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An Introduction to Evidence-Based Public Health

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1 An Introduction to Evidence-Based Public Health
Neal D. Kohatsu, MD, MPH Associate Professor Dept. of Epidemiology Evidence-Based Public Health (EBPH) is an approach to public health practice that has evolved, in part, from advances in the field of Evidence-Based Medicine. This lecture begins with a public health case presentation to set the stage. It then traces the development of EBPH and describes its application, in practice. The intent of this presentation is to present an initial overview of EBPH.

2 Case Presentation Let’s begin with the case presentation dealing with childhood obesity.

3 Case Presentation Assume that you are the health director of a local health department. A community in your jurisdiction is concerned with its high rate of childhood obesity and requests your help. How do you proceed? This presentation will provide you with one possible approach--using the methods of evidence-based public health.

4 Overview Rise of evidence-based medicine
Development of evidence-based PH Current perspective on PH New definition of EBPH Evaluating and improving EBPH Review of case presentation Summary These are the main topics to be covered.

5 Rise of Evidence-Based Medicine
We’ll begin with a discussion of Evidence-Based Medicine.

6 Rise of Evidence-Based Medicine
First described in 1992 A new approach to teaching medicine A “revolution” in medical practice Other “evidence-based” approaches: ethics, psychotherapy, occupational therapy, dentistry, nursing, and librarianship Evidence-Based Medicine (EBM) was first described in It was hailed as a new approach to teaching medicine and was once described in the New York Times as a “revolution” in medical practice. EBM has spawned a host of “evidence-based” approaches including: ethics, psychotherapy, occupational therapy, dentistry, nursing, and librarianship.

7 Factors Driving EBM Let’s examine some of the factors that have driven the development and use of EBM.

8 Factors Driving EBM Overwhelming size of the literature
Inadequacy of textbooks Difficulty synthesizing evidence and translating into practice Increased number of RCTs Available computerized databases Reproducible evidence strategies Clearly, one of the overriding factors has been the explosive growth of the medical literature. The development of the Internet continues to expand the quantity and availability of medical information. The problem has been how to quickly and efficiently obtain high-quality, information that is relevant to each patient or clinical encounter, in both inpatient and outpatient settings. Textbooks, while compiling a lot of information in one location, are frequently out-of-date in key areas by the time they are published. Because of the overwhelming volume of medical literature, it has been difficult to sort through and extract what is needed for one’s unique practice. Although randomized controlled trials (RCTs) are expensive and time-consuming to conduct, their numbers increase because they provide essential scientific information particularly regarding interventions which may carry significant risks. The development of an array of computerized databases and new evidence strategies has facilitated the growth of EBM.

9 Sackett DL et al; Churchill Livingstone, 2000
Definition of EBM “The integration of best research evidence with clinical expertise and patient values.” Sackett DL et al; Churchill Livingstone, 2000

10 Steps of EBM Convert the need for info. into an answerable question
Track down the best evidence Critically appraise that evidence Integrate the appraisal with one’s clinical expertise and the individual patient Evaluate The process of EBM has been described as a series of steps, as follows: Convert the need for info. about prevention, diagnosis, prognosis, therapy, and causation into an answerable question Track down the best evidence to answer that question Critically appraise that evidence for its validity (closeness to the truth), impact (size of effect), and applicability (usefulness in one’s clinical practice) Integrate the appraisal with one’s clinical expertise and with the patient’s unique biology, values, and circumstances Evaluate one’s effectiveness in executing the first four steps and seek ways of improving one’s EBM approach. Sackett DL. EBM: how to practice and teach EBM. Churchill Livingstone 2000

11 Critique of EBM De-emphasizes patient values
Doesn’t account for individual variation Devalues clinical judgment Leads to therapeutic nihilism There has been no shortage of published critiques of EBM. Some of the more common criticisms are listed here. The definition of EBM explicitly requires consideration of clinical experience and patient values, which argues against the first and third charges. One can argue, of course, whether or not EBM is actually practiced this way. Medicine and science are based upon observing patterns and probabilities. The fact that no vaccine has 100% effectiveness, due to individual variation, does NOT mean that one should fail to be aware of consensus guidelines regarding immunizations and ignore such guidelines in practice. Thus, the second critique can be subject to counterargument. The final criticism, that EBM can lead to “therapeutic nihilism” (doing nothing if there aren’t extensive randomized controlled trials justifying an intervention) has also been challenged in that EBM relies on the best available evidence not on an idealized standard.

12 Parachute use to prevent death and major trauma related to gravitational challenge; systematic review of randomised controlled trials. Smith GC, Pell JP. BMJ 327: ; 2003. This paper, published in the British Medical Journal, somewhat whimsically points out that EBM should not require the suspension of common sense and good judgment. The authors do make a serious point, however. The rationale outlined below for the need for RCTs to demonstrate the effectiveness of parachutes has been applied to many interventions in medicine. OBSERVATIONAL DATA ARE INFERIOR TO RCT DATA: Hormone replacement therapy (HRT) use appeared to lower coronary heart disease (CHD) risk in observational studies; The Women’s Health Initiative (an RCT) showed that HRT raises CHD (and many other) risks. NATURAL HISTORY OF GRAVITATIONAL CHALLENGE: If failure to use a parachute resulted in 100% mortality, that might be evidence of effectiveness. However, survival from falls of 33,000 feet have been documented. Furthermore, parachutes have been associated with morbidity and mortality. Therefore RCTs are needed to determine the balance of risks and benefits. OBSERVATIONAL STUDIES ARE SUBJECT TO SELECTION AND REPORTING BIAS: Those jumping from airplanes without parachutes are likely to have pre-existing psychiatric morbidity. Individuals who jump with parachutes may have less mental illness and differ in other characteristics such as socioeconomic status and cigarette smoking. Thus, there may be a healthy cohort effect, in play.

13 Development of EBPH Jenicek (1997) published a review discussing epidemiology, EBM, EBPH Epidemiology described as the foundation of both EBM and EBPH EBPH unique in using complex interventions with multiple community and societal issues Jenicek noted that epidemiology was the foundation for both Evidence-Based Medicine (EBM) and Evidence-Based Public Health (EBPH).

14 Jenicek M. J Epidemiol 1997;7:187-97
Definition of EBPH (1) “EBPH is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of communities and populations in the domain of health protection, disease prevention, health maintenance and improvement.” Jenicek (1997) Key terms in this definition of EBPH are… EXPLICIT: Use defined methods JUDICIOUS: Use judgment BEST EVIDENCE: Sort through the literature and identify what is useful Jenicek M. J Epidemiol 1997;7:187-97

15 Brownson RC. J Public Health Manag Pract 1999;5:86-97
Definition of EBPH (2) “EBPH is the development, implementation, and evaluation of effective programs and policies in public health through application of principles of scientific reasoning, including systematic uses of data and information systems and appropriate use of program planning models.” Brownson (1999) Brownson’s definition is somewhat similar to Jenicek. Critical terms include: EFFECTIVE: Implies that evidence determines what programs are effective SCIENTIFIC REASONING: Relates to thinking and judgment SYSTEMATIC and MODELS: Allude to the explicit use of defined methods Brownson developed a model of EBPH analogous to EBM (see next slide). Brownson RC. J Public Health Manag Pract 1999;5:86-97

16 Brownson RC. J Public Health Manag Pract 1999;5:86-87
Steps of EBPH Develop an initial statement of the issue Search the scientific literature and organize information Quantify the issue using sources of existing data Develop and prioritize program options; implement interventions Evaluate the program or policy These are the steps of Evidence-Based Public Health (EBPH) as described by Brownson et al. Brownson RC. J Public Health Manag Pract 1999;5:86-87

17 Steps of EBM Convert the need for info. into an answerable question
Track down the best evidence Critically appraise that evidence Integrate the appraisal with one’s clinical expertise and the individual patient Evaluate As presented previously, here are the steps of EBM, for comparison: Convert the need for info. about prevention, diagnosis, prognosis, therapy, and causation into an answerable question Track down the best evidence to answer that question Critically appraise that evidence for its validity (closeness to the truth), impact (size of effect), and applicability (usefulness in one’s clinical practice) Integrate the appraisal with one’s clinical expertise and with the patient’s unique biology, values, and circumstances Evaluate one’s effectiveness in executing the first four steps and seek ways of improving one’s EBM approach. Sackett 2000

18 Kohatsu et al. Am J Prev Med 2004;27:417-21
EBM and EBPH Parallels State the scientific question of interest Identify the relevant evidence Determine what information is needed to answer the scientific question Determine the best course of action considering the patient or population Evaluate process and outcome The analogous steps of EBM and EBPH are highlighted, here. Kohatsu et al. Am J Prev Med 2004;27:417-21

19 Cochrane Collaboration
Mission: “…an international organisation that aims to help people make well-informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews of the effects of healthcare interventions.” One of the key resources that has enabled the development and practice of both EBM and EBPH is the Cochrane Collaboration. Its mission is stated in this slide.

20 Structure of the Collaboration
Collaborative Review Groups Methods Groups Fields Consumer Network Centres The structure of the Collaboration consists of the following components: Collaborative Review Groups (CRGs)—Contain researchers healthcare professionals and consumers interested in particular health conditions or diseases. There are 50 CRGs. Methods Groups—Exist to improve the methodology of systematic reviews. Fields—Focus on dimensions of health care other than health problems such setting (e.g., primary care), defined population (e.g., older people), or intervention (e.g., vaccines). Consumer Network—Provides information and a forum for networking for consumers involved in the Collaboration. Centres—Supports the work of the above entities in 12 Centres around the world.

21 Guide to Community Preventive Services
Developed by the U.S. Task Force on Community Preventive Services Supported by the U.S. Centers for Disease Control and Prevention (CDC) Based on systematic reviews Recommendations based on strength of evidence Another important resource for EBPH is the Guide to Community Preventive Services (www.thecommunityguide.org). The Guide uses a defined, evidence-based approach to develop recommendations for addressing a number of important public health problems. Briss PA et al. AJPM 2000;18(1S):35-43.

22 Topic Areas Vaccine-preventable diseases Physical activity Oral health
Tobacco use prevention and control Reducing motor vehicle occupant injury Diabetes Physical activity Oral health Social Environment Prevention of injuries due to violence Cancer The Task Force has published over 100 findings across 9 topic areas. This list of topics brings up one of the weaknesses of EBM and EBPH: The evidence base for both is far more limited than the array of problems confronted in practice.

23 A Current Perspective on PH
Public health encompasses: “the efforts, science, art, and approaches used by all sectors of society to assure, maintain, protect, promote, and improve the health of the people.” If we are going to be able to discuss EBPH, we need to have an idea of what public health is. In 1988, a U.S. Institute of Medicine committee defined the key functions of public health as, ASSESSMENT, ASSURANCE, AND POLICY DEVELOPMENT. A more recent IOM panel defined the scope of public health as shown in this slide. The future of the public's health in the 21st century. IOM 2002.

24 Public Health Communities Healthcare system Employers & business Media
Academia Government Components of public health are indicated, here. Individuals and communities are no longer passive recipients of public health services. They are active participants in the public health system. IOM, 2002

25 Kohatsu, Robinson, Torner. AJPM 2004;27:417-21.
Definition of EBPH (3) “The process of integrating science-based interventions with community preferences to improve the health of populations.” Kohatsu et al. recently published a definition of EBPH emphasizing three concepts (underlined). Kohatsu, Robinson, Torner. AJPM 2004;27:

26 The Future of Evidence-Based Public Health
How can we evaluate and improve EBPH in practice?

27 Improving EBPH in Practice
Quality of the Science Base Community Involvement Effect on Public Health Outcomes These are the core areas in which EBPH advances should be aimed.

28 Improving the Quality of the Science Base
Moving beyond RCTs Transparent Reporting of Evaluations with Non-randomized Designs (TREND) Grading of Recommendations Assessment, Development and Evaluation (GRADE) Improving the quality of the science base supporting EBPH can be addressed in many ways, including the following: RCTs are well suited for demonstrating efficacy of a clinical intervention. They are less suitable for many public health interventions which have complex causal chains and which may be tested in communities that are quite variable. May have to standardize the intervention by function (diabetes education tailored to culture, education, etc.) rather than content. The TREND statement (Des Jarlais et al. Improving the reporting quality of nonrandomized evaluations of behavioral and public health interventions: the TREND statement. Am J Public Health 2004;94: ) provides a checklist and description of elements that should be present in papers reporting results from nonrandomized studies. It was developed along the lines of the Consolidated Standards of Reporting Trials (CONSORT) guidelines which were developed to improve the quality of RCTs. The GRADE system (GRADE Working Group. Grading quality of evidence and strength of recommendations. BMJ 2004;328: ) was developed in response to the variability in ranking systems used by various health-related organizations to assess the quality of evidence and the strength of recommendations.

29 Improving Community Involvement
Ideally, an entire community participates in determining and addressing its public health needs. Here, staff of the Nepal Water Project (a non-governmental organization dedicated to improving access to high-quality water supplies for communities in Nepal) meet with community members.

30 Improving Community Involvement
“Public health institutions should provide communities with the information they have that is needed for decisions on policies or programs and should obtain the community’s consent for their implementation.” --Public Health Leadership Society Increasing community involvement in public health interventions--moving from passive to active involvement--is an ethical imperative. This slide highlights one of the 12 principles of the ethical practice of public health of the (U.S.-based) PHLS. These principles have been endorsed by the American Public Health Association, the Public Health Foundation, and the American College of Preventive Medicine, among other organizations. This concept of community consent for public health intervention is analogous to informed consent provided by a patient for a clinical intervention.

31 Informed Consent at the Community Level
Community-based participatory research Community advisory boards These are a couple of strategies to directly engage communities in the development and implementation of public health interventions that might be applied where they live. Community-based participatory research is an approach that involves community members in all aspects of a public health research project including: assessing needs, formulating questions, devising intervention strategies, evaluating outcomes, and implementing programs and policies. Community advisory boards have been proposed as a valuable means of obtaining community input on clinical trials, especially the informed consent process, to ensure that participants are fully aware of risks, benefits, and implications. The advisory board process could also be used to engage community members in other types of public health interventions.

32 Improving EBPH Outcomes
Difficult to assess Issues of sample size, contamination, blinding, long-term follow-up Ethical constraints of withholding evidence Patients do better in the “real world” when provided with evidence-based therapy It is important to improve our ability to know that an EBPH intervention achieved its desired outcome. However, formal evaluation of EBPH is difficult for the reasons listed in this slide. We do know, however, from outcomes research that patients do better in the “real world” when provided with evidence-based therapy (e.g., beta-blocker and aspirin after a heart attack; provision of recommended clinical preventive services). They also do worse when provided with therapy that lacks evidence (e.g., carotid endarterectomy patients not meeting EBM guidelines have a much higher risk of stroke and death).

33 Case Presentation Assume that you are the health director of a local health department. A community in your jurisdiction is concerned with its high rate of childhood obesity and requests your help. How do you proceed? Now let’s return to the case presentation introduced at the beginning of this lecture. In the following slides, we will address the issue using the steps of EBPH.

34 Develop an Initial Statement of the Issue
The prevalence of obesity among the 327 elementary school children in the community is 35%. With the support of parents, school staff, and community-based organizations, how can this obesity rate be reduced through lifestyle interventions? To accomplish this initial step, it is essential to engage the community. In your role as health director, you could support the development of a task force led by a community member. This slide shows the statement of the issue such a task force developed.

35 Quantify the Issue The prevalence of obesity was determined by a special survey. The rate of obesity was found to increase by grade level. The rates were about equal in girls and boys. 100 minutes/wk provided at school for physical activity, but only 40 minutes is guided by a teacher. Here are key pieces of information gathered as part of quantifying the issue.

36 Search the Scientific Literature and Organize Information
Medline search Cochrane Collaboration Task Force on Community Preventive Services Search the literature using some of the resources previously described and organize the information.

37 Task Force on Community Preventive Services
Insufficient evidence to recommend classroom-based health education to provide information on managing health risks. Strongly recommended curricula and policies to increase the amount of moderate or vigorous activity, increase the amount of time in PE class, or the amount of time being active in PE. As part of your research, you find that the Task Force made the following assessments regarding physical activity interventions. MMWR 2001;50, No. RR-18

38 Develop and Prioritize Program Options
A community-based work group develops a number of options to increase physical activity in school. There are debates about losing time in the classroom and impact on test performance.

39 Develop an Action Plan The next step is to develop an action plan.

40 Develop an Action Plan Agreement is reached on a pilot project for the next school year involving reducing the lunch hour and increasing time in physical education with an emphasis on activities that get all children to be active. The program will be evaluated by all stakeholders (e.g., children will be surveyed)

41 Summary EBM has transformed medicine
EBM has fostered development of EBPH EBPH continues to evolve Increased community engagement EBM has transformed the practice of medicine by providing the techniques to access and improve the science base on which clinical decisions are made. The success of EBM has led to evidence-based approaches in a number of fields (e.g., ethics, psychotherapy, occupational therapy, dentistry, nursing, and librarianship), including public health. EBPH is relatively young in its development and continues to evolve. Increased community engagement is an important, and desirable, part of this evolution


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