Different Ways to Describe the Benefits of Risk-Reducing Treatments A Randomized Trial Peder A. Halvorsen, MD; Randi Selmer, PhD; and Ivar Sønbø Kristiansen, MD, PhD, MPH Background: How physicians communicate the risks and benefits of medical care may influence patients’ choices. Ways to commu- nicate the benefits of risk-reducing drug therapies include the num- ber needed to treat (NNT) to prevent adverse events, such as heart attacks or hip fractures, and gains in disease-free life expectancy or postponement of adverse events. Previous studies suggest that the magnitude of the NNT does not affect a layperson’s decision about risk-reducing interventions, but postponement of an adverse event does affect such decisions. Objective: To examine laypersons’ responses to scenarios that de- scribe benefits as postponing an adverse event or the equivalent NNT. Design: Cross-sectional survey with random allocation to different scenarios. Setting: General community. Participants: Respondents to a population-based health study. Intervention: The survey presented scenarios regarding a hypothet- ical drug therapy to reduce the risk for heart attacks (1754 respon- dents) or hip fractures (1000 respondents). The data sources for both scenarios were clinical trials. Respondents were randomly as- signed to a scenario with 1 of 3 outcomes after 5 years of treat- ment. For the drug to prevent heart attacks, the outcomes were postponement by 2 months for all patients, postponement by 8 months for 1 of 4 patients, or an NNT of 13 patients to prevent 1 heart attack. For the drug to prevent hip fractures, the outcomes were postponement by 16 days for all patients, postponement by 16 months for 3 of 100 patients, or an NNT of 57 patients to prevent 1 fracture. Measurements: Consent to receive the intervention and perceived ease of understanding the treatment effect. Results: The overall rate of response to the survey was 81%. In the heart attack scenarios, 93% of respondents who were pre- sented with the NNT outcome consented to drug therapy, 82% who were presented with the outcome of large postponement for some patients consented to therapy, and 69% who were presented with the outcome of short postponement for all patients consented to therapy (chi-square, 89.6; P  0.001). Corresponding consent rates for the hip fracture scenarios were 74%, 56%, and 34%, respectively (chi-square, 91.5, P  0.001). Respondents who said that they understood the treatment effect were more likely to consent to therapy. Limitation: Decisions were based on hypothetical scenarios, not real clinical encounters. Conclusions: Treatment effects expressed in terms of NNT yielded higher consent rates than did those expressed as equivalent post- ponements. This result suggests that the description of the antici- pated outcome may influence the patient’s willingness to accept a recommended intervention. Ann Intern Med. 2007;146:848-856. www.annals.org For author affiliations, see end of text. C onsiderable resources are devoted to drug therapies that are aimed at modifying risk factors, such as hy- pertension, elevated cholesterol levels (1), and osteoporosis. For individual patients, the choice to begin preventive drug therapy should be consistent with their values and prefer- ences. Thus, to engage meaningfully in shared decision making and to provide truly informed consent, patients need to have a clear understanding of the benefits and harms of a treatment. Strong and consistent evidence shows that stated preferences for medical interventions may depend on how the treatment effects are described. For example, the likelihood of choosing a therapy may depend on whether its benefits are presented as absolute risk reduc- tions or relative risk reductions (2) or as losses versus gains (3–5). These effects suggest the potential for influencing the patient’s response by describing treatment effects in a certain way. We explore laypersons’ responses to different ways of explaining possible outcomes of an intervention. When informing decision makers about the benefit of risk-reducing drug therapies, several authors have advo- cated using the number needed to treat (NNT) to avoid 1 outcome (6 –10), which is defined as the reciprocal of the absolute risk reduction. The NNT is the average number of patients in an intervention group who must be treated for a specific period to observe 1 fewer adverse outcome by the end of this period compared with those in a control group. Several authors believe that NNT provides an easily understood way to describe the effort needed to prevent adverse outcomes (9 –11). However, for drug therapies aimed at disease processes that develop slowly, such as ath- erosclerosis and osteoporosis, the term prevention may be misleading. Rather than completely preventing adverse outcomes in a small fraction of patients, an intervention See also: Print Editors’ Notes ............................. 849 Glossary ................................. 855 Editorial comment.......................... 891 Summary for Patients ....................... I-50 Web-Only Appendix Tables Conversion of figures and tables into slides Annals of Internal Medicine Article 848 © 2007 American College of Physicians