“Evidence of effectiveness” can mean different things to different people. Our approach to assessing evidence combines what we know from scientific study and the observations of unbiased experts. Strategies are generally assessed in terms of their effect on the factor(s) that drive health outcomes rather than their effect on health directly (e.g., strategies in the ‘Income’ health factor are assessed for their effect on income, assets, or wealth).
Each reviewed strategy is assigned an evidence rating based on the quantity, quality, and findings of relevant research. When assigning ratings, we place the most weight on studies with designs that demonstrate causality; we consider study quality in conjunction with design. Strategies are rated for their effects on specified outcomes, labeled ‘Expected Beneficial Outcomes.’ Additional potential benefits suggested in our literature review are noted as ‘Other Potential Beneficial Outcomes.'
Our ratings include:
- Scientifically Supported: Strategies with this rating are most likely to make a difference. These strategies have been tested in multiple robust studies with consistently favorable results.
- Some Evidence: Strategies with this rating are likely to work, but further research is needed to confirm effects. These strategies have been tested more than once and results trend favorable overall.
- Expert Opinion: Strategies with this rating are recommended by credible, impartial experts but have limited research documenting effects; further research, often with stronger designs, is needed to confirm effects.
- Insufficient Evidence: Strategies with this rating have limited research documenting effects. These strategies need further research, often with stronger designs, to confirm effects.
- Mixed Evidence: Strategies with this rating have been tested more than once and results are inconsistent; further research is needed to confirm effects.
- Evidence of Ineffectiveness: Strategies with this rating are not good investments. These strategies have been tested in multiple studies with consistently unfavorable or harmful results.
We assess each strategy’s likely effect on racial/ethnic, socioeconomic, geographic or other disparities based on its characteristics (e.g., target population, mode of delivery, cultural considerations, etc.) and best available evidence related to disparities in health outcomes. Strategies are rated:
- Likely to decrease disparities
- No impact on disparities likely
- Likely to increase disparities
Strategies that are likely to reduce differences in health outcomes (i.e., close a gap) are rated ‘Likely to decrease disparities,’ while strategies likely to exacerbate differences are rated ‘Likely to increase disparities.’ Strategies that generally benefit entire populations are rated ‘No impact on disparities likely.’
These ratings reflect usual use of a strategy as presented in relevant literature. However, choosing to implement a strategy in a targeted way can alter its likely impact on disparities. Implementing a strategy rated ‘no impact on disparities likely’ for those with the greatest need, for example, may decrease disparities in your community.
Starting in April 2022, a revised disparity rating will be assigned to each strategy. The revised disparity rating indicates a strategy’s potential impact on disparities and names the strength of evidence supporting the rating (e.g., ‘Potential to decrease disparities: Supported by strong evidence,’ ‘Potential to decrease disparities: Suggested by expert opinion’). The new rating categories include:
- Potential to decrease disparities: Evidence, expert opinion, or intervention design suggests that these strategies have the potential to decrease, or eliminate, disparities between subgroups.
- Potential to increase disparities: Evidence, expert opinion, or intervention design suggests that these strategies have the potential to increase, or exacerbate, disparities between subgroups.
- Potential for mixed impact on disparities: Evidence or expert opinion suggests that these strategies can both increase and decrease disparities between subgroups.
- Inconclusive impact on disparities: There is not enough evidence to assess a strategy’s potential impact on disparities.
Each disparity rating includes a summary of the evidence supporting the rating and clarifies which subgroups and outcomes the rating applies to.
This revised disparity rating is in the Equity Analysis section of each strategy’s page and will be applied to all WWFH strategies by the end of 2023.