Secular Trends in Blood Pressure in Chinese Children and Adolescents Born 1981-2000: The Impact of Changing Growth Trajectories

Background: Globally, 80% of cardiovascular disease (CVD) deaths occur in low-/middle-income countries. High blood pressure (BP) is a major risk factor for CVD and has its origins in early-life. Childhood development of BP provides important information about the development of CVD risk. This study investigated how age trajectories of BP, from child to late adolescence, have changed in recent decades in China, and the mediating roles of physical growth. Methods: We used longitudinal data on 5,118 children with physical measurements between 7-18y from the China Health and Nutrition Survey 1991-2015. We applied fractional polynomial models with random effects to estimate mean trajectories of BP, BMI and height for cohorts born in 1981-85, 1986-90, 1991-95, and 1996-2000. Models for BP trajectories were also adjusted for BMI and/or height growth to assess their impact on BP trends. Results: BP trajectories (7-18y) shifted upwards with successive cohort. Compared to the earliest cohort, mean BP was higher in the latest cohort throughout childhood to late-adolescence. The increment in systolic BP was 3.8mmHg [95% CI: 2.5-5.1] in boys and 3.9mmHg [2.6-5.3] in girls at 9y, narrowed slightly during adolescence, remained at 2.8mmHg [0.7-4.9] and 2.3mmHg [0.3-4.3] respectively at 17y. Diastolic BP had similar increments to systolic BP in childhood and adolescence, but little increment in late-adolescence in girls. BMI and height trajectories also shifted upwards. The overall increment (in z-scores) was greater for height (0.55 [0.47-0.63]) than BMI (0.28 [0.20-0.35]). When adjusting for physical growth, the increment in systolic BP trajectories reduced but remained in childhood (p<0.05). The reduction was greater with adjustment for height than for BMI and the pattern was more evident in boys. Conclusions: The upward trends in BP trajectories over time among Chinese youths was largely (not entirely) explained by the increasing trends in physical growth, especially in height. The increment in BP remained in childhood after adjusting for growth, suggesting that other early-life factors might also contribute to the BP trends in Chinese children. How changes in BP within a short time frame will affect future CVD in the long term is unclear, particularly in the developing world. Funding Statement: This work was supported by the UCL Overseas Research Scholarship and China Scholarship Council to MG, https://www.csc.edu.cn/. Declaration of Interests: None declared. Ethics Approval Statement: The University of North Carolina and the Chinese Centre for Disease Control and Prevention reviewed and approved the data collection procedures.