Patient Characteristics Associated With Sensitivity to Message Framing: A Within‐Subject Comparison Study Using Data From the Illuminating Dialogues and Insights in Onychomycosis Management ( <scp>IDIOM</scp> ) Survey

Onychomycosis is a common fungal infection, yet the impact of gain- versus loss-framed messages on treatment intention has not been examined. This within-subject study evaluated whether age and sex modified sensitivity to message framing in onychomycosis. Among 300 treatment-experienced patients, we compared gain- and loss-framed messages under mild- and severe-risk scenarios and measured changes in treatment intention. Participants were classified into gain-dominant, loss-dominant, and neutral clusters based on response differences, and associations with age and sex were examined using multinomial logistic regression analysis. The neutral cluster accounted for the majority of patients, suggesting that the risk information itself may have been persuasive regardless of framing. However, effect modification was observed in the severe-risk scenario: women were more likely to be classified into the loss-dominant cluster, whereas older age was associated with the gain-dominant cluster. These findings highlight the importance of communicating the risks of untreated onychomycosis and suggest that patient characteristics may be associated with directional framing preferences, particularly under severe-risk messages. Given the hypothetical intention outcome and limited robustness in sensitivity analyses, clinical implications should therefore be interpreted cautiously. TRIAL REGISTRATION: UMIN Clinical Trials Registry registration number: UMIN000050195.