Prevalence Of Occasional Hypertension And Its Association With Altitude Among Tibetan Adolescents Aged 12-17 Years

BackgroundWith the epidemic of obesity and unhealthy lifestyles among children and adolescents,the onset of hypertension is becoming younger.More and more attention has been paid to hypertension in children and adolescents.It has been demonstrated that hypertension tracked from childhood to adulthood,and it will increases the risk of cardiovascular disease(CVD)in adulthood.In addition,hypertension in childhood have shown early target organ damage.Therefore,early identification of hypertension and effective interventions are essential to the healthy growth in childhood and reduce the burden of CVD in adulthood.There are many factors may influence the development of hypertension,environmental factors also play an important role.More and more studies pay attention to the association of altitude and hypertension.The Tibet Autonomous Region of China is located at high altitude in the Qing-Tibetan highland,and the average altitude is 4500m above sea level.A significant correlation between the prevalence of hypertension and altitude was presented among Tibetan inhabitants.With the development of the economy in Tibet,the prevalence of overweight and obesity among Tibetan children and adolescents has increased while the nutritional status has improved.Overweight and obesity are related to hypertension closely.Blood pressure(BP)status in Tibetan adolescents is less investigated,limiting the understanding of the BP status and the formulation of corresponding interventions.In addition,choosing an applicable BP references is also crucial to describe the BP status among children and adolescents.In recent years,China and other countries have successively updated and published more scientific BP references for children and adolescents,including Mi Jie' team updated the BP references based on age,sex,and height percentile for children and adolescents in 2017(hereafter referred to as"Guideline references"),Ma Jun' team developed health industry standards for screening elevated BP among children and adolescents in 2018(hereafter referred to as"Industry references"),Xi Bo' team established the international BP references among children and adolescents in 2016(hereafter referred to as "International references"),and the American Academy of Pediatrics updated the clinical practice guidelines for screening and management of high BP in children and adolescents in 2017(hereafter referred to as "US references").However,health surveys describing the prevalence of hypertension and its association with altitude among Tibetan children and adolescents based on the above four latest BP references have not been reported.Objectives(1)To define the elevated BP and occasional hypertension among Tibetan adolescents aged 12-17 years according to Guideline references,Industry references,International references and US references,and to describe the epidemic characteristics.(2)To assess the consistency of elevated BP and occasional hypertension between the four BP references among Tibetan adolescents.(3)To analyse the association of elevated BP and occasional hypertension with altitude among Tibetan adolescents.Subjects and methods1 SubjectsData were from the "Investigation project on influencing factors of hypertension among Tibetan Adolescents "performed in Shigatse city,Tibet municipality,2018.In this study,Yadong County(average altitude is 3400m),Sangzhuzi District(average altitude is 4000m)and Gamba County(average altitude is 4700m)were selected as the survey sites by using convient stratified cluster sampling method and stratified by altitude.There were 3 junior high schools(located in Yadong County,Sangzhuzi District,and Gamba County,respectively)and 3 senior high schools(located in Sangzhuzi District).In this survey,2,822 participants aged 12-17 years were initially recruited.After excluding 27 non-Tibetan adolescents,a total of 2,795 Tibetan adolescents were included in the analysis of the prevalence of hypertension.In the study of the association of elevated BP and hypertension with altitude,three senior high school adolescents were not included in the analysis because of living at the same altitude(Sangzhuzi District).Among 1,378 junior high school adolescents,after excluding those with incomplete information(n=77),a total of 1,301 adolescents aged 12-17 years were finally included.2 MethodsAnthropometric measurements and questionnaire surveys were performed on all Tibetan adolescents aged 12-17 years.Anthropometric measurements include height,weight,systolic blood pressure(SBP),diastolic blood pressure(DBP),and heart rate(HR).Pulse pressure(PP)and Mean arterial pressure(MAP)were calculated according to SBP and DBP,together with SBP and DBP as index to measure BP levels.Questionnaire survey include demographic information(gender,age,ethnicity),dietary intake information(salted butter tea,salted brick tea,barley wine),lifestyle information(smoking,screen time,sleep duration).3 Statistical analysisStatistical analyses were performed using SAS version 9.4.Continuous variables were presented as means±standard deviations(x±s),differences between different groups were assessed using independent t-tests or variance analysis.The categorical variables were expressed as percentages(%),differences in different groups were assessed using Chi-squared test.General linear regression model was used to examine the trend of BP level with age.Binary Logistic regression model was used to examine the trend in prevalence of elevated BP and hypertension with increase of age.Weighted Kappa values were calculated to assess the consistency of the prevalence of elevated BP and hypertension between four BP reference standards.After adjusting for sex and age,multivariable linear regression models were used to analyze the impact of increased altitude on BP levels;Binary Logistic regression models were used to examine the trends in prevalence of elevated BP and hypertension with increase of altitude.Multivariable Logistic regression models were used to analyze the association of elevated BP and hypertension with altitude among Tibetan adolescents.The odds ratios(ORs)and 95%confidence intervals(95%CIs)were calculated.Model 1 included sex,age.Model 2 additionally adjusted for BMI,screen time,sleep time,salted butter tea,salted brick tea,barley wine,and smoking.All statistical tests were two-sided,the level of significance was 0.05.Results1 Prevalence of elevated BP and hypertension among Tibetan adolescents aged 12-17 yearsThe average levels of SBP,DBP,PP,and MAP among Tibetan adolescents aged 12-17 years were 110.4±9.3 mmHg,60.9±8.2 mmHg,49.6±7.9 mmHg,and 77.4±7.7mmHg,respectively.The average levels of SBP,DBP,PP,and MAP increased with the increase of age(P for trend<0.05).The prevalence of elevated BP was 12.4%(Guideline references),12.7%(Industry references),11.6%(International references)and 11.7%(US references),respectively.The prevalence of elevated BP according to four BP references,boys were higher than girls;adolescents aged 15-17 years were higher than adolescents aged 12-14 years(all P<0.05).There were significant upward trends in the prevalence of elevated BP with increasing age,irrespective of the used BP references(all P for trend<0.05).The prevalence of hypertension were 8.5%(Guideline references),7.3%(Industry references),7.9%(International references)and 6.4%(US references),respectively.There were no significant differences in prevalence of hypertension between gender and age groups according to four BP references.Significant upward trend in prevalence of hypertension with age was only detected in Guideline references(P for trend<0.05).2 Consistency of elevated BP and hypertension between four BP references among Tibetan adolescentsExcept that the Guideline references and the US references were moderately consistent in 15-17 years among girls(kw=0.79),in different gender and age groups,any two of the four BP references presented high consistency in defining elevated BP and hypertension(all kw>0.80).P values corresponding to kw were all<0.001.3 Association of elevated BP and hypertension with altitude among Tibetan adolescentsCompared with the adolescents in Yadong County(average altitude is 3400 m),the levels of SBP,DBP,and MAP among adolescents in Sangzhuzi District(average altitude is 4000 m)and Gamba County(average altitude is 4700 m)increased(P<0.05).With the increase of altitude,the prevalence of elevated BP and hypertension increased significantly,irrespective of the used BP references(all P for trend<0.05).Similar results were observed in subgroups by sex.According to Guidelines references,after adjusted for variables as sex,age,BMI,screen time,sleep duration,salted butter tea,salted brick tea,barley wine,and smoking,compared with the adolescents in Yadong County,the risk of elevated BP prevalence increased among adolescents in Sangzhuzi District and Gamba County,OR values were 2.31(95%CI:1.27?4.21),and 3.19(95%CI:1.86?5.48),respectively.The risk of hypertension also increased,OR values were 4.63(95%CI:2.09-10.21),and 6.24(95%CI:3.00-12.99),respectively.After applying Industry references,International references,and US references,similar results were observed.Conclusions(1)According to Guideline references,Industry references,International references,and US references,the prevalence of elevated BP and hypertension among Tibetan adolescents aged 12-17 years was relatively high,and high consistency between different BP references was presented.(2)The prevalence of elevated BP tended to increase with increase of age,irrespective of the used BP references.Significant upward trends in the prevalence of hypertension with age only observed according to Guideline references.(3)Applying four BP references,the risk of elevated BP and hypertension increased with the increase of altitude among Tibetan adolescents aged 12-17 years.