Dissertation
Dissertation > Medicine, health > Internal Medicine > Heart, blood vessels ( circulatory ) disease > Abnormal blood pressure > Hypertension

Impacts of Hypertension and Related Risk Factors on Early Target Organ Damage in Childhood

Author MengLingHui
Tutor MiJie
School Beijing Union Medical College
Course Epidemiology and Biostatistics,
Keywords Childhood Hypertension Risk factor Target organ damage Screening index
CLC R544.1
Type PhD thesis
Year 2012
Downloads 38
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[Background]Hypertension (HTN) has become an important issue of public health due to its rapid increase in the past two decades. Meanwhile, blood pressure (BP) tracks from childhood to adulthood, and the onset of primary HTN is proved to be traced back to childhood. However, levels of BP are difficult to be efficiently controlled in nearly70%of hypertensive patients. The target organ damages (TOD) are the important problems of HTN study. TOD is the main culprit of the burden of illness and economical load, so primary prevention early from childhood has become the root of the problem.Recognizing the development of HTN at an earlier age may provide physicians with an opportunity to reduce its risk factors early on. Owing to a large variability in repeated BP measurements obtained on a single visit, the diagnosis of HTN in adults is typically based on repeated BP measurements over several visits. Similar to adults, it was recently recommended that elevated BP in children should be determined from at least three separate visits.The health hazard of pediatric HTN not only causes the high risks of adult HTN, but also does damage to target organs of artery, heart, brain and kidney. Studies based on clinic have proved that TOD could be observed even in those hypertensive children with BP elevated mildly. However, most of the TOD in childhood are function damage and may be reversed if effective intervention conducted on the premise of early identifying. In view of this the population-based study was designed to investigate the characteristics of HTN and TOD, and studied the association between HTN and other risk factors and early TOD in children and adolescents.Furthermore, as it’s the case in adults, the white coat and the masked hypertension phenomena appear to be common in children. Therefore, assessment of out of-office BP using either electronic sphygmomanometer or home monitoring is often needed in children and adolescents. Limited evidence exists on the accuracy of 电子血压计for blood pressure measurement in children. An additional content of this study is to verify the accuracy of electric sphygmomanometer in measurements of blood pressure based on population survey.[Objective]1. To screen hypertensive children and adolescents based on population survey and to prove the necessary of repeated measurements on separate occasions in diagnosing HTN in pediatric population;2. To analyze the association between HTN and other risk factors with early TOD in pediatric population and to supply some proof evidence-based in identifying, diagnosing and interposing of the high risk population from early time;3. To verify the assistant between electronic sphygmomanometer and mercury sphygmomanometer in pediatric population based on blood pr electronic sphygmomanometersure population survey.[Methods]Children and adolescents aged3to18years (400in each age group) were recruited using a stratified cluster sampling in2009. This survey was conducted in9kindergartens,7primary and5secondary schools selected from2urban and2rural districts in Beijing. BP was measured according to a standard protocol using a mercury sphygmomanometer on right upper arm in the sitting position. Korotkoff phase1(K1) and4(K4) sounds were used to define systolic BP (SBP) and diastolic BP (DBP), respectively. Heart rate was recorded in beats/min. Meanwhile anthropometric measurements including height (cm), weight (kg) and waist circumference (cm) were obtained with body mass index (BMI) being calculated as weight in kilograms divided by the square of height in meters (kg/m2). Those with a BP in≥95th percentile were screened a second or third time at two-week intervals. A questionnaire, which included questions on physical activity, sleep duration, salt intake, familial history of hypertension, and parental educational levels, was completed.Meanwhile a comparison test between electric sphygmomanometer and mercury sphygmomanometer was conducted in a consecutive pediatric population aged3to18years (100in each age group). Electronic sphygmomanometer (Omron HEM-759P) and mercury sphygmomanometer were used to measure BP two times, respectively, and two instruments were used by turns. Korotkoff K1was recorded as SBP measured by mercury sphygmomanometer (mSBP), K4and K5as DBP by mercury sphygmomanometer (mDBP4and mDBPs), respectively. SBP and DBP measured by lectronic sohygmomanometer were recorded as eSBP and eDBP.Selected hypertensive and double normotensive matched for gender and age screened from the baseline survey were enrolled in the clinical examination on early TOD in2011. The anthropometric measurements including height, weight, SBP, DBP and heart rate were re-measured with BMI being recalculated. All the participants were divided into3groups (consistent NT, BP change, and consistent HTN) according to the BP levels at the baseline and the clinical examination. Moreover, other indexes such as pulse wave velocity (PWV, cm/s), carotid artery intima-media thickness (cIMT), structure of left ventricular and kidney, retinal artery were measured, blood glucose, lipid spectrum, micro albumin in urine,β2-microglobulin and cystatin C were examined.’Elevated BP’was defined as SBP or DBP in the≥95th sex-and age-specific percentile of Chinese pediatric population on all the three occasions.’Hypertension’ was defined as an’elevated BP’ on all three visits. Overweight and obesity in school-aged children were defined according to BMI cutoffs for Chinese children and adolescents. The US2000CDC Growth Chart (CDC2000) was used to clarify the weight status for children aged3-6years. Specifically, BMI in the<85th, between the>85th and<95th, and in the≥95th percentiles was classified as ’normal weight’,’overweight’, and’obese’, respectively. Based on the Chinese national survey of students’ physical quality data, we also calculated BMI percentiles (i.e.<5th,5th-24th,25th-49th,50th-74th,75th-84th,85th-94th, and≥95th).Data of investigation and examination were entered and double checked with Epidata software3.1, and analyzed using SPSS18.0. Data of non-normal distribution were turned into normal distribution through natural logarithm transformation before being analyzed. The methods of analyses included student t test, chi-square test, covariance analysis, multivariable linear regression, and multivariate logistic regression.[Results]1.1A total of6692consecutive subjects, aged3to18years, were enrolled in the screening. The prevalence of an’elevated BP’was18.2,5.1, and3.1%on the first, second, and third visits, respectively. The prevalence of an’elevated BP’in urban (21.0,6.1, and3.7%on the three visits)were higher than that in rural (15.1,4.0,2.5%)(P<0.05). The BP levels and the prevalence of’elevated SBP’ were slightly higher in boys than that in girls on the first and second visits (P<0.05). However, there were no differences between genders on the third visit. Among children with’elevated BP’,36.7,45.7, and50.3%of them had isolated elevated SBP on the first, second, and third visits, and38.8,17.9, and14.2%of them had isolated elevated DBP on the three successive visits, respectively. The prevalence of ’elevated BP’ in3-5age group were16.6%,1.9%, and0.3%for boys, and20.1%,4.1%, and2.2%for girls; in the6-9age group were24.1%,5.8%, and3.0%for boys, and25.4%,5.1%, and3.1%for girls; in the10-12age group were18.8%,6.5%, and4.1%for boys, and16.5%,5.3%, and3.4%for girls, in the13-15age group were17.1%,7.1%, and4.1%for boys, and9.9%,4.2%, and3.0%for girls; and the16-18age group were17.7%,6.9%, and5.5%for boys, and8.6%,4.1%, and3.2%for girls.1.2After adjustment for gender, age, puberty status, heart rate, risks of ’elevated BP’ and HTN on the3visits were increased with the weight statue and the history of HTN of the parents (P<0.05).The odds ratios (ORs) and95%confidence intervals (CIs) for an’elevated BP’were2.64(2.18-3.31),3.95(2.65-5.88),4.54(2.70-7.61) among overweight children.7.07(5.94-8.42),17.23(12.63-23.52), and20,63(13.69-31.09) among obese children, and1.26(0.98-1.61),1.35(0.90-2.02), and1.80(1.15-2.81) among those with a paternal history of hypertension were on each consecutive visit.2.1According to BP levels at baseline and the clinical examination152children resided in group with sustained NT,38in group with BP changed (32from HTN to NT,6from NT to HTN), and48group with sustain HTN. After adjustment for gender, age, and puberty status, the levels of baPWV, LVM, LVMI, and cIMT ascended across the3BP groups (P<0.001), and they were (938±10),(963±21),(1066±19)cm/s for baPWV,(93±2),(110±4),(119±3)g for LVM,(28±1),(32±1),(34±1)g/m2.7for LVMI, and (0.46±0.01),(0.49±0.01),(0.48±0.01)mm for cIMT in the3BP change groups accordingly. The prevalence of TOD increased in the3BP change groups in order. They were7.9%,42.1%, and33.3%for elevated LVM,2.0%,10.5%, and14.6%for elevated LVMI,12.5%,31.6%, and47.9%for elevated cIMT,9.7%,22.9%, and31.1%for elevated hs-CRP, respectively (P<0.001).2.2Adjusted for gender, age, and puberty status, a binary logistic regression was conducted, in which each TOD index was used as dependent variable and the significant effective factors screen through multiple liner regression corresponding to that TOD index were used as independent variables. The results discovered that age was a protective factor for elevated LVM and elevated LVMI, and compared to children with sustained NT the OR (95%CI) were5.27(1.57-17.66) in BP change group and3.28(1.00-10.74) in sustained HTN group. Compared to normal weight children the ORs (95%CIs) in obese children were14.55(4.14-51.22) to suffer from elevated LVM and22.46(2.14-236.20) to suffer from elevated LVMI. Meanwhile age displayed a common protective factor for elevated RWT and LVH. Compared to children in6-9years group the ORs (95%CIs) decreased to0.19(0.06-0.64) for elevated RWT and0.20(0.07-0.63) for LVH in age group of13~15years, and0.08(0.02-0.43) for elevated RWT0.19(0.05-0.71) for LVH in age group16~18years old. The same result was repeated as that age was a protective factor in predicting cIMT increased. The ORs (95%CIs) of elevated cIMT in female is (0.40(1.03-8.09)) compared to male. Compared to children with sustained NT, children with BP changed were at2.88(1.03-8.09) fold and children with sustained HTN were at7.25(2.69-19.58) fold risk of developing elevated cIMT.3. A total of1695children and adolescents participated in the comparison test between electric sphygmomanometer and mercury sphygmomanometer. The levels of eSBP were higher than mSBP (P<0.05), and eDBP were lower than mDBP4but higher than mDBPs (P<0.05) in both boys and girls. The percentages of absolute difference between electric sphygmomanometer and mercury sphygmomanometer in categories of≤5mmHg,≤10mmHg,≤15mmHg were54.2%,82.9%,100%for SBP;42.3%,70.4%,87.2%for K4; and46.1%,70.6%,84.8%for K5, respectively. The partial correlation coefficients adjusted for gender and age were0.716for SBP (P<0.01),0.448for eDBP and mDBPK4(P<0.01) and0.353for eDBP and mDBPK5(P<0.01). Bland-Altman plots showed good consistency between mercury sphygmomanometer and electric sphygmomanometer for both SBP and DBP.[Conclusion]1. It should be recommended that measuring BP on separate visits before characterizing a child as having HTN. Overweight and obesity are the leading cause of pediatric HTN;2. Hypertensive children were at high risk of developing artery stiffness, concentric left ventricular hypertrophy than the normotensive. Initial treatment should focus on weight loss and rectifying the disorder situation of glucolipid metabolism;3. The effects of HTN and other risk factors on early kidney damage and retinal artery stiffness didin’t present statistical significance in current study;4. BaPWV, cIMT, LVM, and LVMI may have potencial value in screening high risk population in children and adolescents;5. Electric sphygmomanometer (Omron HEM-759P) can be used in BP measurement in children and adolescents. However, its application for individual clinical evaluation of HTN needs further studies to evaluate.

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