Abstract
The prevalence of elevated blood pressure (BP) among US children and adolescents has reportedly declined over the past decade. As no Korean data have been analyzed, we aimed to determine recent trends in BP levels among Korean children and adolescents. This study examines data from the Korea National Health and Nutrition Examination Survey segregated into 3 time periods (2007‐2009, 2010‐2012, and 2013‐2015). A total of 7804 Korean children and adolescents aged 10‐18 years were included in the analysis. Hypertension (≥95th percentile) and elevated BP (>90th percentile) were defined using the sex‐, age‐, and height‐specific BP standards from 2017 American Academy of Pediatrics guidelines. Mean systolic BP from 2007‐2009 to 2013‐2015 increased by 3.9 mm Hg, and there was no significant change in diastolic BP. Body mass index (BMI) z‐scores significantly increased in the total population from 2007‐2009 to 2013‐2015. In 2013‐2015, the prevalence rates of elevated BP and hypertension were 8.8% and 9.0%, respectively. The prevalence of hypertension in 2013‐2015 increased in the total population compared with those in 2007‐2009, especially in the obese subgroup, in which the hypertension prevalence was 27.7% in 2013‐2015. The prevalence of elevated BP increased during these time period. Associated factors were sex, age, BMI z‐score, and survey period for elevated BP; and sex, age, and BMI z‐score for hypertension. During our study, mean systolic BP increased, and the prevalence of hypertension in 2013‐2015 increased in the pediatric population. A possible influencing factor is obesity, and further long‐term data are necessary.
Keywords: blood pressure, children, hypertension, obesity, trends
1. INTRODUCTION
Hypertension in children and adolescents is a serious public health problem because of associated increases in risks of end‐organ damage, especially cardiovascular diseases such as ventricular hypertrophy, congestive heart failure, and peripheral vascular disease.1 Children with hypertension are two to three times more likely than the general population to develop hypertension in adulthood.2 Early identification and proper intervention of hypertension on children and adolescents are therefore important.
The prevalence of elevated blood pressure (BP) among US children and adolescents has declined over the past decade. According to Data from the National Health and Nutrition Examination Survey (NHANES), the prevalence of youths with combined elevated BP/hypertension significantly declined from 16.2% in 2003‐2004 to 13.3% in 2015‐2016.3 Previous data from NHANES showed that the prevalence of elevated BP and hypertension in US children and adolescents was lower in 2009‐2012 compared with 1999‐2002, possibly due to dietary factors.4 Data from the Korea National Health and Nutrition Examination Survey (KNHANES) between 1998 and 2008 revealed that systolic blood pressure (SBP) decreased and the prevalence of prehypertension/hypertension decreased in children adolescents.5 However, there is no recent relevant report on Korean children and adolescents. Danaei et al investigated global trends in SBP by examining 5.4 million adult participants over 786 country‐years and reported that SBP had decreased slightly since 1980, but trends varied significantly across regions and countries.6 It was therefore necessary to examine BP trends and associated factors by region and country to establish effective public health policy.
The current study analyzed recent trends in BP levels and the prevalence of hypertension among Korean children and adolescents using KNHANES data collected from 2007 to 2015. We also analyzed potential contributing factors, including diet and physical activity.
2. METHODS
2.1. Study participants
This study segregated data obtained from KNHANES 2007‐2015 into 3 time periods (2007‐2009, 2010‐2012, and 2013‐2015). The KNHANES is a nationally representative surveillance survey that has been conducted cross‐sectionally since 1998 by the Korea Centers for Disease Control and Prevention and the Ministry of Health and Welfare. A multi‐stage clustered probability design was applied to KNHANES to reflect Korean general population. Detailed methods for KNHANES data collection are described elsewhere.7
Among 73 353 individuals enrolled in the KNHANES during 2007‐2015, whole subjects aged 10‐18 years (n = 8511) included as potential participants for the present study, because BP was measured in the participants aged 10 years old or more in the KNHANES. Finally, a total of 7804 subjects were included in the analysis after excluding those who met one or more of the following criteria: no BP data (n = 613); diastolic blood pressure (DBP) values <30 mm Hg (n = 9); no anthropometric data (n = 598); estimated glomerular filtration rate (GFR) by Schwartz equation8 <60 mL/min/1.73 m2 (n = 14); history of congenital heart disease (n = 62); or pregnancy (n = 0). Informed consent was obtained from the all participants. The KNHANES protocol was approved by the Institutional Review Board of the Korea Centers for Disease Control and Prevention. The present study was approved by the Institutional Review Board of Seoul National University Bundang Hospital (IRB No. X‐1906/547‐903). All procedures were performed in accordance with the Declaration of Helsinki.
2.2. Measurement of anthropometric data
Height, body weight, and waist circumference (WC) were measured by well‐trained medical staff members using calibrated equipment according to standardized protocols. Height was determined to the nearest 0.1 cm using a stadiometer (Seca 225, Seca). Weight was measured to the nearest 0.1 kg using an electronic balance (GL‐6000‐20, G‐tech). Body mass index (BMI) was calculated by dividing weight in kilograms by the square of height in meters and then transformed to a standard deviation score (z‐score) using the CDC 2000 Growth Chart.9 Obesity was diagnosed when a participant's BMI was in the 95th percentile or higher for corresponding sex and age.
2.3. Measurement and definition of blood pressure and hypertension
In the KNHANES, BP was measured using a mercury sphygmomanometer after the subject had rested for 5 minutes in a sitting position [Baumanometer Desk model 0320 in 2007‐2012 and Baumanometer Wall Unit 33(0850) in 2013‐2015, WABaum]. All BP measurements were taken on the right arm three times using the same instruments at 30‐second intervals with a cuff appropriate for arm circumference. The average values of the second and third measurements of SBP and DBP were used for subsequent analyses. For the 2017 American Academy of Pediatrics references, age‐, sex‐, and height‐specific BP percentiles were calculated for SBP and DBP and classified as normal, elevated BP, stage 1 hypertension, and stage 2 hypertension.10 For participants aged 18 year, BP was categorized as normal for <120/<80 mm Hg; elevated BP for 120/<80 to 129/<80 mm Hg; stage 1 hypertension for 130/80 to 139/89 mm Hg; and stage 2 hypertension for ≥140/90 mm Hg.
2.4. Measurement of health‐related lifestyles and daily intake
Information on health‐related lifestyles was collected using a self‐reported questionnaire during the interview portion of the survey. Physical activity was assessed using the Korean version of the International Physical Activity Questionnaire.11 A 24‐hour dietary recall questionnaire conducted by trained interviewers was used to collect information on the dietary intake of all participants. The dietary questionnaire was conducted face‐to‐face and included the type, amount, and frequency of foods or drinks consumed during the previous day. Data on food items were converted to nutrient units using the Food Composition Table developed by the National Institute of Agricultural Sciences (7th revision) and the database of the Korean Health Industry Development Institute (for instant and imported foods).
2.5. Statistical analysis
Statistical analyses were performed using Stata 16.0 Software (StataCorp LP). The svy command with appropriate sample weights was applied for the analysis. All data were expressed as weighted means with standard error for continuous variables and the number of subjects with weight percentage for categorical variables. Student t tests and linear regression analyses were used to compare continuous variables. Chi‐squared tests and logistic regression analysis were used to compare categorical variables. Multivariable logistic regression analysis was applied to the factors influencing elevated BP or hypertension. The trends in mean SBP, DBP, prevalence of elevated BP, and hypertension were analyzed across 3 time periods (2007‐2009, 2010‐2012, and 2013‐2015). P values < .05 were considered statistically significant.
3. RESULTS
3.1. Characteristics of study participants
Sex and age distributions did not differ significantly across the 3 periods (2007‐2009, 2010‐2012, and 2013‐2015). Table 1 presents the trends in anthropometric factors, and there were no significant changes in the proportion of obese and overweight individuals from 2007‐2009 to 2013‐2015, while BMI z‐scores significantly increased in the total population from 2007‐2009 to 2013‐2015. Additionally, abdominal obesity increased from 2007‐2009 to 2013‐2015 in males, but not in females. For dietary factors, the daily intake of calories, total fat, carbohydrate, protein, fiber, and water increased, while that of sodium decreased significantly. No significant change was seen in physical activity from 2007‐2009 to 2013‐2015.
Table 1.
Characteristics of study participants (N = 7804, age 10‐18 y)
| Variables | 2007‐2009 (n = 2932) | 2010‐2012 (n = 2669) | 2013‐2015 (n = 2203) | P value | P for trend |
|---|---|---|---|---|---|
| Male n, (%) | 1542 (53.2%) | 1427 (54.0%) | 1193 (53.0%) | .774 | .908 |
| Age (year) | 14.5 ± 0.1 | 14.7 ± 0.1* | 14.7 ± 0.1* | .001 | .030 |
| Height z‐score | 0.04 ± 0.02 | 0.02 ± 0.02 | 0.02 ± 0.02 | .791 | .588 |
| BMI z‐score (all) | 0.09 ± 0.02 | 0.07 ± 0.02 | 0.20 ± 0.03** | .002 | .004 |
| BMI z‐score (male) | 0.20 ± 0.03 | 0.11 ± 0.04 | 0.26 ± 0.04 | .034 | .297 |
| BMI z‐score (female) | −0.04 ± 0.03 | 0.02 ± 0.03 | 0.13 ± 0.03** | .001 | <.001 |
| BMI category | |||||
| Obesity | 199 (6.6%) | 180 (6.3%) | 177 (7.7%) | .461 | .199 |
| Overweight | 434 (14.2%) | 408 (14.7%) | 342 (14.6%) | .244 | |
| Abdominal obesity | 244 (8.2%) | 220 (8.8%) | 223 (10.7%) | .029 | .008 |
| Dietary factors | |||||
| Calories (Kcal/d) | 1935 ± 18 | 2180 ± 24** | 2204 ± 26** | <.001 | <.001 |
| Total fat (g/d) | 47.4 ± 0.7 | 57.6 ± 1.0** | 60.6 ± 1.0** | <.001 | <.001 |
| Carbohydrates (g/d) | 308.1 ± 2.9 | 336.1 ± 3.5** | 326.0 ± 3.5** | <.001 | <.001 |
| Protein (g/d) | 68.0 ± 0.7 | 78.8 ± 1.2** | 78.9 ± 1.3** | <.001 | <.001 |
| Fiber (g/d) | 5.4 ± 0.1 | 5.5 ± 0.1 | 18.3 ± 0.3** | <.001 | <.001 |
| Water (g/d) | 780.0 ± 11.4 | 891.7 ± 16.4** | 965.0 ± 17.4** | <.001 | <.001 |
| Sodium (mg/d) | 3982 ± 50 | 4166 ± 71** | 3476 ± 60** | <.001 | <.001 |
| Moderate‐to‐vigorous physical activity (min/d) | 31.5 ± 1.5 | 32.5 ± 1.6 | 30.6 ± 1.3 | .648 | 0.650 |
Data were expressed as weighted mean ± SE.
Abbreviation: BMI, body mass index.
P < .05 compared with KNHNAES wave 4 (2007‐2009).
P < .01 compared with KNHNAES wave 4 (2007‐2009).
3.2. Trends in mean BP values from 2007‐2009 to 2013‐2015
Mean SBP levels significantly increased from 2007‐2009 to 2013‐2015 in the total population, while DBP values did not increase (Figure 1). The average differences in mean SBP between 2007‐2009 and 2013‐2015 were 3.9 mm Hg in total participants, 4.2 mm Hg in boys, and 3.8 mm Hg in girls (Table 2).
Figure 1.
Trends in systolic and diastolic blood pressure by sex (A) and degree of obesity (B)
Table 2.
Trends in mean blood pressure levels of study participants (N = 7804, age 10‐18 y)
| Group | BP | 2007‐2009 | 2010‐2012 | 2013‐2015 | P value | P for trend |
|---|---|---|---|---|---|---|
| Total | SBP (mm Hg) | 104.3 ± 0.3 | 106.1 ± 0.3** | 108.2 ± 0.3** | <.001 | <.001 |
| DBP (mm Hg) | 65.5 ± 0.3 | 65.5 ± 0.3 | 66.0 ± 0.3 | .239 | .161 | |
| Male | SBP (mm Hg) | 106.4 ± 0.4 | 108.2 ± 0.4** | 110.6 ± 0.4** | <.001 | <.001 |
| DBP (mm Hg) | 66.2 ± 0.3 | 65.9 ± 0.3 | 66.3 ± 0.3 | .573 | .795 | |
| Female | SBP (mm Hg) | 101.9 ± 0.3 | 103.6 ± 0.4** | 105.7 ± 0.3** | <.001 | <.001 |
| DBP (mm Hg) | 64.7 ± 0.3 | 65.0 ± 0.3 | 65.6 ± 0.3 | .097 | .034 |
Abbreviation: DBP, diastolic blood pressure; SBP, systolic blood pressure.
P < .01 compared with KNHNAES wave 4 (2007‐2009).
3.3. Trends in prevalence of elevated BP and hypertension from 2007‐2009 to 2013‐2015
The prevalence rates of elevated BP and hypertension were 5.4% and 6.9% in 2007‐2009 and 8.9% and 9.0% in 2013‐2015, respectively (Figure 2). Compared with those in 2007‐2009, the prevalence of hypertension in 2013‐2015 increased in the total population, and especially in the obese subgroup, which saw a hypertension prevalence of 27.7% in 2013‐2015 (Table 3). The prevalence of elevated BP increased significantly in the total population and all subgroups by sex and degree of obesity.
Figure 2.
Trends in prevalence of children and adolescents with elevated blood pressure and hypertension
Table 3.
Trends in prevalence of elevated blood pressure and hypertension of study participants (N = 7804, age 10‐18 y)
| Group | BP category | 2007‐2009 | 2010‐2012 | 2013‐2015 | P value |
|---|---|---|---|---|---|
| Total | Hypertension | 190 (6.9%) | 190 (8.2%) | 200 (9.0%) | .025 |
| Elevated BP | 148 (5.4%) | 177 (7.3%) | 196 (8.9%) | <.001 | |
| Elevated BP + hypertension | 338 (12.3%) | 367 (15.5%) | 396 (17.9%) | <.001 | |
| Obese | Hypertension | 30 (14.9%) | 31 (16.9%) | 45 (27.7%) | .008 |
| Elevated BP | 25 (15.8%) | 31 (17.6%) | 30 (17.3%) | .780 | |
| Elevated BP + hypertension | 55 (30.7%) | 62 (34.5%) | 75 (45.0%) | .019 | |
| Non‐obese | Hypertension | 160 (6.3%) | 159 (7.6%) | 155 (7.4%) | .219 |
| Elevated BP | 123 (4.7%) | 146 (6.6%) | 166 (8.2%) | <.001 | |
| Elevated BP + hypertension | 283 (11.0%) | 305 (14.2%) | 321 (15.6%) | <.001 | |
| Male | Hypertension | 125 (8.9%) | 127 (10.2%) | 131 (11.3%) | .103 |
| Elevated BP | 101 (7.2%) | 124 (9.7%) | 139 (11.9%) | .001 | |
| Elevated BP + hypertension | 226 (16.1%) | 251 (20.0%) | 270 (23.2%) | <.001 | |
| Female | Hypertension | 65 (4.6%) | 63 (5.7%) | 69 (6.4%) | .092 |
| Elevated BP | 47 (3.4%) | 53 (4.5%) | 57 (5.4%) | .042 | |
| Elevated BP + hypertension | 112 (8.0%) | 116 (10.2%) | 126 (11.8%) | .008 |
Obese, BMI ≥ 95th percentile; non‐obese, BMI < 95th percentile
Abbreviation: BP, blood pressure.
3.4. Influencing factors for elevated BP and hypertension
Linear regression analysis revealed a positive association between BMI z‐score and BP (Figure 3). In multiple logistic regression analysis, the factors affecting elevated BP were male sex, increased age, higher BMI z‐score, higher height z‐score, lower estimated GFR, and recent survey period. Factors affecting hypertension were male sex, increased age, higher BMI z‐score, the presence of abdominal obesity, and lower estimated GFR (Table 4). Dietary factors and physical activity showed no association with elevated BP and hypertension.
Figure 3.
Association between BMI z‐score and systolic (A) and diastolic (B) blood pressure. Solid lines and blue dots for boys and dotted lines and red dots for girls
Table 4.
Influencing factors for elevated blood pressure and hypertension
| Variables | Unadjusted | Adjusted* | ||||
|---|---|---|---|---|---|---|
| OR | 95% CI | P value | OR | 95% CI | P value | |
| Elevated BP (BP > 90th percentile) | ||||||
| Survey period | ||||||
| 2007‐2009 | 1 (Base) | 1 (Base) | ||||
| 2010‐2012 | 1.30 | 1.06‐1.60 | .013 | 1.35 | 1.01‐1.79 | .042 |
| 2013‐2015 | 1.55 | 1.26‐1.91 | <.001 | 1.48 | 1.11‐1.99 | .008 |
| Sex | ||||||
| Female | 1 (Base) | 1 (Base) | ||||
| Male | 2.21 | 1.89‐2.59 | <.001 | 2.48 | 1.89‐3.26 | <.001 |
| Age (years) | 1.06 | 1.02‐1.09 | .001 | 1.17 | 1.10‐1.26 | <.001 |
| BMI z‐score | 1.66 | 1.52‐1.81 | <.001 | 1.63 | 1.43‐1.86 | <.001 |
| Height z‐score | 1.14 | 1.04‐1.23 | .003 | 1.15 | 1.02‐1.29 | .024 |
| Abdominal obesity | 2.59 | 2.10‐3.20 | <.001 | 1.35 | 0.96‐1.91 | .087 |
| Estimated GFR (mL/h/1.73 m2) | 0.98 | 0.98‐0.99 | <.001 | 0.99 | 0.98‐0.99 | .002 |
| Calorie intake (1000 Kcal/d) | 1.10 | 1.00‐1.21 | .052 | 0.90 | 0.76‐1.07 | .242 |
| Sodium intake (g/d) | 1.04 | 1.01‐1.07 | .017 | 1.04 | 0.99‐1.10 | .114 |
| Water intake (kg/d) | 1.19 | 1.02‐1.39 | .025 | 0.84 | 0.65‐1.08 | .177 |
| Physical activity (h/d) | 1.07 | 0.99‐1.16 | .075 | 0.94 | 0.85‐1.05 | .289 |
| HTN (BP > 95th percentile) | ||||||
| Survey period | ||||||
| 2007‐2009 | 1 (Base) | 1 (Base) | ||||
| 2010‐2012 | 1.20 | 0.92‐1.57 | .177 | 1.23 | 0.87‐1.76 | .240 |
| 2013‐2015 | 1.33 | 1.04‐1.72 | .024 | 1.17 | 0.81‐1.69 | .393 |
| Sex | ||||||
| Female | 1 (Base) | 1 (Base) | ||||
| Male | 1.91 | 1.53‐2.38 | <.001 | 0.48 | 0.34‐0.69 | <.001 |
| Age (years) | 1.09 | 1.04‐1.14 | <.001 | 1.22 | 1.11‐1.33 | <.001 |
| BMI z‐score | 1.51 | 1.34‐1.71 | <.001 | 1.48 | 1.24‐1.76 | <.001 |
| Height z‐score | 1.01 | 0.90‐1.12 | .890 | 1.06 | 0.91‐1.25 | .483 |
| Abdominal obesity | 2.56 | 1.95‐3.36 | <.001 | 1.66 | 1.06‐2.60 | .025 |
| Estimated GFR (mL/h/1.73 m2) | 0.98 | 0.97‐0.99 | <.001 | 0.98 | 0.97‐0.99 | .009 |
| Calorie intake (1000 Kcal/d) | 0.99 | 0.88‐1.12 | .908 | 0.90 | 0.70‐1.15 | .399 |
| Sodium intake (g/d) | 1.00 | 0.96‐1.04 | .986 | 0.99 | 0.92‐1.06 | .769 |
| Water intake (kg/d) | 1.01 | 0.83‐1.23 | .909 | 0.87 | 0.70‐1.38 | .914 |
| Physical activity (hr/d) | 1.02 | 0.92‐1.14 | .707 | 0.91 | 0.78‐1.07 | .248 |
Abbreviation: BMI, body mass index; BP, blood pressure; GFR, glomerular filtration rate.
P values for models of elevated blood pressure and hypertension were all <0.001.
4. DISCUSSION
In the current study, we observed secular increases in SBP levels and prevalence of elevated BP and hypertension in Korean children and adolescents from 2007‐2009 to 2013‐2015. The average differences in mean SBP between 2007‐2009 and 2013‐2015 were 3.9, 4.2, and 3.8 mm Hg in total, male, and female participants, respectively. These increases might contribute to shift the proportion of elevated BP and hypertension upwards. In comparison with other studies, country‐specific secular trends in BP and hypertension in children have been reported to be inconsistent since 2000. Xi et al reported that, according to NHANES data, mean BP levels among US children and adolescents declined from 1999‐2002 to 2009‐2012, and the average differences in mean SBP and DBP were 0.7 and 4.2 mm Hg, respectively.4 The prevalence of elevated BP and high BP also reportedly decreased from 1999‐2002 to 2009‐2012, and in 2009‐2012, the prevalence rates of elevated BP and high BP were 9.6% and 1.6%, respectively.4 In our study, the prevalence rates of elevated BP and hypertension were 8.8% and 9.0%, respectively, and the prevalence of hypertension was higher than US levels. The other US study reported that the prevalence of high BP remained stable between 1999‐2000 and 2011‐2012 although dyslipidemia rates decreased during the same period.12 Khang et al reported that SBP and hypertension substantially decreased among Korean childhood 10‐19 years of age between 1998 and 2008 in the KNHANES, a change that could not be explained by concomitant secular changes in obesity, diet, health behaviors, and sociodemographic factors.5 In the KNHANES data, the age‐standardized prevalence of hypertension decreased significantly in both sexes in Korean adults.13 However, our study results were not consistent with US data and previous Korean data. In contrast, an upward trend in BP levels and prevalence of elevated BP were also found in China. According to the nationally representative cross‐sectional surveys of Chinese children and adolescents aged 7‐17 years in 2005 and 2010, an increase in mean SBP and DBP in the total population was associated with rising BMIs.14 Recently, Dong et al reported that the prevalence of overweight increased from 4.3% in 1995 to 18.4% in 2014, whereas high BP prevalence fluctuated in the range of 4.4% to 6.4% during the same time period.15 The prevalence of obesity‐associated hypertension has been expected to increase in East Asia.14, 15
In our study, elevated BP and hypertension were classified based on the new 2017 AAP Guidelines. In Korea, reference data of BP were available, although it was based on the BP data measured using oscillometric method from children and adolescents including normal weight, overweight, and obesity.16 According to a previous report, elevated BP and hypertension rates among children increased with the new 2017 guidelines, and children whose BP was reclassified upward were more likely to be overweight or obese.17 This explanation could apply to our study. The new guidelines were developed using a reference population that excluded children with a BMI z‐score >1.18 The old guidelines could underestimate high‐risk children with cardiovascular risk. Flechtner‐Mors et al reported that a diagnosis of elevated BP in overweight or obese pediatric patients depends on the reference population used, and a non‐overweight reference population substantially increases the prevalence of hypertension in children and adolescents who are overweight and obese.19 In our study, the increase in the prevalence of hypertension in 2013‐2015 may have been influenced by the reference, which is based on non‐overweight children. Obesity in childhood and adolescents is increasing in Korea, and these children have cardiovascular risk factors. The introduction of BP reference based on non‐overweight children could be helpful to detect the high‐risk groups for cardiovascular disease early.
The risk factors for pediatric hypertension include dietary salt intake, male sex, older age, abdominal obesity, and ethnicity.20, 21 Obesity is a well‐established influencing factor of childhood hypertension.21, 22 Hagman et al reported that the prevalence of hypertension was 15.3% and 5.5% for SBP and DBP in obese children, the SBP standard deviation score (SDS) decreased 0.41, and DBP SDS decreased 0.26 per BMI SDS unit reduction.23 This study found that the effect of weight loss on BP in obese children was limited and recommended considering additional pharmacological treatment. Zhang et al reported that Chinese children and adolescents with a high BMI and high WC may be at increased risk of elevated BP, and these results suggest that measurement of BMI and WC could help identify those at risk of high BP.24 According to a national survey of Australian children, 12.6% of children had hypertension or high‐normal BP, and BMI is the most important predictor of BP.25 In the present study, abdominal obesity increased from 2007‐2009 to 2013‐2015 in males, but not in females, which was associated with hypertension after adjusting confounding variables. Our results for obesity as a risk factor are compatible with previous studies and suggest that a public education campaign to prevent excessive weight gain in children and adolescents should be considered.
In our study, obesity could not solely explain all the changes in BP because of the increase in prevalence of elevated BP and hypertension in both obese and non‐obese groups and the stable proportion of overweight and obese population in these periods. Additionally, SBP has increased in both sexes although BMI z‐score has increased only in females. The analysis to find the associative variables for BP change was performed, and lower estimated GFR was associated with elevated BP and hypertension in the present study. Previously, there was a report that prehypertension and hypertension are independent predictors of decreased GFR in the general population, especially in the elderly.26 Our results suggest that the implications of previous research may be applicable to pediatric population. In our study, no association was found between hypertension and salt intake. However, salt intake is reportedly important to childhood BP change and it is associated not with DBP, but SBP.20 In our study, sodium intake was higher than that in US children and adolescents.4 According to NHANES data, sodium intake in 2009‐2012 was 3353.6 mg/d whereas the intake of Korean children and adolescents was 4226 mg/d in 2010‐2012.4 The relatively high intake of sodium may influence BP in Korean children. For dietary factors, higher intake of total saturated fatty acids is reportedly associated with higher SBP and DBP in adults.27 In our study, total fat intake has increased, and there is a possibility that the proportion of saturated fat in total fat intake increased. Kim et al reported that dietary carbohydrate quality was associated with the prevalence of hypertension among Korean adults using data from the 5th KNHANES.28 More detailed data collection and subsequent analysis of dietary risk factors are necessary in children and adolescents.
Children with hypertension are more likely to develop hypertension during adulthood, and the early identification of hypertension in children and adolescents is important. Diagnosing hypertension based on a BP reference using age‐, sex‐, and height‐ specific criteria is complex, and the necessity for simpler diagnostic criteria has been addressed. Xi et al reported that diagnostic criteria of hypertension using BP‐to‐height ratios in US children and adolescents can help screen for elevated BP.29 Further efforts to develop simple diagnostic criteria for Korean children and adolescents are necessary, because BP measurement is not the routine procedure in general pediatric clinics.
Our study has several limitations. First, we used average BP levels in a single visit to represent BP values, and it is possible the prevalence of elevated BP may have been overestimated. Instead, a single child with elevated BP should be visited 3 times for confirmation. Second, the 24‐hour recall questionnaire used to collect dietary information did not capture long‐term dietary patterns. Third, the new reference of American Academy of Pediatrics was made from data of normal weight children and adolescents, which might affect the prevalence of hypertension over the time period. However, this study was strengthened by the application of a widely used up‐to‐date reference, which would enable an international comparison of prevalence of elevated BP and hypertension.
5. CONCLUSION
During our study period, mean systolic BP increased, and the prevalence of hypertension in 2013‐2015 increased in the total population, particularly among boys and obese children. Blood pressure and prevalence of hypertension might be different by country and ethnicity, and the public health policy based on of the nationally representative data might be helpful to prevent the cardiovascular disease. Considering the fact that the obese children and adolescents have been increasing in Korea, it is necessary to detect the high‐risk group early using BP normative data that excludes overweight and obese children.
CONFLICT OF INTEREST
The authors declare that they have no conflict of interest.
AUTHOR CONTRIBUTIONS
HC and JHK conceptualized, designed the study, and revised the manuscript; HC contributed to the analysis and drafted the manuscript; JHK collected the data and performed the analysis. All authors read and approved the manuscript.
Cho H, Kim JH. Secular trends in hypertension and elevated blood pressure among Korean children and adolescents in the Korea National Health and Nutrition Examination Survey 2007‐2015. J Clin Hypertens. 2020;22:590–597. 10.1111/jch.13842
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