Associations Of Abdominal Obesity And Its Four-year Change With High Blood Pressure In Childhood

BackgroundCardiovascular disease(CVD)is one of the leading causes for death and loss of healthy life of residents.As the most important risk factor of CVD,the health hazard associated with high blood pressure(BP)has aroused widespread concern,and has become an important public health issue.According to the China Cardiovascular Health and Disease report in 2021,there are 330 million patients with CVD and 245 million patients with high BP in China.In recent years,the prevalence of high BP in China has increased rapidly,and tends to be a younger trend.According to the data of China Health and Nutrition Survey,the detection rate of high BP in children aged 7-17 in China has increased from 8.5%in 1991 to 19.2%in 2015,and some children with high BP have developed cardiovascular target organ damage,which poses a serious threat to children’s health.Due to a long-term "trajectory" phenomenon in BP,and high BP in adults originated in childhood.Therefore,it is of great significance to explore the childhood risk factors of high BP for the advance of high BP and CVD prevention time.Obesity is one of the most important risk factors for high BP.The commonly used evaluation indexes are body mass index(BMI),waist circumference(WC)and waist to height ratio(WHtR).BMI is used to evaluate general obesity,while WC and WHtR are used to evaluate abdominal obesity.WC and WHtR can better reflect the distribution of abdominal fat when comparing with BMI.Epidemiological studies showed that there was no significant difference in the odds of high BP between overweight or obese individuals who recovered to normal BMI later and those who maintain normal BMI.However,few studies have examined the association between change in abdominal obesity status and high BP in childhood,whether reversing the status of high WC or high WHtR in childhood can reduce the odds of high BP still remains unclear.Therefore,based on the "Huantai Childhood Cardiovascular Health Cohort",the current study aimed to examine the relationship between changes in WC and WHtR status over 4 years and high BP,so as to provide scientific basis for the prevention of high BP and CVD in children.Objectives1.To examine the association of abdominal obesity defined by WC and WHtR with high BP in childhood.2.To examine the association of the 4-year change of abdominal obesity status defined by WC and WHtR with high BP in childhood.3.To compare the effects of WC and WHtR in predicting childhood high BP.MethodsData were from the baseline survey(2017)and the recent follow-up survey(2021)of the"Huantai Childhood Cardiovascular Health cohort study",which was conduct in a school in Huantai County,Zibo City,Shandong Province by using convenient cluster sampling method.There were 1515 children in the baseline survey and 1346 in the follow-up survey.After excluding the missingness on related variables,1508 children at baseline and 1312 children at follow-up were included,of which 1308 children had complete information in both surveys.In order to study the association between change of abdominal obesity and high BP,after further excluding children with high BP at baseline,a total of 1106 children were included in the analysis.The status of abdominal obesity was evaluated by WC or WHtR,and high WC(WC≥ sex-,age-90th percentile)or high WHtR(WHtR≥ 0.5)was defined as abdominal obesity,respectively.According to the WC status at baseline and follow-up(high vs.normal),the children were divided into four groups:persistent normal WC(normal WC at both baseline and follow-up),WC loss(high WC at baseline but normal WC at follow-up),WC gain(normal WC at baseline but high WC at follow-up),and persistent high WC(high WC at both baseline and follow-up).Following the same rules,children were also divided into four groups according to WHtR status at baseline and follow-up.Children’s BP≥P95 for specific age,sex and height was defined as high BP.This study was approved by the Ethics Committee of School of Public Health,Shandong University(approval number:20160308),and all children and their guardians signed a written informed consent.Statistical analysisFirstly,the basic characteristics of the participants were presented as mean±standard deviation(SD)for each continuous variable and frequency(percentage)for each categorical variable,and the differences across different groups were compared using variance analysis for continuous variables and chi-square test for categorical variables.Secondly,multiple linear regression models were used to explore the association of WC,WHtR with BP in children.Multivariate logistic regression models were used to explore the association of status of WC or WHtR and its changes over 4 years with high BP.The generalized estimation equation(GEE)was used to explore the association of WC,WHtR with BP,as well as the association of high WC,high WHtR with high BP.Finally,the receiver operating characteristic curve(ROC)was used to compare the effects of baseline WC and WHtR in predicting high BP in childhood,and the area under the curve(AUC)was calculated.The covariates adjusted in current study included gender,age,sleep duration,intake of vegetables and fruits,intake of soft drinks,physical activity and screen time.Two side P<0.05 indicates that the difference across groups is statistically significant.Results1.Association between childhood abdominal obesity and high BPThe prevalence of high BP at baseline and follow-up was 14.59%and 19.44%,respectively.Individuals with high WC or high WHtR had higher prevalence of high BP than those with normal WC or normal WHtR(P<0.05).After adjusting for the potential related covariates,the results of multiple linear regression analysis showed that both WC and WHtR were positively correlated with BP(P<0.001).The results of multivariate logistic regression analysis showed that children with high WC had an increased odds of high BP compared with those with normal WC,the corresponding odds ratios(ORs)(95%confidence intervals[CIs])at baseline and follow-up were 2.92(2.17-3.93)and 4.49(3.29-6.13),respectively.Compared with children who had normal WHtR,those with high WHtR had increased odds of high BP,and the ORs(95%CIs)at baseline and follow-up were 3.02(2.23-4.11)and 4.77(3.53-6.46),respectively.The results of GEE showed that both WC and WHtR were positively correlated with BP(P<0.001),and high WC and high WHtR in childhood were positively correlated with high BP,the coefficients(95%CIs)were 1.08(0.85-1.32)and 1.07(0.84-1.30),respectively.2.Association between change of abdominal obesity status and childhood high BPThe prevalence of high BP in children with persistent normal WC,WC loss,WC gain and persistent high WC was 7.02%,11.32%,12.77%and 31.85%,respectively.Compared with children who had persistent normal WC,children with WC gain(OR=4.52,95%CI:2.54-8.07)and persistent high WC(OR=7.67,95%CI:5.12-11.49)had increased odds of high BP,while children with WC loss(OR=1.45,95%CI:0.54-3.90)had no increased odds of high BP.The prevalence of high BP in children with persistent normal WHtR,WHtR loss,WHtR gain and persistent high WHtR was 8.70%,11.76%,14.85%and 44.77%,respectively.Compared with children who had persistent normal WHtR,those who were WHtR gain(OR=2.03,95%CI:1.09-3.76)and persistent high WHtR(OR=8.10,95%CI:5.41-12.13)had increased odds of high BP,while children who were WHtR loss(OR=1.18,95%CI:0.48-2.92)had no increased odds of high BP.3.Comparison of the effects of baseline WC and WHtR in predicting childhood high BPThe results of ROC analysis showed that both WC-Z score and WHtR-Z score were predictive for high BP among children,and predictive effects of WC-Z score(AUC=0.72,95%CI:0.68-0.77)were similar to WHtR-Z score(AUC=0.70,95%CI:0.66-0.75).Conclusions1.Both WC and WHtR are positively associated with BP in childhood,and children with abdominal obesity defined by WC or WHtR have increased odds of high BP.2.The four-year change of WC or WHtR status in childhood is associated with high BP in children.Abdominal obesity increases the odds of high BP in childhood,and reversing abdominal obesity status to normal WC(or normal WHtR)can reduce the odds of high BP in childhood.3.WC and WHtR are predictive in childhood high BP four years later,and their predictive effects are similar.