THE PREVALENCE OF ELEVATED BLOOD PRESSURE IN A SAMPLE 
OF SLOVENE CHILDREN AND ADOLESCENTS: A PILOT STUDY
Tjaša HERTIŠ1, Tadej PETEK1, Nataša MARČUN VARDA2*
1University of Maribor, Faculty of Medicine, Taborska ul. 8, 2000 Maribor, Slovenia
2University Medical Centre Maribor, Department of Pediatrics, Ljubljanska ul. 5, 2000 Maribor, Slovenia
Received: Nov 19, 2016
Accepted: Jan 18, 2018
Original scientific article
Introduction: The aim of our study was to determine the prevalence of prehypertensive and elevated blood 
pressure in the hypertensive range (elevated BP) and obtain some anthropometric measures in Slovene children 
and adolescents.
Methods: In the cross-sectional study lasting one year, we measured BP using mercury sphygmomanometers, 
as well as height, weight, waist, and hip circumferences in schools. Data from regular check-ups (oscillometric 
measurements) were also added to increase the sample size. Participants were 2-19 years old. For statistical 
analysis, we used two-sided multivariate analysis of variance, Pearson’s r, and chi-squared test.
Results: From altogether 1594 participants, 723 (45.4%) were boys and 871 (54.6%) girls. The prevalence of 
elevated BP on a single oscillometric blood-pressure measurement was 12.0% (95% CI: 10.3 to 13.9), and an 
additional 13.9% (95% CI: 12.0 to 15.9) had prehypertensive BP. In Riva-Rocci measurements, elevated BP was 
present in only 7.1% (95% CI: 4.9 to 10.1) and prehypertensive BP additionally in 3.9% (95% CI: 2.4 to 6.4) 
in comparison to oscillometric measurements, which showed higher prevalence. Importantly, overweight 
participants had a 1.75 times greater relative risk for prehypertensive BP (95% CI: 1.22 to 2.53; p<0.01). Obesity 
carried a 1.79 times greater relative risk (95% CI: 1.22 to 2.63; p<0.01) for BP outside of the normotensive BP 
range.
Conclusion: Arterial hypertension is becoming an important public health problem, especially due to the 
childhood obesity. It seems to concern also Slovene young population with prevalence of elevated BP at around 
7.1% after a single auscultatory BP measurement.
Namen: Namen naše raziskave je bil ugotoviti razširjenost povišanega krvnega tlaka ter pridobiti nekatere 
antropometrične meritve slovenskih otrok in mladostnikov.
Metode: V tej presečni študiji, ki je trajala eno leto, smo merili krvni tlak (KT) z živosrebrnimi sfingomanometri 
in pridobili nekatere antropometrične meritve, kot so starost, spol, višina, teža, obseg pasu in bokov. Vzorec 
smo povečali s podatki, pridobljenimi z oscilometrično metodo s sistematskih pregledov in sprotnih pregledov 
pri pediatrih. Preiskovanci so bili stari od 2 do 19 let. Rezultate smo nato še statistično obdelali z dvosmerno 
multivariatno analizo variance. Izračunali smo tudi Pearsonov korelacijski koeficient r in naredili preizkus hi-
kvadrat.
Rezultati: Skupno je sodelovalo 1594 otrok in mladostnikov, od tega 723 (45,4 %) fantov in 871 (54,6 %) deklet. 
Pri enkratni oscilometrični meritvi KT je razširjenost visokega KT znašala 12,0 % (95 % IZ: 10,3 do 13,9) in 
prehipertenzivnega KT kar 13,9 % (95 % IZ: 12,0 do 15,9). Meritve krvnega tlaka z avskultatorno metodo so 
pokazale nižje vrednosti; povišan KT je imelo 7,1 % (95 % IZ: 4,9 do 10,1) in prehipertenzivni KT dodatno 
3,9 % (95 % IZ: 2,4 do 6,4) osnovnošolskih otrok in mladostnikov. Prekomerna telesna teža je v primerjavi z 
normalno pomenila 1,75-krat večje relativno tveganje za prisotnost prehipertenzivnega KT (95 % IZ: 1,22 do 
2,53; p<0,01). Debelost je v primerjavi z normalno telesno težo pomenila 1,79-krat večje tveganje za KT izven 
normotenzivnega območja (95 % IZ: 1,22 do 2,63; p<0,01).
Zaključek: Arterijska hipertenzija postaja pomemben javnozdravstveni problem, zlasti zaradi debelosti otrok 
in mladostnikov. Zdi se, da to zadeva tudi slovensko pediatrično populacijo, saj znaša razširjenost visokega KT 
med otroki in mladostniki 7,1 % ob enkratni meritvi z avskultatorno metodo.
ABSTRACT
Keywords: 
hypertension, 
prevalence, children, 
adolescents, Slovenia, 
antropometrics 
IZVLEČEK
Ključne besede: 
hipertenzija, 
prevalenca, otroci, 
mladostniki, 
Slovenija, 
antropometrija
*Corresponding author: Tel. + 386 2 321 24 65; E-mail:  natasa.marcunvarda@amis.net
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
PREVALENCA VISOKEGA KRVNEGA TLAKA NA VZORCU SLOVENSKIH 
OTROK IN MLADOSTNIKOV: PILOTNA ŠTUDIJA
Hertiš T, Petek T, Marčun Varda N. Prevalence of elevated blood pressure in a sample of Slovene children and adolescents: a pilot study. 
Zdr Varst. 2018;57(2):72-80. doi: 10.2478/sjph-2018-0010.
72
© Nacionalni inštitut za javno zdravje, Slovenija. 
1 INTRODUCTION
Elevated blood pressure (BP) in children and adolescents 
is becoming a public health concern. The increasing 
prevalence of arterial hypertension (HTN) is observed 
worldwide (1, 2) and relates to the epidemic of obesity 
(3, 4), among other factors.
According to the 2016 European Society of Hypertension 
guidelines (5), unlike the previously used guidelines (6), 
high BP is defined differently in children and adolescents 
aged ≥16 years. Normal BP in children is defined as a 
systolic and diastolic BP, which is less than the 90th 
percentile, adjusted for gender, age, and height. Children 
with an average systolic blood pressure (SBP) or diastolic 
blood pressure (DBP) in the 90th or higher percentile, but 
less than the 95th percentile, are prehypertensive. HTN 
in children is defined as an average SBP and/or DBP, which 
is in the 95th or higher percentile, measured on at least 
three different occasions and confirmed by auscultatory 
measurement. The first stage of HTN is defined as the 95th 
to 99th percentile BP plus 5 mmHg and the second stage 
of hypertension as BP greater than 99th percentile plus 5 
mmHg. Isolated systolic hypertension (ISH) is defined by 
SBP ≥95th percentile and DBP <90th percentile (5).
In adolescents aged ≥16 years, normotension is defined 
as a BP <130/85 mmHg. With repeated measures, a BP 
of 130-139/85-89 mmHg defines prehypertension, and a 
BP value ≥140/90 mmHg defines HTN. The first stage of 
HTN in older adolescents is defined as BP 140-159/90-99 
mmHg, and second stage as BP 160-179/100-109 mmHg. 
ISH is defined as BP ≥140/<90 mmHg (5).
Most studies report the prevalence of prehypertension 
around 9–12% (4). On single BP measurement, an American 
study (7) estimated the prevalence of HTN (here described 
as ‘elevated BP’ if <3 measurements were carried out 
with readings in the hypertensive range) in adolescents 
at approximately 10%, the same applies to single-
measurement prevalence of prehypertensive BP. After 
three BP measurements, the prevalence of HTN decreased 
to 3.2%, while the prevalence of prehypertension 
increased to 15.7%, as some of the previous hypertensive 
individuals dropped to the prehypertensive group. In a 
Swiss study (8), the prevalence of prehypertension was 
13.3% and elevated BP 11.4% at the first measurement, 
and after the second, 9.5% and 9.4%, respectively. At the 
third measurement, the prevalence of prehypertension 
was 2.2% and HTN 1.7%. Those results are similar to a 
Slovene paediatric study (1978–1990), which estimated 
the prevalence of HTN at 1.2% (9, 10).
Since then, there has been a lack of research on this topic 
in Slovenia. With this pilot study, we want to contribute 
new data on the estimated prevalence of prehypertensive 
BP and elevated BP. Additionally, we also search for some 
anthropometric features that correlate with elevated BP, 
such as increased body mass index (BMI).
2 METHODS
2.1 Design and Background
This pilot study was conducted under the supervision 
of the Unit for Paediatric nephrology and hypertension, 
University Medical Centre Maribor, Slovenia. In December 
2014, this cross-sectional study received the approval of 
the Ethics Committee of the University Medical Centre 
Maribor. Before starting data collection, we obtained all 
necessary consents. The data collection was completed in 
March 2016. 
2.2 Sampling 
Participants were aged 2–19. From December 2014, we 
began our cooperation with the Health Centre Adolf 
Drolc in Maribor and with the Paediatric Clinic in Lenart. 
There we collected BP data and certain anthropometric 
measurements from regular check-ups, measured with 
an automatic (oscillometric) device during February 
2015 and March 2016. Children with a previously known 
diagnosis of secondary (but not essential) hypertension 
were excluded, as they had aetiology-based treatment 
and their small count would not influence the overall 
results.
Meanwhile, we began to cooperate with two nearby 
schools. There, we measured BP once a month with a 
mercury sphygmomanometer (auscultatory method) and 
gathered additional data on weight, height, hip and 
waist circumferences. The sampling procedure for the 
auscultatory and oscillometric measurements is described 
in Figure 1.
2.3 Procedure
Measurements in primary schools were carried out by two 
6th year medical students, previously trained recording 
paediatric BP using a mercury sphygmomanometer. 
Height, weight, waist, and hip circumferences were also 
measured. Before each measurement, we explained the 
procedure, took a brief history on possible elevated BP 
and asked about children’s experience with BP measuring. 
We waited for anxious children to relax. Participants 
were also not allowed to be physically active before the 
examination, if so, we waited for at least five minutes. 
Children entered the quit room in pairs. As one of two 
examiners was measuring the BP of one of the two 
children, the other examiner obtained anthropometric 
measurements. BP was first measured on the right upper 
arm in the seated position. In the case of increased 
BP (≥90. p.), we obtained a second right upper arm BP 
measurement, followed by a third measurement by 
the other examiner for cross-checking, and a fourth 
measurement on the left upper arm for evaluation of 
possible aortic coarctation, with three-minute intervals 
in between. Three right upper arm measurements were 
used for later analysis.
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
73
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
74
The sample was increased using patient records from 
systematic check-ups. There, repeated BP measurements 
on the upper right arm were taken by Health Centre staff, 
using an Omron M6 oscillometric upper arm blood pressure 
monitor. In addition, data on gender, height, weight, and 
BMI were collected.
Figure 1. Sampling procedure of study participants. 
After collecting the data, we calculated average values 
of SBP and DBP, and calculated mean arterial pressures 
(MAP). Using height and weight data, we calculated the 
BMI and BMI standard deviation scores (SDS).
Anthropometric measurements served us to calculate the 
waist-to-hip and waist-to-height ratios. In accordance 
with recommendations (5), we calculated percentiles of 
arterial BP based on sex, age and height. More about this 
calculation is found in the 4th Report (Supplement) of 
the NHBPEP Working Group on Children and Adolescents 
(6). Since this was a study on the Slovenian children, we 
decided to use the WHO and CDC growth curves (11–13) 
to calculate SDS scores of anthropometric parameters 
(weight-for-age, height-for-age, BMI-for-age). We used 
the European (ages 2–11) and Japanese (ages 12–19) data 
to calculate waist circumference SDS scores (14, 15). 
Children and adolescents were classified into four groups 
based on their BMI percentile: underweight, normal weight 
status, overweight and obese. The participants were also 
allocated to different groups dependent on their height, 
waist, and hip circumferences. When the waist-to-hip 
circumference ratio exceeded 0.85 for girls or 0.9 for 
boys, it was regarded as increased (16). Waist-to-height 
ratio was defined as increased when it exceeded 0.5 (17).
2.4 Statistical Methods and Sample Size
We used IBM SPSS statistical program (version 20), running 
on a PC with Windows 10 operating system. To calculate the 
independence of the distributions of categorical variables, 
we used the chi-square test. Pearson’s correlation 
coefficient r was used in the calculation of correlations 
between the SDS score of systolic and diastolic BP and 
certain anthropometric parameter SDS scores.
The sample size was assessed via an online statistical 
program (18), using an expected hypertension prevalence 
(10%) and the desired confidence interval width of 
95%±2%. Based on this, the recommended sample size was 
912 participants.
3 RESULTS
3.1 Sample Characteristics and Epidemiology
A total of 1,594 children and adolescents have been 
included, 723 (45.4%) boys and 871 (54.6%) girls. The 
participants from two schools (N=382) were aged 6–15, 
with an average age of 9.78 years (SD=2.7). The age of 
children and adolescents from regular check-ups (N=1212) 
was 2–19 years, with an average age of 11.2 years (SD=4.9).
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
75
3.2 The Prevalence of Prehypertensive and Elevated 
Blood Pressure in Hypertensive Range
The prevalence of elevated BP after a single Riva-Rocci 
auscultatory measurement in schools was 7.1% (95% CI: 
4.9 to 10.1), and the prevalence of elevated BP at regular 
check-ups, measured with automatic oscillometric 
device, was approximately 12.0% (95% CI: 10.3 to 13.9). 
Furthermore, the prevalence of children and adolescents 
with BP in stage 1 hypertensive range, using auscultatory 
measurement, was 1.6% (95% CI: 0.7 to 3.4), and in 
stage 2 hypertensive range, 1.0% (95% CI: 0.4 to 2.7). In 
oscillometric measurements, stage 1 hypertensive range 
BP was observed in 6.5% (95% CI: 5.3 to 8.0), and stage 2 
hypertensive range BP in 1.1% (95% CI: 0.6 to 1.8). 
Table 1. Mean values of sample characteristics.
N - number of participants; SD - standard distribution; SDS - standard distribution (Z) score; SBP - systolic blood pressure; DBP - diastolic blood 
pressure; MAP - mean arterial pressure; BMI - body mass index; WC - waist circumference; HC - hip circumference; NA - data not available
Age
Gender - 
N (Male: Female)
SBP [mmHg]
DBP [mmHg]
MAP [mmHg]
Height [SDS]
Weight [SDS]
BMI [SDS]
WC [SDS]
HC [cm]
Waist-to-hip ratio 
Waist-to-height ratio 
6.0 
(0.0; 46)
46 
(25: 21)
100.4 
(7.5; 46)
57.0 
(8.1; 46)
71.5 
(7.2; 46)
1.45 
(0.84; 46)
0.53 
(0.81; 46)
-0.05 
(0.82;46)
1.41 
(1.89; 46)
69.1 
(6.3; 46)
0.87 
(0.06; 46)
0.48 
(0.06; 46)
9.2 
(1.6; 253)
253 
(119 : 134)
100.9 
(12.0; 253)
55.1 
(9.2; 253)
70.4
(9.0; 253)
0.79
(1.00; 253)
0.51
 (1.01; 253)
0.16 
(0.74; 253)
0.48 
(1.63; 253)
78-4 
(9.4; 253)
0.83 
(0.07; 253)
0.46
 (0.06; 253)
13.7 
(0.7; 83)
83
 (35: 48)
114.4 
(11.5; 83)
64.2 
(11.7; 83)
81.0 
(10.1; 83)
0.32 
(1.20; 83)
0.56 
(1.27; 83)
0.09 
(0.52; 83)
0.04 
(1.61; 83)
92.3 
(8.67; 83)
0.80 
(0.08; 83)
0.45 
(0.06; 83)
4.8 
(1.2; 303)
303 
(144: 159)
98.9 
(10.2; 427)
62.3 
(8.8; 427)
74.5 
(8.0; 427)
-0.57 
(1.23; 233)
0.10 
(1.64; 233)
0.34 
(0.86; 233)
0.54 
(1.58; 77)
NA
NA
0.51 
(0.05; 76)
8.8 
(1.9; 319)
319 
(163: 156)
109.6 
(10.7; 319)
66.7 
(9.5; 319)
81.0
 (9.5; 319)
0.43 
(1.44; 196)
0.79 
(1.36; 196)
0.40 
(0.81; 196)
0.56 
(1.90; 81)
NA
NA
0.49 
(0.07; 79)
15.7 
(1.8; 590)
540 
(237: 353)
119.4 
(11.7;590)
72.1 
(8.8; 590)
87.8 
(8.4; 590)
0.61 
(0.98; 469)
0.94 
(1.40; 469)
0.27 
(0.58; 469)
1.00 
(1.97; 33)
NA
NA
0.49 
(0.07; 32)
5.0 
(1.2; 349)
349 
(169: 180)
99.1 
(9.9; 349)
61.6 
(8.9; 349)
74.13 
(8.0; 349)
-0.21 
(1.40; 257)
0.18 
(1.53; 257)
0.27 
(0.86; 257)
0.93 
(1.77;104)
69.1 
(6.3; 46)
0.87 
(0.06; 46)
0.48 
(0.06 ;46)
9.0 
(1.8; 572)
572 
(282: 290)
105.8 
(12.1; 572)
61.6 
(11.0; 572)
76.3 
(10.2; 572)
0.63 
(1.22; 449)
0.63 
(1.18; 449)
0.27 
(0.78; 449)
0.50 
(1.70; 334)
78.4 
(9.4; 253)
0.83 
(0.07; 253)
0.47 
(0.06; 332)
15.5 
(1.8; 673)
673 
(272: 401)
118.8 
(11.8; 673)
71.1 
(9.5; 673)
87.0 
(8.9; 673)
0.56 
(1.02; 552)
0.88 
(1.39; 552)
0.21 
(0.57; 552)
0.31 
(1.77; 116)
92.3 
(8.7; 83)
0.80 
(0.08; 83)
0.46 
(0.07; 115)
Characteristic 2-6 years 2-6 years 2-6 years7-12 years 7-12 years 7-12 years13-19 years 13-19 years 13-19 years
Auscultatory measurements - 
Mean (SD; N)
Oscillometric measurements - 
Mean (SD; N)
All measurements - 
Mean (SD; N)
The prevalence of prehypertensive BP in children and 
adolescents after auscultatory measurement was at 3.9% 
(95% CI: 2.4 to 6.4), and majorly different in oscillometric 
measurements, that is, 13.9% (95% CI: 12.0 to 15.9). 
Regarding ISH, it was prevalent in 4.5% (95% CI: 2.8 to 7.0) 
of cases with auscultatory measurements and 4.5% (95% 
CI: 3.4 to 5.8) of cases with oscillometric measurements. 
For more details on normotension, prehypertensive BP, 
elevated BP, stage 1 and stage 2 hypertensive range BP, 
and isolated systolic hypertension prevalence at different 
ages, see Table 2.
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
76
 3.3 The Influence of Anthropometric Characteristics 
on Blood Pressure Values
Relative Risks
For each pair of variables (anthropometric characteristic, 
blood pressure category), the relative risk with confidence 
intervals and chi-square test were calculated (Table 3).
Focusing on auscultatory measurements, which show a 
more complete set of data, it is seen that children aged 
7–12 years and adolescents aged 13–19 years have 1.10 
times (95% CI: 1.01 to 1.19; p<0.05) greater and 0.82 
times (95% CI: 0.72 to 0.93, p<0.01) smaller relative 
risk for being normotensive in comparison to the rest of 
participants, respectively. Interestingly, not any of the 
three age groups has an increased relative risk for having 
prehypertensive or elevated BP.
The relative risk for being prehypertensive (1.23; 95%CI: 
0.48 to 3.50) or having elevated BP (1.13 95% CI: 0.63 to 
2.04) for boys was not significantly different in comparison 
to girls in the auscultatory measurement group.
Table 2. Blood pressure categories by the participants’ age.
N - number of cases; ISH - isolated systolic hypertension; NA - data not available; N - number of cases; ‡ Due to BP measurement on a single 
occasion, the term hypertension is used as a synonym with “elevated BP in the hypertensive range”
Normal
Prehypertensive BP
Hypertension‡
Stage 1 Hypertension‡
Stage 2 Hypertension‡
ISH‡
Normal
Prehypertensive BP
Hypertension‡
Stage 1 Hypertension‡
Stage 2 Hypertension‡
ISH‡
Normal
Prehypertensive BP
Hypertension‡
Stage 1 Hypertension‡
Stage 2 Hypertension‡
ISH‡
Auscultatory measurements - N (%)
Oscillometric measurements - N (%)
All measurements - N (%)
NA
NA
NA
NA
NA
NA
38 (48.7%)
13 (16.7%)
27 (34.6%)
25 (32.1%)
2 (2.6%)
0 (0.0%)
38 (48.7%)
13 (16.7%)
27 (34.6%)
25 (32.1%)
2 (2.6%)
0 (0.0%)
NA
NA
NA
NA
NA
NA
70 (70.7%)
18 (18.2%)
11 (11.1%)
6 (6.1%)
1 (1.0%)
4 (4.0%)
70 (70.7%)
18 (18.2%)
11 (11.1%)
6 (6.1%)
1 (1.0%)
4 (4.0%)
91 (96.8%)
2 (2.1%)
1 (1.1%)
1 (1.1%)
0 (0.0%)
0 (0.0%)
30 (53.6%)
13 (23.2%)
13 (23.2%)
8 (14.3%)
1 (1.8%)
4 (7.1%)
121 (80.7%)
15 (10.0%)
14 (9.3%)
9 (6.0%)
1 (0.6%)
4 (2.7%)
92 (91.1%)
4 (4.0%)
5 (5.0%)
0 (0.0%)
0 (0.0%)
5 (5.0%)
25 (45.5%)
10 (18.2%)
20 (36.4%)
11 (20.0%)
2 (3.6%)
7 (12.7%)
117 (75.0%)
14 (9.0%)
25 (16.0%)
11 (7.1%)
2 (1.3%)
12 (7.7%)
69 (93.2%)
1 (1.4%)
4 (5.4%)
1 (1.4%)
0 (0.0%)
3 (4.1%)
60 (71.4%)
9 (10.7%)
15 (17.9%)
4 (4.8%)
1 (1.2%)
10 (11.9%)
129 (81.6%)
10 (6.3%)
19 (12.0%)
5 (3.2%)
1 (0.6%)
13 (8.2%)
51 (77.3%)
4 (6.1%)
11 (16.7%)
2 (3.0%)
4 (6.1%)
5 (7.6%)
125 (77.2%)
20 (12.3%)
17 (10.5%)
3 (1.9%)
1 (0.6%)
13 (8.0%)
176 (77.2%)
24 (10.5%)
28 (12.3%)
5 (2.2%)
5 (2.2%)
18 (7.9%)
37 (78.7%)
4 (8.5%)
6 (12.8%)
2 (4.3%)
0 (0.0%)
4 (8.5%)
88 (73.9%)
13 (10.9%)
18 (15.1%)
8 (6.7%)
4 (3.4%)
6 (5.0%)
125 (75.3%)
17 (10.2%)
24 (14.5%)
10 (6.0%)
4 (2.4%)
10 (6.0%)
NA
NA
NA
NA
NA
NA
187 (74.2%)
52 (20.6%)
13 (5.2%)
7 (2.7%)
1 (0.4%)
5 (2.0%)
187 (74.2%)
52 (20.6%)
13 (5.2%)
7 (2.7%)
1 (0.4%)
5 (2.0%)
NA
NA
NA
NA
NA
NA
60 (65.9%)
20 (22.0%)
11 (12.1%)
7 (7.7%)
0 (0.0%)
4 (4.4%)
60 (65.9%)
20 (22.0%)
11 (12.1%)
7 (7.7%)
0 (0.0%)
4 (4.4%)
Characteristic
2-3 
years
8-9 
years
14-15 
years
4-5 
years
10-11 
years
16-17 
years
6-7 
years
12-13 
years
18-19 
years
Participant count - N (%)
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77
Table 3. Blood pressure categories by the relative risks for having normotensive, prehypertensive or hypertensive BP in correlation with 
some participants’ characteristics, e.g. participants’ age.
RR - relative risk; CI - confidence interval; NA - comparison not possible due to too few cases in the 2x2 contingency table; 
* - p<0.05 using chi-square test; ** - p<0.01 using chi-square test
Age
• 2-6 years: rest 
• 7-12 years: rest 
• 13-19 years: rest 
Gender  
(male: female)
Waist-to-hip ratio 
(increased: normal) 
Waist-to-height ratio 
(increased: normal)
Body mass index
overweight: normal
obese: normal
1.11 
(1.05;1.18)*
1.10 
(1.01; 1.19)*
0.82 
(0.72; 0.93)**
0.96 
(0.92; 1.06)
1.03 
(0.94; 1.12)
1-23 
(1.08; 1.40)**
0.67 
(0.52; 0.88)**
0.95 
(0.73; 1.24)
NA
1.02 
(0.36; 2.92)
1.80 
(0.63; 5.13)
1.23 
(0.48; 3.50)
0.80 
(0.26; 2.45)
0.51 
(0.18; 1.43)
6.67 
(2.53; 17.60)**
NA
0.81
(0.30; 2.18)
1.06 
(0.57; 1.98)
1.05 
(0.52; 2.11)
1.13 
(0.63; 2.04)
2.03 
(0.82; 5.03)
1.77 
(0.72; 4.36)
1.37 
(0.22; 8.62)
1.12 
(0.18; 7.17)
0.66 
(0.48; 0.90)**
0.88 
(0.78; 0.99)*
1.20 
(1.09; 1.31)**
0.81 
(0.74; 0.88)**
NA
1.23 
(0.90; 1.68)
0.79 
(0.66; 0.95)**
0.43 
(0.24; 0.76)**
0.98 
(0.70; 1.38)
0.93 
(0.65; 1.32)
1.06 
(0.80; 1.41)
1.71 
(1.30;2.26)**
NA
1.28 
(0.72; 2.29)
1.37 
(0.92; 2.05)
1.36 
(0.66; 2.80)
0.96 
(0.66; 1.38)
1.50 
(1.06; 2.12)*
0.77 
(0.56; 1.06)
1.36 
(0.99; 1.87)
NA
1.43 
(0.73; 2.79)
1.16 
(0.71; 1.89)
0.78 
(0.27; 2.29)
0.89 
(0.82; 0.98)**
1.09 
(1.03; 1.16)**
0.99 
(0.93; 1.05)
0.87 
(0.82; 0.93)**
1.03 
(0.94; 1.12)
1.37 
(1.20; 1.57)**
0.74 
(0.64; 0.86)**
0.56 
(0.38; 0.82)**
1.04 
(0.70; 1.54)
0.60 
(0.43; 0.83)**
1.48 
(1.12; 1.94)**
1.63 
(1.24;214)**
0.80 
(0.26; 2.45)
0.68 
(0.40; 1.14)
1.75 
(1.22; 2.53)**
1.42 
(0.67; 2.99)
0.98 
(0.70; 1.38)
1.15 
(0.86; 1.54)
0.89 
(0.67; 1.18)
1.29 
(0.98; 1.71)
2.03 
(0.82; 5.03)
1.20 
(0.70; 2.05)
0.97 
(0.60; 1.57)
0.87 
(0.34; 2.21)
Characteristic
Normoten-
sive
Normoten-
sive
Normoten-
sive
Pre-
hyper-
tensive
Pre-
hyper-
tensive
Pre-
hyper-
tensive
Hyper-
tensive
Hyper-
tensive
Hyper-
tensive
Auscultatory measurements - 
RR (95% CI)
Oscillometric measurements - 
RR (95% CI)
All measurements -
 RR (95% CI)
As expected, the frequency of hypertensive range BP was 
higher among participants with elevated BMI (overweight 
and obesity). After calculation of the chi-square value, we 
found that the relative risk for having prehypertensive BP 
was 6.67 times (95% CI: 2.53 to 17.60; p<0.001) greater 
in the overweight group, with an insufficient number of 
cases to calculate the relative risk for prehypertensive 
BP in the obese group. Interestingly, neither overweight 
nor obesity carried a significantly greater relative risk of 
elevated BP in the hypertensive range (relative risk of 
elevated BP for overweight = 1.37; 95% CI: 0.22 to 8.62 
and relative risk of elevated BP for obese = 1.12; 95% CI: 
0.18 to 7.17), but this was again most likely due to not 
enough obese (pre)hypertensive patient cases.
There was a positive correlation between increased waist-
to-hip ratio as well as waist-to-height ratio and elevated 
BP in the hypertensive range, but both were statistically 
insignificant (Table 3).
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
78
3.3.2 Pearsons’ Correlations
Some anthropometric characteristics (with continuous 
range of values) correlated with SBP and DBP SDS scores 
differently than others (Table 4).
3.3.3 Comparisons of BP SDS Score Mean Values
The initial intent was to analyse possible interactions 
between anthropometric characteristics and mean scores 
of BP percentiles using the two-way Students’ t-test, but 
no significant interactions were seen on MANOVA analysis, 
so that subsequent testing was not performed.
4 DISCUSSION
The only published study on the prevalence of HTN in 
children in Slovenia between 1978 and 1990 estimated 
the prevalence at 1.2% (9, 10). In foreign literature, the 
prevalence of elevated BP ranges from 9%–19% on a single 
measurement, and the prevalence of prehypertension 
10%–30%, which is higher than our results, with 3.9% 
prevalence of prehypertensive BP and 7.1% of elevated BP 
in hypertensive range (7, 8, 19). 
If we compare the results of the prevalence from regular 
check-ups (12.0%) and the results obtained with the 
auscultatory method (7.1%), we can see that they differ 
to a high extent. This could be explained with findings 
from research by Park et al. (20), where the values of BPs 
measured with automatic-oscillometric device were 10 
mmHg higher in systolic BPs and 5 mmHg higher in diastolic 
Table 4. Pearsons’ r correlation coefficients between sample characteristics and blood pressure SDS scores.
* p<0.05; ** p<0.01; N - number of cases; SDS - standard distribution (Z) score; NA - data not available; r - Pearson’s r correlation coefficient; 
WC - waist circumference; HC - hip circumference; BP m. - blood pressure measurements
Age [yr]
Height [SDS]
Weight [SDS]
WC (SDS)
HC (cm)
Waist-to-hip ratio
Waist-to-height ratio
Body mass index (SDS)
0.20 (382)**
0.10 (382)
0.41 (382)**
0.31 (382)**
0.43 (382)**
0.08 (382)
0.32 (382)**
0.39 (382)**
0.04 (878)
0.06 (878)
0.21 (878)*
0.35 (174)**
NA
NA
0.23 (170)**
0.23 (878)**
0.11 (1260)**
0.17 (1260)
0.26 (1260)**
0.31 (556)**
0.43 (382)**
0.08 (382)
0.35 (552)**
0.29 (1260)**
0.12 (382)*
0.07 (382)
0.31 (382)**
0.20 (382)**
0.30 (382)**
0.02 (382)
0.20 (382)**
0.26 (382)**
-0.21 (878)**
-0.07 (878)*
0.08 (878)
0.23 (174)**
NA
NA
0.20 (170)**
0.20 (878)**
-0.04 (1260)
-0.12 (1260)**
0.14 (1260)**
0.20 (556)**
0.30 (382)**
0.02 (382)
0.30 (552)**
0.24 (1260)**
Sample 
characteristic
Systolic blood 
pressure (SDS) 
Systolic blood 
pressure (SDS) 
Systolic blood 
pressure (SDS) 
Diastolic blood 
pressure (SDS) 
Diastolic blood 
pressure (SDS) 
Diastolic blood 
pressure (SDS) 
Auscultatory BP m. - r (N) Oscillometric BPm. - r (N) All BP measurements - r (N)
BPs, compared to the auscultatory method. Differences 
between settings of out-patient clinics in oscillometric 
measurements and primary school cabinets in auscultatory 
measurements could have led to some differences in BP 
values, further potentiated by the white-coat effect in 
the clinical setting. We also observed relatively large 
proportions of elevated BP readings in the young child 
group, aged 2–6 years, which were seen by primary care 
paediatricians. The reason might be a positive selection 
of patients, in which a BP measurement was indicated and 
not measured only as part of a screening protocol.
We believe that our estimate of HTN prevalence of about 
7% obtained with auscultatory measurement at one 
occasion is the most accurate. Based on these findings 
and the assumption that the prevalence of HTN is at least 
halved after the second and third measurement (7, 21), 
we presume the actual prevalence of HTN in Slovenian 
paediatric population is around 3–4%, concordant with 
results from recent foreign literature (20). 
In the second part of our analysis, we have seen that BMI is 
positively correlated to BP height, which is consistent with 
findings from several other studies (3, 4, 21). Surprisingly, 
the relative risk for HTN was not statistically increased 
with an increase in waist-to-hip ratio, as it would be 
expected (16). Foreign studies (16, 17, 22) also report 
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
79
that an increased waist-to-height ratio strongly correlates 
with a high BP, which was not observed in our study, due 
to unknown reasons, and should be further elucidated.
A major methodological issue was the difference 
between the auscultatory and oscillometric cohorts, 
which prevented us from analysing the two groups 
together. The most important limitation of our study were 
measurements of BP on a single occasion, often with a 
single measurement if below 90th percentile, and not at 
three, as it is expected (5). Single measurement studies 
(7, 8, 19) overestimate the prevalence of HTN. In at least 
two studies, the prevalence of arterial hypertension was 
more than halved after completion of the second and third 
measurements (7, 21). A limitation of our sample was 
also the absence of measurements of certain parameters 
which could correlate with HTN, such as family history 
of hypertension, race, birth weight, quality of diet, drug 
therapy and physical activity.
Our methodology risked a selection bias due to 
opportunistic sampling of children in primary schools. This 
was reduced by supplementing it with data from regular 
check-ups. Observer bias was reduced by double-checking 
the measured elevated BP by another examiner.
5 CONCLUSION
The estimated prevalence of elevated BP in hypertensive 
range in Slovenian paediatric population, measured at 
a single occasion, is around 7.1%, and prehypertensive 
BP approximately 3.9%, which is consistent with recent 
foreign studies. Moreover, a positive correlation between 
blood pressure and body mass index was shown. In other 
words, normal blood pressure appeared less often in 
overweight and obese children and adolescents. These 
findings of a pilot study give a reason to conduct a 
representative, larger-scale study on the prevalence of 
elevated BP and obesity in Slovene paediatric population, 
and, thereby, gather insight into the burden of a disease 
gaining epidemic proportions worldwide.
CONFLICTS OF INTEREST
The authors declare that no conflicts of interest exist. 
FUNDING
The study was not financed. 
ETHICAL APPROVAL
The study was granted ethical approval by the University 
Medical Centre Maribor Ethics Committee on 19 December 
2014.
REFERENCES
1. Din-Dzietham R, Liu Y, Bielo MV, Shamsa F. High blood pressure 
trends in children and adolescents in national surveys, 1963 
to 2002. Circulation. 2007;116(13):1488-96. doi: 10.1161/
CIRCULATIONAHA.106.683243.
2. Falkner B. Recent advances in pediatric hypertension. J Clin 
Hypertens (Greenwich). 2012;14(6):345. doi: 10.1111/j.1751-
7176.2012.00664.x.
3. Chiolero A, Bovet P, Paradis G, Paccaud F. Has blood pressure 
increased in children in response to the obesity epidemic? Pediatrics. 
2007;119(3):544-53. doi: 10.1542/peds.2006-2136.
4. Flynn J. The changing face of pediatric hypertension in the era of 
the childhood obesity epidemic. Pediatr Nephrol. 2013;28(7):1059-
66. doi: 10.1007/s00467-012-2344-0.
5. Lurbe E, Agabiti-Rosei E, Cruickshank JK, Dominiczak A, Erdine S, 
Hirth A, et al. 2016 European Society of Hypertension guidelines for 
the management of high blood pressure in children and adolescents. J 
Hypertens. 2016;34:1887-920. doi: 10.1097/HJH.0000000000001039.
6. National High Blood Pressure Education Program Working Group on 
High Blood Pressure in Children and Adolescents. The fourth report 
on the diagnosis, evaluation, and treatment of high blood pressure in 
children and adolescents. Pediatrics. 2004;114(Suppl 2, Rep 4):555-
76. 
7. McNiece K, Poffenbarger T. Prevalence of hypertension and pre-
hypertension among adolescents. J Pediatr. 2007;150(6);640-4. doi: 
10.1016/j.jpeds.2007.01.052.
8. Chiolero A, Paccaud F, Bovet P. Pre-hypertension and hypertension 
among adolescents of Switzerland. J Hypertens. 2007;151(6):24-5. 
doi: 10.1016/j.jpeds.2007.08.043.
9. Gregorič A, Oberiter V, Schmidt I, Adamčič M, Gulič F, Nikolić T, et al. 
Hypertension in Slovene schoolchildren population. Clin ExperTheory 
Pract. 1986;8(4-5):571-6. 
10. Gregorič A. Esencialna arterijska hipertenzija pri otrocih. Zdr Obz. 
1990;24:157-61. 
11. WHO Multicentre Growth Reference Study Group. WHO Child Growth 
Standards based on length/height, weight and age. Acta Paediatr 
Suppl. 2006;450:76-85. 
12. De Onis M, Onyango AW, Borghi E, Siyam A, Nishida C, Siekmann J. 
Development of a WHO growth reference for school-aged children 
and adolescents. Bull World Health Organ. 2007;85(9):660-7. 
13. CDC. About child & teen BMI. Accessed September 10th, 2016 at: 
http://www.cdc.gov/healthyweight/assessing/bmi/childrens_bmi/
about_childrens_bmi.html.
14. Nagy P, Kovacs E, Moreno LA, Veidebaum T, Tornaritis M, Kourides 
Y, et al. Percentile reference values for anthropometric body 
composition indices in European children from the IDEFICS study. Int 
J Obes (Lond). 2014;38(Suppl 2):S15-25. doi: 10.1038/ijo.2014.131.
15. Inokuchi M, Matsuo N, Anzo M, Takayama JI, Hasegawa T. Age-
dependent percentile for waist circumference for Japanese children 
based on the 1992-1994 cross-sectional national survey data. Eur J 
Pediatr. 2007;166:655-61. doi: 10.1007/s00431-006-0296-8.
16. World Health Organisation. Waist circumference and waist-hip 
ratio report of a WHO expert consultation. Geneva: World Health 
Organization, 2008. 
10.2478/sjph-2018-0010 Zdr Varst. 2018;57(2):72-80
80
17. McCarthy HD, Ashwell M. A study of central fatness using waist-
to-height ratios in UK children and adolescents over two decades 
supports the simple message - ’keep your waist circumference to 
less than half your height’. Int J Obes (Lond). 2006;30(6):988-92. 
doi: 10.1038/sj.ijo.0803226.
18. UCSF. Sample size calculators. Accessed September 11th, 2016 at: 
http://www.sample-size.net/sample-size-conf- interval-
proportion/.
19. Paradis G, Lambert M, O’Loughlin J, Lavallee C, Aubin J, 
Delvin E, et al. Blood pressure and adiposity in children and 
adolescents. Circulation. 2004;110(13):1832-8. doi: 10.1161/01.
CIR.0000143100.31752.B7.
20. Park MK, Menard SW, Yuan C. Comparison of ausculatory and 
oscillometric blood pressures. Arch Pediatr Adolesc Med. 
2001;155:50-3.
21. Chiolero A, Madeleine G, Gabriel A, Burnier M, Paccaud F, Bovet 
P. Prevalence of elevated blood pressure and association with 
overweight in children of a rapidly developing country. J Hum 
Hypertens. 2007;21(2):120-7. doi: 10.1038/sj.jhh.1002125.
22. Falkner B. Hypertension in children and adolescents: epidemiology 
and natural history. Pediatr Nephrol. 2010;25(7):1219-24. doi: 
10.1007/s00467-009-1200-3.