BACKGROUND: Personalized medicine may increase the amount of probabilistic information patients encounter. Little guidance exists about communicating risk for multiple diseases simultaneously or about communicating how changes in risk factors affect risk (hereafter risk reduction). PURPOSE: To determine how to communicate personalized risk and risk reduction information for up to 5 diseases associated with insufficient physical activity in a way laypeople can understand and that increases intentions. METHODS: We recruited 500 participants with <150 min weekly of physical activity from community settings. Participants completed risk assessments for diabetes, heart disease, stroke, colon cancer, and breast cancer (women only) on a smartphone. Then, they were randomly assigned to view personalized risk and risk reduction information organized as a bulleted list, a simplified table, or a specialized vertical bar graph (risk ladder). Last, they completed a questionnaire assessing outcomes. Personalized risk and risk reduction information was presented as categories (e.g., very low). Our analytic sample (N = 372) included 41.3% individuals from underrepresented racial/ethnic backgrounds, 15.9% with vocational-technical training or less, 84.7% women, 43.8% aged 50 to 64 y, and 71.8% who were overweight/obese. RESULTS: Analyses of covariance with post hoc comparisons showed that the risk ladder elicited higher gist comprehension than the bulleted list (P = 0.01). There were no significant main effects on verbatim comprehension or physical activity intentions and no moderation by sex, race/ethnicity, education, numeracy, or graph literacy (P > 0.05). Sequential mediation analyses revealed a small beneficial indirect effect of risk ladder versus list on intentions through gist comprehension and then through perceived risk (bIndirectEffect = 0.02, 95% confidence interval: 0.00, 0.04). CONCLUSION: Risk ladders can communicate the gist meaning of multiple pieces of risk information to individuals from many sociodemographic backgrounds and with varying levels of facility with numbers and graphs.

OBJECTIVES: (1) Test whether a mental imagery-based self-regulation intervention increases physical activity behaviour over 90 days; (2) Examine cognitive and affective precursors of change in physical activity behaviour. DESIGN: A randomized control trial with participants (N = 500) randomized to one of six intervention conditions in a 3 (risk communication format: bulleted list, table, risk ladder) x 2 (mental imagery behaviour: physical activity, active control [sleep hygiene]) factorial design. METHODS: After receiving personalized risk estimates via a website on a smartphone, participants listened to an audiorecording that guided them through a mental imagery activity related to improving physical activity (intervention group) or sleep hygiene behaviour (active control). Participants received text message reminders to complete the imagery for 3 weeks post-intervention, 4 weekly text surveys to assess behaviour and its cognitive and affective precursors, and a mailed survey 90 days post-baseline. RESULTS: Physical activity increased over 90 days by 19.5 more minutes per week (95%CI: 2.0, 37.1) in the physical activity than the active control condition. This effect was driven by participants in the risk ladder condition, who exercised 54.8 more minutes (95%CI 15.6, 94.0) in the physical activity condition than participants in the active control sleep hygiene group. Goal planning positively predicted physical activity behaviour (b = 12.2 minutes per week, p = 0.002), but self-efficacy, image clarity, and affective attitudes towards behaviours did not (p > 0.05). CONCLUSIONS: Mental imagery-based self-regulation interventions can increase physical activity behaviour, particularly when supported by personalized disease risk information presented in an easy-to-understand format.