| BackgroundWith the development of social economy and lifestyle changes during recent years, chronic non-communicable diseases (NCD) such as obesity, hypertension and diabetes became the main killer for health. In 2014, "China Cardiovascular Diseases Report" pointed out that the number of hypertensive individuals had reached 270 millions among Chinese (ages of 18years). However, the control rate of hypertension in China is about 14%. Hypertensive individuals have become potential reserves of cardiovascular disease in China. On the other hand, hypertension becomes relatively common in the younger. As estimated, the prevalence of elevated blood pressure (BP) among school-aged children (ages of 6-17 years) was ～14% based on one occasion BP measurement, while the prevalence of true hypertension was ～3% based on BP measurements on three separate occasions. Besides, the onset of primary hypertension in adulthood is proved to be traced back to children. Thus, it is important to prevent hypertension in children and adolescent, in order to effectively lower risk of adult hypertension.Prevention of pediatric hypertension needs a series of works including prevention, diagnosis, intervention and treatment, and precise screening and definite diagnosis is the cornerstone. There are many factors that can influence stability of BP values in children and adolescents, including within-person variability (e.g., accommodation, nervous status, stress, etc.), and "white coat" effect, etc. Therefore, repeated BP readings on several occasions might be necessary for diagnosis of true hypertension. The 2004 US Fourth Report recommends that diagnosis of pediatric hypertension should be based on blood pressure (BP) measurements on at least three separate occasions. However, many investigations of hypertension rate mainly based on single visit, which may result in an overestimated prevalence of true hypertension.To our knowledge, the 2004 Fourth Report recommended that pediatric pre-hypertension and hypertension should be defined as systolic/diastolic BP (SBP/DBP) above the 90th and 95th percentiles by sex, age and height on three different occasions. However, there are 476 sex-, age- and height- specific cut-offs to assess the 90th and 95th percentiles of SBP and DBP among children aged 1-17 years for both sexes, which makes definition of raised BP in children BP cumbersome for clinicians. Alternatively, several simple and more user-friendly tools for screening elevated BP in children and adolescents have been suggested to be used in clinical practice. These simplified methods include the use of simple mathematical formulas, simplified tables by age and sex with or without height, and BP to height ratio (BPHR). It is therefore useful to compare the performance of these simplified methods in order to know whether these user-friendly methods to assess elevated BP among children and adolescents may be useful for routine screening.In order to acquire the true prevalence of hypertension among children and adolescent in Jinan, Shandong, we recruited about 8000 students from four primary and middle schools. Then, BP data was collected on at least three separate occasion blood pressure measurements. In addition, we compared the performance of eight simplified methods for screening elevated BP among the samples to determine the optimal simplified method for Jinan children and adolescent in Jinan.Objective1. To screen hypertensive children and adolescent based on three separate BP measurements, and to describe the distributions of prevalence of elevated blood pressure and related influencing factors in children and adolescents.2. To compare the performance of eight simplified methods for screening elevated BP among children and adolescents, and to determine the optimal simplified method for children and adolescent in Jinan.Subjects and methods1. Our study was based on the 12th Five-Year National Science and Technology Support Program-"Technology on Warning, Diagnosis and Treatment of Cardiovascular Disease in Children". Convenience cluster sampling method was used to select children in four middle-level schools (two elementary schools, one secondary school and one high school). To be somewhat representative of children and adolescents in Jinan, we chosen students (ages of 6-18 years) who were permanent residents or had lived in Jinan at least one year. Finally, a total of 7983 children and adolescents aged 6-18 years old were recruited, including 4163 boys (52.1%) and 3820 girls (47.9%).2. Anthropometric measurements including height (cm), weight (kg) and waist circumference (cm) were obtained. Children and adolescents with BP values above 95th percentiles by sex and age were invited to take part in the second and third screenings with about two-week intervals. A validated questionnaire was used to collect data on general demographic characteristics, born information, growth and development status, lifestyle factors (including dietary habits, sleep hours, sedentary behaviors and physical activity), familial history of diseases and parents information and so on, needed to be completed.3. Data were entered and double checked with EpiData software. SPSS 16.0 and MedCalc were used to analyze the data. If continuous data were non-normal distribution, then we changed them into normal distribution before analysis. The categorical variables were expressed as percentage, while mean±SD was used to present continuous variables. The methods of analyses included t-test, Chi-square test, binary logistic analysis and receiver operating characteristic curve (ROC). The two-side p value <0.05 was used to indicate statistical significance.Results1 Elevated BP screening based on three separated visits among children and adolescentsA total of 7983 subjects, aged 6 to 18 years old, with complete data were recruited at the first screening. Then,1345 (follow-up rate:92.2%) children and adolescents with elevated BP at the first visit were invited to have their BP measured at the second visit. In addition,630 (follow-up rate:85.9%) children or adolescents whose BP levels were still high were invited to participant in the third screening. The prevalence of elevated BP was 17.0%,9.2% and 5.3% at the first, second and third visits, respectively. Among children or adolescents with elevated BP, isolated elevated SBP was the main type, accounting for 65.6%,70.2% and 74.6% at the first, second and third visits, respectively. Boys had a higher prevalence of elevated BP during every separate screening compared to girls. The overall prevalence of elevated BP was significant higher in boys (20.3%,11.8%,7.3%) than that in girls (13.3%, 6.4%,3.2%) on the three visits (P<0.05). The levels of SBP and the prevalence of isolated elevated SBP were higher in boys than girls (P<0.001) on three separate screenings. No significant difference was found in the levels of DBP and prevalence of isolated elevated DBP among boys and girls (P>0.05) at the first visit, but the difference was obvious in the remain visits which showed higher prevalence in girls (P<0.05). The prevalence of elevated BP was increased with increased age group at the first visit, and the highest rate was observed in adolescents aged 16-18 years (overall:24.1%, boys:30.3%, girls:17.3%), and the lowest in children aged 10-12 years (overall:13.8%, boys:15.9%, girls:11.4%). However, the prevalence of elevated BP was highest in 13-15 years in both overall and boys, and girls still had the highest rate in age of 16-18 years. Similar trend was observed for both isolated elevated SBP and isolated elevated DBP among boys and girls. As is shown, the prevalence of hypertension after third screening was lower for each body mass index (BMI) percentile category as compared to first screening. The prevalence of elevated BP increased with increased BMI percentiles in both overall and boys, with highest rate in P95-P100 (overall:61.4%,44.0%,30.6% boys:26.3%,28.3%,32.8%), but the highest prevalence of elevated BP was in P50～P74 in girls (31.4%,28.3%,32.8%). Significant difference was observed in the prevalence of elevated BP based on increased waist circumference percentile (P<0.001).BP status at three separate visits was treated as the dependent variables. Influencing factors including gender, age, weight status, hypertension history of parents, puberty status, born information, education experience of parents, and sleep time were introduced to binary logistic analysis model. Risk of elevated BP on the three occasions were increased with the gender, hypertension history of parents, overweight and obesity (P<0.05). The odds ratios and 95% CIs for elevated BP were 1.66 (1.47-1.83),1.69 (1.34-2.11) and 2.40 (1.90-3.02), respectively, for boys compared to girls. The odds ratios and 95% CIs were 2.92 (2.49-3.42),4.32 (3.46-5.38),4.74 (3.46-6.50), respectively, among overweight children, and 7.43 (6.44-8.57),11.28 (9.30-14.89) and 16.01 (12.28-20.89), respectively, among obesity children, compared to normal weight children. The odds ratios and 95% CIs were 1.53 (1.25-1.86),1.77 (1.40-2.41) and 1.55 (1.14-2.11), respectively, for children with father having hypertension history, and 1.80 (1.33-2.44),1.68 (1.68-2.30) and 2.80 (1.87-4.18) for children with mother having hypertension history.2 Performance of eight simplified methods for the identification of elevated BP in children and adolescentsGenerally speaking, all the 8 screening methods performed well, with high AUC (0.89-0.96), high sensitivity (0.82-1.00), high specificity (0.84-0.99) and high positive predictive value (≥0.99). The sex-and age-specific 95th percentile BP values at the 50th percentiles of a child’s height (method A- Pso(H)), the age- specific 95th percentile BP values at the 50th percentiles of a child’s height (method B- Pso(H)) and the formula at 50th percentiles of a child’s height (method C- P50(H)) showed a higher area under the curve (AUC), sensitivity and specificity. The sex-and age- specific 95th percentile BP values at the 5th percentiles of a child’s height (method A- P5(H)), the age- specific 95th percentile BP values at the 5th percentiles of a child’s height (method B- P5(H)) and the formula at 5th percentiles of a child’s height (method C-P5(H)) showed a higher sensitivity but a lower specificity. Positive predictive value was a better index to reflect the true effect of a screening method. According to positive predictive value, the 95th percentile BP values for absolute height categories (method D) presented best efficacy (0.89) compared to other methods ranging from 041 to 0.67. The ratio between blood pressure and height is the simplest method that contains only four thresholds, but it showed low positive predictive value among younger children (0.39), although it had a better performance in adolescents (0.81).Conclusion1. The prevalence of pediatric elevated BP decreased from 17.0% to 5.3% from the first visit to the third visit. BP measurements on three different occasions should be recommended to define pediatric hypertension.2. Gender, overweight, obesity and hypertension history of parents were the main influencing factors for elevated BP in children and adolescents.3. The eight simplified methods performed well to identify elevated BP in children and adolescents, but the method based on a child’s absolute height performed best overall which may be most useful for screening purposes in clinical practice. |
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