Objective According to WHO, smoking is an important cause of death in many countries. To encourage smoking cessation, persuasive messages can be used to raise smokers' risk perception. This work discusses challenges and solutions in designing a study to evaluate the impact of two different communication strategies (“gains from quitting” vs “losses from continuing smoking”) in encouraging calls to a Quitline.

Methodology A pragmatic intervention study was conducted in two subway stations for 4 weeks. Large posters containing non-age specific images and texts, based on the theme “shortness of breath”, were displayed on central dividing columns on the boarding platforms. Call rates from the selected stations, and respective rate ratios, overall and per study week, were calculated.

Results Passengers who were smokers, exposed to the positive-content message, called on average 1.7 times more often than those exposed to the negative-content message (p=0.01). Moreover, call rate ratios did not decline over the 4 weeks of the study (multiplicative interaction p=0.40).

Conclusions The effectiveness findings suggest that anti-smoking campaigns could use positive-content messages in order to recruit a larger smoker population. The proposed methodology can also be used to evaluate effectiveness of messages for “capturing’ individuals with other health problems (eg, alcohol abuse), thereby increasing its potential impact.