Tuesday, October 20, 2015: 1:45 PM
Grand Ballroom A (Hyatt Regency St. Louis at the Arch)

Erika A. Waters, PhD, MPH, Washington University School of Medicine, Saint Louis, MO, Thorsten Pachur, PhD, Max Planck Institute for Human Development, Berlin, Germany and Graham Colditz, MD, DrPH, Washington University in St. Louis, Saint Louis, MO
Purpose: An important principle of informed medical decision making is that patients weigh the benefits and risks of treatment options.  However, previous research has shown that side effects can prompt patients to forego otherwise-beneficial therapies.  The present study examines the underlying structure of side effect perceptions in an effort to identify which characteristics make side effects particularly aversive and how this aversion may affect medical decisions.

   Methods: Women (N=148) aged 40-74 years of age were recruited from a large participant registry to complete an online experiment. Participants rated 10 side effects--randomly selected from a pool of 20--on each of 15 characteristics (e.g., frightening, gross). In addition, for each side effect they read a hypothetical scenario in which an effective and necessary medical treatment conferred a 1 in 100 risk of experiencing a side effect (e.g., nausea). Aversiveness of each side effect was measured in four ways: participants indicated their willingness to take the medication (i.e., choice), willingness to pay to avoid the side effect (WTP), the amount of negative affect associated with the side effect, and they ranked the side effects in terms of their desirability. Each of the 20 side effects was rated by at least 45 participants.

   Results: A principle component analysis of the ratings of the side effects’ characteristics yielded a four-factor solution, which together accounted for 82% of the total variance: dread (27%), shame (24%), disabling (19%), and coping (12%).  Regression analyses further indicated that dread was the strongest predictor of each measure of aversiveness.  High dread was associated with statistically significantly (p<.05) lower choice (b=-.52) and desirability rankings (b=-.64), and higher WTP (b=.59) and negative affect (b=.73).  Side effects that were perceived as disabling were associated with significantly higher WTP (b=.47) and negative affect (b=.51), and lower desirability (b=-.61), but not choice (b=-.16).  Side effects perceived as shameful or associated with coping difficulties were not statistically significantly associated with any of the aversiveness measures (ps>.05).

   Conclusions: These findings reveal that affect is a key factor in patients’ perceptions of side effects and this aspect has a strong impact on their decisions regarding treatments that involve side effects.  Decision support tool developers should consider adding components to address the affective nature of medical decision making.