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Community intervention trials: reflections on the Stanford Five-City Project Experience.

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.