Do risk visualizations improve the understanding of numerical risks? A randomized, investigator-blinded general population survey

BACKGROUND: Risk visualizations are often employed to support risk communication. However, their effectiveness in communication of single absolute risks remains unclear. We investigated the effectiveness of risk visualizations in conveying verbatim knowledge of single absolute risks among the general population. METHODS: Randomly sampled members of the general Dutch population completed four basic risk conversions from percentages to natural frequencies and vice versa. By random investigator-blinded allocation, these conversions were supported by either icon arrays, pie charts, bar graphs or no visualization. Verbatim risk knowledge was scored as the number of conversions completed correctly. RESULTS: 393 subjects were included. Overall, 60% of respondents answered all four questions correctly. Risk format (percentages vs. natural frequencies, p = 0.677) and risk magnitude (p = 0.532) were not associated with verbatim risk knowledge score. Younger age (p = 0.001) and higher education level (p < 0.001) were independently associated with higher scores. The use of risk visualizations was not associated with higher scores (OR = 1.08; 95% confidence interval: 0.69-1.69; p = 0.745). All three forms of risk visualization were equally ineffective. These findings held when stratifying by risk format, risk magnitude and user preference for a certain form of risk visualization. There were no significant interactions with age or education level. CONCLUSION: Risk visualizations did not improve conveyance of verbatim knowledge of single absolute risks, irrespective of age, education level, risk magnitude, risk format and form of risk visualization. Risk visualizations may therefore be less suitable for settings in which detailed conveyance of single absolute risks is the main objective, although their effect on user experience and perception of risk communication and subsequent patient activation and participation remains to be elucidated.

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