4.3: What Does “Evidence-Based Practice” Mean?

Evidence-based public health relies on epidemiological data and research. In this chapter and the next we will look into understanding some aspects of epidemiology and how it relates to public health.

Evidence-based practice means “systematically finding, appraising, and using evidence as the basis for decision-making” (Seabert et al., 2022 p.115). This means that before we create programs or propose policies, we should gather as much evidence on the problem and potential solutions as possible, assess the applicability of available evidence to the current problem, and then use this knowledge to help guide decisions on whether or how to move forward. There may have been programs or policies similar to our ideas that have already been tried in the target population or other communities. What if there is evidence that this particular solution doesn’t work well? We certainly wouldn’t want to propose a program or policy that had already been proven to be ineffective. Or perhaps there is evidence that certain implementation methods were more effective than others. We would want to use that insight to make our interventions or policies more likely to work.

Two types of evidence can be used in this process: objective and subjective.

Objective evidence comes in the form of scientific studies and data collection. Typically, objective evidence includes things that can be measured or observed and is often expressed in numbers or percentages.

Subjective evidence may be in the form of expert advice or personal experiences and observations from community stakeholders. Subjective evidence includes personal accounts, individual experiences and stories - this type of evidence is often based on the perceptions of the person observing something or being interviewed.

In practice, objective evidence is often valued more highly than subjective evidence, in large part because well-done research uses several methods to reduce bias and misinterpretation. Objective data also tends to be more reliable than individual experiences or opinions. For example, a community member might perceive that homelessness is not a problem for their city because they used to see many tents and makeshift shelters on sidewalks in their neighborhood, and recently the sidewalks have been clear. But the objective data may show a more complex picture: perhaps the individuals who had been living in those makeshift shelters had been forced to relocate but were still unhoused.

Important to consider:

1. Care should also be taken in interpreting research and applying objective evidence to different situations. Just because a particular program worked for one community doesn’t mean it will work in another. Subjective evidence from stakeholders in the community or professional experience from public health workers should still be valued. For example, a community health worker may know from their work that many of the unhoused are not living on the street - they are living in their cars or “couch-surfing”, and therefore, they might not be aware of or have access to social services. Scientific studies may leave out certain populations, or we may not yet have scientific research available for a specific health problem. Therefore, it’s important to consider all sources of evidence when using an evidence-based approach to public health.

2. As we try to solve health problems with evidence-based practice, we must also consider the time it may take to establish evidence through research and the risks involved with waiting for an abundance of evidence to be established before we take action. Certainly, our understanding of the determinants of health is far better now than it was in the last century. Advances in technology and research methods continue to elucidate the drivers of health outcomes. As Sir Austin Bradford Hill (one of the researchers who first established the link between cigarette smoking and lung cancer) stated:

All scientific work is incomplete - whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time. (Hill, 1965, p. 300)

Pivotal research like the British Doctors Study conducted by Hill and Doll provided the foundation for the surgeon general’s warning about cigarette smoking causing lung disease. Since then, decades of research have supported this causal relationship and have been the practical basis for cigarette advertising bans, lawsuits against tobacco companies, warning labels on cigarettes, smoke-free policies in public spaces, and public health campaigns to reduce smoking. While efforts to reduce smoking have been successful over the decades, newer, similar threats have emerged in the form of e-cigarettes and nicotine vape products. While smoking rates have declined from 20% of adults in 2005 to 11% in 2021 (Centers for Disease Control, 2024), e-cigarette sales have skyrocketed - increasing by over 58% between 2020 and 2024 (Centers for Disease Control, 2024).

Figure \(\PageIndex{1}\): Domains that influence evidence-based decision making. Jacobs et al (2012).

Reference

Centers for Disease Control (2024). Current cigarette smoking among adults in the United States. Smoking and tobacco use. https://www.cdc.gov/tobacco/php/data...king/index.htm

Centers for Disease Control. (2024). About E-cigarettes (vapes). Smoking and tobacco use. https://www.cdc.gov/tobacco/e-cigarettes/about.html

Hill, A. B. (1965). The environment and disease: association or causation? Proceedings of the Royal Society of Medicine, 58(5), 295-300. https://doi.org/10.1177/003591576505800503

Jacobs, J. A., Jones, E. Gabella, B.A., Spring, B, Brownson, C. (2012). Tools for implementing an evidence-based approach in public health practice. Preventing Chronic Disease; 9:110324. DOI: http://dx.doi.org/10.5888/pcd9.110324.

Seabert, D., McKenzie, J., & Pinger, R. (2022). An introduction to community & public health (10th ed.). Jones & Bartlett Learning.