The prevalence of high blood pressure (BP) in the pediatric population has increased significantly over the past few decades. This condition, historically considered rare in childhood, has emerged as a serious public health problem closely associated with the current epidemic of childhood overweight and obesity.1,2 The clinical practice guidelines of the American Academy of Pediatrics report that approximately 3.5% of children have blood pressure readings in the hypertensive range, a proportion that increases in the presence of obesity.3 In some groups of adolescents with obesity, the prevalence of hypertension can exceed 20%,4 demonstrating the impact of excess body fat on BP control early in life and its persistence into adulthood.5 In Spain, data from the 2023 ALADINO study on nutrition, physical activity, child development, and obesity indicate that 36.1% of school-aged children are overweight, and Andalusia stands out as one of the regions with the highest percentages of childhood obesity.6 However, most studies focus solely on body mass index (BMI) as the primary indicator of body fat, even though parameters such as waist circumference, the waist-to-height ratio (WHtR), or the sum of skinfolds may be better indicators of cardiometabolic risk.7,8 In addition, recent studies have highlighted the role of lifestyle factors—physical activity, sleep, and diet—in the pathophysiology of cardiovascular disease, underscoring the need to consider their potential impact when assessing the risk of hypertension.9

The objective of our study was to analyze the association between various anthropometric indicators—including the BMI, WHtR, and body fat percentage (%BF)—and the presence of high BP, defined as BP at or above the 90th percentile (P90), in schoolchildren aged 6–15 years. The aim was to identify simple and useful parameters for assessing adiposity and screening for cardiometabolic risk in real-world pediatric practice.

Cross-sectional observational study to assess anthropometric and cardiovascular parameters in rural schoolchildren in the county of Écija (Seville, Andalusia, Spain).

All children currently enrolled in primary or compulsory secondary education between February and June 2024 at any of the five schools in the three towns included in the study (identified through the school census) were invited to participate. Children enrolled in the selected grades during the data collection period were included following the receipt of signed informed consent from their parents or legal guardians. We established exclusion criteria (chronic illness, medications that could affect blood pressure, and incomplete data), although they did not apply to any of the candidates who consented to participation. The study was approved by the Ethics Committee of the Virgen Macarena/Virgen del Rocío University Hospitals at the meeting held on December 21, 2023 (minute CEI_11/2023 from January 18, 2024). In the end, 497 of the 585 candidates (84.9%) agreed to participate, and the final sample consisted of 249 boys and 248 girls aged 6–15 years, stratified into two age groups (6−9 and 10−15 years). We recorded the biological sex (male/female) of participants, and, from this point, we will refer to participants as “boys” and “girls” in relation to this variable.

The anthropometric assessments included weight (kg), height (cm), waist circumference (cm), neck circumference (NC) (cm), and the sum of the biceps, triceps, subscapular, and suprailiac skinfold thicknesses (∑4SF) (mm). All measurements were performed by trained personnel using standardized equipment, in accordance with the protocol of the International Biological Programme.10 In particular, the neck circumference was measured with the child standing position placing a non-stretch tape measure perpendicular to the vertical axis of the neck, just below the laryngeal prominence.11 We calculated the BMI (kg/m2) and used it to categorize weight status applying the international cut-off points proposed by Cole et al.12 The WHtR was calculated by dividing the waist circumference (cm) by the height (cm) and used to classify weight status according to the cut-off points proposed by Marrodán et al., defining central adiposity based on thresholds for overweight (>0.48 for boys; >0.47 for girls) and for obesity (>0.51 for boys; >0.50 for girls).13 We estimated the %BF with the Siri equation14 after calculating the body density with the Brook equations (6–11 years)15 or the Durnin and Rahaman equations (12–16 years).16 The categorization by weight status according to the %BF was based on the reference values reported by Marrodán et al.17 for the Spanish pediatric population, with high adiposity defined as values at or above the P90 and very high adiposity as values at or above the 97th percentile (P97).

In adherence to the recommendations of the European Society of Hypertension,18 blood pressure was measured in a quiet setting by the oscillometric method with an automated sphygmomanometer validated in the pediatric population (Microlife WatchBP Office), in compliance with the ANSI/AAMI/ISO 81060-2:2013 standard. Measurements were performed using cuffs of appropriate size based on the arm circumference (ensuring that the bladder covered 80%–100% of the arm circumference and at least 40% of the arm length).19 Following the recommendations, after having the child rest for five minutes, three BP readings were taken, one minute apart, with the child in the seated position, with the back supported, legs uncrossed with feet on the ground, and the right arm supported at the level of the heart. For the analysis, we used the mean of the last two readings. Owing to the cross-sectional design of the study, which involved a single visit, these values were used to estimate prevalence and for screening purposes, as opposed to diagnostic confirmation, which would have required additional visits. Blood pressure was classified according to the age-, sex-, and height-adjusted percentile charts for the Spanish population from the RICARDIN II study.20 We defined high BP as a systolic and/or diastolic BP at or above the P90.

We have expressed quantitative variables as mean and standard deviation (SD) or median and interquartile range (IQR), depending on their distribution. We compared groups with the t-test or the Mann-Whitney U test and the χ2 test, substituting the Fisher exact test when appropriate. To compare systolic and diastolic BP in different weight status groups, we used analysis of variance (F), assessing the equality of variances with the Levene test, and the Tukey or Games-Howell post hoc tests as applicable. We assessed discriminative ability by means of receiver-operator characteristic (ROC) curves stratified by sex (calculating the area under the curve [AUC] and 95% CI) and used the Youden index to determine the optimal cut-off points. The model was calibrated internally with the Hosmer-Lemeshow test and a decile calibration plot (observed proportion vs predicted mean probability). In addition, we estimated the calibration intercept and slope from the regression of the outcome on the logit of the predicted probability. The statistical analysis was performed with the software SPSS version 31.0, with statistical significance defined as a p value of less than 0.05.

Overall, anthropometric and hemodynamic profiles were similar in both sexes, except for the NC and %BF (Table 1). Both of these variables showed sexual dimorphism, with a higher NC in boys and greater adiposity in girls, a pattern observed in all age groups under study. The overall prevalence of high BP (≥P90) was 5.8% (29 cases), with similar proportions in both sexes. Its prevalence increased with the degree of excess weight (Table 2), a pattern that was more consistent among girls. Mean systolic and diastolic blood pressure values increased parallel to excess weight (Tables 3–5). The systolic BP gradient was more consistent compared to the diastolic gradient and was generally higher in overweight and obese participants compared to their normal-weight peers. In the stratified analyses, the gradient remained consistent overall, although statistical significance varied depending on the adiposity indicator and the age/sex subgroup (Tables 3–5).

The Pearson correlation coefficients showed positive and significant correlations between blood pressure and all anthropometric variables (all with P <  .001). The coefficients (r for SBP/r for DBP), in order of decreasing SBP strength of correlation, were: weight, 0.678/0.539; height, 0.661/0.518; NC 0.654/0.527; waist circumference, 0.549/0.457; BMI 0.510/0.415; ∑4SF, 0.409/0.332; %BF, 0.389/0.309; WHtR, 0.229/0.211. Given the strong correlations between anthropometric indicators, we fitted separate multivariate models to minimize collinearity issues.

In the multivariable logistic regression models adjusted for age and sex (Table 6), all of which included NC, the NC was the marker that exhibited the most consistent association with high BP, while the specific adiposity indicators (BMI, WHtR, ∑4SF, and %BF) were no longer significant after adjustment. The WHtR was rescaled as WHtR × 100 (original scale OR, 0.01).

In the assessment of discriminative ability (Fig. 1), we found areas under the curve (AUCs) for the NC of 0.700 in boys (95% CI, 0.575−0.824) and 0.936 in girls (95% CI, 0.892−0.979). The optimal cut-off points (Youden) were 29.15 and 30.65 cm, with sensitivities of 81.3% and 92.3% and specificities of 60.5% and 84.7%, respectively; the internal calibration was acceptable (Hosmer-Lemeshow: P =  .688; slope = 1.00; intercept = 0.00), consistent with the decile calibration plot (Fig. 2).

Figure 1.

ROC curves for screening of high blood pressure (systolic and/or diastolic BP ≥ P90) based on anthropometric indicators. (A) Boys. (B) Girls.

Figure 2.

Decile calibration plot: observed vs predicted.

Although the literature on high blood pressure in children in Spain is scarce, the prevalence observed in our cohort (5.8%) falls within the range reported in domestic studies that used similar methodologies. In the Valencian Community, the ANIVA study21 found higher prevalences in children aged 6–9 years (8.1% with prehypertension and 8% with hypertension), with an increasing frequency of high BP associated with increasing weight, while, in Madrid, Marrodán et al.22 described lower prevalences (3.05% in girls and 3.17% in boys) that were consistent with the 4.82% prevalence previously reported by the same group.23 A subsequent update in older children and adolescents (ages 10–17) found a higher prevalence of 7.3%, underscoring how the magnitude of the problem increases in older age groups.24 When it comes to rural settings, a study conducted in Antas (Almería) also found similar figures (4.46% prevalence of hypertension), and more than half of children with hypertension were obese.25 Overall, this range (≈3%–8%) indicates that the prevalence estimates in our study are epidemiologically plausible in Spain, although BP values should be interpreted as screening results on account of the single-visit design.

At the international level, there is evidence of an increasing trend in the prevalence of high BP in the pediatric population. The HyperChildNET network highlighted the long-standing underestimation of this risk factor in children, despite its potential to persist throughout the lifespan.26 One meta-analysis27 estimated a global prevalence of approximately 4%, with variations based on age, a substantial increase in association with obesity (≈15%), and evidence of a relative increase in prevalence of 75% to 79% between 2000 and 2015. A later update confirmed that the trend persisted, showing an increase of up to 6.53% in the span of two decades.28

The prevalence varies between regions (Sudan,29 Cameroon,30 Portugal31 and Lithuania32), with intermediate values in India and China.5 In Latin America, studies conducted in Mexico33 contribute additional evidence supporting the utility of the NC as a marker of excess weight.

The association between adiposity and high BP observed in our sample is consistent with what has been reported in other studies in Spain22,34 and abroad30,32,35,36 and with the roles of visceral fat and insulin resistance, sympathetic activation and early vascular changes as hemodynamic determinants. Furthermore, the findings of the CHOP37 and GENOBOX38 studies suggest that diet (including the consumption of ultraprocessed foods) plays a role in adiposity and cardiometabolic risk, reinforcing the importance of preventive interventions from an early age.

The key differential finding of our study emerged in the multivariate adjustment. Contrary to the studies by Marrodán et al.22 and Niba et al.,30 in which the BMI and WHtR maintained their predictive capacity, in our models, the classic indicators (BMI, WHtR, ∑4SF, and %BF) were no longer significant after the adjustment, while the NC was independently associated with high BP in three out of the four models (with the p value near the significance threshold in the BMI model). The reason that indicators such as BMI or WHtR became nonsignificant in certain subgroups and multivariate models involves the limited statistical power (low prevalence of high BP) and the collinearity of anthropometric variables. However, the NC exhibited a persistent association because it is a direct indicator of upper body subcutaneous fat, whose pathogenic effect on blood pressure is independent of visceral fat.39–41 In this regard, our findings support the usefulness of NC as a simple marker for cardiometabolic screening, as proposed by Androutsos et al.42

In the assessment of discriminative ability, the performance of the NC differed by sex. In boys, the NC showed a moderate discriminative ability (AUC = 0.700), compared to a high discriminative ability in girls (0.936), with optimal cut-off points (Youden’s index) of 29.15 and 30.65 cm, respectively. These differences were consistent with the greater hemodynamic sensitivity previously described in female individuals.21,30,43 The pubertal increase in NC is subject to sexual dimorphism. In female adolescents, it mainly corresponds to an increase in subcutaneous fat, whereas in male adolescents there is also a physiological increase in fat-free mass (development of neck and airway muscles). This association limits the accuracy of the NC as an isolated indicator of adiposity in male individuals.39 The cut-off points should be interpreted as optimal thresholds for this cohort and require external validation prior to their generalization; furthermore, in the pediatric population, raw values may vary with growth and development. The calibration was internal (within-sample), and it does not replace external validation.

The NC offers practical advantages: it is a simple and stable measure,43 and it was the indicator that performed best in our cohort, in agreement with the associations described in other populations.28 Overall, the findings support the usefulness of the NC as a screening tool for high BP in school settings, consistent with recent reviews on anthropometric markers and cardiometabolic risk in childhood.39

The prevalence of high BP (≥P90) was 5.8% and increased with excess weight. The NC was the most consistent predictor of high BP after multivariable adjustment, and it performed better in girls compared to boys. The proposed cut-off points (29.15 and 30.65 cm) require external validation.

Carlos Recio Añón: study conceptualization and design; data collection; drafting of the manuscript. Manuel A. Sastre Domínguez: statistical analysis; visual representation of results; critical review of the manuscript. Julia Carracedo Añón: methodological supervision; critical review of the manuscript. Antonio González Martín: methodology and interpretation of results; critical review of the manuscript; and María Dolores Marrodán Serrano: coordination and oversight of the study; final review and editing of the manuscript. All authors approved the final version of the manuscript and share the responsibility for its content.

The study did not receive any external funding.