Table 3

Predictors of quitting by ITC-4 Wave 2 among all baseline current smokers

	Entire sample			USA			Canada			UK			Australia
	n	% quit	OR	n	% quit	OR	n	% quit	OR	n	% quit	OR	n	% quit	OR
Statistically significant interactions exist between country and ever tried to quit within last year variable.
p<0.05 for odds ratios that are underlined.
Outcome expectancy: Based on smokers’ responses to the question: “How much do you think you would benefit from health and other gains if you were to quit smoking permanently in the next 6 months?” Coded: 1: “not at all”, 2: “slightly”, 3: “moderately”, 4: “very much”, and 5: “extremely”.
Self-efficacy: Based on smokers’ responses to the question: “If you decided to give up smoking completely in the next 6 months, how sure are you that you would succeed?” Coded: 1: “not at all sure”, 2: “slightly sure”, 3: “moderately sure”, 4: “very sure”, and 5: “extremely sure”.
Worries about health and QOL: Based on smokers’ responses to the following two questions: (1) “How worried are you, if at all, that smoking will lower your quality of life in the future?”; (2) “How worried are you, if at all, that smoking will damage your health in the future?” Both questions were coded: 1: not at all worried, 2: a little worried, 3: moderately worried, 4: very worried. Here we used the average for the two variables.
Favourable attitudes about smoking: Based on smokers’ responses to the following two questions: (1) “You enjoy smoking too much to give it up”; (2) Smoking is an important part of your life. Both questions were coded: 1: strongly disagree, 2: disagree, 3: neither agree or disagree, 4: agree, and 5: strongly agree. Here we used the average of the two variables.
Overall opinion of smoking: Based on smokers responses to the question of: “What is your overall opinion of smoking?”
Outcome expectancy is highly correlated with worries about health and QOL (Pearson’s correlation coefficient 0.51, p<0.01).
Country
USA	1253	8%	Ref
Canada	1575	11%	1.23
UK	1686	9%	1.25
Australia	1746	8%	0.91
Age at recruitment (years)
18–24	710	11%	Ref	146	14%	Ref	198	12%	Ref	111	9%	Ref	255	10%	Ref
25–39	1989	11%	0.88	346	10%	0.59	509	14%	1.15	502	12%	1.15	632	8%	0.76
40–54	2268	7%	0.70	468	6%	0.46	574	9%	0.86	606	7%	0.65	620	8%	0.86
55 and up	1293	8%	0.86	293	7%	0.56	294	8%	0.86	467	9%	1.06	239	6%	0.87
Sex
Female	3481	9%	Ref	730	8%	Ref	863	11%	Ref	954	10%	Ref	934	7%	Ref
Male	2779	8%	0.93	523	7%	1.01	712	10%	0.89	732	8%	0.69	812	8%	1.15
Highest level of education
Low	3462	8%	Ref	508	7%	Ref	700	9%	Ref	1097	9%	Ref	1157	7%	Ref
Moderate	1969	9%	0.87	567	8%	1.22	653	11%	0.86	386	6%	0.56	363	9%	1.15
High	829	12%	1.08	178	11%	1.27	222	14%	1.22	203	12%	1.03	226	11%	1.02
Income
Low	1870	8%	Ref	445	9%	Ref	445	8%	Ref	504	9%	Ref	476	5%	Ref
Moderate	2174	9%	1.02	447	6%	0.70	561	13%	1.44	577	7%	0.89	589	8%	1.33
High	1811	10%	1.15	287	9%	0.97	463	12%	1.20	484	11%	1.30	577	9%	1.38
No response	405	8%	1.14	74	8%	0.99	106	8%	0.99	121	9%	1.27	104	8%	1.64
Identified majority group
White/English only	5551	9%	Ref	995	7%	Ref	1404	11%	Ref	1615	9%	Ref	1537	8%	Ref
Non-white/non-English	709	9%	0.81	258	12%	1.15	171	8%	0.56	71	6%	0.53	209	6%	0.78
Intention to quit
No intention	1622	4%	Ref	313	4%	Ref	283	3%	Ref	597	4%	Ref	429	3%	Ref
Plan to quit beyond 6 months	2380	7%	1.89	505	6%	1.95	568	8%	2.27	604	7%	1.79	703	7%	2.14
Plan to quit within 6 months	1576	14%	3.38	296	10%	3.09	532	15%	3.73	345	15%	3.82	403	13%	3.77
Plan to quit within 1 month	682	18%	4.17	139	21%	7.52	192	18%	3.79	140	22%	5.69	211	12%	3.16
Tried to quit within last year
Yes	2645	11%	Ref	558	12%	Ref	731	14%	Ref	583	11%	Ref	773	9%	Ref
No	3615	7%	0.74	695	5%	0.59	844	8%	0.70	1103	8%	0.91	973	7%	0.80
Longest time off smoking
Never	1179	7%	Ref	247	4%	Ref	269	6%	Ref	367	7%	Ref	296	9%	Ref
1 week or less	1017	3%	0.38	212	3%	0.52	260	3%	0.48	257	4%	0.44	288	2%	0.21
Between 1 week and 6 months	1909	8%	0.85	365	7%	1.08	497	11%	1.19	495	7%	0.67	552	7%	0.63
6 months or more	2155	14%	1.57	429	14%	2.59	549	17%	2.18	567	15%	1.62	610	11%	0.85
Heaviness of smoking index
0	896	19%	Ref	178	20%	Ref	229	24%	Ref	213	15%	Ref	276	16%	Ref
1	682	12%	0.72	132	14%	0.78	159	14%	0.61	201	12%	0.79	190	8%	0.59
2	1040	8%	0.49	193	7%	0.42	287	7%	0.36	296	6%	0.42	264	10%	0.83
3	1793	7%	0.55	369	6%	0.41	405	8%	0.48	575	8%	0.77	444	6%	0.54
4	1072	7%	0.62	195	2%	0.15	309	9%	0.57	260	9%	1.12	308	6%	0.71
5	570	4%	0.42	126	2%	0.21	145	7%	0.53	109	6%	0.75	190	3%	0.29
6	207	4%	0.44	60	5%	0.50	41	5%	0.41	32	3%	0.36	74	3%	0.42
Baseline smoking frequency
Daily smoker	5740	8%	Ref	1143	7%	Ref	1444	9%	Ref	1576	8%	Ref	1577	7%	Ref
Weekly/monthly smoker	520	22%	1.56	110	23%	1.63	131	27%	2.07	110	17%	0.86	169	20%	1.81
Overall opinion of smoking
Positive or neutral	2758	7%	Ref	552	7%	Ref	587	9%	Ref	842	6%	Ref	777	6%	Ref
Negative	2235	10%	1.19	428	10%	1.14	626	11%	0.80	565	11%	1.82	616	9%	1.30
Very negative	1267	11%	1.24	273	8%	0.74	362	14%	0.85	279	14%	1.97	353	10%	1.60
Continuous variables
Outcome expectancy			0.90			0.85			1.05			0.90			0.81
Self-efficacy			1.06			0.94			0.95			1.17			1.22
Worries about health and QOL			1.02			0.94			1.10			0.84			1.23
Favourable attitudes about smoking			0.92			1.17			0.77			0.90			1.06
Total	6260	9%		1253	8%		1575	11%		1686	9%		1746	8%
Nagelkerke’s R²			0.14			0.22			0.18			0.18			0.14