Cardiovascular Health in US Adolescents

A major component of the American Heart Association’s (AHA) Strategic Impact Goal through 2020 and beyond is the promotion of ideal cardiovascular health across the life course.1 Central to this AHA goal are data indicating that individuals who maintain optimal levels of established risk factors for cardiovascular disease (CVD) through adult life have dramatically lower lifetime CVD risk and markedly longer survival than do their adult counterparts who developed 1 or more risk factors earlier in life.2–4 Additional recent evidence from the Cardiovascular Risk in Young Finns Study, an ongoing population-based prospective study, indicates that the presence of adverse levels of risk factors for CVD during adolescence strongly influences adult risk for CVD.5–7 Taken together with 4 decades of clinical and epidemiologic evidence that documents the impact of risk factors and adverse health behaviors on cardiovascular structure and function beginning early in life, these results underscore the importance of primordial prevention and lifelong ideal cardiovascular health.8 The AHA’s operational definition of ideal cardiovascular health is stratified by age (children, adults) and includes 4 health behaviors (current smoking, body mass index, physical activity, and healthy diet) and 3 health factors (total cholesterol, blood pressure, and fasting plasma glucose).1 Recognizing the importance of ideal cardiovascular health in adolescence and in the absence of nationally representative prevalence estimates, Shay and colleagues9 examined its components in 4673 participants aged 12 to 19 years from the 2005–2010 National Health and Nutrition Examination Surveys (NHANES). Of note, to ensure the nationally representative nature of sampling, NHANES data are collected with the use of a complex, multistage probability design to select participants from strata defined by geography and proportion of minority populations. The analytic sample for this prevalence study represented approximately 33.2 million US adolescents. Population prevalence of individual cardiovascular health behaviors and factors was estimated using AHA criteria for ideal, intermediate, and poor levels.1 For children and youth, ideal (by health behavior and health factor) was operationally defined as follows: smoking status, never tried; body mass index, less than 85th percentile for age and sex; physical activity, 60 minutes or more of moderate or vigorous intensity activity every day; healthy diet, adherence to 4 to 5 components of Healthy Diet Score; total cholesterol level less than 170 mg/dL; blood pressure less than 90th percentile for age and sex; and fasting plasma glucose level less than 100 mg/dL. Results indicated that ideal blood pressure was most prevalent (males, 78%; females, 90%); in contrast, a dramatically low prevalence of ideal Healthy Diet Score was observed (males, <1%; females, <1%). Females exhibited a lower prevalence of ideal total cholesterol (65% vs 72%, respectively) and physical activity (44% vs 67%, respectively) levels; however, females had a higher prevalence of ideal blood glucose level (89% vs 74%, respectively) compared with male counterparts. Of note, approximately two-thirds of adolescents (males, 66%; females, 67%) exhibited ideal body mass index, ascertained by direct measurement of height and weight. Consistent with other reports, however, non-Hispanic black females and Mexican-American males were more commonly overweight or obese compared with their non-Hispanic white counterparts. Overall, ideal smoking status was the most prevalent cardiovascular health component in all sex and race and ethnic groups, with the highest prevalence observed among non-Hispanic blacks. Most important, less than 50% of adolescents exhibited 5 or more ideal cardiovascular health components (males, 45%; females, 50%). Prevalence estimates for these cardiovascular health components according to sex were consistent across race and ethnic groups.9 The results from this population-based prevalence study have both strengths and methodological limitations and should be interpreted accordingly. Although NHANES data offer nationally representative multistage probability samples of free-living US adults, adolescents, and children, the data are cross-sectional and do not allow for examination of temporal changes at an individual level. Important to emphasize and consider in individual clinical evaluations are the natural physiological changes in health factors that occur during the transition from school age to adolescence. For example, total cholesterol levels increase during prepuberty and decrease during early adolescence and have been shown to vary according to Tanner stage of sexual maturation.10 Similarly, annual variations in blood pressure have been observed during this developmental transition.11 Insulin resistance has also been observed to vary with Tanner stage: Insulin resistance increases significantly at stages 2, 3, and 4 but decreases to near prepubertal levels at stage 5.12 On the basis of these observations of developmental variations, the Expert Panel on Integrated Guidelines for Cardiovascular Health and Risk Reduction in Children and Adolescents13 recommended repeated measures of the lipid profile and blood pressure for evaluation of dyslipidemia and hypertension in youth. In addition, as Shay and colleagues9 acknowledge, total cholesterol is used as the sole blood lipid measure in the AHA definition of cardiovascular health. Non–high-density lipoprotein cholesterol levels during adolescence have also been shown to influence the degree of subclinical atherosclerosis during young adulthood14,15 and may provide a more meaningful estimate of CVD risk. Methodological limitations notwithstanding, the results of this NHANES survey highlight the high prevalence of adverse cardiovascular health behaviors in US adolescents, particularly physical activity and dietary intake and the low prevalence of ideal cardiovascular health. Viewed in the context of accumulated data demonstrating associations between risk factors for CVD and adverse health behaviors present in adolescence to CVD risk in adulthood, these NHANES results do not bode well for the cardiovascular health of future generations. Clearly, in addition to individual, clinical approaches to cardiovascular health promotion and risk reduction in children and youth, there is an urgent need for population-based strategies that target health behaviors central to cardiovascular health with emphasis on the environments that influence these behaviors. Cardiovascular nurses and organized nursing are well prepared and positioned to advocate for adoption of the Integrated Guidelines for Cardiovascular Health and Risk Reduction in Children and Youth13 and the multilevel policies necessary to realize ideal cardiovascular health for all US adolescents.