Hypertension in adolescents: The role of obesity and family history

Abstract We evaluated the combined effect of obesity and family history (FH) on the risk of hypertension in adolescents. We studied 1288 school‐aged adolescents aged 16.0 ± 0.5 years (49.0% males) attending the medical examination for enrollment in the city of Nanning, China. Their blood pressure, weight, and height were measured. A questionnaire was administered to both adolescents and their parents to obtain information on the participants’ medical history. Multiple logistic regression analysis, according to bodyweight categories and adjusted for age, gender, and body mass index (BMI), was done to determine the association of FH with hypertension. Hypertension was found in 14.1% of adolescents. The prevalence of hypertension was significantly higher in adolescents with obesity and positive FH than their normal weight and negative FH counterparts. For adolescents with normal weight and waist circumstance (WC), those with a positive FH in parents compared to those without had an significantly increased risk for hypertension (odds ratio [OR], 2.15; 95% confidence interval [CI] 1.28–3.61, and 1.96; 95% CI 1.16–3.32, respectively). These findings were adjusted for age, gender, and BMI. Our study showed that routine screening for pediatric hypertension should be performed in adolescents who are overweight and obese. Furthermore, parental FH of hypertension played an important role in predicting the hypertension phenotype among adolescents with normal weight.

pediatric population according to our previous studies. 8 However, essential hypertension remains to be the most common type found among adolescents.
Essential hypertension often presents with modest BP elevations. It is associated with being overweight or obese, a contributory family history (FH), higher dietary sodium intake, and premature birth. 9 As the earliest manifestation of adult cardiovascular disease, essential hypertension in children has yet to be given more consideration.
A simple and accurate screening method to identify pediatric hypertension is urgently needed. Obesity and positive FH are the major determinants of essential hypertension in adults and children. 10 Overall and abdominal obesity, measured by body mass index (BMI) and waist circumference (WC), are common alternative measures of adiposity in clinical and public health practice.
Hypertension exhibits familial clustering, 11,12 and is associated with higher BP in offspring of hypertensive parents or grandparents. 12,13 However, there is a paucity of data in the joint effect of FH and obesity on the risk of hypertension. In this study, we assessed the combined effect of obesity and a positive FH in estimating the risk of hypertension in healthy Chinese adolescents.

Study design and population
The participants included 1316 high school freshmen.

Anthropometrics and BP measurements
The anthropometric measurements were performed according to standard protocols. Bodyweight and height were measured with light clothing and without shoes. WC was measured at the midpoint between the right lower rib and the iliac crest, and after a slight breath out. Weight was measured in kilograms (kg) and rounded off to 2 decimal places.
Height and WC were measured to the nearest 0.1 centimeter (cm

Definition of obesity and hypertension
Overweight and obesity were defined as BMI above the 85th and 95th percentiles, respectively, of age-and sex-specific reference values for Chinese adolescents. 14 Abdominal obesity was defined as a WC above the 85th percentiles of age-and sex-specific reference values. 15 Elevated BP and hypertension were defined as either an SBP or DBP above the 90th and the 95th percentiles, respectively, of age-, sex-, and height-specific reference values for Chinese adolescents. 16

Family history (FH) of essential hypertension (EH) definition
A "complete" FH consists of three generations, including the study participants, their parents as first-degree relatives, and grandparents as second-degree relatives. A positive FH of EH was defined as at least one biological parent or grandparent with EH. A negative FH was defined as the individuals' parents and all the grandparents were negative for EH. Diagnosis of EH (ie, BP of 140/90 mmHg, on antihypertensive medications, or verified by the individual's physician) was reported by individuals and their parents through questionnaires, further confirmed through remote consultation. If a parent or grandparent had passed away, diagnosis of EH was determined by whether he had hypertension before his death.

Statistical analyses
General statistical analyses were carried out using Statistical Package   Figure 1 shows the prevalence of normal BP, elevated BP, and hypertension stratified by body weight categories and FH status.

Association of FH with hypertension in offspring
Logistic regression analysis results shown in Table 2

Comparison of participants with different FH status
Analyses of the anthropometrics of individuals with different FH status is shown in Table 3. The individuals with positive FH show a higher BMI, WC, SBP, and DBP (P = .092, P = .438, P = .055, and P = .003, respectively). Furthermore, individuals with positive FH involving grandparents showed a higher trend on parameters compared to those with negative FH (although not statistically significant). In addition, offspring with positive FH involving parents, showed the highest WC, BMI, and DBP, irrespective of FH status of grandparents (P = .003, P = .001, and P = .011, respectively).

DISCUSSION
In the present study, we investigated the combined effect of obesity Abbreviations: BMI, body mass index; FH, in parents: at least one parent diagnosed with hypertension irrespective of FH status of grandparents.; FH, only in grandparents: at least one grandparent diagnosed with hypertension without such a parental history; SBP, systolic blood pressure, DBP, diastolic blood pressure; WC, waist circumference. Note: a Data was presented as mean ± SD for normal distribution. b Data was presented as median ± IQR for skewed distribution.
one parent or both parents were more likely to develop hypertension (OR, 1.28; CI 1.01-1.61, and OR, 2.24; CI 1.09-4.61, respectively), adjusted for sex, age, BMI, parents' age, and educational qualifications, compared with children and adolescents whose parents had no history of hypertension. 18 However, other studies have reported the opposite. 19,20 A school-based study from Turkey including 2166 students aged 6-15 years found that a positive FH of hypertension was not associated with hypertension in children. 19 Another Chinese casecontrol study including 3266 students aged 11-16 years also found no association between FH in parents and hypertension in univariate and obesity-stratified analyses. 20 The discrepancies of these findings may be caused by methodological differences, including the vari- Together, our studies suggest that genetic factors may play a role in inter-individual susceptibility to high BP prior to the onset of obesity.
FH captures the overt results of shared genetics (common and rare genetic variants) and shared environmental risks (ie, dietary intake) among family members. Therefore, with this modulatory effect of obesity in mind, patients with elevated BP and normal weight may become the novel targets of future studies to explore the genetic variants of hypertension.
The study has some limitations. First, FH data were collected from self-reported questionnaires and were not objectively measured. Second, confounding factors, such as diet, physical inactivity, and socioeconomic status, that are well-established risk factors for hypertension, were not adjusted for in our study. Third, BP measurements were based on a single visit, which may be responsible for the higher prevalence of high BP observed in our study. Ideally, elevated BP must be confirmed on repeated measures before a child is diagnosed with hypertension.

CONCLUSION
Early routine screening for pediatric hypertension should be performed in adolescents with a BMI classification of overweight or obesity. Furthermore, adolescents with a normal BMI and a positive FH involving their parents should be paid for ample attention in routine prevalence screening. Our findings provided evidence that FH of EH in parents played a significant role in predicting the hypertension phenotype among adolescents with normal weight.