Table 2

Predictors of quitting by ITC-4 Wave 2 among baseline current smokers who made serious quit attempts between Waves 1 and 2

	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 (1) heaviness of smoking index; (2) self-efficacy; and (3) favourable attitudes about smoking
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?”
Country
USA	454	22%	Ref
Canada	694	24%	3.62
UK	530	29%	0.65
Australia	596	23%	0.30
Age at recruitment (years)
18–24	345	23%	Ref	82	26%	Ref	101	23%	Ref	52	19%	Ref	110	24%	Ref
25–39	761	28%	1.09	123	27%	0.95	240	29%	1.37	169	34%	1.45	229	21%	0.76
40–54	733	23%	0.95	151	18%	0.84	232	23%	1.07	167	25%	0.78	183	26%	1.13
55 and up	435	23%	0.89	98	20%	0.77	121	19%	0.92	142	30%	0.97	74	19%	0.80
Sex
Female	1282	25%	Ref	267	23%	Ref	390	25%	Ref	319	30%	Ref	306	23%	Ref
Male	992	24%	0.90	187	21%	1.07	304	23%	0.88	211	27%	0.71	290	23%	1.05
Highest level of education
Low	1210	23%	Ref	186	19%	Ref	310	21%	Ref	337	30%	Ref	377	21%	Ref
Moderate	737	24%	0.94	200	24%	1.59	286	25%	0.94	119	21%	0.51	132	25%	1.04
High	327	31%	1.18	68	28%	1.32	98	33%	1.30	74	34%	0.98	87	28%	1.04
Income
Low	693	21%	Ref	180	22%	Ref	196	18%	Ref	159	28%	Ref	158	16%	Ref
Moderate	790	24%	1.17	162	18%	0.78	261	27%	1.66	164	26%	0.96	203	24%	1.57
High	669	28%	1.23	92	29%	1.37	198	28%	1.40	177	31%	1.17	202	27%	1.56
No response	122	27%	1.39	20	30%	1.33	39	21%	1.17	30	37%	1.57	33	24%	1.52
Identified majority group
White/English only	1978	25%	Ref	334	21%	Ref	613	25%	Ref	508	29%	Ref	523	24%	Ref
Non-white/non-English	296	21%	0.76	120	25%	1.39	81	17%	0.52	22	18%	0.63	73	18%	0.71
Intention to quit
No intention	232	26%	Ref	40	28%	Ref	52	17%	Ref	80	33%	Ref	60	23%	Ref
Plan to quit beyond 6 months	716	23%	1.04	168	18%	0.58	199	24%	1.64	162	26%	1.04	187	25%	1.50
Plan to quit within 6 months	817	26%	1.21	149	20%	0.73	285	28%	2.02	180	29%	1.13	203	25%	1.54
Plan to quit within 1 month	509	24%	1.08	97	30%	2.01	158	22%	1.27	108	29%	1.18	146	17%	0.89
Tried to quit within last year
Yes	1338	22%	Ref	285	23%	Ref	416	25%	Ref	270	23%	Ref	367	19%	Ref
No	936	28%	1.03	169	21%	0.65	278	24%	0.94	260	35%	1.33	229	30%	1.28
Longest time off smoking
Never	254	30%	Ref	41	22%	Ref	73	22%	Ref	72	35%	Ref	68	40%	Ref
1 week or less	331	10%	0.36	70	10%	0.30	101	9%	0.47	76	13%	0.46	84	7%	0.24
Between 1 week and 6 months	756	20%	0.78	146	16%	0.65	233	23%	1.10	167	20%	0.76	210	18%	0.66
6 months or more	933	32%	1.33	197	31%	1.57	287	32%	1.68	215	39%	1.63	234	28%	0.95
Heaviness of smoking index
0	431	39%	Ref	93	39%	Ref	120	45%	Ref	98	34%	Ref	120	37%	Ref
1	310	26%	0.71	67	28%	0.71	91	24%	0.48	79	30%	0.90	73	21%	0.53
2	399	20%	0.51	82	17%	0.38	127	17%	0.32	91	19%	0.57	99	27%	0.90
3	569	22%	0.64	109	20%	0.55	160	21%	0.51	164	29%	1.01	136	18%	0.60
4	343	22%	0.60	50	8%	0.14	128	21%	0.57	66	36%	1.74	99	19%	0.63
5	163	15%	0.41	33	9%	0.19	54	19%	0.53	25	24%	0.90	51	10%	0.24
6	59	14%	0.45	20	15%	0.54	14	14%	0.40	7	14%	0.46	18	11%	0.35
Baseline smoking frequency
Daily smoker	1995	22%	Ref	392	19%	Ref	620	22%	Ref	471	28%	Ref	512	20%	Ref
Weekly/monthly smoker	279	41%	1.41	62	40%	1.32	74	49%	2.00	59	32%	0.62	84	39%	1.81
Overall opinion of smoking
Positive or neutral	766	24%	Ref	154	25%	Ref	208	25%	Ref	206	25%	Ref	198	23%	Ref
Negative	883	26%	1.22	170	24%	1.08	287	24%	0.86	191	33%	2.15	235	24%	1.24
Very negative	625	23%	1.22	130	17%	0.68	199	25%	0.86	133	29%	1.99	163	21%	1.60
Continuous variables
Outcome expectancy			0.87			0.82			0.98			0.79			0.77
Self-efficacy			1.09			0.89			0.97			1.33			1.17
Worries about health and QOL			0.90			0.86			0.98			0.72			1.06
Favourable attitudes about smoking			1.05			1.27			0.78			1.12			1.32
Total	2274	25%		454	22%		694	24%		530	29%		596	23%
Nagelkerke’s R²			0.14			0.21			0.16			0.21			0.18