International Journal of Cardiology 176 (2014) 1053–1055
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
Urban–rural and regional disparities in the prevalence of elevated blood pressure among children and adolescents in Shandong, China Ying-xiu Zhang ⁎, Jing-yang Zhou, Jin-shan Zhao, Zun-hua Chu Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, Shandong, China
a r t i c l e
i n f o
Article history: Received 30 May 2014 Accepted 26 July 2014 Available online 2 August 2014 Keywords: Elevated blood pressure Disparities Prevalence Socioeconomic status Child and adolescent
The worldwide prevalence of hypertension in adults has become a major public health problem [1]. Several 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 [2–5]. In this study, based on provincial data in 2010, we report the urban–rural and regional disparities in the prevalence of elevated BP among children and adolescents in Shandong, China. Data for this study were obtained from a large cross-sectional survey of schoolchildren. A total of 38,781 students (19,464 boys and 19,317 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. All subjects voluntarily joined this study with informed consent. The sampling method was stratified multistage sampling based on selected primary and secondary schools, and has been described in detail elsewhere [6]. All subjects were stratified by gender, age and the area of residence (urban or rural). The information about gross domestic product (GDP) per capita of the 16 districts in 2010 was collected from Shandong Statistical Yearbook [7]. The 16 districts were divided into three groups [high socioeconomic status (SES), moderate SES and low SES] according to their GDP per capita in 2010. High SES was defined as GDP per capita above 8000 dollars (including Jinan, Qingdao, Yantai, Weihai, Dongying and Zibo), moderate SES was defined as GDP per capita above 5000 but ⁎ Corresponding author at: Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, 16992 Jingshi Road, Jinan, Shandong 250014, China. Tel./fax: +86 531 82679413. E-mail address: [email protected] (Y. Zhang).
http://dx.doi.org/10.1016/j.ijcard.2014.07.155 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
below 8000 dollars (including Weifang, Taian, Laiwu, Binzhou and Rizhao), and low SES was defined as GDP per capita below 5000 dollars (including Jining, Dezhou, Liaocheng, Linyi and Heze). To show the district distribution of elevated BP prevalence, all subpopulations were re-divided into six regions: a) high SES urban areas; b) moderate SES urban areas; c) low SES urban areas; d) high SES rural areas; e) moderate SES rural areas; and f) low SES rural areas. All measurements were conducted by a team of trained technicians in each of the 16 districts. 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 [8], 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 prevalence of relatively high BP among children and adolescents by age, gender, and urban/rural categories in the sample is shown in Table 1. The overall prevalence of relatively high BP among children and adolescents aged 7–17 years was 30.99% (urban boys), 25.37% (rural boys), 24.69% (urban girls) and 20.27% (rural girls); statistically significant gender and urban–rural differences were observed (P b 0.05). For both boys and girls, adolescents (aged 13–17 years) had higher prevalence of relatively high BP than children (aged 7–12 years) (P b 0.05). The prevalence of relatively high BP among children and adolescents by age and regional SES is shown in Table 2. An increasing trend was observed from the low SES group to the moderate and high SES groups. The overall prevalence of relatively high BP in the three SES groups was 24.68%, 27.36% and 31.18% in boys and 19.09%, 22.12% and 25.15% in girls, respectively. For both boys and girls, statistical significant differences were observed between any two groups (P b 0.05). The prevalence of relatively high BP among children and adolescents by regional SES and urban/rural categories is shown in Table 3. The prevalence of relatively high BP in high SES urban areas was 33.88% in boys and 26.97% in girls and thereby much higher compared to that of the other groups. For both boys and girls, the highest prevalence and the lowest prevalence of relatively high BP were observed in high SES urban areas and low SES rural areas (21.88% in boys and 16.83% in girls), respectively.
1054
Y. Zhang et al. / International Journal of Cardiology 176 (2014) 1053–1055
Table 1 Prevalence of relatively high BP among children and adolescents aged 7–17 years in urban and rural areas in Shandong, China. Gender
Boys
Girls
Age/years
7–17 7–12 13–17 7–17 7–12 13–17
Total
Urban
Rural
n
RHBP (95%CI)
n
RHBP (95%CI)
n
RHBP (95%CI)
19,464 10,769 8695 19,317 10,692 8625
28.21 (27.58–28.84) 24.17 (23.36–24.98) 33.20 (32.21–34.19) 22.50 (21.91–23.09) 20.91 (20.14–21.68) 24.48 (23.57–25.39)
9824 5440 4384 9762 5389 4373
30.99 (30.08–31.90) 27.54 (26.35–28.73) 35.26 (33.85–36.67) 24.69 (23.83–25.55) 23.86 (22.72–25.00) 25.70 (24.40–27.00)
9640 5329 4311 9555 5303 4252
25.37 (24.50–26.24) 20.74 (19.65–21.83) 31.11 (29.73–32.49) 20.27 (19.46–21.08) 17.91 (16.88–18.94) 23.21 (21.94–24.48)
x2
P
75.67 67.94 16.95 53.98 57.19 7.23
0.0000 0.0000 0.0000 0.0000 0.0000 0.0072
x2
P
73.57 25.24 48.12 71.81 39.30 31.86
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
RHBP, relatively high BP. Data presented as percentage.
Table 2 Prevalence of relatively high BP among children and adolescents aged 7–17 years in different SES districts in Shandong, China. Gender
Boys
Girls
Age/years
7–17 7–12 13–17 7–17 7–12 13–17
High SES
Moderate SES
Low SES
n
RHBP (95%CI)
n
RHBP (95%CI)
n
RHBP (95%CI)
8325 4546 3779 8195 4519 3676
31.18 (30.18–32.18) 26.42 (25.14–27.70) 36.91 (35.37–38.45) 25.15 (24.21–26.09) 23.50 (22.26–24.74) 27.18 (25.74–28.62)
5413 3019 2394 5365 2934 2431
27.36 (26.17–28.55) 23.58 (22.07–25.09) 32.12 (30.25–33.99) 22.12 (21.01–23.23) 20.52 (19.06–21.98) 24.06 (22.36–25.76)
5726 3204 2522 5757 3239 2518
24.68 (23.56–25.80) 21.54 (20.12–22.96) 28.67 (26.91–30.43) 19.09 (18.07–20.11) 17.66 (16.35–18.97) 20.93 (19.34–22.52)
SES, socioeconomic status. RHBP, relatively high BP. Data presented as percentage.
Table 3 Prevalence of relatively high BP among children and adolescents aged 7–17 years in different populations. Populations
a. High SES urban areas b. Moderate SES urban areas c. High SES rural areas d. Low SES urban areas e. Moderate SES rural areas f. Low SES rural areas Chi-square P value
Boys
Girls
n
RHBP (95%CI)
n
RHBP (95%CI)
4265 2703 4060 2856 2710 2870 147.42 0.0000
33.88 (32.46–35.30) 30.11 (28.38–31.84) 28.35 (26.96–29.74) 27.49 (25.85–29.13) 24.61 (22.99–26.23) 21.88 (20.37–23.39)
4182 2705 4013 2875 2660 2882 125.67 0.0000
26.97 (25.62–28.32) 24.70 (23.07–26.33) 23.25 (21.94–24.56) 21.36 (19.86–22.86) 19.51 (18.00–21.02) 16.83 (15.46–18.20)
SES, socioeconomic status. RHBP, relatively high BP. Data presented as percentage.
Shandong is a populous province with highly unbalanced regional development in China. This is the first study examining the urban– rural and regional disparities in elevated BP among children and adolescents in this province. We found that substantial urban–rural and regional disparities exist in child and adolescent elevated BP. The prevalence of relatively high BP varied from 33.88% (high SES urban boys) to 16.83% (low SES rural girls) in different areas of Shandong. The higher prevalence of relatively high BP may relate to the physical characteristics and dietary customs of Shandongese: First, within China, children and adolescents in Shandong had higher BMI and BP levels. Second, high dietary intake of salt has been identified as an important risk factor for hypertension. A survey carried out in 2011 showed that per capita daily intake of salt was 12.5 g in the Shandong population, which is 2-times greater than the recommended nutrient intake [9]. This study has several limitations. First, 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’. Second, this study is a macro-analysis based on the regional SES, lacking individual SES information probably underestimated the true effects of SES on
elevated BP. Third, the absence of detailed information concerning living environments, nutritional status, dietary pattern, and physical activity at the individual level also limited our study. Conflict 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 are due to Mr. B Yu for providing access to the survey data. References [1] Chockalingam A, Campbell NP, Fodor JG. Worldwide epidemic of hypertension. Can J Cardiol 2006;22:553–5. [2] Bao W, Threefoot SA, Srinivasan SR, Berenson GS. Essential hypertension predicted by tracking of elevated blood pressure from childhood to adulthood: the Bogalusa Heart Study. Am J Hypertens 1995;8:657–65. [3] Vos LE, Oren A, Bots ML, Gorissen WH, Grobbee DE, Uiterwaal CS. Does a routinely measured blood pressure in young adolescence accurately predict hypertension and total cardiovascular risk in young adulthood? J Hypertens 2003;21:2027–34. [4] Chen X, Wang Y. Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis. Circulation 2008;117:3171–80.
Y. Zhang et al. / International Journal of Cardiology 176 (2014) 1053–1055 [5] Klumbiene J, Sileikiene L, Milasauskiene Z, Zaborskis A, Shatchkute A. The relationship of childhood to adult blood pressure: longitudinal study of juvenile hypertension in Lithuania. J Hypertens 2000;18:531–8. [6] Zhang YX, Wang SR. Differences in development and the prevalence of obesity among children and adolescents in different socioeconomic status districts in Shandong, China. Ann Hum Biol 2012;39:290–6. [7] Shandong Provincial Bureau of Statistics. Shandong Statistical Yearbook. Beijing: China Statistical Publishing House; 2011 45 [in Chinese].
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[8] Mi J, Wang TY, Meng LH, et al. Development of blood pressure reference standards for Chinese children and adolescents. Chin J Evid Based Pediatr 2010;15:4–14 [in Chinese]. [9] Bi ZQ, Wang LH, Zong L, Xu AQ. Salt intake hypertension prevalence and economic burden of Shandong population. Jinan: Shandong Science and Technology Press; 2013 21–30 [in Chinese].
Contents lists available at ScienceDirect
International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Letter to the Editor
Urban–rural and regional disparities in the prevalence of elevated blood pressure among children and adolescents in Shandong, China Ying-xiu Zhang ⁎, Jing-yang Zhou, Jin-shan Zhao, Zun-hua Chu Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, Shandong, China
a r t i c l e
i n f o
Article history: Received 30 May 2014 Accepted 26 July 2014 Available online 2 August 2014 Keywords: Elevated blood pressure Disparities Prevalence Socioeconomic status Child and adolescent
The worldwide prevalence of hypertension in adults has become a major public health problem [1]. Several 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 [2–5]. In this study, based on provincial data in 2010, we report the urban–rural and regional disparities in the prevalence of elevated BP among children and adolescents in Shandong, China. Data for this study were obtained from a large cross-sectional survey of schoolchildren. A total of 38,781 students (19,464 boys and 19,317 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. All subjects voluntarily joined this study with informed consent. The sampling method was stratified multistage sampling based on selected primary and secondary schools, and has been described in detail elsewhere [6]. All subjects were stratified by gender, age and the area of residence (urban or rural). The information about gross domestic product (GDP) per capita of the 16 districts in 2010 was collected from Shandong Statistical Yearbook [7]. The 16 districts were divided into three groups [high socioeconomic status (SES), moderate SES and low SES] according to their GDP per capita in 2010. High SES was defined as GDP per capita above 8000 dollars (including Jinan, Qingdao, Yantai, Weihai, Dongying and Zibo), moderate SES was defined as GDP per capita above 5000 but ⁎ Corresponding author at: Shandong Center for Disease Control and Prevention, Shandong University Institute of Preventive Medicine, 16992 Jingshi Road, Jinan, Shandong 250014, China. Tel./fax: +86 531 82679413. E-mail address: [email protected] (Y. Zhang).
http://dx.doi.org/10.1016/j.ijcard.2014.07.155 0167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved.
below 8000 dollars (including Weifang, Taian, Laiwu, Binzhou and Rizhao), and low SES was defined as GDP per capita below 5000 dollars (including Jining, Dezhou, Liaocheng, Linyi and Heze). To show the district distribution of elevated BP prevalence, all subpopulations were re-divided into six regions: a) high SES urban areas; b) moderate SES urban areas; c) low SES urban areas; d) high SES rural areas; e) moderate SES rural areas; and f) low SES rural areas. All measurements were conducted by a team of trained technicians in each of the 16 districts. 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 [8], 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 prevalence of relatively high BP among children and adolescents by age, gender, and urban/rural categories in the sample is shown in Table 1. The overall prevalence of relatively high BP among children and adolescents aged 7–17 years was 30.99% (urban boys), 25.37% (rural boys), 24.69% (urban girls) and 20.27% (rural girls); statistically significant gender and urban–rural differences were observed (P b 0.05). For both boys and girls, adolescents (aged 13–17 years) had higher prevalence of relatively high BP than children (aged 7–12 years) (P b 0.05). The prevalence of relatively high BP among children and adolescents by age and regional SES is shown in Table 2. An increasing trend was observed from the low SES group to the moderate and high SES groups. The overall prevalence of relatively high BP in the three SES groups was 24.68%, 27.36% and 31.18% in boys and 19.09%, 22.12% and 25.15% in girls, respectively. For both boys and girls, statistical significant differences were observed between any two groups (P b 0.05). The prevalence of relatively high BP among children and adolescents by regional SES and urban/rural categories is shown in Table 3. The prevalence of relatively high BP in high SES urban areas was 33.88% in boys and 26.97% in girls and thereby much higher compared to that of the other groups. For both boys and girls, the highest prevalence and the lowest prevalence of relatively high BP were observed in high SES urban areas and low SES rural areas (21.88% in boys and 16.83% in girls), respectively.
1054
Y. Zhang et al. / International Journal of Cardiology 176 (2014) 1053–1055
Table 1 Prevalence of relatively high BP among children and adolescents aged 7–17 years in urban and rural areas in Shandong, China. Gender
Boys
Girls
Age/years
7–17 7–12 13–17 7–17 7–12 13–17
Total
Urban
Rural
n
RHBP (95%CI)
n
RHBP (95%CI)
n
RHBP (95%CI)
19,464 10,769 8695 19,317 10,692 8625
28.21 (27.58–28.84) 24.17 (23.36–24.98) 33.20 (32.21–34.19) 22.50 (21.91–23.09) 20.91 (20.14–21.68) 24.48 (23.57–25.39)
9824 5440 4384 9762 5389 4373
30.99 (30.08–31.90) 27.54 (26.35–28.73) 35.26 (33.85–36.67) 24.69 (23.83–25.55) 23.86 (22.72–25.00) 25.70 (24.40–27.00)
9640 5329 4311 9555 5303 4252
25.37 (24.50–26.24) 20.74 (19.65–21.83) 31.11 (29.73–32.49) 20.27 (19.46–21.08) 17.91 (16.88–18.94) 23.21 (21.94–24.48)
x2
P
75.67 67.94 16.95 53.98 57.19 7.23
0.0000 0.0000 0.0000 0.0000 0.0000 0.0072
x2
P
73.57 25.24 48.12 71.81 39.30 31.86
0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
RHBP, relatively high BP. Data presented as percentage.
Table 2 Prevalence of relatively high BP among children and adolescents aged 7–17 years in different SES districts in Shandong, China. Gender
Boys
Girls
Age/years
7–17 7–12 13–17 7–17 7–12 13–17
High SES
Moderate SES
Low SES
n
RHBP (95%CI)
n
RHBP (95%CI)
n
RHBP (95%CI)
8325 4546 3779 8195 4519 3676
31.18 (30.18–32.18) 26.42 (25.14–27.70) 36.91 (35.37–38.45) 25.15 (24.21–26.09) 23.50 (22.26–24.74) 27.18 (25.74–28.62)
5413 3019 2394 5365 2934 2431
27.36 (26.17–28.55) 23.58 (22.07–25.09) 32.12 (30.25–33.99) 22.12 (21.01–23.23) 20.52 (19.06–21.98) 24.06 (22.36–25.76)
5726 3204 2522 5757 3239 2518
24.68 (23.56–25.80) 21.54 (20.12–22.96) 28.67 (26.91–30.43) 19.09 (18.07–20.11) 17.66 (16.35–18.97) 20.93 (19.34–22.52)
SES, socioeconomic status. RHBP, relatively high BP. Data presented as percentage.
Table 3 Prevalence of relatively high BP among children and adolescents aged 7–17 years in different populations. Populations
a. High SES urban areas b. Moderate SES urban areas c. High SES rural areas d. Low SES urban areas e. Moderate SES rural areas f. Low SES rural areas Chi-square P value
Boys
Girls
n
RHBP (95%CI)
n
RHBP (95%CI)
4265 2703 4060 2856 2710 2870 147.42 0.0000
33.88 (32.46–35.30) 30.11 (28.38–31.84) 28.35 (26.96–29.74) 27.49 (25.85–29.13) 24.61 (22.99–26.23) 21.88 (20.37–23.39)
4182 2705 4013 2875 2660 2882 125.67 0.0000
26.97 (25.62–28.32) 24.70 (23.07–26.33) 23.25 (21.94–24.56) 21.36 (19.86–22.86) 19.51 (18.00–21.02) 16.83 (15.46–18.20)
SES, socioeconomic status. RHBP, relatively high BP. Data presented as percentage.
Shandong is a populous province with highly unbalanced regional development in China. This is the first study examining the urban– rural and regional disparities in elevated BP among children and adolescents in this province. We found that substantial urban–rural and regional disparities exist in child and adolescent elevated BP. The prevalence of relatively high BP varied from 33.88% (high SES urban boys) to 16.83% (low SES rural girls) in different areas of Shandong. The higher prevalence of relatively high BP may relate to the physical characteristics and dietary customs of Shandongese: First, within China, children and adolescents in Shandong had higher BMI and BP levels. Second, high dietary intake of salt has been identified as an important risk factor for hypertension. A survey carried out in 2011 showed that per capita daily intake of salt was 12.5 g in the Shandong population, which is 2-times greater than the recommended nutrient intake [9]. This study has several limitations. First, 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’. Second, this study is a macro-analysis based on the regional SES, lacking individual SES information probably underestimated the true effects of SES on
elevated BP. Third, the absence of detailed information concerning living environments, nutritional status, dietary pattern, and physical activity at the individual level also limited our study. Conflict 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 are due to Mr. B Yu for providing access to the survey data. References [1] Chockalingam A, Campbell NP, Fodor JG. Worldwide epidemic of hypertension. Can J Cardiol 2006;22:553–5. [2] Bao W, Threefoot SA, Srinivasan SR, Berenson GS. Essential hypertension predicted by tracking of elevated blood pressure from childhood to adulthood: the Bogalusa Heart Study. Am J Hypertens 1995;8:657–65. [3] Vos LE, Oren A, Bots ML, Gorissen WH, Grobbee DE, Uiterwaal CS. Does a routinely measured blood pressure in young adolescence accurately predict hypertension and total cardiovascular risk in young adulthood? J Hypertens 2003;21:2027–34. [4] Chen X, Wang Y. Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis. Circulation 2008;117:3171–80.
Y. Zhang et al. / International Journal of Cardiology 176 (2014) 1053–1055 [5] Klumbiene J, Sileikiene L, Milasauskiene Z, Zaborskis A, Shatchkute A. The relationship of childhood to adult blood pressure: longitudinal study of juvenile hypertension in Lithuania. J Hypertens 2000;18:531–8. [6] Zhang YX, Wang SR. Differences in development and the prevalence of obesity among children and adolescents in different socioeconomic status districts in Shandong, China. Ann Hum Biol 2012;39:290–6. [7] Shandong Provincial Bureau of Statistics. Shandong Statistical Yearbook. Beijing: China Statistical Publishing House; 2011 45 [in Chinese].
1055
[8] Mi J, Wang TY, Meng LH, et al. Development of blood pressure reference standards for Chinese children and adolescents. Chin J Evid Based Pediatr 2010;15:4–14 [in Chinese]. [9] Bi ZQ, Wang LH, Zong L, Xu AQ. Salt intake hypertension prevalence and economic burden of Shandong population. Jinan: Shandong Science and Technology Press; 2013 21–30 [in Chinese].
