Attention to Contextual Issues That Influence Interventions

While numerous authors have written about the role of context in informing evidence-based practice and policy, there is little consensus on its definition. When moving from clinical interventions to population-level and policy interventions, context becomes more uncertain, variable, and complex (Dobrow et al., 2004). One useful definition of context highlights information needed to adapt and implement an evidence-based intervention in a particular setting or population (Rychetnik et al., 2004).

The context for questions on how to implement an obesity-related intervention involves five overlapping domains. First is characteristics, such as level of education, of the target population. Second, interpersonal variables provide important context; for example, a person who comes from a family that exercises together may have a lower risk of developing obesity. Third, organizational variables should be considered, such as how an agency’s capacity (e.g., a trained workforce, agency leadership) may influence its success in carrying out an evidence-based obesity prevention program (Dreisinger et al., 2008; Hausman, 2002). Fourth, social norms and culture are known to shape many health behaviors. Finally, larger political and economic forces affect context; for example, a high rate of obesity may influence a state’s political will to address the issue in a meaningful and systematic way.

Particularly for high-risk and understudied populations, there is a pressing need for evidence on obesity prevention in relation to contextual variables and ways of adapting programs and policies across settings and population subgroups. Contextual issues are being addressed more fully in the new “realist review” approach—a systematic review process that involves examining not only whether an intervention works but also how it works in real-world settings (Pawson et al., 2005). This enhanced understanding of context is a key theme of a systems approach (see Chapter 4). Well-reasoned recommendations have emerged from many quarters to replace the hierarchy of evidence-based medicine with a systems approach to garnering, analyzing, and appraising evidence when addressing complex public health problems such as obesity prevention (Briss et al., 2000; Brownson et al., 2003; Green and Glasgow, 2006; Harris, 2000; McKinlay, 1992; Petticrew and Roberts, 2003; Rychetnik et al., 2004; Swinburn et al., 2005). There are several reasons for this shift.

First, unlike medical therapies focused on individual patient care, obesity prevention interventions are typically mounted on a relatively large scale and focus on health issues affecting communities at large (at the regional, national, or even global level). Causal pathways to population outcomes do not involve the straightforward, patient-level treatment-to-outcome linkages typically tested in trials of medical therapies.

Second, obesity prevention interventions frequently comprise multiple components operating at different levels of society. In a typical example, a legislative action at the highest level (e.g., a state action on mandatory nutrition labeling) may be combined with health campaigns and education programs administered at the community

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