OBJECTIVES: To examine the association between physical multimorbidity and 6-month quit outcomes among treatment-seeking smokers.

METHODS: We analysed data from 120 732 adults enrolled in Ontario's largest publicly funded smoking cessation programme. At enrolment, participants self-reported zero, one or two or more chronic physical health conditions. The primary outcome was 7-day point prevalence abstinence at 6 months. We used mixed-effects logistic regression to assess the association between multimorbidity and quit outcomes, adjusting for demographic and tobacco use characteristics.

RESULTS: Of participants, 39.4% reported no conditions, 26.8% reported one and 33.8% reported two or more. Those with multimorbidity were older, had lower socioeconomic status and showed higher tobacco dependence but also greater motivation to quit. Compared to individuals without comorbidities, those with one condition (OR = 0.94, 95% CI: 0.90-0.98) and those with two or more (OR = 0.81, 95% CI: 0.77-0.85) had lower odds of quitting. Mental health conditions further reduced quit success among those with physical multimorbidity.

DISCUSSION: Physical multimorbidity is associated with 19% lower odds of cessation success despite high motivation to quit. Tailored, intensive cessation support may improve outcomes for this high-risk group.