Design and Evaluation of a Mobile-phone Based Intervention to Support Smoking Cessation Among Chilean Women Aged 18 to 44 Years in the Metropolitan Region

This protocol corresponds to a single-blind, two-arm, randomized clinical trial of a smoking cessation intervention based on a mobile-phone app. Eligible participants are Chilean women from the Metropolitan Region, who smoke daily (at least one cigarette per day) or weekly (at least 7 cigarettes per week), and who are willing to make a quit attempt within one month of enrollment. Study will be advertised on the local radio, primary care centers, smoking cessation services and through social media campaigns. Study information will be available online. Potential participants will be asked to register their interest by sending an email to the study. Research assistants then will contact respondents by phone in order to complete a baseline questionnaire about sociodemographic variables, characteristics of tobacco consumption, and to assess eligibility for the study. Eligible participants will be then randomized to the intervention group or control group using a computerized and automated process, in blocks of 6. A minimization algorithm balancing for Fagerstrom score for nicotine addiction (≤5, >5) will be used. Researchers who will gather data and those who will measure carbon monoxide in exhaled air will be masked to treatment allocation.

Each participant will be emailed the link with either the intervention or the control version of the mobile-phone app. Once participants download the app, they will be asked to provide informed consent by clicking the "accept" or "reject" button in the app.

Participants randomized to the intervention app will be sent motivational and preparatory content for the first two weeks, and they will be asked to set a quit date within 4 weeks from enrollment. The mobile app will send an average of 4 messages per day during the first month after quit date, followed by three messages per week up to the end of the study at month 6.

The intervention program was designed based on current best evidence on strategies to support smoking cessation, and included work of Chilean experts in smoking cessation. The design of the intervention app also included the opinion and preferences of potential participants who participated in focus groups during intervention design. The intervention app includes motivational messages, tips on stress management, on how to ask support from friends and family, how to use distraction techniques and how to deal with cravings, lapses and early relapse.

The intervention app also includes a "help button" which provides extra messages in case of cravings and a "lapse/relapse button", which provides advice about what to do if the participant returned to smoke. The control group will receive a control app which will send 1 message every two weeks thanking participants for taking part in the study, and encouraging them to stay in the study for the 6 month follow-up period. After completing the 6-month follow-up evaluation, the control group will be offered access to the intervention app.