The framing effect of relative and absolute risk

To test whether a patient's perception of benefit is influenced by whether the benefit is presented in relative or absolute terms.

Questionnaire-based study.

A general medicine outpatient clinic at a rural tertiary care center associated with a medical school.

470 of 511 consecutive patients who agreed to answer a questionnaire while waiting for their clinic visit. Mean age was 49.1 years, 62.1% were female, and 51.9% had at least one year of education beyond high school.

Patient response to the choice of two equally efficacious medications for the management of a hypothetical serious disease. The benefit of one medication was stated in relative terms, the other in absolute terms. Patients could choose either medication alone, indicate indifference to the choice of medication, or choose not to answer.

56.8% of the patients chose the medication whose benefit was in relative terms. 14.7% chose the medication whose benefit was in absolute terms. Only 15.5% were indifferent to the choice of medication. The patients preferred the medication whose benefit was in relative terms across a wide range of ages and educational levels. Further questioning suggested that the patients thought benefit was greater when expressed in relative terms because they ignored the underlying risk of disease and assumed it was one.

The "framing" of benefit (or risk) in relative versus absolute terms may have a major influence on patient preference.