High Blood Pressure in Children Aged 3 to 12 Years Old With Overweight or Obesity

Abstract

Objective:

(1) To describe the prevalence of high blood pressure (BP) and the association with BMI in young children with overweight/obesity; (2) to evaluate the accuracy of a single high BP to diagnose sustained hypertension over three visits.

Methods:

We used pre-intervention data from the Improving Pediatric Obesity Practice Using Prompts (iPOP-UP) trial. We included children aged 3–12 years with BMI ≥85th percentile at well-visits in 2019–2021 at 84 primary care practices in 3 US health systems in the Northeast, Midwest, and South. BP percentiles were calculated from the first visit with BP recorded during the study period. Hypertensive-range BP was defined by the 2017 American Academy of Pediatrics guideline. We tested the association between BMI classification and hypertensive BP using multivariable logistic regression.

Results:

Of 78,280 children with BMI ≥85th percentile, 76,214 (97%) had BP recorded during the study period (mean 7.4 years, 48% female, 53% with overweight, and 13% with severe obesity). The prevalence of elevated or hypertensive BP was 31%, including 27% in children with overweight and 33%, 39%, and 49% with class I, II, and III obesity, respectively. Higher obesity severity was associated with higher odds of hypertensive BP in the multivariable model. Stage 2 hypertensive BP at the initial visit had specificity of 99.1% (95% confidence interval 98.9–99.3) for detecting sustained hypertension over ≥3 visits.

Conclusions:

High BP is common in 3- to 12-year-olds with overweight/obesity, with higher obesity severity associated with greater hypertension. Children with overweight/obesity and stage 2 BP are likely to have sustained hypertension and should be prioritized for evaluation.

Trial Registration:

ClinicalTrials.gov Identifier: NCT05627011

Introduction

Children with both obesity and hypertension are at higher risk for future cardiovascular morbidity and mortality than children with either risk factor alone.¹ With the rising prevalence of overweight/obesity to more than one in three US children^2,3 and high rates of comorbid hypertension that track into adulthood,^4–6 the prevalence of hypertension is projected to increase from 120 million to 163 million persons in the United States by 2060, resulting in a substantial increase in heart disease and stroke.⁷ Based on observational data showing that reduction in cardiovascular risk factors from childhood to adulthood is associated with lower incidence of cardiovascular events,¹ identifying and treating hypertension and obesity in children may have the potential to reduce the burden of cardiovascular disease on both individual and population health.

Owing to the higher prevalence of hypertension in ∼15% of children with obesity compared with 2% of children with normal BMI,⁶ a 2017 American Academy of Pediatrics (AAP) guideline on hypertension recommends measuring blood pressure (BP) at every health care encounter for children with obesity starting at 3 years old,⁸ which was reiterated in a 2023 AAP guideline on obesity.⁹

The 2017 AAP guideline also introduced new pediatric BP reference values that excluded children with overweight/obesity from the normative data,¹⁰ resulting in a decrease in BP cutoffs for hypertension.¹¹ Multiple studies have applied these new norms to estimate the prevalence of hypertension in adolescents^11–14 and in patients in the National Health and Nutrition Examination Survey (NHANES),^15,16 in which BP measurement starts at 8 years old.

The few studies reporting the prevalence of hypertension in children younger than 8 years old with elevated BMI using the 2017 guideline have been limited to children enrolled in obesity management programs,^17,18 which may not be generalizable to routine general pediatric care, and a single-center primary care study¹⁹ suggesting that children aged 3–12 years and children with overweight BMI experienced a twofold increase in the prevalence of hypertension following adoption of the 2017 guideline⁸ compared with the 2004 Fourth Report.¹⁹

To overcome the limitations of past studies and to understand the practical implications of current guidelines, our primary objective was to estimate the frequency of high BP readings and the association between BMI classification and high BP in >70,000 children aged 3–12 years with overweight/obesity presenting for primary care visits in three US health systems. We also assessed whether the association between BMI classification and high BP was modified by age as we hypothesized that this association may be stronger in older children who may have had obesity for a longer duration.

Because clinicians must make decisions about follow-up testing based on a single BP measurement, our secondary objective was to evaluate the sensitivity and specificity of using a single high BP reading in a child with overweight/obesity to diagnose sustained hypertension measured over three visits.

Methods

Study Population

We conducted a cross-sectional study based on pre-intervention data from the Improving Pediatric Obesity Practice Using Prompts (iPOP-UP) trial (NCT05627011), a cluster randomized controlled trial assessing the effectiveness and implementation of electronic clinical decision support in primary care to promote the adoption of clinical practice guidelines⁹ for the management of pediatric obesity. The study population included children aged 3–12 years seen in 2019–2021 at 84 primary care practices affiliated with 3 US health systems in the Northeast, Midwest, and South that had agreed to participate in iPOP-UP.

To ensure that patients were presenting to their primary care office to be included in iPOP-UP, all children met the following inclusion criteria: (1) BMI ≥85th percentile for age and sex measured at a primary care well-visit with a prescribing clinician (physician, nurse practitioner, and physician assistant); and (2) had another well-visit during the study period or in the 3 years before the qualifying visit. For this study, we applied the additional inclusion criteria that patients had at least one BP measurement at a well-visit or follow-up visit during the study period (Supplementary Tables S1 and S2).

Acute visits or sick visits with BP measured were not included. BMI was calculated using weight and height from the same visit. Age- and sex-specific BMI percentiles were based on the 2000 Centers for Disease Control and Prevention growth charts.²⁰ Since our objective was to describe the frequency of high BP readings in this population during routine visits, we still included children if they had a pre-existing diagnosis of hypertension or were taking medications known to affect BP.

Data Query Processes

All data were extracted retrospectively from the electronic health record (EHR) by a biomedical informatics team familiar with the local data structure at each of the three health systems. Our study team of clinical informaticians and health services researchers developed a data query protocol detailing inclusion/exclusion criteria, the full list of variables and supporting details as needed, and secure data transfer instructions. The informatics lead at each site reviewed the protocol with their local EHR analyst, who then queried the data, and transferred it back to their respective informatics lead.

The informatics lead reviewed the queried data for accuracy, to confirm data deidentification, and evaluate clinical correlation of the data to the variables before transferring it to a central data warehouse for management, cleaning, and analyses. At the central location, data were matched by variable. The team reviewed data content similarity and missing data across sites as part of the quality control evaluation.

Covariates

Demographic and clinical characteristics were extracted from the EHR at the time of the first visit with BP recorded. The main exposure was BMI classification, defined as overweight (BMI ≥85th percentile to <95th percentile for age and sex), class I obesity (BMI ≥95th percentile to <120% of the 95th percentile), class II obesity (BMI ≥120% to <140% of the 95th percentile), and class III obesity (BMI ≥140% of the 95th percentile).²¹

Outcome

Using age-, sex-, and height-based pediatric reference norms to calculate BP percentiles,¹⁰ we applied the 2017 AAP guideline⁸ to classify systolic or diastolic BPs ≥90th to <95th percentile as elevated BP, systolic or diastolic BPs ≥95th percentile as hypertensive BP, and having either elevated or hypertensive BP as high BP. For the primary analysis, BP percentiles were calculated from the first visit with BP recorded.

For children with multiple BP values recorded at the same encounter, we obtained the last-recorded (timestamped) BP for the analysis as subsequent BP measurements from the same encounter tend to be lower due to the accommodation effect.^22,23 We also report the BP index (measured BP divided by 95th percentile BP). In a sensitivity analysis restricted to children with BP at ≥3 separate visits (detailed as follows), we defined the outcome of sustained hypertension as a hypertensive reading at ≥3 visits.

Statistical Analysis

In descriptive analyses, we calculated the proportion of children with normal, elevated, and hypertensive BP overall and stratified by BMI category. The proportion of children with hypertensive BP was compared across BMI categories using the chi-squared test. Linear contrasts were constructed to test for linear trend of mean BP, BP percentiles, and BP indices across BMI categories.

We also compared demographic and clinical characteristics between children included in the study population and children excluded due to lack of BP measurement during the study period. We evaluated the association between BMI category and hypertension or high BP using multivariable logistic regression, adjusted for age, sex, and the interaction between BMI category and age to determine if the association between BMI category and hypertension was modified by age.

Because the diagnosis of hypertension requires BP measurements on three separate occasions, we performed a sensitivity analysis in which we defined sustained hypertension as a hypertensive BP at each of at least three separate visits for the subgroup of children with ≥3 visits with BP measurements during the study period and excluded children with <3 visits with BP measurements from this analysis. The three hypertensive BP readings did not necessarily occur at consecutive visits to meet criteria for sustained hypertension. We evaluated the association between BMI category and sustained hypertension using a similar multivariable model as described earlier.

In secondary analyses, we performed a retrospective cohort study to assess the sensitivity and specificity of using a hypertensive BP at the first visit to predict sustained hypertension in the subgroup of children with ≥3 visits with BP measurements. For this analysis, stage 1 hypertension was defined as a BP ≥95th percentile and <95th percentile plus 12 mmHg and stage 2 hypertension was defined as a BP ≥95th percentile plus 12 mmHg.⁸ To evaluate for verification bias in which children with hypertensive BP at the first visit may be more likely to have follow-up BP measurements to verify their hypertension status, we compared BP values at the initial visit between patients included and excluded from this secondary analysis.

We defined statistical significance as p < 0.05 (two-sided). Statistical analyses were conducted in R, version 4.2.1 and SAS, version 9.4. BP percentiles¹⁰ were calculated in Stata/SE 17.0. BMI percentiles were calculated using the CDC SAS program for growth charts.²⁴ The study was approved by the Yale institutional review board.

Results

Of 78,280 children with BMI ≥85th percentile presenting for well-visits during the study period, 76,214 (97%) children had BP recorded in at least one visit (Supplementary Fig. S1). Among children with BP recorded, the mean age was 7.4 years [standard deviation (SD) 2.8], 48% were female, 33% were non-Hispanic White, 31% non-Hispanic Black, and 20% Hispanic/Latino (Table 1). Overweight BMI occurred in 53% of children, class I obesity in 34%, class II obesity in 9%, and class III obesity in 4%. Compared with included patients, patients excluded due to lack of BP measurement were younger [mean 4.5 years (SD 2.1) vs. 7.4 years (SD 2.8)] and had less severe obesity (10% vs. 13% with class II or III obesity) (Supplementary Table S3).

Table 1.

Study Population Characteristics by BMI Category

Characteristic	Overall, N = 76,214	Overweight, N = 40,339	Class I obesity, N = 25,937	Class II obesity, N = 7130	Class III obesity, N = 2808
Site
Northeast	44,603 (59%)	24,760 (61%)	14,699 (57%)	3780 (53%)	1364 (49%)
South	20,318 (27%)	10,434 (26%)	7119 (27%)	1933 (27%)	832 (30%)
Midwest	11,293 (15%)	5145 (13%)	4119 (16%)	1417 (20%)	612 (22%)
Age, years, mean (SD)	7.38 (2.76)	7.22 (2.77)	7.24 (2.78)	8.31 (2.52)	8.57 (2.37)
Age category, years
3–7	41,621 (55%)	23,021 (57%)	14,629 (56%)	2947 (41%)	1024 (36%)
8–12	34,593 (45%)	17,318 (43%)	11,308 (44%)	4183 (59%)	1784 (64%)
Sex
Male	39,443 (52%)	20,104 (50%)	13,898 (54%)	3834 (54%)	1607 (57%)
Female	36,771 (48%)	20,235 (50%)	12,039 (46%)	3296 (46%)	1201 (43%)
Race/ethnicity
Hispanic/Latino	15,045 (20%)	6738 (17%)	5735 (22%)	1931 (27%)	641 (23%)
Hispanic/Latino multiracial	125 (0.2%)	67 (0.2%)	39 (0.2%)	13 (0.2%)	6 (0.2%)
Non-Hispanic Asian	2507 (3.3%)	1509 (3.7%)	824 (3.2%)	137 (1.9%)	37 (1.3%)
Non-Hispanic Black	23,764 (31%)	11,301 (28%)	8272 (32%)	2779 (39%)	1412 (50%)
Non-Hispanic multiracial	1617 (2.1%)	893 (2.2%)	539 (2.1%)	133 (1.9%)	52 (1.9%)
Non-Hispanic other	4248 (5.6%)	2480 (6.1%)	1355 (5.2%)	321 (4.5%)	92 (3.3%)
Non-Hispanic White	25,211 (33%)	15,471 (38%)	7886 (30%)	1447 (20%)	407 (14%)
Not reported	3697 (4.9%)	1880 (4.7%)	1287 (5.0%)	369 (5.2%)	161 (5.7%)
Primary insurance
Private/commercial	37,189 (49%)	22,087 (55%)	11,770 (45%)	2512 (35%)	820 (29%)
Public	35,816 (47%)	16,722 (41%)	13,002 (50%)	4266 (60%)	1826 (65%)
Self-pay/uninsured/other	1700 (2.2%)	764 (1.9%)	639 (2.5%)	219 (3.1%)	78 (2.8%)
Missing	1509 (2.0%)	766 (1.9%)	526 (2.0%)	133 (1.9%)	84 (3.0%)
Primary language
English	65,018 (85%)	35,359 (88%)	21,622 (83%)	5693 (80%)	2344 (83%)
Spanish	9378 (12%)	4022 (10.0%)	3665 (14%)	1271 (18%)	420 (15%)
Other/missing	1818 (2.4%)	958 (2.4%)	650 (2.5%)	166 (2.3%)	44 (1.6%)

BMI categories were defined as overweight (BMI ≥85th percentile to <95th percentile for age and sex based on the 2000 Centers for Disease Control and Prevention growth charts), class I obesity (BMI ≥95th percentile to <120% of the 95th percentile), class II obesity (BMI ≥120% to <140% of the 95th percentile), and class III obesity (BMI ≥140% of the 95th percentile).

SD, standard deviation.

We observed a significant linear trend between BMI category and mean BP (p < 0.001) (Table 2). Mean systolic and diastolic BP percentiles were highest in children with class III obesity (76th and 77th percentiles, respectively) and lowest in children with overweight (64th and 71st percentiles, respectively). Overall, the proportion of children with high BP at the initial visit was 31%. The proportion of children with high BP differed by BMI category (p < 0.001) such that greater obesity severity was associated with a higher proportion with high BP—27% of children with overweight and 49% of children with class III obesity had BP in the elevated or hypertensive range at their initial visit (Fig. 1).

Table 2.

Distribution of Blood Pressure Readings by BMI Category

	Overall, N = 76,214	Overweight, N = 40,339	Class I obesity, N = 25,937	Class II obesity, N = 7130	Class III obesity, N = 2808	p a
Systolic BP, mean (SD)	103 (10)	101 (9)	103 (10)	107 (10)	110 (10)	<0.001
Diastolic BP, mean (SD)	64 (7)	64 (7)	65 (7)	67 (7)	69 (8)	<0.001
Systolic percentile, mean (SD)	66 (24)	64 (24)	67 (24)	72 (23)	76 (22)	<0.001
Diastolic percentile, mean (SD)	72 (20)	71 (20)	73 (20)	75 (19)	77 (19)	<0.001
Systolic BP index,b mean (SD)	0.90 (0.08)	0.89 (0.07)	0.90 (0.07)	0.92 (0.08)	0.94 (0.08)	<0.001
Diastolic BP index, mean (SD)	0.88 (0.10)	0.88 (0.10)	0.89 (0.10)	0.90 (0.09)	0.92 (0.10)	<0.001
BP category						<0.001
Normal (<90 percentile)	52,463 (69%)	29,251 (73%)	17,426 (67%)	4351 (61%)	1435 (51%)
Elevated (≥90 percentile to <95 percentile)	10,454 (14%)	5158 (13%)	3710 (14%)	1111 (16%)	475 (17%)
Stage 1 hypertensivec	12,500 (16%)	5645 (14%)	4526 (17%)	1546 (22%)	783 (28%)
Stage 2 hypertensived	797 (1.0%)	285 (0.7%)	275 (1.1%)	122 (1.7%)	115 (4.1%)

BMI categories were defined as overweight (BMI ≥85th percentile to <95th percentile for age and sex based on the 2000 Centers for Disease Control and Prevention growth charts), class I obesity (BMI ≥95th percentile to <120% of the 95th percentile), class II obesity (BMI ≥120% to <140% of the 95th percentile), and class III obesity (BMI ≥140% of the 95th percentile).

BP percentiles and hypertension definitions were based on the 2017 American Academy of Pediatrics clinical practice guideline on hypertension.

^a Linear contrasts were constructed to test for linear trend of mean BP, mean BP percentiles, and mean BP indices across BMI categories. The prevalence of hypertensive and elevated BP was compared across BMI categories using the chi-squared test for proportions.

^b The BP index is equal to the measured BP divided by the 95th percentile BP for age, sex, and height.

^c Stage 1 hypertensive BP was a systolic or diastolic BP ≥95th percentile and <95th percentile +12 mmHg according to the 2017 American Academy of Pediatrics clinical practice guideline on hypertension.

^d Stage 2 hypertensive BP was a systolic or diastolic BP ≥95th percentile +12 mmHg according to the 2017 American Academy of Pediatrics clinical practice guideline on hypertension.

BP, blood pressure.

Figure 1.

Proportion of children with high BP at initial visit by BMI category. BMI categories were defined as overweight (BMI ≥85th percentile to <95th percentile for age and sex based on the 2000 Centers for Disease Control and Prevention growth charts), class I obesity (BMI ≥95th percentile to <120% of the 95th percentile), class II obesity (BMI ≥120% to <140% of the 95th percentile), and class III obesity (BMI ≥140% of the 95th percentile). Hypertensive BP was defined as a BP ≥95th percentile for age, sex, and height according to the 2017 American Academy of Pediatrics clinical practice guideline for hypertension. Elevated BP was defined as a BP ≥90th percentile and <95th percentile for age, sex, and height. BP, blood pressure.

In the multivariable model, children with class I, class II, or class III obesity had significantly higher odds of hypertensive BP and of high BP than children with BMI in the overweight category (Table 3). We observed significant effect modification by age (interaction p < 0.001 for the outcome of hypertensive BP; interaction p < 0.001 for the outcome of elevated BP or hypertensive BP) such that the association between obesity severity and each outcome was more pronounced in older than younger children.

Table 3.

Association Between BMI Category and High Blood Pressure (N = 76,214)

BMI categorya	Hypertensive BPb outcome		Elevatedc or hypertensive BP outcome
	3–7 yo, aOR (95% CI)d	8–12 yo, aOR (95% CI)d	3–7 yo, aOR (95% CI)d	8–12 yo, aOR (95% CI)d
Overweight	Ref.	Ref.	Ref.	Ref.
Class I obesity	1.27 (1.2–1.34)	1.39 (1.3–1.49)	1.24 (1.18–1.29)	1.36 (1.29–1.43)
Class II obesity	1.63 (1.49–1.78)	2.07 (1.9–2.26)	1.54 (1.42–1.67)	1.96 (1.82–2.1)
Class III obesity	2.48 (2.16–2.83)	3.21 (2.87–3.58)	2.32 (2.05–2.63)	2.92 (2.65–3.23)

^a BMI categories were defined as overweight (BMI ≥85th percentile to <95th percentile for age and sex based on the 2000 Centers for Disease Control and Prevention growth charts), class I obesity (BMI ≥95th percentile to <120% of the 95th percentile), class II obesity (BMI ≥120% to <140% of the 95th percentile), and class III obesity (BMI ≥140% of the 95th percentile).

^b Hypertensive BP was defined as a BP ≥95th percentile for age, sex, and height according to the 2017 American Academy of Pediatrics clinical practice guideline for hypertension.

^c Elevated BP was defined as a BP ≥90th percentile and <95th percentile for age, sex, and height.

^d In the multivariable logistic regression model including BMI category, continuous age, sex, and the interaction of continuous age and BMI category, the interaction term was statistically significant (interaction p < 0.001 for the hypertensive BP outcome; interaction p < 0.001 for the elevated or hypertensive BP outcome). Therefore, we present our results stratified by age group (3–7 yo vs. 8–12 yo) for ease of interpretation. Unadjusted odds ratios were not meaningfully different from adjusted odds ratios.

aOR, adjusted odds ratio; CI, confidence interval; yo, years old.

In the sensitivity analysis in which hypertension status was determined by BP ≥95th percentile at three separate visits, 8155 children (11%) had ≥3 visits with BP recorded during the study period. The median time from first to second measurement was 371 days [interquartile range (IQR) 311–419] and from second to third measurement was 367 days (IQR 286–388). As in the primary analysis, higher obesity severity remained significantly associated with hypertension defined as three separate visits with BP in the hypertensive range (Supplementary Table S4).

The magnitude of effect sizes was larger than in the primary analysis. For example, class III obesity vs. overweight was associated with 6.0-times higher odds of sustained hypertension in the sensitivity analysis compared with 2.5- to 3.2-times higher odds of hypertensive BP in the primary analysis. In the sensitivity analysis, the interaction between age and obesity severity was not significant.

In secondary analyses evaluating the accuracy of using a hypertensive-range BP at the initial visit to detect sustained hypertension over three visits, an initial BP ≥95th percentile had a sensitivity of 89.4% [95% confidence interval (CI) 85.4–92.6] and specificity of 84.7% (95% CI 83.8–85.4) for sustained hypertension, defined as hypertensive-range BP at each of at least three separate visits. An initial BP in the stage 2 hypertension range ≥95th percentile plus 12 mmHg had high specificity [99.1% (95% CI 98.9–99.3)] and low sensitivity [6.8% (95% CI 4.2–10.2)] for detecting sustained stage 1 or stage 2 hypertension.

In the assessment of verification bias, we found that BP indices, BP percentiles, and the prevalence of hypertensive BP at the initial visit were similar between patients included and excluded from this secondary analysis (Supplementary Table S5).

Discussion

In this multicenter study of >70,000 children aged 3–12 years with overweight/obesity presenting for well-visits in three US health systems, 31% of children had high BP at their initial visit, and higher obesity severity was associated with greater odds of hypertension. Stage 2 hypertensive BP at the initial visit had high specificity for sustained hypertension assessed over three visits, which reinforces the AAP guideline's recommendation to initiate lifestyle counseling and consider subspecialty referral after a single stage 2 reading.⁸ To the best of our knowledge, this is the largest study to describe BP profiles in young children with overweight/obesity using the 2017 guideline.⁸

The association between BMI and BP is well-documented in adolescents and older children.^25–31 In school-based screening of 21,062 adolescents in Houston, the prevalence of hypertension on initial BP measurement was 16% in adolescents with overweight/obesity compared with 7% in adolescents with BMI <85th percentile.²⁶ EHR data from pediatric primary care clinics³² have demonstrated this association between BMI and hypertension in younger children using previous norms from the 2004 Fourth Report.³³

At the population level, serial analyses of children ≥8 years old in NHANES have found that the rise in pediatric hypertension since the 1980s can be partially explained by increasing BMI.^34,35 Our study builds on this literature by testing the association between BMI and BP in a large population of children with overweight/obesity as young as 3 years old based on the 2017 guideline.⁸

It is notable that 3% of our population had well-visits but never had BP recorded. This finding is an improvement from national data showing that hypertension screening occurred at 84%–89% of preventive visits for children with obesity from 2000 to 2018,^36,37 which was higher than the screening rate of ∼75% for the general pediatric population during that period.³⁷

Higher screening rates in our study may reflect increased hypertension screening after the 2017 guideline recommended BP measurement at every encounter for children with obesity⁸ and our inclusion criteria capturing children presenting to their primary care office. Forgoing BP measurement in childhood is concerning, particularly for children with obesity, as up to 40% of children with hypertension already have evidence of end-organ damage with left ventricular hypertrophy at the time their hypertension is detected³⁸ and obesity is an independent risk factor for left ventricular hypertrophy,³⁹ even after controlling for the degree of hypertension.⁴⁰

Despite recommendations for more frequent follow-up in children with overweight/obesity,⁹ the median time between visits with BP measurements in our study was ∼1 year. Clinical decision support has the potential to close this gap in hypertension screening and earlier follow-up for children with overweight/obesity. Published decision support tools have focused on improving clinician recognition and management of high BP in children by delivering alerts after an abnormal BP is recorded.^41–46

The effectiveness of prompts that promote measurement of BP when indicated (e.g., in a child with risk factors for hypertension such as obesity) is less clear. The clinical decision support intervention in iPOP-UP will prompt clinicians to check BP at every visit through a best practice advisory noting whether BP was measured during the visit, a standardized note template documenting whether BP was measured, and a smart set that reports BP at the last three encounters.

Thus, a secondary outcome of iPOP-UP is the change in clinician adherence to the recommendation for BP screening at every encounter for children with obesity.^8,9 Combined with reminders recommending follow-up for elevated BMI, iPOP-UP has the potential to promote more frequent BP measurements for children with overweight/obesity.

Our study has several limitations. First, the primary outcome was based on BP at a single visit. Although a definitive diagnosis of hypertension requires BP at ≥3 visits,⁸ we used BP at one visit as our primary outcome to determine the real-world implications of high BP in this population as clinicians make decisions about the need for further evaluation based on a single BP. In addition, high BP at a single visit in childhood has been shown in prospective studies to be associated with premature cardiovascular mortality in adulthood.¹

Consistent with prior literature,⁴⁷ we found in our sensitivity analysis of patients with ≥3 BP measurements that the magnitude of the association between BMI and hypertension was stronger when hypertension was defined based on three visits instead of one visit. Thus, misclassification based on a single BP likely biased our primary results toward the null. For children with multiple BP measurements at the same visit, we used the last BP on that day to account for the accommodation effect because repeated measurements tend to be lower.^22,23

Although using the lowest BP (not necessarily the last BP) at a single visit provides the most conservative estimate of hypertension prevalence,^23,48 the final measurement is typically also the lowest value²³ and data on additional BP measurements from the same visit were not available. Second, information on measurement technique and cuff size was not available and may have varied between clinics and clinicians.

Likewise, details on lower extremity BP measurements, which may be timestamped last and tend to be higher than upper extremity BP measurements, were not available; although lower extremity BP measurements are rarely performed in pediatric primary care⁴⁹ despite the AAP recommendation for their use as part of the evaluation of a child with hypertension.⁸ Third, patients who turned 13 years old during the study period before they had three BP measurements were excluded from the sensitivity analysis on sustained hypertension.

Fourth, BMI is a limited measure of body composition because it does not differentiate between fat mass and muscle mass.⁵⁰ Future study may investigate alternative anthropometric measures such as waist circumference and waist-height ratio, as these measures may be better predictors of cardiometabolic risk in children.⁵¹

Fifth, analyzing the accuracy of a single BP at detecting sustained hypertension may introduce verification bias,⁵² a form of selection bias such that children with higher BP at their initial visit may be more likely to have follow-up BP checks. Verification bias tends to overestimate sensitivity and underestimate specificity.⁵³ We did not find significant evidence of verification bias as BP values at the first visit were similar between patients with and without ≥3 visits with BP measured. Nevertheless, the low sensitivity of a single BP highlights the importance of measuring BP at every encounter for children with obesity.^8,9

The limited utility of a normal clinic BP in a child with obesity is further impacted by the high prevalence of “masked” hypertension (normal clinic BP with high BP outside clinic) in children with obesity,⁵⁴ which has prompted the AAP⁸ to recommend strongly considering ambulatory BP monitoring for children with obesity and normal clinic BP. Sixth, follow-up may have been adversely affected by the COVID-19 pandemic during the study period.

Finally, our retrospective data can describe the frequency of high BP readings in routine clinical practice in this population, but our analysis may be affected by unmeasured factors associated with both obesity and BP. Thus, we cannot make causal inferences about the relationship between changes in obesity class and BP. In addition, using BMI at a single point in time does not account for the duration of obesity before the study started or how the change in BMI over time may influence the clinician's decision to check BP during follow-up. The results of iPOP-UP will provide data on the effectiveness of electronic decision support on the primary outcome of change in BMI and the associated change in BP.

Conclusions

High BP is common in children aged 3–12 years with overweight/obesity. Consistent with current guidelines,⁸ children with overweight/obesity and stage 2 hypertension readings are likely to have sustained hypertension and should be prioritized for further evaluation.

Impact Statement

In this multicenter study of >70,000 children aged 3–12 years old with overweight or obesity, 31% of children had elevated or hypertensive blood pressure readings, with higher obesity severity associated with greater hypertension. A single stage 2 hypertensive reading had high specificity for sustained hypertension over three visits.

Prior Presentation

A version of this study was presented as an oral abstract at the Pediatric Academic Societies meeting on May 1, 2023.

Authors' Contributions

J.T.N. conceptualized and designed the study, contributed to analyses, drafted the initial article, and critically reviewed and revised the article. K.R.M. conducted the statistical analyses and critically reviewed and revised the article. E.B.F., R.W.G., C.T.W., and J.J.M. contributed to analyses, coordinated and supervised data collection, and critically reviewed and revised the article. D.E. contributed to analyses, provided oversight and supervision, and critically reviewed and revised the article. Y.L. conceptualized and designed the study, contributed to analyses, and critically reviewed and revised the article. M.S. conceptualized and designed the study, coordinated and supervised data collection, contributed to analyses, provided oversight and supervision, and critically reviewed and revised the article. All authors approved the final article as submitted and agree to be accountable for all aspects of the study.

Funding Information

Research reported in this publication was supported by the National Institute on Minority Health and Health Disparities of the National Institutes of Health under award number R01MD014853 and the Yale Clinical and Translational Science award (UL1 TR001863). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The study sponsor had no role in study design, analysis of data, writing of the article, or the decision to submit the article for publication.

Author Disclosure Statement

Dr. Grout has received institutional grant funding from Pfizer, Inc. for unrelated work.