Effectiveness of a Text Message Intervention Promoting Seat Belt Use Among Young Adults: A Randomized Clinical Trial

IMPORTANCE: Approximately 1 in 10 adults do not always wear a seat belt, with the lowest use rates reported among young adults. OBJECTIVE: To determine the efficacy of a 6-week automated behavioral text message program promoting seat belt use compared with an attention control. DESIGN, SETTING, AND PARTICIPANTS: This parallel, 2-group, single-blind, individually randomized clinical trial included a convenience sample of patients recruited from 4 emergency departments in 2 cities in Pennsylvania from December 2019 to September 2021, with follow-ups at 6 and 12 weeks after randomization. Patients in stable condition aged 18 to 25 years who, in standardized screening, reported driving or being a passenger in a car without always using a seat belt in the past 2 weeks were eligible for recruitment. Participants who completed a 2-week trial run-in phase were randomly assigned 1:1 to the intervention or the assessment control. Data were analyzed from October 2019 to January 2020. INTERVENTIONS: The intervention group received Safe Vehicle Engagement (SAVE), a 6-week automated interactive text message program, including weekly seat belt use queries with feedback and goal support to promote consistent use of a seat belt. The control group received identical weekly seat belt use queries but no additional feedback. MAIN OUTCOMES AND MEASURES: The primary outcome was the proportion of young adults reporting always wearing a seat belt over the past 2 weeks, collected at 6 weeks (after a 2-week run-in) via web-based self-assessments and analyzed under intent-to-treat models using multiple imputation procedures. Sensitivity analyses included complete-case analyses of ordered categorical outcomes by vehicle seat position. Secondary outcomes included seatbelt use at 12 weeks and select cognitive constructs related to seat belt use. RESULTS: A total of 218 participants (mean [SD] age, 21.5 [2.1] years; 139 [63.8%] women) were randomized, with 110 randomized to SAVE and 108 randomized to the control group. A total of 158 individuals (72.4%) were included in the 6-week follow-up. The rate of always using a seat belt over the past 2 weeks at the 6-week follow-up was 41.3% (95% CI, 30.6%-52.0%) among SAVE participants and 20.0% (95% CI, 10.6%-29.3%) among control participants (odds ratio [OR], 2.8; 95% CI, 1.4-5.8; P = .005). A total of 140 individuals (64.2%) participated in the 12-week follow-up. At 12 weeks, the rate of always using a seat belt over the past 2-weeks was 42.8% (95% CI, 31.2%-54.2%) among SAVE participants and 30.7% (95% CI, 19.6%-41.6%) among control participants (OR, 1.7; 95% CI, 0.9-3.4; P = .13). When examining ordered categories of seat belt use by seat position, there were significantly greater odds of wearing a seat belt at 6 and 12 weeks among SAVE participants vs control participants (eg, 6 weeks for driver: OR, 5.2; 95% CI, 2.6-10.5; 6 weeks for front passenger: OR, 4.3; 95% CI, 2.2-8.2; 6 weeks for back passenger: OR, 4.3; 95% CI, 2.2-8.2). CONCLUSIONS AND RELEVANCE: In this randomized clinical trial, an interactive text message intervention was more effective at promoting seat belt use among targeted young adults than an attention control at 6 weeks. There was no significant difference between groups in always wearing a seat belt at 12 weeks. These findings, if replicated in a larger sample, suggest a scalable approach to improve seat belt use. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03833713