Smoking cessation smartphone application use over time: Do usage patterns predict 12-month cessation outcomes? (Preprint)

Little is known about how individuals engage over time with smartphone application interventions and whether this engagement predicts health outcomes.In the context of a randomized trial comparing two smartphone applications (apps) for smoking cessation, to determine: (1) distinct groups of smartphone app login trajectories over a 6-month period, (2) their association with smoking cessation outcomes at 12-months, and (3) baseline user characteristics that predict data-driven trajectory group membership.Functional clustering of 182 consecutive days of smoothed login data from both arms of a large (N = 2415) randomized trial of two smartphone apps for smoking cessation (iCanQuit and QuitGuide) was used to identify distinct trajectory groups. Logistic regression was used to determine the association of group membership with the primary outcome of 30-day point prevalence smoking abstinence at 12 months. Finally, baseline characteristics associated with group membership were examined using logistic and multinomial logistic regression. Analyses were conducted separately for each app.For iCanQuit, participants were clustered into three groups: "1-week users" (n=610, 57% of the sample), "4-week users" (n=303, 28%), and "26-week users" (n=156, 15%). For smoking cessation rates at the 12-month follow-up, compared to 1-week users, 4-week users had 50% higher odds of cessation (30% vs. 23%; OR = 1.50; 95% CI = 1.05, 2.14; p = .027) whereas 26-week users had 397% higher odds (56% vs. 23%; OR = 4.97; 95% CI = 3.31, 7.52; p < .001). For QuitGuide, participants were clustered into two groups: "1-week users" (n=695, 65% of the sample), and "3-week users" (n=369, 35%). The difference in the odds of being abstinent at 12-months for 3-week users vs. 1-week users was minimal (23% vs. 21%; OR = 1.16; 95% CI = 0.84, 1.62; p = .370). Different baseline characteristics predicted trajectory group membership for each app.Patterns of 1-, 3-, and 4-week usage of smartphone apps for smoking cessation may be common for how people engage in digital health interventions. There were significant higher odds of quitting smoking among 4-week users, and especially among 26-week users of the iCanQuit application. To improve study outcomes, strategies for detecting users who disengage early from these interventions (1-week users) and proactively offering them a more intensive intervention could be fruitful.Clinical Trials.gov Registration Number: NCT02724462.