Abstract
Background/Aims There are a number of recent large-scale community-level initiatives targeting obesity prevention that focus on policy and environmental change strategies. To help evaluate the impact of these initiatives 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. We provide a definition and examples of measuring population dose and show how the concept was used in an evaluation of the Kaiser Permanente’s Healthy Eating, Active Living Community Health Initiative in Northern California (HEAL-CHI).
Methods HEAL-CHI was a community initiative designed to reduce obesity by implementing community- and organizational-level policy and environmental changes in three low-income communities in Northern California. Population dose was defined 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 used a three-level rating system to assess the strength of each intervention strategy, combining evaluation results with estimates of intensity. We then examined data from youth surveys to assess whether population-level changes from the youth surveys were greater where high- dose strategies were present.
Results The HEAL-CHI population-level results were inconclusive overall, but showed positive and significant findings for four of the nine youth survey comparisons where “high dose” strategies were implemented, primarily physical activity interventions targeting elementary and middle school-age youth. For example, the percent of children reporting exercising at least 20 minutes per day increased from 61% to 67% in a community implementing a high-dose after-school physical activity program, a statistically significant (p<.05) increase relative to comparison schools.
Discussion The concept of population dose provides a way of comparing the potential community impact of different obesity prevention strategies and combining the estimates from multiple strategies to get an estimate of cumulative impact. In addition, we found that for the HEAL-CHI communities where there were high dose strategies in place there were a number of significant and positive population-level behavior changes.
