Evidence-Based Public Health; Ross C. Brownson, Elizabeth A. Baker, Terry L. Leet, and Kathleen N. Gillepsie. Oxford University Press, New York, 2003. ISBN: 0195143760. 256 pp. Price: $39.95.
“Evidence-based medicine” is a well-established movement focused on the accumulation of evidence from controlled trials. This is not to say that observational studies are not useful in medicine; to the contrary, they are preferred for studying the accuracy of a diagnostic test or for identifying risk factors of disease. However, when it comes to evaluating the efficacy of a therapy, there is no substitute for the randomized trial.1
Unfortunately, the level of evidence available in public health is not nearly so well developed. This is apparent in a new book, Evidence-Based Public Health, by Brownson and colleagues. The authors necessarily take a broad approach to “evidence.” They provide excellent discussions of how to access a range of data for decisions about public health programs, and how to implement and evaluate those programs through a range of study designs. Although randomized trials are mentioned as the design of “greatest suitability,” it is revealing that they are not discussed in detail. Only 3 pages are devoted to meta-analyses.
The fact of the matter is that randomized, controlled trials are seldom used to assess public health interventions. More commonly, public health programs are based on “good ideas.” For example, programs to reduce maternal mortality incorporate the training of traditional birth attendants and prenatal risk screening, even though evidence for their efficacy is limited.2
The occasional experimental studies that have been conducted in public health deserve comment. Such studies often use cluster or group randomization procedures, which are often more feasible in trials of public health interventions than individual randomization.3 It is not uncommon for these studies to conclude that good ideas do not necessarily work. Randomized trials of smoking prevention and cessation programs have confirmed the efficacy of individual behavioral counseling but show a disappointing lack of efficacy of community interventions.4,5 On a more positive note, the fact that such studies have been successfully conducted shows the potential for greater use of randomized, controlled trials in the evaluation of public health interventions.
It is reasonable to assume that higher-quality evidence will improve the practice of public health, just as it has the practice of medicine; but this, too, is a testable question. A recent randomized, controlled trial from Norway shows the difficulty in disseminating evidence-based practice among public health practitioners.6 One hundred and fifty public health physicians were randomly assigned either to an intervention group or a control group. The intervention included a workshop on evidence-based public health, a newsletter, access to databases, and an electronic discussion list. The control group received only a letter informing them that they had access to these sources of information. The intervention failed to change public health physicians’ behavior as measured by their use of evidence from the literature. This study suggests that even when evidence-based data for improving public health are at hand, we will need strong behavioral interventions to extend these benefits.
In short, public health lags far behind medicine in implementing the randomized trial. This gap is apparent in the book by Brownson and colleagues, which deals with the wide range of evidence, most of it observational, on which public health decision-makers must rely. Good books such as Evidence-Based Public Health help make the best of the data at hand, but they also show us (if only by implication) where the gaps lie. We should not overlook opportunities for imaginative trials in public health.
1.Sackett D, Rosenberg W, Muir Gray J, et al. Evidence based medicine: what it is and what it isn’t. BMJ
2.Miller S, Sloan N, Winikoff B, et al. Where is the ’E’ in MCH? The need for an evidence-based approach in safe motherhood. J Midwifery Womens Health
3.Ukoumunne OC, Gulliford M, Chinn S, et al. Evaluation of health interventions at area and organization level. BMJ
4.Lancaster T, Stead LF. Individual behavioural counseling for smoking cessation. Cochrane Database Syst Rev
5.Secker-Walker RH, Gnich W, Platt S, et al. Community interventions for reducing smoking among adults. Cochrane Database Syst Rev
6.Forsterlund L, Bradley P, Forsen L, et al. Randomised controlled trial of a theoretically grounded tailored intervention to diffuse evidence-based public health practice. BMC Central 2003;3:2. Available at: http://www.biomedcentral.com/1472-6920/3/2
. Accessed April 22, 2003.