Prospective Cohort Study On Body Mass Index Trajectory And Incidence Of Hypertension Among Population With Normal Body Mass Index In Rural Areas Of Liaoning Province

Objective: Hypertension is one of the primary factors for cardiovascular disease(CVD)and the leading cause of death in China.With the rapid development of society and economy,the prevalence of hypertension is increasing year by year.Especially in rural areas of China,hypertension has caused a huge economic burden,so it is particularly important to find changeable risk factors for hypertension.Studies have shown that high body mass index(BMI)is closely related to the incident hypertension.However,the BMI level at a single time point in previous studies did not fully reflect the role of BMI in the occurrence and development of hypertension.Therefore,the purpose of this study is to explore whether there are different body mass index(BMI)trajectories among the normal BMI population,and whether there is an association between different BMI trajectory groups and incident hypertension and its subtypes.Methods: We conducted a prospective cohort study in the rural area of Fuxin City,Liaoning Province,China,including baseline and three follow-up surveys.3939 participants who are free of hypertension at baseline or first two follow-ups were enrolled.The BMI trajectories were identified using group-based trajectory modeling method(GBTM)with data from the baseline and first two follow-ups.The outcome of the study was incident hypertension between the second follow-up and the third follow-up.We evaluated the hazard ratios(HRs)and 95% confidence intervals(CIs)of different BMI trajectories and the risk of hypertension using the multivariate Cox proportional hazards model adjusting the confounding factors at baseline.Results: We identified four distinct BMI trajectories during 2004–2010: normal-stable(n= 1456),normal-increasing(n = 2159),normal-fluctuated(n = 166),and normal-sharp-increasing(n = 158)groups.Relative to the normal-stable BMI group,the hazard ratios(HRs)(95% confidence intervals(CIs))for the normal-increasing,normalfluctuated,and normal-sharp-increasing groups were 1.244(1.103–1.402),1.331(1.008–1.756),and 1.641(1.257–2.142),respectively,adjusted for confounding factors.Individuals with normal-increasing BMI pattern had a higher risk of both isolated systolic hypertension(ISH)((adjusted HR(95% CI),1.269(1.015–1.585))and systolic and diastolic hypertension(SDH)(1.275(1.091–1.491))than those with normal-stable BMI pattern.Additionally,in subgroup analysis,the normal-fluctuated BMI trajectory significantly elevated hypertension risk only in women,with HR(95% CI)of 1.362(1.151–1.611).Conclusion: The BMI trajectories were significant predictors of hypertension incidence,and increasing BMI trajectories within the currently designated normal range may still increase hypertension risk.Especially for women,fluctuations in BMI also increase the risk of hypertension.Paying attention to the dynamic change process of BMI will provide a basis for effective prevention of hypertension.