Background: How physicians communicate the risks and benefits of medical care may influence patients' choices. Ways to communicate the benefits of risk-reducing drug therapies include the number 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 describe 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 hypothetical drug therapy to reduce the risk for heart attacks (1754 respondents) or hip fractures (1000 respondents). The data sources for both scenarios were clinical trials. Respondents were randomly assigned to a scenario with 1 of 3 outcomes after 5 years of treatment. 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 presented 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 postponements. This result suggests that the description of the anticipated outcome may influence the patient's willingness to accept a recommended intervention.