.01 to 0.13) in males and 0.85 SDs (95% CI 0.79 to 0.90) in females from 7 years to 25 years, leading to 0.42 SDs (95% CI 0.35 to 0.48) lower small VLDL particle concentrations in females at 25 years. Females had lower high-density lipoprotein (HDL) particle concentrations at 7 years. HDL particle concentrations increased from 7 years to 25 years with larger increases among females leading to higher HDL particle concentrations in females at 25 years.

CONCLUSION

Childhood and adolescence are important periods for the emergence of sex differences in atherogenic lipids and predictive biomarkers for cardiometabolic disease, mostly to the detriment of males.

Genetic Variants Associated With Systolic Blood Pressure in Children and Adolescents

Background Genetics, along with lifestyle and behavioral characteristics, play an important role in hypertension in adults. Our aim was to identify genetic variants associated with blood pressure in childhood and adolescence. Methods and Results We conducted a candidate single-nucleotide polymorphism (SNP) analysis and genome-wide association study among 9778 participants aged <18 years in BioVU, the Vanderbilt University Medical Center biobank. The outcome was childhood blood pressure percentile from age 0 to 18 years. For the candidate SNP analysis, a total of 457 previously identified SNPs were examined. Linear regression was used to test the association between genetic variants and median systolic blood pressure (SBP) percentile. Adjusted models included median age, self-reported sex, race, the first 4 principal components of ancestry, and median body mass index Z score. Analyses were conducted in the overall cohort and stratified by age group. A polygenic risk score was calculated for each participant, and the association between polygenic risk score and median SBP percentile in childhood was examined using linear regression. In the overall candidate SNP analysis, 2 SNPs reached significance: rs1018148 (FBN1; P=1.0×10-4) and rs11105354 (ATP2B1; P=1.4×10-4). In the postpuberty age group, 1 SNP reached significance: rs1018148 (FBN1; P=2.2×10-5). In the genome-wide association study of all participants, no SNPs reached genome-wide significance. Higher polygenic risk score was associated with higher SBP percentile (β, 0.35 [95% CI, 0.10-0.60)], and there was a significant interaction with age (P for interaction<0.01). Conclusions These findings suggest that genetic variants play an important role in SBP in childhood and adolescence and provide evidence for age-specific genetic associations with SBP.

Blood Pressure Trajectories Across the Life Course

High blood pressure (BP) is a strong modifiable risk factor for cardiovascular disease (CVD). Longitudinal BP patterns themselves may reflect the burden of risk and vascular damage due to prolonged cumulative exposure to high BP levels. Current studies have begun to characterize BP patterns as a trajectory over an individual's lifetime. These BP trajectories take into account the absolute BP levels as well as the slope of BP changes throughout the lifetime thus incorporating longitudinal BP patterns into a single metric. Methodologic issues that need to be considered when examining BP trajectories include individual-level vs. population-level group-based modeling, use of distinct but complementary BP metrics (systolic, diastolic, mean arterial, mid, and pulse pressure), and potential for measurement errors related to varied settings, devices, and number of readings utilized. There appear to be very specific developmental periods during which divergent BP trajectories may emerge, specifically adolescence, the pregnancy period, and older adulthood. Lifetime BP trajectories are impacted by both individual-level and community-level factors and have been associated with incident hypertension, multimorbidity (CVD, renal disease, cognitive impairment), and overall life expectancy. Key unanswered questions remain around the additive predictive value of BP trajectories, intergenerational contributions to BP patterns (in utero BP exposure), and potential genetic drivers of BP patterns. The next phase in understanding BP trajectories needs to focus on how best to incorporate this knowledge into clinical care to reduce the burden of hypertensive-related outcomes and improve health equity.

Sex Differences in Association of Elevated Blood Pressure with Variables Characterizing Cardiometabolic Risk in Young Subjects with or Without Metabolic Abnormalities

Males present higher blood pressure (BP) values, higher prevalence of elevated BP, and a different prevalence of cardiometabolic risk factors when compared with females. We assumed that the trends of risk markers across BP categories (normotension, high normal BP, and hypertension) differ in young males and females, and between subjects without metabolic abnormalities (without obesity, insulin resistance, atherogenic dyslipidemia, hyperuricemia, or microinflammation) and those presenting them. Data from 2543 subjects (48% males) aged from 16 to 23 years were analyzed. The findings showed that 15% of males and 4% of females presented high normal BP while 9% and 1%, respectively, had hypertension. In males, variables characterizing obesity status, insulin sensitivity, atherogenic dyslipidemia, uric acid, adiponectin, a soluble receptor for advanced glycation end-products, and leukocyte counts showed worsening trends across BP categories. Females presented significant trends only for obesity measures, LDL-cholesterol, and non-HDL-cholesterol. Across BP categories, trends of variables characterizing cardiometabolic risk differed among abnormalities-free and presenting males. The multivariate model selected measures of central obesity, atherogenic dyslipidemia, insulin resistance, and uric acid as significant predictors of BP in both genders, and C-reactive protein in females. Sex differences in measures of cardiovascular health in juveniles may remain undiscovered unless two sexes are analyzed separately. These differences may have implications for sex-specific disease risk in adulthood.

Consolidated Biochemical Profile of Subacute Stage Traumatic Brain Injury in Early Development

Traumatic brain injury (TBI) in general has varied neuropathological consequences depending upon the intensity and biomechanics of the injury. Furthermore, in pediatric TBI, intrinsic developmental changes add further complexity, necessitating a biochemical dimension for improved TBI characterization. In our earlier study investigating the subacute stage TBI metabolome (72 h post-injury) in a developmental rat model, significant ipsilateral brain biochemical changes occurred across 25 metabolite sets as determined by metabolite set enrichment analysis (MSEA). The broad metabolic perturbation was accompanied by behavioral deficits and neuronal loss across the ipsilateral hemisphere containing the injury epicenter. In order to obtain a consolidated biochemical profile of the TBI assessment, a subgrouping of the 190 identified brain metabolites was performed. Metabolites were divided into seven major subgroups: oxidative energy/mitochondrial, glycolysis/pentose phosphate pathway, fatty acid, amino acid, neurotransmitters/neuromodulators, one-carbon/folate and other metabolites. Subgroups were based on the chemical nature and association with critically altered biochemical pathways after TBI as obtained from our earlier untargeted analysis. Each metabolite subgroup extracted from the ipsilateral sham and TBI brains were modeled using multivariate partial least square discriminant analysis (PLS-DA) with the model accuracy used as a measurable index of TBI neurochemical impact. Volcano plots of each subgroup, corrected for multiple comparisons, determined the TBI neurochemical specificity. The results provide a ranked biochemical profile along with specificity of changes after developmental TBI, enabling a consolidated biochemical template for future classification of different TBI intensities and injury types in animal models.

Beneficial Effects of Kaempferol after Developmental Traumatic Brain Injury Is through Protection of Mitochondrial Function, Oxidative Metabolism, and Neural Viability

Oxidative energy metabolism is depressed after mild/moderate traumatic brain injury (TBI) during early development, accompanied by behavioral debilitation and secondary neuronal death. A TBI metabolome analysis revealed broad effects with a striking impact on energy metabolism. Our studies on mitochondrial modulators and their effects on brain function have shown that kaempferol, a stimulator of the mitochondrial Ca2+ uniporter channel (mCU), enhanced neural and neurovascular activity in the normal brain and improved stimulus-induced brain activation and behavior after TBI during early development. Because kaempferol enhances mitochondrial Ca2+ uptake and cycling, with protective effects after TBI, we tested the hypothesis that kaempferol treatment during the acute/subacute stage after TBI (0-72 h) acted on mitochondria in improving TBI outcome. Developmental age rats (P31) underwent TBI and were treated with vehicle or kaempferol (1 mg/kg intraperitoneally) in three doses at 1, 24, and 48 h after TBI. Brains were harvested at 72 h and subjected to liquid chromatography mass spectrometric measurements. Decrease in pyruvate and tricarboxylic acid (TCA) cycle flux were observed in the untreated and vehicle-treated group, consistent with previously established energy metabolic decline after TBI. Kaempferol improved TCA cycle flux, maintained mitochondrial functional integrity as observed by decreased acyl carnitines, improved neural viability as evidenced by higher N-acetyl aspartate levels. The positive outcomes of kaempferol on metabolic profile corresponded with improved sensorimotor behavior.

Sex-specific trajectories of measures of cardiovascular health during childhood and adolescence: A prospective cohort study

BACKGROUND AND AIMS

Sex differences in measures of cardiovascular health in adults are well documented. However, the sex-specific aetiology of cardiovascular health across childhood and adolescence is poorly understood.

METHODS

We examined sex differences in trajectories of 11 measures of cardiovascular health from birth to 18 years, in a contemporary birth cohort study in England (N participants per outcomes: 662-13,985, N repeated measures per outcome: 1,831-112,768). Outcomes were measured over varying time spans from birth or mid-childhood to age 18 and with different numbers of repeated measures per outcome. Analyses were performed using fractional polynomial and linear spline multilevel models.

RESULTS

Females had higher mean BMI, height-adjusted fat mass, pulse rate, insulin, triglycerides, and non-high-density lipoprotein cholesterol (HDL-c) and lower mean height-adjusted lean mass from birth or from mid-childhood to age 18. For example, mean non-HDL-c was 0.07 mmol/l (95% confidence interval (CI), 0.04, 0.10) higher in females compared with males at birth. By age 18, this difference persisted and widened to 0.19 mmol/l (95% CI, 0.16, 0.23) higher non-HDL-c in females compared with males. Females had lower levels of glucose from mid-childhood and developed lower systolic blood pressure and higher HDL-c from mid-adolescence onward. For example, females had 0.08 mmol/l (95% CI, 0.05, 0.10) lower mean glucose compared with males at age seven which widened to a difference of 0.22 mmol/l (95% CI, 0.25, 0.19) at age 18.

CONCLUSIONS

Sex differences in measures of cardiovascular health are apparent from birth or mid-childhood and change during early life. These differences may have implications for sex-specific disease risk in future adult populations.

Associations of Y chromosomal haplogroups with cardiometabolic risk factors and subclinical vascular measures in males during childhood and adolescence

Background and aims

Males have greater cardiometabolic risk than females, though the reasons for this are poorly understood. The aim of this study was to examine the association between common Y chromosomal haplogroups and cardiometabolic risk during early life.

Methods

In a British birth cohort, we examined the association of Y chromosomal haplogroups with trajectories of cardiometabolic risk factors from birth to 18 years and with carotid-femoral pulse wave velocity, carotid intima media thickness and left ventricular mass index at age 18. Haplogroups were grouped according to their phylogenetic relatedness into categories of R, I, E, J, G and all other haplogroups combined (T, Q, H, L, C, N and O). Risk factors included BMI, fat and lean mass, systolic blood pressure (SBP), diastolic blood pressure, pulse rate, triglycerides, high density lipoprotein cholesterol (HDL-c), non-HDL-c and c-reactive protein. Analyses were performed using multilevel models and linear regression, as appropriate.

Results

Y chromosomal haplogroups were not associated with any cardiometabolic risk factors from birth to 18 years. For example, at age 18, the difference in SBP comparing each haplogroup with haplogroup R was −0.39 mmHg (95% Confidence Interval (CI): −0.75, 1.54) for haplogroup I, 2.56 mmHg (95% CI: −0.76, 5.89) for haplogroup E, −0.02 mmHg (95% CI: −2.87, 2.83) for haplogroup J, 1.28 mmHg (95% CI: −4.70, 2.13) for haplogroup G and −2.75 mmHg (95% CI: −6.38, 0.88) for all other haplogroups combined.

Conclusions

Common Y chromosomal haplogroups are not associated with cardiometabolic risk factors during childhood and adolescence or with subclinical cardiovascular measures at age 18.

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Common Y chromosomal haplogroups are not associated with cardiometabolic risk factors from birth to age 18.

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Common Y chromosomal haplogroups are not associated with cardiovascular structure and function at age 18.

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Common Y chromosomal haplogroups are not associated with cardiometabolic risk in males during early life.

International Genome-Wide Association Study Consortium Identifies Novel Loci Associated With Blood Pressure in Children and Adolescents

BACKGROUND

Our aim was to identify genetic variants associated with blood pressure (BP) in childhood and adolescence.

METHODS AND RESULTS

Genome-wide association study data from participating European ancestry cohorts of the Early Genetics and Lifecourse Epidemiology (EAGLE) Consortium was meta-analyzed across 3 epochs; prepuberty (4-7 years), puberty (8-12 years), and postpuberty (13-20 years). Two novel loci were identified as having genome-wide associations with systolic BP across specific age epochs: rs1563894 (ITGA11, located in active H3K27Ac mark and transcription factor chromatin immunoprecipitation and 5'-C-phosphate-G-3' methylation site) during prepuberty (P=2.86×10(-8)) and rs872256 during puberty (P=8.67×10(-9)). Several single-nucleotide polymorphism clusters were also associated with childhood BP at P<5×10(-3). Using a P value threshold of <5×10(-3), we found some overlap in variants across the different age epochs within our study and between several single-nucleotide polymorphisms in any of the 3 epochs and adult BP-related single-nucleotide polymorphisms.

CONCLUSIONS

Our results suggest that genetic determinants of BP act from childhood, develop over the lifecourse, and show some evidence of age-specific effects.

Developmental trajectories of cerebrovascular reactivity in healthy children and young adults assessed with magnetic resonance imaging

KEY POINTS

Cerebrovascular reactivity (CVR) reflects the vasodilatory reserve of cerebral resistance vessels. Normal development in children is associated with significant changes in blood pressure, cerebral blood flow (CBF) and cerebral oxygen metabolism. Therefore, it stands to reason that CVR will also undergo changes during this period. The study acquired magnetic resonance imaging measures of CVR and CBF in healthy children and young adults to trace their changes with age. We found that CVR changes in two phases, increasing with age until the mid-teens, followed by a decrease. Baseline CBF declined steadily with age. We conclude that CVR varies with age during childhood, which prompts future CVR studies involving children to take into account the effect of development.

ABSTRACT

Cerebrovascular reactivity (CVR) reflects the vasculature's ability to accommodate changes in blood flow demand thereby serving as a critical imaging tool for mapping vascular reserve. Normal development is associated with extensive physiological changes in blood pressure, cerebral blood flow and cerebral metabolic rate of oxygen, all of which can affect CVR. Moreover, the evolution of these physiological parameters is most prominent during childhood. Therefore, the aim of this study was to use non-invasive magnetic resonance imaging (MRI) to characterize the developmental trajectories of CVR in healthy children and young adults, and relate them to changes in cerebral blood flow (CBF). Thirty-four healthy subjects (17 males, 17 females; age 9-30 years) underwent CVR assessment using blood oxygen level-dependent MRI in combination with a computer controlled CO2 stimulus. In addition, baseline CBF was measured with a pulsed arterial spin labelling sequence. CVR exhibited a gradual increase with age in both grey and white matter up to 14.7 years. After this break point, a negative correlation with age was detected. Baseline CBF maintained a consistent negative linear correlation across the entire age range. The significant age-dependent changes in CVR and CBF demonstrate the evolution of cerebral haemodynamics in children and should be taken into consideration. The shift in developmental trajectory of CVR from increasing to decreasing suggests that physiological factors beyond baseline CBF also influence CVR.

Risk profiles of lipids, blood pressure, and anthropometric measures in childhood and adolescence: project heartBeat!

Background

Many common risk factors for cardiovascular disease (CVD) originate in childhood and adolescence. There is a lack of literature examining variability within study populations, as well as a shortage of simultaneous analyses of CVD risk factors operating in tandem.

Methods

We used data from Project HeartBeat!-a multi-cohort longitudinal growth study of children and adolescents in the US - for assessing multiple profiles for lipids, blood pressure, and anthropometric measures. Principal component functional curve analysis methods were used to summarize trajectories of multiple measurements. Subsequently less favorable health (high risk) and more favorable (low risk) groups from both female and male cohorts were identified and compared to US national norms.

Results

Compared to national norms, the high risk groups have increased waist circumference, body mass index, and percent body fat as well as higher low-density lipoprotein cholesterol and triglyceride levels, and lower high-density lipoprotein cholesterol. The risk profiles also exhibit patterns of convergence and divergence across the high and low risk groups as a function of age.

Conclusions

These observations may have clinical and public health implications in identifying groups of children at high risk of CVD for earlier interventions.

A life course approach to cardiovascular aging

A life course approach in epidemiology investigates the biological, behavioral and social pathways that link physical and social exposures and experiences during gestation, childhood, adolescence and adult life, and across generations, to later-life health and disease risk. We illustrate how a life course approach has been applied to cardiovascular disease, highlighting the evidence in support of the early origins of disease risk. We summarize how trajectories of cardiometabolic risk factors change over the life course and suggest that understanding underlying 'normal' or 'healthy' trajectories and the characteristics that drive deviations from such trajectories offer the potential for early prevention and for identifying means of preventing future disease.

Differences between the fourth and fifth Korotkoff phases among children and adolescents

BACKGROUND

The relative importance of the fourth (K4) and fifth (K5) Korotkoff phases as the indicator of diastolic blood pressure (DBP) levels among children remains uncertain.

METHODS

In a sample of 11,525 youth aged 5-17, we examined interexaminer differences in these 2 phases and the relation of theses 2 phases to adult blood pressure levels and hypertension. The longitudinal analyses were conducted among 2,156 children who were re-examined after age 25 years.

RESULTS

Mean (±SD) levels of DBP were 62 (±9) mm Hg (K4) and 49 (±13) mm Hg (K5). K4 showed less interobserver variability than did K5, and 7% of the children had at least 1 (of 6) K5 value of 0mm Hg. Longitudinal analyses indicated that K4 was more strongly associated with adult blood pressure levels and hypertension. In correlational analyses of subjects who were not using antihypertensive medications in adulthood (n = 1,848), K4 was more strongly associated with the adult DBP level than was K5 (r = 0.22 vs. 0.17; P < 0.01). Analyses of adult hypertension (based on high blood pressure levels or use of antihypertensive medications) indicated that the screening performance of childhood levels of K4 was similar to that of systolic blood pressure and was higher than that of K5, with areas under the receiver operator characteristic curves of 0.63 (systolic blood pressure), 0.63 (K4), and 0.57 (K5).

CONCLUSIONS

As compared with K5 levels among children, K4 shows less interobserver variability and is more strongly associated with adult hypertension.

Long-term predictors of blood pressure among adolescents during an 18-month school-based obesity prevention intervention

PURPOSE

To evaluate the effectiveness of the HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic Schools) initiative, a multicomponent school-based obesity prevention intervention based on the Centers for Disease Control and Prevention's coordinated school health approach, on the improvement of blood pressure (BP) and to determine long-term predictors of systolic and diastolic BP changes among high school students who were exposed to the intervention.

METHODS

Biometric and behavioral data from high school students were analyzed at baseline, 6, 12, and 18 months (N = 847, three schools). The attrition rate at 18 months was 26.1%. Sequential generalized estimating equation models were fit to the data using SAS 9.3, taking into account clustering effects within the same school and correlations within repeated measures.

RESULTS

A significant downward trend was observed in systolic BP (p = .0006) and diastolic BP (p < .0001) among the students who were exposed to the HEROES initiative. The prevalence of hypertension decreased from 17.1% at baseline to 12.8% at 6 months (p < .0001), 12.0% at 12 months (p < .0001), and 15.0% (p = .0024) at 18 months. Baseline body mass index, increases in body mass index percentiles, and increases of television-viewing hours were associated with BP increases. Increases in frequencies of eating french fries or chips, skipping breakfast, and consuming supersize meals when eating fast food were predictive of systolic BP changes, not of diastolic BP changes.

CONCLUSIONS

An 18-month multicomponent school-based obesity intervention program may be effectively used to decrease rates of high BP among adolescents.

School children systolic and diastolic blood pressure values: YUSAD study

The aim of the study was to analyze changes of systolic and diastolic blood pressure values over five and ten years separately boys and girls and to estimate correlation between them. Three age groups from 8 centers in Serbia were evaluated: Group 1: 10 year old patients, Group 2: 15 year old and Group 3: 20 year old. Group with normal blood pressure values, prehypertensive and hypertensive group were analyzed. Regarding the period of follow-up we analyzed: 10/15 years period-children between 10 and 15 years, 15/20 years period-children between 15 and 20 years, and 10/20 years period-children between 10 and 20 years. Significant increase of diastolic blood pressure was noticed for both genders in 10/15 years period of prehypertensive population, while in hypertensive children, boys showed decline in frequency for systolic and diastolic blood pressure and girls only for diastolic. In 15/20 years period there was significant decrease of prehypertensive and significant increase of hypertensive diastolic blood pressure frequency. In 10/20 years period significant reduction in frequency of prehypertensive systolic blood pressure was noticed, while only hypertensive group of boys showed significant reduction regarding systolic blood pressure frequency. Prehypertensive diastolic and hypertensive systolic blood pressure fluctuations are more related to age.

Life course trajectories of systolic blood pressure using longitudinal data from eight UK cohorts

BACKGROUND

Much of our understanding of the age-related progression of systolic blood pressure (SBP) comes from cross-sectional data, which do not directly capture within-individual change. We estimated life course trajectories of SBP using longitudinal data from seven population-based cohorts and one predominantly white collar occupational cohort, each from the United Kingdom and with data covering different but overlapping age periods.

METHODS AND FINDINGS

Data are from 30,372 individuals and comprise 102,583 SBP observations spanning from age 7 to 80+y. Multilevel models were fitted to each cohort. Four life course phases were evident in both sexes: a rapid increase in SBP coinciding with peak adolescent growth, a more gentle increase in early adulthood, a midlife acceleration beginning in the fourth decade, and a period of deceleration in late adulthood where increases in SBP slowed and SBP eventually declined. These phases were still present, although at lower levels, after adjusting for increases in body mass index though adulthood. The deceleration and decline in old age was less evident after excluding individuals who had taken antihypertensive medication. Compared to the population-based cohorts, the occupational cohort had a lower mean SBP, a shallower annual increase in midlife, and a later midlife acceleration. The maximum sex difference was found at age 26 (+8.2 mm Hg higher in men, 95% CI: 6.7, 9.8); women then experienced steeper rises and caught up by the seventh decade.

CONCLUSIONS

Our investigation shows a general pattern of SBP progression from childhood in the UK, and suggests possible differences in this pattern during adulthood between a general population and an occupational population. Please see later in the article for the Editors' Summary.

Changes in anthropometric characteristics and blood pressure during adolescence

BACKGROUND

Studies suggest that sex differences in blood pressure (BP) are established early in life. Sex differences in BP increases that occur during adolescence may be due to differences in changes in anthropometric characteristics.

METHODS

Using sex-specific individual growth models, we assessed the effect of height, body mass index (BMI; kg/m), waist circumference, and triceps and subscapular skinfold thickness on changes in systolic BP in a cohort of 1293 adolescents in Montreal, Canada. BP and anthropometry were assessed biannually (1999/2000, 2002, 2004) at mean ages 12.8, 15.2, and 17.0.

RESULTS

On average, systolic BP increased by 11.1 mm Hg in boys and 3.2 mm Hg in girls during 5 years. Changes in height explained half of the overall increase in systolic BP in boys and virtually all of the increase in systolic BP in girls. No meaningful sex differences were observed in the association of changes in BMI, waist circumference, and triceps and subscapular skinfold thickness with systolic BP change during 5 years. Increases in 1 BMI unit, 1 cm waist circumference, or 1 mm triceps or subscapular skinfold thickness were associated with increases of 0.7, 0.24, 0.3, and 0.4 mm Hg systolic BP, respectively.

CONCLUSIONS

Although sex differences in mean systolic BP changes during adolescence were largely attributable to differences in gains in height, the effect of gaining weight or body fat on systolic BP change was similar in boys and girls.

Project HeartBeat! Concept, development, and design

Major cardiovascular disease (CVD) risk factors begin development in childhood and adolescence. Project HeartBeat! studied early development of these risk factors as growth processes. Growth, body composition, sexual maturation, major CVD risk factors, and cardiac structure and function were monitored every 4 months for up to 4 years among 678 children and adolescents (49.1% girls; 20.1% blacks) aged 8, 11, or 14 years at study entry. All resided in The Woodlands or Conroe TX. Interviews were conducted at entry and annually on diet, physical activity, and health history of participants and their families. Data were collected from 1991 to 1995, and study investigators continue data analysis and reporting. Overlap in ages at examination among three cohorts (aged 8-12, 11-15, and 14-18 years at baseline) and use of multilevel modeling methods permit analysis of some 5500 observations on each principal variable for the synthetic cohort from ages 8 to 18 years. The mixed-longitudinal design provides trajectories of change with age, for total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides; systolic, and fourth-phase and fifth-phase diastolic blood pressure, and left ventricular mass. These trajectories are then related to concurrent measures of multiple indices of body composition and sexual maturation and adjusted for energy intake and physical activity. The data provide valuable insights into risk factor development and suggest a fresh approach to understanding influences on blood lipids, blood pressure, and left ventricular mass during the period of childhood and adolescence, a period of dynamic change in these risk factors.