Observational studies may be more important than randomized clinical trials: weaknesses in US Preventive Services Task Force recommendation on blood pressure screening in youth

What Level of Blood Pressure Is Concerning in Childhood?

The 95th percentile of blood pressure (BP) among healthy children is the currently accepted level used to denote a hypertensive BP reading in pediatric patients. Yet, ample data have emerged showing that the detrimental effects of high BP can be demonstrated at BP levels considered normal by current guidelines. Cardiac, vascular, cognitive, and kidney effects have been shown starting at the 90th percentile in cross-sectional studies, and markers of adult cardiovascular disease appear in longitudinal cohorts whose members had modestly elevated or even normal BP as youth. This review summarizes data that support a lower threshold of concern for children and adolescents, and outlines some of the remaining questions to be answered before a lower threshold BP level could be adopted.

The predictive value of repeated blood pressure measurements in childhood for cardiovascular risk in adults: the Hanzhong Adolescent Hypertension Study

There is currently a lack of strong evidence linking childhood elevated blood pressure to long-term cardiovascular risk in adulthood. Repeated observations of abnormal blood pressure in childhood may enhance the prediction of cardiovascular risk in adulthood compared with a single observation. The study included 1738 individuals in rural areas of Hanzhong City, Shaanxi, who had been followed for 30 years since baseline (1987, at which time participants were aged 6-15 years). According to four independent measurements of blood pressure in 1987, 1989, 1992, and 1995, childhood elevated blood pressure was defined as 2 in-person examinations with blood pressure values above the 90th percentile. Arterial stiffness and left ventricular hypertrophy in adulthood were assessed by brachial-ankle pulse wave velocity and the Cornell product index, respectively. Childhood elevated blood pressure was associated with an increased risk of adult hypertension (OR, 2.01; 95% CI, 1.53-2.65), arterial stiffness (OR, 1.69; 95% CI, 1.32-2.16) and left ventricular hypertrophy (OR, 1.86; 95% CI, 1.13-3.05) (all P < 0.05). Cardiovascular risk in adults increased with increasing childhood blood pressure levels. In addition, two abnormal childhood blood pressure observations predicted an increased likelihood of hypertension in adulthood (0.77 for 2 versus 0.70 for 1 observation, P < 0.001). Our study provides strong evidence that elevated blood pressure in childhood predicts cardiovascular risk in adults. The prediction was enhanced by two observations of abnormal blood pressure in childhood compared with a single measurement. We emphasize the importance of childhood blood pressure monitoring and control in the prevention of cardiovascular diseases.

High blood pressure in the young: why should we care?

While primary hypertension (HTN) clearly occurs in children and adolescents, the approach of many providers to such patients can best be described as ambivalent: the condition may be recognised, but is not acted upon. Such ambivalence may stem from incomplete understanding of the effects of high blood pressure in the young, which in turn is related to the shortage of information on long-term outcomes of primary childhood HTN. However, other evidence on the short- and long-term effects of blood pressure elevation in childhood clearly shows that it is not a benign condition at all.

CONCLUSION

Childhood HTN warrants action to prevent adult cardiovascular disease.

Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents

These pediatric hypertension guidelines are an update to the 2004 "Fourth Report on the Diagnosis, Evaluation, and Treatment of High Blood Pressure in Children and Adolescents." Significant changes in these guidelines include (1) the replacement of the term "prehypertension" with the term "elevated blood pressure," (2) new normative pediatric blood pressure (BP) tables based on normal-weight children, (3) a simplified screening table for identifying BPs needing further evaluation, (4) a simplified BP classification in adolescents ≥13 years of age that aligns with the forthcoming American Heart Association and American College of Cardiology adult BP guidelines, (5) a more limited recommendation to perform screening BP measurements only at preventive care visits, (6) streamlined recommendations on the initial evaluation and management of abnormal BPs, (7) an expanded role for ambulatory BP monitoring in the diagnosis and management of pediatric hypertension, and (8) revised recommendations on when to perform echocardiography in the evaluation of newly diagnosed hypertensive pediatric patients (generally only before medication initiation), along with a revised definition of left ventricular hypertrophy. These guidelines include 30 Key Action Statements and 27 additional recommendations derived from a comprehensive review of almost 15 000 published articles between January 2004 and July 2016. Each Key Action Statement includes level of evidence, benefit-harm relationship, and strength of recommendation. This clinical practice guideline, endorsed by the American Heart Association, is intended to foster a patient- and family-centered approach to care, reduce unnecessary and costly medical interventions, improve patient diagnoses and outcomes, support implementation, and provide direction for future research.

Performance of Eleven Simplified Methods for the Identification of Elevated Blood Pressure in Children and Adolescents

The identification of elevated blood pressure (BP) in children and adolescents relies on complex percentile tables. The present study compares the performance of 11 simplified methods for assessing elevated or high BP in children and adolescents using individual-level data from 7 countries. Data on BP were available for a total of 58 899 children and adolescents aged 6 to 17 years from 7 national surveys in China, India, Iran, Korea, Poland, Tunisia, and the United States. Performance of the simplified methods for screening elevated or high BP was assessed with receiver operating characteristic curve (area under the curve), sensitivity, specificity, positive predictive value, and negative predictive value. When pooling individual data from the 7 countries, all 11 simplified methods performed well in screening high BP, with high area under the curve values (0.84-0.98), high sensitivity (0.69-1.00), high specificity (0.87-1.00), and high negative predictive values (≥0.98). However, positive predictive value was low for most simplified methods, but reached ≈0.90 for each of the 3 methods, including sex- and age-specific BP references (at the 95th percentile of height), the formula for BP references (at the 95th percentile of height), and the simplified method relying on a child's absolute height. These findings were found independently of sex, age, and geographical location. Similar results were found for simplified methods for screening elevated BP. In conclusion, all 11 simplified methods performed well for identifying high or elevated BP in children and adolescents, but 3 methods performed best and may be most useful for screening purposes.

Pediatric Blood Pressure and Adult Preclinical Markers of Cardiovascular Disease

A high blood pressure level in adults is considered the single most important modifiable risk factor for global disease burden, especially those of cardiovascular (CV) origin such as stroke and ischemic heart disease. Because blood pressure levels have been shown to persist from childhood to adulthood, elevations in pediatric levels have been hypothesized to lead to increased CV burden in adulthood and, as such, might provide a window in the life course where primordial and primary prevention could be focused. In the absence of substantive data directly linking childhood blood pressure levels to overt adult CV disease, this review outlines the available literature that examines the association between pediatric blood pressure and adult preclinical markers of CV disease.

Recent clinical and translational advances in pediatric hypertension

Epidemiological reports describe a child population increase in BP level and an increase in prevalence of hypertension, that is largely, but not entirely, driven by a concurrent increase in childhood obesity. Given current estimates, ≈10% of adolescents have hypertension or prehypertension. In addition to obesity, dietary salt intake and waist circumference, a marker of visceral obesity, are found to be independently associated with the rise in BP among children and adolescents. Dietary salt intake in urban children is well above recommended levels largely because of consumption of processed and fast foods. Childhood exposures, such as stress,52 salt, and fructose, as well as lifestyles, including food sources, sleep patterns, and reductions in physical activity may have a role in obesity-high BP associations. In addition, clinical and translational evidence is mounting that intrauterine exposures alter can effect changes in fetal development that have an enduring effect on cardiovascular and metabolic function later in life. These effects can be detected even in children who are products of a term otherwise normal pregnancy. Hypertension in childhood has been defined statistically (BP ≥ 95th percentile) because of lack of outcome data that links a BP level with heightened risk for future cardiovascular events. Therefore, primary hypertension had been considered a risk factor for later hypertension in adulthood. Intermediate markers of TOD, including cardiac hypertrophy, vascular stiffness, and increases in cIMT, are detectable in adolescents with primary hypertension. Evidence that vascular injury is present in the early phase of hypertension and even in prehypertension warrants consideration on the current definition of pediatric hypertension. With further studies on TOD and other risk factors in addition to high BP, it may be possible to shift from a statistical definition to a definition of childhood hypertension that is evidence based. Preventing or reducing childhood obesity would have substantial benefit in countering the documented increase in BP levels and prevalence of high BP in childhood. Weight control in overweight and obese children, along with dietary changes 53 and increases in physical activity,54 has benefit on BP levels in childhood. Prevention of childhood obesity and BP risk will require multiple levels of intervention, including public health, health policy, and attention to food supply to foster the necessary lifestyle changes to prevent and reduce childhood obesity.