Importance: Mobile applications on smartphones can communicate a large amount of personalized, real-time health information, including advice on skin cancer prevention, but their effectiveness may be affected by whether recipients can be convinced to use them.
Objective: To evaluate a smartphone mobile application (Solar Cell) delivering real-time advice about sun protection for a second time in a randomized clinical trial.
Design, setting, and participants: A previous trial conducted in 2012 used a randomized pretest-posttest design. For the present trial, we collected data from a volunteer sample of 202 adults 18 years or older who owned a smartphone. Participants were recruited nationwide through online promotions. Screening procedures and a 3-week run-in period were added to increase the use of the mobile application. We conducted follow-ups at 3 and 8 weeks after randomization to examine the immediate and the longer-term effects of the intervention.
Interventions: Use of the mobile application. The application gave feedback on sun protection (ie, sun-safety practices and the risk for sunburn) and alerted users to apply or to reapply sunscreen and to get out of the sun. The application also displayed the hourly UV Index and vitamin D production based on the forecast UV Index, time, and location.
Main outcomes and measures: Percentage of days with the use of sun protection, time spent outdoors in the midday sun (days and hours), and the number of sunburns in the last 3 months.
Results: Participants in the intervention group used wide-brimmed hats more at 7 weeks than control participants (23.8% vs 17.4%; F = 4.07; P = .045). Women who used the mobile application reported using all sun protection combined more than men (46.4% vs 43.3%; F = 1.49; P = .04), whereas men and older individuals reported less use of sunscreen (32.7% vs 35.5%; F = 5.36; P = .02) and hats (15.6% vs 17.9%; F = 4.72; P = .03).
Conclusions and relevance: The mobile application initially appeared to confer weak improvement of sun protection. Use of the mobile application was greater than in a previous trial and was associated with greater sun protection, especially among women. Strategies to increase the use of the mobile application are needed if the application is to be deployed effectively to the general adult population.