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Original Article

Prevalence of hypertension and hypertension phenotypes after three visits in Chinese urban children

Dong, Jiea; Dong, Hongbob; Yan, Yinkunb; Cheng, Hongc; Zhao, Xiaoyuanc; Mi, Jieb,c

Author Information
Journal of Hypertension: July 06, 2022 - Volume - Issue - 10.1097/HJH.0000000000002977
doi: 10.1097/HJH.0000000000002977

Abstract

INTRODUCTION

Hypertension (HTN) is the leading modifiable risk factor of cardiovascular diseases (CVD), which explains the major reason of death and morbidity in China [1]. The latest nationwide study between 2012 and 2015 showed that the prevalence of hypertension among Chinese adults has increased to 23.2% [2]. Though the US Preventive Services Task Force claimed that there is insufficient evident to evaluate the balance of benefits and harms of screening for high blood pressure in children [3], strong evidence indicates that blood pressure (BP) in childhood can moderately track into adulthood [4]. Elevated BP in childhood can also predict subclinical vascular damage and left ventricular geometric remodeling, and also can increase the risk of premature death in adulthood [5–7]. Combining the fact that the age of stroke onset in low-income Chinese tends to be younger from 1992 to 2014 [8], it is critical to detect and manage hypertension early in life to reduce the risk of target organ damage and CVD events in later adult life.

There have been many school-based epidemiological surveys on the prevalence of HTN among Chinese children and adolescents in recent years but the results varies greatly from 3.1 to 16.7% [9–14]. Though several guidelines on pediatric hypertension have recommended that at least three separate visits should be taken to confirm the diagnosis of hypertension in children [15–17]; most studies only had BP measurement at only one occasion [10–14], which may overestimate the true prevalence of HTN in Chinese youth. In addition, evidence from young adults indicated different hypertension subtypes had different correlation strengths with CVD events [18,19]. Therefore, the aim of this study was to evaluate the prevalence of hypertension and hypertension subtypes in a nationwide school-based sample in Chinese children and adolescents by three separate visits.

METHODS

Participants

The China Child and Adolescent Cardiovascular Health (CCACH) study is a large-scale school-based cross-sectional study conducted from 2012 to 2015 [20,21]. The primary aim of this survey was to assess the prevalence of hypertension among Chinese urban students by following three separate visits. Six major cities, including Beijing, Changchun, Jinan, Shanghai, Chongqing, and Chengdu were nonrandomly chosen to participate in this study. Several schools were randomly selected to ensure that about 300 participants from each of the 24 sex/grade strata (boys/girls from grade 1 to grade 12) were recruited in each city.

Participants who were older than 18 years were excluded for analyses considering the inconsistent diagnosis criteria for children and adults. Children who reported to have HTN or HTN-related diseases in the questionnaires, including kidney disease, heart disease, diabetes, and thyroid disease were excluded.

This study was approved by the Institutional Review Board and Ethics Committee of the Capital Institute of Pediatrics. Written informed consents were obtained from all the participants or their guardians (< 12years).

Measurements

An open-ended questionnaire was completed by each participant, which identified sex, birthdate, history of diseases, lifestyle habits, and family history of hypertension. Height was measured by using wall-mounted stadiometers without shoes. Weight was measured by using beam scales with light indoor clothing. BMI was calculated as weight (kg) divided by the square of height in meters.

Three consecutive BP readings were obtained from each participant on the right arm in the morning at the initial screen in a quiet classroom in each school without the class teachers or the principals present, using an appropriate cuff size according to the manufacturer's instructions by trained staff in casual clothes from the local research team in each city. Students were asked to empty their bladder and had at least 5 min rest before BP measurements. During the entire measurements, participants were seated with their legs uncrossed, their right arm was supported at the heart level, and they were recommended to be relaxed and keep quiet. The oscillometric device (Omron HEM-7012, OMRON, Kyoto, Japan) used in this study had been validated in children and adolescents according to the Association for the Advancement of Medical Instrument 2009 (DOI: 10.16439/j.cnki.1673–7245.2013.02.036) [22]. The average of the last two readings was used for diagnosis and statistical analysis. According to the BP references for Chinese children and adolescents in 2010 (CN 2010) [23], students with BP at least 95th percentile underwent a second set of BP measurements at least 1 week later, and then a third screening if BP was more than 95th percentile at the second screening.

Definition and diagnosis

Elevated blood pressure was defined as systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) at least sex-specific and age-specific 95th percentiles of the CN 2010 from visit 1 to visit 3. At the first visit, BP status was also categorized by other three commonly used BP references for children, including the Chinese references 2017 (CN 2017), the US fourth report, and the AAP 2017 [17]. BMI were categorized into nonoverweight (<P85th), overweight (P85th to P95th) and obesity (≥P95th) according to the American Centers for Disease Control (CDC) and Prevention growth charts in 2000 [24]. Family history of hypertension was defined as father or mother had hypertension. Definitions of covariates, including sleep time, physical activity, smoking, drinking, diet score, family income per capita, and parents’ education levels were provided in Supplemental Table 1, https://links.lww.com/HJH/B742.

Statistical analysis

Z-scores of height, weight, and BMI were calculated according to the CDC growth charts in 2000 [25]. Continuous variables were presented as means and standard deviations. Categorical variables were presents as counts and percentages. Two sample Student's t tests or chi-square test were used to compare the differences across subgroups. Binary logistic regression was used to examine the related factors of hypertension, ISH, and diastolic hypertension adjusting for covariates. All the analyses were conducted by SPSS, version 20.0 (IBM SPSS, Inc., Armonk, New York, USA). A two-tailed α of less than 0.05 was considered as statistically significant.

RESULTS

The final population included in analyses consisted of 44396 children and adolescents aged 6–17 years, 50.9% of whom were boys. Table 1 shows the basic characteristics of this study population. The average age of our participants was 12 ± 3.3 years. Compared with boys, girls had lower height z score (0.35 vs. 0.17, P< 0.001), weight z score (0.48 vs. 0.10, P< 0.001), and BMI z score (0.34 vs. 0.01, P < 0.001). The prevalence of overweight and obesity in the overall population was 13.4 and 10.6%, respectively. Almost half of our participants had family history of hypertension (46.7%). At the second and the third visit, boys obviously had higher SBP but lower DBP than girls, with P values less than 0.001.

TABLE 1 - Basic characteristics of all participants
All Boy Girl P value
N 44396 22 607 21 789
Age (year) 12.0 ± 3.3 11.9 ± 3.3 12.0 ± 3.3 0.003
Height (cm) 150.4 ± 17.0 152.4 ± 18.5 148.4 ± 14.9 <0.001
Height z score 0.26 ± 1.01 0.35 ± 1.03 0.17 ± 0.98 <0.001
Weight (kg) 45.5 ± 17.0 48.1 ± 18.9 42.8 ± 14.2 <0.001
Weight (z score) 0.29 ± 1.09 0.48 ± 1.14 0.10 ± 0.99 <0.001
BMI (kg/m2) 19.4 ± 4.1 19.9 ± 4.4 18.9 ± 3.6 <0.001
BMI z score 0.17 ± 1.14 0.34 ± 1.20 0.01 ± 1.04 <0.001
BMI status
 Normal weight 33 756 (76.0) 15 505 (68.6) 18251 (83.8) <0.001
 Overweight 5956 (13.4) 3568 (15.8) 2388 (11.0)
 Obesity 4684 (10.6) 3534 (15.6) 1150 (5.3)
FHTN 17 934 (46.7) 8833 (45.5) 9101 (47.8) <0.001
The first visit
 SBP (mmHg) 110.3 ± 11.7 112.6 ± 12.4 107.9 ± 10.5 <0.001
 DBP (mmHg) 64.5 ± 7.9 64.4 ± 7.9 64.7 ± 7.8 <0.001
The second visita
 SBP (mmHg) 120.7 ± 12.2 123.4 ± 12.7 117.2 ± 10.4 <0.001
 DBP (mmHg) 69.9 ± 7.8 69.4 ± 7.8 70.5 ± 7.7 <0.001
The third visitb
 SBP (mmHg) 124.2 ± 12.3 126.8 ± 12.5 120.3 ± 10.9 <0.001
 DBP (mmHg) 71.1 ± 7.7 70.3 ± 7.8 72.3 ± 7.5 <0.001
Data are presented as mean ± SD or n (%). FHTN, family history of hypertension.
an = 6816
bn = 2987.

At the first visit, the prevalence of hypertension reached as high as to 16.6, 17.1, 10.9, and 15.4% by CN 2010, CN 2017, the United States Fourth report, and the AAP 2017, respectively. Boys had higher prevalence of hypertension and ISH than girls by all the four references (P< 0.001). But the prevalence of IDH was lower in boys than that in girls (P < 0.05) (Table 2). After three visits, the prevalence of hypertension by these four references was 4, 3.7, 2.2, and 3.3%, respectively (Supplemental Table 2, https://links.lww.com/HJH/B743)

TABLE 2 - Prevalence of hypertension and hypertension subtypes by four commonly used references in children at the first visit, n (%)
Overall Boy Girl P value
Hypertension
 CN 2010 7368 (16.6) 4166 (18.4) 3202 (14.7) <0.001
 CN 2017 7594 (17.1) 4216 (18.6) 3378 (15.5) <0.001
 Fourth report 4824 (10.9) 2959 (13.1) 1865 (8.6) <0.001
 AAP 2017a 6815 (15.4) 4308 (19.1) 2507 (11.5) <0.001
ISH
 CN 2010 4553 (10.3) 2846 (12.6) 1707 (7.8) <0.001
 CN 2017 4393 (9.9) 2658 (11.8) 1735 (8.0) <0.001
 Fourth report 3596 (8.1) 2395 (10.6) 1201 (5.5) <0.001
 AAP 2017a 4407 (9.9) 3086 (13.7) 1321 (6.1) <0.001
IDH
 CN 2010 1007 (2.3) 416 (1.8) 591 (2.7) <0.001
 CN 2017 1223 (2.8) 564 (2.5) 659 (3.0) 0.001
 Fourth report 395 (0.9) 165 (0.7) 230 (1.1) <0.001
 AAP 2017a 867 (2.0) 367 (1.6) 500 (2.3) <0.001
SDH
 CN 2010 1808 (4.1) 904 (4.0) 904 (4.1) 0.424
 CN 2017 1978 (4.5) 994 (4.4) 984 (4.5) 0.543
 Fourth report 833 (1.9) 399 (1.8) 434 (2.0) 0.078
 AAP 2017a 1541 (3.5) 855 (3.8) 686 (3.2) <0.001
ISH, isolated systolic hypertension; IDH, isolated diastolic hypertension; SDH, systolic and diastolic hypertension.
an = 44320.

Table 3 presents the prevalence of hypertension and hypertension phenotypes in subgroups diagnosed by Chinese reference 2010 from the first visit to the third visit. After a median interval of 65 days [Interquartile range, IQR: 22–77, days] between the first and the second visits, the prevalence of hypertension decreased to 7.2% at the second visit. Then after 24 days [IQR: 12–89, days], the prevalence of hypertension at the third visit in the overall population, boys, and girls was 4, 5, and 3%, respectively; The prevalence of ISH, which usually reflects essential hypertension was 2.7, 3.7, and 1.6%, respectively; the prevalence of IDH, which usually reflects secondary hypertension was 0.3, 0.3, and 0.4%, respectively, which were quite rare. In children aged 6–11 years, boys had slightly higher prevalence of hypertension than girls (3.3 vs. 2.8%), mainly because of ISH (2.2 vs. 1.6%). In children aged 12–17 years, the prevalence of hypertension in boys was more than twice in girls (6.6 vs. 3.2%), also mainly because of ISH (5.2 vs. 1.7%). In normal weight children, 2.2% participants were hypertensive after three BP visits, and this figure substantially increased to 6.2 and 14.4% in the overweight and the obese children. Comparisons between the followed-up and the dropped-out at visit 2 (n = 552) and visit 3 (n = 196) are provided in Supplemental Table 3a and b, http://link-s.lww.com/HJH/B744, and no substantial discrepancies were observed.

TABLE 3 - Prevalence of hypertension and hypertension phenotypes by Chinese references 2010 at three visits, n (%)
First visit Second visita Third visitb
All Boy Girl All Boy Girl All Boy Girl
Hypertension
 Overall 7368 (16.6) 4166 (18.4) 3202 (14.7) 3183 (7.2) 1933 (8.6) 1250 (5.7) 1790 (4.0) 1129 (5.0) 661 (3.0)
 Age group
  6–11 years 3640 (16.7) 1862 (16.7) 1778 (16.8) 1333 (6.1) 714 (6.4) 619 (5.8) 668 (3.1) 370 (3.3) 298 (2.8)
  12–17 years 3728 (16.5) 2304 (20.1) 1424 (12.7) 1850 (8.2) 1219 (10.6) 631 (5.6) 1122 (5.0) 759 (6.6) 363 (3.2)
 BMI status
  Normal 3927 (11.6) 1848 (11.9) 2079 (11.4) 1415 (4.2) 681 (4.4) 734 (4.0) 743 (2.2) 369 (2.4) 374 (2.0)
  Overweight 1449 (24.3) 848 (23.8) 601 (25.2) 651 (10.9) 386 (10.8) 265 (11.1) 371 (6.2) 219 (6.1) 152 (6.4)
  Obesity 1992 (42.5) 1470 (41.6) 522 (45.4) 1117 (23.8) 866 (24.5) 251 (21.8) 676 (14.4) 541 (15.3) 135 (11.7)
ISH
 Overall 4553 (10.3) 2846 (12.6) 1707 (7.8) 2074 (4.7) 1406 (6.2) 668 (3.1) 1196 (2.7) 837 (3.7) 359 (1.6)
 Age group
  6–11 years 2019 (9.3) 1084 (9.7) 935 (8.8) 778 (3.6) 445 (4.0) 333 (3.1) 415 (1.9) 244 (2.2) 171 (1.6)
  12–17 years 2534 (11.2) 1762 (15.4) 772 (6.9) 1296 (5.7) 961 (8.4) 335 (3.0) 781 (3.5) 593 (5.2) 188 (1.7)
 BMI status
  Normal 2392 (7.1) 1288 (8.3) 1104 (6.0) 853 (2.5) 480 (3.1) 373 (2.0) 447 (1.3) 249 (1.6) 198 (1.1)
  Overweight 952 (16.0) 617 (17.3) 335 (14.0) 447 (7.5) 291 (8.2) 156 (6.5) 255 (4.3) 166 (4.7) 89 (3.7)
  Obesity 1209 (25.8) 941 (26.6) 268 (23.3) 774 (16.5) 635 (18.0) 139 (12.1) 494 (10.5) 422 (11.9) 72 (6.3)
IDH
 Overall 1007 (2.3) 416 (1.8) 591 (2.7) 275 (0.6) 110 (0.5) 165 (0.8) 147 (0.3) 69 (0.3) 78 (0.4)
 Age group
  6–11 years 570 (2.6) 269 (2.4) 301 (2.8) 155 (0.7) 75 (0.7) 80 (0.8) 84 (0.4) 44 (0.4) 40 (0.4)
  12–17 years 437 (1.9) 147 (1.3) 290 (2.6) 120 (0.5) 35 (0.3) 85 (0.8) 63 (0.3) 25 (0.2) 38 (0.3)
 BMI status
  Normal 706 (2.1) 255 (1.6) 451 (2.5) 190 (0.6) 68 (0.4) 122 (0.7) 89 (0.3) 37 (0.2) 52 (0.3)
  Overweight 142 (2.4) 59 (1.7) 83 (3.5) 34 (0.6) 12 (0.3) 22 (0.9) 26 (0.4) 11 (0.3) 15 (0.6)
  Obesity 159 (3.4) 102 (2.9) 57 (5.0) 51 (1.1) 30 (0.8) 21 (1.8) 32 (0.7) 21 (0.6) 11 (1.0)
SDH
 Overall 1808 (4.1) 904 (4.0) 904 (4.1) 834 (1.9) 417 (1.8) 417 (1.9) 447 (1.0) 223 (1.0) 224 (1.0)
 Age group
  6–11 years 1051 (4.8) 509 (4.6) 542 (5.1) 400 (1.8) 194 (1.7) 206 (1.9) 169 (0.8) 82 (0.7) 87 (0.8)
  12–17 years 757 (3.3) 395 (3.4) 362 (3.2) 434 (1.9) 223 (1.9) 211 (1.9) 278 (1.2) 141 (1.2) 137 (1.2)
 BMI status
  Normal 829 (2.5) 305 (2.0) 524 (2.9) 372 (1.1) 133 (0.9) 239 (1.3) 207 (0.6) 83 (0.5) 124 (0.7)
  Overweight 355 (6.0) 172 (4.8) 183 (7.7) 170 (2.9) 83 (2.3) 87 (3.6) 90 (1.5) 42 (1.2) 48 (2.0)
  Obesity 624 (13.3) 427 (12.1) 197 (17.1) 292 (6.2) 201 (5.7) 91 (7.9) 150 (3.2) 98 (2.8) 52 (4.5)
IDH, isolated diastolic hypertension; ISH, isolated systolic hypertension; SDH, systolic and diastolic hypertension. an = 6816. bn = 2987.

In boys, the proportions of ISH slightly increased from visit 1 to visit 3 (68.3, 72.7, 74.1%, respectively), and the proportions of SDH (21.7, 21.6, and 19.8% from visit 1 to visit 3, respectively) and IDH slightly decreased (10, 5.7, and 6.1% from visit 1 to visit 3, respectively). In girls, the proportions of ISH were similar among three visits (53.3, 53.4, and 54.3%, respectively), and the proportions of SDH slightly increased (28.2, 33.4, and 33.9%, respectively) whereas IDH slightly decreased (18.5, 13.2, and 11.8%, respectively) from visit 1 to visit 3. Figure 1 illustrates the proportions of hypertension phenotypes by age group and weight status at the third visit. In boys, the proportions of ISH, SDH, and IDH were 65.9, 22.2, 11.9% in the 6–11 years, 78.1,18.6, 3.3% in the 12–17years, respectively. In girls, the proportions of ISH, SDH, and IDH were 57.4, 29.2,13.4% in the 6–11 years, and 51.8, 37.7, 10.5% in the 12–17years, respectively. The proportions of ISH gradually increased from the normal weight to the obese in boys (67.5, 75.8, 78%, respectively). In girls, the overweight had the highest proportion of ISH (58.6%) and the obese had the highest proportion of SDH (38.5%) compared with the other two groups.

F1
FIGURE 1:
Proportions of hypertension phenotypes at the third visit by age group and weight status. (a) Boys by age group; (b) girls by age group; (c) boys by weight status; (d) girls by weight status. IDH, isolated diastolic hypertension. ISH, isolated systolic hypertension; SDH, systolic and diastolic hypertension.

Results of binary logistic regression are presented in Table 4. Compared with the younger ones, the odds ratio for hypertension were 2.10 [95% confidence interval (CI) 1.77–2.49) for older boys, 1.14 (95% CI 0.91–1.43) for older girls adjusted for covariates after three BP visits. Older age was positively associated with ISH in boys at three visits (OR at the third visit: 2.47, 95% CI 2.02–3.01), rather than in girls. Though older age was a protective factor of DHTN in both boys and girls at the first visit [OR in boys: 0.85 (95% CI 0.72 – 0.99); OR in girls: 0.73 (95% CI 0.62–0.85)], it turned into a nonsignificant risk factor at the third visit. Overweight or obesity was positively correlated with hypertension or hypertension phenotypes in both boys and girls at all three visits, with ORs increased from the first visit to the third visit. Overweight girls had slightly higher ORs of ISH and DHTN than boys. The associations between obesity and ISH were stronger in boys than that in girls [OR in boys: 9.67 (95% CI 8.18–11.43]; OR in girls: 6.59 (95% CI 4.97–8.75), at the third visit], whereas obese girls had a stronger association with DHTN than boys [OR in girls: 6.78 (95% CI 5.01–9.17); OR in boys: 4.82 (95% CI 3.71– 6.26), at the third visit]. Family history of hypertension was a risk factor for hypertension or hypertension phenotypes both in boys and girls after three BP screenings.

TABLE 4 - Associations of age group, BMI status, and family history of hypertension with childhood hypertension in boys and girls at three BP visits, odds ratio (95% confidence interval)a
The first visit The second visit The third visit
Boy Girl Boy Girl Boy Girl
OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P OR (95% CI) P
Hypertension
 Age group
  6–11 years Ref Ref Ref Ref Ref Ref
 12–17 years 1.37 (1.25–1.51) <0.001 0.78 (0.70–0.87) <0.001 1.82 (1.60–2.08) <0.001 0.96 (0.81–1.13) 0.599 2.10 (1.77–2.49) <0.001 1.14 (0.91–1.43) 0.245
 BMI status
  NW Ref Ref Ref Ref Ref Ref
  OWT 2.36 (2.15–2.59) <0.001 2.61 (2.36–2.90) <0.001 2.80 (2.45–3.20) <0.001 3.08 (2.65–3.57) <0.001 2.87 (2.41–3.41) <0.001 3.41 (2.81–4.15) <0.001
  OB 5.48 (5.03–5.96) <0.001 6.39 (5.63–7.26) <0.001 7.99 (7.14–8.94) <0.001 7.15 (6.08–8.42) <0.001 8.55 (7.41–9.87) <0.001 7.13 (5.76–8.82) <0.001
 Family history of hypertension
  No Ref Ref Ref Ref Ref Ref
  Yes 1.24 (1.10–1.39) <0.001 1.21 (1.07–1.38) 0.003 1.44 (1.24–1.67) <0.001 1.53 (1.29–1.82) <0.001 1.60 (1.34–1.92) <0.001 1.77 (1.42–2.20) <0.001
ISH
 Age group
  6–11 years Ref Ref Ref Ref Ref Ref
  12–17 years 1.68 (1.51–1.88) <0.001 0.87 (0.75–1.00) 0.052 2.25 (1.93–2.62) <0.001 1.06 (0.85–1.32) 0.619 2.47 (2.02–3.01) <0.001 1.05 (0.78–1.41) 0.759
 BMI status
  NW Ref Ref Ref Ref Ref Ref
  OWT 2.42 (2.17–2.68) <0.001 2.56 (2.24–2.91) <0.001 3.00 (2.57–3.49) <0.001 3.52 (2.90–4.27) <0.001 3.20 (2.61–3.92) <0.001 3.68 (2.85–4.76) <0.001
  OB 4.34 (3.94–4.78) <0.001 4.76 (4.09–5.54) <0.001 8.09 (7.10–9.22) <0.001 7.26 (5.88–8.96) <0.001 9.67 (8.18–11.43) <0.001 6.59 (4.97–8.75) <0.001
 Family history of hypertension
  No Ref Ref Ref Ref Ref Ref
  Yes 1.25 (1.10–1.42) 0.001 1.02 (0.86–1.22) 0.778 1.46 (1.23–1.72) <0.001 1.31 (1.04–1.66) 0.025 1.60 (1.31–1.97) <0.001 1.55 (1.15–2.09) 0.004
DHTN
 Age group
  6–11 years Ref Ref Ref Ref Ref Ref
  12–17 years 0.85 (0.72–0.99) 0.035 0.73 (0.62–0.85) <0.001 0.99 (0.78–1.27) 0.961 0.85 (0.67–1.09) 0.199 1.29 (0.94–1.77) 0.115 1.26 (0.91–1.74) 0.17
BMI status
  NW Ref Ref Ref Ref Ref Ref
  OWT 1.82 (1.55–2.13) <0.001 2.19 (1.89–2.52) <0.001 2.09 (1.63–2.68) <0.001 2.39 (1.92–2.98) <0.001 2.03 (1.46–2.81) <0.001 2.91 (2.17–3.91) <0.001
  OB 4.55 (4.01–5.17) <0.001 4.82 (4.12–5.63) <0.001 5.27 (4.33–6.41) <0.001 5.46 (4.35–6.85) <0.001 4.82 (3.71–6.26) <0.001 6.78 (5.01–9.17) <0.001
 Family history of hypertension
  No Ref Ref Ref Ref Ref Ref
  Yes 1.11 (0.91–1.35) 0.29 1.38 (1.17–1.64) <0.001 1.26 (0.96–1.66) 0.097 1.70 (1.35–2.15) <0.001 1.46 (1.04–2.06) 0.03 1.96 (1.44–2.65) <0.001
BMI, body mass index; DHTN, diastolic hypertension; ISH, isolated systolic hypertension; NW, normal weight; OB, obesity; OWT, overweight.
aAdjusted for sleep time, physical activity, smoking, drinking, family income per capita, parents’ education level and diet score.

DISCUSSION

To our knowledge, this was the first study that evaluated BP status in school-based children and adolescents by multiple BP screenings in a nationwide multicenter cross-sectional survey in China. It provides comprehensive data of BP status for Chinese urban children. About 4% children and adolescents were defined as hypertensive after three separate BP observations. If those dropped-out at the second and the third visits were assumed to have the same possibilities of hypertension as those followed, the estimated prevalence of hypertension would be 7.8% after two BP visits, and 4.6% after three BP visits in our study.

Although many cross-sectional studies have reported the prevalence of hypertension among Chinese children and adolescents, ranging from 2.2 to 26.4%, most researches were based on BP measurement at only one occasion [10–14]. The Chinese National Surveys on Students Constitution and Health, which is typically based on single BP measurement session, reported that the latest prevalence of HTN defined by the AAP 2017 in 2013 was 16.7% in children aged 6–12 years and 7.9% in children aged 13–17 years [14]. The China Health and Nutrition Survey (CHNS) reported the prevalence of hypertension was 19.2% in 2015 diagnosed by Chinese reference 2017 [26]. Both surveys had substantial higher prevalence of hypertension than our results (4%), which might be mainly explained by the number of BP visits. Another study conducted in 6692 Beijing children by three separate BP screenings reported the prevalence of 3.1% [9]. If those dropped-out were assumed to follow a similar trend as those followed populations in this study, the estimated prevalence of hypertension would be 4.7% [9], which was highly in accordance with our result (4.6%). A school-based cross-sectional study conducted in Houston children aged 10–17 years reported the prevalence of confirmed hypertension of 2.3% by AAP 2017 and 2.7% by the Fourth report, respectively [27]. The corresponding result in our study population aged 10–17 years was 2% by AAP 2017 and 2.5% by the Fourth report, respectively. Our reported prevalence was also higher than another large American population aged 3–18 years followed for two consecutive 36-month periods in which the confirmed diagnosis of arterial hypertension was 1.8% [28], which might be mainly explained by the longer follow-up intervals. In addition, our results were considerably higher than Lo's et al.[29] results (5.4% at the initial visit diagnosed by the Fourth report), which might result from the longer follow-up intervals (3.5 years) and constitution of community-based healthier population of their study.

Recently, a systematic review and meta-analysis reported the summarized prevalence of hypertension among Chinese children was 9.8% [30]. The great discrepancy with our study might be because that they did not specify the number of BP visits and the BP references in the review. Other systematic reviews and meta-analysis at the global level showed that the prevalence of hypertension after three separate visits was about 4% in children aged 3–19 years by Song et al.[31]. and 2.7% in children aged 3–20 years by Sun et al.[32], which were similar with our results.

The level of BP is dynamic and can be easily affected by many factors. BP varies even under standard resting circumstances. Because of the effect of accommodation and regression to the mean, high BP tends to fall on subsequent measurement. In our study, though the prevalence of hypertension reached as high as to 18.4% in boys at the initial visit, it dropped out substantially from visit 2 to visit 3, around 56.8 and 75.7% of these hypertensive ones at the first visit returned back to normal BP at the second visit and the third visit, respectively, suggesting that more than half of these transient-hypertension students would be falsely grouped if only one visit was taken. In addition, though the prevalence of hypertension was high and varied by different BP references at the first visit (16.6% by CN 2010, 17.1% by CN 2017, 10.9% by the fourth report, 15.4% by AAP 2017, respectively), it decreased to 4% by CN 2010 and around 3–5% by the other three BP references. This indicated that the number of BP visits has much higher impact on the prevalence of hypertension in children than the BP references and it is quite essential to classify BP status in children by at least three separate occasions. By increasing the number of BP measurement occasions in abnormal BP observations, the tracking coefficient of BP or the prediction of HTN in adulthood might also rise [33–35].

Though there are few evidences of the impact of ISH, IDH, and SDH during childhood on future cardiovascular events, long-term follow-up studies in young adults indicated that ISH, IDH, and SDH were all positively associated with higher risks of CVD than normal BP, with SDH being the highest, and IDH higher or close to ISH [18,19]. Therefore, categorizing hypertensive children with ISH, IDH, and SDH may improve risk stratification to identify high-risk individuals. In our study, ISH was the most frequent phenotype in boys, which was in accordance with many other studies [11,36–38]. Scientific results in young adults indicated that obesity is associated with increased arterial stiffness, which was directly related to increased SBP [39]. However, our results showed that ISH was still the dominant form of hypertension in normal weight participants. Of note, there were substantial differences in the proportions of hypertension subtypes between boys and girls, especially for children at least 12 years (78.1% of ISH in boys and 51.8% of ISH in girls), which implies that puberty and hormones may have a very important role on blood pressure development [40]. We also explored the proportion of hypertension subtypes by CN 2017, United States Fourth report, and AAP 2017 at the initial visit, and found that the similar trend with CN 2010 except for the United States Fourth report where ISH accounts for obviously higher proportions (80.9% in boys and 64.4% in girls, respectively, Supplemental Figure 1, https://links.lww.com/HJH/B740).

Another point that needed to be state was that 126 participants reported hypertension in the survey, which was rarely mentioned in other studies. Flow chart of BP screenings of these 126 students are provided in the Supplemental Figure 2, https://links.lww.com/HJH/B741. If these 126 participants were defined as hypertensive, the final prevalence of hypertension in our population would increase to 4.3% (1916/44522).

Also, this study has several limitations. Firstly, six centers in our study were not chosen by random sampling method and only urban children and adolescents were recruited in this survey, which might limit the expansion of our results to other cities and students in rural areas. But these cities, which vary substantially in geography, economic development, public resources, and health indicators, could be well representatives of urban children and adolescents in mainland China. Secondly, not all students who were hypertensives at the first or the second visit participated in the subsequent BP measurements in this study, leading to the underestimated prevalence of HTN. If those dropped out at the second and the third visit were considered to have the same possibility of hypertension as those followed up, the prevalence of hypertension would be 4.6% at the third visit. Thirdly, we were unable to detect mask hypertension or white coat hypertension by home blood pressure measurement or ambulatory blood pressure monitoring because of limited resources. According to a previous school-based study conducted in Greek children in which the prevalence of sustained, white-coat, and masked hypertension by two visits was 1.8, 2.1, and 4.2%, respectively [41], the prevalence of white-coat and mask hypertension in our population might be similar. Fourthly, only children whose BP at least 95th percentile were invited to have the subsequent BP measurement, whereas those children with BP at least 90th percentile should be followed-up at another visit to verify an elevated BP as recommended by the guidelines, which would result in underestimated prevalence of hypertension of this survey.

In conclusion, our results showed that around 4% urban Chinese children and adolescents aged 6–17 years were hypertensive after three separate BP screenings in 2012–2015. After evaluation of BP status, comprehensive strategies should be undertaken to these hypertensive children on the following management and interventions rather than simply reporting a rate, which was really needed in further studies.

ACKNOWLEDGEMENTS

We thank the schools, students and research staff from Beijing, Shanghai, Jinan, Changchun, Chongqing and Chengdu who participated in this study.

Funding: This study was supported by the ‘Twelfth Five Year Plan’ of the China National Science and Technology (2012BAI03B03).

List of China Child and Adolescent Cardiovascular Health (CCACH) collaboration members

Jie Mi, MD, PhD, Yinkun Yan, MD, PhD, Department of Noncommunicable Disease Management, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, China; Junting Liu, MS, Hong Cheng, MS, Dongqing Hou, MS, Qin Liu, MS, Guimin Huang, MS, Xiaoyuan Zhao, MS, Xinying Shan, MS, Wenpeng Wang, MS, Meixian Zhang, PhD, Department of Epidemiology, Capital Institute of Pediatrics, Beijing, China; Linghui Meng, PhD, Center of Evidence Based Medicine, Capital Institute of Pediatrics, Beijing, China; Weili Yan, PhD, Fang Liu, PhD, Yi Zhang, MPH, Yi Cheng, MS, Shaoke Chen, MS, Qian Zhao, MS, Fang Cao, MS, Kai Mu, MS, Dayan Niu, MS, Department of Clinical Epidemiology, Children's Hospital of Fudan University, Shanghai, China; Jinghui Sun, MD, Xiaona Wang, MD, Jinghua Wang, MS, Pediatric Cardiovascular Department, The First Hospital of Jilin University, Changchun, Jilin, China; Zhiyong Sun, MD, Xiuhong Sun, BS, Neonatal Department, Jilin Women and Children's Health Hospital, Jilin, Changchun, China; Bo Xi, PhD, Department of Epidemiology, School of Public Health, Shandong University, Jinan, Shandong, China; Min Zhao, PhD, Department of Nutrition and Food Hygiene, School of Public Health, Shandong University, Jinan, Shandong, China; Feng Xiong, MD, Gaohui Zhu, PhD, Department of Endocrinology, Children's Hospital of Chongqing Medical University, Chongqing, China; Lan Zhang, MD, Guidance center of child health care, Chengdu Women's and Children's Center, Chengdu, Sichuan, China; Meng Mao, MD, Department of child health care, West China Second University Hospital, Chengdu, Sichuan, China.

Conflicts of interest

There are no conflicts of interest.

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A list of collaboration members is provided in the Acknowledgements’ section.

Keywords:

adolescents; blood pressure; children; hypertension; hypertension phenotype; three occasions; DHTN; diastolic hypertension; FHTN; family history of hypertension; HTN; hypertension; IDH; isolated diastolic hypertension; ISH; isolated systolic hypertension; OWT; overweight; SDH; systolic and diastolic hypertension

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