Department of Epidemiology &Biostatistics

School of Public Health, Xinjiang Medical University

Ethnic difference in blood pressure in Xinjiang Han, Uygur and Kazak

children and adolescents

Yan WL, Ma Jinfeng, Wang Qian, Dai JH, Yao H, Yang XY, Zheng YJ

Corresponding: Weili Yan 严卫丽 01.weili@gmail.com

Tel&Fax: 0991-4366351

Department of Epidemiology &Biostatistics School of Public Health, XJMU

Ethnicities in Xinjiang

Uygur Kazak

38%

46%

3%

13%

Background

1. The risk of common complex diseases, essential

hypertension, type 2 diabetes and obesity differs

among Uygur and Kazak adult populations. (1)

2. Ethnic difference in fat distribution was observed

between Uygur and Kazak adult populations. (1)

3. Ethnic difference in BMI levels and prevalence of

overweight and obesity in pediatric populations (2)

Fig1. Prevalence of EH among Ethnic Adults

The Chinese Task Force of National Survey of Hypertension. Chin J Hypertens 1995;3 (suppl): 14-18

kazak

Uygur

Han

Ethnic groups

Table 1. Prevalence studies on metabolic diseases in adult populations (2005 ）

Disease Prevalence,%

Uygur Kazak China*

Hypertension1 9.1 50.0 18.6

Diabetes2 4.0 0.1 2.6

Obesity3 8.1 35.4 5.6

* The 4th national survey of nutrition and health , 2002

1. Hypertension: SBP ≥ 140 and/or DBP ≥ 90 or under medication

2. Diabetes: FBS ≥ 7.0 mmol/L

3. Obesity: BMI ≥ 28 kg/m2

Fig 2 ． Age-adjusted prevalence of overweight&obesity in Han, Uygur, Kazak and Hui ethnic children and adolescents aged 7-18 (2004)

0.0

4.0

8.0

12.0

16.0

Pre

vale

nce,

%

obesity overw eight

Male

0.0

2.0

4.0

6.0

8.0

Pre

vale

nce,%

Obesity Overw eight

Female

Han Hui Uighur Kazak

The prevalence of obesity are 4.3%The prevalence of obesity are 4.3% ， ， 3.8%3.8% ，， 2.1%2.1% ，， and 0.2% for boys; and 0.2% for boys; as well as 1.4%as well as 1.4% ， ， 0.8%0.8% ， ， 0.5%0.5% ， ， and 0.15% for girls, defined by IOTF and 0.15% for girls, defined by IOTF cutoffs.cutoffs.

Source of data

1. The routine data (2003) of school-aged children aged 7-18 from New District of Urumqi City organized by the National Educational Ministry Physical Examination Center

2. The cross-sectional study based on a school-based random sample ( recruited stratified by age and gender children aged from 7 to 18 years in Urumqi city in 2005)

Study population of the cross sectional study1. A representative sample of school children

aged form 7 to 18 years were recruited by randomly systematic and clustering sampling by age and gender in Urumqi city and Altai city in 2005.

2. Eleven schools, 115 classes, over 6600 students involved.

3. Including Uygur , Han and Kazak ethnicities.

Data collection

1. A set of questionnaire including demographic data of students and their parents, known risk factors of obesity, such as diet, life style and physical activity etc.

2. Anthropometric measurements Including weight, height, waist and hip

circumference, were recorded with the standard protocol and instruments by professional investigators.

Weight was measured with minimal clothing, and standing height was measured without shoes, with a precision of 0.5 kg and 0.5 cm, respectively, following the national protocol.

Blood pressure measurement

Measured in afternoon time; At least 5 minutes rest before measurement; Manual standard mercury manometers were used

and had been calibrated by the same laboratory before investigation and appropriate size of cuff were used;

Sit position, right arm Measured twice with at least 30 seconds interval; Korotkoff phase I and V sounds were checked as

SBP and DBP respectively; Deflated by around 2 mm Hg each second; All readings were taken to the nearest 2 mm Hg.

Is double measurement of blood pressure safe?-1A pilot study included 401 volunteers aged from 5-69

years

Age group n

5-10 115

11-17 190

18-69 100

Blood pressure were measured strictly by the standard protocol recommended by AHA.

We compared the average SBP and DBP from the first 2 measurements and the whole 3 measurements.

Is double measurement of blood pressure safe?-2

Table 2. Average blood pressure by first 2 and all 3 measurements

Blood pressure

Average of first 2

Average of 3 Sig.

All subjects SBP, mm Hg 108.0±11.2 107.9±10.9 0.9977

DBP, mm Hg 67.89±19.6 67.5±14.6 0.8740

Subjects aged 5-18

SBP, mm Hg 107.7±10.9 107.5±10.7 0.9890

DBP, mm Hg 66.5±9.2 66.4±9.0 0.828

Well trained investigator make it possible to measure blood pressure twice in field work.

Fig3. The prevalence of hypertension in Han and Uygur school-aged populations (2005 data)

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

8 9 10 11 12 13 14 15 16 17 18Age, ys

Pre

vale

nce

, %

Han OB Uygur OB HanHT UygurHTThe Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents

Fig4-a. Height centile curve for American ( 2000 CDC data) and Chinese (2005 cross-sectional data) school-aged boys (LMS smoothed)

Boy

110

115120

125

130

135140

145

150

155160

165

170

175180

185

190

8 9 10 11 12 13 14 15 16 17 18Age, ys

Heig

ht,

cm

5th-US10th-US25th-US50th-US75th-US90th-US95th-US5th-CN10th-CN25th-CN50th-CN75th-CN90th-CN95th-CN

Fig4-b.. Height centile curve for American ( 2000 CDC data) and Chinese (2005 cross-sectional data) school-aged girls (LMS smoothed)

Gi rl

110115

120125

130135

140145150

155160

165170

175180

185190

8 9 10 11 12 13 14 15 16 17 18Age, ys

Heig

ht,c

m

5th-US10th-US25th-US50th-US75th-US90th-US95th-US5th-CN10th-CN25th-CN50th-CN75th-CN90th-CN95th-CN

Fig 5-a. The mean height of Uygur, Han and Kazak children

and adolescents aged 7-18yrs ( Boys)

Femal e

110

130

150

170

190

7 8 9 10 11 12 13 14 15 16 17 18

Age, yrs

Heig

ht,

cm

Ugyr Han Kazak

Femal e

110

130

150

170

190

7 8 9 10 11 12 13 14 15 16 17 18

Age, yrs

Heig

ht,

cm

Ugyr Han Kazak

Fig5-b. The mean height of Uygur, Han and Kazak children and adolescents aged 7-18yrs ( Girls)

Mal e

105

106

107

108

109

110

Uygur Han Kazak

SBP,

mm

Hg

Femal e

102

103

104

105

106

107

Uygur Han Kazak

SBP,

mm

Hg

Fig 6. The mean SBP of Han, Uygur and Kazak children and adolescents adjusted by age and height, mm Hg

P<0.001 P<0.001

Male Female

Fig 7. The mean DBP of Han, Uygur and Kazak children and adolescents adjusted by age and height, mm Hg

Mal e

66

67

68

69

70

Uygur Han Kazak

DBP,

mm

Hg

Femal e

65

66

67

68

69

Uygur Han Kazak

DBP,

mm

Hg

P<0.001P<0.001

Male Female

Fig 8. The age adjusted mean HEIGHT of Han, Uygur and Kazak children and adolescents by age. (cm)

Mal e

149

150

151

152

153

154

Uygur Han Kazak

Heig

ht,

cm

Femal e

146

147

148

149

150

151

Uygur Han KazakHe

ight

, cm

Fig 9. The age adjusted mean BMI of Han, Uygur and Kazak children and adolescents by age. (cm)

Mal e

0

0

0

0

0

1

1

Uygur Han Kazak

Age-

spec

ific

perc

enti

le

Femal e

00

0001

11

Uygur Han KazakAg

e-sp

ecifi

c pe

rcen

tile

of B

MI

Does the difference in height and BMI among ethnicities make the ethnic difference in blood pressure ?

Table 3. The explained variation (EV) of SBP by height in Han, Uygur and Kazak pediatric populations

EV,% Uygur Han Kazak

Full model 9.8 19.6 6.5

BMI_pct 5.8 7.3 3.3

Height, cm 1.7 2.9 1.3

Age, years 0.1 0.2 0.1

• Full model includes BMI, height and age as independent variables.

•EV % were analyzed by adjusted R2 of full model minus that from the reduced model by removing height, BMI or age respectively

• BMI_pct, age-specific percentile

Table 4. The explained variation (EV) of DBP by height in Han, Uygur and Kazak pediatric populations

EV,% Uygur Han Kazak

Full model 2.0 3.1 5.8

BMI_pct 0.05 0.02 2.5

Height, cm 1.7 2.2 1.3

Age, years 0.07 0.0 2.4

• Full model includes BMI, height and age as independent variables.

•EV % were analyzed by adjusted R2 of full model minus that from the reduced model by removing height, BMI or age respectively

• BMI_pct, age-specific percentile

Conclusions-1

1. There is ethnic differences in SBP, DBP,

height and BMI among Uygur, Han and Kazak

school-aged children and adolescents.

2. Height, BMI and age explain greater variation

of SBP in Han but DBP in Kazak population

than that in the other two ethnic pediatric

populations.

3. The rest risk factors out of height, BMI and age, e.g., genetic factors, may contribute more to DBP levels but less to SBP in Kazak children than that in Uygur and Han counterparts.

Conclusions-2

References

1. Yan W, Yang X, Chen S et al. Ethnic Differences in Body Mass Index and Prevalence of Obesity in School Children of Urumqi City, Xinjiang, China. Biomed Environ Sci. 2006 Dec;19(6):469-73 .

2. Yan W, Yang X, Zheng Y, Ge D, Zhang Y, Shan Z, Simu H, Sukerobai M, Wang R. The metabolic syndrome in Uygur and Kazak population. Diabetes Care. 2005 ， 28 （ 10 ）： 2554-5.

Other published papers based on the same study sample3. Yan W, Yao H, Dai J, Chen Y, Cui J, Wang X. Waist

circumference cutoff points for Chinese children and adolescents.

Obesity. 2008;16(5):1687-1692

4. Yan W, He B, Wang X, et al. Waist-to-Height Ratio Is an Accurate

and Easier Index for Evaluating Obesity in Children and

Adolescents. Obesity (Silver Spring). 2007 Mar;15(3):748-52.

5. Yan W, Wang X, Yao H et al. Waist-to-height Ratio and BMI

Predict Different Cardiovascular Risk Factors in Chinese Children.

Diabetes Care. 2006; 29(12):2760-1.

6. Yan W, Gu D, Yang X, Wu J, Kang L, Zhang L. High-density

lipoprotein cholesterol levels increase with age, body mass index,

blood pressure and fasting blood glucose in a rural Uygur

population in China. J Hypertens. 2005;23 (11):1985-1989.

Thank you !