In the past two decades several community intervention studies designed to lower the risk of cardiovascular disease in populations have been completed. These trials shared the rationale that the community approach was the best way to address the large population attributable risk of mild elevations of multiple risk factors, the interrelation of several health behaviors, and the potential efficiency of large-scale interventions not limited to the medical care system. These trials also shared several threats to internal validity, especially the small number of intervention units (usually cities) that could be studied. The purpose of this paper is to reflect on the lessons learned in one of the studies, the Stanford Five-City Project, which began in 1978. The anticipated advantages were observed, including the generalizability of the intervention components, the potential for amplification of interventions through diffusion in the community, and the efficiency of the mass media and other community programs for reaching the entire population. Numerous components of the intervention proved effective when evaluated individually, as was true in other community studies. However, the design limitations proved difficult to overcome, especially in the face of unexpectedly large, favorable risk factor changes in control sites. As a result, definitive conclusions about the overall effectiveness of the communitywide efforts were not always possible. Nevertheless, in aggregate, these studies support the effectiveness of communitywide health promotion, and investigators in the field should turn to different questions. The authors have learned how little they know of the determinants of population-level change and the characteristics that separate communities that change quickly in response to general health information from those that do not. Future studies in communities must elucidate these characteristics, while improving the effectiveness of educational interventions and expanding the role of environmental and health policy components of health promotion.
This paper examines the effects of community-wide health education on diet-related knowledge and behavior and on plasma cholesterol levels during an experimental field study in medium-sized cities in northern California. Samples of the population aged 12-74 years were drawn at baseline and every 2 years thereafter to obtain four cross-sectional surveys; participants aged 25-74 years are included in this paper (n = 6,814 or about 425 per city per survey). The baseline sample was asked to return to three follow-up surveys, also 2 years apart, constituting the cohort survey sample (n = 777). Diet was assessed by 24-hour recalls. In the serial cross-sectional survey samples, nutritional knowledge increased over time in both men and women in all cities; among women, this increase was significantly greater in the treatment cities. Plasma cholesterol declined significantly only in men and in neither sex was there evidence of a larger decline in treatment than in control cities. Dietary saturated fat intake tended to decline, but not significantly in either sex, and there was no evidence of treatment impact. Dietary cholesterol intake declined in both sexes. Results in the cohort samples were similar, except plasma cholesterol levels were unchanged over time in men and increased in women, and dietary saturated fat intake declined significantly among women. Secular improvements in knowledge of nutrition and in dietary cholesterol intake occurred during the early 1980s in both men and women in these four cities, while there was less consistent improvement in dietary saturated fat intake. Only nutritional knowledge among women achieved greater improvement in treatment cities than in control cities. Continued and greater change in nutrition probably requires more sustained effort and broader methods, including changes in the food supply.
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