Child and Adolescent Trial for Cardiovascular Health (CATCH)

BACKGROUND:

Coronary atherosclerosis begins in childhood and is expressed in adulthood as angina pectoris, myocardial infarction, or sudden death. The earliest lesion in the vascular system is the fatty streak, characterized by an accumulation of lipids in the intima. These lesions are present in the vessels of infants and young children. Whether these fatty streaks are precursors of more complex lesions is controversial. However, fibrous plaques, intimal lesions consisting of a central core of extracellular lipids covered with a cap of fibromuscular tissue, are frequently seen in children by 15 years of age. In addition, necropsy studies of United States battle casualties confirm the presence of advanced coronary lesions in young adults. Thus, it appears that the atherosclerotic process is well established in the American population by young adulthood.

Epidemiologic studies in adults have found that associated with the development of coronary artery disease are a number of risk factors including age, sex, hypercholesterolemia, hypertension, cigarette smoking, diabetes, a family history of coronary artery disease, obesity, lack of physical activity, and perhaps coronary prone behavior. Of the modifiable factors, hypercholesterolemia, hypertension, and cigarette smoking have the greatest predictive value.

A small reduction of serum cholesterol levels in all children by a modest diet change, it has been hypothesized, would reduce coronary heart disease. More severe dietary restriction, in some cases in conjunction with medication, is recommended for very high-risk pediatric populations only. In addition, surveillance of blood pressure, avoidance of cigarette smoking and overweight, and regular physical exercise are prudent recommendations for all children.

The National Children and Youth Fitness Study (NCYFS) offered new standards for measuring fitness, profiled youth exercise habits, and helped to explain the contribution of exercise to fitness. Nationwide, 8,000 fifth- through twelfth-graders in 140 schools in 19 states participated in the study between February and May 1984. Findings revealed that these youths had substantially more body fat than their counterparts in the 1960's and that approximately half of the students did not perform sufficient physical activity to maintain effective cardiorespiratory functioning. Results from the 1985 national survey of drug use among high school students indicate that most initial experiences with smoking occur before high school, with 13 percent of students beginning prior to tenth grade. Substantial increases in smoking occur between seventh and eighth grade and inner city Hispanic students show higher smoking rates than white or Black inner city youth.

Although there is debate about the cut-off point at which children might be considered at risk for coronary heart disease, it is estimated that 36-60 percent of children in the United States exhibit at least one modifiable risk factor for coronary disease by the age of 12. The nation's schools may provide an appropriate and efficient vehicle for reducing cardiovascular risks in large populations. About 47 million children and young people attend some 115,000 public and private schools. These students are in school from 5 to 8 hours each day, 5 days per week, for nearly 36 weeks per year. Furthermore, the school food services provide 20 percent or more of total daily caloric intake on school days for children who select the school lunch program.

Currently, school-based health promotion programs are conceptualized as including curriculum and related organizational factors that support healthy behavior. The existence of comprehensive programs is limited throughout the nation. The results of numerous school-based nutrition studies report changes in students' knowledge about nutrition. Several studies based on social learning theory report changes in behavior and knowledge about nutrition. Although health education interventions may succeed in increasing children's knowledge and producing changes in behavioral intentions and behavior, the behavioral changes may not be maintained unless the school environment and children's parents reinforce the intentions.

Substantial progress in the field of cigarette smoking prevention in youths has been made during the past few years. Researchers have focused on the prevention of cigarette smoking for several reasons. First, cigarette smoking is a major risk factor for such chronic diseases as coronary heart disease, cancer, and emphysema. Second, cigarette smoking is the most widespread form of drug dependence in our society. Third, cigarette smoking occurs toward the very beginning of the developmental progression of substance abuse and consequently is generally regarded to be one of the so-called 'gateway' substances.

A recent review indicated that the most promising cigarette smoking prevention approaches focus on the psychosocial factors that promote initiation of cigarette smoking. Such approaches fall into two general categories: (a) those that focus on the social influences believed to promote substance use, and (b) those that provide coping skills training designed to enhance personal and social competence. Results of a recent 24-month study involving 689 sixth-grade elementary students showed that youths who received both health information and skills interventions had less intention to smoke and less cigarette use than youths who received no intervention or health information alone. Prior studies using peer-led models with seventh graders report similar results.

The research literature on the effects of physical activity promotion is sparse. One of the few intervention studies on physical activity with school children to report increased endurance fitness and reduced body fat associated with an intensive daily physical program is the Australian Health and Fitness Study. This randomized, controlled trial was designed to compare the effects of integrated physical activity and health education programs on body fat, blood pressure, and endurance fitness in 10-year-old school children in primary schools located in Adelaide. The Oslo Youth Study was successful in designing and implementing within the school system a comprehensive health educational program involving grades 5-7. Positive results were obtained in the intervention group relative to the reference group with reductions in smoking onset, improved eating habits, and increased physical activity over a two-year period.

Over the past ten years, school-based research studies have become more theoretically-grounded and have employed more sophisticated research design strategies and measurement techniques. The prevention of cigarette smoking has been the major focus of this research. There is still considerable need to build the base of scientific knowledge about the development of dietary, smoking, and exercise habits during childhood and about the interventions that are effective in school settings.

DESIGN NARRATIVE:

CATCH consisted of a three-and-a-half year feasibility study conducted from September 1987 through March 1991, the main trial beginning in April 1991, and the Tracking Study, in 1996 a follow-up study to allow measurements on the cohort through ages 13 to 14 years. The purpose of the feasibility study was to test the acceptability of the interventions and measurements in 1,471 third, fourth, and fifth grade boys and girls, ages 7 to 11. The main components of the Phase I intervention programs at the eight schools included classroom curricula for the third, fourth, and fifth grades; home curricula designed to involve parents and children in CATCH activities at home and family fun nights to enhance family involvement; a physical activity program centered around a new physical activity curriculum; and a school nutrition program for school food service directors and staff. Blood samples were obtained from 1,045 children during risk factor screening. Other measurements included blood pressure, height, weight, triceps, and subscapular skinfolds. Nutrient intake was pilot-tested with an interactive 24-hour recall approach, supplemented by food records, a home food inventory, and follow-up calls to parents. Physical activity was measured with a physical activity interview and the Caltrac motion sensor.

The main trial or Phase II, beginning in 1991 and ending in 1994, included two study groups, an Intervention Group and a Control Group, with a total of approximately 8,000 students. The measurement cohort included 5,107 students. The Intervention Group received a school-based program consisting of the CATCH curriculum, the physical education program, the school food service program, and programs to establish smoke-free schools. One-half of the Intervention Group received the same school-based program plus a family-based program. The Control Group received the usual health curriculum of the control schools but none of the CATCH interventions. The primary endpoints at the school level were reduction in fat and saturated fat in school lunches and increased moderate to vigorous activity in PE classes. The primary endpoint at the student level was serum cholesterol change between the third and fifth grades. Secondary endpoints included health knowledge, self-efficacy and behavioral skills that related to the adoption and maintenance of cardiovascular health behaviors; dietary fat intake; dietary sodium intake; physical activity; and systolic blood pressure. The unit of randomization was the elementary school. Schools were recruited for participation and then randomly assigned to the study groups. Twenty-four schools were recruited from each of the four participating field centers for a total of 96 schools. In each center, ten of 24 schools were assigned to the Control Group and 14 to the Intervention Group. Among the 14 intervention schools, seven were randomly assigned to the school-based intervention alone and seven to the school-based and family component. Measures of behavioral outcome and process variables were made during each grade from three through five. Physiological measurements were made at baseline in grade three and at the end of grade five. Final measurements were completed in May 1994. Close-out and final data analysis were conducted in the latter part of 1995 and in 1996. The major results paper was published in JAMA in March 1996. Ten major mainstream papers were published in Preventive Medicine in 1996.

The Tracking Study of CATCH III, beginning in December 1994, followed the cohort through early adolescence in the sixth through eighth grades. The objectives were to measure the effects of CATCH II intervention programs on subsequent smoking prevalence rates during the end of the eighth grade and to observe the onset, development, and inter-correlation of cardiovascular risk factors from early to middle adolescence in the cohort. There were no CATCH interventions. Psychosocial measures, dietary fitness, and smoking data were collected annually. The full panel of physiological measures and biochemical validation of smoking was conducted during the last semester of eighth grade. CATCH III ended in November 1999. The study was active through November 2000 under U01-HL-47098, the coordinating center.

In August of 1996, a homocysteine substudy was added to CATCH. The substudy used serum samples collected in eighth graders in the spring of 1997 for analyses of homocysteine, folic acid, vitamin B-12, vitamin B-6, lipids, lipoproteins, blood pressure, weight and height. A mail survey was conducted to collect data on the children's family history of cardiovascular disease and vitamin supplementation. The results paper was published in JAMA in 1998.

The CATCH-ON Study began in 1998. It's purpose was to assess the degree to which CATCH intervention goals (reduction of fat and saturated fat in school meals, increase in physical activity, no tobacco use, and implementation of the CATCH curriculum) were maintained or institutionalized in the original 56 CATCH intervention schools and in 20 control schools. CATCH-ON was Phase IV that ended March 31, 2001. To determine the influence of secular trends, the outcome measures were also assessed in 12 newly recruited (unexposed) schools. Measures of school climate, teacher and staff characteristics, school turbulence and school facilities and resources were assessed to help explain the variation in the degree of institutionalization in the CATCH intervention and control schools.