International Journal of Cardiology 179 (2015) 536–538

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Letter to the Editor

Prevalence of relatively high blood pressure among children and adolescents with different body mass index and subcutaneous fat cut-offs Ying-xiu Zhang ⁎, Mei Wang, Zun-hua Chu, Li Xie Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, Shandong, China

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Article history: Received 21 October 2014 Accepted 25 October 2014 Available online 28 October 2014 Keywords: Blood pressure Body mass index Skinfold thickness Adolescent

At a global perspective, hypertension in adults is a serious public health problem faced today, since it is the main risk factor for cardiovascular disease (CVD), accounting for nearly 45% of global CVD morbidity and mortality [1,2]. Interestingly, some studies have provided ample evidence that hypertension in adults has its onset in childhood; children with elevated blood pressure (BP) are more likely to become hypertensive adults [3–6]. Therefore, early detection and intervention in children with elevated BP is an important action for the control and prevention of hypertension in adulthood. Although the positive relationship between BP levels and body mass index (BMI) has been well recognized, however, little is known about the linkage of BP with skinfold thickness (SFT) within each BMI category (underweight, normal weight, overweight and obesity). In this study, we reported the prevalence of relatively high BP among children and adolescents categorized by BMI and SFT in a large sample in Shandong, China. Data for this study were obtained from a large cross-sectional survey of schoolchildren. A total of 38,802 students (19,446 boys and 19,356 girls) from 16 districts in Shandong Province, students of Han nationality, aged 7–17 years, participated in the National Surveys on Chinese Students' Constitution and Health, which were carried out in September to October 2010. The sampling method was stratified multi-stage sampling based on selected primary and secondary schools. Six public ⁎ Corresponding author at: Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, 16992 Jingshi Road, Jinan 250014, Shandong, China. E-mail address: [email protected] (Y. Zhang).

http://dx.doi.org/10.1016/j.ijcard.2014.10.163 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.

schools (two primary schools, two junior high schools and two senior high schools) from each of the 16 districts in Shandong were randomly selected and invited to participate in the study. From the selected schools, two classes in each grade were selected, and all students of the selected classes were invited to join the study. All measurements were performed by well-trained health professionals in each of the 16 districts using the same type of apparatus and followed the same procedures. Height without shoes was measured using metal column height-measuring stands to the nearest 0.1 cm. Weight was measured using lever scales to the nearest 0.1 kg while the subjects wore their underwear only. BMI was calculated from their height and weight (kg/m2). SFT was measured on the right side of the body using Skinfold Caliper (Jianmin, GMCS-PZQ; Beijing Xindong Huateng Sports Instruments Company, Limited) to the nearest 0.5 mm, at the two sites: (i) triceps, halfway between the acromion process and the olecranon process; (ii) subscapular, 1.0 cm below the tip of the scapula, at an angle of 45° to the lateral side of the body. In each participant, three measurements were taken and the middle value was recorded for one skinfold site. The sum of triceps and subscapular skinfold thickness (SSFT) was analyzed. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using a mercury sphygmomanometer after each subject had rested for at least 15 min in a sitting position. BP was measured twice on the right arm with an appropriately sized cuff and the average value was recorded on the study form. DBP was defined via Korotkoff Sound 5. Based on the national data, BP reference standards for Chinese children and adolescents have been established in 2010 [7], and the reference values of SBP and DBP percentiles for Chinese children and adolescents were applied in this study. Relatively high BP status was defined as SBP and/or DBP ≥ 95th percentile for age and gender. The BMI cutoff points recommended by the International Obesity Task Force (IOTF) were used to define overweight and obesity [8]; underweight was also defined by the international cut-offs [9]. All subjects were classified into four groups (underweight, normal weight, overweight and obesity). The age- and sex-specific quartiles of SSFT for children and adolescents in each group were calculated, and each group was reclassified into four subgroups (Q1–Q4). Figs. 1 and 2 show the prevalence of relatively high BP within each BMI + SFT category in boys and girls. Within underweight category, no statistical significant differences in the prevalence of relatively high BP were observed among the four subgroups (SFT Q1–Q4) (x2boys = 0.14, P N 0.05; x2girls = 0.09, P N 0.05). Instead, within normal weight, overweight and obesity categories, statistical significant differences in the

Y. Zhang et al. / International Journal of Cardiology 179 (2015) 536–538

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70 60.7 60

54.4 49.3

50

50.4 47.2

42.7 40

36.6

%

33.8 30

25.3 19.4

20

10

15.3 8.9

9.3

8.8

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Q3

10.2

12.5

0 Q1

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Under weight

Q1

Q2

Q3

Q4

Normal weight

Q1

Q2

Q3

Q4

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Over weight

Q2

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Obesity

Fig. 1. The prevalence of relatively high BP within each BMI + SFT category in boys. Q1, SFT b 25th. Q2, 25th ≤ SFT b 50th. Q3, 50th ≤ SFT b 75th. Q4, SFT ≥ 75th.

70 58.2

60 49.1

50 42.1 40

39.8

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35.7 29.5 26.8

30 22.0 20

10

16.5 8.9

9.2

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Q4

11.3

12.7

0 Under weight

Q1

Q2

Q3

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Normal weight

Q1

Q2

Q3

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Over weight

Q1

Q2

Q3

Q4

Obesity

Fig. 2. The prevalence of relatively high BP within each BMI + SFT category in girls. Q1, SFT b 25th. Q2, 25th ≤ SFT b 50th. Q3, 50th ≤ SFT b 75th. Q4, SFT ≥ 75th.

prevalence of relatively high BP were observed among the four subgroups (SFT Q1–Q4) (for boys, x2 = 227.56, 47.36 and 13.24, P b 0.01; for girls, x2 = 209.27, 33.47 and 8.75, P b 0.01 or 0.05). Overweight with SFT = Q4 subgroup had slightly higher and similar prevalence to obesity with SFT = Q1 and SFT = Q2 subgroups (49.3 vs. 47.2 and 50.4% for boys, 42.1 vs. 39.8 and 42.1% for girls). The highest prevalence of relatively high BP was noted in obesity with SFT = Q4 subgroup (60.7% for boys and 58.2% for girls). Based on both BMI and SFT categories, the prevalence of relatively high BP among children and adolescents with different body mass index and subcutaneous fat cut-offs were examined for the first time in Shandong, China. Children and adolescents with high BMI and high SFT might have an increased risk of elevated BP. Our results suggest that the additional measurement of SFT is better than BMI alone to help identify high BP risks. One limitation is noted. The BP reading was recorded as the average of two measurements on one occasion only; thus, the possibility that errors may have occurred in classifying adolescents as having high BP or normal BP cannot be ruled out. However, the purpose of using BP categories in the analysis was to obtain a general idea of the extent of

elevated BP in the studied adolescents rather than to diagnose the presence of hypertension among them. Thus, in this paper, we use the term ‘relatively high BP’ rather than ‘high BP’. Conflicts of interest There are no conflicts of interest on behalf of any of the authors. Acknowledgments Surveys on students' constitution and health are conducted under the auspices of the Department of Education in Shandong Province, China. We thank all the team members and all participants. Special thanks to Mr. B Yu for providing access to the survey data. References [1] A. Chockalingam, N.P. Campbell, J.G. Fodor, Worldwide epidemic of hypertension, Can. J. Cardiol. 22 (2006) 553–555.

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[2] M. Ezzati, S. Vander Hoorn, C.M. Lawes, R. Leach, W.P. James, A.D. Lopez, A. Rodgers, C.J. Murray, Rethinking the “diseases of affluence” paradigm: global patterns of nutritional risks in relation to economic development, PLoS Med. 2 (2005) 404–412. [3] W. Bao, S.A. Threefoot, S.R. Srinivasan, G.S. Berenson, Essential hypertension predicted by tracking of elevated blood pressure from childhood to adulthood: the Bogalusa Heart Study, Am. J. Hypertens. 8 (1995) 657–665. [4] L.E. Vos, A. Oren, M.L. Bots, W.H. Gorissen, D.E. Grobbee, C.S. Uiterwaal, Does a routinely measured blood pressure in young adolescence accurately predict hypertension and total cardiovascular risk in young adulthood? J. Hypertens. 21 (2003) 2027–2034. [5] S.S. Sun, G.D. Grave, R.M. Siervogel, A.A. Pickoff, S.S. Arslanian, S.R. Daniels, Systolic blood pressure in childhood predicts hypertension and metabolic syndrome later in life, Pediatrics 119 (2007) 237–246.

[6] X. Chen, Y. Wang, Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis, Circulation 117 (2008) 3171–3180. [7] J. Mi, T.Y. Wang, L.H. Meng, G.J. Zhu, S.M. Han, Y. Zhong, G.M. Liu, Y.P. Wan, F. Xiong, J.P. Shi, W.L. Yan, P.M. Zhou, Development of blood pressure reference standards for Chinese children and adolescents, Chin. J. Evid. Based Pediatr. 15 (2010) 4–14 (in Chinese). [8] T.J. Cole, M.C. Bellizzi, K.M. Flegal, W.H. Dietz, Establishing a standard definition for child overweight and obesity worldwide: international study, BMJ 320 (2000) 1240–1243. [9] T.J. Cole, K.M. Flegal, D. Nicholls, A.A. Jackson, Body mass index cut offs to define thinness in children and adolescents: international survey, BMJ 335 (2007) 194–197.

Prevalence of relatively high blood pressure among children and adolescents with different body mass index and subcutaneous fat cut-offs.

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