March 17, 2008

Keeping Young Hearts Young
By Ellen Coleman, MA, MPH, RD, CSSD
For The Record
Vol. 20 No.6 P. 24

By setting children on the right path toward proper eating habits, we take an important step in ensuring their future well-being.

The average life span has steadily increased in developed countries due to improved nutrition, public sanitation, vaccines, antibiotics, new diagnostic technology, improved trauma response, and better postoperative care. Whereas our great-great-grandparents feared infectious diseases such as tuberculosis, pneumonia, and numerous childhood ailments, we give them little thought. Instead, we live long enough and are prosperous enough to suffer the ravages of chronic illnesses such as diabetes, cancer, and cardiovascular disease (CVD).

Since 1900, CVD has been the No. 1 killer in the United States in every year except 1918, when a worldwide influenza epidemic claimed millions in the prime of their lives. CVDs include coronary heart disease (CHD), stroke, hypertension, and rheumatic heart disease. CVD caused 36.3% of all deaths in 2004, or one of every 2.8 deaths.1

CHD, a type of CVD that usually has no symptoms, killed 452,327 Americans in 2004—one of every five deaths that year. This year, an estimated 700,000 Americans will have a new coronary attack, and approximately 500,000 Americans will have recurrent coronary attacks. Roughly 38% of those who experience a coronary attack in a given year will die from it. Fifty percent of men and 64% of women who died suddenly of CHD had no previous symptoms, according to the American Heart Association (AHA).1

CVD is the result of atherosclerosis, the progressive accumulation of fatty deposits, or plaque, in artery walls. As the narrowing worsens, the blood flow through the artery is decreased. CVD was once thought to be a disease of old age, but increasing evidence suggests it can begin in childhood and that nutrition plays a key role.

Research conducted during the past 30 years indicates that atherosclerotic CVD processes begin early in childhood and are influenced over the course of life by modifiable and nonmodifiable risk factors.2 Results from observational, interventional, and laboratory studies provide convincing evidence of the link between established modifiable CVD risk factors (eg, hypertension, tobacco use, atherogenic lipid profile, and obesity) and accelerated atherosclerotic processes in adolescence and adulthood.3-8

Autopsy studies conducted as part of the Bogalusa Heart Study and the Pathobiological Determinants of Atherosclerosis in Youth Study have demonstrated significant positive associations between modifiable CVD risk factors and the presence and extent of atherosclerotic lesions in the aorta and coronary arteries.3,4

Knoflach and colleagues found that the clustering of multiple risk factors adversely affected carotid intima-media thickness during childhood and adolescence.5 Researchers in the Bogalusa Heart, Muscatine, and Young Finn studies all found that CVD risk factors in childhood were associated with increased carotid intima-media thickness in adulthood.6-8 These data provide overwhelming support for the importance of primary CVD prevention beginning early in life.

The key risk factors that should be addressed in youth to decrease the risk of future CVD include elevated serum cholesterol, hypertension, overweight and obesity, type 2 diabetes, tobacco use, and physical inactivity.2

Cholesterol
The National Cholesterol Education Program (NCEP) Expert Panel has established cut points for acceptable, borderline, and high total cholesterol and low-density lipoprotein (LDL) cholesterol levels for children and adolescents aged 2 to 19. A total cholesterol of less than 170 milligrams per deciliter is acceptable; 170 to 199 milligrams per deciliter is borderline high; and 200 milligrams per deciliter is high. An LDL cholesterol level below 110 milligrams per deciliter is acceptable; 110 to 129 milligrams per deciliter is borderline high; and more than 130 milligrams per deciliter is high.9 Approximately 10% of adolescents between the ages of 12 and 19 have total cholesterol levels exceeding 200 milligrams per deciliter.1

Compared with children in other countries, American children and adolescents have higher blood cholesterol levels and intakes of saturated fat and cholesterol. Children and adolescents with high blood cholesterol (particularly LDL) often come from families with a high CVD incidence among adult members. High blood cholesterol has been demonstrated to aggregate in families as a result of shared environmental and genetic factors.9

Total cholesterol and LDL cholesterol tend to track (maintain the same percentile rank) over time from childhood to young adulthood. In the Muscatine Study, 75% of children aged 5 to 18 with total cholesterol levels above the 90th percentile at baseline went on to have elevated cholesterol levels (200 milligrams per deciliter or higher) at the ages of 20 to 25.10 Bogalusa Heart Study data have shown that roughly 70% of children with elevated total cholesterol in childhood continued to have elevated levels in young adulthood.11 Tracking is relevant to primary prevention due to the potential for identifying children at risk for future CVD.2

Hypertension
Compared with the National Health and Nutrition Examination Survey (NHANES) III, results of the most recent survey indicate that systolic and diastolic blood pressures have increased substantially for all children and youths.12 These higher blood pressures are partially due to the increased incidence of overweight.12,13 The prevalence of hypertension rises progressively with an increasing body mass index (BMI), and approximately 30% of overweight youths have hypertension.1,13

For each incremental increase of 1 to 2 millimeters of mercury in systolic blood pressure, children have a 10% greater risk of developing hypertension in adulthood.14 Tracking from childhood to adulthood tends to be weaker and more inconsistent for blood pressure than for other CVD risk factors due to the natural variability of blood pressure. However, elevated blood pressure in childhood predicted hypertension in young adulthood for participants in the Bogalusa Heart Study.15

The National High Blood Pressure Education Program defines normal blood pressure as a systolic and diastolic blood pressure that is less than the 90th percentile for sex, age, and height. (Tables are provided in the report.) Hypertension is defined as an average systolic or diastolic blood pressure that is greater than or equal to the 95th percentile. Systolic or diastolic blood pressure levels that are between the 90th and 95th percentile indicate prehypertension. Adolescents with blood pressure levels at 120/80 millimeters of mercury or above are considered to have prehypertension even if the reading is below the 90th percentile.16

Children and adolescents with elevated systolic and/or diastolic blood pressure should have a comprehensive assessment of other cardiovascular risk factors. The clustering of CVD risk factors (low high-density lipoprotein cholesterol, elevated triglycerides, hyperinsulinemia, and truncal obesity) has been observed in children with elevated blood pressure.16

Overweight and Type 2 Diabetes
The Centers for Disease Control and Prevention (CDC) has provided age- and gender-specific nomograms for BMI to monitor patterns of growth and define overweight and obesity in youths. A BMI between the 5th and 85th percentile is considered normal weight. The 85th to 95th percentile is considered at risk for overweight, and above the 95th percentile is considered overweight.17

Overweight and obesity in American youths have become major public health challenges. More than 9 million American children and adolescents between the ages of 6 and 19 are overweight.1 Data from the most recent NHANES (2003–2004) study indicate that 17.4% of adolescents aged 12 to 19, 18.8% of children aged 6 to 11, and 14% of preschool children aged 2 to 5 are overweight. The prevalence of overweight children and adolescents has increased significantly between 1999 and 2004.18

Overweight in children and adolescents is associated with a number of comorbidities (atherogenic dyslipidemia, hypertension, left ventricular hypertrophy, insulin resistance, and the clustering of risk factors known as the metabolic syndrome) that increase the risk of developing CVD.2,17

The clinical utility of defining the metabolic syndrome in children and youths, as well as the specific components and cut points, is controversial. However, an estimated 1 million American adolescents meet the Adult Treatment Panel (ATP) III criteria for the metabolic syndrome, with an estimated population prevalence of 4%.19 In overweight children and youths, prevalence estimates range from 30% to 50%.19

The increased prevalence of overweight has also been associated with a dramatic and parallel increase in type 2 diabetes in youths. Although type 2 diabetes was considered primarily a disease of adulthood, it has been observed in adolescents with a BMI above 30—a level considered obese even by adult standards. The prevalence of type 2 diabetes in American adolescents is 4.1 in 1,000 individuals, more than double the prevalence of type 1 diabetes (1.7 in 1,000).17 This is a particular concern with regard to CVD risk, as the NCEP ATP III has identified diabetes in adults as a coronary artery disease risk equivalent.17

The increase in overweight and obesity suggests that CVD may occur earlier in adult life for the current generation of children and adolescents. It underscores the critical importance of primary prevention of overweight and obesity in childhood as part of a comprehensive approach to reduce the risk of future CVD.2,17

Tobacco Use
CDC data indicate that 31.7% of male high school students and 25.1% of female students reported using tobacco in 2005. Furthermore, the prevalence of lifetime, current, and frequent cigarette use among high school students has remained basically unchanged from 2003 to 2005.20 Early adolescence is recognized as a critical period for smoking initiation, as 80% of people who use tobacco begin before the age of 18.2

Although the determinants of smoking initiation are complex and include individual and familial factors, the role of sociological influences and state health education policies cannot be overemphasized. Statewide tobacco control programs have been instrumental in preventing youths from starting to smoke. Unfortunately, overall statewide spending on tobacco prevention and control programs has declined by 28% from 2002 to 2004. These program cuts have been associated with decreased awareness of the antitobacco campaign and a substantial increase in smoking susceptibility in youths.2

Physical Activity
Adverse trends in physical education and patterns of leisure-time physical activity have been documented, particularly among adolescent girls. In 2005, CDC data indicate that only 54.2% of high school students nationwide were enrolled in physical education classes on one or more days of an average school week, and only 33% were enrolled in daily physical education.20 Nationwide, only 35.8% of high school students reported the recommended levels of moderate-to-vigorous physical activity of at least 60 minutes per day at least five days per week. More male students (43.8%) than female students (27.8%) met this recommended level of physical activity.20

According to 2002 CDC data, 61.5% of children between the ages of 9 and 13 did not participate in any organized physical activity during their nonschool hours, and 22.6% did not engage in any free-time physical activity.21

Sedentary behaviors such as television viewing are considered risk factors for obesity in children and adolescents. As reducing television time can be an effective strategy for improving weight, current recommendations limit television viewing and other sedentary behaviors (eg, playing video games) to less than two hours per day.2 However, current national estimates indicate that 37.2% of students watched television at least three hours per day on an average school day.21

Reducing CVD Risk
Children can consume a diet consistent with the AHA 2006 diet and lifestyle recommendations and maintain appropriate growth while lowering their risk for future CVD. Since diet in youth is associated with the CVD occurrence outcomes later in life and lifestyle habits in youth track into adulthood, adoption of a healthy diet and lifestyle is recommended at an early age.22

The AHA recommends a diet relying primarily on fruits and vegetables, whole grains, low-fat and nonfat dairy products, beans, fish, and lean meat for youths aged 2 and older. The AHA statement is consistent with the 2005 Dietary Guidelines for Americans and recommends low intakes of saturated and trans fat, cholesterol, and added sugar and salt; energy intake and physical activity appropriate for the maintenance of a normal weight for height; and adequate intake of micronutrients.23

The 2005 Dietary Guidelines for Americans recommend that children and adolescents engage in at least 60 minutes of moderate-intensity physical activity on most, and preferably all, days of the week.24 The AHA recommends that schools provide and promote participation in physical activity since children and adolescents spend more time at school than anywhere else (except for home). All children and youths should participate in a minimum of 30 minutes of moderate-to-vigorous activity during the school day, including time spent being active in physical education classes. Additional activity should be provided through intramural and interscholastic sports, as well as extracurricular and school-linked community programs.25

School physical education programs should provide ample amounts of moderate-to-vigorous physical activity (eg, 50% of class time) and teach students the motor and behavioral skills needed to engage in lifelong activity. Physical education programs should meet national standards for quality and quantity: 150 minutes per week for kindergarten through eighth grade and 225 minutes per week for ninth through 12th grade. Schools should also promote walking and cycling to school and work with local government to ensure that students have safe routes.25

Conclusion
The primary prevention of CVD should begin in childhood and include cardiovascular health promotion and the reduction of established, modifiable CVD risk factors. All children and adolescents should have a comprehensive assessment of their total CVD risk profile in the healthcare setting. Lifestyle modification (therapeutic lifestyle change) is the cornerstone of CVD risk reduction for youths and considers the specific risk factor(s) identified, severity of risk (eg, overweight vs. morbidly obese), the youth’s age, developmental level, and presence of comorbidities. Therapeutic lifestyle changes emphasize normalization of body weight, healthy patterns of dietary intake, and optimal amounts of physical activity.2

Regardless of CVD risk, healthy lifestyle training is recommended for all youths to promote cardiovascular health, normalize levels of modifiable risk factors, and reduce the risk and burden of CVD in adult life.2

— Ellen Coleman, MA, MPH, RD, CSSD, is a nutrition consultant at The Sport Clinic in Riverside, Calif.

American Heart Association Dietary Strategies for Individuals Over the Age of 2
• Balance dietary calories with physical activity to maintain normal growth.

• Set aside 60 minutes each day for moderate-to-vigorous play or physical activity.

• Eat vegetables and fruits daily and limit juice intake.

• Use vegetable oils and soft margarines low in saturated fat and trans fatty acids instead of butter or most other animal fats in the diet.

• Eat whole grain breads and cereals rather than refined grain products.

• Reduce the intake of sugar-sweetened beverages and foods.

• Consume nonfat or low-fat milk and dairy products daily.

• Eat more fish, especially oily fish, broiled or baked.

• Reduce salt intake, including salt from processed foods.

References
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2. Hayman L, Meininger J, Daniels SR, et al. Primary prevention of cardiovascular disease in nursing practice: focus on children and youth: A scientific statement from the American Heart Association Committee on Atherosclerosis, Hypertension, and Obesity in Youth of the Council on Cardiovascular Disease in the Young, Council on Cardiovascular Nursing, Council on Epidemiology and Prevention, and Council on Nutrition, Physical Activity, and Metabolism. Circulation. 2007;116(3):344-357.

3. McGill HC Jr, McMahan CA, Zieske AW, et al. Effects of nonlipid risk factors on atherosclerosis in youth with a favorable lipoprotein profile. Circulation. 2001;103(11):1546–1550.

4. Berenson GS, Srinivasan SR, Bao W, et al. Association between multiple cardiovascular risk factors and atherosclerosis in children and young adults: the Bogalusa Heart Study. N Engl J Med. 1998;338(23):1650–1656.

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9. National Cholesterol Education Program. Report of the NCEP expert panel on blood cholesterol levels in children and adolescents. NIH Publication No. 91-2732. 1991.

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18. Ogden CL, Carroll MD, Curtin LR, et al. Prevalence of overweight and obesity in the United States, 1999–2004. JAMA. 2006;295(13):1549–1555.

19. Cook S, Weitzman M, Avinger P, et al. Prevalence of a metabolic syndrome phenotype in adolescents: findings from the third National Health and Nutrition Examination Survey, 1988–1994. Arch Pediatr Adolesc Med. 2003;157(8):821–827.

20. Eaton KD, Kann L, Kinchen S, et al. Youth risk behavior surveillance: United States, 2005. MMWR Surveill Summ. 2006;55(5):1-108.

21. Centers for Disease Control and Prevention. Physical activity levels among children
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23. Gidding S, Denision B, Birch LL, et al. Dietary recommendations for children and adolescents: A guide for practitioners: consensus statement from the American Heart Association. Circulation. 2005;112(13):2061-2075.

24. U.S. Department of Health and Human Services, U.S. Department of Agriculture. Dietary Guidelines for Americans 2005, sixth edition. Washington, D.C.: U.S. Government Printing Office; 2005.

25. Pate R, Davis M, Robinson TN, et al. Promoting physical activity in children and youth: a leadership role for schools: a scientific statement from the American Heart Association Council on Nutrition, Physical Activity, and Metabolism (Physical Activity Committee) in collaboration with the Councils on Cardiovascular Disease in the Young and Cardiovascular Nursing. Circulation. 2006;114(11):1214-1224.