OBJECTIVETo analyze the association between abdominal obesity and blood pressure among 7-10 years old Chinese children.

METHODSA total of 40 495 children aged 7-10 years with complete height, weight, waist circumference and blood pressure data were chosen from the data of 2010 Chinese National Survey on Students Constitution and Health. Based on the "Reference Norms for Screening Overweight and Obesity in Chinese Children and Adolescents" developed by Working Group Obesity in China (WGOC) and the waist to height ratio reference value for children (WHtR ≤ 0.46) , the children were divided into 4 body types (normal weight, simple abdominal obesity, combined obesity and other types). High blood pressure was defined as the systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) higher than the P 95 blood pressure value of 2010 national student of the same gender and age. The prevalence of simple abdominal obesity, combined obesity and high blood pressure were described. Three groups (with 2165 children in each) of children with normal weight, simple abdominal obesity, combined obesity respectively were selected from the chosen ones matched by gender, age (within ± 0.5 years old) and height (within ± 0.3 cm) at the ratio of 1: 1: 1. The value of blood pressure and prevalence of high blood pressure were described.χ(2) test, analysis of variance and multilevel models were used to analyze the relationship between obesity and blood pressure.

RESULTSA total of 40 475 children were selected from the database, including 20 175 boys and 20 320 girls. The prevalence of simple abdominal obesity was 6.36% (2576/40 495), the prevalence of boys and girls was 7.41% (1494/20 175) and 5.32% (1082/20 320) respectively. The prevalence of combined obesity was 16.33% (6611/40 495), the prevalence of boys and girls was 21.30% (4298/20 175) and 11.38% (2313/20 320) respectively. There were statistical differences in the body type distribution of both boys and girls (χ(2) = 869.01, P < 0.01). The prevalence of high blood pressure was 9.62% (3896/40 495), the prevalence of boys (10.05% (2028/20 175)) was higher than girls (9.19% (1868/20 320)) (χ(2) = 8.59, P < 0.01). The value of SBP and DBP among combined obesity group (boys: (103.8 ± 11.3), (64.7 ± 10.1) mm Hg (1 mm Hg = 0.133 kPa); girls: (102.9 ± 12.1), (64.5 ± 10.0) mm Hg) > simple abdominal obesity group (boys: (99.5 ± 11.2), (61.6 ± 9.9) mm Hg; girls: (99.6 ± 11.4), (62.6 ± 9.3) mm Hg)> normal weight group (boys: (97.4 ± 10.8), (60.5 ± 9.4) mm Hg; girls: (97.2 ± 10.8), (60.8 ± 9.4) mm Hg), and the differences were statistical significant (Fboys: 113.22, 62.05; Fgirls: 54.19, 32.31, P < 0.01). According to the results of multilevel model, among boys, compared with the normal weight group, the SBP of combined obesity group and simple abdominal obesity group was 6.0 and 1.8 mm Hg higher respectively (Wald χ(2): 17.55, 204.94, P < 0.01); the DBP was 4.0 and 0.9 mm Hg higher respectively (Wald χ(2): 6.37, 114.05, P < 0.05). Among girls, the SBP was 5.0 and 2.1 mm Hg higher respectively (Wald χ(2):16.47, 92.52, P < 0.01); the DBP was 3.5 and 1.6 mm Hg higher respectively (Wald χ(2): 12.29, 57.52, P < 0.01). Comparing with normal group, the risk of high SBP among boys with simple abdominal obesity was higher (OR = 1.48; 95%CI: 1.06-2.06), and both the boys (SBP: OR = 3.06; 95%CI: 2.28-4.11) ; DBP: OR = 2.72; 95%CI: 1.99-3.72) and girls (SBP: OR = 2.48; 95%CI: 1.75-3.53; DBP: OR = 2.64; 95%CI: 1.82-3.93) in combined obesity group had a higher risk of high SBP and high DBP.

CONCLUSIONSimple abdominal obesity is associated with the increasing of blood pressure in children, and combined obesity has a closer ties than simple abdominal obesity.