Building the evidence base for population-level interventions: barriers and opportunities.

Population-level interventions focused on policy, systems, and environmental change strategies are increasingly being used to affect and improve the health of populations. At the same time, emphasis on implementing evidence-based public health practices and programming is increasing, particularly at the federal level. Valuing strategies in the population health domain without the benefit of demonstrated efficacy through highly rigorous methods introduces an inherent tension between planning and acting on the best evidence available, waiting for more rigorous evidence to emerge, as well as exploring innovative ways to evaluate and model evidence-based strategies. This article describes the creation of a resource that helps public health practitioners use current evidence for strategic decision making while building the evidence base for population-level interventions. The resource addresses topics of current discussion in the field of evaluating population-level interventions, including the tension between internal and external validity, the need to include measures of health equity, and the balance between fidelity to the intervention and adaptation to the community context. The resource is intended to advance development of evidence in the field by providing practitioners, project managers, and evaluators with a practical guide for using, reviewing, and adding to the existing evidence base.