Table 1

Predictors of making serious quit attempts between International Tobacco Control Four Country Survey (ITC-4) Wave 1 and Wave 2

	Entire sample			USA			Canada			UK			Australia
	n	% attempted	OR	n	% attempted	OR	n	% attempted	OR	n	% attempted	OR	n	% attempted	OR
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).
OR, odds ratio; QOL, quality of life.
Country
USA	1253	36%	Ref
Canada	1575	44%	1.30
UK	1686	31%	1.01
Australia	1746	34%	0.88
Age at recruitment (years)
18–24	710	49%	Ref	146	56%	Ref	198	51%	Ref	111	47%	Ref	255	43%	Ref
25–39	1989	38%	0.69	346	36%	0.43	509	47%	0.86	502	34%	0.62	632	36%	0.82
40–54	2268	32%	0.64	468	32%	0.45	574	40%	0.76	606	28%	0.62	620	30%	0.68
55 and up	1293	34%	0.88	293	33%	0.59	294	41%	0.94	467	30%	0.96	239	31%	0.94
Sex
Female	3481	37%	Ref	730	37%	Ref	863	45%	Ref	954	33%	Ref	934	33%	Ref
Male	2779	36%	1.00	523	36%	1.02	712	43%	0.98	732	29%	0.79	812	36%	1.18
Highest level of education
Low	3462	35%	Ref	508	37%	Ref	700	44%	Ref	1097	31%	Ref	1157	33%	Ref
Moderate	1969	37%	0.89	567	35%	0.87	653	44%	0.81	386	31%	0.92	363	36%	1.02
High	829	39%	0.98	178	38%	1.04	222	44%	0.87	203	36%	1.04	226	38%	1.03
Income
Low	1870	37%	Ref	445	40%	Ref	445	44%	Ref	504	32%	Ref	476	33%	Ref
Moderate	2174	36%	0.88	447	36%	0.83	561	47%	0.91	577	28%	0.83	589	34%	0.94
High	1811	37%	0.86	287	32%	0.69	463	43%	0.79	484	37%	1.06	577	35%	0.91
No response	405	30%	0.77	74	27%	0.54	106	37%	0.67	121	25%	0.73	104	32%	1.18
Identified majority group
White/English only	5551	36%	Ref	995	34%	Ref	1404	44%	Ref	1615	31%	Ref	1537	34%	Ref
Non-white/non-English	709	42%	1.09	258	47%	1.27	171	47%	1.10	71	31%	0.84	209	35%	1.04
Intention to quit
No intention	1622	14%	Ref	313	13%	Ref	283	18%	Ref	597	13%	Ref	429	14%	Ref
Plan to quit beyond 6 months	2380	30%	1.85	505	33%	2.95	568	35%	1.81	604	27%	1.70	703	27%	1.41
Plan to quit within 6 months	1576	52%	3.76	296	50%	4.69	532	54%	3.25	345	52%	4.44	403	50%	3.18
Plan to quit within 1 month	682	75%	8.82	139	70%	9.04	192	82%	11.52	140	77%	11.46	211	69%	5.87
Tried to quit within last year
Yes	2645	51%	Ref	558	51%	Ref	731	57%	Ref	583	46%	Ref	773	47%	Ref
No	3615	26%	0.55	695	24%	0.57	844	33%	0.54	1103	24%	0.56	973	24%	0.50
Longest time off smoking
Never	1179	22%	Ref	247	17%	Ref	269	27%	Ref	367	20%	Ref	296	23%	Ref
1 week or less	1017	33%	0.90	212	33%	1.29	260	39%	0.90	257	30%	0.93	288	29%	0.67
Between 1 week and 6 months	1909	40%	1.14	365	40%	1.79	497	47%	1.09	495	34%	0.93	552	38%	1.01
6 months or more	2155	43%	1.45	429	46%	2.39	549	52%	1.70	567	38%	1.24	610	38%	1.01
Heaviness of smoking index
0	896	48%	Ref	178	52%	Ref	229	52%	Ref	213	46%	Ref	276	43%	Ref
1	682	45%	0.93	132	51%	0.91	159	57%	1.15	201	39%	0.77	190	38%	0.86
2	1040	38%	0.72	193	42%	0.76	287	44%	0.74	296	31%	0.60	264	38%	0.81
3	1793	32%	0.64	369	30%	0.50	405	40%	0.66	575	29%	0.57	444	31%	0.78
4	1072	32%	0.69	195	26%	0.45	309	41%	0.81	260	25%	0.59	308	32%	0.86
5	570	29%	0.68	126	26%	0.54	145	37%	0.77	109	23%	0.68	190	27%	0.72
6	207	29%	0.71	60	33%	0.86	41	34%	0.60	32	22%	0.65	74	24%	0.72
Baseline smoking frequency
Daily smoker	5740	35%	Ref	1143	34%	Ref	1444	43%	Ref	1576	30%	Ref	1577	32%	Ref
Weekly/monthly smoker	520	54%	1.43	110	56%	1.38	131	56%	1.34	110	54%	1.55	169	50%	1.44
Overall opinion of smoking
Positive or neutral	2758	28%	Ref	552	28%	Ref	587	35%	Ref	842	24%	Ref	777	25%	Ref
Negative	2235	40%	1.07	428	40%	1.22	626	46%	0.91	565	34%	1.06	616	38%	1.19
Very negative	1267	49%	1.24	273	48%	1.18	362	55%	1.12	279	48%	1.40	353	46%	1.34
Continuous variables
Outcome expectancy			1.04			0.94			1.08			1.06			1.04
Self-efficacy			0.99			1.02			0.94			0.92			1.08
Worries about health and QOL			1.15			1.10			1.13			1.13			1.28
Favourable attitudes about smoking			0.88			1.00			0.89			0.75			0.88
Total	6260	36%		1253	36%		1575	44%		1686	31%		1746	34%
Nagelkerke’s R²			0.27			0.29			0.25			0.29			0.26