Applying Human-Centered Design to Develop Smartphone-Based Intervention Messages to Help Young Adults Quit Using E-Cigarettes and Cigarettes: A Remote User Testing Study.

Background: Despite the popularity of concurrent use of electronic cigarettes (e-cigarettes) and cigarettes (dual tobacco use) among young adults, few interventions address the cessation of both tobacco products. The application of a human-centered design (HCD) approach in the development of such interventions remains limited. Objective: This study used an HCD approach to develop smartphone-based intervention messages for dual tobacco cessation for young adults. Methods: Intervention messages were developed based on theories, cessation guidelines, existing messages, and our previous formative study. Three rounds of message testing were conducted asynchronously via an online platform with 35 young adults (18-29 years old) who currently used both e-cigarettes and cigarettes and were motivated to quit either smoking or vaping in the next 6 months. In each round, a new sample of 10-12 participants evaluated the messages individually. For the quantitative assessment, participants viewed and rated each message on a scale from 1 ("very low degree") to 5 ("very high degree") across 4 components: Comprehension ("This message is easy to understand"), Usefulness ("This message is useful for encouraging tobacco cessation"), Tone ("The language is clear and non-judgmental"), and Design ("The design is appealing"). For the qualitative assessment, participants used a platform-enabled feature to place markers on specific parts of messages they liked, disliked, or found confusing and then provided brief explanations for their feedback. Initial messages were assessed during the first 2 rounds of testing, and those with low mean scores were revised based on participants' feedback and retested in the third round. Results: We found significant improvements in message ratings after refinement. The overall mean score increased from 3.6 (SD 0.4) to 4.6 (SD 0.2) (P<.001), using paired t tests. Specifically, the mean score of "Comprehension" improved from 4.0 (SD 0.5) to 4.9 (SD 0.2) (P<.001), the mean score of "Usefulness" increased from 3.0 (SD 0.6) to 4.4 (SD 0.4) (P<.001), the mean score of "Tone" increased from 3.8 (SD 0.6) to 4.8 (SD 0.2) (P<.001), and the mean score of "Design" increased from 3.4 (SD 0.48) to 4.4 (SD 0.3) (P<.001). The qualitative assessments highlighted design elements related to message liking, such as clear layout, minimalistic imagery, italicized quotes, and highlighted keywords. Conversely, design features related to message dislike included color shades, lengthy text, and confusing wording. Conclusions: This study demonstrated the use of HCD in developing smartphone-based intervention messages to support dual tobacco cessation among young adults. Integrating remote message testing improved the feasibility of rapid prototyping while enhancing the relevance and appeal of message content and design. Future interventions targeting emerging health behaviors among young adults may benefit from incorporating a remote testing method to efficiently gather user feedback and refine intervention messages in a timely manner.