How are body weight and changes in body weight associated with hypertension risk in youths at the higher end of normal weight?

By Pooja Toshniwal PahariaReviewed by Danielle Ellis, B.Sc.Mar 17 2023

In a recent study published in JAMA Network Open, researchers investigated the risk of hypertension among young individuals with body weight near the upper limit of normal body mass index (BMI).

Background

Hypertension in childhood can continue during adulthood and is related to cardiovascular damage, including arterial wall thickening, increased stiffness of arteries, and reduced functioning of endothelial cells. Studies have reported that childhood hypertension-induced damage to target organs may be irreversible. Irrespective of blood pressure readings during adulthood, preventing persistent childhood hypertension and related target organ injury is essential.

Obesity is considered a potent alterable risk factor for pediatric hypertension. However, the relationship between high normal weight and hypertension risk has not been well-characterized. Strategy development and policy-making for managing hypertension could be significantly improved if determined.

About the study

In the present study, researchers evaluated the risk of incident hypertension among children having body weight near the upper limit of the normal weight range at study initiation. The study differentiated between hypertension risk related to baseline weight and that linked to weight gain with time.

The study comprised 801,019 individuals aged three top 17.0 years, registered with Kaiser Permanente Southern California (KPSC) healthcare system between 1 January 2008 and 28 February 2015. Participants were followed up for ≤5.0 years, up to the incidence of pregnancy, hypertension, death, termination of KPSC health care coverage, or end of the follow-up period.

Data were analyzed between 2018 and 2022 for the prime outcome of new-onset and sustained hypertension. The baseline gender-specific body mass index values for individual age and changes in distances from the median value of body mass index for age were compared at the follow-up of the study participants. Cox proportional hazard-type regression modeling was performed, and hypertension's adjusted hazard ratios (aHR) and incident rates (IRs) were calculated.

Participant age was used to evaluate the risk of hypertension from three consecutive visits, using the 2017 American Academy of Paediatrics guidelines on blood pressure. Data was obtained from the participant's electronic health records (EHRs) and was adjusted for ethnicity, sex, race, socioeconomic status, year at baseline, and year of birth.

The range of normal weight was divided into low (between the 5th and 39th percentiles), medium (between the 40th and 59th percentile), and high (between the 60th and 84th percentiles) to provide insights into hypertension risks at body weight below the cut-off for being overweight. Individuals were excluded if their weight or blood pressure measurements were missing or if they suffered from pre-existing hypertension or any medical condition affecting blood pressure and/or growth.

Digital devices and sphygmomanometers were used to measure blood pressure at KPSC and clinics, respectively. Hypertension was diagnosed based on the International Classification of Diseases, ninth revision (ICD-9) codes 362.11 and 401-405, and ICD-10 codes H35.039, I10-I13, I15.0, and I15.8, and antihypertensive drug prescriptions. A sensitivity analysis was performed by using the initial occurrence of blood pressures representing stages I and II of hypertension, or single independent visits with hypertension diagnosis, as events.

Results

The mean participant age was nine, and 51% (n=409,167) were female. Among the participants, 7.0% were Pacific Islander and Asian, 8.0% were Black, and 53% were Hispanic. Compared to children having an initial body mass index between the 40th and 59th percentiles, an aHR value of 1.3 was obtained for hypertension over five years, or for those with baseline body mass index in the 60th to 84th percentiles, whose weight remained stable with advancing age.

With each unit increase in distance from the median body mass index for participant age annually, the aHR values elevated by 1.0. Among participants with baseline body mass index at ≥97th percentile, and stable body weight, an aHR of 4.9 was observed. An increase in weight elevated hypertension risk related to the baseline body mass index in the ≥97th percentile for the age group, and the aHR value was 1.0 per unit elevation in the distance from the median body mass index for age annually.

The risk of hypertension related to increased body weight was greater among individuals weighing within the normal reference range and among those who were overweight than severely obese individuals. During the mean follow-up duration of 4.5 years, 24,969 individuals were identified with new-onset hypertension (IR 7.0 for every 1,000 individual years).

The IR rates for every 1,000 individual years were greater for males (IR 8.5) than females (IR 5.5) and young individuals with state-subsidized healthcare plans (IR 7.9) than the youths without such plans (IR 6.7). Rates were greatest for Whites (IR 7.2) and Hispanics (IR 7.2) compared to others. The incident rates were comparable among individuals who were underweight or had low normal body weight but showed a gradual increase with the increase in body mass index for age.

Conclusions

Overall, the study findings showed that a baseline body weight near the upper limit of normal body weight (60th to 84th percentiles of body mass index for age) was related to an elevated risk of hypertension. This was compared to weight ranging between the 40th and 59th percentiles of body mass index for age. The hypertension risk was 26.0% greater if body weight remained stable at follow-up.

Even modest increases in the body mass index for the age percentile near the upper limit of normal body weight might increase hypertension risks among pediatric individuals. In turn, it increases with excessive weight gain with time. The current normal body weight range from the 5th to the 84th percentile of body mass index for age among children might be too wide and requires re-evaluations concerning the risk of medical disorders. Future studies must assess the weight range regarded as normal for children and the health risks linked to greater normal weight.