OBJECTIVETo study the dietary habits of school-age children in urban and rural districts and their association with blood pressure levels in Beijing, China.

METHODSA stratified, randomly clustered sampling design was used, 29 primary and secondary schools from four urban districts and three rural districts in Beijing were randomly selected in 2004. 20 638 children aged 6-18 years old were surveyed, and 19 072 of them provided completed usable data. The weight, height and blood pressure of the subjects were measured according to standard method.10 food-groups' information was collected by a semi-quantitative food frequency questionnaire. The relationship between different dietary habits and the blood pressure levels in school children was analyzed by multiple linear regression model.

RESULTSThe prevalence of obesity among children in urban area (12.2%, 1 218/9 984) was higher than that in rural area (6.7%, 609/9 088) (χ(2) = 4.62, P < 0.05) , whereas the prevalence of hypertension among children in urban area (8.0%, 799/9 984) was lower than that in rural area (8.9%, 809/9 088) (χ(2) = 167.32, P < 0.05) . The diastolic blood pressure (DBP) among children was (65.7 ± 8.6) mmHg (1 mmHg = 0.133 kPa) in urban area and (67.0 ± 8.7) mmHg in rural area, respectively (F = 86.44, P < 0.05) , and the systolic blood pressure (SBP) among children was (103.4 ± 12.2) mmHg in urban area and (104.3 ± 11.6) mmHg in rural area, respectively (F = 11.33, P < 0.05) . Factor analysis revealed 4 dietary habits labeled prudent habit, protein habit, high-fat and high-calorie habit and vegetables and fruits habit. The 4 dietary habits' variance contribution rate respectively was 24.7%, 14.6%, 14.0%, 8.9%, and the 4 dietary habits totally reflect 62.2% characteristics of the 10 food-groups.In urban area, prudent habit was inversely associated with DBP (β' = -0.026, P < 0.05) , Protein habit was inversely associated with both children's SBP (β' = -0.018, P < 0.05) and DBP (β' = -0.030, P < 0.05) .In rural area, prudent habit was associated with children's SBP (β' = -0.050, P < 0.05) and DBP (β' = -0.039, P < 0.05) .

CONCLUSIONSThe dietary habits of school age children varied by sociodemographic characters in Beijing. The prudent habit and protein habit may decrease the children's blood pressure levels.