Background: Primary care providers (PCPs) prescribe less often treatments for smoking cessation than for other major risk factors. We assessed the effect of training PCPs to offer smoking cessation treatments to current smokers as the default choice using an encounter decision aid (DA) on smoking cessation.

Methods: Pragmatic, cluster-randomized controlled trial with PCPs in private practice in Switzerland and France. The intervention was a half-day course teaching PCPs the default choice approach using a DA. Control PCPs received a 1-h refresher training on smoking cessation aids. PCPs recruited daily smokers seen for routine care. The primary outcome was self-reported, 7-day, point prevalence smoking abstinence at 6 months. Secondary outcomes were quit attempts and use of smoking cessation aids at 3 weeks, 3 months, and 6 months, and a patient-reported measure of shared decision-making (CollaboRATE scale 1-10, higher scores = more involvement).

Results: Forty-two PCPs completed the training (76% Swiss) and recruited 287 current smokers (105 intervention group, 182 control group), with 51% women, mean age 48 (SD, 2.6), 77% who smoked <20 cigarettes/day, and 221 who responded at 6 months follow-up (77%). The intervention did not affect self-reported smoking abstinence rate at 6 months (9.5% intervention and 10.4% control groups, respectively; OR 0.88 (95%CI 0.37-2.10). It did however increase the number of quit attempts at 3 weeks (OR 2.09, 95%CI 1.04-4.20) and the use of smoking cessation aids at the 3-week and 3-month follow-ups (OR 2.57, 95%CI 1.21-5.45 and OR 2.00, 95%CI 1.11-3.60, respectively). The mean CollaboRATE score was 8.05/10 in the intervention group and 7.28/10 in the control group (p=0.02), reflecting more patient involvement in decision-making.

Conclusion: Training PCPs to use a decision aid did not improve smoking abstinence rate, despite short-term increases in quit attempts and use of smoking cessation aids. It improved patient involvement in decision-making.

Trial registration: ClinicalTrials.gov identifier: NCT04868474.