Research Underway to Evaluate Health Impact Assessment Process

Effort seeks to understand how HIAs affect factors that influence health

Research Underway to Evaluate Health Impact Assessment Process

Factors such as housing, transportation, and education can all affect people’s health, but decision-makers in these and similar sectors might not know about or act on these connections. A tool known as a health impact assessment (HIA) can help identify the potential health effects of a proposed policy, project, plan, or program, in part, by bringing a wider range of stakeholders into the process. Those doing HIA work—and those who fund it—want to understand the effect the process has on the social, economic, and environmental factors that shape health, what are known as the social determinants of health.  

The Health Impact Project, a collaboration of the Robert Wood Johnson Foundation and The Pew Charitable Trusts, promotes the use of HIAs as a decision-making tool for policymakers. In 2016, the project contracted with Harder+Company, a California-based research firm, to get a better sense of the effectiveness of these assessments. Harder’s work started with a look at previous evaluations of the factors associated with successful HIAs, including analysis of the challenges, limitations, and lasting effects of recommendations that were implemented. A second phase now in progress will provide an in-depth look at the impact of a broader array of HIAs on health.

In the initial phase, the study team identified key mechanisms—such as community engagement and use of health and demographic data in decisions—through which HIAs can lead to changes in the determinants of health in a community. Researchers also examined the impact the assessments have had on opportunities for individuals to be healthy—what is known in the field as health equity. Among the critical HIA outcomes they observed were increased trust between community members and decision-makers, protections from environmental risks with a focus on more vulnerable populations such as low-income families, and certainty that the needs of underserved communities were considered in infrastructure design and planning.

Harder conducted a literature review and reached out to 388 HIA practitioners pulled from the project’s HIA database for an online survey to collect information on the effect of each HIA and the current state of the field. The survey garnered nearly 150 responses, representing 126 unique HIAs. Researchers conducted in-depth interviews with 46 people who played key roles in 27 assessments about decisions in the built environment sector—the physical places where people live and work, including housing, physical activity infrastructure, transportation, and other components.

The interviews provided insights into the HIA process, outcomes, and expectations about the potential influence on determinants of health and health equity. Harder found that some of the key aspects of HIAs, such as engaging community members, using health data, and focusing on under-resourced populations, tend to affect three interrelated health determinants: community-government relationships, environmental risks, and the availability of resources that promote better health, such as sidewalks and bike lanes. The Health Impact Project will release a brief later this year with detailed findings.

This preliminary study wrapped up in 2017, and researchers now plan to measure how changes in determinants of health and health equity are influenced by HIAs and to identify ways to strengthen the HIA practice.

The Harder team will examine the following questions:

  • Are HIAs associated with changes in physical, social, and economic determinants of health such as housing quality and affordability of or access to healthy foods?
  • Are HIAs associated with changes in determinants of health equity, defined as the systems and structures that drive disparities across populations?
  • What mechanisms or circumstances can strengthen the association between HIAs and determinants of health and health equity? 

To augment the study, Harder is looking for additional, ongoing HIAs, especially those not captured in the project’s database. To participate or learn more, contact

Stacey Millett is a director and Abigail Baum and Arielle McInnis-Simoncelli are senior associates with the Health Impact Project.