Twelve-year tracking of blood pressure in Korean school children: the Kangwha Study

Prenatal Household Air Pollution Exposure and Childhood Blood Pressure in Rural Ghana

BACKGROUND

The association between prenatal household air pollution (HAP) exposure and childhood blood pressure (BP) is unknown.

OBJECTIVE

Within the Ghana Randomized Air Pollution and Health Study (GRAPHS) we examined time-varying associations between a) maternal prenatal and b) first-year-of-life HAP exposure with BP at 4 years of age and, separately, whether a stove intervention delivered prenatally and continued through the first year of life could improve BP at 4 years of age.

METHODS

GRAPHS was a cluster-randomized cookstove intervention trial wherein n = 1,414 pregnant women were randomized to one of two stove interventions: a) a liquefied petroleum gas (LPG) stove or improved biomass stove, or b) control (open fire cooking). Maternal HAP exposure over pregnancy and child HAP exposure over the first year of life was quantified by repeated carbon monoxide (CO) measurements; a subset of women (n = 368 ) also performed one prenatal and one postnatal personal fine particulate matter (PM 2.5 ) measurement. Systolic and diastolic BP (SBP and DBP) were measured in n = 667 4-y-old children along with their PM 2.5 exposure (n = 692 ). We examined the effect of the intervention on resting BP z -scores. We also employed reverse distributed lag models to examine time-varying associations between a) maternal prenatal and b) first-year-of-life HAP exposure and resting BP z -scores. Among those with PM 2.5 measures, we examined associations between PM 2.5 and resting BP z -scores. Sex-specific effects were considered.

RESULTS

Intention-to-treat analyses identified that DBP z -score at 4 years of age was lower among children born in the LPG arm (LPG β = - 0.20 ; 95% CI: - 0.36 , - 0.03 ) as compared with those in the control arm, and females were most susceptible to the intervention. Higher CO exposure in late gestation was associated with higher SBP and DBP z -score at 4 years of age, whereas higher late-first-year-of-life CO exposure was associated with higher DBP z -score. In the subset with PM 2.5 measurements, higher maternal postnatal PM 2.5 exposure was associated with higher SBP z -scores.

DISCUSSION

These findings suggest that prenatal and first-year-of-life HAP exposure are associated with child BP and support the need for reductions in exposure to HAP, with interventions such as cleaner cooking beginning in pregnancy. https://doi.org/10.1289/EHP13225.

Association between pre-and postnatal growth and longitudinal trends in serum uric acid levels and blood pressure in children aged 3 to 7 years

Background

Uric acid has been identified as an important factor in the development of hypertension. If low birth weight (LBW) combined with catch-up growth (CUG) is associated with continuously elevated serum uric acid levels (SUA) level trajectories, LBW children who experience CUG may have an increased risk of hypertension later in life. Therefore, this cohort study analyzed longitudinal trends in SUA levels and changes in blood pressure in relation to pre- and postnatal growth over an extended follow-up period.

Methods

This prospective cohort study of 364 children from the Ewha Birth and Growth Cohort assessed the effects of pre- and postnatal growth status on SUA at 3, 5, and 7 years of age using a linear mixed model and the change in blood pressure over the 7-year follow-up period using a generalized linear model (analysis of covariance). CUG was defined as a change in weight (between birth and age 3) with a z-score > 0.67 for LBW subjects. The multivariate model considered sex, gestational age, and uric acid, height, and weight at 3 years of age.

Results

Children with LBW and CUG had higher SUA for the first 7 years of life compared to the normal birth weight group. This trend was particularly evident when comparing LBW children at term to children with normal birth weight. Within the group with LBW at term, children with greater CUG had higher SUA than children with normal birth weight, and this difference increased with age. Changes in the systolic blood pressure between 3 and 7 years of age were higher by 7.9 mmHg in children who experienced LBW and CUG compared with those who had a normal birth weight after adjusting for sex, gestational age, and height, weight, and uric acid at 3 years of age (p-value = 0.08).

Conclusions

The uric acid levels and changes in systolic blood pressure were consistently higher among LBW children who experienced CUG compared with NBW children for the first 7 years of life. LBW children who experienced greater weight gain from birth to age 3 had even higher uric acid levels compared with NBW children.

Effects of Prenatal Growth Status on Subsequent Childhood Renal Function Related to High Blood Pressure

BACKGROUND

Hypertension is one of the major causes of chronic diseases. The effect on high blood pressure (BP) with fetal growth restriction is now well-established. Recent studies suggest that a reduced number of nephrons programmed during the intrauterine period contribute to a subsequently elevated BP, due to a permanent nephron deficit. However, few studies have examined this in children. We investigated the effects of low birth weight (LBW) and preterm birth on the renal function markers related to a high BP in childhood.

METHODS

We used data from 304 children aged 7-12 years who participated in the 2014 Ewha Birth and Growth Cohort survey in Korea. We assessed the serum uric acid, cystatin C, blood urea nitrogen (BUN), creatinine levels, and the estimated glomerular filtration rate (eGFR) in childhood. Anthropometric characteristics, BP in childhood, birth weight and gestational age were collected.

RESULTS

The serum uric acid was significantly higher in LBW children (4.0 mg/dL) than in normal birth weight children (3.7 mg/dL). The cystatin C levels were highest among children who were very preterm (0.89 mg/dL) compared with those who were not (preterm, 0.84 mg/dL; normal, 0.81 mg/dL), although the result was only borderline significant (P for trend = 0.06). Decreased birth weight was found to be significantly associated with an increased serum BUN level in childhood. In the analysis of the effects of renal function on BP, subjects with an eGFR lower than the median value had a significantly higher diastolic BP in childhood (difference = 2.4 mmHg; P < 0.05).

CONCLUSION

These findings suggest that LBW and preterm birth are risk factors for increased serum levels of renal function markers in childhood. Reduced eGFR levels were significantly associated with elevated diastolic BP in childhood. It is necessary to identify vulnerable individuals during their life and intervene appropriately to reduce the risk of an increased BP in the future.

Association Between Serum Levels of Uric Acid and Blood Pressure Tracking in Childhood

BACKGROUND

Recent studies suggest that high levels of serum uric acid of very early life are a result of the in-utero environment and may lead to elevated blood pressure (BP) in adulthood. However, serum uric acid levels can change throughout life. We investigated the effect of serum uric acid levels in childhood on the BP tracking and analysed BP according to changes in serum uric acid levels in early life.

METHODS

A total of 449 children from the Ewha Birth and Growth Cohort study underwent at least 2 follow-up examinations. Data were collected across 3 check-up cycles. Serum uric acid levels, BP, and anthropometric characteristics were assessed at 3, 5, and 7 years of age.

RESULTS

Children with a serum uric acid level higher than the median values had significantly increased systolic BP (SBP) and diastolic BP at 3 years of age. Baseline serum uric acid levels measured at 3 years of age, significantly affected subsequent BP in the sex and body mass index adjusted longitudinal data analysis (P < 0.05). Considering the changing pattern of serum uric acid over time, subjects with high uric acid levels at both 3 and 5 years of age had the highest SBP at 7 years of age.

CONCLUSIONS

These findings suggest the importance of maintaining an adequate level of serum uric acids from the early life. Appropriate monitoring and intervention of uric acid levels in a high-risk group can reduce the risk of a future increased BP.

A 24-year follow-up study of blood pressure tracking from childhood to adulthood in Korea: the Kangwha Study

PURPOSE

A number of longitudinal studies have tracked blood pressure over time in children and adults. Although there are a few blood pressure tracking studies for Asian populations, they are all relatively short-term studies with around only 10 years of follow-up. Accordingly, we assessed the stability of blood pressure tracking from childhood to adulthood over a 24-year follow-up period among participants in the Kangwha Study.

MATERIALS AND METHODS

The Kangwha Study was a community- based prospective cohort study that started in 1986 in Kangwha County, South Korea. The study dataset included 14 blood pressure measurements over a 24-year period from 266 (123 male and 143 female) participants who completed the 2010 examination. All participants were 7 years old when the study began and were followed for the next 24 years.

RESULTS

The tracking coefficient (95% confidence interval) for systolic blood pressure was 0.81 (0.52-1.11) in men and 0.72 (0.51-0.92) in women; diastolic blood pressure was 0.53 (0.26-0.80) in men and 0.33 (0.15-0.52) in women. After adjusting for body mass index, the tracking coefficient for systolic blood pressure was 0.68 (0.39-0.97) in men and 0.67 (0.44-0.89) in women; diastolic blood pressure was 0.51 (0.24-0.78) in men and 0.33 (0.15-0.51) in women. All tracking coefficients were statistically significant (p<0.001).

CONCLUSION

In this 24-year longitudinal study, we confirmed the stability of blood pressure tracking from childhood to adulthood for participants in the Kangwha Study.

Association between depressive symptoms and bone stiffness index in young adults: the Kangwha study

OBJECTIVE

Young adulthood is an important period for both bone and mental health. This study investigated the association between depressive symptoms and bone density in apparently healthy Korean men and women aged 29-32 years.

METHODS

This study is a cross-sectional analysis of data from 123 men and 133 women who completed follow-up examinations of the Kangwha study in 2010-2011. Bone stiffness index (SI) was measured at the os calcis using a quantitative ultrasound device. Depressive symptoms were evaluated using the Korean version of the Beck Depression Inventory (K-BDI) and classified as normal (K-BDI <10), mild (K-BDI 10-15), and moderate to severe (K-BDI ≥16).

RESULTS

Moderate to severe depressive symptoms were prevalent among 11.4% of men and 19.6% of women. Higher K-BDI scores were significantly correlated to SI in men, before (ρ = -0.286, p = 0.001) and after (ρ = -0.228, p = 0.013) adjustment for covariates. Men with depressive symptoms tended to have a lower SI; multivariate-adjusted mean SI in men with normal, mild, and moderate to severe depressive symptoms was 104.1±3.1, 100.9±5.9, and 94.1±7.8, respectively (p for trend = 0.021). In contrast, no significant correlations were identified in women.

CONCLUSIONS

Depressive symptoms were significantly associated with lower SI in men, but not in women. Further studies are necessary to evaluate the impact of depression on developing osteoporosis or osteoporotic fractures later in life.

Hypertension in children and adolescents: epidemiology and pathogenesis

High blood pressure is one among the leading contributors to burden of disease globally. Approximately 54 % of stroke and 47 % of ischemic heart disease events worldwide were attributable to high blood pressure in the year 2001. There is deficiency of data on the long-term outcome of hypertension in children. In spite of this, there is sufficient evidence to suspect that the health risks of hypertension in pediatric patients are substantial. Hypertension in childhood is known to result in hypertension in young adulthood. The epidemiology of hypertension in children is well represented from various studies conducted across continents. Factors like methodological issues in measurement, socio demographic differences, adiposity levels and ethnicity appear to influence the distribution of blood pressure as well as prevalence of hypertension in children. The etio-pathogenesis of essential (primary) hypertension is multi-factorial in origin. Obesity, insulin resistance, activation of sympathetic nervous system, alterations in sodium homeostasis, renin-angiotensin system changes, changes in vascular smooth muscle structure and reactivity, high serum uric acid levels, genetic factors and fetal programming have been reported to contribute to this disorder. The causes of secondary hypertension vary with age. Renal disorders and coarctation of the aorta are the most common causes of hypertension in children up to age 6 y. In older children, renal parenchymal disease remains the most frequent cause of increased blood pressure. Other causes of hypertension in children are relatively rare and include systemic arteritis and certain tumours, endocrine dysfunction, and neurologic disorders.

Baseline autonomic nervous system arousal and physical and relational aggression in preschool: the moderating role of effortful control

The current study investigates whether established associations between physical aggression and low autonomic nervous system arousal, as indexed by heart rate and blood pressure, also apply to the study of the development of relational aggression. Baseline heart rate and blood pressure were collected in two samples of preschoolers, and teachers reported on classroom physical and relational aggression. In Study 1, lower systolic and diastolic blood pressure were related to increased engagement in relational aggression among older preschoolers. In Study 2, lower heart rate and blood pressure predicted increased engagement in classroom physical and relational aggression concurrently and across a preschool year in some cases. Low baseline arousal-aggression associations were strongest for children with poorer self-regulation abilities, whereas high self-regulation appeared to protect children with low heart rate and blood pressure from engagement in aggressive classroom behavior. These findings suggest the utility of examining baseline physiological measures in the study of relational aggression as well as physical aggression. Implications for interventions targeted to physical and relational aggression in early childhood are discussed.

Relationship between height and blood pressure in Japanese schoolchildren

BACKGROUND

Blood pressure examinations for health education use have been conducted at several schools in Japan. It has been reported that blood pressure is closely associated with bodyweight and height in US children. The aim of the present paper was to evaluate the association between height and blood pressure in Japanese schoolchildren.

METHODS

In Iwata city in Japan, blood pressure screening was conducted by the school administration. A total of 98.9% (10,152/10,270 children) of all fifth (10-year-olds) and ninth graders (14-year-olds) residing in the Old Iwata area from 2002 to 2007 were analyzed.

RESULTS

In 10-year-old and 14-year-old boys, regression analysis indicated that a positive correlation between weight and blood pressure was the strongest among the three body size indices (height, weight, and body mass index), but the association between height and blood pressure was also significant. For girls from both the 10 and 14 year age groups, the correlation of weight and blood pressure was stronger than those for the other body size indices, but there were also significant associations between height and blood pressure, except for height and diastolic blood pressure in the 14-year-olds.

CONCLUSIONS

There is a significant positive relationship between height and blood pressure. Further study is necessary to provide a blood pressure reference based on height in the Japanese program to prevent children from developing lifestyle-related risk factors.

Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis

BACKGROUND

A large number of studies have examined the tracking of blood pressure (BP) from childhood to adulthood, but the reported findings are inconsistent and few systematic analyses have been conducted.

METHODS AND RESULTS

We conducted a systematic search of PubMed for studies that examined the tracking of BP from childhood to adulthood published between January 1970 and July 2006. From 301 retrieved papers, 50 cohort studies met our inclusion criteria and provided 617 data points (Pearson/Spearman correlation coefficients) for systolic BP (SBP) and 547 data points for diastolic BP (DBP) for our meta-analysis. Information on sample characteristics and BP measurement protocols was extracted. Fisher z transformation and random-effects meta-regression analysis were conducted. The reported BP tracking correlation coefficients varied from -0.12 to 0.80 for SBP and from -0.16 to 0.70 for DBP, with an average of 0.38 for SBP and 0.28 for DBP. BP tracking varied significantly by baseline age and length of follow-up. The strength of BP tracking increased with baseline age by 0.012 for SBP (P<0.001) and 0.009 for DBP (P<0.001) and decreased with follow-up length by 0.008 for SBP (P<0.001) and 0.005 for DBP (P<0.001). BP tracking did not vary markedly across the number of BP measurements or race/population groups.

CONCLUSIONS

Data from diverse populations show that the evidence for BP tracking from childhood into adulthood is strong. Childhood BP is associated with BP in later life, and early intervention is important.

Impacts of Measurement Protocols on Blood Pressure Tracking From Childhood Into Adulthood

The best approach for blood pressure (BP) measurement in children remains controversial, specifically regarding the choice of Korotkoff phase 4 versus Korotkoff phase 5 for diastolic BP (DBP) and the use of automated devices. To examine the impacts of different BP measurement protocols on BP tracking from childhood into adulthood, we conducted a meta-analysis of 50 related studies published between 1970 and 2006 identified based on a systematic search of PubMed. These studies provided 617 data points (tracking correlation coefficient, our outcome variable) for systolic BP and 547 data points for DBP for our meta-analysis. The explanatory variables included the use of Korotkoff phase 4/Korotkoff phase 5, BP device, and number of BP measurements per visit. Analyses were adjusted for potential confounders, including sex, baseline age, follow-up length, publication year, and study country. Tracking correlation coefficients for DBP measured using Korotkoff phase 4 was higher than that of Korotkoff phase 5 by 0.035 but not significant. DBP tracking assessed by automated device was higher than that of Korotkoff phase 5 by 0.152 ( P =0.024) and higher than the mercury manometer by 0.223 ( P =0.005). BP tracking was slightly higher with multiple BP measurements per visit, but measurements of ≥3 times did not improve the tracking further compared with 2 measurements. Although policy-making bodies currently recommend the use of Korotkoff phase 5 to assess DBP in children, our metaregression analysis did not support the recommendation. In general, Korotkoff phase 4 seems to be different from Korotkoff phase 5, and automated device is a promising approach for BP assessment in childhood.

Haplotype-based score test for linkage in nuclear families

Background

To look for genetic linkage between angiotensin-I converting enzyme(ACE) gene and hypertension in a Korean adolescent cohort, we developed a powerful test using the covariances between marginal differences and their variances in a transmission/non-transmission table.

Results

We estimated haplotype frequencies using the parental and affected offspring's genotypes and then constructed a transmission/non-transmission table for the parental haplotypes transmitted to the offspring. We then proposed a test for checking the marginal homogeneity in the table. Because the cells in the table were dependent due to the uncertainty of the parental haplotypes, we adopted a randomization procedure to estimate the significance of the observed test statistic. Simulations show that our test performs well on a nominal level and has a monotone power, which increases as the relative risk increases. With our test, there was no evidence of genetic linkage between the ACE gene and hypertension in the Korean adolescent cohort.

Conclusion

We developed a score test for linkage and used simulations to demonstrate that our test performs well at a nominal level. Under some situations where the diversity of haplotypes is low, the proposed test gained a little power over the method based on only variances between marginal differences in a transmission/non-transmission table.

Genetics of essential hypertension: from families to genes

Family studies demonstrated the contribution of genetic factors to the development of primary hypertension. However, the transition from this phenomenologic-biometric approach to the molecular-genetic one is more difficult. This last approach is mainly based on the Mendel paradigm; that is, the dissection of the poligenic complexity of hypertension is brought about on the assumption that the individual genetic variants underlying the development of hypertension must be more frequent in hypertensive patients than in controls and must cosegregate with hypertension in families. The validity of these assumptions was clearly demonstrated in the so-called monogenic form of hypertension. However, because of the network of the feedback mechanisms regulating BP, it is possible that that the same gene variant may have an opposite effect on BP according to the genetic and environmental backgrounds. Independent groups of observations (acute BP response to saline infusion, incidence of hypertension in a population follow-up of 9 yr, age-related changes on BP) discussed in this review suggest a positive answer to this question. Therefore the impact of a given genetic variant on BP level must be evaluated within the context of the appropriate genetic epistatic interactions. A negative finding or a minor genetic effect in a general population may become a major gene effect in a subset of people with the appropriate genetic and environmental backgrounds.

Tracking of systolic blood pressure during childhood: a 15-year follow-up population-based family study in eastern Finland

OBJECTIVES

To investigate the tracking of systolic arterial blood pressure (SBP) during childhood.

DESIGN AND SETTING

All children born during 1981-82 in a rural community of eastern Finland were followed at the ages of 6 months, 7 and 15 years (SBP-6m, SBP-7y, SBP-15y). One hundred and thirty-eight out of 205 children completed the full follow-up period, of which 100 (45 girls) were included in the analysis with complete data.

MAIN OUTCOME MEASURES

SBP (mmHg).

RESULTS

SBP-6m was associated with SBP-7y (r = 0.715; P < 0.001) and with SBP-15y (r = 0.238; P = 0.017) and SBP-7y was associated with SBP-15y (r = 0.348; P < 0.001). Adjustment for confounders did not change these results. Children at the highest tertile of SBP-6m had a higher probability of being at the highest tertile of SBP-7y [relative risk (RR) = 4.3; 95% confidence interval (CI), (2.4-7.6)] and SBP-15y [RR = 1.9; 95% CI, (1.1-3.3)]. Children at the highest tertile of SBP-7y had a higher probability of being at the highest tertile of SBP-15y [RR = 2.6 (1.5-4.6)]. The regression analysis showed a significant main effect on SBP-15y for birth weight (negative association), male gender, current body mass index (BMI), change of BMI between the ages of 7 years and 15 years, SBP-6m, SBP-7y and the mean SBP between the ages of 6 months and 7 years (all with positive association). Children with family history of hypertension appear to have a higher SBP during childhood; however, this association did not reach a significant level.

CONCLUSIONS

The study confirmed the tracking of SBP during childhood. Birth weight was inversely associated with SBP-15y. Family history of hypertension was not significantly associated with SBP during childhood.