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Objective This longitudinal study aims to identify distinct trajectories of body mass index (BMI) and waist circumference (WC) during 20–60 years old, and explore their joint effect on incident hypertension.Design A longitudinal cohort study.Setting China Health and Nutrition Survey, 1993–2011.Participants The longitudinal cohort included 6571 participants (3063 men) who had BMI and WC repeatedly measured 3–7 times before incident hypertension or loss to follow-up.Outcomes Hypertension was defined as systolic blood pressure/diastolic blood pressure>140/90 mm Hg or diagnosis by medical records or taking antihypertensive medication.Results Two distinct trajectories were characterised for both BMI and WC: low-increasing and high-increasing. Jointly, subjects were divided into four groups: normal (n=4963), WC-increasing (n=620), BMI-increasing (n=309) and BMI&WC-increasing (n=679). Compared with the normal group, the adjusted HRs and 95% CIs for hypertension were 1.43 (1.19 to 1.74), 1.51 (1.19 to 1.92) and 1.76 (1.45 to 2.14) for WC-increasing, BMI-increasing and BMI&WC-increasing groups, respectively. The model-estimated levels and slopes of BMI and WC were calculated at each age point in 1-year interval according to the model parameters and their first derivatives, respectively. The associations between model-estimated levels and hypertension increased with age, with adjusted ORs and 95% CIs ranging from 0.92 (0.86 to 0.98) to 1.57 (1.47 to 1.67) for BMI and 0.98 (0.92 to 1.05) to 1.44 (1.35 to 1.53) for WC. Conversely, the ORs (95% CIs) of level-adjusted linear slopes decreased with age, ranging from 1.47 (1.38 to 1.57) to 0.97 (0.92 to 1.03) for BMI and 1.36 (1.28 to 1.45) to 0.99 (0.93 to 1.06) for WC.Conclusions Our study demonstrates that the joint trajectories of BMI and WC have significant effect on future hypertension risk, and the changing slopes of BMI and WC during young adulthood are independent risk factors. Both BMI and WC should be paid more attention to prevent hypertension, and young adulthood may be a crucial period for intervention.

Objectives The prevalence of childhood hypertension is rising in parallel with the increasing prevalence of overweight and obesity in children. How growth trajectories from childhood to puberty relate to high blood pressure (HBP) is not well defined. We aimed to characterise potential body mass index (BMI) dynamic changing trajectories from childhood to puberty and investigate their association with HBP.Design A dynamic prospective cohort.Setting China Health and Nutrition Survey 1991–2015.Participants There were 1907 participants (1027 men and 880 women) in this study.Outcomes The primary outcome was HBP defined as systolic blood pressure (SBP)/diastolic blood pressure (DBP) exceeding the standards or diagnosis by medical records or taking antihypertensive medication.Results A model of cubic parameters with three groups was chosen, labelled as normal increasing group (85.16%, n=1624), high increasing group (9.81%, n=187) and resolving group (5.03%, n=96). Compared with the normal increasing group, the unadjusted HRs (95% CIs) for the resolving and high increasing groups were 0.91 (0.45 to 1.86) and 1.88 (1.26 to 2.81), respectively. After adjusting for baseline age, region, sex, baseline BMI z-score, baseline SBP and baseline DBP in model 3, the HRs (95% CIs) for the resolving and high increasing groups were 0.66 (0.30 to 1.45) and 1.56 (1.02 to 2.38).Conclusions These results indicate that the BMI trajectories from childhood to puberty have significant impact on HBP risk. Puberty is a crucial period for the development of HBP.