Zikmund-Fisher BJ (VA Ann Arbor Healthcare System)
Roberts TR (University of Michigan)
Fagerlin A (VA Ann Arbor Healthcare System)
Derry HA (University of Michigan)
Ubel PA (VA Ann Arbor Healthcare System)
When describing side effects, we often use side-by-side presentations of total risk (e.g. 10% get headaches with placebo, 14% with Medication X). This approach, however, forces people to do mental arithmetic to tell how much risk the medication causes (here, a 4% increase). Furthermore, people may confuse the additional risk (4%) with the total risk (14%) and inaccurately perceive excess risk. We tested whether presenting the risk difference explicitly (by describing the "additional" number of women experiencing side effects) would improve comprehension in both graphical and textual risk communications.
We recruited women from a demographically balanced panel to participate in an online survey experiment about tamoxifen side effects. Participants saw information describing how the risk of four types of side effects would increase with tamoxifen and were randomly assigned to view either a side-by-side display of total risk or a sequential presentation of the additional risk, in one of two formats (numerical text or pictograph). Since there is no single "correct" level of worry about a risk, to test the quality of our presentations, we also tested whether additional risk presentations would prevent other manipulations (e.g., risks "out of 1000" vs. "out of 100") from biasing perceptions. We compared women's ratings of subjective worry about each side effect (if they took tamoxifen) using bivariate t-tests and ANOVAs.
1789 women completed the online survey. For all side effects, worry ratings were significantly higher for total risk presentations than for those that highlighted additional risk (all p's < 0.001). This effect was significantly larger with textual descriptions than with pictographs in 3 out of 4 cases. Furthermore, while modifying the risk denominator or the presentation order changed reactions to total risk presentations, reactions to additional risk presentations remained constant.
Focusing on additional risk lowers worry about side effect risk by highlighting the fact that most risk existed at baseline. Further, these risk descriptions were resistant to two known cognitive biases: order and denominator effects.
Presenting side effect risk in a pictograph format, with additional risk specifically highlighted, may improve patient comprehension, facilitating communications and treatment decision making.