BACKGROUND:

The American Indian population, including American Indians and Alaska Natives, totals nearly 1.5 million from over 500 tribes and nearly 300 reservations and Alaska Native villages. Earlier in this century, heart disease was rarely noted in American Indians, but in the past decade, cardiovascular disease has become the leading cause of death in American Indians. Several factors may be responsible for this increase: a decreasing incidence of infectious disease, an increasing incidence of diabetes mellitus, and an increasing incidence of obesity. Previous research on non-Indian populations indicates that obesity is an independent risk factor for cardiovascular disease and that it is associated with increases in other cardiovascular disease risk factors such as high blood pressure, diabetes, and low high density lipoprotein cholesterol levels. The high prevalence of obesity among American Indians, coupled with its role as a risk factor for hypertension, coronary heart disease, and diabetes, suggests that a reduction in the average weight of young American Indians would improve their health. Reduction of the prevalence of obesity in American Indians has been designated as a goal for improving the health of this minority population and reducing health disparities in our nation.

The successful 4-1/2 year feasibility study was followed by the full-scale randomized trial involving 1,700 American Indian elementary schoolchildren. Schools were the unit of randomization.

The initiative was developed as a result of consultations with the NHLBI Ad Hoc Committee on Minority Populations, the Conference on Obesity and Cardiovascular Disease in Minority Populations, and the Indian Health Service. The need for the study was reinforced by the preliminary data from the Strong Heart Study confirming the high prevalence of obesity in American Indians. The initiative was approved by the Clinical Applications and Prevention Advisory Committee in February 1992 and given concept clearance by the National Heart, Lung, and Blood Advisory Council in May 1992.

DESIGN NARRATIVE:

The Feasibility Phase of the trial was completed in 1995. The organizational structure has been established, validation studies to determine an endpoint and formative assessment of the tribe communities was completed. Intervention including classroom curriculum, food service, physical activity family component and for the measurement methods including obesity, physical activity, diet intake, knowledge, attitudes and behavior, and process evaluation were completed.

The full-scale trial started in September 1996. The primary aim was to test the effectivenes of a culturally appropriate school-based intervention that promoted increased physical activity and healthful eating behaviors to prevent obesity in American Indian upper elementary school children. The primary outcome was percent body fat after three years of intervention. The major hypothesis was that intervention would result in an absolute difference of 3 percent body fat between the control and intervention schools. All students enrolled in the second grade in the participating schools during Spring, 1997 participated in the baseline survey. Baseline measurements were performed at the end of second grade so that the intervention could begin at the start of third grade. The intervention lasted for three years. A single cohort of children progressed through third, fourth, and fifth grades. Schools were the unit of randomization. Forty-one schools in four centers were stratified within each field center on median percent body fat (PBF) at the end of second grade using data from the baseline measurement. Schools within a field center were then ranked on median PBF. Once stratified, the coordinating center randomly assigned half the schools within each stratum to intervention (21) and half to control (20).