Applying the concept of “Population Dose” in planning and evaluating community health initiatives

There are a number of recent large-scale community-level initiatives targeting obesity prevention. These initiatives typically involve a portfolio of strategies at multiple levels (e.g., individual, family, community) across multiple sectors (e.g., school, worksite, neighborhood). It is useful for both planning and evaluation purposes to have a quantitative estimate of the impact of individual obesity prevention strategies. We have created a measure of estimated strategy-level impact that we refer to as "population dose" that provides an overall estimate of the impact of a strategy on food and physical activity behaviors. Population dose is defined, similar to RE-AIM, as the product of reach (number of people exposed to an intervention strategy) and strength (change in behavior for each person reached). Since quantitative effect sizes for policy and environmental change interventions are generally unavailable, we use a rating system based on intervention intensity and frequency of exposure to assess the strength of each intervention strategy. We will present population dose results, including estimates of the validity and reliability of the strength ratings, for three communities that are part of Kaiser Permanente's Healthy Eating, Active Living Community Health Initiative in Northern California (HEAL-CHI). In addition, we will present results showing the relationship between the combined dose of strategies targeting specific outcome measures (e.g., minutes of physical activity) and population-level measures assessing those outcomes. Our results suggest that population-level intervention effects were greater where high-dose strategies were present.