[Impact of dynamic change of waist circumference or body mass index in hypertension incidence].

Objective: To study the impact of dynamic change of waist circumference (WC) and body mass index(BMI) in two years on hypertension incidence in cohort populations.

Methods: A perspective cohort study was conducted. The participants (5888 subjects) whose follow-time were 2 years or longer from the program Prevention of multiple metabolic disorders and metabolic syndrome (MS) in Jiangsu province were investigated. Amongst 5888 subjects, 4582 participants received the first follow-up investigation in January 2002. Among 4582 subjects who received first follow-up investigation and whose follow-time met 5 years, total 3847 participants received the second follow-up investigation in March 2006. Total 2778 free hypertension subjects were included in this analysis. Subjects with normal WC or BMI at baseline but abnormal WC or BMI at the first follow-up or subjects with abnormal WC or BMI both at baseline and the first follow-up were defined as non-control group. Subjects with abnormal WC or BMI at baseline but normal WC or BMI at the first follow-up or subjects with normal WC or BMI both at baseline and the first follow-up were defined as control group. The incidence of hypertension at second follow-up investigation was defined as the final variable(hypertension = 1, non-hypertension = 0). The association between dynamic change of WC or BMI and incident hypertension was analyzed by using Cox proportional hazards regression model. The OR, RR value and 95%CI were calculated through WC and BMI risk stratification.

Results: Among 2778 participants without hypertension at baseline, 660 subjects developed hypertension. When both BMI difference value (D-value) and WC D-value were included in the regression model, WC D-value was associated with hypertension in both genders (males: OR = 1.04, 95%CI: 1.01 - 1.05; females: OR = 1.04, 95%CI: 1.02 - 1.06), but BMI D-value was not associated with hypertension in both men and women (males: OR = 1.04, 95%CI: 0.97 - 1.11; females: OR = 0.98, 95%CI: 0.93 - 1.03). Hypertension risk of WC non-control group was higher than that in WC control group in baseline normal and abnormal WC groups (normal baseline WC group: RR = 1.41, 95%CI: 1.01 - 2.39, abnormal baseline WC group: RR = 4.41, 95%CI: 1.66 - 9.80). But in baseline abnormal BMI group, there was no significant difference between BMI control and non-control group (RR = 1.33, 95%CI: 0.88 - 2.02). Whether BMI was controlled can not influence hypertension risk if WC was controlled (males: RR = 1.03, 95%CI: 0.36 - 2.96; females: RR = 1.02, 95%CI: 0.70 - 5.85), however, control WC could reduce hypertension risk obviously even though BMI was not controlled (males: RR = 4.03, 95%CI: 1.61 - 10.09; females: RR = 1.55, 95%CI: 1.13 - 3.60).

Conclusion: Both WC and BMI dynamic change were associated with change of hypertension. But reducing WC can decrease hypertension risk more than reducing BMI.