Supplementary Material for: How a five-day stay in the tobacco-free environment of the Stoptober House supports individuals to quit smoking: a mixed methods pilot study

Introduction
The Stoptober House is part of the annual national Stoptober smoking cessation campaign in the Netherlands. During the first week of October, 48 volunteers resided in the tobacco-free Stoptober House for five days and received smoking cessation counselling. This pilot study explored how the Stoptober House may have facilitated smoking cessation among participants.
Methods
We included 48 individuals who were selected for the Stoptober House (intervention group) and 67 individuals who were not selected (control group). Surveys were conducted at baseline, immediately after, two and eight weeks post-intervention. We compared self-reported abstinence, psychosocial mediators related to smoking cessation, and perceived active elements of the Stoptober House between the intervention and control groups using t-/chi-square tests and linear mixed model (LMM) analysis. 16 semi-structured qualitative interviews were conducted to explore participants' perspectives on the elements contributing to their success in quitting smoking.
Results
At 8 weeks follow-up, a higher proportion of participants in the intervention group (24/48 (50%)) reported being abstinent compared to the control group (5/67 (7%); p<0.001). Among participants who reported making a quit attempt, 22/38 (57.9%) in the intervention group remained abstinent compared to 4/17 (23.5%) in the control group (p=0.022).
The intervention group also exhibited higher self-efficacy to quit smoking throughout the follow-up period and higher social support immediately after the Stoptober House. No significant differences were observed in other psychosocial factors. The interviews highlighted several perceived elements of the Stoptober House that contributed to smoking cessation success, including restricted smoking opportunities, access to smoking cessation counselors, and peer support.
Conclusion
This pilot study suggests that the Stoptober House provides support that can help people quit smoking. Further research is needed to confirm these findings and determine the cost-effectiveness of this intervention in promoting long-term abstinence among specific groups of smokers.