Logistic regression models predicting changes in quitting intentions and smoking behaviour
| ADPE models | PPE models | ADPE and PPE model | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Unadjusted models | Multivariable model | Multivariable model with two-way interaction | Unadjusted models | Multivariable model | Multivariable model with two-way interaction | Multivariable model | ||||||||
| OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | OR | (95% CI) | |
| Predicting intention change† | ||||||||||||||
| Plan to quit at Time 1‡ | ||||||||||||||
| No plans to quit | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | ||||||||
| Plans to quit | 0.81 | (0.26 to 2.55) | 0.61 | (0.18 to 2.02) | 0.70 | (0.20 to 2.46) | 0.43 | (0.12 to 1.56) | 0.98 | (0.26 to 3.68) | 0.43 | (0.12 to 1.58) | ||
| ADPE | 1.71** | (1.11 to 2.64) | 1.70** | (1.09 to 2.64) | 1.78** | (1.12 to 2.84) | 1.03 | (0.63 to 1.68) | ||||||
| Plans to quit×ADPE | 0.57 | (0.11 to 3.10) | ||||||||||||
| PPE | 2.44*** | (1.38 to 4.32) | 2.63*** | (1.42 to 4.87) | 3.15*** | (1.65 to 6.03) | 2.57*** | (1.35 to 4.89) | ||||||
| Plans to quit×PPE | 0.20* | (0.04 to 1.08) | ||||||||||||
| Predicting behaviour change§ | ||||||||||||||
| Plans to quit at Time 1¶ | ||||||||||||||
| No plans to quit | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 | ||||||||
| Plans to quit | 1.98 | (0.78 to 5.03) | 1.89 | (0.74 to 4.79) | 1.96 | (0.77 to 5.00) | 1.60 | (0.59 to 4.37) | 2.37* | (0.86 to 6.55) | 1.51 | (0.55 to 4.18) | ||
| ADPE | 1.10 | (0.81 to 1.51) | 1.06 | (0.77 to 1.44) | 1.07 | (0.77 to 1.49) | 0.70 | (0.45 to 1.07) | ||||||
| Plans to quit×ADPE | 0.85 | (0.32 to 2.29) | ||||||||||||
| PPE | 1.59** | (1.09 to 2.33) | 1.47** | (1.01 to 2.16) | 1.59** | (1.06 to 2.38) | 1.93*** | (1.18 to 3.16) | ||||||
| Plans to quit×PPE | 0.47 | (0.15 to 1.49) | ||||||||||||
All models adjusted for dependency within friendship pairs and robust SEs were used. All models controlled for the number of days since the tax increase and plain packaging announcement, and for which advertisement was viewed; and all models predicting behaviour change also adjusted for the number of days between the experimental session and the follow-up survey.
***p≤0.01, **p<0.05, *p<0.10.
†N=231. Except for the unadjusted models, all other models predicting intention change adjusted for daily cigarette consumption and conversation condition.
‡Of those who were not planning to quit at Time 1, 18.5% changed their intentions to quit. Of those who were planning to quit, 15.4% changed their intentions.
§N=208. Except for the unadjusted models, all other models predicting behaviour change adjusted for sex and age.
¶Of those who were not planning to quit at Time 1, 24.2% reported having made a change to their smoking behaviour. Of those who were planning to quit, 45.5% had changed their behaviour.
ADPE, ad-directed perceived effectiveness; PPE, personalised perceived effectiveness; PTQ, plans to quit.