Interactions
POI
RECRUITMENT, INTERACTION
Interaction models revealed some attenuation of effects with respect to baseline variables. Most consistently, there was evidence that age was a moderator for both primary outcomes at the 3-month interval and for prolonged abstinence at the 6-month interval. These analyses suggests that older participants were more likely to benefit from the intervention, as the interaction term had an OR of 1.03 (95% CoI = 1.00; 1.05, probability of interaction [POI] = 98.9%) for prolonged abstinence at 3 months, 1.02 (95% CoI = 1.00; 1.04, POI = 96.6%) for point prevalence at 3 months, and 1.02 (95% CoI = 1.00; 1.05, POI = 97.1%) for prolonged abstinence at 6 months.There was also evidence that the intervention was more effective amongst those who scored higher on the confidence item at baseline (being more confident about being able to quit). However, this was less consistent with the moderation effect only marked in point prevalence at 3 months (OR = 1.17, 95% CoI = 1.02; 1.34; POI = 98.7%) and prolonged abstinence at 5 months (OR = 1.13, 95% CoI = 0.98; 1.30, POI = 94.7%). Finally, evidence that men were less likely to benefit from the intervention was found with respect to point prevalence at 3- and 6 months, with the evidence weaker for the latter. The OR was 0.45 (95% CoI = 0.20; 1.04, POI = 96.8%) at 3 months and 0.53 (95% CoI = 0.22; 1.24, POI = 92.9%) at 6 months.We found no evidence of interactions between group allocation and recruitment method nor with access to the general or the surgery version of the intervention. However, these analyses were limited by small sample sizes.