[Trajectories of body mass index and risk of hypertension and blood pressure among Chinese adults].

Objective: To explore the relationship between trajectories of body mass index(BMI) and the risk of hypertension and blood pressure among Chinese adults.

Methods: The current study was based on data from 10 waves of the China Health and Nutrition Survey from 1991 to 2018. A multistage stratified random sample was used in this study.11885 adults whose BMI had been measured at least three times were included in the study. Group-based trajectory modeling(GBTM) was used to identify the BMI trajectories in different genders, Cox regression model was used to analyze the association between BMI trajectories and the risk of incident hypertension. Generalized linear model was used to analyze the association between BMI trajectories and the blood pressure level.

Results: Three distinct BMI trajectories were determined for both genders: normal-stable group, normal-overweight group, obesity-stable group. The numbers of each group among males were 3595(63.23%), 1412(24.83%) and 679(11.94%), and the numbers of each group among females were 4566(73.66%), 1214(19.58%) and 419(6.76%). Taking the normal-stable group as a reference, after adjusting for confounding factors, the normal-overweight group, obesity-stable group had 1.14(1.03-1.25), P=0.01 and 1.42(1.24-1.63), P<0.01 increased risk(HR(95% CI)) of developing hypertension in male. The normal-overweight group, obesity-stable group had 1.29(1.13-1.46), P<0.01 and 1.58(1.23-2.03), P<0.01 increased risk of developing hypertension in female. Taking the normal-stable group as a reference, after adjusting for confounding factors, the systolic blood pressure[β(95% CI)] in the male normal-overweight group and obesity-stable group increased by 3.01(1.88-4.14)mmHg, P<0.01 and 5.44(3.85-7.03)mmHg, P<0.01 respectively. The diastolic blood-pressure level was increased by 2.20(1.48-2.91)mmHg, P<0.01 and 4.04(3.04-5.04)mmHg, P<0.01 respectively. The systolic blood pressure in the female normal-overweight group and obesity-stable group were increased by 3.65(2.44-4.85)mmHg, P<0.01 and 2.96(0.97-4.94)mmHg, P<0.01 respectively. The diastolic blood pressure level was increased by 3.11(2.38-3.86)mmHg, P<0.01 and 1.25(0.03-2.47)mmHg, P=0.05 respectively.

Conclusion: Both the trajectory of BMI increasing with age and the trajectory of maintaining a high BMI level increased the risk of hypertension, and blood pressure also increased significantly compared with those who maintained normal BMI.