[Relationship between waist circumference development curve of children and hypertension and risk of hypertension].

Objective: The 85th percentile of waist circumference (WC) is considered an appropriate cutoff for Chinese children in the prediction of cardiovascular risks in previous researches, but the risk for hypertension of moderate WC maybe underestimated. The purpose of this study was to understand the characteristics of the WC curve trajectory of children with hypertension and to determine the appropriate cutoffs for waist circumference for Chinese school-age children and adolescents for predicting hypertension risk factors.

Methods: A total of 8194 Han children aged 7 - 17 years were selected from schools in Suzhou, Hefei, and Chizhou cities in Anhui province by stratified cluster sampling. WC and blood pressure were accurately measured in all subjects. LMS (lambda-mu-sigma) method was used to construct WC centile curves. Optimal WC cutoffs were determined by comparing the performance of different percentile sets of WC cutoffs in predicting hypertension risk factors.

Results: The fitted LMS curves of WC for the group of boys with hypertension deviate in parallel from that for the corresponding curve in the entire boy study population with higher WC. The WC curves for the group of girls with hypertension gradually upward deviated from the corresponding curve before 12 years of age and then gradually returned to the corresponding curve. WC of boys at the percentiles of 60 was already associated with an increased risk of hypertension and hazard ratio of WC at percentiles of 60, 70, 80, and 90 increased from 1.88(95%CI: 1.18 - 2.99) to 4.87 (95%CI: 3.31 - 7.16). WC of girls at the percentiles of 70 was already associated with an increased risk of hypertension and hazard ratio of WC at percentiles of 70, 80, and 90 increased from 1.71 (95%CI: 1.07 - 2.73) to 3.32 (95%CI: 2.16 - 5.09).

Conclusions: The WC growth trajectory of children with hypertension varies with gender. WC is an independent predictor of childhood hypertension, even when it is well within what is now defined as the normal range of WC. Thus, it is helpful to prevent the risk of cardiovascular disease of children using the parameter that WC cut-off level lower than 85th percentile.