AHA 2020 Goals for Children and Adolescents -- Don’t Let Perfect Be the Enemy of Good

Although mortality from heart disease has declined over the past decade, heart disease remains the leading cause of death in the US, and cardiovascular disease is projected to affect 23.6 million people worldwide by 2030.1 We have made some progress in addressing contributors to cardiometabolic disease in the US adult population, notably a decline in the prevalence of some risk factors (smoking and hypercholesterolemia) and stabilization in others (obesity and hypertension); however, the prevalence of hyperglycemia is on the rise.1, 2 Cardiometabolic consequences of obesity, poor diets and inactivity remain an important issue, as reflected in the fact that 82% of US adults have less than ideal CV health;1 thus the population as a whole remains at risk for future cardiovascular disease.

In an effort to move the needle on cardiovascular disease, in 2010 the AHA set as an overarching goal “by 2020, to improve the cardiovascular health of all Americans by 20% while reducing deaths from cardiovascular disease and stroke by 20%”.3 Seven key drivers of cardiovascular outcomes were identified including four health behaviors – smoking, obesity, diet and physical activity, and three health factors - lipids, blood pressure, and fasting glucose. Ideal, intermediate and poor categories were defined for “Life’s Simple 7” as a way to describe and track the cardiovascular health of an individual and the population (Table 1). By using this strategy, the AHA has tried to create a paradigm shift to re-orient thinking towards improving health, and away from a focus on treating disease.

In a parallel process, a body of work has emerged that describes the concept of ideal CV health. Exploring these concepts in longitudinal cohorts reveals that once lost, ideal CV health is difficult to regain.4 However, individuals who are able to maintain ideal CV health into middle age have a low risk of lifelong CV disease events.5 These concepts are particularly important for youth as - at least in theory - most children start out with ideal cardiovascular health. Unfortunately, national data show that by age 11 years no children met ideal criteria in four cardiovascular categories, blood pressure, weight, diet and total cholesterol,6 and rates of ideal cardiovascular health decline further over the first and second decades.1 Thus it appears the seeds of cardiovascular disease are sown in childhood.

Five years after the publication of the AHA 2020 goals, Drs. Steinberger et al. have written a scholarly manuscript that surveys the state of cardiovascular health in US youth using the framework of the 2020 goals, explores issues of puberty, and identifies evidence gaps in the cardiovascular health of youth (Steinberger et al. Circulation 2016). This statement helps illuminate opportunities for intervention to improve the cardiovascular health of children and adolescents in the U.S.

The writing group describes that with the notable exception of the healthy diet score, the majority of US children and adolescents score in the ideal range for Life’s Simple 7, but argues that the population remains vulnerable to adverse health effects that are not completely captured by the metrics. For example, rates of current smoking among adolescents are declining;7 however, one third of adolescents have tried a cigarette in the prior month (Steinberger et al. Circulation 2016) and 4.8 million children under 12 are exposed to second-hand smoke in their homes, an exposure known to be associated with sub-clinical measures atherosclerosis (AHA pediatric SHS statement, unpublished). The prevalence of non-ideal weight, as defined in the AHA 2020 goals as ≥85th%tile, has stabilized,8 yet still 40-48% of teens have non-ideal BMI and the rates of severe obesity continue to climb, particularly in girls.9 Measuring physical activity by self-report suggests two-thirds of boys and half of adolescent girls meet the goal of 60 or more minutes per day of moderate to vigorous intensity physical activity including muscle strengthening and bone-loading activities at least 3 days per week.10 However, measured physical activity (by accelerometry) shows a different picture, with under half of school-aged children boys and a third of school-aged girls meeting the mark for ideal levels of physical activity. By age 16-19 years, only 5-10% manage an hour a day of physical activity 5 days a week (Steinberger et al. Circulation 2016). A healthy diet is the metric U.S. children and adolescents are least able to achieve. Less than 1% of 2-19 year olds meet the criteria for an ideal diet and ~80% of youth have what the AHA metrics describe as a poor diet.1 Fortunately there has been some improvement over time, with an increase in the proportion of children falling in the intermediate diet score, from 31% to 45%.7

Similar issues are identified in the three cardiovascular risk factors, cholesterol, blood pressure and glycemia. Ideal cholesterol levels, defined as TC<170 mg/dL, are present in 65-73% of US youth. However, HDL, an important indicator of CV health is not reflected in the TC metric and in fact the prevalence of high non-HDL is higher than that of high TC, suggesting that looking at TC alone may miss higher risk youth.11 Furthermore, TC levels decrease during puberty, so using a single measure across all of childhood may miss higher risk adolescents. Non-ideal blood pressure, defined as ≥90th%tile, is the cardiovascular health metric most likely to be met by the pediatric population (89% are in the ideal category).11 Non-ideal blood glucose (≥100 mg/dL) is seen in 20-38% of children, with boys being more affected. However, this is a single measure in time and is affected by fasting status; arguably its utility is limited and glycosylated hemoglobin could better convey abnormal glucose homeostasis over time.

The AHA 2020 goals for youth would benefit from refinement, as would be expected for any set of national health metrics, and Steinberger et al. suggest factors to consider. For example, exposure to 2nd hand smoke and use of electronic smoking should be included in the smoking risk score. The adiposity measure could be narrowed to focus on obesity and extreme obesity and not include “overweight”. A better choice for the cholesterol metric might be non-HDL as it better represents the atherogenic portion of the lipid profile. Hemoglobin A1C could better represent exposure to hyperglycemia over time. Physical activity should focus on measured as opposed to self-reported activity. These targets should be evidenced based.

Permeating the topic of ideal cardiovascular health in youth, and in fact the entire field of pediatric prevention, is the issue of evidence. Policy makers, researchers, and guideline writers raise concerns about gaps in the existing evidence and about the types of studies available to justify recommendations about cardiovascular risk in youth. Evidence gaps include issues of implementation of healthy lifestyle behaviors, and about how to maintain heart healthy behaviors over the long term. Future research should include bigger sample sizes in racially and ethnically diverse populations, and should include young children less than 5 years old. While the impact of extreme cardiovascular risk behaviors and risk factors (e.g. familial hypercholesterolemia, severe hypertension, diabetes) has been studied, how mild or moderate abnormalities affect risk is a relatively unexplored area. In addition to gaps in evidence, there are issues about evidence quality. The research gold standard, the randomized controlled trial using clinically important outcomes (cardiovascular events), is not likely to be realized in the pediatric population because the time to event is so long, the event rate is low, and because of issues surrounding consent of children for long term follow-up. Different methodologies must be considered to choose clinically meaningful cutpoints for intervention and to investigate the utility of interventions to change behaviors and risk factors. Ultimately a wider range of evidence will need to be used to address the field of pediatric prevention.

Fortunately, high quality studies can inform these issues. For example, rigorous feeding studies can test the effect of diet on cardiovascular risk factors and preclinical vascular measures. Accelerometers and direct observation can better quantify the dose of activity levels than self-report and new technologies can help solve logistical issues around measuring physical activity. In many areas, observational data, long-term cohorts, and the use of pre-clinical outcomes should continue to be used to address questions of pediatric prevention, but high quality methodology must be used. Adequate funding is required to do these studies well, and federal and foundation sources will need to dedicate adequate resources to pediatric prevention if we are going to advance the cardiovascular health of the nation.

While we are gathering the highest quality evidence to preserve ideal cardiovascular health, we need to go on with the tasks of assessing the health of our population, providing recommendations about diet, physical activity, and health-related policy and advising to our patients in the clinic. Fortunately, actions to improve risk factors and risk behaviors are, for the most part, low risk. Few young people meet the current guidelines for pharmacotherapy12-15 and healthy lifestyle behaviors have diverse benefits not only for cardiovascular health but also for cancer prevention, brain and physical development, and prevention and amelioration of mental health disorders. As described in this statement, the 2020 goals for children and adolescents are an important tool for measuring the cardiovascular health of the population and for promoting health at the national, community, family and individual level

Table 1: Poor, Intermediate, and Ideal definitions: Health metrics in children and adolescents