Prevalence Of High Blood Pressure In Chinese Urban Children And Adolescents Based On Three Separate Occasions And Dietary Salt And Potassium Intake And Its Evaluation Methods

[Background]In 2012,the prevalence of hypertension(HTN)was 23.2%in China,twenty-hundred and forty billion adult Chinese people were hypertensive.Many moderate to strong evidence suggest that blood pressure(BP)in childhood could track into adulthood,and childhood high BP(HBP)can predict subclinical target organ damage,left ventricular remodeling and premature death in adulthood.Therefore,monitoring and management of HBP from childhood is critical to prevent lifelong cardiovascular diseases.Many school-based cross-sectional studies on prevalence of HBP in Chinese children and adolescents were conducted in recent years.However,most of these studies were based on BP measurement at only one occasion,which was against the recommendations,and the reported results were inconsistent.In adults,high salt intake plays a very important role in HTN.High potassium intake can lower BP and reduce the risk of cardiovascular disease.However,less evidence is available among children and adolescents,and findings are equivocal.The daily dietary salt intake of Chinese adults was about 10.5 g,which was 75%higher than the recommended^6.0 g/day.Few studies on salt and potassium intake was reported among Chinese children and adolescents.As the gold standard for estimating daily salt intake,24-h urine is burdensome to participants.Many researchers established equations based on spot virine to estimate 24-h urinary sodium excretion in adults,and these formulas were proved to be an alternative to 24-h urine in adults.But none of these formulas was validated in children and adolescents.[Objectives]1.To describe the prevalence of HTN among Chinese urban children and adolescents based on three separate occasions.2.To estimate the 24-h urinary salt and potassium excretion of urban children in three cities.3.To explore the performance of eight equations-Kawasaki,Tanaka,International Cooperative Study on Salt,Other Factors,and Blood Pressure(INTERSALT1),INTERSALT without potassium(INTERSALT2),Mage,Whitton,Uechi simple-mean,and Uechi-regression-at both population and individual levels in Chinese young adolescents.[Methods]The China Child and Adolescent Cardiovascular Health Study(CCACH)study was a school-based cross-sectional survey,wliich was conducted during 2012-2014.Children and adolescents from 3 cities in the northerm China and another 3 cities in the southern part were chosen to participate in this survey.Three consecutive BP readings were examined from each subject on the right arm in the morning at their first visit.Students with BP ≥95th percentile according to BP references for Chinese children underwent a second set of BP measurements at least two weeks later,and then a third screening if BP was>95th percentile at the second screening.A sub-sample in 3 cities of CCACH was chosen to collect 24-h urine to estimate the 24-h urinary salt and potassium excretion.Then another cross-sectional study was conducted in a primary and middle school in Hunan Changde.Boarding students from Grade 5 to 9 were recruited and two spot urine specimens and two-separate 24-h urine were collected from each participant in weekdays to evaluate the aceuracy of spot urine formulations which were established based on healthy adult populations in children and adolescents.SPSS 20.0 and R 3.5.1 were used to data analysis.[Results]In CCACH study,44 242 students from 6 cites were included in data analysis(boys,50.9%).The prevalence of HBP was 16.5%at the 1st visit,7.1%at the 2nd visit,and 4.0%at the 3rd visit,respectively.More than 90%participants who were hypertensive at the 1st and the 2nd visit attended the subsequent BP measurement.The prevalence of HTN would be around 4.6%if the dropped-out were considered.Six-hundred and twenty-eight subjects with complete 24-h urine in CCACH study were included in data analysis.The 24-h urinary salt excretion was 7.7 g and 1.3 g for potassium excretion.And the corresponding daily intake was 7.7 g for salt and 1.3 g for potassixxm.Almost three-in-four participants(73.6%)took in more salt than the recommended levels and more than 90%subjects(92.5%)had inadequate potassium intake.A total of 284 participants with two complete 24-h urine and two spot urine specimens were included in analysis in the second study.Using the averages of two 24-h urinary sodium and potassium excretions as references,only Tanaka method could estimate populational 24-h urinary sodium and potassium excretion accurately.All these equations were not recommended to estimate individual 24-h sodium or potassium excretion in our study.[Conclusions]1.The prevalence of hypertension among Chinese urban children and adolescents by three occasions was 4.0%.2.The problem of excessive salt intake and insufficient potassium intake was serious among Chinese children and adolescents.3.Among the 8 equations established in adults to estimate 24-h urinary sodium excretion and 2 equations to estimate 24-h urinary potassium excretion based on spot urine,only Tanaka method could be an alternative to estimate populational sodium and potassium excretion in Chinese children,and none of these formulas could be used to estimate individual sodium or potassium excretion in our study.