Policy Implementation Science - An Unexplored Strategy to Address Social Determinants of Health.

This commentary explores the ways in which robust research focused on policy implementation will increase our ability to understand how to - and how not to - address social determinants of health. We make three key points in this commentary. First, policies that affect our lives and health are developed and implemented every single day, like it or not. These include "small p" policies, such as those at our workplaces that influence whether we have affordable access to healthy food at work, as well as "large P" policies that, for example, determine at a larger level whether our children's schools are required to provide physical education. However, policies interact with context and are likely to have differential effects across different groups based on demographics, socioeconomic status, geography, and culture. We are unlikely to improve health equity if we do not begin to systematically evaluate the ways in which policies can incorporate evidence-based approaches to reducing inequities and to provide structural supports needed for such interventions to have maximal impact. A policy mandating physical education in schools will do little to address disparities in fitness and weight-related outcomes if all schools cannot provide the resources for physical education teachers and safe activity spaces. Second, as we argue for an increased emphasis on policy implementation science, we acknowledge its nascent status. Although the field of implementation science has become increasingly robust in the past decade, there has been only limited application to policy. However, if we are strategic and systematic in application of implementation science approaches and methods to health-related policy, there is great opportunity to discover its impact on social determinants. This will entail fundamental work to develop common measures of policy-relevant implementation processes and outcomes, to develop the capacity to track policy proposal outcomes, and to maximize our capacity to study natural experiments of policy implementation. Third, development of an explicit policy implementation science agenda focused on health equity is critical. This will include efforts to bridge scientific evidence and policy adoption and implementation, to evaluate policy impact on a range of health equity outcomes, and to examine differential effects of varied policy implementation processes across population groups. We cannot escape the reality that policy influences health and health equity. Policy implementation science can have an important bearing in understanding how policy impacts can be health-promoting and equitable.